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Limestone wetland mesocosm for recycling saline wastewater in Coastal Yucatan, Mexico

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Title:
Limestone wetland mesocosm for recycling saline wastewater in Coastal Yucatan, Mexico
Creator:
Nelson, Mark, 1947-
Place of Publication:
Gainesville FL
Publisher:
University of Florida
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Subjects / Keywords:
Cells ( jstor )
Constructed wetlands ( jstor )
Groundwater ( jstor )
Limestones ( jstor )
Phosphorus ( jstor )
Species ( jstor )
Wastewater ( jstor )
Water tables ( jstor )
Water treatment ( jstor )
Wetlands ( jstor )

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Rights Management:
Copyright Mark Nelson. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Resource Identifier:
2428287 ( ALEPH )
41092449 ( OCLC )

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LIMESTONE WETLAND MESOCOSM FOR RECYCLING SALINE
WASTEWATER IN COASTAL YUCATAN, MEXICO














By

MARK NELSON


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE
OF DOCTOR OF PHILOSOPHY


UNIVERSITY OF FLORIDA


1998





























Copyright 1998
On Construction Blueprints pp. 55-64
(Figures 3-1 to 3-10)

By

Mark Nelson














ACKNOWLEDGMENTS


I would like to thank my dissertation committee and especially its chair, Howard

T. Odum, who was an invaluable friend, critic, catalyst and inspiration for my work in

ecological engineering. I was fortunate to have a committee of gifted teachers and

scientists whose professional fields spanned the topics covered in the research. Mark

Brown, my co-chair, gave freely of his knowledge of emergy analysis, wetland ecology

and restoration. K.R. Reddy is a master of wetland biogeochemistry and generously made

his laboratory available. Daniel Spangler is a gifted theoretical and field hydrogeologist

who helped design much of the mangrove research. Clay Montague shared his expertise

in estuarine dynamics and ecological modeling. I owe a debt to all of them for their

support, guidance and patience.

The present study would not have been possible without the generous support of

the Planetary Coral Reef Foundation, Bonsall, CA and Akumal, Q.R., Mexico. The

wetland systems have been recipients of the hard work, intelligence and care of Abigail

Ailing, Gonzalo Arcila, John Allen, Mark van Thillo, Ingrid Datica and Klaus Eiberle,

who share the vision of coral reef protection and bringing appropriate new technology to

the tropical world.

I am indebted to Richard Smith, laboratory manager, and the Water Reclamation

Facility of the University of Florida for making possible most of the water quality

analyses. Yu Wang, manager of the Biogeochemistry Laboratory, Soil & Water Sciences,









conducted the limestone/phosphorus analyses, and Biol. Edgar F. Cabrera contributed his

extensive knowledge of the plants of the Yucatan.

The Center for Wetlands supported my work with a research assistantship

and by providing a stimulating environment of creative staff and students. The Centro

Ecologico Akumal (CEA) contributed the land for the research wetland units and

financially assisted in their construction costs. Charles Shaw, staff geologist for CEA,

greatly assisted by sharing his research on the hydrogeology of the region.

Finally, I would like to thank my colleagues in the Institute of Ecotechnics

for allowing me the time to pursue this research, and for all the camaraderie and

challenge during more than two decades of wonderful ecological work. "Friendship,

honor, discipline and beauty."














TABLE OF CONTENTS
page
ACKNOWLEDGMENTS........................................................................ ...11ii

LIST OF TABLES................................................................................. viii

LIST OF FIGU RES...................................... .................. ............... ...... .... xiv

A B STRA CT ......................................... .................................... ........ ... xxii

CHAPTER 1: INTRODUCTION.................................................................. 1

Scientific Questions in Ecological Engineering of Wastewater....................... 2
Wastewater Interface Ecosystems in the Tropics............................... 2
Wastewater Interactions in Landscapes with Soil
Substrate of Limestone................................................... 3
Salty Wastewater................................................................... 4.
Using Small-Scale Mesocosm Tests to Evaluate
Regional Potentials..................................................... ...4
Problems of Fitting Water Systems to the Landscape.................................. 5
Unique Characteristics of Tropical Coastal Development.................... 5
Eutrophication Impacts on Coral Reefs.......................................... 6
Issues of Human Health........................................................ ....7
Previous Studies.............................................................................. 8
Study Sites in Yucatan........................................................................ 10
Regional Study Area: Akumal Coastline....................................... 10
Growth and Development in the Yucatan...................................... 13
Sites of Mesocosm Tests........................................................ 19
Receiving Wetland............................................................. 19
C oncepts........................................... .......... ............................. .. 24
Aggregated Conceptual Model.................................................. 24
Diversity vs. Trophic Conditions in the Interface
Treatment System........................................................ 26
Ecological Succession in the Treatment Systems .............................27
Major Objectives of the Research........................................................ 28
Plan O f Study...................................... ................................. ....... 28
Sampling and Measurement..................................................... 29
Outline of the Research Report............................................................ 30
CHAPTER 2: METHODS...................................................................... 32
Treatment Systems......................................................................... 32


iv









page
Ecological Engineering Design................................................. 32
Procedures for Start-Up and Management.................................... 34
Seeding with Biota.............................................................. 34
Field Measurements............................................................... 35
B iodiversity............................................................. 35
Frequency..................................................................36
C over................................... ................................. .. 36
Importance value.........................................................36
Leaf area index............................................................ 36
Leaf holes................................... ........................... .... 37
Surface organic matter............................................... 37
Solar insolation........................................................ 37
Canopy closure........................................................... 38
Analytic Measurements.......................................................... 39
Total nitrogen and total phosphorus................................... 39
Biochemical oxygen demand (BOD).................................. 40
Chemical oxygen demand............................................... 40
Total suspended solids................................................... 40
Fecal coliform bacteria.................................................. 41
A lkalinity................................... ........................... .... 41
Salinity ................................................................ 41
Phosphorus Uptake by Limestone............................................... 41
Initial P content and uptake in wetlands............................... 41
Calcium/magnesium composition of
Yucatan limestone.............................................. 42
Experiments on phosphorus uptake by limestone................... 43
Water Budget of Wetland Systems............................................. 44
Economic Evaluation............................................................. 44
Emergy Evaluation............................................................... 45
Receiving Wetland............................................................. 46
B iodiversity...................................... ........................... ..... 46
Mangrove Soils................................................................ 46
H ydrogeology...................................................................... 49
Simulation model of water budgets...................................................... 49
Evaluating the Potential of Wastewater System for Coastal Zone................... 50
Emergy Evaluation............................................................. 50
Transformities.......................................................... 51
Economic Evaluation............................................................. 51
Regional Water Budget........................................................... 51
Regional Nutrient Budget........................................................ 51

CHAPTER 3: RESULTS...................................... ................................... 53

Treatment Mesocosms................................................................. 53









page
Design and Operation of the Wetland Units.................................. 53
Ecological Characteristics....................................................... 65
Patterns of biodiversity and dominance............................... 65
Comparison with natural ecosystems................................. 74
Dominance..................................................... 74
Shannon diversity index................................... 81
Plant cover............................................................. 81
Plant frequency........................................................... 88
Importance values........................................................ 93
Leaf area index..................................................... .... 100
Leaf holes.......................... ...................................... 100
Surface organic matter................................................. 110
Solar insolation....................... .................................. 112
Canopy closure.......................................................... 112
Chemical Characteristics and Uptake......................................... 117
Phosphorus.......................... .....................................117
N itrogen................................... ........................... .... 123
Biochemical oxygen demand.......................................... 128
Total suspended solids................................................. 128
Alkalinity................................................................ 137
Salinity.......................... ......................................... 137
Reduction in Coliform Bacteria................................................ 140
Phosphorus Uptake by Limestone.......................................... ..140
Ca/Mg analysis of limestone....................................... ...140
Initial and uptake phosphorus levels................ ............. 146
Experiments on limestone P uptake.............................. ...149
W ater Budget................................... ................................. 153
Economic Evaluation............................................................ 153
Emergy Evaluation............................................................... 157
Receiving Wetland Groundwater Mangroves....................................... 176
Biodiversity....................................................................... 176
M angrove Soils....................... ............... ..... ... .. .... .. .... .... ..... 176
N utrients.................................... ...................................... 180
Hydrogeology of Coastal Zone................................................. 189
Cross section................................... ................................. 189
Groundwater.......................... .................................. 189
Water quality in mangroves.................................................... 192
Total nitrogen.......................... ..................................192
Soluble reactive phosphorus............................... ......... 199
Chemical oxygen demand............................................. 199
Total suspended solids............... ............... ................... 199
Coliform bacteria....................................................... 203
Salinity ................................................................... 203
Simulation of Water in Treatment Units and Mangroves..........206


vi









pane
Regional Potential of Wastewater System............................................ 219
Definition of Coastal System.................................................. 219
Emergy Evaluation.............................................................. 219
Economic Evaluation.......................... ..................................229
W ater B udget................................................ .... .. .... .. .........230
N utrient Budget.................................................................. 234

CHAPTER 4: DISCUSSION..................................................................... 247

Contribution of Research to Science of Ecological Engineering.................. 247
Ecological Succession in the Limestone Wetland Units............................ 248
Comparisons of the Akumal Systems with other Treatment Approaches.........250
Comparisons with Temperate Latitude Interface Systems.......................... 254
Comparison of Emergy Indices of the Akumal Units............................... 256
Role of Limestone Substrate............................................................ 260
Seasonal Changes and Effect of the Dry Season..................................... 261
Treatment of Wastewater Containing Sea Salt....................................... 263
Simulation of Hydrological Extremes................................................. 264
Transpiration of Treatment Systems................................................ ..264
Maintaining Vegetative Biodiversity.................................................. 265
Impacts of Effluent Disposal on the Mangroves..................................... 266
Carrying Capacity for People Coastal Development Potential................... 267
Percent of Economy Required for Wastewater Processing......................... 268
Perspectives from Regional Simulation Model....................................... 269
Future Potentials of the Designed Treatment System................................ 276
Long-Term System Prospects........................................................... 277
Authorization Meeting in Mexico...................................................... 279
Questions for Research................................................................... 280
B iodiversity ............................. ....................... .. .... .. ... .... ... 280
Mangrove Change................................................................ 281
Useful Life of the Wetland System............................................ 281
Acceptability and Affordability by Local People........................... 281
Sum m ary................................... .................. .............................. 282

APPENDIX A WATER LEVEL DATA FOR AKUMAL................................... 284
APPENDIX B NOTES AND TABLES FOR WATER BUDGET
SIMULATION MODEL................................................................. 304
APPENDIX C COMPARISON WITH UNIVERSITY OF FLORIDA
SEWAGE TREATMENT FACILITY................................................. 314

R EFER EN C E S................................... .................. .............. ... .. ... ... .... ... 319

BIOGRAPHICAL SKETCH...................................................................... 330














TABLES
page
Table 2-1 Transformities values used in emergy evaluations in this study.................. 52

Table 3-1. Plant species in the treatment wetlands from surveys of May 1997,
December 1997 and July 1998. Total number of species as of May 1997:
68 species; as of December 1997:70 species, as of July 1998:66 species ................. 66

Table 3-2 Species list: mangrove wetland ecosystem, 8 December
1997. Species identified by Edgar Cabrera, Chetumal, Q.R................................. 78

Table 3-3 Species list of inland forest near Akumal, Q.R., 9 December
1997. Species identified by Edgar Cabrera, Chetumal, .Q.R................................ 79

Table 3-4 Shannon diversity indices for constructed wetland systems
based on May 1997, December 1997 and July 1998 surveys............................ ...82

Table 3-5. Comparison of Shannon diversity indices for constructed
wetlands vs. natural mangrove and tropical forest ecosystems of the
study area, based on December 1997 and July 1998 survey data........................... 83

Table 3-6. Relative cover in the wetland system cells, based on 0.25
sq m quadrant analysis, M ay 1997..................................................... ... ... 84

Table 3-7. Estimates of area coverage, including canopy, of dominant plants in
the wetland treatment cells, May 1997. Total area of each cell in system 1 is 25.3
square meters, and area of each cell in system 2 is 40.6 square meters............... 85

Table 3-8. Estimates of area coverage, including canopy, of dominant
plants in the wetland treatment cells, December 1997 and July 1998.
Total area of each cell in system 1 is 25.3 square meters, and area of
each cell in system 2 is 40.6 square meters.................................................. 86

Table 3-9. Frequency rankings of dominant plants in constructed
wetlands in May 1997, December 1997 and July 1998 transects............................ 89

Table 3-10. Importance value ranking of top eight species in each wetland treatment
cell, May 1997, December 1997 and July 1998 surveys. Values were computed by
adding relative species frequency and relative species cover and dividing by 2.
Maximum value is therefore 1.0, and total is 1.0 summing all species found









page
in the treatm ent cell........................................ .................... .. ..................... ... 94

Table 3-11 Measurements of leaf area index in the treatment cells of the
wetland systems, May 1997, December 1997 and July 1998. Values are
given with standard error of the mean......................................................... 101

Table 3-12 Leaf holes in the wetland treatment units, December 1997................... 106

Table 3-13 Leaf holes in the wetland treatment units, July 1998 data..................... 108

Table 3-14. Outside solar insolation levels and their reduction in the
constructed wetlands, 28 July 1998 between 1050 and 1145 AM.
Perimeter light levels are the measured insolation at locations 0.5 m inside
the wetland systems along their outside edges............................................... 113

Table 3-15. Light penetration and canopy closure in the wetland systems and
adjoining mangrove wetland, 29 July 1998. Data presented standard error
of the m ean ....................................... ... .................... ............... .... .... 115.

Table 3-16 Total phosphorus content of water samples from cenote
(groundwater well) near wetland treatment systems .................................... .. 120

Table 3-17 Total phosphorus in effluent from septic tank and discharge
effluent from wetland treatment systems and percent reduction of
phosphorus levels...................................... ........................ ....... ....121

Table 3-18. Total phosphorus content of water samples from the
treatm ent w etlands................................ ............... ............................... 122.

Table 3-19 Total nitrogen in effluent from septic tank and discharge effluent
from wetland treatment systems and percent reduction of nitrogen levels............... 126

Table 3-20 Total nitrogen content of water samples from cenote
(groundwater well) near wetland treatment systems......................................... 127

Table 3-21 Biochemical oxygen demand (BOD-5) in effluent from septic
tank and discharge effluent from wetland treatment systems and percent
reduction ............................................ ......... ..................................... 13 1

Table 3-22 Biochemical oxygen demand (BOD-5) content of water
samples from cenote (groundwater well) near wetland treatment systems............... 132

Table 3-23 Total suspended solids (TSS) concentrations and reduction in
septic tank and discharge water from the Akumal wetland treatment systems.......... 133









page
Table 3-24 Total suspended solids (TSS) concentrations in water samples
from cenote (groundwater well) near wetland treatment systems......................... 134

Table 3-25 Alkalinity in septic tanks, wetland systems and cenote........................ 138

Table 3-26 Salinity in septic tanks, wetland systems and cenote........................... 139

Table 3-27 Coliform bacteria concentrations in effluent from septic tank and
discharge effluent from wetland treatment systems and percent reduction. Data
is in units of most probable number of colonies per 100 ml (MPN/100 ml)............. 143

Table 3-28 Coliform bacteria concentrations in water samples from
cenote (groundwater well) near wetland treatment systems. Data is in units
of most probable number of colonies per 100 ml (MPN/100 ml)......................... 144

Table 3-29 Ca/Mg composition of Yucatan limestone as analyzed by inductive
coupled plasm a spectroscopy................................................................... 145

Table 3-30. Inorganic phosphorus content of limestone samples............................ 147

Table 3-31 Results from experiments on limestone uptake of phosphorus................ 150

Table 3-32. Daily water budget of wetland treatment systems, May 1997................ 154

Table 3-33. Daily water budget of wetland treatment systems, December 1997......... 155

Table 3-34 Purchased materials and services used in construction of wetland
systems, Akumal, Mexico. Costs are expressed in Mexican pesos(1996) and
converted to U.S. dollars at the rate of 7.8 peso/$, which was the exchange
rate in 1996 when systems were built.......................................................... 159

Table 3-35 Purchased materials and services used in construction of package
plant sewage treatment system, Akumal, Mexico. Costs are expressed in
Mexican pesos (1996) and converted to U.S. dollars at the rate of 7.8 peso/$,
which was the exchange rate in 1996 when systems were built........................... 160

Table 3-36 Emergy analysis of the constructed limestone sewage wetlands............. 162

Table 3-37 Emergy analysis of the package plant sewage treatment system............. 171

Table 3-38 Wet weight/dry weight of soils in mangrove receiving wetland,
D ecem ber 1997................................... ................................................ 177

Table 3-39 Bulk density of soils in mangrove receiving wetland, December 1997......178









page
Table 3-40 Organic matter content of soils in mangrove receiving wetland
estimated from loss on ignition and mean values of the five soil samples
from D ecem ber 1997............................................................................ 179

Table 3-41 Calcium and magnesium content of mangrove soil ash after combustion
for organic content. Results determined by inductive coupled plasma spectroscopy... 181

Table 3-42 Total Kejdahl nitrogen content of soils in mangrove receiving
wetland on 12 December 1997 before discharge of treated effluent...................... 185

Table 3-43 Total Kejdahl nitrogen content of soils in mangrove receiving
wetland before discharge (30 April 1998) and 2 months (3 July 1998),
3 months (3 August 1998) and 4 months (2 September 1998) after
discharge of treated effluent began 3 May 1998........................................... ..186

Table 3-44 Phosphorus content of soils in mangrove receiving wetland
on 12 December 1997 before discharge of treated effluent................................ 187

Table 3-45 Phosphorus content of soils in mangrove receiving wetland
before and after discharge began 3 May 1998............................................. ..188

Table 3-46 Total nitrogen in water of mangroves before and after discharge
of treated w astew ater............................................................................ 198

Table 3-47 Soluble reactive phosphorus (SRP) in water of mangroves
before and after discharge of treated wastewater.......................................... 200

Table 3-48 Chemical oxygen demand (COD) in water of mangrove receiving
wetland before and after discharge of treated wastewater ............................... ..201

Table 3-49 Total suspended solids (TSS) in water of mangroves
before and after discharge of treated wastewater............................................ 202

Table 3-50 Coliform bacteria in water of mangroves in 1998 after
discharge of treated effl uent.................................................................... 204

Table 3-51. Salinity in mangrove water in December 1997 before
discharge of sewage effluent................................... ................................. 205

Table 3-52 Salinity in mangroves in 1998. Discharge of treated
effl uent began M ay 1998...................................... .................................. 207

Table 3-53 Computer program in BASIC for simulation model of water
budget in treatm ent wetland nit.................... ................... .... .. .... .. .... ......... 210









page
Table 3-54 Spreadsheet for calculation of coefficients in water budget
simulation model of treatment units and mangroves........................................ 212

Table 3-55 Emergy evaluation table of one square kilometer of developed
coastline, Akumal, Mexico (see Figure 3-58).............................................. ..221

Table 3-56 Emergy indices for evaluating one square kilometer of
developed coastline, Akumal, M exico......................................................... 227

Table 3-57 Water budget of a square kilometer of coastline around
research site without use of wetland treatment systems.................................... 231

Table 3-58 Comparative additions to groundwater (GW) of nitrogen,
phosphorus, BOD (organic compounds) and fecal coliform in a 1-square-
kilometer area of study site with and without the use of wetland
treatm ent system s................................... .............................................. 235

Table 3-59 Phosphorus budget of a developed square kilometer of
coastline, Akumal, Mexico, with no sewage treatment and changes if
wetland system s are installed....................... .................... .. .... ... .. ... .... ....... 237

Table 3-60 Nitrogen budget of a developed square kilometer of
coastline, Akumal, Mexico, with no sewage treatment and changes if
wetland system s are installed................................... ................................. 240

Table 3-61 Organic compounds (BOD) budget of a developed square
kilometer of coastline, Akumal, Mexico, with no sewage treatment and
changes if wetland systems are installed...................................................... 243

Table 3-62 Coliform bacteria budget of a developed square kilometer of
coastline, Akumal, Mexico, with no sewage treatment and changes if
wetland system s are installed................................................................... 245

Table 4-1 Comparison of loading rates and removal efficiency of Akumal
treatment wetland units with average North American surface and subsurface
flow wetlands (Kadlec and Knight, 1996).................................................... 255

Table 4-2. Comparison of emergy indices for Akumal treatment units,
package plant at Akumal and the University of Florida wastewater
treatment system (compiled from data in Tables 3-36, 3-38 and Appendix)............257

Table 4-3 Program in BASIC for simulation model of interactions between
natural environment and human economy along the Yucatan coast..................... 273









page
Table B-I. Average monthly rainfall at Tulum, 20 km south of study site............... 308

Table B-2 Measured evaporation at Tulum, 20 km south of study site
along the Yucatan coast. Actual evapotranspiration is estimated at 900 mm
for the Yucatan. The last column is a calculation of evapotranspiration
based on the percentage of yearly evaporation that occurs in each month............... 309

Table B-3 Average monthly relative humidity, temperature, and air
vapor pressure calculated for the given temperature and relative humidity
for the Y ucatan coast................................ ............................................ 310

Table B-4 Average wind velocity, measured at Puerto Moreles, Mexico,
80 km north of study site............................. .......................................... 311

Table B-5 Estimates of monthly groundwater flow based on data from
Back (1985) and average monthly rainfall in the Yucatan.................................. 312

Table B-6 Net primary productivity in mangrove ecosystems.............................. 313

Table C-1. Emergy analysis of the University of Florida sewage
treatm ent facility................................... .............................................. 316














FIGURES
pEge
Figure 1-1 Map of eastern Yucatan Peninsula of Mexico showing coastal
area of study around Akumal, Quintana Roo, north of Tulum.............................. 11

Figure 1-2 Geological cross-section in study area showing flow and mixing
of fresh groundwater and seawater (Shaw, in press).......................................... 12

Figure 1-3 Map of study area a) shows collapse zones and areas of ancient
bays (larger black dots) b) shows areas of groundwater discharge along the
coast and sampling points. In both diagrams modem reef is indicated by
light dots offshore (Shaw, in press) ............................................................ 14

Figure 1-4 Salinity contours in Akumal during a period of no rain.
Contours are compressed on the highly porous and permeable limestone.
At the 20% contour, mixing of saltwater and freshwater below ground
surface makes the gradients steeper (Shaw, 1997).......................................... 15

Figure 1-5 Salinity contours in Akumal area after a heavy rain. Compared
to Figure 1-4, salinity gradient is displaced inland due to dilution by rain
and groundwater flow (Shaw, 1997)..................................................... ... .. 16

Figure 1-6 Map of study area showing groundwater flow in relation to
porous limestone rock (indicated by crosses) and coliform contours from
studies conducted in May-August 1997 (Shaw, in press).................................... 17

Figure 1-7 Aerial photograph of study area, Akumal, Quintana Roo,
M exico ............................................... .............................................. 20

Figure 1-8 Study area around Akumal, Mexico showing location of the wetland
systems at "A", enlarged in Figure 1-9. Contour lines in meters. (Shaw, in press).......21

Figure 1-9 Enlarged sketch of area "A" in Figure 1-8 showing location of wetland
treatment areas and mangrove where treated effluent was discharged.
Points labeled A to E are mangrove sampling stations....................................... 22

Figure 1-10 Systems diagram showing the wetland treatment unit within
the context of the coastal zone economy and ecology........................................ 25









pwge
Figure 2-1 Schematic of wetland treatment system showing flow from
houses to septic tanks to wetlands............................................................... 33

Figure 3-1 Construction blueprint: isometric view of the wetland treatment
system .............................................. .......... ....................................... 55

Figure 3-2 Construction blueprint: isometric view of piping in the wetland
system .................................................. ........................................... .. 56

Figure 3-3 Construction blueprint: center section view of the wetland
system ............................................... ............ .................................. 57

Figure 3-4 Construction blueprint: side section showing fill materials in
the w etland system ......................................... ..................................... .. 58

Figure 3-5 Construction blueprint: control box with dimensions of the
wetland treatm ent cells...................................... ................................... .. 59

Figure 3-6 Construction blueprint: treatment cell 1 header detail of the
w etlands.............................................. ................ ......... ...................... 60

Figure 3-7 Construction blueprint: treatment cell 2 header detail of the
w etlands..................................................... ........................................ 6 1

Figure 3-8 Construction blueprint: schematic showing drainfield detail
for large wetland system s...................................................................... 62

Figure 3-9 Construction blueprint: schematic showing drainfield detail for
sm all wetland system s......................................... ................................... 63

Figure 3-10 Construction blueprint: drainfield cross-section drawing of
w etland system ............................................ ................................. ...... .. 64

Figure 3-11 Species-area curves for each of the four wetland treatment
cells, M ay 1997 data............................................................................... 70

Figure 3-12 Species-area curves for each of the four wetland treatment
cells, Decem ber 1997 data........................................................................ 71

Figure 3-13 Species-area curves for each of the four wetland treatment
cells, July 1998 data............................................................................... 72

Figure 3-14 Species-area curves for the 50.6 m2 wetland unit (system 1)
and the 81.2 m2 wetland (system 2), May 1997. Transects counted 482









pAge
individuals in each system ....................................................................... 73

Figure 3-15 Species-area curves for the 50.6 m2 Yucatan wetland

(system 1) and the 81.2 m2 wetland (system 2), December 1997. Transects
counted 500 individuals in each system........................................................ 75

Figure 3-16 Species-area curves for the 50.6 m2 Yucatan wetland
(system 1) and the 81.2 m2 wetland (system 2), July 1998. Transects
counted 500 individuals in each system........................................................ 76
Figure 3-17 Comparison of species richness between treatment wetlands,
mangrove wetland and forest ecosystems, December 1997. Transects were
1000 individuals from each system .............................................................. 77

Figure 3-18 Comparison of species richness between mangrove, forest and
each treatment wetland. Transects counted 1000 individuals in mangrove
and forest, and 500 each in wetland systems 1 and 2......................................... 80

Figure 3-19 Plant species in rank sequence of importance value (IV) in
the four wetland treatment cells, May 1997 data. Importance value =
(frequency + cover)/2.......................... .................. .... .... ..... .... .. .... ... ...... .. 97.

Figure 3-20 Plant species in rank sequence of importance value (IV) in
the four wetland treatment cells, December 1997 data. Importance
value = (frequency + cover)/2................................................................ 98

Figure 3-21 Plant species in rank sequence of importance value (IV) in
the four wetland treatment cells, July 1998 data. Importance value =
(frequency + cover)/2......................................... ................................. .... 99

Figure 3-22 Photograph of wetland systems in Akumal shortly after
planting, August 1996. System 1 is in foreground and System 2 in
background, in front of edge of mangrove wetland.......................................... 102

Figure 3-23 Photograph of vegetation in wetland system 1, May 1997.................... 103

Figure 3-24 Photograph of vegetation in wetland system 1, December 1997............. 104

Figure 3-25 Photograph of vegetation in wetland system 1, July 1998..................... 105

Figure 3-26 Surface organic matter in the wetland treatment cells. Data
presented are those of initial mulching (August 1996) and surface organic
matter (July 1998) after 23 months of operation. Bars are standard errors............ 111









page
Figure 3-27 Photograph showing dense canopy cover intercepting solar
insolation, wetland system 2, July 1998...................................................... 114

Figure 3-28. An example of canopy-cover photograph using fish-eye lens,
July 1998............................................... .......................................... ... 116

Figure 3-29 Total phosphorus (TP) analyses of water samples from
wetland treatm ent system 1................................... .................................. 118

Figure 3-30 Total phosphorus (TP) analyses of water samples from
wetland treatm ent system 2................................................................... .. 119

Figure 3-31 Total nitrogen (TN) analyses of water samples from wetland
treatm ent system 1................................... ............... ............................. 124

Figure 3-32 Total nitrogen (TN) analyses of water samples from wetland
treatm ent system 2......................................... ................................... ... 125

Figure 3-33 Biochemical oxygen demand (BODs) in wetland system 1
w ater sam ples...................................... .................. ............................. 129

Figure 3-34 Biochemical oxygen demand (BOD5) in wetland system 2
w ater sam ples............................................ ......................................... 130

Figure 3-35 Total suspended solids (TSS) in water samples from wetland
system 1 ............................................... .......................................... ... 135

Figure 3-36 Total suspended solids (TSS) in water samples from wetland
system 2............................................... ........................................ ... 136

Figure 3-37 Fecal coliform bacteria in water samples from wetland
system 1. Data plotted on log scale, and units are most probable number
(MPN) of bacterial colonies per 100 ml...................................................... 141

Figure 3-38 Fecal coliform in water samples from wetland system 2.
Data plotted on log scale, and units are most probable number (MPN) of
bacterial colonies per 100 m l..................................................................142

Figure 3-39 Estimates of monthly flows of phosphorus during first year of
wetland treatment system operations (1997). Data from both wetland
system s are com bined................................ ...................... .... .. .... .. ... ..... .. 148

Figure 3-40 Graphs with results of experiments on limestone uptake of
phosphorus........................................... .................... ......................... 152










page
Figure 3-41 Diagram of emergy and money flows in wetland treatment
systems, Akumal, Mexico. Units of diagram are E15 sej/yr................................ 172

Figure 3-42 Diagram of emergy and money flows in the package plant
sewage treatment system, Akumal, Mexico. Units of diagram are
E l5 sej/yr............................................... ...................................... .... 180

Figure 3-43 Howard T. Odum inspecting root penetration and peat depth
in mangroves, Akumal, December 1997...................................................... 182

Figure 3-44 Thickness of mangrove peat in the receiving wetland around the outfall
pipe discharging effluent, December 1997. See Figures 1-9 for location of mangrove
discharge point in Akumal. Mangrove soil samples were collected 1,3, 5 and 10 m
from discharge point in N,S,E and W directions (Tables 3-43 and 3-45). Water
samples were collected at Im upstream (A), Im (B) 3m (C) and 6m (D)
downstream and 15m (E) SE of discharge point (see Figure 1-10)....................... 183

Figure 3-45 Systems diagram of the mangrove wetland receiving treated
effl uent.................................................. ........................................... 190

Figure 3-46 Potentiometric measurements of groundwater level in
mangroves, December, 1997. Piezometers were located at AB, and C.
Survey transit level was located at point D. Flowlines calculated from
data are approximately in easterly direction.................................................. 191

Figure 3-47 Chart recorder water levels in cenote near wetland systems,
27-28 M ay 1997................................... ............................................... 193

Figure 3-48 Chart recorder water levels at Yal-ku lagoon, showing tidal
record, 27-28 M ay 1997............................. ........................................... 194

Figure 3-49 Chart recorder water levels in mangrove receiving wetland,
9-14 D ecem ber 1997................................ ............................................. 195

Figure 3-50 Chart recorder water levels in cenote near wetland systems,
10-14 D ecem ber 1997............................................................ .... ... 196

Figure 3-51 Chart recorder water levels at Yal-ku lagoon, showing tidal
record, 10-14 December 1997.......................... ........................................ 197

Figure 3-52 Systems diagram for simulation model of water budgets of
treatment unit and receiving wetland showing difference equations..................... 208









page
Figure 3-53 Systems diagram showing steady state storage and pathway
flows for water budget simulation model of treatment units and mangroves............ 209

Figure 3-54 Computer simulation of the water budgets of treatment
units and m angroves................................ ............................................. 215

Figure 3-55 Simulation of water budget for wetland treatment unit and
mangroves with increase of wastewater loading (10 times higher).
Scale: sunlight 5000 Kcal/m2/day, biomass 20 kg/m2, water levels 1.5 m,
w ater inflow s Im /day............................................................................ 216

Figure 3-56 Simulation of water budget for wetland treatment unit and
mangroves with loss of groundwater inflow. Scale: sunlight 5000
Kcal/m2/day, biomass 20 kg/m2, water levels 1.5 m, water inflows
Im /day ......................................... .................. .................................. 2 17

Figure 3-57 Simulation of water budget for wetland treatment unit and
mangroves with hurricane event at year 5. Scale: sunlight 5000 Kcal/m2/day,
biomass 20 kg/m2, water levels 1.5 m, water inflows lm/day............................ 218

Figure 3-58 Map of Akumal, Mexico showing the 1-square-kilometer
coastal study area................................... ..............................................220

Figure 3-59 Systems diagram of the square kilometer coastal economy and
environment, labeled with emergy flows in El18 sej/yr from Table 3-57................ 226

Figure 3-60 Diagram of emergy and money flows in the 1-square-kilometer
coastal area, Akumal, Mexico. Units of diagram are expressed
in E18 sej (solar emergyjoules)/yr............................................................ 228

Figure 3-61 Diagram of water budget of one square kilometer of
developed coastline, Akumal, Mexico. Figures in parentheses show changes
in budget if all sewage is treated by constructed limestone wetlands.................. 233

Figure 3-62 Diagram of phosphorus budget of one square kilometer of
developed coastline, Akumal, Mexico. Figures in parentheses show changes
in budget if all sewage is treated by constructed limestone wetlands and
receiving w etlands................................ ............................................... 239

Figure 3-63 Diagram of nitrogen budget of one square kilometer of
developed coastline, Akumal, Mexico. Figures in parentheses show
changes in budget if all sewage is treated by constructed limestone
wetlands and receiving wetlands............................................................. 242









page
Figure 3-64 Diagram of organic matter (BOD) budget of one square
kilometer of developed coastline, Akumal, Mexico. Figures in parentheses
show changes in budget if all sewage is treated by constructed limestone
wetlands and receiving wetlands............................................................... 244

Figure 3-65 Diagram of coliform bacteria budget of one square kilometer
of developed coastline, Akumal, Mexico. Figures in parentheses show
changes in budget if all sewage is treated by constructed limestone
wetlands and receiving wetlands.............................................................. 246

Figure 4-1. Diagram showing annual emdollar contributions to the
constructed wetland system in Akumal, Mexico............................................. 258

Figure 4-2. Systems diagram and difference equations used for simulation
model of the interactions between the natural environment and the human
economy along the Yucatan coastline......................................................... 270

Figure 4-3. Systems diagram for Yucatan coastal model. Values shown
are steady-state storage and flows between components ............................... ..271

Figure 4-4 Computer simulation of the Yucatan coastal model. The
legend gives the full scale values of the ordinate for each quantity...................272

Figure 4-5 Simulation runs of the interaction of the environment and human
economy in the Yucatan. a/Impact of starting with nitrogen at ten times higher
value b/Impact of starting with coral at zero c/ Impact of starting with money
and assets at 1/10 value................................ .......................................... 275

Figure A-1 Water level record for cenote near wetland treatment unit,
27-28 M ay 1997................................... ............... ............................... 285.

Figure A-2 Water level record for cenote near wetland treatment unit,
28-29 M ay 1997................................... .................. ............................. 286

Figure A-3 Water level record for cenote near wetland treatment unit,
29-30 M ay 1997................................... ............................................... 287

Figure A-4 Water level record for cenote near wetland treatment unit,
30-31 M ay 1997................................... ............................................... 288

Figure A-5 Water level record of tidal heights at Yal-Ku Lagoon, 27-28 May 1997... 289.

Figure A-6 Water level record of tidal heights at Yal-Ku Lagoon,
13-16 D ecem ber 1997...................................................... ....................... 290









page
Figure A-7 Water level record of tidal heights at Yal-Ku Lagoon,
16-17 D ecem ber 1997.............................................. .. .... .. .... ... .. ... ... ....... 291

Figure A-8 Water level record of tidal heights at Yal-Ku Lagoon,
17-19 D ecem ber 1997................................ ........................................... 292

Figure A-9 Water level record of tidal heights at Yal-Ku Lagoon,
19-22 Decem ber 1997................................ ........................................... 293

Figure A-10 Water level record for cenote near wetland treatment unit,
10-14 D ecem ber 1997................................ ........................................... 294

Figure A-I 1 Water level record for cenote near wetland treatment unit,
14-17 Decem ber 1997................................ ........................................... 295

Figure A-12 Water level record for cenote near wetland treatment unit,
17-20 D ecem ber 1997................................ ........................................... 296

Figure A-1 3 Water level record for mangrove near wetland treatment unit,
9-14 Decem ber 1997............................................................................. 297

Figure A-14 Water level record for mangrove near wetland treatment unit,
14-17 Decem ber 1997...................................... ................................... .. 298

Figure A-15 Water level record for mangrove near wetland treatment unit,
17-20 D ecem ber 1997................................ ........................................... 299

Figure A-16 Water level record for mangrove near wetland treatment unit,
18-21 July 1997............................................ ................................... ... 300

Figure A-17 Water level record for mangrove near wetland treatment unit,
22-25 July 1997................................... .................. .............................. 301

Figure A-I 8 Water level record for mangrove near wetland treatment unit,.
25-28 July 1997................................... .................. .............................. 302

Figure A-19 Water level record of tidal heights at Yal-Ku Lagoon,
24 July- 1 August 1997................................ ......................................... 303














Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

LIMESTONE WETLAND MESOCOSM FOR RECYCLING SALINE
WASTEWATER IN COASTAL YUCATAN, MEXICO

By

Mark Nelson

December 1998


Chairman: Howard T. Odum
Major Department: Environmental Engineering Sciences


To understand wetland self-organization and to prevent pollution of groundwater

and coral reef on the calcareous east coast of Yucatan, Mexico, a wetland mesocosm

system was developed for treatment and recycle of saline, septic-tank wastewater. High

diversity wetland ecosystems were developed in two concrete-lined chambers, using

subsurface flow through limestone gravel, arranged in series with discharge to backbeach

mangroves.

Evapotranspiration in the wetlands averaged 35% of design influent during

summer months and 20% during winter months. Tall wetland vegetation developed with

66 plant species in 131 m2. Shannon diversity of vegetation was 5.01 (logarithm base 2),

far greater than that of the mangrove wetland (1.49), but less than the inland Yucatan

forest (5.35). Leaf area index increased over 13 months from 3.96 0.28 to 6.05 0.49.









In wastewater passing through the systems, biochemical oxygen demand was reduced

85%, suspended solids 40%, phosphorus 78% and nitrogen 75%. Coliform bacteria were

reduced 99.8+%. Limestone gravel in the treatment system removed 5.75 1.68 mg/kg

phosphorus per year. Nutrients in mangrove water and soil sediments increased 5-10%

from discharge of treated wastewater. Water budgets in treatment system and mangrove

were studied with simulation model.

On a per-capita basis, the wetland systems for 40 people cost approximately $160

per person to construct, vs. over $400 for alternative treatment technologies. Operation

and maintenance costs were 10% that of conventional treatment. Emergy in purchased

inputs for construction were less than 1/3 of free environmental inputs; empower density

was 2.5 E19 sej/ha/yr (one third that of conventional treatment).

The potential for economic development using the new treatment systems was

evaluated. Treatment systems would require 0.3% of the annual monetary flow (vs. 1.1%

for conventional sewage treatment) and 2.4% of total emergy while contributing 71,000

emdollars (the monetary equivalent of useful work contributed by nature and by humans).

The new systems conserve mangroves, reduce eutrophication, prevent pollution of

groundwater, protect marine resources, and contribute aesthetic values.

Research results indicate high biodiversity can be achieved in sewage treatment

wetlands, use of limestone gravel augments phosphorus uptake and such systems can be

integrated into the larger environmental setting.














CHAPTER 1
INTRODUCTION 1

A central question in ecological engineering is how to organize the hydrological

cycle of the human economy symbiotically with that of the supporting ecosystems and

geological substrate so as to maximize their joint performance. This dissertation reports

the development and evaluation of an ecologically engineered wastewater interface

between saline municipal wastewater and a tropical coastal zone with limestone substrate,

mangrove wetlands, tourist beaches and coral reefs. Potential for this wetland system was

evaluated by estimating its role in the water, nutrient, and emerge budgets of the

emerging coastal economy.

To achieve the performance observed in ecosystems in nature, an ecologically

engineered system may need to be coupled to the geological setting and cycles as

organized with groundwater. This project uses a human-assisted self-organization

and structure to innovate a union of wastewater treatment with the larger ecosystem

context.

Ecological engineering seeks a symbiotic mix of man-made and ecological self-

design that maximizes productive work of the entire system (including the human

economy and the larger-scale environmental system). Allowing this process to self-

organize may develop better adapted ecosystems that prevail because of their greater

empower (Odum, 1991). By such minimal human manipulation and management,









materials are recycled, efficiency is enhanced, costs are reduced, and ecological

processes contribute more.

An important application of ecological engineering is the design of interface

ecosystems to handle byproducts of the human economy and to maximize the

performance of both the human economy and natural ecosystems (Mitsch and Jorgensen,

1991).

Scientific Questions in Ecological Engineering of Wastewater


Treatment and release of wastewater from coastal development in Quintana Roo,

in the Yucatan Peninsula of Mexico, involve new scientific questions..

Wastewater Interface Ecosystems in the Tropics

Tropical coastlines have dry and wet season properties, frequent hurricanes and

high temperatures year-round. There has been increasing interest in using wetlands as

interface ecosystems for wastewater treatment since early studies demonstrated their

effectiveness at removal of nutrients and suspended solids. These included use of cypress

swamps in Florida (Odum et al., 1977; Ewel and Odum, 1984) and peatlands in northern

Michigan (Kadlec, 1979).

Constructed wetlands using surface-flow or subsurface flow emergent vegetation

or aquatic plant systems have gained increasing acceptance (Hammer, 1989; Mitsch and

Gosselink, 1993; Reed et al, 1995). Since such natural or constructed wetlands are often

limited by solar insolation and show increased rates of uptake in warmer climates, such

systems may be expected to operate even more efficiently in tropical regions. In addition,

wastewater interface ecosystems may benefit from the high species diversity found in

tropical regions since diversity at the biotic and metabolic level increases the efficiency









of ecosystems (Jorgensen and Mitsch, 1991). Plant diversity may benefit wastewater

treatment by providing I/ greater variety of root systems, allowing for greater penetration

of the limestone gravel and supporting a wider range of associated microorganisms;

2/differing metabolic needs (e.g. nutrient uptake) may lead to greater capacity for

absorbing wastewater constituents; 3/differing seasonal cycles of activity which may

increase plant productivity year-round; 4/ greater ability to utilize the full spectrum of

incident solar radiation by the inclusion of shade-tolerant as well as top canopy species

and 5/ differing "specialist" capabilities (e.g. C3 and C4 photosynthetic pathways, or

quantity of aerenchyma tissue in saturated conditions) allowing for greater system

response to changing environmental conditions such as light, heat, and nutrient levels.

Greater diversity also buffers against system failure should disease or herbivory decimate

selected plant species in the constructed wetland. There is evidence that allowing self-

organization to develop cooperative mechanisms enhances the ability of adapted

ecosystems to handle pollution and toxicity (Odum, 1991).

Wastewater Interactions in Landscapes with Soil Substrate of Limestone

Landscapes on limestone platforms offer special challenges and opportunities for

ecologically engineered wastewater treatment. Calcium carbonate, the predominant

mineral compound, has the ability to react with phosphorus and thus offers the potential

for enhanced nutrient retention. On the other hand, such karstic landscapes are

characterized frequently by relatively poor or shallow soil depth. In addition, the presence

of rock such as limestone, which is dissolved by water, at ground surface permits rapid

infiltration and lateral movement of wastewater (Bogli, 1980; Milanovic, 1981).









Studies in similar subtropical and tropical limestone coastlines (e.g. the Florida

Keys and Caribbean islands such as Jamaica) have indicated that they are especially

susceptible to eutrophication through flow of septic tank effluent through porous

calcareous strata since retention time does not allow for sufficient plant uptake or

microbial decomposition (Bright et al, 1981; Pastorok and Bilyard, 1985).

Salty Wastewater

Wastewater with appreciable salt content has only rarely been studied in sewage

treatment. It is an especially important vector in ecologically engineered wetland

treatment systems as salinity is frequently a controlling factor in determining the types of

organisms that will best self-organize such systems. In addition, salinity is important in

coastal regions as groundwater salinity varies depending on factors such as tidal

interchange, rainfall and evapotranspiration. Saltwater ecosystems such as estuaries,

mangrove and salt marsh are amongst the world's most productive (Day et al, 1989).

Previous work with mangroves (Sell, 1977) and with marine ponds receiving treated

sewage have demonstrated their treatment effectiveness and capacity to self-organize to

the input of eutrophic wastewater (Odum, 1985).

Using Small-Scale Mesocosm Tests to Evaluate Regional Potentials

The two small constructed wetlands (total area 130 m2) evaluated in this research

may be viewed as a mesocosm study of the impact of such interface ecosystems if more

widely applied to the coastal regions of karstic tropical countries. A growing body of

literature has demonstrated the applicability of such mesocosm studies to evaluate

processes and potentials at higher spatial and energetic levels (Beyers and Odum, 1993).

Frequently distinctive patterns of self-organization result from interface mesocosms









exposed to extreme forcing functions such as high nutrient and hydrological subsidies

(Odum, 1991) that can then be evaluated for scaling-up and application at regional levels.

Problems of Fitting Water Systems to the Landscape


Unique Characteristics of Tropical Coastal Development

Over half the world's population live along coasts and adjoining rivers, and the

rate of population increase in coastal areas exceeds those of inland regions (NRC, 1995).

Especially in tropical developing countries, such issues have gained increasing attention

due to recent accelerated growth of tourism and land development, exploitation of natural

resources and the vulnerability of marine ecosystems, such as coral reefs, and coastal

ecosystems, such as mangrove wetlands, to the effects of pollution and eutrophication

(U.N., 1995).

At present, lack of effective and affordable means of sewage disposal is

widespread through the tropical developing world. This leads to chronic disease through

human contact with polluted water and environmental damage to sensitive ecosystems.

Coastal tourist development has been pursued by some developing tropical countries as a

method of economic progress, utilizing their resources of warm climates, beautiful

beaches and eco-tourism if they have attractive marine or terrestrial ecosystems. All too

frequently, this tourist development exacerbates the problems of water contamination by

placing large demands on available freshwater, adding new permanent and transient

populations to an area, and converting land from natural ecosystems.

Tropical areas are frequently characterized by extremely high biological diversity.

The Yucatan, because of its tropical climate and isolation, has been able to sustain to date

some of the most widespread and undamaged stands of tropical forest. The coastline









around Akumal and this portion of the eastern Yucatan coast is an important breeding

ground for loggerhead and green sea turtles, which come ashore annually to lay their

eggs.

In areas like the eastern Yucatan, the environmental hazard is especially great

because of the highly permeable karstic geology and the presence of coral reefs offshore

that are particularly sensitive to eutrophication. It is critical to not only evaluate current

development, but to develop ecologically engineered solutions. The subsurface flow

constructed wetlands, constructed as part of the present research effort in Akumal, will be

evaluated as one strategy for sustaining water quality both for people and for

environmental preservation in tropical coastal regions.

Eutrophication Impacts on Coral Reefs

Economic development results in the release of nutrients in coastal waters causing

replacement of ecosystems such as coral reefs important to tourism. The impact of

nutrients in coastal regions is greater than that of deeper waters because of the interplay

between sediments and the water column, due to the strong vertical mixing by tidal

currents and wind in the shallow water depths (Nixon and Pilson, 1983). Thus coastal

regions are unlike deeper oceanic areas where deposited materials are "lost" to surface

ecosystems. Thus coral reef ecosystems and other mature ecosystems are dependent on

internal nutrient recycling for a large portion of their gross productivity (Laws, 1983),

new growth requiring added nutrients. Nitrogen is sometimes a limiting factor for coral

reefs (D'Elia and Wiebe, 1990), normally supplied by zooplankton captured by coral

polyps. Excessive nutrients displace mature ecosystems with low diversity growths.









Thus nutrient retention by the interface ecologically engineered wastewater wetland is an

important criterion for maintenance of optimal environmental health at the higher level.

A growing body of research indicates that coral reefs and other marine

ecosystems such as seagrass can be rapidly degraded due to pollution from inadequately

treated sewage. Seagrass ecosystems are normally mesotrophic and are vulnerable to

shading, disease, and excessive epiphytic growth in eutrophied waters (Pastorok and

Bilyard, 1985). Caribbean coral reefs, despite their high gross productivity, are adapted to

oligotrophic waters where they maintain themselves using high nutrient retention and

recycling. Corals are vulnerable to sewage pollution due to the following causes:

I/ stress; 2/ decrease of available light and dissolved oxygen due to higher rates of

sedimentation and enhanced growth of phytoplantkon and other microorganisms in the

water column; 3/ overgrowth and bio-erosion of corals by fleshy macro-algae and benthic

filter-feeding invertebrates that outcompete corals in high-nutrient waters; 4/ diseases

resulting from bacterial growth stimulated by mucus-production by eutrophied corals;

and 5/ direct chemical toxic effects (Hallock and Schlager, 1986; Pastorok and Bilyard,

1985; Lapointe and Clark, 1992; and Hughes, 1994).

Issues of Human Health

Contamination of water resources is one of the leading causes of disease in

tropical countries (U.N., 1995). Coastal areas with their shallower water tables are

especially vulnerable to groundwater pollution. Water pollution includes pathogens

carried by improperly treated sewage and potentially toxic chemicals. Pathogens include

disease-causing bacteria, protozoa, viruses and helminths. Chemical hazards include









heavy metals, organic chemicals, and nitrates in sufficient concentrations to cause illness

(Krishnan and Smith, 1987).

Previous Studies


Coral reef deterioration caused by eutrophication was studied in Kaneohe Bay,

Oahu, Hawaii, which received sewage effluent from a treatment plant. In parts of the bay,

coral loss stemmed from a buildup of organic matter, causing anaerobic conditions that

released hydrogen sulfide, overgrowth from the explosive growth of "green bubbly

algae" (Dictosphaeria cavernosa), sedimentation, and loss of light and competition by

filter-feeders in increasingly turbid waters (DiSalvo, 1969; Laws, 1983; Grigg and

Dollar; 1990). There was a proliferation of filter-feeders that bore into the corals. Benthic

organisms outcompete water column plankton and filter-feeders in oligotrophic waters,

but the reverse is true in nutrient-rich conditions (Laws, 1983).

Previous studies of subsurface flow wetlands for sewage treatment have

demonstrated their advantages in situations of small, on-site sewage loading in areas

where land is scarce, or in situations where avoidance of malodor and mosquito-breeding

are important (Kadlec and Knight, 1996). These are all the case in Akumal because of the

high visibility of the treatment site, the need to create a nuisance-free and aesthetically

attractive system, and the potential of a well-designed subsurface flow wetland of

providing an inexpensive but highly effective degree of sewage treatment. As is the case

in the U.S. and Europe where this approach is rapidly spreading, the advantages of

constructed wetlands are that, because they rely on more natural methods, they are less

expensive to build and operate than conventional sewage treatment plants

(Tchonbanoglous, 1991). Constructed wetlands also can produce a standard of treatment









equivalent to tertiary or advanced wastewater treatment. This is far better than a typical

"package plant" or municipal sewage plant that produces effluent at secondary sewage

standards quality, requires high capital investment and technical expertise and is energy-

intensive (Reed et al, 1995). Subsurface wetlands use little or no electricity and

technology and require little technical supervision once installed (Cooper, 1992, Steiner

and Freeman, 1989; Green and Upton, 1992; Steiner, 1992). However, there is little prior

research with these systems in tropical, karstic, coastal conditions.

Wetland systems have long hydraulic residence times and through a variety of

mechanisms (sedimentation, antibiotics, filtration, natural die-off etc.) have shown

promise in achieving large reductions in coliform bacteria without the use of disinfectants

like chlorine used in conventional sewage treatment (Reed et al., 1995). Chlorine has the

potential to form toxic byproducts, such as chloramine, when released into marine

environments (Berg, 1975). Bacteria can break down chlorinated hydrocarbons into

compounds that may be far more dangerous than the original ones (Gunnerson, 1988),

and sometimes de-chlorination has been required by regulatory agencies, further adding

to the expense of such approaches (Kott, 1975).

The dynamics of limestone in subsurface flow wetlands is also largely unknown.

Theory suggests that limestone should increase phosphorus retention since calcium and

magnesium are the primary agents of phosphorus fixation in alkaline conditions (Reddy,

1997). A previous study with subsurface flow wetlands in Canada examined the efficacy

of dolomite [CaMg (C03)2] substrate containing 55% CaCO3. The substrate was found to

be effective at removal of P in influent wastewater handling secondary wastewater, but

when primary wastewater with higher P levels were used, P retention capacity proved









inadequate, and P-retention capacity decreased by 77% over 45 months of operation

(Reddy, 1997).

Study Sites in the Yucatan


Regional Study Area: Akumal Coastline

The research site is the coastal region around Akumal, Quintana Roo, Mexico

(Figure 1-1), about 90 kilometers south of Cancun on the eastern coast of the Yucatan

Peninsula, and 10 km north of the town and Mayan ruins at Tulum. Like many tropical

coastlines, the eastern Yucatan is underlain by permeable limestone that, in a kilometer-

wide area adjacent to the coast, is believed to be the remains of Pleistocene coral reef

communities (Shaw, in press). The hydrogeology of the coastal region around our study

site in Mexico was studied during the 1960s and 1970s (Ward and Weidie, 1976; Ward et

al, 1985), and water budgets for the region were developed by Lesser (1976).

In the northern third of the Yucatan (which includes the study site at Akumal),

maximum elevation is about 40 m though most of the land surface is in a very flat plain

of rough, pitted terrain, caused by weathering of the very permeable limestone, which is

exposed over most of the surface. Because of the general absence of other sediments or

soil, no surface drainage system exists. Cenotes (sinkholes) are the main bodies of fresh

water, and almost all water movement is subsurface through the fractured limestone.

Shaw (in press) has described the area's geologic profile and how the modern

topographic features have been derived from their Pleistocene predecessors (Figure 1-2).

About one kilometer inland is an Upper Pleistocene (Sangamon) beach ridge, with a

maximum elevation of 8 m, which is segmented by triangular spits that extend up to 750

m towards the sea. Modem, sandy, rounded bays have been formed by Holocene flooding



















































Figure 1-1 Map of eastern Yucatan Peninsula of Mexico showing coastal area of study
around Akumal, Quintana Roo, north of Tulum.













Ancient beach


Younger limestone belt '


Lagoon
Mangrove
and Karst Zone


Core holes Brackish water exits
_.. Brackish water ,.. _


Older limestone


Freshwater


Sea water enters


Figure 1-2 Geological cross-section in study area showing flow and mixing of fresh
groundwater and seawater (Shaw, inpress)









of the Pleistocene ones. Behind the headlands several hundred meters is a mixing zone

where the mix of fresh and saltwater have led to dissolution of limestone, the collapse

creating lagoons such as Yal-Ku in Akumal (Figure 1-3). While this collapse has been

attributed solely to the CaCO3 solution kinetics in the mixing zone (Back et al, 1979),

this area is associated with mangrove wetlands and biological activity may have been at

least partly responsible for the limestone dissolution (Odum, pers. comm.).

Akumal, which attracts tourists for its beaches, diving and snorkeling, has

experienced growth, from dozens of permanent residents in 1970 to around 500 currently,

with yearly tourist stays in the tens of thousands of days. There is evidence, from water

quality monitoring done by the Centro Ecologico Akumal (CEA), that there is growing

pollution of the terrestrial and marine environments. Shaw (1997) has documented a

pollution plume in Akumal as high as 2000 coliform colonies/100 ml in groundwater.

The finding of pollution correlates with the movement of this water through reef rock of

high porosity and permeability (Figures 1-4, 1-5, 1-6).

This pollution poses dangers both for people, due to contamination of

groundwater supplies and recreational contact with improperly treated sewage, and for

natural ecosystems such as the coral reef system offshore. Pollution and beach

development also are of concern in the study area because the coastline around Akumal is

an important breeding ground for leatherback and green sea turtles, which come ashore

annually to lay their eggs.

Growth and Development in the Yucatan

The rapid growth of the Yucatan Peninsula as an international and Mexican

tourist destination followed the selection of the area by the national government because












YalKu'
Lagoon
Half Moon
Bay

Akumal Bay


Figure 1-3 Map of study area a) shows collapse zones and areas of ancient bays (larger
black dots) b) shows areas of groundwater discharge along the coast and sampling points.
In both diagrams modem reef is indicated by light dots offshore (Shaw, 1997)









































Figure 1-4 Salinity contours in Akumal during a period of no rain. Contours are
compressed on the highly porous and permeable limestone. At the 20% contour, mixing
of saltwater and freshwater below ground surface makes the gradients steeper (Shaw, 1997).











Salinity, % SW
May 16, 1995


storm surge


Yal Ku Lagoon


Figure 1-5 Salinity contours in Akumal area after a heavy rain. Compared to Figure 1-4,
salinity gradient is displaced inland due to dilution by rain and groundwater flow (Shaw,
1997)





































Figure 1-6 Map ofstudy area showing groundwater flow in relation to porous limestone
rock (indicated by crosses) and coliform contours from studies conducted in May-August
1997 (Shaw, 1997)









of its excellent beaches, beautiful off-shore coral reefs, and Mayan ruins. Cancun now

receives over two million visitors per year and Quintana Roo close to three million

annually. The entire population of the state of Quintana Roo was less than 25,000 in

1950, but grew to around 200,000 by 1980 (Edwards, 1986). Evidence from tourism

development in other countries indicates that intensity of negative environmental and

cultural impact are related to scale (Jenkins, 1982, Rodenburg, 1980).

The geology of the coastal area of the eastern Yucatan is one of extreme

topographic flatness, underlain with carbonate rocks, predominantly limestone, of

Tertiary age. The soil is generally shallow (0-20 cm deep), which, coupled with high

permeability of the limestone, results in rapid infiltration of rain and high lateral

movement. The result is a thin lens of groundwater (less than 70 m thick) overlying

deeper groundwater that is close to the salinity of ocean water (Hanshaw and Back,

1980).

The Yucatan region is freshwater limited despite the ample rainfall (around 1100

mm of annual rainfall) and humid climate, and strategies for effective water utilization

have characterized human settlement in the region since the time of the Mayan

civilization (Back, 1995). These water limitations result from the nature of its almost pure

limestone karstic geology without appreciable other sediments. When the limestone

dissolves, forming solution depressions, these channels are not filled, so retain high

permeability and porosity. This geology produces low hydraulic head, which results in

restricted freshwater aquifers since the freshwater/saltwater interface is quite close to the

ground surface near to the coast. The Yucatan also lacks rivers, except in its southern

portions, because with the nearly flat topography of a coastal plain, and absence of









sediments, infiltration of rain to the water table is extremely rapid (Espejel, 1987).

Seasonal variability of rainfall is considerable, which also limits freshwater availability.

The region's high permeability not only decreases the amount of freshwater available, but

also makes the water supply very vulnerable to contamination by sewage effluent,

agricultural runoff, and the products of litterfall decomposition from the inland forests.

The resulting pollution, exacerbated by tropical climate, which favors the growth of

disease bacteria, is widespread in the Yucatan (Back, 1995).

Sites of Mesocosm Tests

Two subsurface flow wetlands for sewage treatment were constructed off the

"main street" in Akumal to serve residences, offices and public toilets. These constructed

wetlands are located about 250 m inland from Akumal Bay, and in close proximity (5-50

m) to a natural mangrove wetland as can be seen in an aerial photo of Akumal (Figure 1-

7), a topographic map of the study area (Figure 1-8) and sketch of treatment wetland units

and mangrove areas of the study (Figure 1-9). Groundwater was encountered at less than

1 m below ground surface during construction in August 1996. There is a thin layer of

sandy soil (6-10 inches) below which limestone rock is encountered.

Receiving Wetland

The mangrove wetlands around Akumal are unusual in that most have a groundwater

connection to seawater rather than having surface tidal channels. But like all mangrove

ecosystems, their hydrologic and salinity environments are highly dependent on the

relative and shifting predominance of freshwater and seawater that they receive.

Productivity in mangroves typically increases as one moves from mangrove areas
















24'*** ..


-U
~


= -


Figure 1-7 Aerial photograph of study area, Akumal, Quintana Roo, Mexico.


- *n M~ i


k ? '- 1 X-
& ^i4







--6
7


"L .I ... ;./ .""-. .....H. .... .." \ --.*








VScale



systems at "A", enlarged in Figure 1-9. Contour lines in meters. (Shaw, in press).
I,, Ullalf Moon Bay A



/ /0 100 200meters
Scale
Caribbean Sea Contour Interval- meter

Figure 1-8 Study area around Akumal, Mexico showing location of the wetland
systems at "A", enlarged in Figure 1-9. Contour lines in meters. (Shaw, in press.).










zN


Edge of
Mangrove


Ccnotec


Discharge point
N


Wetland System I


mangrove


Mangrove


Wetland System 2


10m


Sampling points A,B,C, D and E



Figure 1-9 Enlarged sketch of area "A" in Figure 1-8 showing location of wetland
treatment areasmangrove where treated effluent was discharged. Points labeled
A to E are mangrove sampling stations.









dominated by low-nutrient and high salinity seawater to ones enriched by freshwater

nutrient inputs and with decreased salinity (Day et al., 1989).

Mangroves have been shown to be effective in treating secondary wastewater. Sell

(1977) studied two South Florida tidal mangrove ecosystems enriched by effluent from a

sewage treatment plant. Mangrove growth was enhanced and there were no significant

differences in species composition, seedling survival or litterfall between mangroves

areas receiving enriched nutrient waters and control mangrove ecosystems.

Soils in the Akumal region are characterized by low nutrient status. Noguez-Galvez

(1991) studied nutrient levels near Carillo Puerto (19deg 16'N., 88 deg. 07' W) about 50

km inland from the coast and 75 km south of Akumal after differing ages of fallow

following slash-and-bum shifting agricultural use. Total N in the 0-5 cm layer was 0.437

0.022% at 1 year fallow rising to 0.619 0.095% after 20 years fallow. In the 6-11cm

layer, the total nitrogen data were 0.316% 0.044% after 1 year, and 0.478 0.076%

after 20 years. Phosphate levels were 12.16 1.75 mg/kg after 1 year in the 0-5 cm level,

rising to 16.72 4.61 mg/kg after 10 yrs, and 6.35 2.35 mg/kg in the 6-11 cm level after

1 year, and 11.33 7.7 mg/kg after 10 years of fallow.

At Puerto Moreles, Mexico, about 70 km north of the study site, Feller (1998)

found autochtonous mangroves without external source of sediment, creating a highly

organic peat substrate in the saturated subsurface. These soils are classified as solonchaks

and histosols in view of their high organic content and salinity (McKee, 1998). The

overall environment is oligotrophic and dominated by calcium carbonate limestone.

Human impacts include road-making, clearing, diking, filling, and garbage dumping

associated with tourist development. Road impoundments have not severed hydrological









connections since drainage is predominantly through groundwater connection with both

fresh and saltwater. Trejo-Torres et al (1993) found that Yucatan coastal mangroves

export freshwater during the rainy season and receive considerable seawater during drier

periods. In Belize, south of the study site, mangroves were primarily phosphorus limited,

and fertilization with phosphorus or a combination of nitrogen, phosphorus and

potassium (but not with nitrogen alone) produced sizeable increase of growth in

mangrove species (Feller, 1995).

Mangroves were found in five zones along the Yucatan coast depending on

distance from the coast. Highest biomass and basal areas were found in the mangrove

zone closest to the coast (Feller, 1998), which is the zone receiving the experimental

discharge of treated sewage effluent at Akumal.

Concepts


Aggregated Conceptual Model

Figure 1-10 is an aggregated systems diagram of the treatment unit within the

context of the coastal economy and environment. The sources of natural energy include

sun, wind, rain, inland groundwater flow, and wave and tidal activity of the sea.

Primary producing ecosystems are the inland forest, the mixed wetlands shaped by both

freshwater and saltwater near the coast, and the marine ecosystems (seagrass, coral reef

etc.). The human economy is supported by these natural ecosystems, local resources

(limestone, forest products), and imported goods and services. Tourism is the principal

source of monetary flow in the area; it pays for goods and services. The treatment

wetland units make an interface between the wastewater produced by the human






















upland forest / I idd \ \


\/ \f, salt \ nutri nt
\ -^ ^\ H20> \ 1 -- H20
-treatment
mixed units
/ wetlands


Akumal coastal zone
Quintana Roo, Mexico



Figure 1-10 Systems diagram showing the wetland treatment unit within the context of the
coastal zone economy and ecology.









economy before discharging treated water and nutrients to be recycled back into the

mixed wetlands.

Diversity vs. Trophic Conditions in the Interface Treatment System

These ecologically engineered systems provided an opportunity to investigate issues

of diversity vs. trophic state. Constructed wetlands have generally failed to maintain high

species numbers and diversity. This failure has been attributed to high nutrient waters

favoring the growth of species (such as Typha spp. or Phragmites spp.) that out-compete

other, less aggressive species. In the United States and Europe, many constructed

wetlands have not attempted to provide ecosystem attributes. They were designed as

monocultures or planted with only 2-3 species, but have nevertheless provided

satisfactory water treatment (Reed et al, 1995).

The relationship between nutrient status and species diversity is far from well

understood. Yount (1956 cited in Odum, 1996) correlated pulses of nutrient enrichment

with increased dominance, variation, competitive exclusion and loss or masking of rarer

species. However, natural conditions of steady-state, high eutrophication have also

promoted high diversity as contrasted to sudden conditions of eutrophication caused by

anthropogenic pollution (Odum, 1996). Some types of human disturbance (e.g. fire,

grazing and cutting in Mediterranean-climate Israel) enhance numbers of species

(Naveh and Whittaker, 1979 cited in Mooney, 1986).

Similarly, while the prevalent tendency is to regard high species diversification as

a sign of ecosystem development toward maturity (Margalef, 1968), there are other

circumstances in which high initial nutrient levels and species numbers are reduced as









storage are consumed (Odum, 1968), leading to suggestions that maximum species

numbers may be maintained at intermediate successional stages (E.P. Odum, 1993).

Ecological Succession in the Treatment System

The research presented an opportunity to study ecological succession in the

wetland mesocosms and to investigate some of the theoretical relationships posited for

such self-organization.

Odum (1994) noted that succession is the process by which structure and

processes are developed by ecosystems from available energies and resources. These

progressions often include system adaptation to physiological challenges, the building of

storage, development of diversity and interchange with the larger, external

environmental setting.

Ecological succession typically includes a period of rapid initial growth

dominated by aggressive, short-lived, pioneer species, giving way over time to species

with high biomass and gross productivity but less net production.

Among the characteristic patterns observed after system biomass and non-living

organic matter have been increased and as primary succession gives way to a more

mature, or equilibrium, stage are a greater balance between primary productivity and

respiration. As succession proceeds, the more mature ecosystem tends to display greater

internal cycling and retention of nutrients, increased specialization and mutualism, and

increase of efficiency of use of input energy (E.P. Odum, 1971).

The Akumal research offered an opportunity to track ecological succession and

self-organization from an initial state of virtually lifeless quarried limestone gravel and to









track ecosystem changes that resulted from the input of domestic wastewater to an initial

planting of wetland species.

Major Objectives of the Research


The major objectives of the present research were to develop a new, ecologically

engineered wastewater treatment system and to evaluate its effectiveness and integration

into the Yucatan coastal environment and human economy. Among the new elements

under investigation were the efficacy of utilizing limestone gravel as the primary

substrate for the constructed wetland, the ability of constructed wetlands with high-

nutrient inputs to sustain a high level of biodiversity and devising an integration with the

natural mangrove wetlands. In addition, evaluating whether the new treatment system

was economically cost-effective compared to other approaches and whether its use of

local resources (evaluated through emergy comparisons with other alternatives) would

make it more sustainable for a tropical developing country than conventional sewage

treatment options. Finally, if applied on a regional scale, to what extent would such a

system retain the anthropogenically-produced nutrients which pollute groundwater and

threaten the health of off-shore ecosystems such as coral reef?

Plan of Study


1. Two pilot sewage treatment systems were constructed using saline influent wastewater,

limestone gravel and multiple seeding of species on the eastern coast of the Yucatan.

2. The living ecosystem was evaluated as it developed tracking species, diversity indices,

percent cover, leaf area index, and transpiration estimated indirectly.









3. The water and nutrient budgets were evaluated by analysis of inflow waters and

outflow waters, and a budget and simulation model that represents the seasonal cycle and

role of the ecosystem were developed.

4. After defining a representative square kilometer of coastal zone including tourist

developments and their wastewater flows, the coastal water budget was evaluated. The

role the new wastewater systems can have in the coastal water budget if expanded to

service a kilometer of coastline was examined.

5. The share of the system contributed by the environment and the economy was

evaluated using emergy, transformity, empower and empower densities of the principal

features of the wastewater unit and the main parts of the coastal area (hotels, people,

substrate limestone, dollar circulation and exchange).

Sampling and Measurement

Periodic sampling of water quality was conducted for the septic tanks, wetland

treatment compartments, groundwater and mangrove receiving wetland. Analysis was

done in local Mexican laboratories (Alquimia, Cancun and Centro Ecologico Akumal) for

parameters such as coliform bacteria and biochemical oxygen demand (BODs), which

require immediate testing. Other parameters, such as phosphorus, nitrogen, suspended

solids, and alkalinity, were tested in laboratories at the Water Reclamation Facility,

University of Florida, Gainesville by Richard Smith, the laboratory manager.

Bulk density and water-holding capacity for soils from the mangrove receiving

wetland were conducted in the laboratory of the Centro Ecologico Akumal. Soil samples

from the mangrove receiving wetland were analyzed for organic matter content and

phosphorus and nitrogen content at the at the Institute of Food and Agricultural Sciences









(IFAS) Soil Testing Laboratory, Gainesville. Analysis for mineral composition of the soil

was conducted using X-ray diffraction techniques by Dr. Willie Harris at the Pedology

Laboratory of the University of Florida, Gainesville.

Field measurements for ecological characteristics such as species number, cover

and frequency were conducted during research visits to the study site. Identification of

species were made with Edgar F. Cabrera, a biologist from Chetumal, Quintana Roo.

Limestone from the system was collected before treatment began and after 11

months of system operation. Analysis of the limestone for elemental composition was

done at the IFAS Soils Laboratory, with the help of Dr. James Bartos. Analysis of

limestone gravel for phosphorus was done at the University of Florida Wetland

Biogeochemistry Laboratory with the help of its manager, Ms. Yu Wang. Experiments

on limestone uptake of phosphorus were conducted at the same laboratory.

Outline of the Research Report


The research was reported in the following manner. Chapter 2 gives the

methodology followed in all the components of the research. Chapter 3 presents results

from the following areas

a/ Ecological characterization of the limestone wetland ecosystem, including

species number, biodiversity, frequency, cover, leaf area index, leaf holes, interception of

sunlight, canopy closure and surface organic matter.

b/ Wastewater treatment including total phosphorus, total nitrogen, biochemical

oxygen demand, total suspended solids, salinity, alkalinity and uptake of phosphorus by

limestone gravel, and water budget.









c/ Economic and emergy evaluation of the wetland treatment system and in

comparison with an alternative conventional treatment approach.

d/ Impact on the mangrove wetland including characterization of the hydrology

and soil sediments of the ecosystem; and nutrient status of the soils and water before and

after discharge of treated wastewater effluent from the limestone wetland unit.

d/ Simulation of the water budget of wetland treatment system and mangrove.

e/ Regional evaluation of application of the treatment wetlands. This was done by

first assessing the emergy and monetary flows in a square kilometer of developed

coastline, then evaluating the impact on this larger system's water and nutrient budgets

with and without the use of the wetland treatment systems.

Chapter 4 presents a discussion of the major findings of the present study, and

commentary on important vectors in the new wetland system for treating domestic

wastewater along the Yucatan coast. Observations are presented on the pattern of

ecological succession, the role of limestone, and a simulation model is developed for the

interaction of the environment and the tourist economy of the area. Finally, potential for

future application of the system in the region is discussed and remaining questions for

future research are listed.

Appendix A contains water levels measured for the tide at Akumal, in the

mangrove and in nearby cenote (groundwater well). Appendix B presents literature data

used in the model. Appendix C contains the emergy evaluation of the University of

Florida sewage treatment facility that is used for comparison to the limestone wetland

system.














CHAPTER 2
METHODS


Treatment Systems


Ecological Engineering Design


A constructed wetland for sewage treatment was developed meshing with the

environmental/geological context of the Akumal coastline. Following the concept of

ecological engineering, maximizing the work of natural elements, minimizing the use of

machinery and reducing cost. A system of contained wetlands was used to treat septic

tank discharge using gravity-flow, eliminating the need for electrical pumps (Figure 2-1).

Because of the thin soil layer, high porosity of underlying limestone and high

water table of the coastal settlements, an impermeable concrete liner prevented discharge

of wastewater before adequate treatment could be accomplished. A two-celled system

was used so that there was capacity to absorb torrential rains.

Limestone gravel with 1/4 3/8 inch diameter was used in the system. The

advantage of using smaller size gravel is that surface area and porosity is increased.

However, the trade-off is that smaller limestone gravel may undergo greater danger of

compaction and dissolution over time (Steiner and Freeman, 1989). Larger limestone

rock (2-4 inch diameter) was used in the first and last meter of each treatment cell to

minimize the danger of clogging near inlet and collector pipes.














-* -


Kitchen


Soil


Figure 2-1 Schematic of wetland treatment system showing flow from houses to septic
tanks to wetlands.


Constructed Subsurface

Wetland System









Outflows from the treatment wetlands were discharged into natural groundwater

mangrove wetlands where there was natural filtering capacity of rich, organic soils and

root uptake.

The treatment wetland systems were built with financing and support from

Planetary Coral Reef Foundation and the Centro Ecologico Akumal. Local Mayan

contractors and laborers did the construction work. Local sources of limestone

and sand were used. Public meetings in Akumal explained the planned research and

provided updates on research findings to government, business and local residents.

Procedures for Start-up and Management

An initial layer of sawdust mulch was applied to the system over the limestone,

establishing an aerobic layer for plants that could be sustained later by leaf litter drop.

Maintenance guidelines called for minimal interference without pruning

vegetation or eliminating species. Disease or pest pulses would be allowed, since these

form a part of nature's diversity mechanisms. Monitoring allowed tracking of natural

self-organization of introduced and volunteer plant species.

Seeding with Biota

The wetlands were planted with a wide variety of wetland plants, some

transplanted from local wetland areas, some from local commercial plant nurseries,

others from the botanical garden at Puerto Moreles and local gardens in Akumal. Some

species entered the system as seeds carried in by wind or animals from nearby wetlands,

as seeds or seedlings in the soil of plants transplanted from the wild, or during the

construction process.









There was no attempt to limit species. None were removed manually as unwanted

('weeds"). Trees and large palm species were planted at least 2 m away from the system

piping to minimize maintenance problems with roots. Multiple rounds of seeding were

arranged following experience with promoting self-organization in mesocosms (Beyers

and Odum, 1993).

Field Measurements

Biodiversity

Plant species richness was determined by identification of plant species in the

wetlands with the assistance of Edgar Cabrera, Chetumal, Q.R., a botanist from the

region. Transects of approximately 250 observations were conducted in each of the two

treatment cells of the two wetland systems, giving a total of about 1000 observations.

These observations were made in May 1997, December 1997 and July 1998.

Comparisons with biodiversity of natural ecosystems in the region (mangrove and

tropical inland forest) were done by conducting transects with 1000 individual plants,

identifying each to species in December 1997.

Biodiversity was calculated using the Shannon diversity index (Shannon and

Weaver, 1949; Brower et al, 1991):

H' = -1 p, log Pi

where p, = ni/N

"pi" is the proportion of species 'T' in the total number of individuals in the population

(N). The Shannon biodiversity index was calculated using the above formulas for log 2

and log 10.









Frequency

Frequency is a measure of the probability of finding an individual species with the

overall population sample (Brower et al, 1991). Plant species' frequency in the wetlands

was determined by analysis of the transects. Each individual plant stem was counted as

an observation in the transect. Data was tabulated for each treatment cell and cumulative

data were tabulated for each wetland system, and data for the combined two wetland

systems were analyzed.

Cover

Plant cover for each species was determined by 1/ use of 0.25 m2 quadrats in each

treatment cell and estimating percent cover of each species present, as well as percent of

bare ground; 2/ measuring canopy cover of the most prevalent species (15-20) in each

treatment cell (May 1997) and 3/estimating canopy coverage of all wetland species in

each treatment cell (December 1997 and July 1998).

Importance values

Importance values (IV) were calculated combining frequency and cover data and

dividing by two, so that the sum of all IV values for each system equaled one. These

calculations were made using the May 1997, December 1997 and July 1998 field data.

The graph of these data, called a dominance-density curve or species importance curve,

was plotted on a log/arithmetic scale against rank order (Brower et al, 1991).

Leaf area index

Leaf area index was determined by the point-intercept method. Approximately 50

measurements were made in each treatment cell of the wetland systems in May, 1997,









December 1997 and July 1998. Using a tall piece of steel rebar moved a set distance

along pre-assigned transect lines, the number of leaves touching the pole were recorded.

Each treatment cell had approximately 50 observations at each round of study.

Leaf holes

Holes in leaves due to herbivory, decomposition and other causes were measured

in December 1997 and July 1998 by estimating percent leaf damage and loss on 5

randomly selected leaves of each of the species present in the wetland. Then these data

were multiplied by the relative frequency of each species to give an overall measure of

leaf holes in the wetland systems.

Surface organic matter

Surface organic matter was determined by collecting surface litter from four 0.1

m2 quadrats within each cell of the two wetland systems in July 1998. Four samples of

the original woodchip/sawdust mulch from 0.1 m2 quadrats from a similarly constructed

wetland system in Akumal were collected to provide a measure of the starting surface

organic matter of the wetlands. The surface litter was dried at 70C and weighed, then

combusted at 4500C in a muffle furnace of the Water Reclamation Laboratory

of the University of Florida and reweighed. Organic matter content of samples was

determined as the difference between starting and final weights.

Solar insolation

Solar insolation and light interception in the wetland systems was measured

using a LI-COR LI-1 89 Quantum/Radiometer/Photometer equipped with a LI-COR

Terrestrial Radiation Sensor, Type SA (LI-200SA) pyranometer sensor. The pyranometer









was factory calibrated against an Eppley Precision Spectral Pyranometer under natural

daylight conditions, giving an absolute error of 5% maximum, typically 3%.

Quantum light measurement results were in pamol s- m-2 (1 nmol s-I m-2 is equivalent to

1 gEinstein s-1 m-2).

Light measurements were conducted on 28 July 28 1998, a cloudless day, from

1050 to 1145 AM. Measurements were made of ambient solar insolation outside the

wetland systems before and after measurements of each wetland cell. Approximately 30

measurements were made in each of the 2 wetland cells of wetland system 1 and 50

measurements in each cell of wetland system 2. Measurements were made 0.5 m in from

the edge of each cell and then every 1 m across the cells.

Canopy closure

Canopy closure in the wetland systems was evaluated in July 1998 using

analysis of hemispheric canopy photography (Rich, 1989). Photographic images of the

wetland canopies were made using a 180 fish-eye lens adapter on a Nikon camera. Nine

photos were taken at predetermined and equivalent locations in each of the wetland cells,

and in the discharge area of the mangrove ecosystem, then digitized and converted to a

gray scale using Photoshop 2.0. Analysis for amount of canopy and light penetration was

done with MapFactory software.









Analytic Measurements

Total nitrogen and total phosphorus

To determine nutrient treatment in the wetlands of phosphorus and nitrogen,

laboratory tests for total phosphorus and total nitrogen were conducted on wastewater

samples from the wetland treatment systems.

Phosphorus was determined using persulfate digestion followed by the ascorbic

acid method, SM 4500-P (APHA, 1995). Tests were conducted at the University of

Florida Water Reclamation Laboratory. Total nitrogen was determined using the

persulfate method, SM 4500-N (APHA, 1995).

Samples were collected from the septic tank, from the standpipe at the end of cell

1 and cell 2 in each wetland treatment system. A sample was collected from a cenote

(shallow groundwater well) with water accessible a few feet below ground level located

just a few meters from the wetland treatment system. This cenote is located on the inland

side of the wetland systems, and is presumed to give some indication of local

groundwater background levels. After collection in a 10 ml sample bottle, 1-2 drops of

concentrated sulfuric acid was added to preserve the samples until shipping to the

laboratory.

To determine variability in the total P and total N laboratory test, two samples

were run three times in August and September, 1997 so that standard deviation and

standard error of the mean could be determined.









Biochemical oxygen demand (BOD)

Biochemical oxygen demand (BOD) was determined using EPA method 405.1

(EPA, 1993). This is a five day test with sample kept at 20C. Samples (250 ml) were

collected as described above and kept cool during transport to the laboratory. The

materials were tested in laboratories in Cancun. The tests from January to April 1997

were conducted at Laboratorio Alquimia, Cancun and those from May 1997 were

conducted at the laboratory of Jose Castro in Cancun. Both are certified laboratories for

water analysis.

Chemical oxygen demand (COD)

Chemical oxygen demand in the water of the mangroves was determined

using the closed reflux, colorimetric method, APHA 5220D (APHA, 1995). The sample

was digested using K2Cr207, H2SO4, and HgSO4. Tests were conducted using Hach

prepared reagants, and analyzed on a Hach DR-3000 colorimetric instrument at the

laboratory of the University of Florida Water Reclamation Facility.

Total suspended solids

Total suspended solids (TSS) in the wastewater were determined using the

filterable residue, a gravimetric method with the material dried at 180C, EPA method

160.1 (EPA, 1993), method 2540DSM (APHA, 1995). 250 ml. samples were collected

from the seven points described above and stored for shipment to the Water Reclamation

Laboratory, University of Florida, where the tests were conducted.









Fecal coliform bacteria

Fecal coliform in the wastewater was determined using membrane filtration and

most probable number (MPN) of colonies per 100 ml of sample. This is method

9222DSM (APHA, 1995). Samples (175 ml) were collected from the seven points

described above and transported to the laboratory in Cancun for analysis within hours of

collection. The same laboratories that conducted the BOD-5 tests conducted the analyses

for fecal coliform until May 1998, when analysis was conducted in the water laboratory

of the Centro Ecologico Akumal.

Alkalinity

Alkalinity of the water samples was determined by titration (buret), method

2320B (APHA, 1995). Samples weighed 50 ml and the method used .02 N sulfuric acid.

Salinity

Salinity of water samples from the septic tank and wetlands was determined with

use of a hand-held refractometer accurate to +/- 0.5 parts salt per thousand.

Phosphorus Uptake by Limestone

Initial P content and uptake in wetlands

Samples of limestone were analyzed for initial phosphorus content and

phosphorus content after exposure to sewage in the treatment wetlands. Pre-exposure

limestone was collected during construction and bagged for later analysis. In December

1997 after one year of sewage treatment had occurred, composite limestone samples

were collected from each of the treatment cells of systems I and 2. These were divided

into limestone from the layer above the sewage line, and those at 0-10 cm depth, 10-20









cm depth, 20-30 cm depth, 30-40 cm depth and 40-50 cm depth. These limestone

samples were roughly pulverized mechanically then ground in a ball grinder.

Inorganic P analysis, conducted in the Wetland Biogeochemistry Laboratory at

the University of Florida, was determined as follows. Following grinding, the limestone

samples were dried in an oven at 70 deg.C. for 48 hours. Then a subsample (0.5 g) of the

ground limestone was extracted with 25 ml of 1M HCI for 3 hours, then filtered through

a 0.45 micrometer pore size membrane filter. The HCI extract was stored at 4C in a 20

ml polyethylene vial. The HCI extract was analyzed for inorganic P using an automated

ascorbic acid method (Method 365.1, EPA, 1995).

Calcium/magnesium composition of Yucatan limestone

The limestone was analyzed for calcium and magnesium content at the Soils

Laboratory of the Institute of Food and Agricultural Sciences (IFAS), University of

Florida.

The procedure was to grind and dry samples of limestone in a 120C oven for 4

hours. Then 5 x 1.0 gram dried sample was placed in a 1000 ml graduated beaker, and.

125 ml of IN HCI solution was added to dissolve the limestone. The solution was diluted

to 250 ml of 0.25M hydrochloric acid. The beaker was covered with a watch glass and

boiled gently on hot-plate for 10-15 minutes. Condensate was washed into beaker with

de-ionized filtered (D.I.) water and cooled to room temperature. The solution was

brought to approximate volume of 1000 ml. with D.I water. Analysis for

calcium/magnesium was by inductive coupled plasma spectroscopy.









Experiments on phosphorus uptake by limestone

To determine reaction kinetic rates of the Yucatan limestone with respect to

phosphorus, a series of lab and field experiments were designed. The experimental

procedure to determine phosphorus uptake by limestone was to combine limestone gravel

samples from the wetlands. Five hundred ml plastic bottles were filled with

approximately 250 grams of limestone gravel. Bottles were then filled with 450 ml of

phosphorus solution. This left some airspace below the neck of the bottles.

For the laboratory experiment, there were 5 experimental treatments x 3

replicates for a total of 15 bottles. The initial phosphorus concentrations were 5.6 mg

P/liter, 1 Img P/liter, 22 mg P/liter, 56 mg P/liter, and 111 mg P/liter. After addition of

phosphorus solution, bottles were maintained with caps only loosely on, allowing air

exchange. Bottles were shaken once a day. After 10 days, 10 ml. samples were taken and

filtered through a 0.45 pm membrane filter at 1,2,4,6 and 10 days. Separate syringes and

filter cases were used for each of the six treatments. Samples were stored in a freezer

until analysis for soluble reactive phosphorus.

For the field experiment, 3 x 500 ml. bottles with 250 grams of limestone gravel

prepared at the same time as the laboratory ones, were loaded with 450 ml of actual

wastewater from the septic tanks in Akumal, Mexico. Three bottles with 250 grams of

limestone were filled with 175 ml of actual wastewater (to approximate the condition in

the wetland treatment system that the sewage water covers the limestone). The bottles

had 10 ml. samples taken and filtered through a 0.45 micrometer membrane filter at

1,2,4,6, 10 and 30 days after loading. The samples were kept in a freezer until shipment

to the University of Florida Water Reclamation Laboratory for soluble reactive









phosphorus analysis. Analysis for soluble reactive phosphorus used EPA Method 365.1

(EPA, 1995)

Water Budget of the Wetland Systems

In May 1997 and December 1997 the water budget of the wetland systems were

determined by measuring inputs and outputs from the system. The only water inputs to

the systems are effluent from the septic tanks and direct rain, as no surface runoff or

groundwater enters the constructed wetlands. By draining the system 1 and system 2

septic tanks, and then measuring rate of re-fill, it was possible to estimate hydraulic

loading.

System evapotranspiration was calculated by measuring the decline over time in

the water levels of the standpipes in the control box at the end of each cell of the wetland

systems (see Figure 2-3 of the construction blueprints). Water-holding capacity of the

gravel used in the wetland was estimated by filling a known quantity (20 liter bucket)

with the limestone gravel and then measuring the amount of water that the volume holds.

The only outputs from the system are evapotranspiration and discharge from the

outlet in the control box of cell 2. Thus, once the average daily evapotranspiration is

calculated, the average discharge from the system may be estimated by difference from

average input from the septic tanks.

Economic Evaluation

Data on construction and maintenance costs of the wetland and package plant

sewage treatment systems were collected. Annual costs were estimated using expected

lifetimes of system components.









Emergy Evaluation

Comparative evaluations of the emergy involved in the wetland sewage treatment

system and a conventional "package plant" sewage system were carried out using survey

data on materials, labor, equipment used in constructing and operating the systems, plus

data on natural resource flow in the area. From these, emergy evaluation tables were

developed and emergy indices used to compare the sewage treatment systems.

Receiving Wetland


Biodiversity

Biodiversity of the mangrove area receiving discharge from Wetland system 2

was monitored for biodiversity before effluent began in December 1997. Biodiversity

was determined by ten transects of 100 individual plants identified to species. Shannon

diversity was then calculated from these data (see previous section).

Mangrove Soils

Depth of the mangrove soils in the vicinity of the wetland discharge was

determined in December 1997 by driving a piece of 1/8 inch steel rebar into the soil until

it struck rock. This was done in four directions, each 90 deg. from the next, from the

center of the discharge, with 20 total observations, each made at 3 m intervals. An

isopach map was generated from these data.

Wet/dry weight of the mangrove soils was determined in December 1997 by

drying five sample bags of 30 cm. deep soil cores at 70C until no further weight loss

was observed. Bulk density was calculated by taking five soil cores to a 30 cm depth and

then determining wet weight and dry weight after drying in an oven at 70 C until there









was no further weight loss. Five soil samples collected in December 1997 were analyzed

by the Soil Laboratory of the Institute for Food and Agricultural Sciences (IFAS),

University of Florida for total phosphorus and total nitrogen (using Kjeldahl method for

N and the dry ash method for P) and total organic content (by loss on ignition method).

These latter tests are described below:

Loss on ignition test for soil organic matter determination (Magdoffet al, 1996)

was used for soils with organic content greater than 6%. Five gram soil samples were

placed in a pre-heated oven at 120C for 6 hours. After cooling for 30 minutes, a weighed

subsample of soil was placed in a beaker and placed in a muffle furnace set to 450 C.

for at least 5 hours. For this study, samples were left for 14 hours. After cooling to room

temperature, final weight was recorded. Percent organic matter was determined by

comparing final weight with initial weight of the soil samples.

Total Kjeldahl Nitrogen (TKN) and dry ash method for phosphorus (Hanlon et al,

1998) were used by the IFAS Soil Laboratory in nutrient analysis of the mangrove soils.

In the TKN procedure, 0.5 g of soil is digested with 2.0 g of Kjeldahl mixture in a

digestion tube. The mixture is wet with pure water and 0.5 ml of concentrated sulfuric

acid is added. The tubes are placed on a preheated aluminum block digester at 150 deg C.

for 0.5 hours then the temperature is increased to 250C for 2 hours. One ml. of hydrogen

peroxide is added by pipette in two steps of 0.5 ml. A glass funnel is placed over the tube

and digestion continues for 2.5-3 hours. The tubes are removed from the digester and

cooled, then the sides of the tubes are washed with 5-10 ml of pure water. After mixing

with a vortex shaker, the digestate is moved to a 100 ml volumetric flask. Approximately

20 ml of solution is filtered through a Roger's Custom Lab 720 into a 90 ml. plastic cup.









A filtered subsample is transferred to a 20 ml. plastic scintillation vial and refrigerated

until analysis on the RFA (air-segmented, continuous-flow, automated

spectrophotometer). Final step is analysis on the RFA calibrated with digested standards

for total nitrogen.

In the dry ash P analysis, 1 g of oven-dry soil is combusted in a 500C muffle

furnace to ash for a minimum of 5 hours. The ash is then moistened with 5 drops of

distilled water and dissolved with 5 ml of 6.0M hydrochloric acid. After 30 minutes, the

solution containing the ash is transferred to a 50 ml volumetric flask and brought to

volume with pure water. A filtered subsample is transferred to a 20 ml. plastic

scintillation vial and refrigerated until analysis on the RFA (air-segmented, continuous-

flow, automated spectrophotometer). Final step is analysis on the RFA calibrated with

digested standards for total phosphorus.

Micro-analysis for soil composition

The mineral portion of the mangrove soils was assessed using X-ray diffraction

at the Soil Pedology Laboratory of the University of Florida.

After soil samples were mixed, organic materials were digested by addition of

sodium hypochlorite, 5.25% by weight, to cover the sample. After digestion for 20 hours,

each sample was put through a 15 micrometer sieve into distilled water. The soil sample

was centrifuged at 2500 RPM for 3 minutes and the supernatant liquid poured off. Then a

1 M solution of sodium chloride was added, and the solution again centrifuged at 2500

RPM and the supernatant poured off. Then de-ionized water was added to the solid

materials, and centrifuged at 3000 RPM for 5 minutes. Some of the liquid was poured

off, and oriented mounts were prepared for X-ray diffraction analysis by depositing









suspended materials onto porous ceramic tiles under suction. One of the tile mounts was

treated with potassium chloride, and two with magnesium chloride. The KCI and MgCI2

were added four times, and pulled through the ceramic tiles by a suction device. Then

each ceramic tile soil mount was rinsed with de-ionized water four times. To one of the

MgCl2 treated tiles, 30% glycerol was added. The clay tiles were then analyzed by X-ray

diffraction. Samples were scanned from 2 to 60 degrees 20 using a computer-controlled

x-ray diffraction system equipped with stepping motor and graphite crystal

monochromator. Power was 35 kV and scanning rate was 2 20 per minute.

Nutrients

Mangrove soil samples collected before and after discharge commenced, at the

beginning of May 1998 and monthly from June to August 1998, were analyzed using the

Total Kjeldahl Nitrogen and Dry Ash Phosphorus methods described above in the section

entitled Mangrove Soil. Soil samples were collected at 1, 3, 5 and 10 meters east, west,

north and south of the discharge point. Mangrove water samples collected in December

1997 and April 1998 were analyzed for biochemical oxygen demand, fecal coliform,

suspended solids, total nitrogen, total phosphorus, salinity and alkalinity using methods

described in the section on Analytic Measurements. These tests were repeated after

discharge commenced in May, and monthly samples were collected June, July, and

August 1998 to ascertain changes in the nutrient and water quality status of the mangrove

groundwater.









Hydrogeology

Water in the mangrove site at Akumal exchanged through groundwater channels

from below. There was no surface connection to the sea. Hydrologeological studies of the

fluxes with the receiving area were made by comparing surface water levels with those of

a nearby cenote (well) and the sea. This was done with a water level chart recorder of

surface water height during May 1997, December 1997 and July 1998

Direction of water flow in the area was determined from the heights of water in

three polyvinyl chloride (PVC) pipes, 10 cm in diameter, placed 60 cm deep in the

mangrove soils, which served as piezometers. Elevations were determined by use of

manual water-tube levels. Location and directional orientation of the piezometers was

determined with a surveying level. Water levels in the piezometers are equal to the

elevation of the hydraulic head (Fetter, 1994). Flow lines were determined by

triangulation of these data on a map of the potentiometric surface in the vicinity of the

discharge outfall. A series of 5 PVC monitoring pipes were installed in December 1997.

One pipe was installed 1 meter upstream from outfall of the discharge pipe from the

wetland, and three other pipes were installed 1,3 and 6 meters in the direction of water

flowlines in the mangrove. The fifth monitoring pipe was installed 12 meters southeast of

the discharge pipe, in the direction of the edge of the mangrove.

Simulation Model of the Water Budgets


Simulation models were developed for the treatment units and their discharge into

the receiving wetland. This model followed the methodology outlined in Odum (1994)

and Odum and Odum (1996). After selecting a system boundary, outside sources were









listed, from the environment and from the human economy. Relationships and pathways

between system components were identified including exports from the system.

Relationships were translated into energy language symbols and then into rate equations.

After average values were put on the pathways and in storage symbols, coefficients were

calculated with spreadsheet. A simulation program was written in BASIC and sensitivity

studied with scenarios. Simulation runs were compared with field and literature data.

Evaluating Potential of Wastewater System for the Coastal Zone


Potential significance of the treatment system was studied by considering a square

kilometer of developed coastal area operating the treatment system. Evaluations were

done on two scales: the treatment systems and the square kilometer.

Emergy Evaluation

An emergy evaluation of the square kilometer area was made using data from

published sources, data on use of natural resources and human services obtained from

hotel owners, homeowners and residents, and from town maps showing density and

layout of properties in the area.

Emergy analyses followed methods developed by Odum and Brown (Odum,

1996; Doherty and Brown, 1993; Brown and Ulgiati, in press). This was done by

developing systems diagrams showing energy sources, system components, pathways of

energy and material flow in the system, system outputs and depreciation/heat sinks.

These systems diagrams were developed in three forms: detailed, aggregated and three

arm diagrams. Then data was collected, using published and new data, on material and

energy flows.









Transformities

Emergy tables were compiled, using transformities for the items. Table 2-1

presents the transformity values used in all the emergy evaluations of the present study.

With these system relationships and data, indices to compare emergy flows of the

environment with those of the natural environment are evaluated. Among the indices

evaluated were the investment ratio, emergy yield ratio, ratio of nonrenewable to

renewable resources and empower density. These emergy indices characterize the

intensity and balance of environmental vs. developed resources (Odum, 1996).

Economic Evaluation

Economic impact on the square kilometer coastal area were compared for the use

of treatment wetlands or conventional package plant treatment systems. These data were

evaluated as a percentage of overall capital investment and yearly monetary flow.

Regional Water Budget

A regional water budget for a square kilometer of coastline in the study area was

developed including precipitation, inflow of groundwater from inland, tidal exchange,

evapotranspiration, pumped water and sewage. Budgets were compared for development

with no sewage treatment and development with treatment by constructed wetlands.

Regional Nutrient Budget

Regional nutrient budgets were developed for the same scenarios that of

development of a square kilometer of the Akumal coastal region. Nutrient budgets for

nitrogen and phosphorus were examined for the scenarios of fidull development without

sewage treatment and with treatment by constructed wetlands.









Table 2-1 Transformities and emergy per mass used in this study.


Item


Transformity
Sej/J
solar emjoule/joule


Sunlight
Wind, kinetic
Rain, geopotential
Rain, chemical potential
energy
Tide
Waves
Earth cycle
Wood
Groundwater
Gas
Motor fuel (liquid)
Primitive labor
Food
Hurricanes
Electricity (global average)

Agricultural and forest
products
Untreated wastewater
Concrete
Plastic products
Pulp wood
Sand
Limestone
Steel + iron products
Potassium chloride

a Odum, 1996
b Odum and Odum, 1983
c Brown etal, 1992
d Scatena et al., in press
e Christiansen, 1984
f Green, 1992
g Odum etal., 1983
h Brown and McClanahan,


Emergy per mass Reference
Sej/gram
solar emjoule/gram


1 (by definition) a
6.63 E2 a
8.888 E3 a
a
1.5444 E4
2.3564 E4 a
2.5889 E4 a
2.9 E4 a
3.49 E4 c
4.8 E4 a
4.8 E4 a
6.6 E4 a
8.1 E4 b
8.5 E4 c
9.579 E4 d

1.736 E5 a
2E5 c

5.54 E5 f
7.0 E7 h
9.26 E7 c
2.75 E8 e
1.0 E9 a
1.0 E9 a
1.78E9 a
1.1 E9 a
1.25 E10








1992














CHAPTER 3
RESULTS

Treatment Mesocosms


Design and Operation of the Wetland Units

In August 1996, the two wetland sewage treatment systems were constructed.

One, henceforth referred to as "wetland system 1" was designed to treat the wastewater

of 16 people and covers an area of 50.6 inm2. The second, "wetland system 2", designed to

handle the sewage of 24 people, has an area of 81.2 min2.

The treatment process for each wetland begins with a well-sealed two-chamber

septic tank which receives wastewater from the residences and offices by gravity flow.

Solids settle out in the septic tank which serves as primary treatment, and the

commencement of microbial treatment of the sewage. A filter at the discharge pipe from

the septic tank ensures that no solids larger than 1/64 inch can enter the wetland. Effluent

from the septic tank overflows by gravity feed into a header pipe which distributes the

sewage along the total width of the first of two treatment cells (compartments) of the

constructed wetland.

These wetlands were designed as subsurface flow systems, and have a cement

liner and sides to prevent movement of untreated sewage into the groundwater. They

were filled with limestone gravel to a depth of 0.6 m. Each cell of the wetland has a

collector, perforated 4 inch PVC pipe at the end which direct wastewater into the









centrally-located control box. Inside the control box, an adjustable standpipe determines the

level at which wastewater is maintained in the wetland, as wastewater overflows its

open end either from Cell 1 into the header pipe for Cell 2, or from Cell 2 to final discharge.

Normally, the standpipe is fully vertical at a height of 55 cm. The wastewater is kept 5 cm

below the level of the gravel. The sides of the system are at least 15 cm above the top of the

gravel to allow for natural litter buildup and to prevent overflow in heavy rains. The terrain

was graded to preclude surface water runoff inflow into the wetland systems. Hydraulic

residence with design loading is 5-6 days depending on seasonal evapotranspiration.

After the cement liner was completed, the system was filled with water and leak-

tested. Then the gravel was added and leveled. Larger limestone rock (5-10 cm) was used

in the first and last meter of each cell, around the header and collection pipes, to minimize

the dangers of clogging. After the addition of the gravel, the systems were filled with

tapwater and planted with wetland plants gathered from nearby wetlands, or purchased from

botanical gardens or commercial plant nurseries in the area. Soil was not introduced into the

system, except for rootballs of the plants. The plants were planted with at least 2-5 cm.

contact with the water. After planting, the two wetlands were mulched with 2-4 cm sawdust.

After discharge from Cell 2 of the wetland, the wastewater from System 1 enters

perforated drainage pipes that slope away from the wetland. The trenches in which these

pipes were laid were back-filled with limestone gravel to prevent clogging by dirt. System 2

effluent is sent to the nearby mangrove wetland and discharged near soil surface.

The blueprint drawings (Figures 3-1 to 3-10) show additional details of the

construction. Limestone gravel depths were increased for wetlands built subsequently to this

research in the area were done to a design specification of 80 cm to increase hydraulic








Subsurface Wetland
Sewage Treatment
Design, Mark Nelson
Pafle I oF 10 ,Date' 10/02/97


Overall


Isometric


View


Copyrloht 19971 Mark Nelson, ConFIdentlaLt


Notes
DAll wattlls 4'waterproof concrete, leak test
cells and control boxes before grovel fill
P)Backfill and grade all sides of wetQland to
prevent rainwater spillover
3)Trenches for leach field piping covered with
gravel and filltted to prevent dirt clogging


Figure 3-1 Construction blueprint: isometric view of the wetland treatment system.







Subsurface WetLand
Sewage Treatment
Deslgni Mark Nelson
Page 2 of 10 |Date, 10/02/97


2'-5 3/a8'


S.-<"


Overall.


Isometric


View of Piping


Copyright 19971 Mark Nelson, Confidential


Notes
D)Al Piping 4' PVC, see details pages 6 and 7
2)Septic tank and leach Field gravity Feed
require at least I to 50 slope For proper f
3)Septic Tank and/or grease trap require
Zoabel Filter
4)Cover all piping to prevent sun damage
5)Collector pipe risers optional
6)Renovable caDs on risers


Figure 3-2 Construction blueprint: isometric view of piping in the wetland system.


-


6k.P
-pr
.J i


"-A








Subsurface Wetland
Sewage Treatment
Design, Hark Nelson
Page 3 of 10 IDate, 10/02/97


Stones 2' to 4'
to surface

Pea Gravel
31' Deep
Mulch
/- l*Deep


i

I-..


ninlInun 6"


Center


Section


View


Copyright 1997, Harlk Nelson, Confidential


Notes#
D)AI walls 4' waterproof concrete
2)Vaterlevel 30. pea gravel 31' deep
3)Mutch layer 1' applied after planting
4)2' to 4' rock fillt to 31', cover with nulch
4 places
5)All rock and gravel fill must be washed
6)2' to 4' rock around collector pipes not
shown due to perspective
7)Positlon standpipe next to one wattll of the
control box ensuring that It can be lowered to
horizontal position within the control box


Figure 3-3 Construction blueprint: center section view of the wetland system.







SubsurFace Wettand I


Sewage Treatment I


Design, Mark Nelson l
Page 4 oF 10 Mlate, 10/02/97


Stones 2' to 4'
dia., to surface


Pea Gravel
31' Deep

Mulch
-- 1'Deep


I. (,'


Stones 2' to 4'
dla. to surface

Pea Gravel
31' Deep

Hutch
/- 1'Deep


Side Section


Showing Fill Materials


Copyright 1997a Mark Nelson, Confidentialt


Notes'
l)AIl watts 41 waterproof concrete
2)Vater level 30', pea gravel 31' deep
3)Mulch layer 1 applied after planting
4)2' to 4' rock Flit to 31', cover with nulch
4 places
5)Altl rock and gravel Fill nust be washed


I__________________________________


Figure 3-4 Construction blueprint: side section showing fill
system.


materials in the wetland


|


nilnlnun 6'







Subsurface Wetlandc
Sewage Treatment
Design Mark Nelson
Page 5 of 10 IDatei 10/02/97


Box Detail with


Dimensions


1997, Mark Nelson, Confidential


Notes'
1)1' thick wood control box cover, seated with
rubber gasket to prevent odor and Mosquito
breeding
2)4' waterproof concrete walls
3)Posltion standpipe next to one wall of the
control box ensuring that It can be lowered
horizontal position within the control box


Figure 3-5 Construction blueprint: control box with dimensions ofthe wetland treatment
cells.


Copyright








Subsurface Wetland
Sewage Treatment
Design. Mark Nelson
Page 6 of 10 jDate. 10/02/97


b. ^


Cell 1 Header Deteail


Copyright 19971


Mark Nelson, ConFidential


Notes
)Alt hatoles drlUed at centerline of 4* pipe
2)Durlng rock Filling, pipe must remain level
3)Septic tank and/or grease trap require
Zabel filter to prevent solids from entering
treatment system


Figure 3-6 Construction blueprint: treatment cell I header detail of the wetlands.


I









SubsurFace W/etland
Sewage Treatment
Desl ni Mark Nelson
Page 7 of 10 |Da'te 10/02/97


Cell 2 Header Detail



Copyright 19971 Mark Nelson, Confidential


Notes
1)4 PVC pipe sow scored at 1I Intervals
2)Ensure that during rock FlU, header pipe
renalns Level


Figure 3-7 Construction blueprint: treatment cell 2 header detail of the wetlands.


I








SubsurFace Wetland
Sewage Treatment
Design' Mork Nelson
Page 8 oF 10 IDate, 10/02/9


Large


Copyright 19971


System


Drainfield


Detail


Mark Nelson, Confidential


Notes,
D)Eoch drolnFleld pipe nust have a riser with
renovable cap for maintenance
2)Dralnfleld piping must have a nin. slope of 1150
for proper flow
3)Anount of dralnFleld needed depends on
system size


Figure 3-8 Construction blueprint: schematic showing drainfield detail for large wetland
systems.








SubsurFace \ettand
Sewage Treatment
Design' Mark Nelson
Poae 9 oF 10 IDate, 10/02/97


4-
1.
-~
A.


Small System


DrainField Detail


Copyright 1997i Mark Nelson, Confidentlal


Notes,
)DDralnfleld pipe nust have a riser with
removable cap for Maintenance
2)Dralnfield piping Must have a min. slope of 1'50
for proper flow
3)Amount of dralnfleld needed depends on
system size


Figure 3-9 Construction blueprint: schematic showing drainfield detail for small wetland
systems.







Subsurface Wetland
Sewage Treatment
Design' Mark Nelson
Poage o 10 DoF oDate, 10/02/97


Cover gravel with
6' sand or soil,


Geo-Textlle
Cloth







6' min. gravel
under pipe


4' perforated
drain pipe, silts
facing down


Drainfield


Cross


Section


Notes
lDMIn. slope 1,50 For proper Flow
2)Pipe perforated with saw cuts
3)Cross section shown here applies to all
dralnFleld Installations unless specified other-
wise


Copyright 19971 Marl Nelson, ConFidential I


Figure 3-10 Construction blueprint: drainfield cross-sectlion drawing or wetland system.









retention time, rather than the 60 cm of limestone used in the two research wetlands of this

study.

Ecological Characteristics

Patterns of biodiversity and dominance

In May 1997, December 1997 and July 1998 (nine, fifteen and twenty-three months

after planting, respectively) examinations of the wetland systems for species diversity was

conducted with the assistance of Edgar Cabrera, a botanist from Chetumal, Quintana Roo. A

total of 68 species were identified in May 1997, 70 species in December 1997 and 66 species

in July 1998 (Table 3-1). Species native to the Yucatan constituted 47 of the 66-68 species

present in May, 1997 and December 1997, with the remainder being cultivated and

introduced species.

Plant species richness (total number of species present) in each treatment cell

decreased slightly over the course of the study as shown in Figures 3-11, 3-12 and 3-13. For

example System 1 Cell 1 had 41 species in May 1997, 37 species in December 1997 and 35

species in July 1998; while System 1 Cell 2 had 37 species in May 1997,35 species in

December 1997 and 36 species in July 1998. In May 1997, wetland System I averaged 39

plant species per cell, in December 1997 and July 1998, the average was 36 species.

Wetland System 2 averaged 47 species per cell in May 1997,45 species in December 1997

and July 1998.

Considering the systems as a whole, in May 1997 there were 63 species in System 2

(with 482 observations), 17% higher than in wetland System 1 with 54 species (from 482

observations) (Figure 3-14). By December 1997, plant species had declined by about 10% in









Table 3-1. Plant species in the treatment wetlands from surveys of May, 1997, December,
1997 and July, 1998. Total number of species as of May, 1997: 68 species; as of December,
1997: 70 species, as of July, 1998: 66 species.


Scientific Name

D2 Acalypha hispida

Acrostichum danaefolium
Ageratum littorale

Alocasia macrorhiza


N2 Aloe vera
N2 Alternanthera
ramossissima
Dl Angelonia angustifolia

Anthurium
Schlechtendalii
N1 Anthurium sp.
Asclepias curassavica
Dl Bambusa sp.
Bidens pilosa

Bravaisia tubiflora
Caladium bicolor
Canna edulis

N2 Capraria biflora
Carica Papaya
Dl Cestrum diurnum

Chamaedorea Seifrizii
Chamaesyce
hypericifolia
Chrysobalanus icaco


Common Name

Cola de gato; cat's
tail
Helecho


Mafota; elephant
ears, taro

Sabila




Moco de povo



Bambu; bamboo
Margarita

Sulub
Bandera
Platonillo; canna
lilly
Claudiosa
Papaya
Galon de noche

Palma camedor


Icaco


NI1 Cissus sicyoides
Cissus trifoliata


Citrus Aurantium


Naranja agria;
orange tree


Notes: N = Native, I =
Introduced; C= Cultivated
C; red cattail flowers

N; wetland fern, to 3 m
N: blue-flowering little shrub
(purplish flowers); annual
I; starchy root, very shiny
Large leaves; leaf is straighter
and flatter than Xanthosema
C;
N

N; delicate shrub, purple
flowers
N; epiphyte

N
N; orange and yellow flowers
I;
N; yellow or white flowers
(like daisy)
N; pink flowers like bells
C; decorative taro
I; yellow flowers

N
N; edible fruit
I; shrub/tree CEA Cell 2, long
thin leaves
N; palm
N; delicate shrub with tiny
white flowers
N; woody, sturdy shrub with
thick leaves
N;
N; vine, elongated, ovate
leaves
C; edible fruit




















N2
Dl
D2
N1
NI;
D2


Scientific Name

Coccoloba uvwifera

Conocarpus erecta

Corchorus siliquosus

Cordia sebestena

Crinum amabile
Cucumis melo
Cyperus ligularis
Delonix regia
Desmodium incanum


N2 Desmodium tortuosum
Distichlis spicata.
Dl Eclipta alba

Eleocharis cellulose
DI Eleusmine indica
Eupatorium albicaule

DI Euphorbia cyathophora

Dl Eutachys petraea

Flaveria linearis
Hymenocallis littoralis
N1 Ipomoea indica


N1;
D2


Ipomoea Pes-caprae
Iresine celosioides


Ixora coccinea

Kalanchoe pinnata
Dl Lactuca intybacea
D2 Lantana involucrata


Common Name

Uva de mer; sea
grape
Botoncillo;
buttonwood tree


Siricote

Lidio reina
Melo; melon
Zacate cortadera
Poinsettia


Spike reed grass


Lirio/Spider lilly
morning glory

rinonina


Ixora


Milk weed
oregano xiru


N2 Leucaena glauca


Notes: N = Native, I =
Introduced; C=Cultivated
N; beach tree, prostrate or
upright
N; mangrove area tree

N; woody shrub, long-hard
seed pods (tree)
N; tree with large leaves, (next
to Eleocharis CEA Cell 2)
C
I; melon vine
N;
C;
N; 3-leaved leguminous vine

N
N; grass
N; like botoncillo with dots on
leaves;
N; short wetland reed
N;
N: 2 notches on leaves nearer
base
N;

N; grass with "feathers" on
ends
N; yellow flowers
N; white flowers;
N; vine with heart-shaped
leaves
N;vine, morning glory family
N; flowers are scales

I; yellow or orange flowers,
low shrub
I;
N; CEA Cell 1
N; small flowering shrub,
woody shrub; small serrations
on leaves; succulent; fragrant
leaves
C









Scientific Name

NI; Lochnera rosea
D2
Dl Ludwigia octavalis
Dl Lycopersicum esculenta
D2 Melanthera nivea


N2 Mimosa sp.
Malvaviscus arboreus
Musa sp.
Nerium oleander
N1 Nopalea cochinillifera
Paspalum virgatum
Pedilanthus
tithymaloides
N1; Pelliciera alliacea
D2
Philodendron sp
Phyla nodiflora



N2 Phyllanthus niruri
Pluchea odorata
Dl Porophyllum punctatum

DI Portulaca oleracea

Psychotria nervosa
Rabdadenia biflora

N2 Rhizophora mangle
Rhoeo discolor

Sansevieria triasiate
Scindapsus aureus
N1; Selenicereus Donkelaarii
D2
Senna biflora


Common Name

Teresita


Tomate; tomato




tulipancillo
Platano; banana
Oleonder; oleander
Napolito
Sacate


Santa Maria


Verdolaga; moss
rose



Red mangrove
Platonillo morado;

Lengue de suegra
Telefono


Modrecacao


Dl Sesbania emerus


Notes: N = Native, I =
Introduced; CCultivated
C; lavender flowers

N; yellow flowers
I; tomato plant
N; small button-white flowers
on sprawling shrub; 3-lobed
leaves
N
N; red flowers, tree
C; edible fruit
I; pink flowers, small tree
C; cactus; used as food
N; sharp-leaved clump grass
I;

N; long stalk, delicate flower

N;
N: red stems, white flowers,
sprawling shrub with sharp
notches near tip of leaves,
deep-grooved veins
N
N; purple flowering shrub
N; decorative black dots on
leaves, shrub, small leaf
N; various colors

N;
N; "mangrove-like" vine CEA
Cell 2
N
N; purple and green leaves,
roseatte form
C; small agave-like
C; variegated leaves
N: viney, thin cactus

N; tree with rounded leaves;
with a bunch of small, varied
colored flowers
N; tree with leguminous leaves









Scientific Name

Sesuvium portulacastrum

Dl Solanum erianthum
Solanum Schlechtendalii

N1; Syngonium sp.


NI:
D2
NI

N1;
D2


Terminalia Catappa

Thrinax radiata
Typha domingensis
Vigna elegans


Common Name

Verdolaga de playa;
succulenta


Almendro

Chit
Tule; cattail


Vigna luteola


Viguiera dentata


Washingtonii robusta

N1 Wedelhia trilobata
Xanthosoma roseum

Zamia purpuraceus
N 1 Zephyranthes Lindleyana


Washingtonii palm


mafata; taro,
elephant ears


Notes: N = Native, I =
Introduced; C=Cultivated
N; beach succulent

N;
N; red berries like small
tomatoes
N; palmate leaves, 5-folias

C; comer PCRF Cell 1 nr
septic tank; tree
N; palm, used for thatching
N; to 3-4 m
N; vine, 3-leaves, purple
flowers
N; yellow flower otherwise
similar to V. elegans (77)
N

C: palm tree; sharp thorns on
fronds
N; vine, yellow flowers
N; starchy root; soft-leaved and
more curved leaf form of taro
C; purple flowering shrub
C; thin, short blades, grass-like
with pink flower


Plant species identified by Edgar F. Cabrera, Chetumal, Q.R. on surveys in May and
December 1997, and July 1998.Code for column 2, DI = dead or not found in December
1997 survey but present in May, 1997 survey; N1 = new in December 1997 survey; D2 =
dead or not found in July, 1998 survey, N2 = new in July 1998 survey.

Botanic names: Cabrera, Martinez (1987), UNAM (1994), Brummitt (1992).



























*System 1, 1st treatment compartment
--- System 1, 2nd treatment compartment
-A- System 2,1st treatment compartment
-- System 2, 2nd treatment compartment


1 9 17 25 33 41 49 57 65 73 81 89 97 105 113 121 129 137 145 153 161 169 177 185 193 201 209 217 225 233
Number of observations in transect, May 1997

Figure 3-11 Species-area curves for each of the four wetland treatment cells, May 1997
data.


























--- System 1, 1st treatment compartment
--- System 1, 2nd treatment compartment
-A- System 2, 1st treatment compartment
-*- System 2, 2nd treatment compartment


1 10 19 28 37 46 55 64 73 82 91 100 109 118 127 136 145 154 163 172 181 190 199 208 217 226 235 244

Number of observations in transect, December 1997

Figure 3-12 Species-area curves for each of the four wetland treatment cells, December,
1997 data.























!E 35
0

A 30
0
0.
4)
._ 0


o 25
L-
0
E
20



E 15



10


5h




0 flt i m 19 9 i9t1 l 9 Il II9 I III H I II III t iff Iiff IIIII of I I II 111fi 11 III t 9 9t91 ill I III 11111i If III# I I 1i tff II I II 11111 it ll I tif1 99 I P11` l I I1 9 I + 11 94191 t1| 4 fl t 99t4i1919tt I99499| 11 1 1 *t 9 I 9II 1tt9 99|ti |itt 11 F 1t 9 I I M OW1|9 I99 *t1 i it9if t
,-. N ,) r ,- (0 ,. 0 0, 0 -_ N N "- IfU ,1 f 0 r',- in 0 M

Number of observations In transects July 1998N

Figure 3-13 Species-area curves for each of the four wetland treatment cells, July, 1998
data.


-U-Wetland system 2 Cell 1
- Wetland system 1 Cell 1

-M- Wetland system 1 Cell 2
-4-Wetland system 2 Cell 2












60 ..................... ...... ................... ....... ........... ... ............. ......




o 5 0 .....................................
4)


0.
40 ............
CL
30

ME 30
C


E 20 ... ... .. ..... ........... .......... .... ..... ..












Number of observations in transect, May 1997

Figure 3-14 Species-area curves for the 50.6 m2 wetland unit (system 1) and the
81.2 m2 wetland (system 2), May, 1997. Transects counted 482 individuals in each
system.


--- Wetland treatment system 1
--Wetland treatment system 2









the individual wetlands (Figure 3-15) although overall number of species present in both

wetlands increased slightly (from 68 to 70 species). Many of the species no longer present

were low, understory shrubs, while almost half the newly present species were native vines.

In July 1998, System 1 lost an additional 10% of species, with a total of 44 species,

while System 2 remained constant at 57 (Figure 3-16), although again both numbers included

a loss of some previously present species and establishment of new species (Table 3-1).

Comparison with natural ecosystems

In December 1997, transects with 1000 observations showed 73 species present in the

inland tropical forest ecosystem, and 17 species in the natural mangrove wetlands, compared

with the 70 species found in the constructed wetland treatment systems (Figure 3-17). Table

3-2 lists the species found in the mangrove and Table 3-3 presents the species found in the

forest ecosystem. Figure 3-18 compares number of species in treatment wetland systems 1

and 2 with number of species found in the transects through forest and mangrove ecosystems.

The wetlands had diversity of plant species comparable to that found in nearby forest

ecosystems and a much greater number of species than were found in the adjacent mangrove

wetlands.

Dominance

Dominance was assessed through species relative frequency, Shannon diversity

index, percent cover, estimate of areal coverage and importance value.




































Figure 3-15 Species-area curves for the 50.6 m2 Yucatan wetland (system 1) and the
81.2 m2 wetland (system 2), December, 1997. Transects counted 500 individuals in each
system.


-*- Wetland treatment system 1
--0-Wetland treatment system 2











60






50



1a

4-
lo
C 40
a)
'0
(0
V
._





0





E
30
.0






10


Figure 3-16 Species-area curves for the 50.6 m2 Yucatan wetland (system 1) and the
81.2 m2 wetland (system 2), July, 1998. Transects counted 500 individuals in each
system.


---Wetland system 1
-f-Wetland system 2










-4


0~ ______ __________________ _________________------------ ----- ---------




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PAGE 1

LIMESTONE WETLAND MESOCOSM FOR RECYCLING SALINE WASTEWATER IN COASTAL YUCATAN MEXICO By MARK NELSON A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 1998

PAGE 2

Copyright 1998 On Construction Blueprints pp. 55-64 (Figures 3-1 to 3-10) By Mark Nelson

PAGE 3

ACKNOWLEDGMENTS I would like to thank my dissertation committee and especially its chair Howard T. Odum who was an invaluable friend critic catalyst and inspiration for my work in ecological engineering I was fortunate to have a committee of gifted teachers and scientists whose professional fields spanned the topics covered in the research Mark Brown my co-chair gave freely of his knowledge of emergy analysis wetland ecology and restoration K.R. Reddy is a master of wetland biogeochemistry and generously made his laboratory available. Daniel Spangler is a gifted theoretical and field hydrogeologist who helped design much of the mangrove research Clay Montague shared his expertise in estuarine dynamics and ecological modeling. I owe a debt to all of them for their support guidance and patience. The present study would not have been possible without the generous support of the Planetary Coral Reef Foundation Bonsall CA and Akumal Q R. Mexico The wetland systems have been recipients of the hard work, intelligence and care of Abigail Alling Gonzalo Arcila John Allen Mark van Thillo Ingrid Datica and Klaus E iberle who share the vision of coral reef protection and bringing appropriate new technology to the tropical world I am indebted to Richard Smith laboratory manager and the Water Reclamation Facility of the University of Florida for making possible most of the water quality analyses. Yu Wang manager of the Biogeochemistry Laboratory Soil & Water Sciences ii

PAGE 4

conducted the limestone / phosphorus analyses, and Biol. Edgar F Cabrera contributed his extensive knowledge of the plants of the Yucatan The Center for Wetlands supported my work with a research assistantship and by providing a stimulating environment of creative staff and students The Centro Ecologico Akumal (CEA) contributed the land for the research wetland units and financially assisted in their construction costs Charles Shaw staff geologist for C E A greatly assisted by sharing his research on the hydrogeology of the region Finally I would like to thank my colleagues in the Institute ofEcotechnics for allowing me the time to pursue this research, and for all the camaraderie and challenge during more than two decades of wonderful ecological work. Friendship honor discipline and beauty. iii

PAGE 5

TABLE OF CONTENTS ACKNOWLEDGMENTS .......................................................................... .ii LI ST OF TAB LE S ............................. .................... .............................. viii LIST OF FIGURES .. ........ .......................... ....................................... ...... xiv ABS1RACT ........................................................................................ xx.ii CHAPTER 1 : INTRODUCTION ......... ........................................................ 1 Scientific Questions in Ecological Engineering of Wastewater.. .................. ... 2 Wastewater Interface Ecosystems in the Tropics ......................... ..... 2 Wastewater Interactions in Landscapes with Soil Substrate of Limestone .................................................... 3 Salty Wastewater. . .. ............... ... .. . ...................................... 4 Using Small-Scale Mesocosm Tests to Evaluate Regional Potentials ....................................................... .4 Problems of Fitting Water Systems to the Landscape .............................. ... 5 Unique Characteristics of Tropical Coastal Development ........... ... ...... 5 E utrophication Impacts on Coral Reefs ..... .................................... 6 Issues of Human Health ........... ........................ .. ..................... 7 Previous Studies .............................................................................. 8 Study Sites in Yucatan ..................................................................... 10 Regional Study Area : Akumal Coastline ............... ... .................... 10 Growth and Development in the Yucatan ..................................... 13 Sites ofMesocosm T ests ......................................................... 19 Receiving Wetland ............................................................. .. 19 Concepts ..................................................................................... 24 Aggregated Conceptual Model .................................................. 24 Diversity vs Trophic Conditions in the Interface Treatment System ....................................................... .26 E cological Succession in the Treatment S y stems ............................ .2 7 Major Objectives of the Research ....................................................... .28 Plan Of Stud y ...................................................................... ........ 28 Sampling and Measurement. .................................................... 29 Outline of the Research Report .................. ... ............ .......................... 30 CHAPTER 2: METHODS ......................................................................... 32 Treatment Systems .................... .................................................... 32 JV

PAGE 6

Ecological Engineering Design ............... .................................. 32 Procedures for Start-Up and Management .................................... 34 Seeding with Biota ............................................................... 34 Field Measurements ............................................................... 35 Biodiversity .................... .................... ....................... 35 Frequency ................................................................. 36 Cover ...... ................................................................. 36 Importance value ......................................................... 36 Leaf area index ............. ............................................... 36 Leaf holes .................................................................. 37 Surface organic matter.. ................................................ 37 Solar insolation ........................................................... 37 Canopy closure ...................... ..................................... 38 Analytic Measurements ......................................... ................ 39 Total nitrogen and total phosphorus ................................ ... 39 Biochemical oxygen demand (BOD) ............. ................. ... .40 Chemical oxygen demand ........................................ .. ... .40 Total suspended solids .................................................. .40 F ecal coliform bacteria ..................... .... ...................... ..41 Alkalinity .................................................................. 41 Salinity .................................... ................................ 41 Phosphorus Uptake by Limestone . ............................................ .41 Initial P content and uptake in wetlands ............................... 41 Calcium/magnesium composition of Yucatan limestone .............................. ............... .42 Experiments on phosphorus uptake by limestone ................... 43 Water Budget of Wetland Systems ............ ................................. 44 Economic Evaluation ........................ ..................................... 44 Emergy Evaluation ................................................................ 45 Receiving Wetland ............................................................... .46 Biodiversity ........................................................................ 46 Mangrove Soils ................................................................... .46 Hydrogeology ...................................................................... 49 Simulation model of water budgets .................................... .. ............. .49 Evaluating the Potential of Wastewater System for Coastal Zone .......... ....... 50 Emergy Evaluation ............................................. ................... 50 Transformities ...................................................... ...... 51 Economic Evaluation ........... .................................................. 51 Regional Water Budget .................. ......................................... 51 Regional Nutrient Budget ........................................................ 51 CHAPTER 3: RESULTS ................... ................................. ..................... 53 Treatment Mesocosms ................................................................. .... 53 V

PAGE 7

Design and Operation of the Wetland Units .................................. 53 Ecological Characteristics ....................................................... 65 Patterns of biodiversity and dominance ........................... .... 65 Comparison with natural ecosystems ... ............ .................. 74 Dominance . ... . ........... .................................. 74 Shannon diversity index .................. ...................... 81 Plant cover ................................................................ 81 Plant frequency ........................................................... 88 Importance values .............. ..................................... .. ... 93 Leaf area index .............................................. . ... ...... 100 Leaf holes ... .............. ... ........................................... 100 Surface organic matter. ........................ ........................ ll 0 Solar insolation ........ ............................ .................. ... 112 Canopy closure ................................. .......... ............... 112 Chemical Characteristics and Uptake .................... ..................... 117 Phosphorus .......... ....... ................................ .... ........ 117 Nitrogen ................................................. ......... ........ 123 Biochemical oxygen demand ............... .................. ........ 128 Total suspended solids ................................................ 128 Alkalinity .............. .......................... . ..................... 137 Salinity ................................................................... 13 7 Reduction in Coliform Bacteria ................................................ 140 Phosphorus Uptake by Limestone ............ ................................ 140 Ca/Mg analysis oflimestone . . . . . . . . . . . . . . . . . . . . .. 140 Initial and uptake phosphorus levels . . . . . . . . . . . . . . . .. 146 Experiments on limestone P uptake ................................. 149 Water Budget. .................................................................... 153 Economic Evaluation ...... ............ ... ....................................... 153 Emergy Evaluation ........................................................... .... 157 Receiving WetlandGroundwater Mangroves ....................................... 176 Biodiversity .................................. ............ ........................ .176 Mangrove Soils ... ......... .................................... .. ... ......... 176 Nutrients .............................................. . .......................... 180 Hydrogeology of Coastal Zone ................................................. 189 Cross section ..................................................................... 189 Groundwater ....... ..................................................... 189 Water quality in mangroves ........... ..................................... ... 192 Total nitrogen .............. .... .................................... ...... 192 Soluble reactive phosphorus............................... ........ 199 Chemical oxygen demand ... ........... ................... ... ....... .. 199 Total suspended solids ............................................ .. ... 199 Coliform bacteria ...................................................... 203 Salinity ................................................................... 203 Simulation of Water in Treatment Units and Mangroves ...... .... 206 vi

PAGE 8

Regional Potential of Wastewater System ............................................ 219 Definition of Coastal System ........... . .......... ............... ....... . 219 Emergy Evaluation ............................................ ............... . 219 Economic Evaluation . .................................. ....................... 229 Water Budget ..................................................................... 230 Nutrient Budget .................... . ............................................ 234 CHAPTER 4 : DISCUSSION ... .................................. .... ..................... ...... 247 Contribution of Research to Science of Ecological Engineering ................. 247 Ecological Succession in the Limestone Wetland Units ........................ .... 248 Comparisons of the Akumal Systems with other Treatment Approaches ... .... 250 Comparisons with Temperate Latitude Interface Systems .......................... 254 Comparison ofEmergy Indices of the Akumal Units .... ...................... ... .256 Role of Limestone Substrate ............................................................ 260 Seasonal Changes and Effect of the Dry Season ............................ .. ... .... 261 Treatment of Wastewater Containing Sea Salt.. ...... ............................. 263 Simulation of Hydrological Extremes ....................... .... ... .............. .... 264 Transpiration of Treatment Systems ... ............................. . ............... 264 Maintaining Vegetative Biodiversity .. ..... .......................... ........ . . . .. 265 Impacts of Effluent Disposal on the Mangroves ...... .......................... .... 266 Carrying Capacity for People Coastal Development Potential. .............. ... .267 Percent of Economy Required for Wastewater Processing ..... .... .............. 268 Perspectives from Regional Simulation Model. ....... ........................... ... 269 Future Potentials of the Designed Treatment System ................................ 276 Long-Term System Prospects ... ............................. ......................... 277 Authorization Meeting in Mexico ................... ................................. 279 Questions for Research ... ..... ........................................................ 280 Biodiversity . .. ... ................................. ..... .................... . 280 Mangrove Change ............................................................... 281 Useful Life of the Wetland System ........ ........................ ... ........ 281 Acceptability and Affordability by Local People ... .... ................. ... 281 Summary . .. ............................................................................... 282 APPENDIX A WATER LEVEL DATA FOR AKUMAL .................................. 284 APPENDIX B NOTES AND TABLES FOR WATER BUDGET SIMULATION MODEL. ............................................................ .... 304 APPENDIX C COMPARISON WITH UNIVERSITY OF FLORIDA SEWAGE TREATMENT FACILITY ... ....... .................................... .314 REFERENCES ..................................................................................... 319 BIOGRAPHICAL SKETCH ............. ..................................................... .... 330 vii

PAGE 9

TABLES Table 2-1 Transformities values used in emergy evaluations in this study .......... .. ..... 52 Table 3-1. Plant species in the treatment wetlands from surveys of May 1997 December 1997 and July 1998. Total number of species as of May 1997 : 68 species ; as of December 1997: 70 species as of July 1998 : 66 species .. . ........ ... . 66 Table 3-2 Species list: mangrove wetland ecosystem 8 December 1997 Species identified by Edgar Cabrera Chetumal Q R ......... ....................... 78 Table 3-3 Species list of inland forest near Akumal Q.R. 9 December 1997. Species identified by Edgar Cabrera Chetumal, Q R .......... . ... ................. 79 Table 3-4 Shannon diversity indices for constructed wetland systems based on May 1997 December 1997 and July 1998 surveys ............................... 82 Table 3-5 Comparison of Shannon diversity indices for constructed wetlands vs natural mangrove and tropical forest ecosystems of the study area based on December 1997 and July 1998 survey data ........................... 83 Table 3-6 Relative cover in the wetland system cells based on 0.25 sq m quadrant analysis May 1997 ........... .................................................. 84 Table 3-7 Estimates of area coverage including canopy of dominant plants in the wetland treatment cells May 1997 Total area of each cell in system 1 is 25.3 square meters and area of each cell in system 2 is 40 6 square meters .. .................. 85 Table 3-8 Estimates of area coverage including canopy of dominant plants in the wetland treatment cells December 1997 and July 1998 Total area of each cell in system 1 is 25 3 square meters, and area of each cell in system 2 is 40 6 square meters . . ......................................... ..... 86 Table 3-9 Frequency rankings of dominant plants in constructed wetlands in May 1997 December 1997 and July 1998 transects ............................ 89 Table 3-10. Importance value ranking of top eight species in each wetland treatment cell May 1997 December 1997 and July 1998 surveys Values were computed by adding relative species frequency and relative species cover and dividing by 2 Maximum value i s therefore 1.0 and total is 1.0 summing all species found viii

PAGE 10

in the treatment cell .............................................................................. 94 Table 3-11 Measurements of leaf area index in the treatment cells of the wetland systems May 1997 December 1997 and July 1998 Values are given with standard error of the mean ................................. ....................... 101 Table 3-12 Leaf holes in the wetland treatment units December 1997 ................... 106 Table 3-13 Leaf holes in the wetland treatment units July 1998 data ..................... 108 Table 3-14. Outside solar insolation levels and their reduction in the constructed wetlands 28 July 1998 between 1050 and 1145 AM. Perimeter light lev els are the measured insolation at locations 0 5 m inside the wetland systems along their outside edges ........................... ................. 113 Table 3-15 Light penetration and canopy closure in the wetland systems and adjoining mangrove wetland 29 July 1998 Data presented standard error of the mean ........................................... ............................................ 115. Table 3-16 Total phosphorus content of water samples from cenote (groundwater well ) near wetland treatment systems ................................... ... 1 20 Table 3-17 Total phosphorus in effluent from septic tank and discharge effluent from wetland treatment systems and percent reduction of phosphorus levels ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 121 Table 3-18 Total phosphorus content of water samples from the treatment wetlands .............................................................................. 1 22 Table 3-19 Total nitrogen in effluent from septic tank and discharge effiuent from wetland treatment systems and percent reduction of nitrogen levels ........... .... 1 26 Table 3 20 Total nitrogen content of water samples from cenote (groundwater well ) near wetland treatment systems ............ ... ... ....................... 127 Table 3-21 Biochemical oxygen demand (BOD-5 ) in effluent from septic tank and discharge effiuent from wetland treatment systems and percent reduction .................................................................... ...................... 131 Table 3-22 Biochemical oxygen demand (BOD-5) content of water samples from cenote (groundwater well) near wetland treatment systems ............... 132 Table 3-23 Total suspended solids (TSS) concentrations and reduction in septic tank and discharge water from the Akumal wetland treatment systems .......... 1 33 ix

PAGE 11

Table 3-24 Total suspended solids (TSS) concentrations in water samples from cenote (groundwater well) near wetland treatment systems ......................... 134 Table 3-25 Alkalinity in septic tanks wetland systems and cenote ...... .................. 138 Table 3-26 Salinity in septic tanks wetland systems and cenote ........................... 139 Table 3-27 Coliform bacteria concentrations in effluent from septic tank and discharge effluent from wetland treatment systems and percent reduction. Data is in units of most probable number of colonies per 100 ml (MPN/ 100 ml) ............ 143 Table 3-28 Coliform bacteria concentrations in water samples from cenote (groundwater well ) near wetland treatment systems. Data is in units of most probable number of colonies per 100 ml (MPN/ 100 ml) ...... .. ................. 1 44 Table 3-29 Ca/Mg composition of Yucatan limestone as analyzed by inductive coupled plasma spectroscopy ........ ....................................... ................ .. 14 5 Table 3-30 Inorganic phosphorus content oflimestone samples ........................... .147 Table 3-31 Results from experiments on limestone uptake of phosphorus ..... .......... 150 Table 3-32 Daily water budget of wetland treatment systems May 1997 ... ........... .. 1 54 Table 3-33 Daily water budget of wetland treatment systems December 1997 ......... 1 55 Table 3-34 Purchased materials and services used in construction of wetland systems Akumal Mexico Costs are expressed in Mexican pesos(1996) and converted to U.S. dollars at the rate of7. 8 peso / $ which was the exchange rate in 1996 when systems were built. ........ ...... ........................................... 159 Table 3-35 Purchased materials and services used in construction of package plant sewage treatment system Akumal Mexico Costs are expressed in Mexican pesos (1996 ) and converted to U.S. dollars at the rate of7. 8 peso / $ which was the exchange rate in 1996 when systems were built. ... ..................... .. 160 Table 3-36 Emergy analysis of the constructed limestone sewage wetlands ...... .. . . 1 62 Table 3-37 Emergy analysis of the package plant sewage treatment system ............. 171 Table 3-38 Wet weigh t/ dry weight of soils in mangrove receiving wetland December 1997 ................................................................................... 177 Table 3-39 Bulk density of soils in mangrove receiving wetland December 1997 ..... 1 78 X

PAGE 12

Table 3-40 Organic matter content of soils in mangrove receiving wetland estimated from loss on ignition and mean values of the five soil samples from December 1997 .................................... ... ... .............................. .... 179 Table 3-41 Calcium and magnesium content of mangrove soil ash after combustion for organic content. Results determined by inductive coupled plasma spectroscopy ... 181 Table 3-42 Total Kejdahl nitrogen content of soils in mangrove receiving wetland on 12 December 1997 before discharge of treated effluent ...... . ............. 185 Table 3-43 Total Kejdahl nitrogen content of soils in mangrove receiving wetland before discharge (30 April 1998) and 2 months (3 July 1998) 3 months (3 August 1998) and 4 months (2 September 1998) after discharge of treated effluent began 3 May 1998 ................................ ............ 186 Table 3-44 Phosphorus content of soils in mangrove receiving wetland on 12 December 1997 before discharge of treated effluent.. .............................. 187 Table 3-45 Phosphorus content of soils in mangrove receiving wetland before and after discharge began 3 May 1998 ..... ... . ....................... . ... ........ 188 Table 3-46 Total nitrogen in water of mangroves before and after discharge of treated wastewater. ........................................... . ........................ . . 198 Table 3-47 Soluble reactive phosphorus (SRP) in water of mangroves before and after discharge of treated wastewater ... . . . . . . . . . . . . . . . . . . . .200 Table 3-48 Chemical oxygen demand (COD) in water of mangrove receiving wetland before and after discharge of treated wastewater ................................. 201 Table 3-49 Total suspended solids (TSS) in water of mangroves before and after discharge of treated wastewater.. .......................................... 202 Table 3-50 Coliform bacteria in water of mangroves in 1998 after discharge of treated effluent.. ................................................................. .204 Table 3-51. Salinity in mangrove water in December 1997 before discharge of sewage effluent .................................................................... 205 Table 3-52 Salinity in mangroves in 1998. Discharge of treated effluent began May 1998 ............................. .......................................... 207 Table 3-53 Computer program in BASIC for simulation model of water budget in treatment wetland nit. .............. ................................................ .21 O xi

PAGE 13

page Table 3-54 Spreadsheet for calculation of coefficients in water budget simulation model of treatment units and mangroves ........ ............................... 212 Table 3-55 Emergy evaluation table of one square kilometer of developed coastline Akumal Mexico (see Figure 3-58) .............................. . ............... .221 Table 3-56 Emergy indices for evaluating one square kilometer of developed coastline Akumal, Mexico ....................................... ................. 227 Table 3-57 Water budget of a square kilometer of coastline around research site without use of wetland treatment systems .... ........ .... ............... ... 231 Table 3-58 Comparative additions to groundwater (GW) of nitrogen phosphorus BOD ( organic compounds) and fecal coliform in a 1-square kilometer area of study site with and without the use of wetland treatment systems .............. ... ...................... . ....................................... 235 Table 3-59 Phosphorus budget of a developed square kilometer of coastline Akumal Mexico, with no sewage treatment and changes if wetland systems are installed ................................... . .............................. 237 Table 3-60 Nitrogen budget of a developed square kilometer of coastline Akumal Mexico with no sewage treatment and changes if wetland systems are installed ............... ................................................ .... 240 Table 3-61 Organic compounds (BOD) budget of a developed square kilometer of coastline, Akumal Mexico, with no sewage treatment and changes if wetland systems are installed ..................... ...... ... .... .. ................ 243 Table 3-62 Coliform bacteria budget of a developed square kilometer of coastline Akumal Mexico with no sewage treatment and changes if wetland systems are installed .................................................................. 245 Table 4-1 Comparison of loading rates and removal efficiency of Akumal treatment wetland units with average North American surface and subsurface flow wetlands (Kadlec and Knight 1996) .................................................... 255 Table 4-2 Comparison of emergy indices for Akumal treatment units package plant at Akumal and the University of Florida wastewater treatment system ( compiled from data in Tables 3-36 3-38 and Appendix) ............ 257 Table 4-3 Program in BASIC for simulation model of interactions between natural environment and human economy along the Yucatan coast ............... ..... . 273 xii

PAGE 14

Table B-1 Average monthly rainfall at Tulum 20 km south of study site ............... 308 Table B-2 Measured evaporation at Tulum 20 km south of study site along the Yucatan coast. Actual evapotranspiration is estimated at 900 mm for the Yucatan. The last column is a calculation of evapotranspiration based on the percentage of yearly evaporation that occurs in each month .............. 309 Table B-3 Average monthly relative humidity temperature, and air vapor pressure calculated for the given temperature and relative humidity for the Yucatan coast. . ... ..................................... .. ............................... 310 Table B-4 Average wind velocity measured at Puerto Moreles Mexico 80 km north of study site ........ ...... .. ...... ....................... .......................... 311 Table B-5 Estimates of monthly groundwater flow based on data from Back (1985) and average monthly rainfall in the Yucatan ................................. .312 Table B-6 Net primary productivity in mangrove ecosystems .............................. 313 Table C-1 Emergy analysis of the University ofFlorida sewage treatment facility ...... ........................................................ ................. . 316 Xlll

PAGE 15

FIGURES Figure 1-1 Map of eastern Yucatan Peninsula of Mexico showing coastal area of study around Akumal Quintana Roo north of Tulum ..... ......................... 11 Figure 1-2 Geological cross-section in study area showing flow and mixing of fresh groundwater and seawater (Shaw, in press) ............................ ............. 12 Figure 1-3 Map of study area a ) shows collapse zones and areas of ancient bays (larger black dots) b) shows areas of groundwater discharge along the coast and sampling points. In both diagrams modem reef is indicated by light dots offshore (Shaw, in press) .... ........................................................ 14 Figure 1-4 Salinity contours in Akumal during a period of no rain Contours are compressed on the highly porous and permeable limestone At the 20% contour mixing of saltwater and freshwater below ground surface makes the gradients steeper (Shaw, 1997) ............................................ 15 Figure 1-5 Salinity contours in Akumal area after a heavy rain Compared to Figure 1-4, salinity gradient is displaced inland due to dilution by rain and groundwater flow (Shaw, 1997) ........................................................... .16 Figure 1-6 Map of study area showing groundwater flow in relation to porous limestone rock (indicated by crosses) and coliform contours from studies conducted in May-August 1997 (Shaw, in press) .................................... 17 Figure 1-7 Aerial photograph of study area, Akumal Quintana Roo, Mexico ........................................................................................... ... 20 Figure 1-8 Study area around Akumal Mexico showing location of the wetland systems at A ", enlarged in Figure 1-9 Contour lines in meters (Shaw, in press ) ....... 21 Figure 1-9 Enlarged sketch of area A in Figure 1-8 showing location of wetland treatment areas and mangrove where treated effluent was discharged. Points labeled A to E are mangrove sampling stations ... .. .................................. 22 Figure 1-10 Systems diagram showing the wetland treatment unit within the context of the coastal zone economy and ecology .................. ... ................... 25 xiv

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Figure 2-1 Schematic of wetland treatment system showing flow from houses to septic tanks to wetlands ....... ...................................................... .33 Figure 3-1 Construction blueprint: isometric view of the wetland treatment system ............ ................................................ ... ......... ... . ... ......... ..... 55 Figure 3-2 Construction blueprint: isometric view of piping in the wetland system .......................................... ................. .. .......... ... .... ............ 56 Figure 3-3 Construction blueprint: center section view of the wetland system .............................. ... ..... ...... .......................... .................. . ... . 57 Figure 3-4 Construction blueprint: side section showing fill materials in the wetland system ........................................... ................................ .. . 5 8 Figure 3-5 Construction blueprint: control box with dimensions of the wetland treatment cells ........... ........ . .................................................... 59 Figure 3-6 Construction blueprint: treatment cell 1 header detail of the wetlands ......... ................................................................................. 60 Figure 37 Construction blueprint: treatment cell 2 header detail of the wetlands .................................................. .......................................... 61 Figure 3-8 Construction blueprint: schematic showing drainfield detail for large wetland systems .................................. ......... .. ......................... ... 62 Figure 3-9 Construction blueprint: schematic showing drainfield detail for small wetland systems ........ .... ............................... ................................. 63 Figure 3-10 Construction blueprint: drainfield cross-section drawing of wetland system ........................................................... .......................... 64 Figure 3-11 Species-area curves for each of the four wetland treatment cells, May 1997 data ...... .................................................................. ...... 70 Figure 3-12 Species-area curves for each of the four wetland treatment cells December 1997 data ................ .. ................................ ... .................. 71 Figure 3-13 Species-area curves for each of the four wetland treatment cells July 1998 data .. ........................................................................ .... 72 Figure 3-14 Species-area curves for the 50 6 m2 wetland unit ( system 1 ) and the 81.2 m2 wetland (system 2) May 1997 Transects counted 482 xv

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individuals in each system .................................................................... .. 73 Figure 3-15 Spec i es-area curves for the 50 6 m2 Yucatan wetland (system 1 ) and the 81.2 m2 wetland ( system 2) December 1997 Transects counted 500 individuals in each system ..................................................... ... 75 Figure 3-16 Species-area curves for the 50 6 m2 Yucatan wetland ( system 1 ) and the 81.2 m2 wetland ( system 2 ), Jul y 1998 Transects counted 500 indi v iduals in each system ....................................................... 76 Figure 3-17 Comparison of species richness between treatment wetlands mangrove wetland and forest ecosystems December 1997. Transects were 1000 individuals from each system ............................................................. 77 Figure 3-18 Comparison of species richness between mangrove forest and each treatment wetland. Transects counted 1000 individuals in mangrove and forest and 500 each in wetland systems 1 and 2 ......................................... 80 Figure 3-19 Plant species in rank sequence of i mportance value ( IV) in the four wetland treatment cells May 1997 data Importance value = ( frequency + cover )/ 2 ............................................................................. 97 Figure 3-20 Plant species in rank sequence of importance value ( IV ) in the four wetland treatment cells December 1997 data Importance value = ( frequency+ cover )/ 2 ............................ ..... .................................. 98 Figure 3-21 Plant species in rank sequence of importance value (IV) in the four wetland treatment cells July 1998 data Importance value = ( frequency + cover )/ 2 ............................ ....................... .......................... 99 Figure 3-22 Photograph of wetland systems in Akumal shortly after planting August 1996 System 1 is in foreground and System 2 in background in front of edge of mangrove wetland .............. . . ..... .................. 102 Figure 3-23 Photograph of vegetation in wetland system 1 May 1997 ................... 103 F igure 3-24 Photograph of vegetation in wetland system 1 December 1997 ... .......... 1 04 F igure 3-25 Photograph of vegetation in wetland system 1 July 1998 ................... 105 Figure 3-26 Surface organic matter in the wetland treatment cells Data presented are those of initial mulching (August 1996) and surface organic matter (July 1998 ) after 23 months of operation Bars are standard errors ............ 1 1 1 XV1

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Figure 3-27 Photograph showing dense canopy cover intercepting solar insolation wetland system 2 July 1998 ............................. ................... . . 114 Figure 3-28 An example of canopy-cover photograph using fish-eye lens July 1998 . . .................................................................................... ... 116 Figure 3-29 Total phosphorus (TP) analyses of water samples from wetland treatment system 1 . .............................. .... ....................... ........ 118 Figure 3-30 Total phosphorus (TP ) analyses of water samples from wetland treatment system 2 .............................. ................................ .. ... 119 Figure 3-31 Total nitrogen ( TN) analyses of water samples from wetland treatment system 1 ......................................................... ...................... 1 24 Figure 3-32 Total nitrogen (TN) analyses of water samples from wetland treatment system 2 ...... ......... ................................. . ......... . ................ 125 Figure 3-33 Biochemical oxygen demand (BOD5 ) in wetland system 1 water samples .. .. ...... ................. . ............................ ........... ... ....... . 129 Figure 3-34 Biochemical oxygen demand (BOD5 ) in wetland system 2 water samples ........................................ .. ........................................... 130 Figure 3-35 Total suspended solids (TSS) in water samples from wetland system 1 ......................................... ........................... ............... ........ 135 Figure 3-36 Total suspended solids (TSS) in water samples from wetland system 2 ............ .. .. ...................................... ... .. ............ ................ 1 36 Figure 3-37 Fecal coliform bacteria in water samples from wetland system 1 Data plotted on log scale and units are most probable number (MPN) of bacterial colonies per 100 ml.. .................................................... 141 Figure 3-38 Fecal coliform in water samples from wetland system 2. Data plotted on log scale and units are most probable number (MPN) of bacterial colonies per 100 ml.. ..... ...... ..... ... .. . .. ...................... ............ .. .. 142 Figure 3-39 Estimates of monthly flows of phosphorus during first year of wetland treatment system operations (1997) Data from both wetland systems are combined .............. ... .......................................................... 148 Figure 3-40 Graphs with results of experiments on limestone uptake of phosphorus .. . ................................................. ................................. 152 XVll

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Figure 3-41 Diagram of emergy and money flows in wetland treatment systems Akumal Mexico. Units of diagram are El5 sej/yr .. ........ .. .. ........ . . . ... 172 Figure 3-42 Diagram of emergy and money flows in the package plant sewage treatment system Akumal Mexico Units of diagram are El5 sej / yr .................................................................. .. ...................... 180 Figure 3-43 Howard T. Odum inspecting root penetration and peat depth in mangroves Akumal December 1997 ...................................................... 182 Figure 3-44 Thickness of mangrove peat in the receiving wetland around the outfall pipe discharging effiuent December 1997 See Figures 1-9 for location of mangrove discharge point in Akumal. Mangrove soil samples were collected 1 3 5 and 10 m from discharge point in N S E and W directions (Tables 3-43 and 3-45) Water samples were collected at lm upstream (A) lm (B) 3m (C) and 6m (D) downstream and 15m (E ) SE of discharge point ( see Figure 1-10 ) ...................... 183 Figure 3-45 Systems diagram of the mangrove wetland receiving treated effiuent. ............................................................................................ 190 Figure 3-46 Potentiometric measurements of groundwater level in mangroves December 1997 Piezometers were located at A,B and C Survey transit level was located at point D Flowlines calculated from data are approximately in easterly direction .................................................. 191 Figure 3-47 Chart recorder water levels in cenote near wetland systems 27-28 May 1997 ................................................................... .. ............. 193 Figure 3-48 Chart recorder water levels at Yal-ku lagoon showing tidal record 27-28 May 1997 ........................................................................ 194 Figure 3-49 Chart recorder water levels in mangrove receiving wetland 9-14 December 1997 ............................................................................. 1 95 Figure 3-50 Chart recorder water levels in cenote near wetland systems 10-14 December 1997 ........ ........................ ...................................... .. 196 Figure 3-51 Chart recorder water levels at Yal-ku lagoon showing tidal record 10-14 December 1997 .................................................................. 197 Figure 3-52 Systems diagram for simulation model of water budgets of treatment unit and receiving wetland showing difference equations .................... 208 xviii

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Figure 3-53 Systems diagram showing steady state storages and pathway flows for water budget simulation model of treatment units and mangroves ........... .209 Figure 3-54 Computer simulation of the water budgets of treatment units and mangroves ............................................................................. 215 Figure 3-55 Simulation of water budget for wetland treatment unit and mangroves with increase of wastewater loading (10 times higher) Scale: sunlight 5000 Kcal/m2/ day biomass 20 kg/m2 water levels 1.5 m water inflows lm/day ..................................... ....................................... 216 Figure 3-56 Simulation of water budget for wetland treatment unit and mangroves with loss of groundwater inflow Scale: sunlight 5000 Kcal/m2/ day biomass 20 kg/m2 water levels 1.5 m water inflows lm/day .............................................................. ......... ... ................. 217 Figure 3-57 Simulation of water budget for wetland treatment unit and mangroves with hurricane event at year 5 Scale : sunlight 5000 Kcal/m2/ day biomass 20 kg/m2 water levels 1.5 m water inflows Im/day ......................... ... 218 Figure 3-58 Map of Akumal Mexico showing the I-square-kilometer coastal study area ................................................................................ 220 Figure 3-59 Systems diagram of the square kilometer coastal economy and environment labeled with emergy flows in El 8 sej/yr from Table 3-57 ................ 226 Figure 3-60 Diagram of emergy and money flows in the I-square-kilometer coastal area Akumal Mexico Units of diagram are expressed in E18 sej (solar emergy joules) / yr ............................................................ 228 Figure 3-61 Diagram of water budget of one square kilometer of developed coastline Akumal Mexico. Figures in parentheses show changes in budget if all sewage is treated by constructed limestone wetlands ........ ............ 233 Figure 3 62 Diagram of phosphorus budget of one square kilometer of developed coastline Akumal Mexico Figures in parentheses show changes in budget if all sewage is treated by constructed limestone wetlands and receiving wetlands ...................................... ............ ............................. 239 Figure 3-63 Diagram of nitrogen budget of one square kilometer of developed coastline Akumal Mexico Figures in parentheses show changes in budget if all sewage is treated by constructed limestone wetlands and receiving wetlands .............................................................. 242 XIX

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Figure 3-64 Diagram of organic matter (BOD) budget of one square kilometer of developed coastline, Akumal Mexico. Figures in parentheses show changes in budget if all sewage is treated by constructed limestone wetlands and receiving wetlands ........... ............................................. ..... 244 Figure 3-65 Diagram of coliform bacteria budget of one square kilometer of developed coastline Akumal Mexico. Figures in parentheses show changes in budget if all sewage is treated by constructed limestone wetlands and receiving wetlands ........................ ............................... ...... 246 Figure 4-1. Diagram showing annual emdollar contributions to the constructed wetland system in Akumal Mexico ...... ... .................................. .258 Figure 4-2 Systems diagram and difference equations used for simulation model of the interactions between the natural environment and the human economy along the Yucatan coastline ........................................................ .270 Figure 4-3. Systems diagram for Yucatan coastal model. Values shown are steady-state storages and flows between components .................. .. ............ .271 Figure 4-4 Computer simulation of the Yucatan coastal model. The legend gives the full scale values of the ordinate for each quantity ... .................... 272 Figure 4-5 Simulation runs of the interaction of the environment and human economy in the Yucatan. a/ Impact of starting with nitrogen at ten times higher value b / Impact of starting with coral at zero c / Impact of starting with money and assets at 1/10 value ...................................................... .. ................. .275 Figure A-1 Water level record for cenote near wetland treatment unit 27-28 May 1997 ................................................................................. 285 Figure A-2 Water level record for cenote near wetland treatment unit 28-29 May 1997 ........... .. .................................................................... 286 Figure A-3 Water level record for cenote near wetland treatment unit, 29-30 May 1997 .................................................................................. 287 Figure A-4 Water level record for cenote near wetland treatment unit 30-31 May 1997 .................................................................................. 288 Figure A-5 Water level record of tidal heights at Yal-Ku Lagoon, 27-28 May 1997 ... 289 Figure A-6 Water level record of tidal heights at Yal-Ku Lagoon 13-16 December 1997 ... .......................................................................... 290 xx

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Figure A-7 Water level record of tidal heights at Yal-Ku Lagoon 16-17 December 1997 ............................................................................ 291 Figure A-8 Water level record of tidal heights at Yal-Ku Lagoon 17-19 December 1997 .......................................................................... 292 Figure A-9 Water level record of tidal heights at Yal-Ku Lagoon 19-22 December 1997 ........................................................................ ... 293 Figure A-10 Water level record for cenote near wetland treatment unit 10-14 December 1997 ......................................................................... .. 294 Figure A-11 Water level record for cenote near wetland treatment unit 14-17 December 1997 .................................................... ....................... 295 Figure A-12 Water level record for cenote near wetland treatment unit 17-20 December 1997 ............................................. ...... ................... ..... 296 Figure A-13 Water level record for mangrove near wetland treatment unit 9-14 December 1997 ............................................................................. 297 Figure A-14 Water level record for mangrove near wetland treatment unit 14-17 December 1997 .. ......................................................................... 298 Figure A-15 Water level record for mangrove near wetland treatment unit 17-20 December 1997 ........................................................................... 299 Figure A-16 Water level record for mangrove near wetland treatment unit 18-21 July 1997 ................................................................................... 300 Figure A-17 Water level record for mangrove near wetland treatment unit 22-25 July 1997 ......... .......................................................................... 301 Figure A-18 Water level record for mangrove near wetland treatment unit,. 25-28 July 1997 ................................................................................... 302 Figure A-19 Water level record of tidal heights at Yal-Ku Lagoon, 24 July-1 August 1997 ......................................... ................................ 303 XXI

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Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy LIMESTONE WETLAND MESOCOSM FOR RECYCLING SALINE WASTEWATER IN COASTAL YUCATAN, MEXICO Chairman : Howard T. Odum By Mark Nelson December 1998 Major Department: Environmental Engineering Sciences To understand wetland self-organization and to prevent pollution of groundwater and coral reef on the calcareous east coast of Yucatan Mexico a wetland mesocosm system was developed for treatment and recycle of saline septic-tank wastewater. High diversity wetland ecosystems were developed in two concrete-lined chambers, using subsurface flow through limestone gravel arranged in series with discharge to backbeach mangroves. Evapotranspiration in the wetlands averaged 35% of design influent during summer months and 20% during winter months. Tall wetland vegetation developed with 66 plant species in 131 m2 Shannon diversity of vegetation was 5 .01 (logarithm base 2), far greater than that of the mangrove wetland (1.49), but less than the inland Yucatan forest (5.35) Leaf area index increased over 13 months from 3.96 0.28 to 6.05 0.49 xxii

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In wastewater passing through the systems, biochemical oxygen demand was reduced 85% suspended solids 40% phosphorus 78% and nitrogen 75% Coliform bacteria were reduced 99 8 +%. Limestone gravel in the treatment system removed 5 75 1.68 mg/kg phosphorus per year. Nutrients in mangrove water and soil sediments increased 5-10% from discharge of treated wastewater. Water budgets in treatment system and mangrove were studied with simulation model. On a per-capita basis the wetland systems for 40 people cost approximately $160 per person to construct vs over $400 for alternative treatment technologies Operation and maintenance costs were 10% that of conventional treatment. Emergy in purchased inputs for construction were less than 1 / 3 of free environmental inputs ; empower density was 2.5 E19 sej/ha/yr (one third that of conventional treatment) The potential for economic development using the new treatment systems was evaluated. Treatment systems would require 0 3% of the annual monetary flow (vs. 1.1 % for conventional sewage treatment) and 2.4% of total emergy while contributing 71, 000 emdollars (the monetary equivalent of useful work contributed by nature and by humans) The new systems conserve mangroves reduce eutrophication, prevent pollution of groundwater, protect marine resources and contribute aesthetic values Research results indicate high biodiversity can be achieved in sewage treatment wetlands, use of limestone gravel augments phosphorus uptake and such systems can be integrated into the larger environmental setting xxiii

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CHAPTER 1 INTRODUCTION 1 A central question in ecological engineering is how to organize the hydrological cycle of the human economy symbiotically with that of the supporting ecosystems and geological substrate so as to maximize their joint performance. This dissertation reports the development and evaluation of an ecologically engineered wastewater interface between saline municipal wastewater and a tropical coastal zone with limestone substrate, mangrove wetlands tourist beaches and coral reefs Potential for this wetland system was evaluated by estimating its role in the water, nutrient, and emergy budgets of the emerging coastal economy To achieve the performance observed in ecosystems in nature, an ecologi cally engineered system may need to be coupled to the geological setting and cycles as organized with groundwater. This project uses a human-assisted self-organization and structure to innovate a union of wastewater treatment with the larger ecosystem context Ecological engineering seeks a symbiotic mix of man-made and ecological self design that maximizes productive work of the entire system (including the human economy and the larger-scale environmental system). Allowing this process to self organize may develop better adapted ecosystems that prevail because of their greater empower (Odum 1991) By such minimal human manipulation and management, 1

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2 materials are recycled efficiency is enhanced costs are reduced and ecological processes contribute more An important application of ecological engineering is the design of interface ecosystems to handle byproducts of the human economy and to maximfae the performance of both the human economy and natural ecosystems (Mitsch and Jorgensen, 1991). Scientific Questions in Ecological Engineering of Wastewater Treatment and release of wastewater from coastal development in Quintana Roo in the Yucatan Peninsula of Mexico involve new scientific questions .. Wastewater Interface Ecosystems in the Tropics Tropical coastlines have dry and wet season properties frequent hurricanes and high temperatures y ear-round There has been increasing interest in using wetlands as interface ecosystems for wastewater treatment since early studies demonstrated their effectiveness at removal of nutrients and suspended solids These included use of cypress swamps in Florida ( Odum et al. 1977 ; Ewel and Odum, 1984) and peatlands in northern Michigan (Kadlec 1979). Constructed wetlands using surface-flow or subsurface flow emergent vegetation or aquatic plant systems have gained increasing acceptance (Hammer 1989 ; Mitsch and Gosselink, 1993 ; Reed et al 1995). Since such natural or constructed wetlands are often limited by solar insolation and show increased rates of uptake in warmer climates such systems may be expected to operate even more efficiently in tropical regions In addition, wastewater interface ecosystems may benefit from the high species diversity found in tropical regions since diversity at the biotic and metabolic level increases the efficiency

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3 of ecosystems (Jorgensen and Mitsch 1991) Plant diversity may benefit wastewater treatment by prov i ding 1 / greater variety of root systems allowing for greater penetration of the limestone gravel and supporting a wider range of associated microorganisms ; 2 / differing metabolic needs ( e.g nutrient uptake) may lead to greater capacity for absorbing wastewater constituents ; 3 / differing seasonal cycles of activity which may increase plant productivity year-round ; 4 / greater ability to utilize the full spectrum of incident solar radiation by the inclusion of shade-tolerant as well as top canopy species and 5 / differing specialist capabilities ( e .g. C3 and C 4 photosynthetic pathways or quantity of aerenchyma tissue in saturated conditions) allowing for greater system response to changing environmental conditions such as light heat and nutrient levels Greater diversity also buffers against system failure should disease or herbivory decimate selected plant species in the constructed wetland There is evidence that allowing self organization to develop cooperative mechanisms enhances the ability of adapted ecosystems to handle pollution and toxicity (Odum 1991) Wastewater Interactions in Landscapes with Soil Substrate of Limestone Landscapes on limestone platforms offer special challenges and opportunities for ecologically engineered wastewater treatment. Calcium carbonate the predominant mineral compound, has the ability to react with phosphorus and thus offers the potential for enhanced nutrient retention On the other hand such karstic landscapes are characterized frequently by relatively poor or shallow soil depth In addition the presence of rock such as limestone which is dissolved by water at ground surface permits rapid infiltration and lateral movement of wastewater (Bogli 1980 ; Milanovic 1981).

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4 Studies in similar subtropical and tropical limestone coastlines ( e g the Florida Keys and Caribbean islands such as Jamaica) have indicated that they are especially susceptible to eutrophication through flow of septic tank effluent through porous calcareous strata since retention time does not allow for sufficient plant uptake or microbial decomposition (Bright et al 1981 ; Pastorok and Bil yard 1985 ) Salty Wastewater Wastewater with appreciable salt content has only rarely been studied in sewage treatment. It is an especially important vector in ecologically engineered wetland treatment systems as salinity is frequently a controlling factor in determining the types of organisms that will best self-organize such systems In addition salinity is important in coastal regions as groundwater salinity varies depending on factors such as tidal interchange rainfall and evapotranspiration. Saltwater ecosystems such as estuaries mangrove and salt marsh are amongst the world s most productive (Day et al 1989). Previous work with mangroves (Sell 1977) and with marine ponds receiving treated sewage have demonstrated their treatment effectiveness and capacity to self-organize to the input of eutrophic wastewater (Odum 1985). Using Small-Scale Mesocosm Tests to Evaluate Regional Potentials The two small constructed wetlands (total area 130 m2 ) evaluated in this research may be viewed as a mesocosm study of the impact of such interface ecosystems if more widely applied to the coastal regions of karstic tropical countries A growing body of literature has demonstrated the applicability of such mesocosm studies to evaluate processes and potentials at higher spatial and energetic levels (Beyers and Odum 1993). Frequently distinctive patterns of self-organization result from interface mesocosms

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5 exposed to extreme forcing functions such as high nutrient and hydrological subsidies ( Odum 1991) that can then be evaluated for scaling-up and application at regional levels Problems of Fitting Water Systems to the Landscape Unique Characteristics of Tropical Coastal Development Over half the world s population live along coasts and adjoining rivers and the rate of population increase in coastal areas exceeds those of inland regions (NRC 1995) Especially in tropical developing countries such issues have gained increasing attention due to recent accelerated growth of tourism and land development exploitation of natural resources and the vulnerability of marine ecosystems such as coral reefs and coastal ecosystems such as mangrove wetlands to the effects of pollution and eutrophication ( U.N., 1995). At present lack of effective and affordable means of sewage disposal is widespread through the tropical developing world This leads to chronic disease through human contact with polluted water and environmental damage to sensitive ecosystems Coastal tourist development has been pursued by some developing tropical countries as a method of economic progress utilizing their resources of warm climates beautiful beaches and eco-tourism if they have attractive marine or terrestrial ecosystems All too frequently this tourist development exacerbates the problems of water contamination by placing large demands on available freshwater adding new permanent and transient populations to an area, and converting land from natural ecosystems Tropical areas are frequently characterized by extremely high biological d i versity The Yucatan, because of its tropical climate and isolation has been able to sustain to date some of the most widespread and undamaged stands of tropical forest. The coastline

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6 around Akumal and th i s portion of the eastern Yucatan coast is an important breeding ground for loggerhead and green sea turtles which come ashore annually to lay their eggs. In areas like the eastern Yucatan the environmental hazard is especially great because of the highly permeable karstic geology and the presence of coral reefs offshore that are particularly sensitive to eutrophication It is critical to not only evaluate current development but to develop ecologically engineered solutions. The subsurface flow constructed wetlands constructed as part of the present research effort in Akumal will be evaluated as one strategy for sustaining water quality both for people and for environmental preservation in tropical coastal regions Eutrophication Impacts on Coral Reefs E conomic development results in the release of nutrients in coastal waters causing replacement of ecosystems such as coral reefs important to tourism T he impact o f nutrients in coastal regions is greater than that of deeper waters because of the interplay between sediments and the water column due to the strong vertical mixing by tidal currents and wind in the shallow water depths (Nixon and Pilson, 1983). Thus coastal regions are unlike deeper oceanic areas where deposited materials are lost to surface ecosystems Thus coral reef ecosystems and other mature ecosystems are dependent on internal nutrient recycling for a large portion of their gross productivity ( Laws 1983 ), new growth requiring added nutrients Nitrogen is sometimes a limiting factor for coral reefs (D 'Elia and Wiebe 1990 ), normally supplied b y zooplankton captured by coral polyps Excessive nutrients displace mature ecosystems with low diversity growths

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7 Thus nutrient retention by the interface ecologically engineered wastewater wetland is an important criterion for maintenance of optimal environmental health at the higher level. A growing body of research indicates that coral reefs and other marine ecosystems such as seagrass can be rapidly degraded due to pollution from inadequately treated sewage Seagrass ecosystems are normally mesotrophic and are vulnerable to shading disease, and excessive epiphytic growth in eutrophied waters (Pastorok and Bilyard 1985). Caribbean coral reefs despite their high gross productivity are adapted to oligotrophic waters where they maintain themselves using high nutrient retention and recycling. Corals are vulnerable to sewage pollution due to the following causes : 1/ stress ; 2 / decrease of available light and dissolved oxygen due to higher rates of sedimentation and enhanced growth of phytoplantkon and other microorganisms in the water column ; 3 / overgrowth and bio-erosion of corals by fleshy macro-algae and benthic filter-feeding invertebrates that outcompete corals in high-nutrient waters; 4 / diseases resulting from bacterial growth stimulated by mucus-production by eutrophied corals ; and 5 / direct chemical toxic effects (Hallock and Schlager 1986 ; Pastorok and Bilyard 1985; Lapointe and Clark, 1992 ; and Hughes, 1994 ). Issues of Human Health Contamination of water resources is one of the leading causes of disease in tropical countries (U.N ., 1995) Coastal areas with their shallower water tables are especially vulnerable to groundwater pollution Water pollution includes pathogens carried by improperly treated sewage and potentially toxic chemicals Pathogens include disease-causing bacteria, protozoa viruses and helminths Chemical hazards include

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8 heavy metals organic chemicals and nitrates in sufficient concentrations to cause illness (Krishnan and Smith 1987) Previous Studies Coral reef deterioration caused by eutrophication was studied in Kaneohe Bay Oahu, Hawaii which received sewage effluent from a treatment plant. In parts of the bay, coral loss stemmed from a buildup of organic matter, causing anaerobic conditions that released hydrogen sulfide, overgrowth from the explosive growth of green bubbly algae (Dictosphaeria cavernosa), sedimentation and loss oflight and competition by filter-feeders in increasingly turbid waters (DiSalvo, 1969 ; Laws, 1983 ; Grigg and Dollar ; 1990). There was a proliferation of filter-feeders that bore into the corals Benthic organisms outcompete water column plankton and filter-feeders in oligotrophic waters but the reverse is true in nutrient-rich conditions (Laws 1983). Previous studies of subsurface flow wetlands for sewage treatment have demonstrated their advantages in situations of small on-site sewage loading in areas where land is scarce or in situations where avoidance of malodor and mosquito-breeding are important (Kadlec and Knight, 1996) These are all the case in Akumal because of the high visibility of the treatment site, the need to create a nuisance-free and aesthetically attractive system and the potential of a well-designed subsurface flow wetland of providing an inexpensive but highly effective degree of sewage treatment. As is the case in the U.S. and Europe where this approach is rapidly spreading the advantages of constructed wetlands are that because they rely on more natural methods, they are less expensive to build and operate than conventional sewage treatment plants (Tchonbanoglous, 1991) Constructed wetlands also can produce a standard of treatment

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9 equivalent to tertiary or advanced wastewater treatment. This is far better than a typical package plant or municipal sewage plant that produces effluent at secondary sewage standards quality requires high capital investment and technical expertise and is ene r gy intensive (Reed et al, 1995) Subsurface wetlands use little or no electricity and technology and require little technical supervision once installed ( Cooper 1992 Steiner and Freeman, 1989 ; Green and Upton 1992 ; Steiner 1992) However there is little prior research with these systems in tropical karstic coastal conditions Wetland systems have long hydraulic residence times and through a variety of mechanisms (sedimentation antibiotics filtration natural die-off etc ) have shown promise in achieving large reductions in coliform bacteria without the use of disinfectants like chlorine used in conventional sewage treatment (Reed et al ., 1995). Chlorine has the potential to fonn toxic byproducts such as chloramine when released into marine environments (Berg 1975). Bacteria can break down chlorinated hydrocarbons into compounds that may be far more dangerous than the original ones ( Gunnerson, 1988) and sometimes de-chlorination has been required by regulatory agencies further adding to the expense of such approaches (Kott 1975) The dynamics of limestone in subsurface flow wetlands is also largely unknown Theory suggests that limestone should increase phosphorus retention since calcium and magnesium are the primary agents of phosphorus fixation in alkaline conditions (Reddy 1997) A previous study with subsurface flow wetlands in Canada examined the efficacy of dolomite [CaMg ( CO3)2] substrate containing 55% CaCO3 The substrate was found to be effective at removal of Pin influent wastewater handling secondary wastewater but when primary wastewater with higher P levels were used, P retention capacity proved

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10 inadequate and P-retention capacity decreased by 77% over 45 months of operation (Reddy 1997) Study Sites in the Yucatan Regional Study Area: Akumal Coastline The research site is the coastal region around Akumal Quintana Roo Mexico (Figure 1-1) about 90 kilometers south of Cancun on the eastern coast of the Yucatan Peninsula and 10 km north of the town and Mayan ruins at Tulum Like many tropical coastlines the eastern Yucatan is underlain by permeable limestone that in a kilometer wide area adjacent to the coast is believed to be the remains of Pleistocene coral reef communities (Shaw in press). The hydrogeology of the coastal region around our study site in Mexico was studied during the 1960s and 1970s (Ward and Weidie 1976 ; Ward et al 1985 ), and water budgets for the region were developed by Lesser ( 1976). In the northern third of the Yucatan (which includes the study site at Akumal ), maximum elevation i s about 40 m though most of the land surface is in a very flat plain of rough pitted terrain caused by weathering of the very permeable limestone which is exposed over most of the surface Because of the general absence of other sediments or soil no surface drainage system exists. Cenotes (sinkholes) are the main bodies of fresh water and almost all water movement is subsurface through the fractured limestone Shaw (i n press) has described the area s geologic profile and how the modem topographic features have been derived from their Pleistocene predecessors (F igure 1-2 ) About one kilometer inland is an Upper Pleistocene ( Sangamon ) beach ridge with a maximum elevation of 8 m which is segmented by triangular spits that extend up to 750 m towards the sea Modem, sandy rounded bays have been formed by Holocene flooding

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11 0 ulf of1'J1e~C G \ 20Km. Scale Figure 1-1 Map of eastern Yucatan Peninsula of Mexico showing coastal area of study around Akumal Quintana Roo north of Tulum.

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10 5 0 -5 I 0 Ancient beach Younger limestone belt : Lagoon Mangrove and Karst Zone Cenote Core holes I Brackish water exits Brackish water r Impermeable layer: --~~.,c~~===~~E::=:=:~~~~~--! Mixing dissolution Older limestone Freshwater Sea water enters f-'igure 1-2 Geological cross-section in study area showing flow and mixing of fresh groundwater and seawater ( Shaw, ;;n_, press) 0 200m I I -N

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13 of the Pleistocene ones Behind the headlands several hundred meters is a mixing zone where the mix of fresh and saltwater have led to dissolution of limestone the collapse creating lagoons such as Yal-Ku in Akumal (Figure 1-3) While this collapse has been attributed solely to the CaC03 solution kinetics in the mixing zone (Back et al 1979 ), this area is associated with mangrove wetlands and biological activity may have been at least partly responsible for the limestone dissolution (Odum pers. c omm .) Akumal which attracts tourists for its beaches diving and snorkeling has experienced growth from dozens of permanent residents in 1970 to around 500 currently with yearly tourist stays in the tens of thousands of days. There is evidence from water quality monitoring done by the Centro Ecologico Akumal (CEA) that there is growing pollution of the terrestrial and marine environments Shaw (1997) has documented a pollution plume in Akumal as high as 2000 coliform colonies / 100 ml in groundwater The finding of pollution correlates with the movement of this water through reef rock of high porosity and permeability ( Figures 1-4 1-5 1-6 ) This pollution poses dangers both for people due to contamination of groundwater supplies and recreational contact with improperly treated sewage and for natural ecosystems such as the coral reef system offshore Pollution and beach development also are of concern in the study area because the coastline around Akumal is an important breeding ground for leatherback and green sea turtles which come ashore annually to lay their eggs Growth and Development in the Yucatan The rapid growth of the Yucatan Peninsula as an international and Mexican tourist destination followed the selection of the area by the national government because

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(1) U) d) . >-1 "Cl a 0 l. (1) (/) 0 u -~a \ \ 2km Xaak YalKu Lagoon .: HalfMoon fl'Bay L=.:,tii~-Akumal Bay .Xel Ha Playa Caribe well "t ~\ 0 I 2 km Figure 1-3 Map of study area a) shows collapse zones and areas ofancienl bays ( larger black dots) b) shows areas of groundwater discharge along the coast and sampling points. In both diagrams mod em reef is indicated by light dots offshore (Shaw 1997) -

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15 Salinity, % SW October 21-22, 1994 --0__/ Figure l-4 Salinity contours in Akumal during a period of no rain Contours are compressed on the highl y porous and penneable limestone At the 20% contour mixing of saltwater and freshwater below ground surface makes the gradients steeper ( Sha\v, 1997)

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Salinity, % SW May 16, 1995 16 storm surge Figure 1-5 Salinity contours in Akumal area after a heavy rain Compared to Figure 1-4, salinity gradient is displaced inland due to dilution by rain and groundwater flow (Shaw, 1997)

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17 Figure 1-6 Map of study area shov,ing groundwater flow in relation to porous limestone rock (indicated b y crosses ) and coliform contours from studie s conducted in Ma y A ugust 1997 ( Shaw, 1997)

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18 of its excellent beaches beautiful off-shore coral reefs, and Mayan ruins Cancun now receives over two million visitors per year and Quintana Roo close to three million annually The entire population of the state of Quintana Roo was less than 25 000 in 1950 but grew to around 200 000 by 1980 (Edwards 1986) Evidence from tourism development in other countries indicates that intensity of negative environmental and cultural impact are related to scale (Jenkins 1982 Rodenburg 1980). The geology of the coastal area of the eastern Yucatan is one of extreme topographic flatness underlain with carbonate rocks predominantly limestone of Tertiary age The soil is generally shallow ( 0-20 cm deep) which coupled with high permeability of the limestone, results in rapid infiltration of rain and high lateral movement. The result is a thin lens of groundwater (less than 70 m thick) overlying deeper groundwater that is close to the salinity of ocean water (Hanshaw and Back 1980) The Yucatan region is freshwater limited despite the ample rainfall ( around 1100 mm of annual rainfall ) and humid climate and strategies for effective water utilization have characterized human settlement in the region since the time of the Mayan civilization (Back 1995). These water limitations result from the nature of its almost pure limestone karstic geology without appreciable other sediments When the limestone dissolves forming solution depressions these channels are not filled, so retain high permeability and porosity This geology produces low hydraulic head, which results in restricted freshwater aquifers since the freshwater / saltwater interface is quite close to the ground surface near to the coast. The Yucatan also lacks rivers except in its southern portions because with the nearly flat topography of a coastal plain and absence of

PAGE 43

19 sediments infiltration of rain to the water table is extremely rapid (Espejel 1987 ) Seasonal variability of rainfall is considerable which also limits freshwater availability. The region s high permeability not only decreases the amount of freshwater available but also makes the water supply very vulnerable to contamination by sewage effluent agricultural runoff and the products of litterfall decomposition from the inland forests The resulting pollution, exacerbated by tropical climate which favors the growth of disease bacteria is widespread in the Yucatan (Back 1995) Sites of Mesocosm Tests Two subsurface flow wetlands for sewage treatment were constructed off the main street in Akumal to serve residences offices and public toilets These constructed wetlands are located about 250 m inland from Akumal Bay, and in close proximity (5-50 m) to a natural mangrove wetland as can be seen in an aerial photo of Akumal (Figure 17), a topographic map of the study area (Figure 1-8) and sketch of treatment wetland units and mangrove areas of the study ( Figure 1-9) Groundwater was encountered at less than 1 m below ground surface during construction in August 1996 There is a thin layer of sandy soil (6-10 inches) below which limestone rock is encountered Receiving Wetland The mangrove wetlands around Akumal are unusual in that most have a groundwater connection to seawater rather than having surface tidal channels But like all mangrove ecosystems, their hydrologic and salinity environments are highly dependent on the relative and shifting predominance of freshwater and seawater that they receive Productivity in mangroves typically increases as one moves from mangrove areas

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Figure 1-7 Aerial photograph of study area Akumal Quintana Roo Mexico N 0

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Bay -6 ~s s -6--Caribbean Sea i Half Moon Ray 0 100 200meters Scale ~o~rour forerval I meter Figure 1-8 Study area around Akumal Mexico showing location of the wetland s ystems at A ", en~arged in Figure 1-9 Contour lines in meters ( Shaw in press). tv ,: .. ........ l~ (,:~giovc

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wetland System l .-< N C I u u l !Om Cenote 0 Wetland System 2 Edge of Mangrove Discharge point ~ 0-ve e to tnal'\.o' Discnarg,e 1)1\' Mangrove E ~, \ (.I B C Sampling points A,B,C, D arid E Figure 1-9 Enlarged sketch of area "A" in Figure ]-8 showing location of wetland treatment areasmangrove where treated emuent was discharged Points labeled A to E are mangrove sampling stations D

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23 dominated by low-nutrient and high salinity seawater to ones enriched by freshwater nutrient inputs and with decreased salinity (Day et al. 1989) Mangroves have been shown to be effective in treating secondary wastewater. Se ll (1977) studied two South Florida tidal mangrove ecosystems enriched by effluent from a sewage treatment plant. Mangrove growth was enhanced and there were no significant differences in species composition seedling survival or litterfall between mangroves areas receiving enriched nutrient waters and control mangrove ecosystems. Soils in the Akumal region are characterized by low nutrient status. Noguez-Galvez (1991 ) studied nutrient levels near Carillo Puerto ( 19deg 16' N ., 88 deg 07' W ) about 50 km inland from the coast and 75 km south of Akumal after differing ages of fallow following slash-and-burn shifting agricultural use T otal Nin the 0-5 cm layer was 0.437 0 022% at 1 year fallow rising to 0 619 0 095% after 20 years fallow In the 6-1 lcm layer the total nitrogen data were 0 316% 0 044% after 1 year and 0.478 0 076% after 20 years. Phosphate levels were 12.16 1.75 mg/kg after 1 year in the 0-5 cm level rising to 16.72 4 .61 mg/kg after 10 yrs and 6 35 2 35 mg/kg in the 6-11 cm level after 1 year and 11.33 7 7 mg/kg after 10 years of fallow At Puerto Moreles Mexico about 70 km north of the study s i te Feller (1998 ) found autochtonous mangroves without external source of sediment creating a highly organic peat substrate in the saturated subsurface These soils are classified as solonchaks and histosols in view of their high organic content and salinity (McKee 1998) The overall environment is oligotrophic and dominated by calcium carbonate limestone Human impacts include road-making clearing diking filling and garbage dumping associated with tourist development. Road impoundments have not severed hydrological

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24 connections since drainage is predominantly through groundwater connection with both fresh and saltwater. Trejo-Torres et al (1993) found that Yucatan coastal mangroves export freshwater during the rainy season and receive considerable seawater during drier periods In Belize south of the study site mangroves were primarily phosphorus limited and fertilization with phosphorus or a combination of nitrogen phosphorus and potassium (but not with nitrogen alone) produced sizeable increase of growth in mangrove species (F eller 1995). Mangroves were found in five zones along the Yucatan coast depending on distance from the coast. Highest biomass and basal areas were found in the mangrove zone closest to the coast (F eller 1998) which is the zone receiving the experimental discharge of treated sewage effiuent at Akumal. Concepts Aggregated Conceptual Model F igure 1-10 is an aggregated systems diagram of the treatment unit within the context of the coastal economy and environment. The sources of natural energy include sun wind, rain inland groundwater flow and wave and tidal activity of the sea Primary producing ecosystems are the inland forest the mixed wetlands shaped by both freshwater and saltwater near the coast and the marine ecosystems ( seagrass coral reef etc.). The human economy is supported by these natural ecosystems local resources (limestone forest products) and imported goods and services Tourism is the principal source of monetary flow in the area ; it pays for goods and services The treatment wetland units make an interface between the wastewater produced by the human

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Akumal coastal zone Quintana Rao, Mexico Figure 1-10 Systems diagram showing the wetland treatment unit within the context of the coastal zone economy and ec ology.

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26 economy before discharging treated water and nutrients to be recycled back into the mixed wetlands Diversity vs Trophic Conditions in the Interface Treatment System These ecologically engineered systems provided an opportunity to investigate issues of diversity vs trophic state. Constructed wetlands have generally failed to maintain high species numbers and diversity This failure has been attributed to high nutrient waters favoring the growth of species (such as Typha spp. or Phragmites spp ) that out-compete other less aggressive species In the United States and Europe many constructed wetlands have not attempted to provide ecosystem attributes They were designed as monocultures or planted with only 2-3 species, but have nevertheless provided satisfactory water treatment (Reed et al, 1995) The relationship between nutrient status and species diversity is far from well understood Yount ( 1956 cited in Odum 1996) correlated pulses of nutrient enrichment with increased dominance, variation, competitive exc1usion and loss or masking of rarer species. However natural conditi ons of steady-state high eutrophication have also promoted high diversity as contrasted to sudden conditions of eutrophication caused by anthropogenic pollution (Odum 1996) Some types of human disturbance (e g fire grazing and cutting in Mediterranean-climate Israel) enhance numbers of species (Naveh and Whittaker 1979 cited in Mooney 1986) Similarly while the prevalent tendency is to regard high species diversification as a sign of ecosystem development toward maturity (Margalef, 1968) there are other circumstances in which high initial nutrient levels and species numbers are reduced as

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27 storages are consumed (Odum 1968), leading to suggestions that maximum species numbers may be maintained at intermediate successional stages (E. P Odum 1993 ) Ecological Succession in the Treatment System The research presented an opportunity to study ecological succession in the wetland mesocosms and to investigate some of the theoretical relationships posited for such self-organization Odum ( 1994) noted that succession is the process by which structure and processes are developed by ecosystems from available energies and resources These progressions often include system adaptation to physiological challenges the building of storages development of diversity and interchange with the larger external environmental setting. Ecological succession typically includes a period of rapid initial growth dominated by aggressive short-lived pioneer species giving way over time to species with high biomass and gross productivity but less net production Among the characteristic patterns observed after system biomass and non-l i ving organic matter have been increased and as primary succession gives way to a more mature or equilibrium stage are a greater balance between primary productivity and respiration. As succession proceeds the more mature ecosystem tends to display greater internal cycling and retention of nutrients increased specialization and mutualism and increase of efficiency of use of input energy (E. P Odum, 1971 ). The Akumal research offered an opportunity to track ecological succession and self-organization from an initial state of virtually lifeless quarried limestone gravel and to

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28 track ecosystem changes that resulted from the input of domestic wastewater to an initial planting of wetland species Major Objectives of the Research The major objectives of the present research were to develop a new ecologically engineered wastewater treatment system and to evaluate its effectiveness and integration into the Yucatan coastal environment and human economy Among the new elements under investigation were the efficacy of utilizing limestone gravel as the primary substrate for the constructed wetland the ability of constructed wetlands with high nutrient inputs to sustain a high level of biodiversity and devising an integration with the natural mangrove wetlands In addition evaluating whether the new treatment system was economically cost-effective compared to other approaches and whether its use of local resources ( evaluated through emergy comparisons with other alternatives) would make it more sustainable for a tropical developing country than conventional sewage treatment options FinalJy, if applied on a regional scale to what extent would such a system retain the anthropogenically-produced nutrients which pollute groundwater and threaten the health of off-shore ecosystems such as coral reef? Plan of Study 1 Two pilot sewage treatment systems were constructed using saline influent wastewater limestone gravel and multiple seeding of species on the eastern coast of the Yucatan 2 The living ecosystem was evaluated as it developed tracking species, diversity indices, percent cover leaf area index, and transpiration estimated indirectly

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29 3. The water and nutrient budgets were evaluated by analysis of inflow waters and outflow waters and a budget and simulation model that represents the seasonal cycle and role of the ecosystem were developed 4. After defining a representative square kilometer of coastal zone including tourist developments and their wastewater flows the coastal water budget was evaluated T he role the new wastewater systems can have in the coastal water budget if expanded to service a kilometer of coastline was examined 5 The share of the system contnbuted by the environment and the economy was evaluated using emergy transformity empower and empower densities of the principal features of the wastewater unit and the main parts of the coastal area (hotels people substrate limestone dollar circulation and exchange). Sampling and Measurement Periodic sampling of water quality was conducted for the septic tanlcs, wetland treatment compartments groundwater and mangrove receiving wetland Analys i s was done in local Mexican laboratories ( Alquimia, Cancun and Centro Ecologico Akumal ) for parameters such as coliform bacteria and biochemical oxygen demand (BOD5), wh i ch require immediate testing Other parameters such as phosphorus, nitrogen, suspended solids and alkalinity were tested in laboratories at the Water Reclamation Facility University of F lorida, Gainesville by Richard Smith, the laboratory manager Bulk density and water-holding capacity for soils from the mangrove receiving wetland were conducted in the laboratory of the Centro Ecologico Akumal. Soil samples from the mangrove receiving wetland were analyzed for organic matter content and phosphorus and nitrogen content at the at the Institute of Food and Agricultural Sciences

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30 (IFAS) Soil Testing Laboratory Gainesville Analysis for mineral composition of the soil was conducted using X-ray diffraction techniques by Dr. Willie Harris at the Pedology Laboratory of the University of Florida Gainesville. Field measurements for ecological characteristics such as species number cover and frequency were conducted during research visits to the study site Identification of species were made with Edgar F Cabrera a biologist from Chetumal Quintana Roo Limestone from the system was collected before treatment began and after 11 months of system operation Analysis of the limestone for elemental composition was done at the IFAS Soils Laboratory with the help of Dr. James Bartos Analysis of limestone gravel for phosphorus was done at the University of Florida Wetland Biogeochemistry Laboratory with the help of its manager Ms Yu Wang Experiments on limestone uptake of phosphorus were conducted at the same laboratory Outline of the Research Report The research was reported in the following manner. Chapter 2 gives the methodology followed in all the components of the research Chapter 3 presents results from the following areas a/ Ecological characterization of the limestone wetland ecosystem including species number biodiversity frequency cover leaf area index leaf holes interception of sunlight canopy closure and surface organic matter b / Wastewater treatment including total phosphorus total nitrogen biochemica l oxygen demand, total suspended solids salinity alkalinity and uptake of phosphorus by limestone gravel and water budget.

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31 c / Economic and emergy evaluation of the wetland treatment system and in comparison with an alternative conventional treatment approach. d/ Impact on the mangrove wetland including characterization of the hydrology and soil sediments of the ecosystem ; and nutrient status of the soils and water before and after discharge of treated wastewater effluent from the limestone wetland unit. d/ Simulation of the water budget of wetland treatment system and mangrove e / Regional evaluation o f application of the treatment wetlands. This was done by first assessing the emergy and monetary flows in a square kilometer of developed coastline then evaluating the impact on this larger system s water and nutrient budgets with and without the use of the wetland treatment systems Chapter 4 presents a d i scussion of the major findings of the present study, and commentary on important vectors in the new wetland system for treating domestic wastewater along the Yucatan coast. Observations are presented on the pattern of ecological succession the role of limestone and a simulation model is developed for the interaction of the environment and the tourist economy of the area Finally potential for future application of the system in the region is discussed and remaining questions for future research are listed. Appendix A contains water levels measured for the tide at Akumal in the mangrove and in nearby cenote (groundwater well) Appendix B presents literature data used in the model. Appendix C contains the emergy evaluation of the University of Florida sewage treatment facility that is used for comparison to the limestone wetland system

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Ecological Engineering Design CHAPTER2 :METHODS Treatment Systems A constructed wetland for sewage treatment was developed meshing with the environmental/ geological context of the Akumal coastline Following the concept of ecological engineering maximizing the work of natural elements minimizing the use of machinery and reducing cost. A system of contained wetlands was used to treat septic tank discharge using gravity-flow, eliminating the need for electrical pumps (Figure 2-1) Because of the thin soil layer high porosity of underlying limestone and high water table of the coastal settlements an impermeable concrete liner prevented discharge of wastewater before adequate treatment could be accomplished A two-celled system was used so that there was capacity to absorb torrential rains Limestone gravel with 1/ 4 -3 / 8 inch diameter was used in the system The advantage of using smaller size gravel is that surface area and porosity is increased However the trade-off is that smaller limestone gravel may undergo greater danger of compaction and dissolution over time (Steiner and Freeman, 1989 ) Larger limestone rock (2-4 inch diameter ) was used in the first and last meter of each treatment cell to minimize the danger of clogging near inlet and collector pipes 32

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Potable Water ~ ----11---Soil Level Constructed Subsurface Wetland System Figure 2-1 Schematic of wetland treatment system showing flow from houses to septic tanks to wetlands.

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34 Outflows from the treatment wetlands were discharged into natural groundwater mangrove wetlands where there was natural filtering capacity of rich, organic soils and root uptake The treatment wetland systems were built with financing and support from Planetary Coral Reef Foundation and the Centro Ecologico Ak:umal. Local Mayan contractors and laborers did the construction work. Local sources of limestone and sand were used Public meetings in Akumal explained the planned research and provided updates on research findings to government business and local residents Procedures for Start-up and Management An initial layer of sawdust mulch was applied to the system over the limestone establishing an aerobic layer for plants that could be sustained later by leaf litter drop Maintenance guidelines called for minimal interference without pruning vegetation or eliminating species Disease or pest pulses would be allowed since these form a part of nature s diversity mechanisms. Monitoring allowed tracking of natural self-organization of introduced and volunteer plant species Seeding with Biota The wetlands were planted with a wide variety of wetland plants some transplanted from local wetland areas some from local commercial plant nurseries others from the botanical garden at Puerto Moreles and local gardens in Ak:umal. Some species entered the system as seeds carried in by wind or animals from nearby wetlands as seeds or seedlings in the soil of plants transplanted from the wild, or during the construction process

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35 There was no attempt to limit species None were removed manually as unwanted ('weeds "). Trees and large palm species were planted at least 2 m away from the system piping to minimize maintenance problems with roots Multiple rounds of seeding were arranged following experience with promoting self-organization in mesocosms (Beyers and Odum 1993 ) Field Measurements Biodiversity Plant species richness was determined by identification of plant species in the wetlands with the assistance of E dgar Cabrera Chetumal Q R. a botanist from the region Transects of approximately 250 observations were conducted in each of the two treatment cells of the two wetland systems giving a total of about 1000 observations These observations were made in May 1997 December 1997 and July 1998 Comparisons with biodiversity of natural ecosystems in the region (mangrove and tropical inland forest) were done by conducting transects with 1000 individual plants identifying each to species in December 1997 Biodiversity was calculated using the Shannon diversity index (Shannon and Weaver 1949 ~ Brower e t al, 1991): H' = -I: P i log P i where P i = n / N p t is the proport i on of species 'T' in the total number of individuals in the population (N). The Shannon biodiversity index was calculated using the above formulas for log 2 and log 10.

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36 Frequency Frequency is a measure of the probability of finding an individual species with the overall population sample (Brower et al 1991) Plant species frequency in the wetlands was determined by analysis of the transects Each individual plant stem was counted as an observation in the transect. Data was tabulated for each treatment cell and cumulative data were tabulated for each wetland system and data for the combined two wetland systems were analyzed Cover Plant cover for each species was determined by 1/ use of 0 25 m2 quadrats in each treatment cell and estimating percent cover of each species present as well as percent of bare ground ; 2 / measuring canopy cover of the most prevalent species (15-20) in each treatment cell (May 1997) and 3 / estimating canopy coverage of all wetland species in each treatment cell (December 1997 and July 1998) Importance values Importance values (IV) were calculated combining frequency and cover data and dividing by two so that the sum of all IV values for each system equaled one These calculations were made using the May 1997, December 1997 and July 1998 field data The graph of these data called a dominance-density curve or species importance curve was plotted on a log/arithmetic scale against rank order (Brower et al 1991). Leaf area index Leaf area index was determined by the point-intercept method Approximately 50 measurements were made in each treatment cell of the wetland systems in May 1997

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37 December 1997 and July 1998 Using a tall piece of steel rebar moved a set distance along pre-assigned transect lines the number of leaves touching the pole were recorded Each treatment cell had approximately 50 observations at each round of study Leaf boles Holes in leaves due to herbivory decomposition and other causes were measured in December 1997 and July 1998 by estimating percent leaf damage and loss on 5 randomly selected leaves of each of the species present in the wetland. Then these data were multiplied by the relative frequency of each species to give an overall measure of leaf holes in the wetland systems Surface organic matter Surface organic matter was determined by collecting surface litter from four 0 1 m2 quadrats within each cell of the two wetland systems in July 1998 Four samples of the original woodchip / sawdust mulch from 0.1 m2 quadrats from a similarly constructed wetland system in Akumal were collected to provide a measure of the starting surface organic matter of the wetlands The surface litter was dried at 70C and weighed then combusted at 450C in a muffle furnace of the Water Reclamation Laboratory of the University of Florida and reweighed. Organic matter content of samples was determined as the difference between starting and final weights Solar insolation Solar insolation and light interception in the wetland systems was measured using a LI-COR LI-189 Quantum/Radiometer/Photometer equipped with a LI-COR Terrestrial Radiation Sensor Type SA (LI-200SA) pyranometer sensor. The pyranometer

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38 was factory calibrated against an Eppley Precision Spectral Pyranometer under natural daylight conditions giv i ng an absolute error of 5% maximum typically 3% Quantum light measurement results were in mol s -1 m -2 ( 1 mol s -1 m -2 is equivalent to 1 Einstein s -1 m -2 ) Light measurements were conducted on 28 July 28 1998 a cloudless day from 1050 to 1145 AM Measurements were made of ambient solar insolation outside the wetland systems before and after measurements of each wetland cell Approximately 30 measurements were made in each of the 2 wetland cells of wetland system 1 and 50 measurements in each cell of wetland system 2. Measurements were made 0 5 min from the edge of each cell and then every 1 m across the cells Canopy closure Canopy closure in the wetland systems was evaluated in July 1998 using analysis of hemispheric canopy photography (Rich 1989). Photographic images of the wetland canopies were made using a 180 fish-eye lens adapter on a Nikon camera N i ne photos were taken at predetermined and equivalent locations in each of the wetland cells and in the discharge area of the mangrove ecosystem then digitized and converted to a gray scale using Photoshop 2 0 Analysis for amount of canopy and light penetration was done with MapFactory software

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39 Analytic Measurements Total nitrogen and total phosphorus To determine nutrient treatment in the wetlands of phosphorus and nitrogen laboratory tests for total phosphorus and total nitrogen were conducted on wastewater samples from the wetland treatment systems Phosphorus was determined using persulfate digestion followed by the ascorbic acid method, SM 4500-P (APHA 1995). Tests were conducted at the University of Florida Water Reclamation Laboratory. Total nitrogen was determined using the persulfate method SM 4500-N (APHA 1995) Samples were collected from the septic tank, from the standpipe at the end of cell 1 and cell 2 in each wetland treatment system. A sample was collected from a cenote (shallow groundwater well) with water accessible a few feet below ground level located just a few meters from the wetland treatment system This cenote is located on the inland side of the wetland systems and is presumed to give some indication of local groundwater background levels. After collection in a 10 ml sample bottle 1-2 drops of concentrated sulfuric acid was added to preserve the samples until shipping to the laboratory To determine variability in the total P and total N laboratory test two samples were run three times in August and September 1997 so that standard deviation and standard error of the mean could be determined

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40 Biochemical oxygen demand (BOD) Biochemical oxygen demand (BOD) was determined using EPA method 405 l (EPA, 1993). This is a five day test with sample kept at 20C Samples (250 ml) were collected as described above and kept cool during transport to the laboratory. The materials were tested in laboratories in Cancun The tests from January to April 1997 were conducted at Laboratorio Alquimia Cancun and those from May 1997 were conducted at the laboratory of Jose Castro in Cancun Both are certified laboratories for water analysis Chemical oxygen demand (COD) Chemical oxygen demand in the water of the mangroves was determined using the closed reflux colorimetric method APHA 5220D (APHA 1995) The sample was digested using K2Cr2O7 H2SO4 and HgSO4 Tests were conducted using Hach prepared reagants and analyzed on a Hach DR-3000 colorimetric instrument at the laboratory of the University of Florida Water Reclamation Facility Total suspended solids Total suspended solids (TSS) in the wastewater were determined using the filterable residue a gravimetric method with the material dried at l 80C EPA method 160 1 (EPA 1993 ), method 2540DSM (APHA, 1995) 250 ml. samples were collected from the seven points described above and stored for shipment to the Water Reclamation Laboratory University of Florida where the tests were conducted

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41 Fecal coliform bacteria Fecal coliform in the wastewater was determined using membrane filtration and most probable number (MPN) of colonies per 100 ml of sample This is method 9222DSM (APHA, 1995). Samples ( 175 ml) were collected from the seven points described above and transported to the laboratory in Cancun for analysis within hours of collection. The same laboratories that conducted the BOD-5 tests conducted the analyses for fecal coliform until May 1998, when analysis was conducted in the water laboratory of the Centro Ecologico Aku.mal. Alkalinity Alkalinity of the water samples was determined by titration (buret) method 2320B (APHA, 1995). Samples weighed 50 ml and the method used .02 N sulfuric acid Salinity Salinity of water samples from the septic tank and wetlands was determined with use of a hand-held refractometer accurate to +/ -0 5 parts salt per thousand Phosphorus Uptake by Limestone Initial P content and uptake in wetlands Samples of limestone were analyzed for initial phosphorus content and phosphorus content after exposure to sewage in the treatment wetlands Pre-exposure limestone was collected during construction and bagged for later analysis In December 1997 after one year o f sewage treatment had occurred composite limestone samples were collected from each of the treatment cells of systems 1 and 2 These were divided into limestone from the layer above the sewage line and those at 0-10 cm depth 10-20

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42 cm depth, 20-30 cm depth 30-40 cm depth and 40-50 cm depth These limestone samples were roughly pulverized mechanically then ground in a ball grinder. Inorganic P analysis conducted in the Wetland Biogeochemistry Laboratory at the University of Florida, was determined as follows Following grinding, the limestone samples were dried in an oven at 70 deg C for 48 hours Then a subsample (0.5 g) of the ground limestone was extracted with 25 ml of lM HCl for 3 hours then filtered through a 0.45 micrometer pore size membrane filter. The HCl extract was stored at 4C in a 20 ml polyethylene vial. The HCl extract was analyzed for inorganic P using an automated ascorbic acid method (Method 365 1 EPA, 1995) Calcium/magnesium composition of Yucatan limestone The limestone was analyzed for calcium and magnesium content at the Soils Laboratory of the Institute of Food and Agricultural Sciences (IFAS) University of Florida The procedure was to grind and dry samples of limestone in a 120C oven for 4 hours Then 5 x 1.0 gram dried sample was placed in a 1000 ml graduated beaker and 125 ml of lN HCl solution was added to dissolve the limestone. The solution was diluted to 250 ml of 0 .25M hydrochloric acid The beaker was covered with a watch glass and boiled gently on hot-plate for 10-15 minutes Condensate was washed into beaker with de-ionized filtered (D.I .) water and cooled to room temperature. The solution was brought to approximate volume of 1000 ml. with D.I water. Analysis for calcium/magnesium was by inductive coupled plasma spectroscopy

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43 Experiments on phosphorus uptake by limestone To determine reaction kinetic rates of the Yucatan limestone with respect to phosphorus a series of lab and field experiments were designed The experimental procedure to determine phosphorus uptake by limestone was to combine limestone gravel samples from the wetlands Five hundred ml plastic bottles were filled with approximately 250 grams of Limestone gravel. Bottles were then filled with 450 ml of phosphorus solution This left some airspace below the neck of the bottles. For the laboratory experiment there were 5 experimental treatments x 3 replicates for a total of 15 bottles The initial phosphorus concentrations were 5 6 mg P / liter 11mg P / liter 22 mg P / liter 56 mg P / liter and 111 mg P/liter. After addition of phosphorus solution bottles were maintained with caps only loosely on, allowing air exchange Bottles were shaken once a day After 10 days 10 ml samples were taken and filtered through a 0.45 m membrane filter at 1,2 4 ,6 and 10 days Separate syringes and filter cases were used for each of the six treatments Samples were stored in a freezer until analysis for soluble reactive phosphorus. For the field experiment 3 x 500 ml. bottles with 250 grams of limestone gravel prepared at the same time as the laboratory ones were loaded with 450 ml of actual wastewater from the septic tanks in Akumal Mexico Three bottles with 250 grams of limestone were filled with 175 ml of actual wastewater (to approximate the condition in the wetland treatment system that the sewage water covers the limestone). The bottles had 10 ml samples taken and filtered through a 0.45 micrometer membrane filter at 1,2,4 6 10 and 30 days after loading The samples were kept in a freezer until shipment to the University of Florida Water Reclamation Laboratory for soluble reactive

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44 phosphorus analys i s Analysis for soluble reactive phosphorus used EPA Method 365 .1 (EPA 1995) Water Budget of the Wetland Systems In May 1997 and December 1997 the water budget of the wetland systems were determined by measuring inputs and outputs from the system. The only water inputs to the systems are effluent from the septic tanks and direct rain, as no surface runoff or groundwater enters the constructed wetlands By draining the system 1 and system 2 septic tanks and then measuring rate of re-fill it was possible to estimate hydraulic loading System evapotranspiration was calculated by measuring the decline over time in the water levels of the standpipes in the control box at the end of each cell of the wetland systems (see Figure 2-3 of the construction blueprints) Water-holding capacity of the gravel used in the wetland was estimated by filling a known quantity (20 liter bucket ) with the limestone gravel and then measuring the amount of water that the volume holds The only outputs from the system are evapotranspiration and discharge from the outlet in the control box of cell 2 Thus once the average daily evapotranspiration is calculated, the average discharge from the system may be estimated by difference from average input from the septic tanks Economic Evaluation Data on construction and maintenance costs of the wetland and package plant sewage treatment systems were collected Annual costs were estimated using expected lifetimes of system components

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45 Emergy Evaluation Comparative evaluations of the emergy involved in the wetland sewage treatment system and a conventional package plant sewage system were carried out using survey data on materials labor equipment used in constructing and operating the systems plus data on natural resource flow in the area From these emergy evaluation tables were developed and emergy indices used to compare the sewage treatment systems Receiving Wetland Biodiversity Biodiversity of the mangrove area receiving discharge from Wetland system 2 was monitored for biodivei:sity before effluent began in December 1997 Biodiversity ~as determined by ten transects of 100 individual plants identified to species Shannon diversity was then calculated from these data (see previous section). Mangrove Soils Depth of the mangrove soils in the vicinity of the wetland discharge was determined in December 1997 by driving a piece of 1 / 8 inch steel rebar into the soil until it struck rock. This was done in four directions each 90 deg from the next from the center of the discharge with 20 total observations each made at 3 m intervals An isopach map was generated from these data. Wet/dry weight of the mangrove soils was determined in December 1997 by drying five sample bags of 30 cm. deep soil cores at 70C until no further weight loss was observed Bulk density was calculated by taking five soil cores to a 30 cm depth and then determining wet weight and dry weight after drying in an oven at 70 C until there

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46 was no further weight loss. Five soil samples collected in December 1997 were analyzed by the Soil Laboratory of the Institute for Food and Agricultural Sciences (IFAS) University of Florida for total phosphorus and total nitrogen (using Kjeldahl method for N and the dry ash method for P) and total organic content (by loss on ignition method) These latter tests are described below: Loss on ignition test for soil organic matter determination (Magdoff et al 1996) was used for soils with organic content greater than 6%. Five gram soil samples were placed in a pre-heated oven at 120C for 6 hours After cooling for 30 minutes a weighed subsample of soil was placed in a beaker and placed in a muffle furnace set to 450 C for at least 5 hours For this study samples were left for 14 hours After cooling to room temperature final weight was recorded Percent organic matter was determined by comparing final weight with initial weight of the soil samples. Total Kjeldahl Nitrogen (TKN) and dry ash method for phosphorus (Hanlon et al 1998) were used by the IF AS Soil Laboratory in nutrient analysis of the mangrove soils 1n the TKN procedure 0.5 g of soil is digested with 2 0 g of Kjeldahl mixture in a digestion tube The mixture is wet with pure water and O 5 ml of concentrated sulfuric acid is added The tubes are placed on a preheated aluminum block digester at 150 deg C for 0 5 hours then the temperature is increased to 250C for 2 hours One ml of hydrogen peroxide is added by pipette in two steps of 0 5 ml. A glass funnel is placed over the tube and digestion continues for 2.5-3 hours The tubes are removed from the digester and cooled then the sides of the tubes are washed with 5-10 ml of pure water After mixing with a vortex shaker the digestate is moved to a 100 ml volumetric flask. Approximately 20 ml of solution is filtered through a Roger' s Custom Lab 720 into a 90 ml. plastic cup

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47 A filtered subsample is transferred to a 20 ml. plastic scintillation vial and refrigerated until analysis on the RFA (air-segmented continuous-flow automated spectrophotometer). Final step is analysis on the RF A calibrated with digested standards for total nitrogen. In the dry ash P analysis 1 g of oven-dry soil is combusted in a 500C muffle furnace to ash for a minimum of 5 hours The ash is then moistened with 5 drops of distilled water and dissolved with 5 ml of 6 0M hydrochloric acid. After 30 minutes the solution containing the ash is transferred to a 50 ml volumetric flask and brought to volume with pure water A filtered subsample is transferred to a 20 ml. plastic scintillation vial and refrigerated until analysis on the RFA (air-segmented continuousflow, automated spectrophotometer). F i nal step is analysis on the RFA calibrated with digested standards for total phosphorus. Micro-analysis for soil composition The minera l portion of the mangrove soils was assessed using X-ray diffraction at the Soil Pedology Laboratory of the University of Florida After soil samples were mixed organic materials were digested by addition of sodium hypochlorite 5 25% by weight to cover the sample After digestion for 20 hours each sample was put through a 15 micrometer sieve into distilled water. The soil sample was centrifuged at 2500 RPM for 3 minutes and the supernatant liquid poured off. Then a 1 M solution of sodium chloride was added and the solution again centrifuged at 2500 RPM and the supernatant poured off. Then de-ionized water was added to the solid materials and centrifuged at 3000 RPM for 5 minutes Some of the liquid was poured off and oriented mounts were prepared for X-ray diffraction analysis by depositing

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48 suspended materials onto porous ceramic tiles under suction One of the tile mounts was treated with potassium chloride and two with magnesium chloride T he KCl and MgCh were added four times and pulled through the ceramic tiles by a suction device Then each ceramic tile soil mount was rinsed with de-ionized water four times To one of the MgCh treated tiles 30% glycerol was added. The clay tiles were then analyzed by X-ray diffraction Samples were scanned from 2 to 60 degrees 28 using a computer-controlled x-ray diffraction system equipped with stepping motor and graphite crystal monochromator Power was 35 kV and scanning rate was 2 28 per minute Nutrients Mangrove soil samples collected before and after discharge commenced at the beginning of May 1998 and monthly from June to August 1998 were analyzed us i ng the Total Kjeldahl Nitrogen and Dry Ash Phosphorus methods described above in the section entitled Mangrove Soil. Soil samples were collected at 1 3 5 and 10 meters east, west north and south of the discharge point. Mangrove water samples collected in December 1997 and April 1998 were analyzed for biochemical oxygen demand fecal coliform suspended solids total nitrogen total phosphorus, salinity and alkalinity using methods described in the section on Analytic Measurements These tests were repeated after discharge commenced in May and monthly samples were collected June July and August 1998 to ascertain changes in the nutrient and water quality status of the mangrove groundwater.

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49 Hydrogeology Water in the mangrove site at Akumal exchanged through groundwater channels from below. There was no surface connection to the sea Hydrologeological studies of the fluxes with the receiving area were made by comparing surface water levels with those of a nearby cenote (well) and the sea. This was done with a water level chart recorder of surface water height during May 1997, December 1997 and July 1998 Direction of water flow in the area was determined from the heights of water in three polyvinyl chloride (PVC) pipes, 10 cm in diameter, placed 60 cm deep in the mangrove soils, which served as piezometers. Elevations were determined by use of manual water-tube levels. Location and directional orientation of the piezometers was determined with a surveying level. Water levels in the piezometers are equal to the elevation of the hydraulic head (Fetter, 1994). Flow lines were determined by triangulation of these data on a map of the potentiometric surface in the vicinity of the discharge outfall. A series of 5 PVC monitoring pipes were installed in December 1997. One pipe was installed 1 meter upstream from outfall of the discharge pipe from the wetland, and three other pipes were installed 1, 3 and 6 meters in the direction of water flowlines in the mangrove. The fifth monitoring pipe was installed 12 meters southeast of the discharge pipe, in the direction of the edge of the mangrove. Simulation Model of the Water Budgets Simulation models were developed for the treatment units and their discharge into the receiving wetland This model followed the methodology outlined in Odum (1994) and Odum and Odum (1996). After selecting a system boundary, outside sources were

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50 listed from the environment and from the human economy. Relationships and pathways between system components were identified including exports from the system Relationships were translated into energy language symbols and then into rate equations After average values were put on the pathways and in storage symbols coefficients were calculated with spreadsheet. A simulation program was written in BASIC and sensitivity studied with scenarios Simulation runs were compared with field and literature data Evaluating Potential of Wastewater System for the Coastal Zone Potential significance of the treatment system was studied by considering a square kilometer of developed coastal area operating the treatment system Evaluations were done on two scales : the treatment systems and the square kilometer Emergy Evaluation An emergy evaluation of the square kilometer area was made using data from published sources data on use of natural resources and human services obtained from hotel owners homeowners and residents, and from town maps showing density and layout of properties in the area Emergy analyses followed methods developed by Odum and Brown ( Odum 1996 ; Doherty and Brown 1993 ; Brown and Ulgiati in press). This was done by developing systems diagrams showing energy sources system components pathways of energy and material flow in the system system outputs and depreciation/heat sinks These systems diagrams were developed in three forms : detailed aggregated and three arm diagrams Then data was collec t ed using published and new data on material and energy flows

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51 Transformities Emergy tables were compiled using transformities for the items. Table 2-1 presents the transformity values used in all the emergy evaluations of the present study. With these system relationships and data, indices to compare emergy flows of the environment with those of the natural environment are evaluated. Among the indices evaluated were the investment ratio emergy yield ratio, ratio of nonrenewable to renewable resources and empower density. These emergy indices characterize the intensity and balance of environmental vs. developed resources (Odum, 1996). Economic Evaluation Economic impact on the square kilometer coastal area were compared for the use of treatment wetlands or conventional package plant treatment systems. These data were evaluated as a percentage of overall capital investment and yearly monetary flow Regional Water Budget A regional water budget for a square kilometer of coastline in the study area was developed including precipitation inflow of groundwater from inland, tidal exchange evapotranspiration, pumped water and sewage Budgets were compared for development with no sewage treatment and development with treatment by constructed wetlands Regional Nutrient Budget Regional nutrient budgets were developed for the same scenarios that of development of a square kilometer of the Akurnal coastal region. Nutrient budgets for nitrogen and phosphorus were examined for the scenarios of full development without sewage treatment and with treatment by constructed wetlands

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52 Table 2-1 Transformities and emergy per mass used in this study Item Transformity Emergy per mass Reference Sej / J Sej/gram solar emjoule / joule solar emjoule / gram Sunlight 1 (by definition) a Wind kinetic 6 63 E2 a Rain geopotential 8 888 E3 a Rain chemical potential a energy 1.5444 E4 Tide 2 3564 E4 a Waves 2 5889 E4 a Earth cycle 2.9E4 a Wood 3.49 E4 C Groundwater 4.8E4 a Gas 4 .8E4 a Motor fuel (liquid ) 6 .6E4 a Primitive labor 8 1 E4 b Food 8.5E4 C Hurricanes 9 579 E4 d Electricity (global average) 1.736 E5 a Agricultural and forest 2E5 C products Untreated wastewater 5.54 E5 f Concrete 7 0 E7 h Plastic products 9 26 E7 C Pulp wood 2 75 E8 e Sand 1.0E9 a Limestone 1.0E9 a Steel + iron products 1.78 E9 a Potassium chloride 1 1 E9 a Machine!X 1.25 ElO a Odum, 1996 b Odum and Odum 1983 c Brown et al. 1992 d Scatena et al. in press e Christiansen 1984 f Green, 1992 g Odum et al., 1983 h Brown and Mcclanahan, 1992

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CHAPTER3 RESULTS Treatment Mesocosms Design and Operation of the Wetland Units In August 1996 the two wetland sewage treatment systems were constructed. One henceforth referred to as wetland system 1 was designed to treat the wastewate r of 16 people and covers an area of 50.6 m2 The second, wetland system 2", des i gned to handle the sewage of 24 people has an area of 81.2 m2 The treatment process for each wetland begins with a well-sealed two-chamber septic tank which receives wastewater from the residences and offices by gravity flow Solids settle out in the septic tank which serves as primary treatment and the commencement of microbial treatment of the sewage A filter at the discharge pipe from the septic tank ensures that no solids larger than 1/64 inch can enter the wetland Effluent from the septic tank overflows by gravity feed into a header pipe which distributes the sewage along the total width of the first of two treatment cells (compartments) of the constructed wetland These wetlands were designed as subsurface flow systems and have a cement liner and sides to prevent movement of untreated sewage into the groundwater. They were filled with limestone gravel to a depth of 0.6 m Each cell of the wetland has a collector perforated 4 inch PVC pipe at the end which direct wastewater into the 53

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54 centrally-located control box Inside the control box, an adjustable standpipe determines the level at which wastewater is maintained in the wetland as wastewater overflows its open end either from Cell 1 into the header pipe for Cell 2 or from Cell 2 to fina l discharge Normally the standpipe is fully vertical at a height of 55 cm The wastewater is kept 5 cm below the level of the gravel. The sides of the system are at least 15 cm above the top of the gravel to allow for natural litter buildup and to prevent overflow in heavy rains. The terrain was graded to preclude surface water runoff inflow into the wetland systems Hydraulic residence with design loading is 5-6 days depending on seasonal evapotranspiration After the cement liner was completed the system was filled with water and leak tested Then the gravel was added and leveled Larger limestone rock (5-10 cm) was used in the first and last meter of each cell around the header and collection pipes to minimize the dangers of clogging After the addition of the gravel the systems were filled with tapwater and planted with wetland plants gathered from nearby wetlands or purchased from botanical gardens or commercial plant nurseries in the area Soil was not introduced into the system except for rootballs of the plants. The plants were planted with at least 2-5 cm contact with the water. After planting, the two wetlands were mulched with 2-4 cm sawdust. After discharge from Cell 2 of the wetland the wastewater from System 1 enters perforated drainage pipes that slope away from the wetland The trenches in which these p i pes were laid were back-filled with limestone gravel to prevent clogging by dirt System 2 effluent is sent to the nearby mangrove wetland and discharged near soil surface The blueprint drawings (F igures 3-1 to 3-10 ) show additional details of the construction Limestone gravel depths were increased for wetlands built subsequently to this research in the area were done to a design specification of 80 cm to i ncrease hydraulic

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Subsurf oce \./etlond Sewoge TreotMent Design Mark Nelson Pn e 1 of 10 Do te1 10/02/97 Dvero.ll IsoMetric View Copyrloht 1997 Marl< Nelson, Confldentlnl Notes DAil WCllls ,4wnterproof concrete, leCll< test cells Clnd control boxes before grClvel fill 2)Bcicl
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Subsurface \,/etlond Sewage TreotMent Deslgn1 Mork Nelson Po e 2 of 10 Do te1 10/02/97 _f 9 7 Dvero.ll Isor,etric View of Piping Copyright 19971 Mori< Nelson, Confidential Notes 2'-5 3/8' --, DAil Piping ... PVC, see details pages 6 and 7 2)Septlc tank and leach field gravity feed require at least 1 to 50 slope for proper flow 3)Septlc Tonk and/or greo.se tro.p require Zabel filter ")Cover all piping to prevent sun do.1"10.gw 5)Collector pipe risers optional 6)Renovable ca s on risers f-igure 3-2 Construction blueprint: isometric view of piping in the wetland system.

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Subsurfo.ce \./etlo.nd Sewo.ge Treo.tMent Deslgn1 Hnrk Nelson Pae 3 of 10 Da te1 10/02/97 I '.l' ?' ;, 7 L ___ I __ Stones 2 to -4 / to surfllCl' Mulch l'Dt>rp l t'-6' nlnlMUM 6' ~ Center Section View Copyright 19971 Mori< Nelson, ConFldentlnl [ r 10 2-10 I 2'-6' Notes1 DAIi wnlls -4' waterproof concrete 2)1.Jo.-terlevel 30', pea gravel 31' deep 3)Mulch layer 1 applied after planting -4 )2' to -1' rock fill to 31 ', cover with r1ulch -4 places S)All rock and gravel fill Must be washed 6)2' to -4 rock a.round collector pipes not shown due to perspective 7)Posltlon stondplpe ne>< ensuring that It con be lowered to horizontal position within the control bo>< Figure 3-3 Construction blueprint: center section view of the wetland system.

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SubsurFo.ce \./etlo.nd Sewo.ge Treo.tMent Design Mark Nelson ~e 4 of' 10 Date 10/02/97 l' C,' Stones 2' to 4 dla., to surface Pea. Gravel / 31' Deep Mulch !'Deep ---1'-6' Side Section Showing Fill Mo. terlo.ls Copyright 19971 Mori< Nelson, Confidential Stones 2 to 4 dla. to surface Notes Pea. Gra.vel 31' Deep Mulch l'Deep 1 '-6' DAil walls -4 waterproof concrete 2)\Jo. ter level 30', peo. gravel 31' deep J>Mulch lo.yer 1 o.pplled o.fter planting -4)2' to -4 rock fill to 31', cover with Mulch -4 plo.ces S)All rock and gro.vrl fill Must lor wo.shrd figure 3-4 Construction blueprint: side section showing fill materials in the wetland system

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Subsurfo.ce \Jetlo.nd Sewo.ge Treo.tMent Deslgn1 Mark Nelson ~e 5 of' 10 Date1 10/02/97 Box Deto.il with Dir1ensions Copyright 19971 Marl< Nelson, Confidential Notes1 DI thick wood control box cover, see1led with rubber ge1sket to prevent odor e1nd Mosquito breeding 2H we1terproof concrete we1lls 3)Posltlon stllndplpe ne>ct to one we1II of the control box ensuring the1t It ce1n be lowered to horl2onte1l position within the control bo>< figure 3-5 Construction blueprint: control box with dimensions of the wetland treatment cells.

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Subsurf o.ce \.Jetlo.nd Sewo.ge Treo.tMent Design Marl< Nelson Pa e 6 of 10 Dote, 10/02/97 Cell 1 Hender Deto.il Copyright 19971 Mark Nelson, Confidential Notes l>All hales drilled nt centerline of' -1 pipe 2>DurlnQ rock filling, pipe Must rer,Qln level 3)Septlc tQnk Qnd/or greQse trQp require ZQbel filter ta prevent solids froM entering trentMent systeM Pigure 3-6 Construction blueprint: treatment cell I header detail of the wetlands. 0\ 0

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Subsurf a.ce 'wetla.nd Sewa.ge Trea.tMent Design Mnrk Nelson Pn e 7 of 10 Dn te1 10/02/97 Cell 2 Heoder Detoil Copyright 19971 Mark Nelson, Confidential Notes IH PVC pipe saw scored at t Intervals 2)Ensure tho t during rock fill, header pipe reMolns level Figure 3-7 Cons trnction bl ue print: treatm e nt cell 2 header det ail of the wetlands.

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Subsurfo.ce \./etlo.nd Sewo.ge Treo.trient Nelson Da te1 10/02/97 / Lorge Syster1 Dre.infield Deto.il Copyright 19971 Marl< Nelson, Confidential Notes l)[Qch drQlnfleld pipe l'IUst hQVe a riser with reMOVQble ccip for MolntenQnce 2>Dralnfleld piping Must hQve Q Min. slope of 1 for proper flow 3)AMount of drQlnfleld needed depends on systeM size Figure 3-8 Cons truction hlucprint: schematic showing drainfield detail for large wetland systems.

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Subsurf o.ce \./etlo.nd Sewo.ge Treo.trient Design Harl< Nelson Pa e 9 of 10 Date, 10/02/97 Sr-io.ll Syster-i Dre.infield Deto.il Copyright 19971 Marl< Nelson, r.onfldentlal Notes DDralnfleld pipe Must have a riser with reMova~e cap for Ma~tenance 2>Dralnfleld piping Must have a Min. slope of 1,so for proper flow 3)AMount of dralnfleld needed depends on systeM size Figure 3-9 Construction blueprint: schematic showing drainfield detail for small wetland systems.

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Subsurf a.ce \./etlo.nd Sewage Treo.trient Design, Mark Nelson Pa e 10 of 10 Date, 10/02/97 Geo-Textile Cloth 6' riln. grn vel under pipe 2' Druinfield Cross Section Copyright 1997 Marl< Nelson, Confidential Cover gro. vel with 6' so.nd or soil 8' Notes 4' perforo.ted dro.ln pipe, slits fo.clng down DMln. slope 1 For proper Flow 2>P~e perforated ~th saw cuts 3)Cross section shown here applies to all dralnFleld lnstalla tlons unless speclf'led other wise Figure 3-10 Construction blueprint: drainfield cross-section drawing of wetland system

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65 retention time rather than the 60 cm of limestone used in the two research wetlands of this study Ecological Characteristics Patterns of biodiversity and dominance In May 1997 December 1997 and July 1998 (nine, fifteen and twenty-three months after planting, respectively) examinations of the wetland systems for species diversity was conducted with the assistance of Edgar Cabrera a botanist from Chetumal, Quintana Roo A total of 68 species were identified in May 1997 70 species in December 1997 and 66 species in July 1998 (Table 3-1) Species native to the Yucatan constituted 47 of the 66-68 species present in May, 1997 and December 1997 with the remainder being cultivated and introduced species. Plant species richness (total number of species present) in each treatment cell decreased slightly over the course of the study as shown in Figures 3-11 3-12 and 3-13 For example System 1 Cell l had 41 species in May 1997 37 species in December 1997 and 35 species in July 1998 ; while System 1 Cell 2 had 37 species in May 1997 35 species in December 1997 and 36 species in July 1998 In May 1997, wetland System 1 averaged 39 plant species per cell in December 1997 and July 1998 the average was 36 species Wetland System 2 averaged 47 species per cell in May 1997, 45 species in December 1997 and July 1998 Considering the systems as a whole, in May 1997 there were 63 species in System 2 (with 482 observations) 17% higher than in wetland System 1 with 54 species (from 482 observations) (Figure 3-14 ). By December 1997 plant species had declined by about 10% in

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66 Table 3-1. Plant species in the treatment wetlands from surveys of May, 1997, December, 1997 and July, 1998. Total number of species as of May, 1997: 68 species; as of December, 1997: 70 species, as of July, 1998: 66 species. Scientific Name Common Name Notes: N = Native, I= Introduced; C= Cultivated D2 Acalypha hispida Cola de gato ; cat's C; red cattail flowers tail Acrostichum danaefolium Helecho N; wetland fern, to 3 m Ageratum littorale N : blue-flowering little shrub (purplish flowers); annual Alocasia macrorhiza Mafota; elephant I; starchy root, very shiny ears, taro Large leaves; leaf is straighter and flatter than Xanthosema N2 Aloe vera Sabila C N2 Alternanthera N ramossissima D1 Angelonia angustifolia N; delicate shrub, purple flowers Anthurium Moco de povo N; epiphyte Schlechtendalii Nl Anthurium sp. N Asclepias curassavica N; orange and yellow flowers DI Bambusa sp Bambu; bamboo I Bidens pilosa Margarita N; yellow or white flowers (like daisy) Bravaisia tubiflora Sulub N; pink flowers like bells Caladium bicolor Bandera C; decorative taro Canna edulis Platonillo; canna I; yellow flowers lilly N2 Capraria biflora Claudiosa N Carica Papaya Papaya N; edible fruit DI Cestrum diurnum Galon de noche I; shrub / tree CEA Cell 2, long thin leaves Chamaedorea Seifrizii Palma camedor N; palm Chamaesyce N; delicate shrub with tiny hypericifolia white flowers Chrysobalanus icaco Icaco N; woody, sturdy shrub with thick leaves Nl Cissus sicyoides N Cissus trifoliata N; vine, elongated, ovate leaves Citrus Aurantium Naranja agria ; C; edible fruit orange tree

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67 Scientific Name Common Name Notes: N = Native, I= Introduced; C=Cultivated Coccoloba uvifera Uva de mer; sea N; beach tree, prostrate or grape upright Conocarpus erecta Botoncillo; N; mangrove area tree buttonwood tree Corchorus siliquosus N; woody shrub, long-hard seed pods (tree) Cordia sebestena Siricote N; tree with large leaves, (next to Eleocharis CEA Cell 2) N2 Crinum amabile Lidio reina C Dl Cucumis melo Melo; melon I; melon vine D2 Cyperus ligularis Zacate cortadera N NI Delonix regia Poinsettia C NI; Desmodium incanum N; 3-leaved leguminous vine D2 N2 Desmodium tortuosum N Distichlis spicata. N; grass DI Eclipta alba N; like botoncillo with dots on leaves; Eleocharis cellulosa Spike reed grass N; short wetland reed DI Eleusine indica N Eupatorium albicaule N: 2 notches on leaves nearer base DI Euphorbia cyathophora N DI Eutachys petraea N; grass with "feathers" on ends F/averia linearis N; yellow flowers Hymenocallis littoralis Lirio/Spider lilly N; white flowers ; NI Jpomoea indica morning glory N; vine with heart-shaped leaves lpomoea Pes-caprae rinonina N;vine, morning glory family NI; lresine celosioides N; flowers are scales D2 lxora coccinea Ixora I; yellow or orange flowers, low shrub Kalanchoe pinnata I Dl Lactuca intybacea Milk weed N; CEA Cell I D2 Lantana involucrata oregano xiru N; small flowering shrub, woody shrub; small serrations on leaves; succulent; fragrant leaves N2 Leucaena glauca C

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68 Scientific Name Common Name Notes: N = Native, I= Introduced; C=Cultivated Nl; Lochnera rosea Teresita C; lavender flowers D2 Dl Ludwigia octavalis N; yellow flowers Dl Lycopersicum esculenta Tomate; tomato I; tomato plant D2 Melanthera nivea N; small button-white flowers on sprawling shrub; 3-lobed leaves N2 Mimosa sp. N Malvaviscus arboreus tulipancillo N; red flowers, tree Musasp. Platano; banana C; edible fruit Nerium oleander Oleonder ; oleander I; pink flowers, small tree Nl Nopalea cochini//ifera Napolito C; cactus ; used as food Paspalum virgatum Sacate N; sharp-leaved clump grass Pedilanthus I tithymaloides Nl; Pelliciera alliacea N; long stalk, delicate flower D2 Philodendron sp N Phyla nodiflora N: red stems, white flowers, sprawling shrub with sharp notches near tip of leaves, deep-grooved veins N2 P hyllanthus niruri N Pluchea odorata Santa Maria N; purple flowering shrub Dl Porophyllum punctatum N; decorative black dots on leaves, shrub, small leaf DJ Portulaca oleracea Verdolaga; moss N; various colors rose Psychotria nervosa N Rabdadenia biflora N; "mangrove-like" vine CEA Cell 2 N2 Rhizophora mangle Red mangrove N Rhoeo discolor Platonillo morado; N; purple and green leaves, roseatte form Sansevieria triasiate Lengue de suegra C; small agave-like Scindapsus aureus Telefono C; variegated leaves Nl; Selenicereus Donkelaarii N: viney, thin cactus D2 Senna biflora Modrecacao N; tree with rounded leaves; with a bunch of small, varied colored flowers DJ esbania emerus N; tree with leguminous leaves

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69 Scientific Name Common Name Notes: N = Native, I= Introduced; C=Cultivated Se s uvium portula c a s trum Verdolaga de p]aya ; N ; beach succulent succulenta Dl Solanum e ri a nthum N Solanum S c hl ec h te ndalii N ; red berries like small tomatoes Nl; S yngonium sp N ; palmate leaves 5-foJias D2 Terminalia C atappa Almendro C ; comer PCRF Cell 1 nr septic tank ; tree Thrinax radiata Chit N ; palm used for thatching T ypha doming e nsi s Tule ; cattail N ; to 3-4 m Nl: Vigna elegan s N ; vine 3-leaves purple D2 flowers NI Vigna lut e o la N ; yellow flower otherwise similar to V. elegans ( 77 ) Nl; Viguiera d e nt a t a N D2 Washingtoni i robu s ta Washingtonii palm C : palm tree ; sharp thorns on fronds Nl Wedelia trilobata N ; vine yellow flowers Xanthosoma ro se um mafata ; taro N ; starchy root ; soft-leaved and elephant ears more curved leaf form of taro 'Zamia purpura ce us C ; purple flowering shrub NI Zephyranth es L indl ey ana C ; thin, short blades grass-like with pink flower Plant species identified by Edgar F Cabrera Chetumal Q.R. on surveys in May and December 1997, and July 1998 Code for column 2 Dl = dead or not found in December 1997 survey but present in May 1997 survey ; NI = new in December 1997 survey ; D2 = dead or not found in July 1998 survey N2 = new in July 1998 survey Botanic names : Cabrera Martinez (1987 ), UNAM ( 1994 ), Brummitt ( 1992 )

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50 45 ---------"C 40 .................. (1) .; .:. i 35 :2 II) (1) c:; 30 (1) C. II) -O 25 ......................... ....... ... (1) .c E :::, 20 C: (1) > .:. !!! :::s E :::s (.) -+System 1 1 st treatment compartment -aSystem 1 2nd treatment compartment -ASystem 2 1st treatment compartment --M-System 2, 2nd treatment compartment .................................................. ...................................... ___ o~-------------------------------------9 17 25 33 41 49 57 65 73 81 89 97 105 113 121 129 137 145 153 161 169 177 185 193 201 209 217 225 233 Number of observations in transect, May 1997 Figure 3-11 Species-area curves for each of the four wetland treatment cells May 1997 data -....) 0

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50 45 "C 40 ..... Cl) ..:: .:; C: Cl) 35 ........ ...... . ....................... ................. ............ .... ................ .............................. -:2 1/) .~ U 30 Cl) a. 1/) O 25 L. Cl) .c E :, 20 C: Cl) > .:; _!!! 15 :, E :, (.) 10 -+System 1, 1 st treatment compartment ----aSystem 1, 2nd treatment compartment -Ii-System 2, 1st treatment compartment -MSystem 2 2nd treatment compartment o~--------------------------------------10 19 28 37 46 55 64 73 82 91 100 109 118 127 136 145 154 163 172 181 190 199 208 217 226 235 244 Number of observations in transect, December 1997 Figure 3-12 Species-area curves for each of the four wetland treatment cells December 1997 data

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, 1 50 ..-----------------------------------------------, 45 40 'C 11) !E 35 C: 11) :2 l3 30 u 11) a. II) .... o 25 ... 11) .0 E :, c: 20 11) > "' :i E 15 :, u 10 5 0 IIIHIIIIIIIIIIIIIIIIIIIIIIIHIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIHIIII II IIIIIIIIIIIIIIIIIIIIIHIIIIIIIIIIIIIIHIIHIIIIIIIIHHIHlltHIIHllllHlllllllHIIIHlltHIIIHiltHIIIIIIIIHIIHHIIHHIIIIIHlllllll M -m M -m m m m m N Number of observations In transects, July 1998 F igure 3 -13 Sp e cie sarea curve s for e ach of the four wetland treatment cells, July 1998 d a ta. 8 -W ~ tland system 2 Cell 1 __._ Wetland system 1 Cell 1 -M-Wetland system 1 Cell 2 ~ _Wetl~n_d_ ~YS!~~ ~ Cell 2 -.l N

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70 ~-----------60 "C 50 ., C Cl) :'Q Ill Cl) -~ 40 a. Ill 0 Cl) .0 E Jo ::, C Cl) > :;:. Ill "S 20 ...... ..... (.) 10 ..... -........... ......... ...... ....................... .............. ................ .............................. ................. .......... ............................. ....... .. 0 ..,___ ____________________________________ __, Number of observations in transect, May 1997 Figure 3-14 Species-area curves for the 50.6 m2 wetland unit (system I) and the 81.2 m2 wetland (system 2), May, 1997. Transects counted 482 individuals in each system -+-Wetland treatment system 1 -Wetland treatment system 2

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74 the inclividual wetlands (F igure 3-15) although overall number of species present in both wetlands increased slightly (from 68 to 70 species) Many of the species no longer present were low understory shrubs while almost half the newly present species were native vines In July 1998 System 1 lost an additional 10% of species with a total of 44 species while System 2 remained constant at 57 (Figure 3-16 ), although again both numbers included a loss of some previously present species and establishment of new species (Table 3-1 ). Comparison with natural ecosystems In December 1997 transects with 1000 observations showed 73 species present in the inland tropical forest ecosystem and 17 species in the natural mangrove wetlands compared with the 70 species found in the constructed wetland treatment systems (Figure 3-17). Table 3-2 lists the species found in the mangrove and Table 3-3 presents the species found in the forest ecosystem Figure 3-18 compares number of species in treatment wetland systems 1 and 2 with number of species found in the transects through forest and mangrove ecosystems The wetlands had diversity of plant species comparable to that found in nearby forest ecosystems and a much greater number of species than were found in the adjacent mangrove wetlands Dominance Dominance was assessed through species relative frequency Shannon diversity index percent cover estimate of areal coverage and importance value

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60 ,--------------------------------------~ 50 0 30 Lo Cl) .0 E :::, C: Cl) > .:; 3 20 E :::, (.) 10 .... 0 _________________________________________ _] figure 3-15 Species-area curves for the 50 6 m2 Yucatan wetland (system 1) and the 81.2 m2 wetland (system ~), December, 1997 Transects counted 500 individuals in each system -+-Wetland treatment system 1 --0-Wetland treatment system 2

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60 ~-------"-----------------------------50 b 30 ... C1) .c E :l C: C1) > +a nl :i 20 E :l (.) 0 f-igure 3-16 Species-area curves for the 50. 6 m2 Yucatan wetland (system I) and the 81.2 m2 wetland (system 2), July, 1998. Transects counted 500 individuals in each system. r:+=viet1and syste~ 1 j ~!land system 2 J

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80 ~-----------------------------~ 70 ....... ....... 'O 60 (1) I;: ::, C: (1) :!2 111 50 (1) c:; (1) a. Ill .... 0 40 ..... ... (1) .0 E ::, C: 30 .:; ffl 3 E ::, (.) 20 o'I. ______________________ ..... 1 55 109 163 217 271 325 379 433 487 541 595 649 703 757 811 865 919 973 Figure 3l 7 Comparison of species richness between treatment wetlands, mangrove wetland and forest ecosystems, December 1997. Transects were 1000 individuals from each system. -----------+-Mangrove Wetland -a-Inland Tropical Forest ~Constructed wetland systems -.J -.J

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78 Table 3-2 Species list: mangrove wetland ecosystem, 8 December 1997 Species identified by Edgar Cabrera, Chetumal, Q R. Name of Species Acrostichum danaefolium Anthrurium Schlectendalii Chlorophora tinctoria Conocarpus erecta Cyperus ligularis Diospyros cuniata Enriquebeltrania cientifola Jpomoea indica Laguncularia racemosa Piendia aculeata Rhabdadenia biflora Rhizophora mangle Selenicereus Donkelaarii Selenicereus testudo Solanum Schlechtendalii Thrinax radiata Yithecellobium do/le Botanic names : Cabrera, Martinez (1987), UNAM (1994), Brummitt (1992)

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79 Table 3-3 Species list of inland forest near Aktnnal, Q.R. 9 December 1997 Species identified by Edgar Cabrera, Chetumal, Q .R. Species Name Acacia Collinsii / Acacia dolycostachia Acacia Gaumeri Acacia pennatula Amyris elem/era Anthurium Schlechtendalii Astronium graveoleus Ayenia pusi/la Bauhinia divaricata Beaucarnea ameliae Bromelia alsodeii Brosimum Alicastrum Bursera Simaruba Caesalpinia Gauneri Calocarpum acuminata Cenchrus ciliaris Chamaedorea Seifrizii Coccoloba acapu/censis Coccoloba diversifolia Coccoloba spicata Coccothrinax readea Dactyloctenium aegypticum Desmodium inconun Digitaria decumbens Diospyros veracruzensis Drypetes /ateriflora Eleusine indica Esenbeckia Berlandieri Galactia striata Gouania lupuloides Grass sp. Gymnopodium jloribundun Helicteris baruensi s Hevea obovata Hompea trilobata Jchnanthus lanceolatus Jacquemontia nodifl ora Species Name Karwinskyia Humboldtiana Lantana camara Lesaea divericata Malpighia amarginata Malvaviscus arboreus Manilkara z apodilla Melanthera nivea Melochia tomentosa Microgramma nitida Neea tenuis Ocimum micranthum O/ira yucatana Oncidium sp Otopappus guatemalensis Parthenium hysterophorus Paullinia pinnata Petrea volubilis Phyllanthus macriorus Piendia acileata Piscidia piscipula Plumeria obtusa Priva lapulacea Psychotria nervosa Sebastiania adenophora Selenicereus testuda Senna racemosa Sida acuta Spermacoce tetracera Talisia olivaeformis Themeda microntha Thevetia Gaumeri Thouinia paucidentata Thrinax radiata Unknown vine Veronia cinerea Vitex Gaumeri Botanic names: Cabrera Martinez (1987), UNAM (1994), Brummitt (1992)

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80 ~-----------------::-------------------, "C Q) I;: +: C: C1l :E 70 Cll 50 C1l u C1l a. Cl) .... O 40 L. C1l ..0 E :::J C: Q) > +: ra 3 E :::J (..) 20 -+Mangrove Wetland -G-lnland Tropical Forest -.-wetland treatment system 1 -M-Welland treatment system 2 --. -. ---53 105 157 209 261 313 365 417 469 521 573 625 677 729 781 833 885 937 989 Figure 3-18 Comparison of species richness between mangrove, forest and each treatment wetland Transects counted 1000 individuals in mangrove and forest, and 500 each in wetland systems 1 and 2. 00 0

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81 Shannon diversity index Shannon diversity indices for the wetlands (Table 3-4) confirmed that there was relatively high diversity in both constructed wetlands In May 1997 wetland System 2 with a with a Shannon diversity of 4.59 (base 2), 1.38 (base 10) was higher than wetland System 1 whose diversity was 4.17 (base 2) 1.25 (base 10) However by December 1997 their indices were far closer with System 1 at 4 .52 (base 2) and 1.36 (base 10) and System 2 at 4.49 (base 2) and 1.35 (base 10) In July 1998 Shannon diversity had increased and remained very similar between the two wetland systems. Wetland System 1 had an index of 4 .81 (base 2) and 1.45 (base 10) while wetland System 2 had a diversity index of 4 .85 (base 2 ) and 1.46 (base 10) Comparing the treatment wetlands with the nearby natural ecosystems (Table 3-5) shows that the tropical forest ecosystem was about 7% more diverse since it had a Shannon diversity index of 5 35 (base 2) and 1.61 (base 10) On the other hand, the constructed wetlands were far more diverse than the natural mangrove wetlands which had a Shannon diversity of 1.49 (base 2) and 0.45 (base 10), only about 30% that of the treatment wetlands Plant cover Calculation of species cover in each wetland treatment cell is shown in Table 3-6 Table 3-7 and Table 3-8 These observations demonstrate that overall plant coverage was higher in the first treatment cells of both wetland systems in May 1997 Plant cover in wetland System 1 Cell 1 averaged 85% compared to 74% in Cell 2 and in wetland System 2 Cell 1 plant cover averaged 91 %, while in Cell 2 plant cover was 48% of ground surface in the quadrats By December 1997 coverage was equal between cells 1 and 2 of wetland

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82 Table 3-4 Shannon diversity indices for constructed wetland systems based on May 1997 December 1997 and July 1998 surveys Wetland location Date System 1 Cell 1 May 1997 December 1997 July 1998 System 1 Cell 2 May 1997 December 1997 July 1998 System 2 Cell 1 May 1997 December 1997 July 1998 System 2 Cell 2 May 1997 December 1997 July 1998 System 1 (whole) May 1997 December 1997 July 1998 System 2 (whole) May 1997 December 1997 Jul y 1998 Shannon diversity index base 10 1.22 1.26 1.36 1 29 1.32 1.42 1.42 1.26 1.43 1.35 1.29 1.36 1.25 1.36 1.45 1.38 1.35 1.46 Shannon diversity index base 2 4 06 4.19 4 52 4.27 4.39 4 .71 4 72 4 .19 4 74 4.47 4.27 4 52 4 .13 4 52 4 .81 4.58 4.49 4 85

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83 Table 3-5 Comparison of Shannon diversity indices for constructed wetlands vs. natural mangrove and tropical forest ecosystems of the study area based on December 1997 and July 1998 survey data Ecosystem Constructed wetland System 1 Constructed wetland System 2 Both constructed wetlands Mangrove ecosystem Tropical forest ecosystem Shannon diversity base 10 Shannon diversity base 2 -------------~---------1.45 4 .81 1.46 4.85 1.51 5 .01 0.45 1.49 1.61 5.35

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84 Table 3-6 Relative cover in the wetland system cells based on 0 25 sq m quadrat analysis, May 1997 Wetland system and Plant species Relative cover Rank cell by species --System 1 Cell 1 C anna edulis 37.3% 1 Sesuvium portulacastrum 12.6% 2 Typha domingensis 11% 3 A locasia macrorhiza 9 5% 4 Paspalum virgatum 8 7% 5 Solanum erianthum 8 .2% 6 Nerium oleander 6 5% 7 System 1 Cell 2 C anna eduli s 25.2% 1 Melanthera nivea 12.2% 2 Hymenocallis littoralis 9% 3 Sesuvium portulacastrum 8.4% 4 Washingtonii robusta 8% 5 C hrysobalanus icaco 5 5% 6 C yperus ligulari s 4 .6% 7 System 2 Cell 1 C anna edulis 13.8% 1 Typha domingensis 13.1% 2 Pluchea odorata 9.7% 3 Sesuvium portulacastrum. 9% 4 Ipomoea Pes-caprae 6 .6% 5 Ageratum littorale 6.2% 6 E leocharis cellulosa 5 .9% 7 System 2 Cell 2 C anna edulis 28 .7% 1 Typha domingensis 17% 2 Nerium oleander 12.9% 3 Sesbania emerus 8.8% 4 So/anus erianthum 7% 5 E leocharis cellulosa 6.4% 6 Paspalum virgatum 4.7% 7 (tie) Alocasia macrorhiza 4 .7%

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85 Table 3-7 Estimates of area coverage including canopy, of dominant plants in the wetland treatment cells, May 1997. Total area of each cell in System 1 is 25.3 square meters, and area of each cell in System 2 is 40 6 square meters Wetland system and Plant species Total Percentage of Rank cell coverage total area {m22 System 1 Cell 1 Canna edulis 5 35 20 9% 1 Typha domingensis 2 .95 11.7% 2 Alocasia macrorhiza 1.58 6.2% 3 Solanum erianthum 1.1 4.3% 4 Xanthosema roseum 0 8 3 2% 5 (tie) Musasp. 0 8 3 2% Phyla nodiflora 0.6 2 4% 7 Pluchea odorata 0.5 2% 8 (tie) Conocarpus erecta 0 5 2% System 1, Cell 2 Canna edulis 3.95 15.6% 1 Washingtonii robusta 3.15 12. 5% 2 Cyperus ligularis 2.2 8.7% 3 Hymenocal/is littora/is 2.1 8.1% 4 Typha domingensis 1.9 7.5% 5 Acrostichum danaefolium 0 9 3.6% 6 lpomoea Pes-caprae 0 8 3.2% 7 Sesuvium portulacastrum 0 7 2 8% 8 System 2, Cell 1 Typha domingensis 4.85 11.9% 1 Canna edulis 3 .73 9.2% 2 Sesuvium portulacastrum 2.5 6.2% 3 Nerium oleander 2.45 6 .1% 4 Washingtonii robusta 1.9 4.7% 5 Pluchea odorata 1.75 4.3% 6 Ageratum littorale 1.6 3.9% 7 Phyla nodiflora 1.4 3.4% 8 System 2, Cell 2 Typha domingensis 8 .25 20.3% 1 C anna edulis 3 .75 9.2% 2 Solanum erianthum 3 0 7.4% 3 Eleocharis cel/ulosa 1.5 3.7% 4 Sesbania emerus 1.15 2.8% 5 Sesuvium portulacastrum 1.0 2 5% 6 Nerium oleander 0 95 2.3% 7 Alocasia macrorhiza 0 5 1 2% 8 (tie) Musa se.0.5 1.2%

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86 Table 3-8 Estimates of area coverage, including canopy, of dominant plants in the wetland treatment cells, December 1997 and July 1998. Total area of each cell in System 1 is 25 3 square meters, and area of each cell in System 2 is 40 6 square meters Wetland system and Plant species Total Percentage of Rank cell coverage total area m2 System 1 Cell 1 December 1997 Washingtonii robusta 3.1 12.3% 1 Typha domingensis 2 6 10.4% 2 Conocarpus erecta 2.4 9.5% 3 Nerium oleander 1.6 5.9% 4 (tie) Musasp. 1.6 5.9% Alocasia macrorhiza 0.9 3.6% 6 Pluchea odorata 0 .8 3.2% 7 (tie) Sesuvium portulacastrum 0 .8 Xanthoseum roseum 0 .8 July 1998 C onocarpus erecta 7 0 28% 1 Washingtonii robusta 6 0 24% 2 Alocasia macrorhi z a 4 8 19.2% 3 Musasp. 4 2 16.8% 4 Typha domingensis 2 .8 11.2% 5 Nerium oleander 2 0 8% 6 C occo/oba uvifera 1.8 7.2% 7 Xanthosema roseum 1.3 5 .2% 8 System 1, Cell 2 December 1997 Washingtonii robusta 3.3 13% 1 C anna edulis 2 0 7 9% 2 Hymenocal/is /ittoralis 1.7 6 7% 3 Musasp. 1.6 6 .3% 4 Typha domingensis 1.3 5.1% 5 Oleander nerium 0.9 3 6% 6 Acrostichum danaefolium 0 .8 3.2% 7 (tie) Cy perus /igularis 0 .8 C hrysobalanus icaco 0 8 July 1998 Washingtonii robusta 14.4 57 6% 1 Hymenocallis littoralis 3 9 15. 6% 2 Nerium oleander 2.4 9 6% 3 Ipomoea Pes-caprae 1.9 7 6% 4 Typha domingensis 1.4 5 6% 5 Terminalia Catappa 0 7 2 6% 6 Pedilanthus tithymaloides 0.6 2 .2% 7 C occoloba uvifera 0.4 1.4% 8 System 2 Cell 1 December 1997 Washingtonii robusta 5 6 13.9% 1 Musase,. 2 4 5.9% 2 { tie l

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Wetland system and cell July 1998 System 2, Cell 2 December 1997 July 1998 87 Plant species Typha domingensis Alocasia macrorhiza Nerium oleander Sesuvium portulacastrum Acalypha hispida Cissus erosus Washingtonii robusta Typha domingensis Nerium oleander Cissus erosus Musa sp. Xanthoseum roseum Alocasia macrorhiza Cissus trilofolia Typha domingensis Alocasia macrorhiza Canna edulis Xanthoseum roseum Musa sp. Washingtonii robusta Vigna elegans Nerium oleander Nerium oleander Washingtonii robusta Typha domingensis Xanthoseum roseum Alocasia macrorhiza Solanum Schlechtendalii Carica Papaya Acrostichum danaefolium -------------------Total coverage (m2) 2.4 1.9 1.4 1.4 1.3 1.2 9.4 4.4 4.4 3.6 3.2 3.0 1.3 1.2 3.9 2.3 2.1 1.7 1.6 1.6 1.1 I.I 4.9 4.8 3.6 3.5 3.1 2.0 1.8 1.7 Percentage of total area 4.7% 3.5% 3.2% 2.9% 23.2% 10.8% 10.8% 8.9% 7.9% 7.4% 3.2% 3.0% 9.6% 5.7% 5.2% 4.2% 3.9% 2.7% 0.9 12.1% 11.8% 8.9% 8.6% 7.6% 4.9% 4.4% 4.2% Rank 4 5 (tie) 7 8 1 2 (tie) 4 5 6 7 8 1 2 3 4 5 (tie) 7 (tie) 2.2% 9 1 2 3 4 5 6 7 8

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88 System 2 (both around 70%) while Cell 1 of System 1 at 94% cover was still far ahead of Cell 2 with 76%. Estimates of area covered by dominant species in each wetland treatment cell were also done by visual inspection and estimation of cover by each species in May 1997, December 1997 and July 1998 These results (Tables 3-7 and Table 3-8) show that dominance decreased between May and December 1997. In May 1997, the top 4 species covered 38%, 47% 37% and 37% in individual treatment cells, while in December 1997, the top four species covered 32%, 28% 24% and 21 % of the wetlands For the top 8 species combined coverage in May 1997 was 54%, 56%, 50%, and 49% while in December 1997, coverage had fallen to 54% 49%, 38% and 38%. By July 1998 the top four species in each treatment cell had greater canopy cover (71 %, 83%, 45% and 33%). This reflected the growth and increased canopy of trees and large palms such as Washingtonii robusta C onocarpus erecta, and Musa sp Plant frequency The frequency of species in the treatment wetlands was evaluated in May 1997, December 1997 and July 1998 (Table 3-9) The 8 plant species with highest relative frequency in the treatment cells of each wetland system in May and December 1997 are shown in Table 3-9 These results show that Canna edulis and Typha domingensis were the two most frequently observed plant species overall in May 1997 but that some differences are seen in the wetland cells In wetland System 2, Cell 1 Hymenocallis littoral is is the second most frequent species and a number of different species appear in the top seven species depending on the wetland area By December 1997, the pattern had changed somewhat with Canna edul is coverage

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89 Table 3-9 Frequency rankings of dominant plants in constructed wetlands in May 1997 December 1997 and July 1998 transects. ........ ., ..... -~ ; .. Wetland Date location Systeml May Cell 1 1997 July 1998 System 1 May Cell 2 1997 Most frequent species Canna edulis Typha domingensis Alocasia macrorhiza Sesuvium portulacastrnm Hymenocallis littoralis Solanum erianthum Paspalum virgatum Nerium oleander Typha domingensis Alocasia macrorhiza Hymenocallis littoralis Canna edulis Solanum Schlechtendalii Scindapsus aureus Washingtonii robusta Pluchea odorata Canna edulis Hymenocallis littoralis Typha domingensis A crostichum danaefolium Sessuvium portulastrum Cyperns ligularis .. .. .. .. Percent Date Mostfrequent Percent frequency species frequency Dec. Typha 25.4 1997 domingensis 20.3 12.5 Alocasia 11.4 macrorhiza 9.1 Sesuvium 9.6 portulacastru m 8.2 Hymenocallis 8.0 littoral is 5.6 Canna edulis 7.1 3.9 Nerium 3.8 oleander 3.4 C onocarpus 2.6 erecta 2 6 Melanthera 2 6 nzvea 16.8 6.4 5.6 5.2 4 8 4.4 3.6 3.6 Dec. 1997 25.2 Canna edulis 17.5 14.0 Typha 10.8 domingensis 8.8 Hymenocallis 7.6 littoralis 4.4 Acalypha 7.2 hispida 4.4 Washingtonii 4.4 robusta 3.6 Melanthera 4.0 nivea

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90 Wetland Date Most frequent Percent Date Most frequent Percent location species frequency species frequency Chrysobalanus 3.2 Alocasia 4 0 icaco macrorhiza Chamaesyce 2.4 Cyperus 4 0 hypericifolia ligularis July Hymenocallis 1998 littoralis 9 2 Canna edu/is 8.4 Typha domingensis 8.0 Ipomoea Pes-caprae 8 0 Washingtonii robusta 6.4 Alocasia macrorhiza 4.4 Nerium oleander 4.4 Phyla nodiflora 4.0 System 2 May Dec Typha 29 7 Cell 1 1997 Typha domingensis 19.4 1997 domingensis C anna edulis 15. 1 Canna edulis 12. 7 Nerium oleander 5.2 Nerium 6 6 oleander Ageratum littorale 3.9 Xanthoseum 3.4 roseum Sessuvium 3.4 Sessuvium 3 1 portulastrum portulastrum Phyla nodiflora 3.4 lpomoea Pes-3.1 caprae Ludwigia octavalis 3.0 Cissus erosus 2 2 Pluchea odorata 3.0 Acalypha 2.2 hispida Ageratum 2 2 littorale July Typha domingensis 1998 17.6 Cis sus erosus 8.4 Alocasia macrorhiza 6.4 Nerium oleander 5.2 Washingtonii 4.8 robusta Sesuvium 2.8 portulacastrum Wetland Date Most frequent Percent Date Most frequent Percent

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91 location species frequency spec1es frequency Bravaisia tubiflora 2.4 lpomea indica 2.4 System 2 May Dec Typha Cell 2 1997 Typha domingensis 21.6 1997 domingensi 28.6 C anna edulis 19.2 C anna edulis 12. 1 Solanum erosanthum 7 0 Nerium 7 1 oleander E leocharis cel/ulosa 6.4 Alocasia 3.8 macrorhiza Alocasia macrorhiza 4.7 Vigna elegans 2.9 Paspalum virgatum 4 7 Sessuvium 2 9 portu/astrum Hymenocallis 4.1 Eleocharis 2 9 littoralis cellulosa Phyla nodiflora 4.1 Hymenocallis 2 9 littoralis Washingtonii robusta 4 1 Aca/ypha 2 0 hispida C estrum diurnum 4.1 July 1998 Typha domingensis 20.8 Nerium oleander 8.4 Xanthoseum roseum 4.8 Alocasia macrorhiza 4 8 C anna edu/is 4.4 Pluchea odorata 4.4 Scindapsus aureus 4.3 Hymenocallis 3 6 littoralis Rhabdadenia biflora 3.3

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92 declining ( from 17% overall to 12% ), T ypha doming e nsis increasing ( from 15% to 22%) and other cells showing changes in species and their frequency The cover by vines was greater in System 2 with Jpomo e a Pes-caprae C issu s e rosus and Vigna e legan s among the most frequently observed species. By July 1998 the decline of C anna eduli s accelerated, both in frequency and in size of individual plants as it became overtopped by a taller canopy Along with greater species richness System 2 was less heavily dominated by its most frequently observed plant species in May 1997 In System 2 Cell 1 the five most frequent species constitute 47% of total observations and in System 2 Cell 2, the top five are 52% By contrast in System 1 Cell 1 the top 5 are 60%, and in System 1 Cell 2 are 56% of total observations in May 1997. When considered as a whole in System 1 the top 5 species are 58.3% of observations while in System 2 the top 5 are 47 .7%. By December 1997 the situation had changed and the two wetlands were more comparable In System 2 s cells 1 and 2 the top 5 species constituted 56% and 55% of observations while in wetland System 1 the top five species represented 60% and 48% of observations In July 1998 the decrease in dominance continued, with the top 5 species constitute 42.4% of observations in System 2 and 37 2% in System 1 (Table 3-9 ) Rarely observed species are found in all cells of both systems but more are found in wetland System 2. In May 1997 in System 1 Cell 1 there were 10 species with only 2 observations and 9 with only 1 ; in System 1 Cell 2 there were 5 species with only 2 observations and 8 with only 1 ; in System 2 Cell 1 there were 11 species with only 2 observations and 9 with only l ; and in System 2 Cell 2 there were 12 species with only 2 observations and also 12 species with only 1 observation. In December 1997 System 1 Cell

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93 I had 9 species with 2 observations 5 species with 1 ; System 1 Cell 2 had 6 species with 2 observations 8 species with l ; while System 2 Cell l had 13 species with 2 observations 10 species with l ; and System 2 Cell 2 had 12 species with 2 observations and 16 with 1 In July 1998 System 1 Cell 1 had 4 species with 2 observations and 6 with one ; System 1 Cell 2 had 4 species with 2 observations and 3 with one System 2 Cell 1 had 12 species with 2 observations and 10 with one ; System 2 Cell 2 had 5 species with two observations and 14 with one Importance values Importance values for the plant species in the wetland systems were calculated combining their relative frequency ( from transect studies ) and their relative cover (from quad.rat analysis ) and dividing by two (Brower et al. 1991). Table 3-10 presents the Importance Value results which show that in May 1997 C anna e duli and Typha doming e nsi s were the two most important plant species overall as they occupied all but one of top two rankings in the four treatment cells In December 1997 T ypha remained the highest ranking species but now Washingtonii robusta was second overall Below that level there was some variability in which plants ranked highest in importance in each treatment cell. In July 1998 Typha remained the top species in the two system cells of System 2 but Washingtonii robu s ta and C onocarpus e recta were the top plants in each of System 1 s cells ( Table 3-10). Graphing the rank sequence of species from each system cell is a method of comparing dominance vs. evenness of systems (Brower et al 1991 ) Figure 3-19 Figure 320 and Figure 3-21 show that there was great similarity in the pattern of dominance / evenness for all four of the wetland treatment cells in May 1997 December

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94 Table 3-10 Importance value ranking of top eight species in each wetland treatment cell, May 1997 December 1997 and July 1998 surveys Values were computed by adding relative species frequency and relative species cover and dividing by 2. Maximum value is therefore 1.0, and total is 1.0 summing all species found in the treatment cell Wetland system and cell Survey date Plant species Importance Rank value System 1 Cell 1 Mayl997 C anna edulis 0.31 1 Typha domingensis 0 12 2 Sesuvium portulacastrum 0 .10 3 Alocasia macrorhiza 0 09 4 Paspalum virgatum 0.06 5 Solanum erianthum 0.06 6 Hymenoca/lis littoralis 0 05 7 Nerium oleander 0.04 8 Dec.1997 Typha domingensis 0 .15 1 Alocasia macrorhiza 0.08 2 Washingtonii robusta 0.08 3 Sesuvium portu/acastrum 0 07 4 C onocarpus erecta 0 06 5 Nerium oleander 0 05 6 Hymenoca/lis littoralis 0 05 7 C anna edulis 0.05 8 July 1998 C onocarpus erecta 0.13 1 Typha domingensis 0.12 2 Washingtonii robusta 0.10 3 Alocasia macrorhiza 0 10 4 Musasp. 0 07 5 Nerium oleander 0.06 6 Solanum Schlechtendalii 0 04 7 Hymenocal/is littoralis 0 04 8 System 1 Cell 2 May 1997 C anna edulis 0 25 1 Hymenocal/is littora/i s 0 .11 2 Melanthera nivea 0.07 3 Sesuvium portulacastrum 0 06 4 Typha domingensis 0.06 5 Acoelorhaphe wrightii 0 05 6 C hrysobalanus icaco 0 04 7 Acrostichum danaefolium 0 04 8 Dec.1997 C anna edulis 0 .14 1 Washingtonii robusta 0 .11 2 Typha domingensis 0.09 3

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95 Wetland system and cell Survey date Plant species Importance Rank value H y menocallis littoralis 0 08 4 A calypha hispida 0.05 5 Musasp. 0 05 6 C yperus ligulari s 0.04 7 Acrostichum danaefolium 0 04 8 July 1998 Washingtonii robusta 0 .25 1 Hymenocallis littoralis 0.11 2 lpomoea Pes-caprae 0 07 3 Typha domingensis 0.06 4 Nerium oleander 0 06 5 C anna edulis 0 04 6 A locasia macrorhiza 0.03 7 Solanum Schlechtendalii 0 03 8 System 2 Cell l May 1997 Typha domingensis 0.16 1 C anna edulis 0 14 2 Pluchea odorata 0 06 3 Sesuvium portulacastrum 0.06 4 Nerium oleander 0.05 5 Ageratum littorale 0 05 6 lpomoea Pes-caprae 0 05 7 Eleocharis cellulosa 0.04 8 Dec 1997 Typha domingensis 0 .19 1 Washingtonii robusta 0 .11 2 C anna edulis 0.08 3 Nerium oleander 0 06 4 Musasp. 0 05 5 Sesuvium portulacastrum 0 04 6 Alocasia macrorhiza 0.04 7 Acalypha hispida 0.03 8 July 1998 Typha domingensis 0 .14 1 Washingtonii robusta 0.14 2 C issus erosus 0.09 3 Nerium oleander 0.08 4 Musasp. 0.05 5 Alocasia macrorhiza 0 05 6 Xanthoseum roseum 0 05 7 Hymenocallis littoralis 0.04 8 System 2 Cell 2 May 1997 C anna edulis 0 24 1 Typha domingensis 0 19 2 Nerium oleander 0 08 3 Sesbania emerus 0.06 4

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96 Wetland system and cell Survey date Plant species Dec. 1997 July 1998 Alocasia macrorhiza Eleocharis cellulosa Paspalum virgatum Solanum erianthum Typha domingensis Canna edulis Alocasia macrorhiza Nerium oleander Vigna elegans Xanthoseum roseum Washingtonii robusta Musa sp. Typha domingensis Nerium oleander Washingtonii robusta Xanthoseum roseum Alocasia macrorhiza Solanum Schlechtendalii Acrostichum danaefolium Canna edulis Importance value 0.05 0.04 0.04 0.04 0.21 0.10 0.06 0.06 0.04 0.03 0.03 0.03 0.15 0.10 0.07 0.07 0.06 0.06 0.04 0.03 Rank 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8

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1/lCI) u 8. 1/l c "' ... Q. II 'o~ Cl) n:, :::, E ~i Cl) .... u ,g C: "' t:: 0 .01 0 Q, ---0 .001 -t---+----1f---+--+-+--+----1f---+---+-+--+--f---+---+-+--+--l---+---+-+--+--i-------_J 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Plant species in rank sequence Figure 3-19 Plant species in rank sequence oflmportance Value (IV) in the four wetland treatment cells,.May, 1997 data. Importance Value= (Frequency+ Cover)/2. -+-Wetland system 1, cell 1 -Wetland system 1, cell 2 ----6--Wetland system 2, cell 1 ~Wetland system 2, cell 2

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,,r QI 'i3 QI C. Cl) C: C? ca .,.. Q. II 'o~ QI ca ::, E ~i QI -CJ .s C: ca 0.1 .... 5 0 .01 C. .5 . ----................. -----..................... ......................... ............ -----0 001 ;--:2~--:3--4:~5--6~~7:---+8--91---+--+--+--+--l---+--+--+--+--l---+--+--J 1 0 1 1 12 13 14 15 16 17 18 19 20 21 22 Plant species in rank sequence...:_ Figure 3-20 Plant species in rank sequ e nce ofimportance Value (IV) in the four wetland treatment cells, December 1997 data Importance Value = (Frequency + Cover) / 2 ---+-Wetland system 1 cell 1 -Wetland system 1, cell 2 -A-Wetland system 2 cell 1 -M-Wetland system 2, cell 2

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1.000 ,---------------------------------------. -+-Wetland system 1, cell 1 -a--Wetland system 1, cell 2 >< co -lr-Wetland system 2 cell 1 -M-Wetland system 2 cell i .. 0 100 Ill~ Cl) o Cl) C. Ill ... C: co a. .... 0 Cl) ::::, iii > Cl) 0 010 CJ C: 0 C. E 0 .001 -t----i1---+--+--+---+--+----il---+--+--+---+--+-----l----+---+---+--+--+--1----+--_J 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Plant species in rank sequence Figure 3-21 Plant species in rank sequence of Importance Value (IV) in the four wetland treatment cell s, July 1998 d a ta Importance Value = (Frequency + Cover)/2

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100 1997 and July 1998 Distribution is somewhat more even in December 1997 as evidenced by a flatter shape to the graph lines than in the earlier and later measurements Leaf area index Data on the structure of vegetation in the wetlands monitored with leaf area index (LAI) are summarized in Table 3-11 Photographs of the wetlands illustrating canopy development are presented in Figures 3-22 to 3-25 The initial development of the canopy in the two wetlands was similar The overall LAI for the System 1 and System 2 wetlands were 4.04 28 and 3 89 29 in May 1997 However leaf area indexes were markedly different between the fust and second treatment cells The first cells of the two wetland systems averaged 5.56 0 27 By contrast the second cells were substantially lower averaging 2 33 0 19 (Table 3-11) By November 1997, after an additional six months growth, and July 1998, with an additional 14 months growth all cells had increased in LAI The difference between fust and second cells had considerably narrowed in System 1 and was no longer evident in System 2 Average LAI for System 1 had increased to 5 73 0.48 and System 2 was 6 38 0 .51 (Table 3-11) Leaf holes Leaf holes due to herbivory and other causes were measured in December 1997 and July 1998 (Table 3-12 Table 3-13) Overall estimates for the ecosystem were determined by multiplying leaf holes per species by species frequency The result was 4 .7% ofleaf material in the wetlands in December 1997 and 2 1% in July 1998 (Table3-12 Table 3-13)

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101 Table 3-11 Measurements of leaf area index in the treatment cells of the wetland systems, May 1997, December 1997 and July 1998. Values are given with standard error of the mean. May, 1997 ,1rt ... f!i'of' .,. ..: ... . ~-~;,~ ~},,,,:,!'\,,,: ;. ~ -~-4;\ ...... ;."I,. Wetland Unit No. of observations First Cell Second Cell Overall Wetland .. . . . . . . . . . . . . . . . . .... ... .. .. .. ... . . .. ~ ... .. .. ...... .. .. . ... . .. ... ..... ............ .. . . .... System 1 93 5.51 +/ -0.40 2.54 +/-0.23 4.04 +/-0.28 System 2 105 5.60 +/-0.36 2.33 +/0.19 3.89 +/-0.29 November 1997 ta. ..~11 ...,._",_~'" -i ..~1;.... .1;1 -1' .... , ..,.. ~~" ,.., ,,.lr.-.-;4', WW.t.illl , "-',:. ._. ., Wetland Unit No. of observations First Cell Second Cell Overall wetland System 1 System 2 July 1998 109 109 --~-~-. 6.22 +/0.4 4.24 +/0.43 5.23 +/0.31 5.76 +/ 0.36 4.9 -'r/-0.31 5.33 +/0.26 1 ,"4., --~,-..... :--< .. -.,.. ~" - .,.,._1 -""" ..-., ~u.~~. ... ....... ttift~~QC., ....,~._. ~--~ -_,.......------.Wetland Unit No. of observations First Cell Second Cell Overall wetland . . . . . . . . .. . . . . System 1 System 2 66 71 . . . . -. . . .. ..... .. .. .. .. ..... .. . --~.. ... .. .. .. .. . ..... -~ 6.68 0.46 6.38 0.48 4.77 0.55 6.39 0.54 5.73 +/0.48 6.38 +/0.51 ' -~-~1.r~ '~~ Ide....,__~~,_.., .., ., -tcJtel..4*~+' lit4~ "' "'~ W 11-1 q, .... -~ , ._ "ffl""'' ,t,,<:,, ... n ,.,, ...... ,.._. .. ..-..., . .... ,.,uJ ,-.1,,.< , ,l: .-~ V :;;.e:i~ !-ii~--. ii0$:tie ..,.,.,_,.,.,..,._,, ~-

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Fig ue 3-22 Photogrpah of wetland systems in Akumal shortly after planting August 1996. System 1 is in foreground and System 2 in background in front of edge of mangrove wetland ....... 0 N

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Figure 3-23 Photograph of vegetation in wetland system l May 1997 ...... 0 v,)

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Figure 3-24 Photograph of vegetation in wetland system 1, December 1997

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105 I \ ' \ . .,\ ,, t Figure 3-25 Photograph of vegetation in wetland system 1 July 1998 -----

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106 Table 3-12 Leaf holes in the wetland treatment units, December 1997 Name of Species Percent Leaf Species Holesa Frequencyb Contributionc Canna edulis 0.15 0.123 0 018 Acalypha hispida 0 1 0.036 0 004 Hymenocallis littoralis 0.04 0.052 0.002 Lantana involucrata 0.16 0.015 0.002 Melanthera nivea 0.074 0 029 0 002 Solanum Schlechtendal ii 0.11 0.016 0.002 Alocasia macrorhi z a 0.026 0 047 0.001 Cissu erosus 0 .11 0 006 0.001 Ci sus sicyoides 0 26 0 002 0.001 Cyperus ligularis 0 05 0 017 0 .001 Eupatorium albicaule 0 .19 0 006 0.001 Jpomea indica 0.15 0 005 0.001 Jpomoea Pes-caprae 0.042 0.024 0.001 Phyla nodiflora 0.15 0.005 0.001 esuvium portulacastrum 0.014 0.046 0.001 Terminalia Catappa 0 058 0 009 0 001 Vigna elegans 0.1 0 013 0.001 Wa hingtonii robusta 0.03 0.022 0.001 Acrostichum danaefolium 0.014 0 014 0 000 Ageratum littorale 0.04 0 008 0.000 Anthur ium schlechtendall ii 0 012 0 005 0.000 Anthurium sp. 0.03 0 005 0.000 Asclepias curossavica 0.01 0.001 0.000 Bidens pilosa 0.018 0.003 0.000 Bravaisia tubiflora 0.07 0.005 0.000 Cae alpinia pulcherrima 0 014 0.003 0.000 Caladium bicolor 0.02 0 007 0.000 Carica Papaya 0 .05 0 .001 0 000 hamaedorea Seifri z ii 0 012 0 001 0.000 Chamaesyce hypericifolia 0 038 0 004 0.000 hrysobalonus icaco 0 002 0.013 0.000 Citrus aurianthum 0 014 0 .001 0.000 Coccoloba uvifera 0 048 0.008 0.000 Conocarpus erecta 0 02 0 007 0 000 Corchorus siliquosus 0.07 0.005 0 000

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107 Name of Species Percent Leaf Species Holes8 Frequencl Contributionc Desmodium incanum 0.12 0.002 0.000 Distichlis spicata 0 0.006 0.000 Eleocharis cellulosa 0.01 0.006 0.000 Flaveria linearis 0.05 0.004 0.000 Iresine celosioides 0.03 0.002 0.000 Ixora coccinea 0 0.007 0.000 Kalanchoe pinnata 0.008 0.003 0.000 Lochnera rosea 0.09 0 .001 0.000 Malvaviscus arboreus 0 022 0.003 0.000 Nerium oleander 0 0 052 0.000 Nopalea cochinillifera 0.008 0.001 0.000 Paspalum virgatum 0.014 0.018 0.000 Pedilanthus tithymaloides 0.03 0.011 0.000 Pelliciera alliacea 0.09 0 002 0.000 Philodendron sp 0 004 0.001 0.000 Pluchea odorata 0 046 0.009 0.000 Psychotria nervosa 0.02 0.001 0.000 Rabdadenia biflora 0.08 0 003 0.000 Rhoeo discolor 0.02 0 009 0.000 Sansevieria triasiate 0.01 0.010 0.000 Scindapsus aureus 0.03 0 008 0.000 Selenicereus dontielarii 0 0 001 0 000 Senna biflora 0 004 0.001 0.000 Syngonium sp. 0.07 0.002 0.000 Thrinax radiata 0 0 004 0.000 Typha domingensis 0.002 0.220 0.000 Vigna luteola 0.07 0.001 0.000 Viguiera dentata 0 06 0.001 0 000 Wedelia trilobata 0.1 0 001 0.000 Xanthosoma roseum 0 014 0 026 0 000 Zamia purpuraceus 0 0 005 0 000 Zephranthes Lindleyana 0 014 0.005 0 000 Total 1.000 0.047 a Portion of measured leaves of one species which showed holes b Frequency is based on the frequency of the species in the wetlands c Product of percent holes and species frequency.

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108 Table 3-13 Leaf holes in the wetland treatment units, July 1998 data Name of Species Solanum Schlechtendalii Alocasia macrorhiza Nerium oleander Sesuvium portulacastrum Bidens pilosa Canna edulis Hymenocallis l ittoralis Phyla nodiflora Pluchea odorata Scindapsus aureus Typha domingensis Xanthosoma roseum Acrostichum danaefolium Ageratum littorale Aloe vera Alternanthera ramossissima Anthurium schlechtendallii Anthurium sp Bravaisia tubiflora Caesalpinia pulcherrima Caladium bicolor Capraria biflora Carica Papaya Chamaedorea Seifri zii Chamaesyce hypericifolia Chrysobalonus icaco Cissus erosus Cissus sicyoides Citrus aurianthum Coccoloba uvifera Conocarpus erecta Corchorus siliquosus Cordia sebestena Crinum amabile Desmodium tortuosum Distichlis spicata ------Percent Holes a 0.11 0 028 0 028 0 054 0 06 0.022 0 .01 0 06 0 034 0.018 0 004 0.05 0 02 0 04 0.028 0 014 0 014 0.018 0.014 0 0 0.04 0.024 0 002 0 0 .01 0 0 004 0 004 0 034 0.018 0 05 0.004 0 004 0.014 0 Leaf Species Frequencl Contributionc 0.038 0.004 0.055 0 002 0 060 0 002 0 030 0 002 0.012 0 001 0.055 0 .001 0.062 0 .001 0.017 0.001 0.028 0.001 0 036 0 .001 0.158 0.001 0 028 0 001 0 018 0.000 0.010 0.000 0 003 0 000 0.002 0.000 0 006 0.000 0.003 0.000 0 023 0 000 0 .001 0 000 0.007 0 000 0.003 0 000 0.001 0 000 0 002 0.000 0.007 0.000 0 006 0 000 0.029 0.000 0 006 0 000 0.003 0.000 0.013 0 000 0.020 0 000 0.004 0.000 0.001 0 000 0 002 0.000 0.006 0 000 0.005 0.000

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109 Name of Species Percent Leaf Species Holes a Frequencl Contribution c Eupatorium albicaule 0 018 0 007 0 000 Flaveria lineari 0 0 001 0.000 Jpomea indica 0 004 0 006 0.000 Jpomoea Pes-caprae 0.014 0.033 0.000 Jxora coccinea 0.034 0.009 0.000 Kalanchoe pinnata 0.04 0 002 0 000 Leucaena glauca 0 0.002 0 000 Mimosasp. 0 .01 0.003 0 000 Malvaviscus arboreus 0 0.004 0.000 Musa sp. 0 004 0.015 0 000 Nopalea cochinillifera 0.03 0.001 0 000 Paspalum virgatum 0.02 0.003 0 000 Pedilanthus tithymaloides 0 004 0.014 0.000 Philodendron sp 0 025 0.001 0 000 Phylanthus niruri 0.03 0.001 0.000 Psychotria nervosa 0 014 0 003 0 000 Rabdadenia biflora 0 0 008 0.000 Rhizophora mangle 0 0 003 0.000 Rhoeo discolor 0.01 0 017 0.000 Sansevieria triasiate 0.008 0 009 0 000 Senna biflora 0.004 0.003 0 000 Terminalia Catappa 0 004 0.017 0.000 Thrinax radiata 0 07 0 006 0 000 Vigna luteo/a 0 0.003 0 000 Washingtonii robusta 0 004 0 044 0.000 Wedelia trilobata 0.004 0.008 0 000 Zamia purpuraceus 0 0.004 0 000 Zephranthes Lindleyana 0.05 0 007 0 000 Total 1.00 0.021 --a Portion of measured leaves of one species which showed holes b Frequency is based on the frequency of the species in the wetlands c Product of percent holes and species frequency

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110 More holes were found in Cissus sicyoides (26%), Eupatorium albicaule (19%), Lantana involucrata (16%), Canna edulis (15%), Ipomea indica (15%), Phyla nodiflora (15%), Solanum schlectendalionum (11%) and Cissus erosus (11 %) Because of its abundance Canna edulis (1.8%) was responsible for over one-third of the total. Eighteen species accounted for 89% of total herbivory in the wetlands in December 1997 (Table 3-12). By July 1998, when average leaf holes were 1.8%, the leading species were Thrinax radiata (7%), Bidens pilosa (6%), Phyla nodiflora (6%), Sesuvium portulacastrum (5.4%), Xanthoseum roseum (5%) and Corchorus siliquosus (5%). Leaf holes were more evenly divided among species than in December 1997, with Solanum Schlechtendalii contributing the highest individual amount ( 4%), while Alocasia macrorhiza, Sesuvium portulacastrum, and Nerium oleander each contributed 2% (Table 3-13) Surface organic matter Results of analysis of organic matter on the gravel surface of treatment systems are presented in Figure 3-26. Average organic matter surface material was initially 1582 242 g m-2 (dry weight). In July, 1998, after twenty three months of wetland operation since planting, surface organic matter averaged 1458 254 g m-2 in System 1 Cell 1, 1515 373 g m-2 in System 1 Cell 2, 1210 81 g m-2 in System 2 Cell 1, and 1610 242 g m-2 in System 2 Cell 2. The overlap of the standard error bars shows that these values are not statistically different from the starting value T-tests for samples of unequal variance show their probabilities to be p<0.73, p<0.96, p<0 36 and p<0.20 respectively indicating that statistically there was no significant change.

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111 2000 e 1400 en 1200 C'O E -~ 1000 C: C'O en .. 0 800 G> (.) C'O 't: ::s Cl) 600 400 200 0 co co co co co 0) 0) 0) 0) 0) ----co co co co co .c i -N-(.) ..:::J Q) ->, (/) >, Cf) C'/) >, Cf) Cf) Figure 3-26 Surface organic matter in the wetland treatment cells. Data presented are those of initial mulching ( August 1996) and surface organic matter (Ju}y 1998), after 23 months of operation Bars are standard errors

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112 Solar insolation Data on solar insolation and canopy interception in the wetland systems are presented in Table 3-14 Part of the canopy of wetland System 2 in July 1998 is shown in F i gure 3 27 On a summer cloudless day near mid-day when outside ambient solar insolation levels averaged 7464 25 moles m -2 solar insolation reaching ground level in the wetland systems averaged 373 20 moles m -2 in System 1 Cell 1,367 32 moles m -2 in System 1 Cell 2,563 51 moles m -2in System 2 Cell 1, and 504 61 moles m -2in System 2 Cell 2 ( Table 3-14) These data represent canopy interception reductions of95% in System 1 Cell 1 93% in System 1 Cell 2 82% in System 2 Cell 1 and 90% in System 2 Cell 2 Measurements of solar insolation reaching the perimeters of the wetland treatment cells (the outer 0 5 m ), show that in System 1 Cells 1 and 2 the light levels are slightly lower than but comparable to average light levels for the whole treatment cell ( 4 9% on the perimeter vs 5% for Cell 1 and 6 8% on the perimeter vs 7.5% for Cell 2) Perimeter light levels are considerably higher however for wetland System 2 with Cell 1 perimeter light averaging 33% of ambient vs 18. 1 % for the whole cell and in Cell 2 perimeter light averaging 12. 1 % of ambient compared to 9.8% for the whole cell. The statistical significance of these differences (by t-test for two samples of unequal variance ) are p < 0 .12 for System 2 Cell 1 and p < 0.19 for System 2 Cell 2 Canopy closure Canopy closure of the wetland treatment cells was analyzed with hemispheric canopy photographs 23 months after planting (Table 3-15 Figure 3 -28)

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113 Table 3-14 Insolation levels and their reduction in the constructed wetlands 28 July 1998 between 1050 and 1145 AM. Perimeter light levels are the measured insolation at locations 0 5 m inside the wetland systems along their outside edges Location Ambient System 1 Cell 1 System 1 Cell 1 Perimeter System 1 Cell 2 System 1 Cell 2 Perimeter System 2 Cell 1 System 2 Cell 1 Perimeter System 2 Cell 2 System 2 Cell 2 Perimeter Solar insolation mol 7464 25 373 20 367 32 563 51 504 61 1350 225 2460 641 722 902 112 Percent of ambient light 5.0% 4 9% 7 .5% 6 8% 18. 1% 33.0% 9.8% 12. 1%

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Figure 3-27 Photohraph showing dense canopy cover intrecepting solar insolation wetland system 2 July, 1998

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115 Table 3-15 Light penetration and canopy closure in the wetland systems and adjoining mangrove wetland, 29 July 1998 Data presented standard error of the mean. Location Number of Light through Canopy closure Photographs canopy (percent) (percent) System 1 Cell 1 9 12. 5 1.4 87 5 1.4 System 1 Cell 2 9 16.1. 9 83. 9 2 9 System 2 Cell 1 9 15. 2 2 6 84.8 2.6 System 2 Cell 2 8 13.1 1.8 86 9 1.8 Mangrove wetland 9 14. 8 1.8 85.2 1.8

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Figure 3-28 An example of canopy cover photograph using fish-eye lens 2 July 1998

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117 Canopy closures were greater than 80% in all the treatment cells The largest closure in System 1 Celll ( 87 5 1.4%) was slightly greater than in the least System 1 Cell 2 (83. 9 2 9%) The significance of this difference by t-test for two samples of unequal variance is p < 0.27 Canopy closures in System 1 (85 7%) System 2 (85.8%) and the mangrove receiving wetland in the vicinity of the discharge (85 2 1.8%) were similar Chemical Characteristics and Uptake Phosphorus Data on total phosphorus from the two wetland systems are presented in Figure 3-29 and Figure 3-30 The influent concentrations and reduction of phosphorus in the wastewater varied seasonally in both systems as they did for all other wastewater constituents as a result of large seasonal changes in numbers of residents and tourists in the buildings connected to the wetland units System 1 had average discharge of 1.1 0.2 mg/liter phosphorus compared to the background levels in the cenote of 0.46 0.17 mg/liter (Table 3-16) In wetland System 2 discharge water contained 2 7 0.4 mg/liter P Overall reduction in phosphorous between initial levels in the septic tank and discharge from wetland Cell 2 was greater in System 1 which averaged 84% while System 2 had a P reduction of71 % on average (Table 3-17 ) Tests to determine the variability in analysis of total P at the University of Florida Water Reclamation Laboratory were conducted with the samples of 31 August 1997 and 27 September 1997. Results in Table 3-18 show that the largest standard error of the mean was less than 6% of the determination

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25 20 :::::::: 0) 15 E-(/) :::J \_ 0 .c Q. 10 (/) 0 .c Q. ro +-' 0 I5 0 -----[_M t-(J) I C co -, I co N I t-(J) I ..0 Q) u... I co N ---n I ---rn. t-(J) a.. cq: 0 (") -h-, t--(J) ...!.. :::J -:, I co --------------h t-t--I'I'-(J) (J) CJ) CJ) I I I I CJ) CJ) 0. ...... u :::J :::J Q) , I ...!.. (.) C C I... I... I... co C Q) co co co co 0. :::J 0 -, -:,
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25 20 :::::: 0) 15 E Cf) J L. 0 .c 10 0... Cf) 0 .c (L cu 5 ...., 0 f0 "--., ~ r-en I C cu -:, I co N I --.,. ,, -r-en I .0 Q) LL I co N D Effluent from -Septic Tank D Effluent from Cell 1 -D Effluent from Cell 2 ------I Wetland 2 --f----1:-.. -. ,=--,-' :-'----:::-I r-en I L.. cu 2 I .-('I) -' I 1lm=1[6.,1D-n, r-en I ::J -:, I co r--0) I t5 0 I r-N -r-en I (J Q) 0 I .7 T co 0) I C cu -:, I C'? co 0) I C cu -:, I N co 0) cu 2 I C'? I I co 0) cu 2 I 0 C'? ' f-igure J -30 Total rhosrhorus (TP) analyses of water samrle s from wetland treatment system 2. -f----. f----' .. -' .. co en I C ::J -:, I 0 C'? =--; -co en ..!.. :::J -, I N N -I

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120 Table 3-16 Total phosphorus content of water samples from cenote (groundwater well) near wetland treatment systems. Date Total phosphorus mg/liter ............... -------.,.,, .......... * ....... ,.,. __ ..,___ -- ..,...,. ___ .,..,, 4 ., ..,..,... ,,., _..,_ ...... ___ ,,,, ____ ...._ ............. .... _..,._ .,. ..-___ ... 28 Jan 97 0.52 28 Feb 97 0.37 31 Mar 97 0.33 30Apr97 0.17 8 Jul 97 0.75 11 Aug97 0.5 31 Aug 97 0.35 27 Sep 97 0.9 27 Oct 97 0.4 1 Dec 97 0.3 Mean standard O. 46 0. 07 error

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121 Table 3-17 Total phosphorus in effluent from septic tank and discharge effluent from wetland treatment systems and percent reduction of phosphorus levels Date of System 1 Discharge Percent System 2 Discharge Percent Test Septic from Reduction Septic from Reduction tank System 1 tank System 2 mg P / liter mg P / liter mg P/liter mg P/liter .... "-n .... ........... ......... ---~--28 Jan 97 6.0 0.4 93.7 7 3 0 28 96.1 28 Feb 97 12. 2 N I A 10.3 4 61.0 31 Mar97 14. 8 1.4 90.5 6 1 3 75 38 5 30 Apr97 14. 3 0 8 94.4 4 0 0.95 76.3 8 Jul 97 5 8 0 6 89 6 4.7 0.55 88 3 11 Aug97 4.8 0.55 88.5 2.3 1.55 32.6 31 Aug 97 3.3 0 55 83. 3 0.4 0 55 -37 5 27 Sep 97 1.4 0 .65 53 6 1.4 0.45 66 7 27 Oct 97 2 1 0.55 73. 8 1.4 0 .85 37 0 1 Dec 97 6.4 2.3 64.1 6.4 1.3 79 7 3 Mar 98 8 55 0 54 93.7 10. 75 4.77 55. 6 30 Mar98 5.45 1.07 80.4 8 84 4 05 54.2 30 Apr 98 9 .93 0 52 94 8 17.43 4 07 76 6 31 May 98 5.64 1.67 70.4 16.59 5 96 64.1 30 June 98 3 .93 1.91 51.4 27 59 4.72 82. 9 22 Jul 98 4 22 2.2 47 9 23.39 5 1 78.2 19 Aug 98 5 95 1.52 74 5 13.71 3 .71 72.9 Mean 7 0 1.0 1.1.2 9 .1.7 2 7 0.4 standard error Overall 83. 9 70 9 reduction

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122 Table 3-18 Total phosphorus content of water samples from the treatment wetlands Wetland treatment area Date of sample Average result from Standard error of 3 tests the mean mg P/liter mg P/liter Wetland System 1, septic tank 31 August 1997 3 38 0 044 Cell I 31 August 1997 1.35 0 05 Cell2 31 August 1997 0 58 0 017 Wetland System 2 septic tank 31 August 1997 0.42 0.017 Cell l 31 August 1997 0 58 0 033 Cell 2 31 August 1997 0 53 0 017 Wetland System 1 septic tank 27 September 1997 1.47 0 033 Cell I 27 September 1997 1.72 0 017 Cell 2 27 September 1997 0.6 029 Wetland System 2 septic tank 27 September 1997 1.42 0 033 Cell I 27 September 1997 0.62 0 033 Cell 2 27 September 1997 0.45 0

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123 Nitrogen Figures 3-31 and 3-32 present results of total nitrogen water quality tests from the wetland systems Final effluent reduction of initial nitrogen tended to become more efficient as the wetland systems developed In the more heavily nutrient-loaded wetland System 2 which had final effluent N concentrations in the septic tank ranging from 38 mg N /l iter ( 28 February 1997 to 6 mg N / liter (30 April 1997 8 July 97 and 11 August 1997 ) to 1-2 mg/liter (31 August 1997 and 29 September 1997). There was considerable variability, septic tank N concentrations ranging from a high of 117 mg N / liter to a low of 6 mg N / liter (Table 3-19). Ammonia (NH3 ) analysis was conducted when the plants were still very undeveloped on 12 January 1997 (Table 3-19) Wetland System 1 had only a 30% reduction (from 17 2 mg N / liter in the septic tank to 12 mg N / liter in discharge water from Cell 2) Wetland System 2 had a 46% reduction (from 32 mg N / liter in the septic tank to 17 2 mg N / liter in wetland Cell 2). The rest of the nitrogen analyses were for total N The nearby cenote had an average concentration of 7 6 1. 8 mg N / liter from laboratory analyses conducted concurrently with those for the constructed wetlands (Table 320) Discharge water from Wetland System 1 had an average N concentration of 6 1 1 1 mg N/liter statistically not significantly different than the cenote Discharge water from Wetland System 2 averaged 13.9 3 5 mg N / liter. During the course of the study total nitrogen levels in the wetland system discharge effluent were reduced from initial septic tank levels by an average of 86.0% in wetland System 1 and 73 1% in wetland System 2 (Table 3-19)

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140 -,-----------------------------------------, 120 100 L.. Q) -~ :::::: 0) Eao C (1) 0) 0 L.. :gso cu 0 1-40 20 0 ,..._ O> I C ro -, I N ..-l'---0> I .0 (1) LJ.. I co N l'---0) I ,_ ro 2 I ..... ("') ,..._ O> I ::, -, I co l'---0) I 0) :::, I I I g-t5 en O o I I I 0) I'--..... Date ~fTest co (J) I ,._ ro 2 I ("') co (J) ro 2 I 0 ("') co 0) 0. , ro I ..-("') co (J) I C :::, -, I 0 ("') co 0) I :5 -, I N N co 0) t 0) ::,
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140 .---------------------------------------~ 120 --t------------------------------------1 100 0) E C C 80 -+---------------------------- Q) 0) e "E 60 ro ...... -E -,: I:~--~---;;.::_ ;~ 0 40 -+----1,'.!l:,1-------------------I",. __ ... .. :. ..:. i r :_. ~--,,j_j-~----. __ t_-_1_:_-_:_ ~_;_:,~_.:_;_. _ :,._-_ -_ : __ :-_ i--' 20 0 -~ . = ell -f_,_m _i;_ =-f_:~_i __ ;-:-:frF 1-:~-~-1,:1--------------fr' --. ._,..... l,_:_:_i_' -~-:_. :~-i [_~ t _~-~ -n ;_~-;,~_~_!=_: -l i ~ T _-J!. 7 t :il Ehl. r;k_, [[k i '.f, ,; 7 ~11 ; ih I 1P I ; C } l .,, if I I r-r--0) 0) I I C .0 ro Q) ---, LL. I I N co ..-----N r--0) I I,... ro I -.--(") I l T T T T I r--0) I I,... 0. c:i: 0 (") r--O> ...!... ::::, ---, I co r--0) I 0) ::::, <( I ..------.--r-r--0) 0) I I 0) 0. ::::, Q) c:i: (f) I -.--0) (") N r--r-co co 0) 0) 0) 0) I I I I ....., (.) I,... I,... (.) Q) C'O ro 0 0 I I I I r--..-----_ (") 0 N (") I co co co 0) 0) 0) I I I I,... >, C 0. ro ::::, <( ---, I I I 0 -.-0 (") (") (") Figure 3 32 Total nitro g en (TN) analy se s of water samples from wetland tr e atment s yst e m 2 co 0) ...!... ::::, ---, I N N ,;, ? 'f co 0) I 0) ::::, c:i: 0) -.-Wetland 2 o Septic Tank CJ Wetland Cell 1 D Wetland Cell 2 -N VI

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126 Table 3-19 Total nitrogen in effluent from septic tank and discharge effluent from wetland treatment systems and percent reduction of nitrogen levels Date of System 1 Discharge Percent System 2 Discharge Percent Test Septic from Reduction Septic from Reduction tank System 1 tank System 2 mg N / liter mg N / liter mgN/ liter mg N/liter 28 Jan 97 17.2 12 30.2 32 17.2 46.3 28 Feb 97 108 N I A 72 38 47 2 31 Mar97 132 4 97 0 36 26 27.8 30 Apr 97 132 10 92.4 36 6 83. 3 8 Jul 97 48 8 83.3 36 6 83. 3 11 Aug 97 36 6 83. 3 16 6 62 5 31 Aug97 10 2 80. 0 6 1 83.3 27 Sep 97 20 6 70 0 8 2 75 0 27 Oct 97 22 8 63.6 10 2 80. 0 1 Dec 97 38 14 63.2 72 14 80 6 3 Mar98 7 6 3 .82 49.7 58.4 4 .86 91.7 30 Mar98 8.44 5.51 34.7 94.45 12.5 86.8 30 Apr 98 16.99 0 7 95.9 87. 8 4 .82 94 5 31 May98 53. 36 10. 74 79.8 20 38 10. 64 47 .8 30 Jun 98 25.88 0.28 98 9 53.96 19.1 64 6 22 Jul 98 47 .22 0.86 98 2 117 5 9.32 92 1 19 Aug 98 22 34 12.48 44.1 59 6 16. 2 72 .8 Mean +/ -43. 8 9.9 6 1 1.1 51.5 9.0 13. 9 3 5 standard error Overall 86. 0 73 1 reduction

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127 Table 3-20 Total nitrogen content of water samples from cenote (groundwater well) near wetland treatment systems Date Total nitrogen mgN/liter 28 Jan 97 19. 6 28 Feb 97 10 31 Mar97 8 30 Apr97 4 8 Jul 97 8 11 Aug 97 10 31 Aug 97 1 27 Sep 97 4 27 Oct 97 10 1 Dec 97 1 Mean standard error 7 6 1.8

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128 Biochemical oxygen demand BOD-5 (biochemical oxygen demand 5 day test ) analyses are presented in F igure 333 and Figure 3-34 Reduction of BOD improved after the initial analyses in January 1997 shortly after the wetlands were first connected to sewage inputs Table 3-21 presents septic tank effluent and final discharge levels ofBOD from the wetlands Wetland System 1 had average discharge concentration of 12.4 1.7 mg BOD / liter over the course of study. Wetland System 2 had an average discharge of 23 .4 6 6 mg BOD / liter. Wetland System 2 which received sewage from a higher percentage of its design population showed higher levels of influent BOD with septic tank analyses averaging 161. 7 mg/I compared to 129 mg/I in System l s septic tank effluent (Table 3-21) BOD reduction was comparable in the two wetlands with wetland System 1 averaging a 87 7% reduction compared to 83.5% in wetland System 2 Final effluent BOD from the wetland System 1 was around 40% lower than the nearby cenote whose BOD averaged 20 7 +/ -3 9 mg/liter (Table 3-22) while discharge effluent from wetland System 2 was about 15% higher. Total suspended solids Results of total suspended solids (TSS) analyses in effluents from septic tanks and treatment systems are presented in Table 3-23 and Table 3-24 and in Figure 3-35 and F igure 3-36 During the study TSS averaged around 70 mg/liter in the two septic tanks effluent and was reduced 41 % on average Suspended solids were consistently higher in wetland

PAGE 153

300 0 ... 250 0 ::::: C) E U') I 8 200.0 en "C C: C'CS E 150 0 C: (1) C) 0 c; 100 0 -~ E (1) .c CJ 50 0 0 0 lill ---!Pi~) ti' ili, l :i1l!j C ro J I N ,.... 11 qlff :Ii> HU /!Ii !U' ~ll ;~, u; foi /!!l iln l!!! 11!! llliii ,, -J C ro J I N N 'm; li11 ,i11-,/lliX ., I .~. l 1,1~, i1w lf ,! il. l'' ii .; ,:i ,(n "S J I N T' llij l1U ij~ Hi ,. ;lit d~ !~' ,d 1lj, 1111 '' I? !~, 'rih I .lli Iii* a. (1) (./) d, N I "i7 !~I !11! 'ti Ui i!1j 11,1 '1 ij_ 11:.n ; 1 I () (1) Cl I ,.... I !Ii 1.; I!., JIil iili ,111 IN 1:I: !!l; !II! ljr !I/ 1!, 'II % 1111 -'I' r1 1!11-'r" 1,11n 111 I :1 .... ro I 0 N I ----"-~I i'I' f 1!, !.q "ii il11 < H 1:{ i r !l 'll Jl: :111,~ C ::, ...., I ,.... ,.... ll!l Effluent from Sept i c Tank Cl Effluent from Cell 1 D Effluent from Cell 2 Wetland 1 F igure 3-33 Biochemical oxygen demand (BOD5 ) in wetland system l water samples

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..... :::::::: 0) E -0 C cu E Q) 0 C Q) 0) 0 cu u E Q) .r:. u 0 m 300 250 200 150 100 50 0 r;ip ;11Ul f--------------------ri1ll11----------------------I M lflPI~ 1,11 ~,\,1,1,'.f! 111,il -~ ru. 1lill1 1: r.r. !1!111,:_ Jill'', ii!l ,i,,1 .. : f i!.;ft'' 1l' I/' l 1,!ll 1Ul1 -----.J.1ll1--------------1:ll:,:l,!l't-----.-...,.J.1 .. 11'""1jj--------t:11111---llllllj.---! ,r1~ ~1 1m1 -1 11 Ii 1hl, !l!il1 w = ~ 1l~ ,-!i!.;,'i. 1.,,1.',!i.. W,j li11!1-----1Uli!l----1ij,,i1------1l!!l! ''11 :mi ,.. ii1 ei, M1 n"i1 1 1 '"iij,1---__, iU1'j lj!J: '.: .. :.':,,::'';1;:,:;;!,.i!i!;J'i,. '.l,liJ!!!'j1:1'i!:,I:'.::: Jij., Jtj-1 1:,,; l 11 ii~ . i,l.:,:i,, lil!i : ~,,,.''.l:.1,:.lRl;,1! ''Iii 'it: ,,Jf ... ~l: ~,1 b u 1,1.~ 1.1,,1 t r~11 ~ ~1~11 ,,~ i,f1j!;,1.i.'._. 1 1 1111j. .. ,,, I, .. di!' il,I! ,.l,!'!.11,. .'..l1!1 JI!! -~ e!li!i,, ----l!!llr.,.~;.,.... ,----1:!j~j----1;j1ll'1;u;----!~~1----lil~l .1f1!~,!:l;----l''j!l11l .... _---!1IIH ! -11,j' ;::; '11ill >;; 'Hj!j II! I i\llli '111!1 !l l [ ; ll!il I li.1/1. ? J . 11 ~' '. ,!hl, '1' P." tt1 ;; 1,',1,,,11 .. 1 !!ii!I ffl-7 ,:_'1.'11' '""'. : l1! i ,fit,; 11 I \ :.f !1;11 lj !!It < ~ l I!.'! 'I ,i#,;,I 7 i.1.1.i. ,,., -111!1 :{'_'1'1'1.:.'.1 ll . .. :. '1,.: ll; m:.. f!.!1l!l ~: 7 !~ 'j' M,I i,1 :1li!ll i!:' I !I ,. I P I I -~ul = I ,m 'l l' !l!i:1 .. i II I ,;', llH -j d:1 , ti, ,., I : 1!h,i I" : 1i1f:8-, : ii! : : l:ilir, t r--0'> I C ro -, I N ,.-r--0'> I C ro -, I N N r--0'> I ..0 Q) u... I N r--0'> I ::, -, I N r--0'> I a. Q) en I O> N r--0'> t) Q) 0 I ,.co O'> ro I 0 N Figure 3-34 Biochemical oxygen demand (BOD5 ) in wetland system 2 water samples co O> I C: ::, -., I r--,.-G Effluent from Septic Tank !El Effluent from Cell 1 Wetland 2

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131 Table 3-21 Biochemical oxygen demand (BOD-5) in effluent from septic tank and discharge effluent from wetland treatment systems and percent reduction. Date of System 1 Discharge Percent System 2 Discharge Percent Test Septic from Reduction Septic from Reduction tank System 1 tank System 2 mgBOD/ 1 mgBOD/ 1 mgBOD/1 mgBOD/ l 12 Jan 97 48 3 12. 6 73.9 108.3 53.4 50 7 22 Jan 97 120 15 87.5 240 35 0 85.4 2 Feb 97 59 1 14.7 75.1 111 18 9 83.0 3 Apr 97 120 5 95 8 100 20 0 80 0 2 Jul 97 300 16 94.7 263 14 0 94 7 29 Sep 97 112 9 92 0 150 6.0 96 0 1 Dec 97 96 16 83.3 112 12. 0 89.3 20Mar 186 21 88 7 171 29 83. 0 98 17 Jun 98 120 2 98 3 161.7 23.4 83.5 Mean 129 12.4 161.7 22.8 standard 34 1 1.7 27 8 6.6 error Overall 87 7 83. 5 reduction

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132 Table 3-22 Biochemical oxygen demand (BOD-5) content of water samples from cenote (groundwater well) near wetland treatment systems Date BOD-5 mg BOD / liter 12 Jan 97 29 7 28 Jan 97 15. 0 2 Feb 97 16. 0 3 Apr97 25. 0 2 Jul 97 32.0 29 Sep 97 6 5 1 Dec 97 12.0 Mean standard error 20 7 3 9

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133 Table 3-23 Total suspended solids (TSS) concentrations and reduction in septic tank and discharge water from the Akumal wetland treatment systems Date of System l Discharge Percent System 2 Discharge Percent Test Septic from Reductio Septic tank from Reduction tank System l n mgTSS/1 System 2 (Increase) mgTSS/ 1 mgTSS/1 (Increase) mgTSS/1 12 Jan 97 17.2 12.0 30 32 17.4 46 28 Feb 97 57.6 29.2 49 59.2 33 2 44 31 Mar 97 46 27. 2 41 45.2 36 8 19 30 Apr 97 56 41.6 26 34.4 27 2 21 8 Jul 97 31 18 42 37 9 76 11 Aug97 42.5 22 5 47 33 5 25.5 24 27 Sep 97 8 16 ( + 100) 23 2 16 31 29 Oct 97 2 32 8 ( + 1540) 37 6 35 6 5 3 Jan 98 31.6 20 37 53 2 16 70 24 Jan 98 40 16 8 58 48 27 2 43 3 Mar98 100 56 44 77 64 17 30 Mar 98 80 55 31 85 48 44 30 Apr 98 79 65 18 106 97 8 31 May 98 64 79 ( + 23) 227 66 71 30 Jun 98 65 58 11 238 60 75 22 Jul 98 62 76 ( + 23) 209 67 68 19 Aug 98 131 23 82 118 26 78 Mean 53 .7 38 2 5.4 86 1 17 3 39 5 5 8 standard 8 0 error Overall 29.0 54 1 reduction

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134 Table 3-24 Total suspended solids (TSS) content of water samples from cenote (groundwater well) near wetland treatment systems Date Total suspended solids mg TSS/Jiter 12 Jan 97 19 6 28 Feb 97 20.4 31 Mar97 34.4 30 Apr 97 24.4 8 Jul 97 20 11 Aug 97 26 5 27 Sep 97 28.4 29 Oct 97 10.4 Mean standard error 23 0 2 5

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250 .-----------------------------------~ 200 --t--------------------------------------~ ':m ::::::::: E 1 so ~ ------Cf) Cf) I-U) :Q 0 Cf) 'U Q) 'U C Q) a. U) :J Cf) ro 0 I-100 --t-----------------------~--r"'I-50 +------f""r-----1a---------------h1 -t 0 I i-, :ni, ~ ,JJJJlftin, 1 -ILt ~ -$ l ~ f fITT-1 I t ~ ,: 1 a t ( l '.Ii I I I I t---t---t--t---t---t--t--t---co co co 0) 0) 0) 0) 0) 0) 0) 0) 0) 0) 0) I I I I I I I I I I C ..0 L.. L.. ::I 0) a. .... C C co Q) co a. ::I Q) (.) co co a. ro >ure 3-35 Total suspended solids (TSS) in water samples from wetland system l. I C .: co 0) I ::I J I N N I CJ Effluent from Septic Tank D Effluent from Cell 1 D Effluent from Cell 2 Wetland 1

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-(I) (I) I-(/) :Q 0 (I) -0 250 200 150 100 +----------------------0 C (1) a. (/) :::, (I) m ...... 0 II'! ,I , ': ~i -l' 50 -1---ttl-' -------------ru;r--~ -1,;1 t-0) I C co -, I N ..--t-0) I .0 Q) LL. I co N t-0) ..'... a. , C :S a. co ::, -, 4= -, I I N 0 I 0 ..--N C") C") C") Figure 3-36 Total suspended solids (TSS) in water samples from wetland system 2. lEI Effluent from Septic Tank raJ Effluent from Cell 1 D Effluent from Cell2 Wetland 2 ...... (.;J ~ -' F. r <:: -FI: l !1 .... !1 ,, % if -L ~-'., .. ,; I: I' r--, r Ii co 0) I O> ::,
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137 System 2 and were reduced more (54%) than in System 1 (29% reduction) On average both systems reduced TSS to around 39 mg/liter but discharge varied from under 20 mg/1 to over 90 mg/1 (Table 3-23) TSS in the nearby cenote averaged 23 0 2 5 mg/liter (Table 3-24) TSS reduction varied widely, both on a percentage basis, and in concentrations in effluent water. For example, several times wetland System 1 showed higher discharge TSS than influent TSS and suspended solid concentrations were higher during March August 1998 than they had been earlier in the study (Table 3-23) This may reflect release of materials from biota or gravel of the wetlands themselves Alkalinity Data on alkalinity is presented in Table 3-25. Alkalinity in the septic tanks was far lower (155 mg/1) than in either wetland System 1 or wetland System 2 These systems averaged 308 mg/1 and 344 mg/1 alkalinity respectively. Alkalinity in the cenote was lower than in the wetlands averaging 252 mg/1. Salinity Salinity observations are presented in Table 3-26 Salinity decreased as the sewage effluent passed from septic tank through Cell 1 and Cell 2 of the wetland systems. Average salinity was 4 1 0 2 ppt (parts per thousand salt) in System 1 septic tank but decreased to 3 3 0 3 ppt salt in Cell 2 effluent. In System 2 variability was greater, and salinity differences were not statistically significant. In System 2 septic tank effluent averaged 3 6 0 2 ppt salt while in Cell 2 it was 2 6 0 .8. Salinity in the cenote averaged 2.6 0 2 ppt.

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138 Table 3-25 Alkalinity in septic tanks, wetland systems and cenote Location 27 Sep 97 29 Oct 97 Average Septic tank System 1 72 32 52 Wetland 1 Cell 1 248 414 331 Wetland 1 Cell 2 266 304 285 Septic tank System 2 214 300 257 Wetland 2 Cell I 320 344 332 Wetland 2 Cell 2 360 350 355 Cenote 224 280 252

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139 Table 3-26 Salinity in septic tanks, wetland system and cenote Salinity expressed as parts per thousand salt (ppt). Date System 1 Celll Cell 2 System 2 Cell 1 Cell 2 Cenote Septic tank ppt ppt Septic tank Ppt ppt Ppt ppt ppt 12 Jan 97 3 5 2 5 2.5 4 3 2 2 2 Feb 97 4 5 4 3 3 1 0.5 2 28 Feb 97 4 4 4 4 5 5 3 14 Apr 97 4 3.5 3 5 3 2 2 3 21Dec 97 4 5 4 3 5 4 3 3.5 3 Mean 4 1 3.6 3.3 3.6 2.8 2.6 2.6 std. error .2 3 .3 2 7 .8 .2

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140 Reduction in Coliform Bacteria Figure 3-37 and Figure 3-38 are graphs of coliform bacteria concentrations in the septic tanks and treatment cells of the wetlands These data show levels of the bacteria were reduced by 99 87% on average after treatment in the wetlands (Table 3-27) Final effluent coliform bacteria levels were fairly uniform for the two wetland systems averaging 1580 810 colonies (MPN) / 100 ml in wetland System 1 and 2850 1160 (MPN) / 100 ml in wetland System 2 (Table 3-27). Consistent reduction of fecal coliform bacteria was achieved as the wetlands developed although the absolute numbers varied widely between tests Even initial tests in January 1997 showed 99% reduction (wetland System 1) and 99 8% reduction (wetland System 2). Subsequent tests generally showed reductions of99. 9 + % in both wetlands ( Table 3-27) Concentrations of coliform bacteria in the final discharge into the mangroves although numerically lower were not statistically significant from coliform bacteria concentrations in the cenote which averaged 3 339 2 267 (Table 3-28) Phosphorus Uptake by Limestone Ca/Mg analysis of limestone Table 3-29 presents results of analysis of the Yucatan limestone gravel used in the wetland treatment units for calcium and magnesium content. Calcium constitutes 26 6 0 6 percent of the gravel material and magnesium is 11.9 0 2 percent by weight. If both occur primarily as carbonate minerals (e .g calcite Mg-calcite aragonite and dolomite) we can calculate their overall molecular weight as 100 1 for CaCO3 and 84 3 for MgCO3 Thus

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E 100.0E+3 0 0 -z a.. 10.0E+3 co c Q) ..... u co 1.0E+3 .0 E 8100. 0E+0 10.0E+0 1.0E+0 r-r--r--r--r--co co 0) 0) 0) 0) 0) 0) 0) I ...!.. I I I I C a. () Lo-C a, a. ::, Q) Q) a, ::,
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10.0E+6 1.0E+6 E o 100.0E+3 0 T-z c.. 1 0.0E+3 ro c ro 1.0E+3 ..0 E .E 0100.0E+O () 1 0.0E+0 1.0E+0 r--r--r--O'> O'> O'> I _..!... C ro a. :::::, 0) 0) O'> I I I a. (.) C Q.) Q.) ro :::::, CJ) Cl -, I I I I 0) ...... 0 ("() N N N Date of Test Figure 3-38 Fecal coliform in water samples from wetland system 2. Data plotted on log scale, and units are Most Probable Number (MPN) of bacterial colonies per 100 ml. Bacteria in Effluent from Septic Tank nm Bacteria in Effluent from Cell 1 D Bacteria in Effluent from Cell 2 Wetland system 2

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143 Table 3-27 Coliform bacteria concentrations in effluent from septic tank and discharge effluent from wetland treatment systems and percent reduction. Data is in units of most probable number of colonies per 100 ml (MPN / 100 ml). --Date of System 1 Discharge Percent System 2 Discharge Percent Test Septic from Reduction Septic tank from Reduction tank System 1 MPN / 100 System 2 MPN/100 MPN / 100 ml MPN / 100 ml ml ml 27 Jan 97 8 000 80 99.0 1 300 2 99.85 3 Apr97 160 000 2 99 99 17 000 2 99.99 8 July 97 4 400 000 4 100 99 .91 5 000 000 4 000 99.92 29 Sep 97 8 000 000 1 280 99.98 12, 000 000 1 100 99.99 1 Dec 97 4 000 000 3 000 99 .93 8 000,000 4 000 99 .95 20 Mar 98 6 200 000 520 99 97 8 600 000 2 180 99 97 23 June 98 1 200 000 2 100 99 .82 11, 200,000 8 700 99 92 Mean +/ 3 424 000 1 580 6 403 000 2 850 standard 1 160 error 1 167 000 1 ,861, 000 Overall% 99.80 99 94 reduction

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144 Table 3-28 Coliform bacteria concentrations in water samples from cenote (groundwater well) near wetland treatment systems Data is in units ofMPN/ 100 ml (most probable number of colonies per I 00 ml) Date Coliform bacteria MPN / 100 ml .............. _______ ...... --27 Jan 97 1 100 3 Apr97 8 July 97 29 Sep 97 Mean +/ standard error 1 100 1014 10. 140 3 ,339 2 267

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145 Table 3-29 Calcium/magnesium content of Yucatan limestone gravel as analyzed by inductive coupled plasma spectroscopy. Sample 1 2 3 4 5 Average standard error of the mean Percent calcium Percent magnesium -Ho 25.6 12.5 26 3 12.1 28 2 11.7 25.4 12. 1 27 7 11.2 26 64 0 56 11.92 0 22

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146 carbonate minerals constitute over 95% of the material. This compares with publ i shed estimates, for example of Pleistocene dune rocks of northeastern Quintana Roo being totally carbonate dominated by aragonite with 20-40% mg-calcite and small amounts of calc ite, and dolomite comprising 25-68% of supratidal sediments in lagoons studied near Akumal (Ward, 1975 cited in Weide 1985) Initial and uptake phosphorus levels To determine the rate at which phosphorus was being absorbed by the limestone gravel samples of I/limestone gravel not exposed to the sewage 2 / limestone above the sewage water level of the wetlands and 3 / limestone below the water level and thus exposed to the sewage for eleven months of system operation were analyzed for inorganic phosphorus content (Table 3-30) These results indicate that phosphorus enrichment has averaged some 6 mg/kg (ppm) per year in the limestone exposed to sewage. Limestone prior to placement and limestone above the sewage level average 38 0 2 9 mg/kg while limestone below the sewage level averaged 43 8 1.7 mg/kg. Limestone in the first treatment cells of both wetland systems were marginally higher in phosphorus content than the limestone of the second cells, but the results are not statistically significant. In System 1 first cell limestone totaled 43 5 3 7 mg P/kg while in the second cell phosphorus content totaled 39 9 3 7 mg P/kg In wetland System 2 first cell limestone totaled 48.1 2.5 mg P/kg while that of the second cell was 43 6 3.4 mg P/kg (Table 3-30) F igure 3-39 presents the phosphorus starting value and uptake by limestone in the wetland systems during their first year of operation Since limestone gravel averages 1350 kg/m3 and there are 25 m3 oflimestone in System 1 and 41m3 in System 2 we can

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147 Table 3-30 Inorganic phosphorus content of limestone samples Date Description # of Mean Standard collected samples phosphorus error of the mg/kg mean - ... " .. T .. - -~---- ,_,,.,,, ,_._, " Aug 96 Limestone gravel not used in wetlands 3 40 3 4 2 Dec 97 Limestone above the sewage line Aug 96 All limestone not exposed to sewage + Dec 97 (total of above 2 categories) Dec97 All limestone exposed to sewage ( composite of samples from all cells and systems) Dec 97 System 1 Cell 1 below sewage level Dec 97 System 1 Cell 2 below sewage level Dec 97 System 2 Cell 1 below sewage level Dec 97 System 2 Cell 2 below sewage level 4 7 20 5 5 5 5 36 3 38.0 43 75 43.5 39 9 48 1 43.6 4 35 2 9 1 68 3.7 3 7 2.5 3.4

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150 g/month ,,,,---Limestone gravel 8 .9E?g p bacterial biomass 79.1 g/month 23.4 g/month / / / Figure 3 39 Estimates of mon thly flows of phosphorus during first year of wetland treatment system operati ons (1997) Data from both wetland systems are combined 00

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149 calculate that System I limestone totaled 33 750 kg and System 2 limestone totaled 55 350 kg for a combined weight of around 89 000 kg (8 9E7 g) Average enrichment in System 1 limestone was 3 8 mg P /k g E nrichment in System 2 limestone averaged 7.8 mg P/kg for a total uptake of 570 g P / yr or 47.5 g P / month This is equivalent to 40 kg P ha-1 yr -1 uptake by the limestone in the wetlands on an areal basis Phosphorus levels in influent water averaged 6 25 mg/I and was 1.3 mg/1 in eflluent water. So with 800 litters / day entering the system phosphorus into the system was 150 g/month and after ET losses discharge was 600 litters / day, phosphorus in discharge water totaled 23 4 g/month The unaccounted for phosphorus totaling 79.1 g/month was likely taken up by bacterial and plant biomass. Experiments on limestone P uptake In Table 3-31 and Figure 3-40 the reduction in phosphorus is reported from laboratory experiments where phosphorus solutions were mixed with Yucatan limestone in bottles After ten days phosphorus was reduced 28-63% when initial conditions were 5.6-111 mg P/liter Field experiments where actual septic tank effluent was employed, showed 56.9% reduction with a starting concentration of 5 .11 mg P/1. In samples where the ratio of limestone gravel and effluent were kept nearly equal ( comparable to conditions in the wetland units) reduction of phosphorus increased to 85.6% after 10 days (Table 3-31).

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150 Table 3-31. Resul ts from experiments on limestone uptake of phosphorus Laboratory : Sample Initial One day after Two days Four days Six days Ten days number loading loading Mg/lP mg/lP mg/1 P mg/IP mg/IP mg/lP 2-1 5 6 4.35 4 35 4 3 65 3 19 2-2 5 6 4 35 4 23 4.12 3.42 2 9 2-3 5 6 4 23 4 29 3 .71 3 .31 2 67 Average 5 6 4 31 0 04 4 29 0 03 3 94 12 3.46 0 1 2 92 0 15 Percent 23 0 23 4 29 6 38 2 47 9 Reduction 3-1 11.1 8.1 8 16 7 52 7 23 6 25 3-2 11.1 8.62 8 85 7 75 7 75 6 66 3-3 11. 1 8 62 8 85 8 .21 8 25 6 77 Average 11.1 8.45 0.17 8 62 0 23 7.83 0 2 7 74 0 29 6 56 0 16 Percent 23.9 22.3 29 5 30 2 40.9 Reduction 4-1 22 2 18 6 19.3 19 3 17 5 16.2 4-2 22 2 18 6 19.5 19 1 17 7 15.5 4-3 22 2 18 6 19.8 23 1 16 7 16.5 Average 22 2 18 6 0 0 19 5 0 15 20 .5. 3 17 3 32 16 0 .31 Percent 16 3 12 1 7 7 22 0 27 7 Reduction -5-1 55 6 46.9 56 8 46.4 33.4 29 8 5-2 55 6 52 1 53 7 50 0 63 0 37.6 5-3 55 6 53 7 45.4 53 7 35.0 33 9 Average 55 6 51. 0 04 51. 9 .41 50.0.1 43.8 .62 33 8 25

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151 Sample Initial One day after Two days Four days Six days Ten days number loading loading Mg/IP mg/IP mg/IP mg/IP mg/IP mg/IP 6-1 111.1 106 2 91.6 103.0 79.6 37. 7 6-2 111. 1 101. 1 108.7 101.8 83.4 42 7 6-3 111.1 101. 8 97.3 85.9 77 6 42 7 Average 111.1 103.0 .61 99 2.04 96.9.51 80 2.68 41.1 69 Percent 7.3 10.7 12 8 27.8 63 1 Reduction Field studies : Sample Initial One day after Two Four Six Ten 30 days number loading loading days days days days mg/IP mg/IP mg/IP mg/IP mg/IP mg/IP mg/IP 7-1 5.11 3.3 2 .65 3 1 2.1 1.55 0.85 7-2 5.11 3 9 3 75 3.6 3.3 2 .8 1.95 7-3 5 .11 4 4 3.55 3.15 2.25 1 avg 5.11 3 7 0.2 3.47 3.42 2 85 2 2 3 1 27 0.41 0.16 0 38 6 0.34 Percent 27.3 32.2 33. 1 44 2 56. 9 75 2 Reduction 7-4 5.11 1.45 0 .8 0 .95 0.75 0 .85 0.45 7-5 5.11 3 .05 1.1 0 7 0.85 0 7 0.45 7-6 5 .11 1.15 1.1 0 95 0.75 0.65 0.4 avg 5 .11 1.88 1.0 0.1 0 87 0.78 0 73 0.43 0.59 0 08 0 .03 0 06 0 02 Percent 63.1 80.4 83. 0 84. 7 85. 6 91.5 reduction

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120 ~------------------------------, 100 .......................................... ........................ :::::: C, E .. C: 080 ... .. +:i +J C: Cl> CJ &,o ------------(.) tn ::::J .... 0 .c: g-40 0 .c: a.. 0 --1-----1--------+-------+------r------i 0 2 4 6 10 Days after Loading Figure 3-40 Graph s with results of experiments on limestone uptake of P -+Loaded at 5 .56 mg/IP --Loaded at 11. 1 mg/I P -A-Loaded at 22 2 mg/I P -*-Loaded at 55.6 mg/IP ---Loaded at 111. 1 mg/I P

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153 Water Budget Estimates of the water budget of the wetland treatment systems are given in Table 3-32 and Table 3-33 The results from the May 1997 study indicated that evapotranspiration rates are similar in wetland systems 1 and 2 since total evapotranspiration is 58% greater in System 2 than System 1 and System 2 is 60% larger. With the system loading occurring in May 1997 on average 0.05 m3 ( 9 gal.) [equivalent to 0.99 mm over the area] was discharged per day from wetland System 1 and 0.33 m3 (85 gal.) [4.1 mm] were discharged per day ( Table 3-32). The data from the December 1997 measurements show that overall evapotranspiration was only 50% that of the summertime for wetland System 1 and 39% in wetland System 2 Discharge in December 1997 was 0 .16 m 3 ( 4 2 gal.) [3 2 mm] per day from wetland System 1 and 0 3 m3 (79 gal) [3. 7 mm] from wetland System 2 (Table 3-33). Hydraulic loading of the wetland systems in May 1997 was equivalent to about 1 9 inches / week for wetland System 1 and 2 8 inches of wastewater / week for wetland System 2 Under these conditions E T losses were 90% of influent in wetland System 1 and 59% in wetland System 2 Estimated hydraulic residence time in May 1997 was about 28.8 days for wetland System 1 and 19.8 days for wetland System 2 The data indicate that hydraulic loading in December 1997 was similar in wetland System 1, but had dropped in wetland System 2 to 1 7 inches / week. Evapotranspiration losses were 41 % in wetland System 1 and 38% in wetland System 2 Economic Evaluation Economic evaluations of the constructed wetlands vs. a package plant sewage treatment system built for a comparable number of residents in Akumal show that capital

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154 Table 3-32 Daily water budget of wetland treatment systems, May 1997. Date Wetland Input from septic E vapotranspiration System system tank loss m3/ day (gal/day) m3/ day(gal / day) May 1997 System 1 0 34 (88) 0 29 (79) May 1997 System 2 0 79 ( 205 ) 0.46 ( 120 ) See notes below Table 3-33 discharge m3/ day (gal/day) 0 05 (9 ) 0 33 (85)

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155 Table 3-33 Daily water budget of wetland treatment systems, December 1997 Date Wetland Input from septic Evapotranspiration System system tank loss m3/ day (gal/day) m3/ day(gal/day) December 1997 System 1 0.3 (87) 0 .14 (361.) December 1997 System 2 0.48 (127) 0 .18(48) Notes on Table 3-32 and Table 3-33 1. Water input from septic tanks discharge m3/ day (gal/day) 0 .16 (42 ) 0 3 (79 ) Eflluent from the septic tanks was estimated from their volume and measured inflow after they were pumped out. Wetland System 1 septic tank is 2 5 m wide x 4 m long x 1 m deep (to the discharge pipe) with a capacity of 10 m3 (2600 gallons). Over the course of9.5 days In May 1997 septic tank filled 0.32 m or 3.2m3 (832 gallons). This is a daily input of 0 34 m3 (87 6 gallons). There were 3 people resident in buildings serviced by the septic tank plus 3 people working in shops whose bathrooms are connected to the septic tank These daytime workers are counted as 0 .33 people so a total of 4 people were serviced by the septic tank. Their daily wastewater production was 0 085 m3 (22.1 gallons / day) In December 1997 septic tank of wetland System 1 filled 0.28 m, so inflow was 2.8 m3 (739 gallons) over the course of9.4 days. This is a daily input of 0 3 m3 ( 78 6 gal) There were 3. 5 people using the system ( computed as above), so daily wastewater production was 0 086 m3 (22.5 gal ) per person Table 3-33 continued

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156 The wetland System 2 septic tank is 2 3 m wide x 4 5 m long x 1.15 m deep (to discharge pipe), a volume of 11.9 m3 (3095 gallons) In 10 days of refill in May 1997 7.87 m3 (2046 gallons) of water entered the septic tank of wetland System 2. This is equivalent to 0 787m3 or 204.6 gallons / day During this period there were 7 people living in housing which the septic tank served On average wastewater production during this period was 29 2 gallons / person/day for wetland System 2 In December 1997, this septic tank filled 4.51m3 (1191 gal.) over 9.4 days so daily inflow was 0.48m3 (127 gal.) With 5 people on average using the system, this equals a daily wastewater production of 0.096 m3 (25.4 gal) per person per day. 2. System evapotranspiration Evapotranspiration (ET) was estimated from decreases in standpipe water levels during periods without discharge input from septic tank. Inputs from direct rain were measured and this addition was factored into calculations of system ET. Porosity of limestone gravel in the wetlands was determined to be 35% through successive measuring of water required to fill a 20 liter bucket filled with the same grade of limestone used in the wetland. Since wetland System 1 is 50.6 m2 with a normal wastewater level of 0.55 m (with standpipe vertical) and a porosity of 0.35 total water capacity of wetland System 1 is 9 74 m3 or 2 533 gallons. Wetland System 2 is 81.2 m2, with wastewater depth of 55 cm porosity 0 35 giving a total system capacity of 15.6 m3 (4,064 gallons) Standpipe water declines in May 1997 in wetland System 1 totaled 7.4 cm (0 074 m) over 4 5 days and in wetland System 2 standpipe water decline totaled 8 9 cm (0 089 m) over 5.5 days Since there was no input into the wetlands during this period and no discharge from standpipe overflow this loss is equivalent to evapotranspiration in the system Evapotranspiration in wetland System 1 was thus calculated to equal 1.31 m3 (340 7 gallons) over 4 5 days or 0 29 m3 (75.7 gallons) per day. Evapotranspiration in wetland System 2 was 2 .52 m3 (657.6 gallons) over 5 5 days or 0.46 m3 (119 6 gallons / day) in May 1997. Standpipe water declines in December 1997 averaged 5.7 cm in wetland System 1 and 5 .17 cm over 9.4 days in wetland System 2 There were three rains totaling 1.8 cm over this period Total evapotranspiration in wetland System 1 was thus 1.29 m3 (340 6 gal) over 9.4 days or 0 137 m3 (36.2 gal) per day Evapotranspiration in wetland System 2 was 1. 7 m3 (449 gal) over 9.4 days or 0.18 m3 (47 8 gal) per day. 3. Discharge of wastewater from the wetland treatment systems Average discharge of wastewater from the wetland systems was estimated from the difference between hydraulic inputs to the system and evapotranspiration losses from the system from wetland System 2. The data from the December 1997 measurements show that

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157 Table 3-33 continued overall evapotranspiration was only 50% that of the summertime for wetland System 1 and 39% in wetland System 2. Discharge in December 1997 was 0 .16 m3 (42 gal.) [3. 2 mm] per day from wetland System 1 and 0 3 m3 (79 gal) [3.7 mm] from wetland System 2 Hydraulic loading of the wetland systems in May 1997 was equivalent to about 1.9 inches/week for wetland System 1 and 2.8 inches of wastewater / week for wetland System 2 Under these conditions ET losses were 90% of influent in wetland System 1 and 59% in wetland System 2 Estimated hydraulic residence time in May 1997 was about 28 8 days for wetland System 1 and 19. 8 days for wetland System 2 The data indicate that hydraul i c loading in December 1997 was similar in wetland System 1 but had dropped in wetland System 2 to 1 7 inches/ week. Evapotranspiration losses were 41 % in wetland System 1 and 38% in wetland System 2

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158 costs of package plants are more than twice that of the wetlands ($15 400 vs $6 650) and maintenance costs are about ten times as great ($1,130 yr -1 vs. $120 yr-1 ) (Table 3-34 and Table 3-35) The wetlands are also expected to last longer as machinery especially in tropical conditions has a far shorter replacement time So on an amortized basis, the costs per year are even more divergent: over $2000 for the package plant vs $330 for the wetland ( even if the wetland only lasts 20 years as was assumed) Dependence on infrastructure is also greater for the package plant for since the system will not work without electricity to run grinders, pumps and blowers The wetlands relying on gravity flow for all movement of the sewage and on filtration by the limestone and bacterial/vegetative action for treatment of the sewage have mainly the requirement that filters be cleaned so that pipes do not clog The package plant also requires a supply of chlorine for disinfection since its hydraulic residence time (2-4 hours) is insufficient to achieve significant coliform bacteria reduction Emergy Evaluation Emergy evaluations of the limestone constructed wetland system are calculated in Table 3-36 and summarized in Figure 3-41 a summary diagram of emergy flows in the wetlands Wind is the largest environmental resource but environmental inputs constitute a small flow (< 1%) of total system emergy Local materials primarily Yucatan limestone contribute some 2% of emergy used in the wetland treatment process and are the predominant source of system emergy use apart from the wastewater The emergy contained in service and imported goods are less than 1 % of total emergy Emergy from local materials (Yucatan limestone vegetation mulch) constitute over 60% of total emergy used for construction of the wetland treatment units Operational costs

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159 Table 3-34 Purchased materials and services used in construction of wetland systems Akumal Mexico. Costs are expressed in Mexican pesos (1996) and converted to U.S. dollars at the rate of 7.8 peso / $ which was the exchange rate in 1996 when systems were bui lt. Item Quantity Cost per unit Cost Cost (U.S.$) esos Native Materials : Limestone gravel 72m3 1460 peso / 12 m3 8760 $1123 Limestone rock 12m3 1460 peso / 12 m3 1460 $ 187 Sand 21 m3 800 peso / 7 m3 2400 $ 308 Plants 327 variable some free 2200 $282 lmQorted Materials : Cement 105 50-kg bags 50 peso / bag 5250 $ 673 Lime 40 25-kg bags 15 peso / bag 600 $ 77 Steel rebar 15 X 12-m 48 pesos / piece 720 $ 92 PVC pipe 8 x 6-m, 10 cm 550 peso / piece 4400 $ 564 dia. Steel wire mesh 131 m2 3 mm dia 750 $ 96 Labor and Services : Backhoe rental 20 m3 excavated 450 peso / m3 9000 $1154 Jackhammer rental 25 m3 excavated 450 peso / m3 11250 $1442 Construction 3 people x 15 days 70 peso / day 3150 $ 404 laborers Plumber, labor 1 person x 1 week 1500 peso / week 1500 $ 192 Fuel and Power : Gasoline 60 liters 8 peso / liter 480 $ 62 Total Construction 51, 920 $6 656 Cost Maintenance costs: Labor and Services : Labor 104 hours / yr 70 pesos / 8 hrs 910 $117 Annual 910 $117 Maintenance Cost

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160 Table 3-35 Purchased materials and services used in construction and annual maintenance of package plant sewage treatment system, Akumal Mexico. Costs are expressed in Mexican pesos (1996) and converted to U.S dollars at the rate of7. 8 peso / $ which was the exchange rate in 1996 when system was built. Item Quantity Cost per unit ..... ....... --- --------............................ -.. --Native Materials : Sand 7m3 800 peso / 7 m3 lm:QQrted Materials : Concrete blocks 125 blocks 2 9 peso Cement 35 50-kg bags 50 peso / bag Rebar Steel 7.5 pcs x 12 m 48 pesos PVC Pipe 32x6m 550 pesos Jet system includes blowers, grinders motors Labor and Services : Construction labor 80 people / days 70 pesos Excavation of includes steel pipe injection well liner Fuel and Power : Gasoline 301 8 pesos Total Construction Cost Maintenance costs: lmgorted materials Chlorine 10 kg 40 pesos Labor and Services : Labor 150 hrs / yr 50 pesos Fuel and Power : Electricity 250 kWh/month 79 pesos Annual Maintenance Costs Cost (pesos) 800 362 1 750 360 17 600 70,200 5,600 23,400 240 Cost (U.S $) ----$102.30 $46 50 $224.40 $46 $2256 $9000 $718 $3000 $31 120 312 $15 425 400 $51.30 7500 $961.50 948 $121.50 8 848 $1, 134

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Sewage Limestone Wetland Treatment System 161 \ \ \ \ ,_ Annual Flows in E15 sej/yr \ \ I 7 Water 354.1 -----Flow of money Figure 3-41 Diagram of emergy and money flows in wetland treatment systems Akumal, Mexico. Units of diagram are E 15 sej/yr.

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162 Table 3-36 EmerID:'. anal ~ sis of the constructed limestone sewa~e wetlands Note Item Raw Units Emergy per Solar EmDollars Unit Emergy (Thousands) sej/unit E15 se"/ ENVIRONMENT 1 Sunlight 7 12E7 J / yr 1 < 0 001 2 Rain, chemical 5 85 E8 J / yr l.82E4 0 .01 0 .01 3 Rain, 2.58 E5 J / yr l.05E4 < 0.001 geopotential 4 Wind 7.4Ell J / yr 663 sej/J 0.49 5 Land 1.3 E8 J / yr 2.9E4 < 0.001 Total (renewable 0.48 0 35 resources) CONSTRUCTION ( divided by 20 INPUTS years) Local materials : 6 Gravel, 4.9E6 g/yr 1.0 E9 sej / g 4 9 3 577 limestone 7 Rock, 7.35E5 g/yr 1.0 E9 sej / g 0.74 0 54 limestone 8 Vegetation $14.1/yr 1.9 El2 sej / $ 0.03 0 0058 9 Mulch 4 5 E3 g/yr 2 75 E8 sej / g < 0 001 0 00007 Subtotal (local construction items 6-9 5 .67 4 14 inputs) Imported goods and services 10 Cement 0 3 ton/yr 6.4 E13 sej/ton 0 02 0 0015 11 Lime 5E4 g/yr 1 0E9 sej/g 0 05 < 0 001 12 Concrete block 0 5 ton/yr 6.4 El3 sej / ton 0 03 0 0022 13 Sand 1.48E6 g/yr 1.0 E9 sej/g 1.48 1.08 14 Rebar steel 15 lbs / yr 8.9 El 1 sej / lb 0.003 0 0022 15 PVC pipe 5 6E3 g/yr 9.26E7 sej/g < 0 001 < 0 001 16 Wire mesh 12 5 lb / yr 8 9 Ell sej /lb 0.001 < 0.001 17 Gasoline 1 .2 E8 J / yr 6 6E4 sej / J 0.008 0 0058 18 Rental of $57 7 / yr l.9El2 sej/$ 0.11 0 08 backhoe 19 Jackhammer $72 1 / yr l.9El2 sej / $ 0 14 0 1 rental 20 General labor 2.4 E7 J / yr 8 1 E4 sej/J 0 002 < 0 001 21 Plumber $9.6 / yr 1.9 El2 sej/$ 0 02 0 .01 22 Payment for $169 / yr l.9E12 sej/$ 0.32 0 .23 Goods

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163 Note Item Raw Units Transformity Solar EmDollars Sej/unit Emergy (Thousands) EIS sej / yr Subtotal imported Items 10-22 2 .18 1.59 goods and services Total inputs for 7 .85 5 .73 construction HUMANWASTE 23 Raw sewage 3.94 ES 8 .767Ell 345.4 252.13 gallons / yr sej / gallon OPERATION 24 Maintenance $117 / yr 1.9 El2 sej/$ 0 22 0 .16 Total emergy 354 1 258 5 OUTPUT (yield ) 25 Treated 5 .17El0 6 84 E6 sej/J 354 l 258 5 wastewater J / yr Column 6 (EmDollars) based on l.37El2 sej/$ U.S. dollar / emergy ratio for 1996 (Odum 1996) Notes : 1. SOLAR ENERGY Land area : 131. 8 m2 Insolation : 1.8 E2 Kcal/ cm2 / yr (World Energy Data Sheet) Albedo: 0 30 Energy (J) = (area) ( avg insolation) (albedo) = ( 131.8m2) (1.8E2KcaVcm2 / yr) (E4 cm2 / m2) (0 3 ) = 7.12 E7 2 RAIN CHEMICAL POTENTIAL ENERGY Land area = 131. 8 m2 Rain= 9.44E-l m/yr (1AM, U of Ga., 1988) ET= 9 (Lessing 1975 ) Energy (J) = (area) (ET) (rain density) (Gibbs # ) = 131.8m2 ( 9) (1000 kg/m3) ( 4.94 E3 J/kg ) = 5 85E8 J / yr

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Table 3-36 continued 3 RAIN, GEOPOTENTIAL Area= 131.8 m2 Rainfall= 1.050 (Lessing, 1975) AvgElev=2 m Runoff rate = 1 ( 1 ET) 164 Energy (J) = (area ) (%runoff) (rain density) (avg elevation)* (gravity) = 131.8m2 0 1 1000 kg/m3 2 9 8 m/s2 = 2 58E5 4 WIND Based on method given in Odum, 1996, p 294, with values of eddy diffusion and vertical gradient from Tampa Florida and using wind of 10 m height (10 m)(I 23 kg/cum) (2. 8 cu m/m/sec) (3. 154E7 sec / yr) (2.3 m/sec/ m)(130 sq m) = 7.4 Ell J / yr Transformity for wind from Odum 1996 p 186 All of purchased goods and services ( except annual maintenance) are divided by 20 (anticipated life of wetland) to give emergy / yr 5 LAND (EARTH CYCLE ) Transformity = 2.9E4 sej/J (Odum, 1996, p. 186) Energy= (land area) (heat flow per area) heat flows for old stable areas is 1E6 J / m2/yr (Odum 1996, p 296) Energy = 130 m2 1E6 J / m2 = 1.3 E8 J / m2 6. GRAVEL, LIMESTONE 72 m3 at cost of 1460 pesos /12 m3 = 8760 pesos / (7 8 peso /US.$)= $1123 Transformity oflimestone from Odum (1996 p 310 ), emergy / gram: 1E9 sej/g Weight oflimestone from Limestone Products, Newberry FL (pers comm ) : 3000 lbs/m3 72 m3 3000 lbs /m3 454 g/lb =9 8E7 g I 20 yrs = 4.9E6 g emergy in limestone gravel: 4.9E6 1E9 = 4 9E15 7 ROCK LIMESTONE : 12 m3 of 5-10 cm rock at 1460 pesos/7 8 peso / $ = $187 Transformity oflimestone from Odum (1996, p 310) emergy / gram : 1E9 sej/g Weight oflimestone 5-10 cm rock, from Limestone Products Newberry FL (pers comm.): 2700 lbs/m3 12 m3 2700 lbs / m3 454 g/lb = 1.47E7 g / 20 yrs= 7.35 E5 g

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165 Table 3-36 continued emergy in limestone gravel : 7 35E5 1E9 = 7.35El4 8 VEGETATION approx 2.5 plants per m2 planted, or 325 plants total ; purchased plants for total of2200 peso* $/7 8 peso= $282 / 20 yrs = $14 1 / yr 5 .2El2 sej / $ (emergy / dollar ratio from this study, see Table 3-64) = 7.33 El3 sej 9 MULCH 2 5 cm of sawdust and woodchip mulch (local and free) over 131 m2 = 3 28 m3 transformity based on that for pulp wood 2 75E8 sej/g (Christensen 1984 ) est. wt of mulch: 200 lbs* 454 g/lb = 9 1E4g / 20 yrs = 4 5E3 g/yr 4 5E3 2.75E8 = l.2El2 10. CEMENT (LOCAL MANUFACTURE) : 105 bags @ 50 kg/bag = 5250 kg ; price 50 peso/bag 105 = 5250 peso 5250 peso* $/7 8 peso = $673 Transformity of concrete from Brown and McClanahan (1992 p. 27) : 7E7 sej / g 454 g/lb 2000 lb /ton= 6.356El3 sej/ ton Concrete in wetland in cu yds : perimeter = 70 yds x 4 ( .11 yd) = 7.8 cu yd + bottom : 145 yd2 4 ( 0 .11 yd) = 16 cu yd ; 23.8 cu yd* 500 lb / cu yd (est. from concrete company)* ton/2000 lbs = 5 95 tons concrete 5 .95 tons / 20 yr lifetime = 0.3 tons / yr 11. LIME (LOCAL): 40 bags @25 kg/bag = 1000 kg ; price 15 pesos/bag* 40 bags = 600 peso* $/7 8 peso = $77 1000 kg/20 yr = 50 kg/yr using same transformity as for limestone: 1E9 sej / g 50 kg 1000 g/kg = 1El3 sej 12. CONCRETE BLOCK (LOCAL ) 250 blocks (40 cm x 20 cm x 15 cm) @2. 9 peso/block = 725 peso* $/7 8 peso = $93 using transformity of concrete from Brown and McClanahan (1992 p 27): 7E7 sej / g 454 g/lb 2000 lb / ton = 6.356E13 sej/ton est. wt of each concrete block = 20 lbs total wt 20 ,000 lb* ton/2000 lb = 10 ton / 20 yrs= 5 ton/yr 5 ton* 6 356E13 sej/ ton = 3.2El3 sej

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Table 3-36 continued 13. SAND (LOCAL) 166 21 m3 for 2400 peso total ; 2400 peso* $/7.8 peso = $308 est. wt of sand from Florida Rock Mines, Grandin, FL plant (pers comm.) : 3100 lbs/m3 transformity of sand using Odum (1996, p 310) for other Earth products : 1E9 sej / g 21m3 3100 lbs/m3 454 g/lb = 2 96E7 g / 20 yrs = 1.48E6 g 1.48E6 g 1E9 sej / g = 1.48E15 sej 14. REBAR STEEL 15 pcs 12 m length = 180 m; price 48 pesos/pc* 15 = 720 peso* $/7 8 = $92 transformity of steel and iron products from Odum (1996 p 193): 1 .78El5 sej / ton ton/2000 lb= 8 .9El lsej/lb est. wt of rebar : 15 pcs 20 lb / piece = 300 lbs / 20 yr lifetime = 15 lbs / yr 15 lb* 8.9El I = 1.34E13 sej/yr 15. PVCPIPE transformity for plastic from Brown et al, 1992, p 27 : 9.26E7 sej/g weight of PVC pipe (est.) 14 kg / 6 m piece* 8 pc = 112 kg* 1000 g/kg = 1.12E5 / 20 yr = 5.6E3 g/yr 5 6E3 g/yr 9.26E7 sej / g = 5.2 El 1 sej 16. WIRE MESH: 3 mm diameter 131 m2 ; total price = 750 pesos $/7 .8 = $96 transformity of steel and iron products from Odum (1996 p 193) : 1.78El5 sej / ton ton/2000 lb = 8 .9El 1 sej/lb est. wt of wire mesh : 250 lbs / 20 yr lifetime = 12. 5 lbs / yr 12. 5 lb 8 .9Ell = 1.34E13 sej/yr 17. GASOLINE gasoline for concrete mixer : 60 liter@ 8 peso / liter (est.) = 480 pesos* $/7 .8 peso = $62 Transformity for motor fuel from Odum (1996 p 308) : 6 6E4 sej / J 60 liter= 15 gal; bbl of oil = 42 gal ; barrel of oil = 6.28E9 J/bbl 15 gal/42 gal/bbl= 2.35E9 J / 20 = l.2E8 J / yr 1.2E8 J / yr 6 6E4 sej/J = 7.9El2 sej ** 18. BACK.HOE RENT AL 450 peso per 1 m3 of excavation : approx 20 m3 excavated= 9000 peso* $/7 .8 peso = $1154 $1154 /20 yr = $57 7 / yr l.9El2 sej / $ (Trujillo, 1998)

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167 Table 3-36 continued **19 JACKHAMMER RENTAL 450 pesos per 1 m3 of excavation : approx. 25 m3 excavated = 11250 pesos* $/7.8 peso = $1442 $1442 / 20 yr = $72 1 / yr * 1.9El2 sej / $ (Trujillo 1998) 20 LABOR Workers (general excavation and construction) : 15 days* 3 people* 70 peso / day = 3150 peso $/7. 8 peso = $404 transformity for primitive (uneducated labor) from Odum and Odum 1983 : 8 1E4 sej/J energy per person : 2500 Kcal/day* 4186 Kcal/J 45 days = 4 7E8 J / 20 yrs = 2.4E7 J / yr 2.4E7 J 8 1E4 sej/J = 1.9El2 21. PLUMBER LABOR 7 days* 1 person = 1500 pesos* $/7 8 peso = $192 I 20 yrs = $9.6 / yr 1.9E12 sej / $(Trujillo, 1998) 22. PAYMENT FOR GOODS Monetary expenditures included limestone gravel: 8760 pesos limestone rock : 1460 pesos cement: 5250 pesos lime : 600 pesos, sand : 2400 pesos PVC pipe : 4400 pesos steel rebar : 720 pesos wire mesh : 750 pesos vegetation : 2200 pesos and gasoline : 480 pesos for a total of 27,020 pesos / 7 8 pesos per dollar = $3464 U.S. dollars / 20 yrs = $173 per year 1.9E12 sej / $(Trujillo 1998) 23 HUMAN WASTE Yearly sewage = 36 people* 30 gal/day 365 days / yr = 3 94 E5 gallons / yr Transformity based on emergy per person Since emergy per person in U.S. = 32 El5 sej/yr and that for Mexico = 8 El5 sej/yr (Odum et al 1998) we will use an in-between average emergy since Akumal system is unlike typical Mexican one because of tourist economy : 16 E 15 sej/yr Total wastewater per person = 50 gal/day* 365 days = 18250 gallons Transformity : 16 E15 sej / 1.825 E4 gallons = 8 767 Ell sej/gallon

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168 Table 3-36 continued 24 OPERATION (est.) 2 hours/week 52 weeks = 104 hr for gardener / handyman @ 70 peso / 8 hours = 910 peso* $/7.8 peso = $117 $117 l.9E12 sej / $(Trujillo 1998) 25. OUTPUT (yield): TREATED WASTEWATER Chemical potential of yearly inputs of raw sewage : Yearly treated wastewater = 1493 2 m3/yr-(1493 2m3 .3 (evapotranspiration loss)) = 1045.2m3 Water : (1045 2 m3/ yr) (10E6 g/m3) (4 94 J ig)= 5 17E10 J Transformity : 354.1 E15 sej I 5.17 ElO J = 6.85 E6 sej / J ** in systems which don t have hard limestone excavation ( e .g. beach sand sites) excavation costs are 6400 peso or 14, 000 pesos less expensive ; 14000 $/7.8 peso = $1794 less expensive

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169 total less than 3% of total construction emergy The wetland system discharges less treated wastewater than it receives since about 30% are used in transpiration by the vegetation. By contrast emergy analysis of a package plant sewage treatment system (Table 33 7 and Figure 3-4 2 ) built for a comparable number of residents in Akumal shows the far higher use of purchased services and imported resources that such highly technical systems use There was very little use of renewable resources The largest emergy flows ( apart from wastewater) are that of imported goods and services, mainly representing the costs of imported machinery and high maintenance labor costs by technical personnel. Imported resources are more than 100 times higher than those of the constructed wetland) as might be expected as equipment and technical processing is substituted for the large buffering and retention the use of limestone gravel permits in the wetland systems. Operational costs of the package plant are around ten times higher than the wetland system ($1100 vs $ 1 17) and emergy in services are eighteen times higher (3 7 E 15 sej/yr vs. 0 2 E15 sej / yr) The transformity of treated water from the package plant is 4.83 E6 sej/J, which is about 30% lower than the transformity for the wetland system (6 85 E6 sej / J) reflecting the greater quantity of discharged water in the package plant, since virtually all input water to the system is discharged. The empower density of the package plant is about three times higher than that of the wetland system (7 1 El9 sej/ha vs 2 5 El9 sej/ha) since such a highly technical system occupies requires less land area

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Sewage <0.001 170 Operation 1.91 I I \ I \ \ \ \ \ \ \ \ ' I \ ...... ;:::r -,Package Plant Water Sewage Treatment Annual Flows in E15 sej/yr -----Flow of money Figure 3-42 Diagram of emergy and money flows in package plant sewage treatment systems, Akumal, Mexico Units of diagram are E15 sej/yr. 356 2

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171 Table 3-37 Emergy analysis of package plant sewage treatment system Note Item Raw Emergy per Emergy EmDollars Units Unit El5 Thousands ................... ....................... sej/unit se"_I.Y!_ ENVIRONMENT 1 Sunlight 2 75 E7 1 < 0.001 < 0 001 J / yr 2 Rain, chemical 2.2 E8 1.82E4 sej / J 0.004 0.002 J / yr 3 Rain, 9.8E4 1.05E4 sej/J < 0 001 < 0 001 geopotential J / yr 4 Land 5 E7 J/yr 2 9 E4 sej/J <0.001 Total (Environment) 0 004 0 002 CONSTRUCTION Divided by 20 INPUTS years except machinery divided by 5 years Imported goods and seTV1ces 5 Cement 0.3 ton/yr 6.4E13 0 002 001 sej / ton 6 Concrete block 0.0625 6.4E13 0.004 002 ton/yr sej/ton 7 Sand 5E5 g/yr 1.0 E9 sej / g 0.5 0.4 8 Rebar steel 7.5 lbs / yr 8 9 Ell 0.007 005 sej/lb 9 PVC pipe 2 24E4 9 26E7 sej/g 0 002 001 g/yr 10 Gas for concrete 6 E7 J / yr 6.6E4 sej / J 0 004 002 rmxer 11 Machinery 2.27E5 1. 25E 1 0sej / 2 8 2.0 g/yr g 12 Excavation of $150/yr 1.9 E12 0 29 0.2 injection well sej/$ 13 "Jet system" $1800 / yr 1.9 E12 3.42 2 5 cost sej / $ 14 General labor 4.2E7 J/yr 8 1 E4 sej/J 0.003 .002 Total construction 7 03 5 13 inputs HUMANWASTE 15 Raw sewage 3 94 E5 8 767 Ell 345.4 252.13 ~allons/yr sej/~allon

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172 Note Item Raw Emergy per Emergy EmDo11ars Units Unit E15 Thousands sej/unit sej / yr OPERATION 16 Electricity 1. lElO 1.74E5 sej/J 1.9 1.4 j / yr 17 Maintenance $961.5 / yr 1.9 E12 1.83 1.34 sej/$ 18 Chlorine 1E4 g/yr 1.1E9 sej / g 0.01 008 Total Operation 3 74 2 73 Total emergy 356.2 260 OUTPUT (yield) 19 Treated 7.38 ElO 4 95 E6 356 2 260 wastewater J sej / J Column 6 (EmDollars) based on 1.37E12 sej/$, U.S dollar / emergy ratio for 1996 (Odum, 1996) Notes: 1. SOLAR ENERGY Land area : 50 m2 Insolation: 1.8 E2 Kcal/cm2 / yr (World Energy Data Sheet) Albedo: 0.30 Energy (J) = (area) (avg insolation) (albedo) = (50m2) (1.8E2Kcal/cm2/yr) (E4 cm2 / m2) (0.3) = 2.75 E7 2. RAIN, CHEMICAL POTENTIAL ENERGY Land area = 50 m2 Rain= 9.44E-1 m/yr (1AM, U of Ga., 1988) ET= 9 (Lessing, 1975) Energy (J) = (area) (ET) (rain density) (Gibbs#) = 50m2 (.9) (1000 kg/m3) (4 94 E3 J/kg) = 2.2 E8 J/yr 3. RAIN, GEOPOTENTIAL Area= 50 m2 Rainfall= 1.050 (Lessing 1975) AvgElev=2 m

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Table 3-37 continued Runoff rate = 1 ( 1 ET) 173 Energy (J) =(area)* (%runoff)* (rain density)* (avg elevation)* (gravity) = 50 m2 0 1 1000 kg/m3 2 9 8 m/s2 = 9 .8E4 4. LAND (EARTI-1 CYCLE) Transformity = 2 9E4 sej/J (Odum 1996 p 186) Energy = (land area ) (heat flow per area) heat flows for old stable areas is 1E6 J / m2 /yr (Odum, 1996 p. 296) Energy = 50 m2 1E6 J / m2 = 5 E7 J / m2 5 CEMENT 35 bags @ 50 kg/bag = 1750 kg; price 50 peso/bag 35 = 1750 peso 1750 peso $/7 8 peso = $224.40 Transformity of concrete from Brown and McClanahan (1992 p 27) : 7E7 sej/g 454 g/lb 2000 lb / ton = 6.356 El3 sej / ton Concrete in system in cu yds : 6 cu yd; 6 cu yd* 500 lb /cu yd (est. from concrete company)* ton/2000 lbs = 1.5 tons concrete 1.5 tons I 20 yr lifetime = 0.75 tons/yr 6 CONCRETE BLOCK 125 blocks (40 cm x 20 cm x 15 cm) @ 2 9 peso/block = 362 peso* $/7 8 peso = $46.50 using transformity of concrete from Brown and McClanahan ( 1992 p 27) : 7E7 sej / g 454 g/lb 2000 lb / ton = 6.356El3 sej/ton est. wt of each concrete block = 20 lbs total wt 2500 lb ton/2000 lb = 1 25 ton / 20 yrs = .0625 ton/yr 0625 ton* 6.356El3 sej/ton = 3 97E12 sej 7 SAND 7 m3 for 800 peso total ; 800 peso $/7 8 peso = $102 est. wt of sand from F lorida Rock Mines Grandin, FL plant (pers comm. ) : 3100 lb s/ m3 transformity of sand using Odum (1996 p 310) for other Earth products: 1E9 sej / g 7m3 3100 lbs / m3 454 g/lb = 0 98E7 g / 20 yrs = 5E5 g 5E5 g 1E9 sej / g = 5E14 sej 8. REBAR STEEL 7 5 pcs 12 m length = 90 m ; price 48 pesos /pc* 15 = 360 peso* $/7.8 = $46

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174 Table 3-37 continued transformity of steel and iron products from Odum (1996, p. 193) : 1.78El5 sej/ton ton/2000 ]b = 8 9El lsej/1b est. wt ofrebar: 7.5 pcs 20 lb/ piece = 150 lbs / 20 yr lifetime = 7 5 lbs / yr 7.5 lb* 8 .9Ell = 6 .7El2 sej/yr 9 PVCPIPE 10 cm diameter 32 pc x 6 m = 192 m ; price 17,600 pesos* $/7 8 = $2256 transformity for finished product use average emergy / dollar ratio for Mexico : 5 5El 2 sej / $ (source?) $2256 / 20 yr = $113 /yr* 5 5 E12 sej / $ = 6 2E14 transformity for plastic from Brown et al 1992 p 27 : 9.26E7 sej/ g weight of PVC pipe (est.) 14 kg / 6 m piece* 32 pc =448 kg* 1000 g/kg = 4.48E5 /20 yr = 2 24E4 g/yr 2.24E4 g/yr 9 26E7 sej /g = 5.2 El I sej 10. GASOLINE gasoline for concrete mixer: 30 liter@ 8 peso/liter (est.)= 240 pesos* $/7.8 peso= $31 Transformity for motor fuel from Odum (1996, p 308) : 6.6E4 sej/J 30 liter = 7 5 gal; bbl of oil = 42 gal; barrel of oil = 6.28E9 J/bbl 7 5 gal/42 gal/bbl = 1 175E9 J / 20 = 6E7 J / yr 6E7 J / yr 6 6E4 sej/J = 4E12 sej 11. MACHINERY 2 blowers 2 HP engine grinder 2 check valves, 2 u-joints estimated weight: 1500 lbs ; divided by 3 years (expected life)= 500 lb* 454g/1b = 2 27E5 g Transformity = 1.25E10 sej / g (Odum et al, 1983, p. 432) 12. EXCAVATION OF INJECTION WELL $3000/20 yrs = $150 13. JET SYSTEM Jet system costs : including machinery parts bacterial media, filters: $9000 / 5 yr life = $1800 1.9E12 sej/$(Trujillo 1998)

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Table 3-37 continued 14. LABOR 175 Workers (general excavation and construction) : 20days *4 people* 70 peso / day = 5600 peso $/7.8 peso = $718 transformity for primitive (uneducated labor) from Odum and Odum 1983: 8 1E4 sej / J energy per person : 2500 Kcal/day* 4186 Kcal/J 80 days = 8.37E8 J / 20 yrs = 4 2 E 7 J / yr 4.2E7 J 8 1E4 sej / J = 3.4E12 15. RAW WASTEWATER Yearly sewage = 36 people* 30 gal/day 365 days/yr = 3 94 E5 gallons / yr Transformity based on emergy per person Since emergy per person in U.S.= 32 El5 sej / yr and that for Mexico = 8 E15 sej/yr (Odum et al 1998) we will use an in-between average emergy since Akumal system is unlike typical Mexican one because of tourist economy : 16 E 15 sej/yr Total wastewater per person = 50 gal/day 365 days = 18250 gallons Transformity : 16 E 15 sej / 1.825 E4 gallons = 8. 767 E 11 sej/gallon 16. ELECTRICITY estimate for operating system : 250 kWh/month = 3000 kWh/yr Transformity for electricity taken as mean global value = 173 681 sej / J (Odum 1996 p. 305) Electrical energy = ( 3000 kWh)* (3. 606E6 j/kWh) = l.lElO J 17 . MAINTENANCE LABOR: estimated at 3 hrs / week of' 'technician = 150 hrs/yr@50 pesos/hr = 7500 pesos*$ /7 8 pesos = $961 50 l.9E12 sej / $(Trujillo 1998) 18 CHLORINE 10 kg used per year ; 400 pesos cost; transformitytaken as equiv to potassium chloride = 1.1E9 sej / g (Odum 1996 p 310 ) 10 kg lO00g/kg = 1 E 4 g/yr 19. OUTPUT (yield): 'IREATED WASTEWATER Chemical potential o f yearly inputs of raw sewage : Yearly treated wastewater = 1493 2 m3 / yr Water : (1493.2 m3 / yr) (10E6 g/m3) (4 94 Jig) = 7 38 ElO J Transformity : 356 2 El5 sej / 7.38 ElO J = 4 .83 E6 sej / J

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176 Receiving Wetland -Groundwater Mangroves Biodiversity Biodiversity in the mangroves near the discharge was determined by transects of 1000 observations made in December 1997 before effluent was released to the system Total number of plant species was 17 (Table 3-2) The Shannon Diversity Index was 1.49 (base 2) and 0.45 (base 10 ) in December 1997 (Table 3-5) White mangrove ( L agun c ularia rac e mo s a) is the most dominant plant in the wetland, accounting for some 84% of observations in the December 1997 transect and over 75% of tree stems in the discharge area Mangrove Soils The mangrove soils had an average water content of 72% and dry weight averaged 27.4% 1.7% in six soil samples taken in December 1997 (Table 3-38 ) Bulk density in five samples taken to 31-35 cm depth with a 2 1 cm diameter soil corer showed that bulk density averaged 0 060 0 003 g/cm3 (Table 3-39) Organic matter averaged 76 5 0.8% in five soil samples (x 3 replicates) collected in December 1997 ( Table 3-40) Variability amongst the five soil samples ranged from one sample with a mean of 79.4 0.3% and the lowest organic matter content in a sample with a mean of72. 5 0 1 %. X-ray diffraction and scanning electron microscope analysis of the mineral portion of mangrove soil samples revealed the presence of calcite amorphous silica and the aragonite form oflimestone. All the peaks on the X-ray diffraction analysis were small with calcite being the most abundant mineral. Some slight presence of weddelite ( calcium oxalate

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177 Table 3-38 Wet weight/dry weight of soils in mangrove receiving wetland, December, 1997. Sample No. 1 2 3 4 5 6 Average standard error of the mean Wet Weight kg Dry weight kg ... .. .... ____..~---. -. 0.634 0 129 0.099 0 079 0.094 0 099 0.099 0.029 0.024 0.029 0 029 0.024 Percent dry weight/wet weight 20.3 29.3 30.4 30. 9 29.3 24.2 27.4% 1.7%

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178 Table 3-39 Bulk density of soils in mangrove receiving wetland December 1997 Sample Volume Dry weight Bulk density cm3 grams grams / cm3 1 473 29 0.061 2 468 24 0 051 3 439 29 0 066 4 443 29 0 065 5 439 24 0 055 Average standard error of the mean 0.060 0 003

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179 Table 3-40 Organic matter content of soils in mangrove receiving wetland estimated from loss on ignition and mean values of the five soil samples December 1997. Soil Sample 1-1 1-2 1-3 1-4 1-5 Mean Standard error of the mean Number of samples 3 3 3 3 3 Mean percentage loss on ignjtion standard deviation of the mean 73.2 0.1 79 1 0.1 79.4 0.3 78.4 0 1 72.5. 1 76.5 0 8

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180 hydrite, C2CaO4 2H2O ) detected by the X-ray diffraction may have been a secondary product resulting from the preparation procedure (Dr. W Harris pers. comm .) Ash remaining after combustion for determination of organic matter was analyzed by inductive coupled plasma spectroscopy for calcium and magnesium content (Table 3-41) These results indicate that 41.9 +/1.3 percent is calcium and 3 2 +/-0.1 is magnesium Calcium thus constitutes a sizeable portion of the 23.5% non-organic portion of the mangrove soils and if present as calcium carbonate would account for virtually all of the inorganic material. Depths of the mangrove wetland s organic soil were measured (Figure 3-43) to ascertain if there were limestone outcrops or cenotes in the vicinity of the outfall location which might prevent sufficient residence time to permit filtration and uptake of nutrients in the effluent. The results were mapped (Figure 3-44 ) showing that within a 15 meter radius of the outfall, soil depths varied from 33 to 55 cm before limestone rock was encountered Average depth was 41. 6 cm. No consistent pattern emerged, so an isopach could not be generated from the data although many of the deepest soil depths were found close to the outfall site and to its south (where soils averaged 48 cm deep along an axis 15 m long). Nutrients Sampling tubes were installed in the mangrove receiving wetland to determine water nutrient content before and after discharge Sample point A was 1 1 m upstream from the point of outfall B was 1.1 m downstream C was 3.25 m downstream D was 6 1 m downstream and sample point E was 12 m southeast of discharge and closer to the edge of the wetland area Before treated effluent discharge began nitrogen content of the mangrove soils

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181 Table 3-41 Calcium and magnesium content of mangrove soil ash after combustion for organic content. Results determined by inductive coupled plasma spectroscopy Sample 1 2 3 4 5 Average standard error of the mean Calcium % 40 1 42 8 39.1 41.3 46.4 41.9 1.27 Magnesium % 3 38 3.46 3.15 3.15 3 07 3 24 0.08

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Figure 3-44 Howard T. Odum inspecting root penetration and peat depth in mangroves AktunaJ December 1997 00 N

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183 38 39 38 Line of flow 41 38 35 33 34 WI I I 33 I 1 "' 1 33 34 33 35 ~~c-o--1 --1 --1 E 52 Thickness of peat in cm. 38 Discharge point for treated effluent 51 53 E 44 Scale s 6m. Figure 3-44 Th i ckness of mangrove peat in the receiving wetland around the outfall pipe discharging effluent December 1997 See Figures 1-8 for location of mangrove discharge point in Akumal. Mangrove soil samples were collected 1 3 5 and 10 m from discharge point in N,S E and W directions (Tables 3-43 and 3-45) Water samples were collected at 1 m upstream (A) 1 m (B), 3m (C) and 6 m (D) downstream and 15 m (E) SE of discharge point (see Figure 1-9)

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184 was 1.58% +/ 02% ( Table 3-42) with a range from a low value of 1.44% N to a high of 1.74% N Table 3-43 presents nitrogen levels measured at specific distances from outfall in the mangrove wetland prior to and after discharge of treated effluent. Nitrogen levels measured lm from discharge point of the effluent showed about a 7% increase after 4 months ofreceiving the treated sewage (from 1.68% to 1.79% nitrogen) However this increase may be due to other factors as the increase at 3m from discharge was 11% at 5m was 9% and 10m was 9% (Table 3-43) Nitrogen increase over pre-discharge levels totaled 18% for the South 1-lOm samples 6% for the East 1-lOm and 5% for both North and West 1-lOm In December 1997 phosphorus levels in the mangrove soils averaged 0.32% +/ 0.006% (Table 3-44 ) These nutrient concentrations may have been caused by anthropogenic additions to the s i te as construction workers during this period used the wetland as an outdoor bathroom In the mangrove soil samples from April August 1997 phosphorus was measured at lower levels ranging from 0 065% to 0 115% (Table 3-47). Table 3-47 shows analyses of mangrove soil from just before to four months after discharge commenced, which reveal increases in phosphorus levels of 5-10% . At lm distance from outfall P levels were 7% above those pre-discharge and at 3m were unchanged, at 5m were + 7% and 9% at 10 m. Only in the South ( + 14%) and West ( + 3%) direction samples were phosphorus levels higher than pre-discharge East and West direction soils samples were 5-6% lower (Table 3-47)

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185 Table 3-42 Total Kjeldahl nitrogen content of soils in mangrove receiving wetland on 12 December 1997 before discharge of treated eflluent. December 1997 mangrove soi] samples Total Kjeldahl nitrogen g/kg 1 14.4 2 14.4 3 14. 2 4 16. 2 5 16. 4 6 15. 8 7 16.4 8 15.2 9 16. 8 10 16. 6 11 17.4 12 16. 0 13 16. 6 14 15. 6 15 15.8 mean standard error of the mean 15.9 2.5 .. Laboratory accuracy with nitrogen standard + 3.1 %

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186 Table 3-43 Total Kjeldahl nitrogen content of soils in mangrove receiving wetland before discharge (30 April 1998) and 2 months (3 July 1998), 3 months (3 August 1998) and 4 months (2 September 1998) after discharge of treated effluent began 3 May 1998 -------_.., ... ----Sample # of 30Apr 3 Jul 1998 3 August 2 Sep 1998 Percent Location Samples 1998 Total 1998 Total change (Distance n Total Kjeldahl Total Kjeldahl from 30 from Kjeldahl Nitrogen Kjeldahl Nitrogen Apr 1998 discharge) Nitrogen g/kg Nitrogen g/kg to 2 Sep g/kg .... g/kg 1998 data . .... -- East Im 3 17 7 0 2 18.2 0 6 19 0 0.4 17.3 0.3 -2% East3m 3 15.4 0.4 16.6 04 16.8 0.3 17 6 0 3 + 14% East 5m 3 16.2 0.5 17 7 0 2 18.7 0.4 16.8 0.3 +4% East 10m 3 15. 1 0 6 16. 8 0 2 18.0 0.3 16. 3 0 5 +8% West Im 3 16.6 0 2 17.8 0.3 15. 9 0 6 18 .1.4 + 9% West3m 3 17.9 0 6 17.8 0 2 18. 6 0 8 18.6.1 +4% West 5m 3 16.3 0 7 18.0 0 3 19.6 0.4 18 1 0.6 + 11% West 10m 3 17 5 0.4 16. 3 0 3 16. 8 0.6 17.0 0 3 -3% North Im 3 16.8 0 7 15.9 0.2 17 0 0.6 18.5 0.3 + 10% North3m 3 16.3 0 3 19. 3 0 1 18.5 0.3 17. 5 0 2 +8% North 5m 3 17.4 0 3 18.2 0.5 20 1 0.3 17 .7.2 + 2% North 10m 3 18.0 0 2 18.4 0.3 19.5 0.6 18. 0 0 3 No change South Im 3 16.1. 1 17.4 0.4 18.9 0.4 17.8 0.4 + 11% South3m 3 14 7 0 3 17 6 0 6 19.6 0.8 17.6 0.5 + 19% South5m 3 14 8 0 8 16. 9 0.4 17.3 0 2 17 5 0 3 + 19% South 10m 3 13. 5 8 16 7 0 3 17.4 0.6 16 7 0.2 + 24% Average Im 12 16. 8 17 3 17.7 17.9 + 7% Average3m 12 16. 1 17 8 18.4 17.8 + 11% Average5m 12 16.2 17 7 18.9 17 6 + 9% Averagel0m 12 16.0 17 1 17 9 17.0 +7% Average East 12 16. 1 17.3 18 1 17 0 + 6% Average West 12 17.1 17.5 17.7 18 0 +5% Average North 12 17. 1 17.9 18. 8 17 9 + 5% Average S2u~12 14 8 17.2 18 3 17.4 + 18% Laboratory accuracy with nitrogen sta~dard 4.2% (April & August 1998) -3. 1 % (July and September 1998)

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187 Table 3-44 Phosphorus content of soils in mangrove receiving wetland on 12 December 1997 before discharge of treated etlluent. December 1997 mangrove soil samples Total phosphorus g/kg 1 3.7 2 3.3 3 3.5 4 3.2 5 3.3 6 3.1 7 2.9 8 3.0 9 3.1 10 2.9 11 3.1 12 3.3 13 3.3 14 3.4 15 3.5 Average standard error of the mean 3.2 0.1 ,...., ,.,.~ "t' *" ,J:-,..~, ~, r--1. a.... a:#"~~~---,.,. ___ :-.t,, ,. .t .;. ~.._,it r: ,,ia tt.t=t.1-.t~~..._,:. tH.r.:. .c-,1,t. he e, i-1\., .,.. tJ-..>, ~ J Laboratory accuracy with phosphorus standard +2.4%.

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188 Table 3-45 Phosphorus content of soils in mangrove receiving wetland before and after discharge began May 3 1998. ~. .... .... .-: .. ... !Jl,:~:r:~t ,. ,:, ..... .. .. .. ,........ ,:... -~ ... ....... :.n~-... Sample # of Location samples (Distance n from discharge) 30 Apr 1998 Total Phosphorus g/kg 3 Jul 1998 Total Phosphorus g/kg . ... .. . . . . .. . . .. . .. . . . . I o East lm 3 0.88 0.03 1.08 0 03 East 3m 3 0.86 0.02 1.06 0.03 East 5m 3 0.90 0.02 0.94 0.06 East 10m 3 0.99 0.03 1.04 0.03 West lm West3m West 5m West 10m North lm North3m North 5m North 10m South Im South 3m South 5m South 10m Average Im Average3m Average5m Average I Om 3 3 3 3 3 3 3 3 3 3 3 3 12 12 12 12 0.88 0.06 0.91 .05 0.90 0.07 0.90 0.05 0.89 0.01 0.81 0.04 1.13 0.09 1.15 0 02 0.76 0.03 1.03 0.01 0.90 0.04 0.93 0.04 0.84 0.07 0.79 0.05 0.76 0.04 0.72 0.04 0.99 0.06 1.03 0.07 0.86 0.03 1.00 0.07 0.92 0 03 1.08 0.07 0.98 0.05 1.04 0.04 0.88 1.01 0.88 0.97 0.89 0.91 0.96 0.96 3 Aug 1998 Total Phosphorus g/kg 2 Sep 1998 Percent Total change Phosphorus from 30 g/kg Apr 1998 .. . .. 0 65 0.01 0.90 0.03 0.87 0.07 0.84 0 07 1.04 0.04 0.93 0.05 0.91 0.07 0.69 0.03 0.99 0.01 1.00 0.03 0.81 0.04 0.96 0.02 0.98 0.13 0.98 0.09 0.87 0.06 0.92 0.05 0.97 0.04 0.77 0.03 0.85 0.09 0.71 0.04 0.85 0.09 0.81 0.03 0.90 0.09 0.78 0.03 0.79 0.04 1.10 0.09 1.16 0.06 1.00 014 1.05 0.08 1.11 .08 1.15 0.06 1.05 0.05 0.85 0.94 0.92 0.88 0.98 0.96 0.96 0.86 to 2 Sep 1998 data + 2% -2% +3% -30% + 12% + 6% + 10% -18% + 1% -21% -3% +3% + 11% + 16% + 20% + 8% +7% No change + 7% -9% Average East 12 0.91 0.87 0.87 0.84 -6o/o Average West 12 0.95 0.91 0.91 0.97 +3% Average North 12 0.81 0.89 0.89 0.77 -5% .A":e~~ge_ S ~!Jth _. ____ 12 0.84 1.04 0.94 --~----1.06 + 14% and September 1998). -----------------

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189 Hydrogeology of Coastal Zone Cross Section Figure 3-45 presents a systems diagram of the effluent-receiving salt-fresh wetland in the treatment system The driving energy sources are sun and wind while rain tidal exchange inland freshwater groundwater inflow and wastewater effluent contribute to the hydrology of the ecosystem. A geological cross-section of the coastal area (Figure 1-3) shows that the natural wetlands along the coast are located in the collapse karst zone where seawater and freshwater mix leading to dissolution of limestone These wetlands are dominated primarily by mangrove-type vegetation except where limestone rocks provide elevated hammocks F i gure 1-9 presents a map showing the relationship of the wetland treatment units and the mangrove discharge and sampling areas in Akumal. Ground Water Measurements of water levels in three piezometer tubes in the mangrove receiving wetland enabled calculation of water flowlines The difference between the three piezometers was slight, only 3 / 8 inch (0 95 cm) although they were separated by 10-14 meters (Figure 3-46) Directions to the three piezometers were established from a reference point by surveyor transit level. These calculations showed that line of groundwater flow was approximately in an easterly direction. Changes in tidal range may be expected to change the gradient of flow but not its direction Chart recorder data tracking changes in water levels in the mangrove wetland in a nearby cenote (near to the edge but outside the wetland) and at the seaside at Yal-Kul lagoon in Akumal showed that the mangrove soils had a large impact in lessening tidal fluctuations

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Wastewater Mangroves 190 Figure 3-45 Sy stems diagram of the mangrove wetland receiving treated effluent.

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--A.-B 14.3 rn \ \ \ \ \ \ \ \ \ \ -\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ Une of floW -------~ Ang\es fTQrn O (suNe'/ transit): o-P.:. S3~ de
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-192 larger than would be expected by mere distance from the ocean. For example chart recording data from May 27-28 1997 (Figures 3-47 and Figure 3-48 ) showed that the cenote near the mangrove had total water level changes less than half as great as the ocean Water level changes totaled 22.5 cm in the cenote while tidal flux at Yal-Ku totaled 48 5 cm. Also, the amplitude of the tides were less : 26 cm at Yal-Ku and 16.5 cm in the cenote The mangrove wetland had considerably less water level changes than the cenote despite the fact that both are nearly equidistant from the ocean ( and in fact the mangrove wetland where the chart recorder was placed is some 5-10 meters closer to the sea). For example during December 10-14 1997 total water level change in the mangrove was some 17 cm as contrasted with 119 cm in the cenote and 246 cm in tidal changes at Y al-Ku Lagoon (Figure 3-49 Figure 3-50 Figure 3-51 ) The greatest amplitude change in the mangroves was 7 cm while the shorter sharper tidal fluxes in the cenote was as high as 21 cm and the tidal range at Yal-Ku reached 28 cm. Water Quality in Mangroves Total nitrogen Table 3-46 presents results of nitrogen analyses of water in the mangroves before and after discharge of treated effluent Pre-discharge total nitrogen concentrations average around 4 mg/1 in the discharge area of the mangroves. After 3.5 months of receiving treated effluent nitrogen concentrations in mangrove water were increased to 9-12 mg/1 in sites close to the discharge location Increases o f total nitrogen were 57 mg/liter in sampling sites 1-3 m from the discharge but returned to background levels by 6 m distance (Table 3-46).

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E u Cl) > G) '--Cl) 1 (U <1) u :l en C Cl) a C: (U .c u 193 2 16 - I 12 8 4----+- 0 0 N < 0 0
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(I) > Cl) I.. 28 20 (tl Cl) u :J en C 12---.-C: (tJ .c u 8----.4-- 0 0 0 0 N N 25 May 97 194 -. 0 0 0 0 N -q' N 26 May 97 .. - 0 0 N 27 May 97 -\ -- 0 0 0 0 N N ~, 28 May 97 Figure 3-48 Chart recorder water levels at Y al-ku lagoon, showing tidal record, 27-28 May 1997.

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. E u .. Cl) -"
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196 3?---------------------------i (I) > (I) 2820 m 3: (I) u 16 ::, Cl) C 12 C m .c: u 8--+-4_____..._ 0 0 N ...0 0 N ...0 0 N ...0 0 N ...10 Dec 97 11 Dec 97 12 Dec 97 13 Dec 97 Figure 3-50 Chart recorder water levels in cenote near wetland systems 10-14 December 1997 0 0 N ...14 Dec 97

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1.97 2 E u 2.ur--1-,.-CJ) > CJ) (I) -2 m 3: CJ) u :J 16 Cl) C CJ) 01 C m 12 .c u 8 4 -0 0 0 0 CO 0 O N 0 0 0 0 CO 0 0 N 0 0 0 0 co 0 o N 10 Dec 97 11 Dec 97 12 Dec 97 Figure 3-51 Chart recorder water levels at Yal-ku lagoon, showing tidal record 10-14 December 1997. I I 0 0 0 0 co 0 0 N 13 Dec 97

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198 Table 3-46 Total nitrogen in water of mangroves before and after discharge of treated wastewater Before discharge : Sample 12Dec 3Mar 30Mar 30Apr Average Location 1997 1998 1998 1998 standard Total Total Total Total error of mean nitrogen nitrogen nitrogen nitrogen Total mg/I mg/I mg/I mg/I nitrogen ~-~---h------~ -----~----------m g/ 1 ______ A 1 m upstream 8.2 1.1 1.6 5 5 4.1 1.7 B 1 m 7 7 0 2 2 5.1 3 .8.7 downstream C 3 m 10. 3 2.4 2 8 3 6 4 .8 .9 downstream D ,6m 5 9 2 2 3 1 4.3 3 9 .8 downstream E 12 m S E 9 7 2 3 4 9 9 2 6.5 .8 After discharge : Sample 31 May 30 Jun 1998 1 Aug 1998 19Aug Average Location 1998 Total Total 1998 standard error Total nitrogen nitrogen Total of mean nitrogen mg/1 mg/1 nitrogen Total nitrogen --.. -~---..... -.. ---------.... mg/1 ---~-----mg/1 -mg/I ........... A 1 m upstream 7.6 7 3 14 8 13. 5 10.8 2.0 B, 1 m downstream 2 9 1 7 20. 2 10.1 8.7 .3 C 3 m downstream 1.3 9 .8 21.5 15. 7 12 1 .3 D 6 m downstream 0.9 3 5 3 1 3.0 2 6 0 6 E, 12 m SE 4 9 0 2 3 2 2.2 2.6 1 0

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199 Soluble reactive phosphorus Analyses of soluble reactive phosphorus in the mangrove water before and after discharge of treated effluent are presented in Table 3-47 Before discharge soluble reactive phosphorus varied from 0.9 1.2 mg P / liter on average in mangro v e water. After 3.5 months of discharge locations 1 m distant had increased phosphorus levels by 2-3 mg/liter but showed less increase at 3m from the discharge point. The sampling location 6m distant showed similar phosphorus concentrations to background levels in the mangrove (Table 3-47) Chemical oxygen demand Analyses of chemical oxygen demand (COD) in mangrove water are presented in Table 3-48. Mangrove water prior to discharge ranged from 60-160 COD mg/1. After 3.5 months of receiving treated effluent sampling sites lm from discharge location had COD concentrations around 1 50 mg/1, and showed a decline in COD with distance from the discharge By 6m distance COD concentration was below that shown pre-discharge for that sampling location and was below background levels of COD in the mangrove ( Table 3-48). Total suspended solids Total suspended solids (TSS) were examined in the mangrove before and after the discharge of treated effluent (Table 3-49). Pre-discharge levels ranged from an average of 280-360 with high variability (over 25% in some cases). After 3.5 months ofreceiving treated effluent there was on average significant decline in suspended solids in the mangrove water. Sampling locations 1-3m from the discharge had TSS levels 30-50% lower than they

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200 Table 3-47 Soluble reactive phosphorus (SRP) in water of mangrove before and after discharge of treated wastewater Before dischar~e: Sample 12Dec 3 Jan 24 Jan 3Mar 30Mar 30 Apr Average location 1998 1998 1998 1998 1998 1998 standard Total Total Total SRP Total SRP Total SRP Total error of SRP SRP mg/1 mg/I mg/I SRP mean Mg / 1 mg/I mg/I Total SRP .... ..... ........ -~_g,1! -A 1 m 1.65 1.75 0.7 0.95 1.1 1.16 1.22 + 0 17 upstream B 1 m 1.55 1.05 1.35 1.05 0 88 1.4 1.21 + 0.11 downstream C,3 m 1.35 0 95 0 7 0 8 0 84 0 67 0 89 + 0 1 downstream D,6m 1.05 1.8 0.6 1.15 0 66 1.16 1.07 + 0 18 downstream E, 12 m SE 2.1 0 .85 0 95 0 6 0 65 0 54 0.95 + 0.24 After dischar~e : Sample 31 May 30 June 1 Aug 1998 19 Aug 1998 Average standard error location 1998 1998 Total SRP Total SRP of mean Total SRP Total SRP mg/1 mg/I TotalSRP mg/l __ mg/1 m 1 A, 1 m 3 54 4 1 3 69 3 63 3.74 0 12 upstream B 1 m 2 3 6 54 4 76 3.44 4 26 0 .91 downstream C ,3m 0 34 1.67 4 .03 3.44 2.37 0.84 downstream D ,6m 0.37 1.3 1.74 2.45 1.47 0.44 downstream E 12 m SE 0 56 0.44 1.03 2 17 1.05 39

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201 Table 3-48 Chemical oxygen demand (COD) in water of mangrove receiving wetland before and after discharge of treated wastewater Before discharge : Sample location 3 Mar 1998 30 Mar 1998 30 Apr 1998 Average standard error of COD COD COD mean mg/1 mg/1 mg/1 COD mg/I --------A 1 m upstream 54 70 69 64 B 1 m 48 65 144 86 downstream C 3 m 54 76 106 79 15 downstream D ,6m 129 129 203 154 25 downstream E, 12 m SE 189 202 93 161 34 After discharge : Sample location 31 May 1998 1 Aug 1998 19 Aug 1998 Average standard COD COD COD error of mean mg/1 mg/1 mg/1 COD mg/1 ---A 1 m 102 204 150 152 29 upstream B 1 m 112 203 129 148 28 downstream C ,3m 67 211 123 134 42 downstream D ,6m 55 199 76 110 45 downstream E, 12 m SE 82 203 133 139 35

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202 Table 3-49 Total suspended solids (TSS) in water of mangrove receiving wetland before and after discharge of treated wastewater Before discharge : Sample 3 Mar 1998 30 Mar 1998 30 Apr 1998 Average standard error of location TSS TSS TSS mean mg/1 mg/I mg/I TSS m A, 1 m 275 277 330 294 18 upstream B, 1 m 218 400 282 300 53 downstream C,3 m 139 378 424 314 88 downstream D ,6m 157 371 312 280 64 downstream E, 12 m SE 209 435 435 360 After dischaq~e : Sample 31 May 1998 30 Jun 1998 1 Aug 1998 19 Aug 1998 Average location TSS TSS TSS TSS standard error of mg/I mg/I mg/I mg/I mean TSS -....... ... -.. ----.... .. ------mg/I .. A, 1 m 74 112 328 145 195 58 upstream B, 1 m 55 151 176 173 167 downstream C,3m 73 194 162 208 188 12 downstream D,6m 49 248 198 228 225 13 downstream E, 12 m SE 52 104 164 326 198 57

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203 had been pre-discharge. This was also true for the more distant sampling points (6m downstream and 12 m SE ) and thus may reflect a general lowering in suspended solid content on the mangrove during this period of the year There is in any case no increase in suspended solids content of the waters as the locations closest to the discharge point are lower than other locations in the mangrove (Table 3-49 ) Coliform bacteria Coliform bacteria were measured in mangrove surface water before and after discharge (Table 3-50). In December 1997 and March 1998 coliform bacteria levels were 30 000 co l onies / 100 ml. After discharge began on 3 May 1998 coliform levels close to the outfall were influenced by coliform concentration in the discharge effluent. When 700 colonies / 100 ml were counted in discharge water on 15 May 1998 only location A 1 m upstream of the discharge showed elevated bacteria count ( 3500 colonies/100 ml) On 20 June 1998 when 8700 colonies / 100 ml were counted in discharge water and on 3 August 1998 when 87 000 colonies/100 ml were counted, elevated coliform levels were found in the monitoring locations 1-3 m from outfall but point D 6m downstream was at or below background levels ( Table 3-50 ) Salinity Salinity in the surface water of the mangrove measured December 21-22 1997 (Table 3-5 1 ) showed considerable variability ranging from 7 -15 parts per thousand (ppt). Over the course of a two day study a smaller range was found in individual monitoring pipes 1-2 5 ppt. At this time the pumped tapwater in Akumal was 4 5 ppt and salinity in the two wetland treatment systems varied from 3 to 4 5 ppt.

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204 Table 3-50 Coliform bacteria in water of mangroves in 1998 after discharge of treated effluent. Sample location or type 15May 20 June 3 August Mean Coliform Coliform Coliform Coliform MPN / 100 ml MPN/lO0ml MPN/ 100 ml MPN/ 100 ml ----;,,J,J .. Discharge 700 8700 83, 000 30 800 Effluent Station A 1 m upstream 3500 4000 5300 4267 Station B 1 m downstream 120 9000 46000 18373 Stn C 3 m downstream 0 3000 6800 3267 Stn D ., 6 m downstream 820 520 40 460 Stn E, 12 m S E 19400 510 3060 7657 measurements of mangrove water before discharge began : 1 December 1997 30 000 MPN/ 100 ml ; 20 March 1997 30 000 MPN / 100 ml.

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205 Table 3-51 Salinity in mangroves in 1997 before discharge of sewage eflluent. Location A 1 m upstream B 1 m downstream C 3 m downstream D 6 m downstream E 12 m SE 21 Dec 21 Dec 22 Dec 97 22 Dec 97 0900 hr 1530 hr 1000 hr ppt ppt ppt 13 13 14 7 8 9 5 9 9 5 10 9 9 10 13 14 14.5 1230 hr ppt 14 9.5 10 10 15

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206 Salinity was measured at these locations monthly from March 1998 through August 1998 (Table 3-52) After discharge began in early May 1998 salinity was around 2 ppt at locations A -D which were within 6 meters of the treated effluent. However on 31 May 1998 when salinity was low ( < 0 5 ppt at station E), eflluent with 2 ppt increased salinity (which averaged 1.8 ppt at stations A-C). These data suggest that salinity was mostly lowered by the discharge of treated eflluent. However in periods of very low salinity in the mangrove (e.g after heavy rains or during periods of high input of inland fresh groundwater) the treated eflluent may be expected to raise salinity in the discharge area. Simulation of Water in Treatment Units and Mangroves A computer simulation model was developed to increase understanding of factors affecting water inputs and outflows in the wetland treatment units and mangroves Figure 3-52 presents systems diagrams of water in the treatment wetland units and the water i n the mangrove receiving wetland with equations used in the simulation model. Figure 3-53 shows the systems diagram with calibration values for storages and for flows along pathways Table 3-53 gives the computer program for the simulation and Table 3-54 is the spreadsheet with calibration values for storages and flows used to calculate coefficients of the model. The treatment wetland units receives inputs of water from incident rainfall (J r ) that falls directly on the wetlands and sewage (J5). Transpiration (k2) is controlled by amount of water in the wetland (Q1 ) and its interaction with sunlight (S1), wetland biomass (B1 ) and the wind (w) Wetland biomass increase (k8 ) is autocatalytic driven by

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207 Table 3-52 Salinity in mangroves in 1998 Discharge of treated eflluent began May 1998 Location 3Mar 30Mar 30Apr 31 May 30 Jun 1 Aug 19Aug ppt ppt ppt ppt ppt ppt ppt A 1 m upstream 9 11 12 1.5 2 2 2 B 1 m downstream 7 9 10 5 2 2 1.5 2 C 3 m downstream 5 12 14 1.5 2 2 1.5 D 6 m downstream 5 5 8 10 < 0 5 4 2 2 E 12 m SE 5.5 12.5 13. 5 < 0.5 3 5 4 Table 3-53 Salinity in mangroves in 1997 before discharge of sewage effluent. Location 21 Dec 21 Dec 22Dec 97 22 Dec 97 0900 hr 1530 hr 1000 hr 1230 hr ppt ppt ppt ppt ---------... ---"-----~ ................ A, 1 m upstream 13 13 14 14 B 1 m downstream 7 8 9.5 9 5 C 3 m downstream 9 9.5 10 10 D, 6 m downstream 9 9 10 10 E 12 m SE 13 14 14.5 15

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Treatment Unit dQ1 =Jr+ JS -k1Q1kzB1Q1S1w dB1 = k9S1Q1B1 k11B1 S1 = S/(1 + k7wQ181) Treated Sewage s 2 = s1c1 + k 8wQzBz) dBz = k, oSzwQzBzk, zBz dQz = Jr + Jts+ Jg k4(Qz/ A -Td) k5SzwBzQz Figure 3 52 Systems diagram for simula tion mod e l o f water bud ge t s o f t reat m e nt unit a nd r ece i v in g w etla nd s howin g diffe r e n ce e qu at i o n s N 0 00

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0.335 Treated Sewage Receiving Mangroves ----u.p-~--~---' Figure 3-53 Systems diagram showing steady state storages and pathway flows for water budget simulation model of treatment unit~ and mangroves. N 0 '-0

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210 Table 3-53 Computer program in BASIC for simulation model of water budget in treatment wetland unit. water budget simulation model for treatment system 4CLS 5 SCREEN I, 0 6 COLOR 15, 1 10 LINE (0, 0)-( 400, 300), 15, B 15 LINE (0, 60)-(400, 60) 20 LINE (0, 120)-( 400, 120) 25 LINE (0, 180)-( 400, 180) 30 LINE (0, 240)-( 400, 240) 35 LINE (0, 300)-( 400, 300) 50 dT = 1 55 tO = 1 'make equal to yr# 60Td0=. 6 65 so =90 70 Q20= .1 75Ql0=.l 80 BlO = 2 85 B20 = .1 86 Jr{)= .01 87 JgO = .1 95 S = 3000 110 Id= .68 155 Jr= O! 180Bl = 2 185 B2 =9 190 Ql = .16 195Q2=1 196 A= 1 205 Dilvf w(l 2), Jg(l 2), Js(I 2) 223 FORI = I TO 12 224 READ w(I) 225 NEXTI 226 DATA 5,6 6,4 3,4.4,5 .6,5 4,4.5,3 6,4 ~1,4. 4,5.9,6.7 230FORI = 1 TO 12 232 RE.t\D J g(I) 234 NEXTI 236 DATA 0 254,0. 2,0 2,0 2,0 6,0.47,0.29,0.33,0.47,0.4 4,0 22,0 .21 238 FORI =ITO 12 240 READ Js(I) 242 NEXT I 244 Data 034,0 034,0.034,0 034,0 022,0 022,0 .02 2,0 022,0 022,0.034,0.034,0.034 275 K2 = . 0000016666# 282 k4 = 1.012625# 285 K5 = .000002# 290 K7 = 520833 292 K8 = 7375# 294K9=. 00000114# 295 klO = .000000675# 300 Kl 1 = .000457 305 Kl2 = .000169# 306 kl= .02902# 309 I= 1 320 PSET ((t + y 365) / 10 tO, 60 -S I SO), 2 325 PSET ((t + y 365) I 10 tO, 160 -Ql / QIO), 1 330 PSET ((t + y 365) / 10 tO, 120 Q2 / Q20), 2 335 PSET ((t + y 365) I 10 tO, 160 -Bl/ B10), 4 340 PSET ((t + y 365) / 10 tO, 180 B2 / B20), 3 350 PSET ((t + y 365) / 10 tO, 60 Jr / Jr{)), 2 360 PSET ((t + y 365) / 10 tO, 180 Jg(I) I JgO), 4 380 S = 3000 + 1500 SIN(t 0193 -90)' ANNUAL SINEW A VE SUNLIGHT 385 IF S < 0 THEN S = 0 390Sl =S/(l+K7*Ql *Bl *w(I)) 395 S2 =SI (1 + K8 Q2 B2 w(l)) 400 Jts = QI -.16 403 IF QI < .16 THEN x = 0 405 IF QI> 16 THEN x = 1 415dQl =Js(I)+Jr-Jts-(K2*Sl *Bl* Ql w(I)) 418dQ2=Jr+(x*kl *Ql)+Jg(I)-(k4* (Q2 / A Td)) -(KS S2 B2 w(I) Q2) 4 25 dB 1 = (K9 S 1 Q 1 B 1 w(I)) -(Kll Bl)

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Table 3-53 continued 4'.28 dB2 = (klO S2 Q2 B2 "'w(l)) (Kl2 B2) 430 ETI = (h2 SI "'Bl l(c w(I) Ql) 431 ET2 = (K5 S2 B2 "' w(I) "' Q2) 440 B 1 = B 1 + dB 1 dT 442 Ql = dQl dT + Ql 444 Q2 = dQ2 "' dT + Q2 446 B2 = dB2 l(c dT + B2 450 TJr = TJr + Jr* dT 454 TJs = TJs + Js(I) dT 456 TETl = TETl + ETl dT 458 TJts = TJts + Jts dT 460 TET2 = TET2 + ET2 dT 560 prob = RNTI 562 Jr= 0 570 IF t <= 30. 42 AND prob < .164 THEN Jr= .0156 580 IF (t > 30.42 AND t <= 60.84) AND prob< .131 TIIEN Jr= .0103 590 IF (t > 60.84 AND t <= 91.26) Ai."JD prob < .072 THEN Jr= .0192 600 IF (t > 91.26 AND t <= 121.68) AND prob < .059 TIIEN Jr= .0229 610 IF (t > 121.68 AND t <= 152. I) A"ND prob < .158 TIIEN Jr= .0348 620 IF (t > 152.1 AND t <= 182.52) AND prob< .26 THEN Jr= .0182 630 IF (t > 182.52 .AND t <= 212.94) AND prob < .224 TIIEN Jr= 0129 640 IF (t > 212 .94 AND t <= 243.46) AND prob < .256 THEN Jr= 0129 650 IF (t > 243.46 AND t <= 273. 78) AND prob < .322 THEN Jr = .0153 660 IF (t > 273.78 AND t <= 304.2) AND prob< .312 TIIEN Jr= .0148 670 IF (t > 304 2 A1'ID t <= 334.62) AND prob < .253 TIIEN Jr= _()..)97 680 IF (t > 334 .62 AND t <= 365) AND prob < .22 THEN Jr= .0085 690 IF (y > 5 AND y < 10) THEN Jr= Jr>!< .5 700 IF t <= 30.42 THEN I= 1 702 IF (t > 30.42 AND t <= 60.84) THEN I =2 704 IF (t > 60.84 AND t <= 91.26) THEN I =3 211 706 IF (t > 91.26 Al."JD t <= 121.68) THEN I =4 708 IF (t > 121.68 AND t <= 152.1) THEN I =5 710 IF (t > 152. l AND t <= 182.52) THEN I =6 712 IF (t > 182.52 AND t <= 212.94) THEN I=7 714 IF (t > 212.94 AND t <= 243. 46) THEN I=8 716 IF (t > 243.46 AND t <= 273.78) THEN I=9 718 IF (t > 273.78 AND t <= 304.2) TIIEN I = 10 720 IF (t > 30-4.2 AND t <= 334. 62) THEN I = 11 722 IF (t > 334.62 AND t <= 365) THEN I = 12 1000 t = t + dT 1010 IF t < 365 GOTO 320 1020 y = y + 1 1030 t = 1 1040 IF y <= 10 GOTO 320

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212 Table 3-54 Spreadsheet for calculation of coefficients in water bydget simulation model of treatment units and mangroves. Sources: Sunlight S= 3000 kcal/m2/day Calibration States: Unused sunlight, treatment wetland S 1 = 500 kcal/m2/day Unused sunlight, mangrove wetland S2= 50 kca l /m2/day Tide level Td= 0.68 m3/m2 Sewage input Js= 0 034 m/m2/day Rain Jr= 0 00302 m/m2/day Inland GW Jg= 0 3 m/m2/day Wind w= 5 m/sec Depth of water in treatment wetland 01= 0.16 m Depth of water in mangrove wetland 02= 1 m Biomass, treatment wetland 81= 12 kg/m2 Biomass mangrove wetland B2= 16 kg/m2 Flows per day: Calculations of coefficients Outflow from treatment wetland flow (qty) k1 (01 Othreshold) = transpirat i on in treatment wetland k2*B1 *01 *S 1 '\v = k1= 0 .008 k2= Exchange between mangrove surface water and groundwater k4*((O2/A) -Td) =((Jr+ Jts + Jg (k5*B2*S2*W'"O2)) k4= k4*((O2/A) -Td) = 0 32404 transpirat ion in mangrove wetland k5*B2*O2*S2'\v = 0 008 k5= Unused sunlight, treatment wetland k7*O1 *81 '\v = 500 Unused sunlight mangrove wetland k8*O2*82'\v = B i omass increase treatment wetland k9*S1 *Q1 *81 '\v = Biomass increase.mangrove wetland k1 0*S2*Q2*82'\v = Resp i ratory losses treatment wetland k11*81 = Resp i ratory losses mangrove wetland k12 B2 = .0027 500 k7= 50 k8= 5.48E-03 k9= 2 70E-03 k10= 5.48E-03 k11 = 2 70E-03 k12= 0 02902 1 67E-06 1 012625 0 000002 0 520833 0 7375 1 14E-06 6 75E-07 0 000457 0 000169

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213 sunlight wind water levels and the quantity of existing wetland biomass Respiratory losses (k ll) are a function of quantity of the biomass Water exits the system by two methods : from transpiration from the wetland plants and by outflow of treated wastewater (k1). Because of the density of plants evaporation and plant uptake are minimal and have been omitted from this aggregated model. Treated sewage ( k1) overflows out drainage pipe and leaves the wetland for the mangrove when the holding capacity of the treatment unit is exceeded (X in switch = 1 ). The water inputs to the mangroves are direct incident rainfall (Jr), treated wastewater outflow from the treatment wetland units CJts) and groundwater input ( Jg) and tidal inflow(~) when the water level of the mangrove (Q2 ) is lower than that of the tides (Td) Water outputs are from transpiration (ks ) by the mangrove vegetation and tidal exchange (~) when mangrove water level exceeds sea level. Mangrove biomass grows ( k10) by an autocatalytic process the energy drivers being sunlight (S2), wind ( w ), available fresh water ( Q2 ) and its own biomass state (B2). Mangrove biomass losses through plant respiration and animal consumption ( k12) are a function of the quantity of biomass The model was calibrated and its sources programmed with seasonally varying data from available literature on climatic factors (temperature humidity rainfall tida l range wind evapotranspiration, groundwater flow) in the Yucatan (Appendix B ) Groundwater discharge becomes more important in months with heavy rain and treated effluent decreases at the same time of year (the off-peak tourist summer season). In the dry season sewage inputs are greater and rainfall is decreased

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214 Simulation of the model under normal anticipated conditions (Figure 3-54 ) shows that treatment wetland biomass increases more rapidly than the mangrove biomass though the constructed wetland reaches equilibrium (when rate of primary productivity equals respiration) at a lower value than the mangroves Water levels remain fairly constant in the treatment wetlands since effluent discharge to mangroves occurs when the limestone is saturated however there is a small annual elevation due to peak tourist season loading. Sewage inputs are an order of magnitude greater than rainfall inputs Mangrove water levels reflect the influence of the large inland groundwater discharge during the summer / fall and inputs of treated sewage effiuent are of the same order of importance as groundwater from inland sources Simulation runs were conducted for extreme conditions (Appendix B) If sewage loading is increased ten-fold due to increased population use of the treatment system, there is rapid growth of wetland biomass and the mangroves show higher standing water levels ( Figure 3-55). If inland development has eliminated groundwater flow to the mangroves this results in lowering mangrove water levels and decreasing mangrove growth (Figure 3-56). Hurricane events bring high rain, wind and tidal levels resulting in loss of half of both treatment wetland and mangrove biomass Wetland vegetation recovery is more rapid than mangrove but that overall both ecosystems may take 5-10 years to fully restore biomass after a large hurricane (Figure 3-57) Notes on literature values used to estimate storage values and pathway flows in the water budget simulation model are given in Appendix B.

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lnsolation 5000 Kcal/m 2/day Water Inflows 1 m/day Water Levels 1.5 m Biomass 20 Kg/m 2 J\J\J\J\J\J\j\j\j\ / Ground Water Flow -----------...... --------....... ---Rainfall .: .:. = .; .:, .. ... ... .. . -.... .. -... ..._ ... .. -... -..,. ... -.. .._ In Treatment Unit Mangroves :rreatment Unit Years Figure 3-54 Computer simulation of the water budgets of treatment units and mangroves 11

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216 I'~ A l~L f\ A A/~/~\ 'J /\ I"/\ I~ 1 \ / \ v Sunlight 'L \ \_.._.) \ ...Jt' I ; , I \. { \ / ...J .......... '--" ......... ,........ ......__ .,, Rainfall :., -,... ... .. , .-..._, .,_ , -:s. r Mangrove bio. ~a~s ~---------Mangrove water level r ;,.___ ------"'I..J"L------._,_ ~.....,... -"'----"1...11&__ ...P-__ ~--.__. ... -~--___ .... Wetland biomass. _.,.~ Wetland water level Groundwater flow -------~-~--. =..:...~::=:,__:;,:::___:::::..::.'.:!~--=:..=-Simulation run 2 Time---'> ... Figure 3-55 S i mulation of water budget for wetland treatment unit and m angroves with increase of wastewater loading (10 times higher) Scale: sunlight 5000 Kcal/m2/ day biomass 20 kg/m2 water levels 1.5 m water inflows Im/day

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217 0 0 A~~\ A 0 / \ / \ \ /Sunlight \., J./ \ / ~J '\.J .,J .-4. l \_,_/ V \ ..... / _._. "-.aJ \ Rainfall -.. r -:- -... , .-... -, e . - __, .,, r r -Mangrove biorl_}_ ass ____ .--.w ___ Mangrove water level Wetland biomass ___,..,.------Wetland water level Groundwater flow Simulation run 3 Time-->-Figure 3-56 Simulation of water budget for wetland treatment unit and mangroves with loss of groundwater inflow. Scale: sunlight 5000 Kcal/m2/ da y, biomass 20 kg/m2, water levels 1.5 m, water inflows lm/day

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218 -, -:r ;n -:"\ed""'\, I -,._ a 'Iii I I .-,., !5-, ,... I ---Figure 3-57 Simulation of water budget for wetland treatment unit and mangroves with hurricane event at year 5. Scale: sunlight 5000 Kcal/m2/ day biomass 20 kg/m2 water levels 1.5 m water inflows Im/day.

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219 Regional Potential of Wastewater Treatment System Definition of Coastal System For purposes of estimating the regional role of the new wastewater treatment systems, a square kilometer area around Akumal was defined (Figure 3-58). Data collected from the homeowner s association in Akumal combined with interviews permitted an assessment of the environmental flows and support systems for this area. Judging from the pattern of current development, this area may contain 15 private houses and four hotels / condominium complexes with a total resident population of225-250 (permanent residents plus tourists) Emergy Evaluation For this scenario inputs to this area are diagrammed in Figure 3-59 and evaluated in Table 3-55. With the use oftransformities from Table 2-1 emergy and emdollars were calculated in the last two columns. The largest renewable source emergy flows are those of inland groundwater and hurricanes. Tourism revenues (income) are the largest imported emergy flow, followed by imported goods, petroleum products and building materials (limestone sand, concrete) Local services are about 25% of tourist revenues (Table 3-55). In aggregate natural emergy from renewable natural resources is about 39% of total emergy flows Inflows are grouped in categories in Figure 3-60 and used to calculate the indices shown in Table 3-56 Empower density is 1.2 E16 sej /ha/yr. Service emergy compared to free energy is 0.32. Imported emergy flows are somewhat greater than local ones as the nonrenewable / renewable resource ratio is 1.22. The investment ratio of 1.49 is far lower than the United States where it averages 7 (Odum, 1996) The sej I money flow ratio is

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-6 C anbbean S ea / / ---------7---------------------8--------------0 100 200meters Scale Contour Interval =I meter Figure 3-58 Map of Akumal, Mexico showing the one square kilometer coastal study area N N 0

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221 Table 3-55 Emergy evaluation table of I-square-kilometer of developed coastline, Akumal, Mexico (see Figure 3-58) Note Item Raw Units Transformity Solar EmDollars (sej/unit) emergy ... -. ~n.., E:}8 __ s~L .... RENEW ABLE RESOURCES : 1 Sunlight 4 54 E13 J 1 < 0 .001 < 0 .001 2 Rain 5 5 El2 1.544 E4 0 09 62 0 3 Rain transpired 4.46 El2 J 1.544 E4 0 07 51.1 4 Rain, geopotential 2 .65 El 1 8 88 E3 < 0 .001 < 0.001 5 Wind, kinetic 2 .7E9 6 .63 E2 < 0 .001 < 0 .001 6 Hurricanes 1.14 E13 9 579 E4 1.09 796 7 Waves 7 88 E6 2.59E4 < 0 .001 < 0 .001 8 Tide 7.53 ES 2 36 E4 < 0 .001 < 0 .001 9 Earth cycle 1 El2 2 .9E4 0 .03 21.2 10 Inland water flow 7.41 E13 4 .8E4 3 54 2 584 11 Pumped groundwater 4 .28 Ell 4 .8E4 0 02 15. 0 Subtotal (items 2 + 6 + 9 + 10) 4 77 3 482 NON-RENEW ABLE RESOURCES 12 Loss of soil due to development 4 24 Ell 7 .37E4 0 .031 22 6 13 Loss of vegetation due to development 4 .7Ell 2E5 0 094 68. 6 Subtotal (items 12+ 13) 0 .13 95 LOCAL SER VICES 14 Local labor and services 7 68 E5$ 1.88 E12 1.44 1 146 +of item 22 0.13 Subtotal 1.57 IMPORTED GOODS AND SERVICES 15 Forest products 5 09 El2 3.49 E4 0 2 146 16 Limestone gravel sand 1.53 El 1 8 .98 E6 1.4 1 022 17 Food 8 6 Ell 8.5 E4 007 51 18 Gas 6 96 E4 4 .8E4 < 0 .001 < 0 .001 19 Petroleum products 1.84 El3 6 .6E4 1.21 880 20 Electricity 2 37 El2 1.74 ES 0.4 292 21 Imported Goods 7 02 E5$ 1.88 E12 1.32 885.4 22 Capital investments 1 375 E5$ 1.88 E12 0 .25 183. 5 23 Tourism 4 9 E5$ 1.88 El2 0 92 2 476 7 Subtotal (items 15-23) 5 .71 4 ,168 Total 12.05 8 ,891 Column 6 (EmDollars) based on 1.37El2 sej/ $ U.S dollar / emergy ratio for 1996

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222 Table 3-55 continued 1 SUN Solar exposure of2381 hours/year (Viguera et al 1994) area = 1E6 m2 avg insolation : 1.55 E2 kcaVcm2/yr (Brown et al, 1992) [taken as equal to that ofNayarit, Mexico] albedo= 3 Energy = area avg insolation ( 1 albedo) = 1E6 m2 1.5 5E2 kcaVcrn2 E4 cm2/m2 7 4186 I/kcal =4.54E13 J 2 RAIN, TOTAL Average rainfall at Puerto Moreles is 1123 mm ((Ibarra and Davalos 1991) for Puerto Moreles Q R and at Tulum is 1104 mm (Viguera et al, 1994). Therefore a value of 1114 mm was used transformity = 15,444 sej/J (Odum, 1996 p 186) land area = 1E6 m2 rainfall = 1.114 m Rain, total = area* rainfall* Gibbs#= (IE6 m2) (1.114 m) 1000 kg/m3 4 94E3 J/kg = 5 SE12 3 RAIN, TRANSPIRED land area = 1E8 m2 rainf aU = 1.114 m ET= 0.9 (Viguera et al, 1994) given as% of rainfall = .81 Rain transpired = area ET rainfall Gibbs # = IE6m2 1.114m 81 1000 kg/m3 4 94E3 J/kg transformity (Odum, 1996 p 186) : 15 444 / J 4 RAIN, GEOPOTENTIAL Transformity = 8 888E3 (Odum, 1996 p 186) Energy = area runoff* rainfall average elevation gravity = IE6 m2 [(1-ET)= 81]* 1.114 m 1000 kg/m3* 3 m 9 8 mis = 2 65 E11 5 WIND Average wind velocity of 5 0 mis (Ibarra and Davalos 1991) for Puerto Moreles Q R Wind transformity = 663 sej / J (Odum, 1996 p 186) Diffusion coefficient taken as similar to Tampa, Fl = 2 2 m3/mlsec (Odum, 1996 p .295) Vertical gradient taken as similar to Tampa, Fl = 1.9E-3 mlsec/m Kinetic energy of wind = (height) (density) (diffusion coefficient) (wind gradient) (area) energy at 1000 m = (1000 m) (1. 23 kg/m3) (2 2 m3 / mlsec) (5m/s/m) (1E6m2) energy= 1.35El2 J energy available at ground level = 20%, (H.T. Odum, pers comm ) = 2 1.3SE10 J = 2 .7E9 J 6 HURRICANES Transformity = 9 579E4 sej / J (Scatena et al, in press) Method following that of Scatena et al.: average hurricane has kinetic energy of wind of 1.3E18 j/day (Riehl 1979) assume has overall diameter of 500 km but hurricane winds in two 50 km zones around center = 4.46El2 and strip l km wide passes over Akumal location ; assume 100/4 of wind energy does work at surface assume area on average has major hurricane event every 50 years

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223 Table 3-55 continued hurricane wind energy = (0 10)*(1.3 E18 J / day)* (0 25 days)* (1 km* (50 + 50 km)) / [(3. 14*250*250 km)* (50 yr) = 1.14 El3 J / yr 7WAVES Average wave height is given as 0 8 m for the coast at Puerto Moreles (Ibarra and Davalos 1991) Energy of waves absorbed at shore = shore length*l/8*density*gravity*height squared* velocity (Odum, 1996 p 298) velocity is : square root of gravity* depth at gauge (taken as 3 m for Akumal coastline)= 9.8m/sec2 m ".5= 5.4m/sec energy= 1000 m 1/8 l.025E3 kg/m3*9 8m/sec2 64 5.4m/sec = 4 34E6 Transformity for wave energy = 25 889 sej/J (Odum, 1996) 8TIDE average tidal height of 18. 1 cm (Ibarra and Davalos 1991) for Puerto Moreles Q R transformity for tidal energy = 23, 564 sej/J (Odum, 1996 p 186) Energy= shelf area* (0 5) *tides/yr* (height squared)* (density)* gravity (Odum, 1996 p 298) =5E4m2 0 5 730 3E-2m2 1025 kg/m3 9 8 m/sec2 = 7 .53 ES 9 EARTH CYCLE Transformity = 29 000 sej/J (Odum, 1996 p 186) Energy= (land area) (heat flow per area) heat flows for old stable areas is 1E6 j/m2/yr (Odum 1996 p 296) Energy= 1E6 m2 1E6 j/ m2 = 1E12 10 INLAND GROUNDWATER FLOW following methodology ofBack, 1985 : average rainfall= 1 05 m .9 m evapotranspiration = .15 m mean annual recharge to groundwater area including inland drainage basin = 65 500 km2; total recharge = 9 800E6 m3 per yr groundwater consumption (Lesser 1976) is 350 m3/ yr Assuming this water is lost total discharge along the approximately 1,100 km of coastline= 9450E6 m3/ l 100 km= 8 6E6 m3/yr for each km of coastline the amount of groundwater underlying the coastal area can be estimated as around 3 m (Back, 1985) thus total groundwater in the study area is about 50% of this depth, or 1.5 m 10E6 m2 = 1.5E7m3 l.5E7 1000 kg/m3 4 94E3 J/kg = 7.41El3 11 PUMPED GROUNDWATER calculated at 100 gallons/person/day Energy: 225 people *lO0gaVday lm3/260 gallons* 365 days* 1000 kg/m3 4 94E3 J/kg Energy= 4 .28El1 Transformity = 4 8E4 (Odum, 1996 p 120) 12. LOSS OF SOIL (due to development) estimate loss of20m2 of mangrove wetland per hotel* 4 = 80 m2 and 5 rn2 per house* 15 = 60m2 total 140 m2; depth oforganic soil@ 0 .3m 06 g/cm3 (bulk density mangrove soil from this study) soil lost= 140 m2 0 3m 1 E6cm3/m3 06g/cm3 = 2 52 E6 gin mangrove loss of soil ofbeach/sand dune ecosystems : 4 E3 rn2 x 0 15m = 6 E2m3 1.0 g/cm3 (bulk density) soil lost= 6 2 E2m2 1 E6 cm3/m3 1.0 g/cm3 = 6.2 E8g Energy= (2 52 E6g)*(0 76organic)*(5 4Kcal/g)*(4186J/Kcal) + (6 2 E8g)*(0.03organic)*(5.4Kcal/g)*(4186J/Kcal) = 4 .33 E9 J + 4 .2El 1 =4 24 El IJ Transformity = 7 37 E4 sej/J (Brown et al 1992)

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224 Table 3-55 continued 13. LOSS OF VEGETATION ( due to development) average biomass for mangrove = 15 kg/m2 (Mitsch and Gosselink 1993) ; sand dune est at 0 5 = 7.5 kg/m2 lost vegetation : 140m2 15 kg + 4 E3m2 7 5 kg = 3 .21 E4 kg Energy = 3 .21 E4kg 1 E 3 g/kg 3 5 Kca V g 4186J/Kcal = 4 7 El 1 J Transformity = 2E5 (Brown et al, 1992 for agricultural + forest products) 14 LOCAL SERVICES estimated from revenues oflocal labor and businesses (e g diving shops travel agency etc ) 125 local workers @ $35 week 52 weeks = $227 500 15 higher paid labor (di v e instructors drivers etc ) @ $3, 000 / month 12 = $540 000 Total $7 68E5 Mexican national sej / $ = 1.88 El2 (Trujillo 1998) 15 WOOD wood products harvested locally for construction, repairs + palm frond for roofing estimated at 500 m3/ yr Energy = 500m3 lE6cm3 /m3 10176J /cm3 = 5 .09El2 transformity = 3.49E4 (Brown et al, 1992) 16LIMESTONE GRAVEL SAND limestone( + local sand and gravel) : used in construction and repair from survey data : 120 m3/ yr sand ; 120 m3 gravel ; 60 m3 limestone rock Transformity of limestone gra vel and rock = 1.62E6 sej/ J from Odum (1996 p 310) Weight of limestone from Limestone Products Newberry FL (pers. comm ) : 3000 lbs/m3 Energy (gravel) = 120 m3 3000 lbs/m3 454 g/lb *611 J/g = 9 99EIO limestone rock, 5-10 cm. rock, from Limestone Products Newberry FL (pers comm.) : 2700 lbs/m3 Energy (rock)= 60 rn3 2700 Ibs/m3 454 g/lb 61 lJ/g = 4.49E10 est. wt of sand from Florida Rock Mines Grandin, FL plant (pers comm ) : 3100 lbs/m3 transformity of sand using Odum (1996 p 310) for sandstone : 2E7 sej/ J Energy (sand) = 120rn3 3100 lbs/m3 454 g/lb 50J/g = 8 44E9 total energy (gravel rock and sand) = l.53El 1 Composite transformity calculated by combining those for grave~ rock and sand in proportions of materials used 17FOOD Based on 2500 Kcal/person/day (10.47E6 J / day) and population on average of225 Transformity : 8 5E4 (Brown et al, 1992) Energy = 225 365 10.47E6J = 8 .60Ell 18 GAS Hotel usage = 30 200 litters butane gas (survey data) 6 = 181, 200 I butane/yr transformity = (Odum, 1 996 p 187) Energy = l.81E5 litters 1 ft3/ 28 3 litters 1031 BTU /ft3 1055 J/BTU = 6 96E4 J 19 FUEL (Petroleum products) Fuel usage by hotels (from survey data) : 8500 litters gasoline/yr + 650 litters diesel ifwe combine gasoline+diesel we can estimate that owner use of oil products is 9000 I *6 = 54 000 I

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225 Table 3-55 continued and adding 10 I/day *365 150 tourists = 547 500 litters/yr ; total = 601 500 litters= 150 400 gal= 54 000 gallons= 3008 barrels Oil products energy = 3008 barrels 5 8E6 BTU/barrel 1055 J/BTU = l.84El3 Transformity of petroleum products= 66, 000 sej/J (Odum, 1996 p 186) 20 ELECTRICITY Transformity for electricity taken as mean global value = 173,681 sej/J (Odum, 1996 p 305) Electrical usage: avg for hotels : 144 000 kWh/yr 4 = 576 000 (from survey data) avg for homes : 5500 kWh/yr 15 = 82 500 (from survey data) Energy= (658,500 kWh) (3. 606E6 j/kWh) = 2 37E12 J 21 IMPORTED GOODS estimated as tourist revenues local services 25% profit on investment = 1.96 E6$ -7 68 ES$ -4 9 ES$= 7 02 ES$ Mexican national sej/$ = 1.88 E12 (Trujillo 1998) 22 CAPITAL INVESTMENT capital investment : figured as $50 000 per house x 15 = $750 000 and $500,000 per hotel x4 = $2 000 000 Total $2 750 000 divided by lifetime of20 years= $137 500 Mexican national sej/$ = 1.88 El2 (Trujillo, 1998) 23 TOURISM (Income) from survey data, $490,000/yr per hotel 4 = $1, 960 000 To avoid double counting in table : tourist revenues service-imported goods : 1 96 E6 7 02E5 7 68E5 = 4 9 ES$ Mexican national sej/$ = 1.88 E12 (Trujillo 1998)

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Akumal coastal zone Quintana Roo Mexico 226 Emergy flows E18 sej/yr Figure 3-59 ; Systems diagram of the square kilometer coastal economy and environment, labelled with emergy flows from Table 3-57.

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227 Table 3-56 Emergy indices for evaluating one square kilometer of developed coastline Akumal Mexico Name of Index Definition ----------------Nomenewable / renewable F + N / R Service / free S / N + R Empower density Emergy / area / time Emergy/$ ratio Emergy / money flow Investment ratio (F + S) / (R + N) R = 4 77 El8 sej / yr (Table 3-57 subtotal after line 11) N = 0 .13 El8 sej/yr (Table 3-57 subtotal after line 13) One km of developed coastline Akumal,Mexico 1.22 0 32 1.2 E 16 sej /ha/ yr 5 7 El2 sej/$ 1.49 S = 1.57 E18 sej /yr (Table 3-57 lines 14 + 1/2 ofline 22) F = 5.71 E18 sej / yr (Table 3-57 lines 15-23 1/2 ofline 22) Empower density = 12.05 E18 sej/yr / 100 ha = 1.2 E16 sej/ha/yr

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228 0 _;;:r $ ,---,------I........L.~/$2.1E6 (U.S.)/yr 4.77 Akumal coastline 1 km2 R = renewable resources N = non-renewable resources F = imported resourcs S = services ___ ,... Flow of$ Annual flows in E18 sej/yr Figure 3-60 Diagram of emergy and money flows in the 1-square-kilometer coastal area Akumal, Mexico. Units of diagram are expressed in El8 sej (solar ernergy joules) / yr.

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229 5.7 El2 sej / $ four times greater than the U.S. and three times that of the national Mexican average (Trujillo 1998) showing the dominance of environmental emergy flow vs. monetary flow in the region Economic Evaluation The application of wetland treatment systems to the developed square kilometer will require the construction of wetlands to treat the hotels and houses. Construction costs vary depending on size of the wetland with individual house systems being smaller and therefore more expensive than the research wetlands and the hotel systems being larger and costing less The two wetlands in our study averaged $165 / person to construct. If we estimate the individual house systems as $250 / person and hotels at $150 / person, the costs for 15 houses of 6 people each = $22 500 plus 4 hotels with 160 people = $24 000 for a total capital expenditure of $46,500. If lift pumps are required on half the systems ( either because slopes do not permit gravity flow or to get treated effluent to the receiving wetland) costs will be increased by around $3,000 Averaged over 20-year lifetime (and 5 years for pumps), this equals $2,925/yr. Maintenance costs are estimated at $100 per house system, $500 per hotel system, for a total of $3500 /yr. Total yearly expenditures are thus $6,425 for the wetland treatment units to serve the developed square kilometer Package plants would cost $15, 600 for each of the hotels and if the houses send their sewage to a common collection point the equivalent of2.25 additional package plants will be required. Additional pumping/piping to centralize the house sewage will add an additional $10, 000 The overall capital cost will be $107 500 and with an

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230 average lifetime of 7.5 years (averaging machinery and other components) is $14 330 / yr Maintenance costs at $1100 / system will be $6,875, so total costs are $21,205 / yr Given a yearly money flow of about $1,950,000 for the developed kilometer in Akumal, capital and operating/maintenance (0/M) costs of the wetland treatment systems equals 0.3% of this economic activity, and capital and 0/M costs of the package plants would account for 1 1 % of overall monetary flows. Electricity required for the package plants are estimated at 250 Kilowatt-hours (kWh) / month/system or 18,750 kWh/year for the 6.25 package plants in the coastal area. This is 2 8% of the total electrical usage of the developed kilometer Should half the wetland treatment systems require use of a submersible lift-pump, electrical usage will be around 35 kWh/month or 420 kWh/yr, so 10 pumps will use 4 200 kWh or 0.6% of total electrical usage of the developed square kilometer. Water Budget Water budgets for a square kilometer of coastline were prepared for the square kilometer development scenario with no sewage treatment and the changes to the water budget assuming that all human wastewater is treated by the installation of wetland systems (Table 3-57 Figure 3-61) These regional water budgets show that the largest water inputs are from tidal exchange (36 5E6 m3 / yr) and secondly from inland groundwater (8 6E6 m3 / yr). These quantities of water far exceed that of pumped groundwater used by the area's population (1.7E4 m3 / yr). However pumped groundwater is far larger than the quantity of water deriving from precipitation that directly falls on the square kilometer (1.05E3 m3 / yr)

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231 Table 3-57 Water budget of a square kilometer of coastline around research site without use of wetland treatment systems. Changes with use of wetland treatment units are shown in parentheses Item Water in : 1 Direct precipitation 2 Pumped groundwater used by people 3 Inland groundwater flow 4 Tidal inputs Total water in Water out: 5 ET 6 Subsurface groundwater discharge to sea (includes tidal return + discharge of input precipitation, domestic sewage + inland groundwater) Total water out Notes: 1 Precipitation Quantity of water m / yr E5 m3/ yr 0 .01 0 17 86 365 451.2 8.59 ( + 0.02) 442 6 (-0 02) 451.2 Based on average precipitation of 1050 mm for Yucatan (Lesser, 1976). 1.05 1000 m2 = 1050 m3 2 Pumped groundwater use based on estimated population of 250 people x 50 gallons / person/day 250 50 gallons* 365 = 4 56E6 gal/yr m3/ 264 gal = 17,280 m3 3 Inland groundwater flow based on estimate (Back, 1985) on average discharge of groundwater per km of coastline in northeastern Yucatan

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Table 3-57 continued 4 Tidal exchange 232 -estimated on basis that 1 m of saltwater underlies and mixes with freshwater : 1000m 1000m 1 m = IE6m3 and that turnover is every 10 days 365 /10 = 36 5 /yr 1E6m3 = 36.5E6m3/ yr 5 Evapotranspiration sum of a. estimates by Lesser (1976) that 9 m on average of 1.05 of precipitation was evapotranspired in the Yucatan .9m 1000m2 = 900 m3 b plus 690 m3 from ET of water used for watering gardens etc. (based on estimates that average per capita production of wastewater is 30 gal/person/day in the Yucatan 20 gal / person/day is the difference between water consumption and wastewater production rates usually largely accounted for by watering of gardens etc. assume that this water has same characteristics as GW pumped 20 gal / person/day 250 people 365 m3 / 264 gal = 6,910 m3 further assume that 10% of this water is lost to ET before infiltrating therefore ET is increased by 690 m3 ) c plus water evapotranspired by mangrove wetlands of area based on water budget for southern Florida mangrove swamp (Twilley 1982) = 108 cm/yr, so if mangrove + other natural wetland vegetation covers 50 ha (half) of area = 50*10,000 m2 1.08m = 5.4E5 m3 Total ET= 9 E2 + 6.9 E2 + 8.57 ES = 8.59 ES m3 Impact of wetland based on wastewater discharge of 30 gal/person/day estimate. 30 gal/per person/day* 250 people* 365 day /yr* m3/264 gal = 10,370 m3 However with use of wetlands estimated ET losses of wastewater are 20% (from research for this study) therefore ET is increased by 2 070 or 0 02E5 m3 6 Subsurface discharge is based then on difference between inputs and ET since there is no surface water discharge

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233 Precipitation 86 Inland groundwater 0 17 Pumped groundwater Evapotranspiration 0.01 8.59 (+0.02 = 8 61) One square kilometer developed coastline Akumal, Mexico water flows ES m3/yr Tidal input 365 ES 442.6 ES Subsurface discharge (-0.02 = 442 .58) to the sea Figure 3-61 Diagram of water budget of one square kilometer of developed coastline Akumal, Mexico Figures in parentheses show changes in budget if all sewage is treated by constructed limestone wetlands

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234 The regional water budget with installation of wetlands for treatment of all wastewater shows a higher percentage of water going to E T as occurs currently as the ET is greatly increased by the estimated 20% evapotranspiration of sewage influent to the wetlands (Table 3-57) . Nutrient Budget Table 3-58 shows the quantities of nitrogen phosphorus organic compounds (BOD) and coliform bacteria added to the groundwater of the square kilometer if development occurs without sewage treatment and if wetland systems are used. Use of the wetland treatment systems for the 250 people living in the square kilometer area results in reductions of 76% for N added to the groundwater 85% less P being added, 88% less BOD ( organic compounds) and 99 97% less fecal coliform bacteria being added ( Table 3-58). These reductions amount to 75 kg less P 425 kg less N and 1430 kg less BOD in the groundwater on an annual basis When the further uptake and retention in the receiving mangrove wetlands are included discharge ofN, P BOD and coliform are further reduced It is more difficult to estimate what levels of nutrients and coliform bacteria will be discharged to the sea from our study area. Some nutrients are undoubtedly utilized b y soil bacteria and vegetation in the coastal wetlands and beach zone and some nitrogen are volatilized due to oxidative / reductive biochemical reactions in wetland zones Some phosphorus may be absorbed in limestone in the subsurface zone Coliform bacteria have an extinction rate in inhospitable environments apart from other processes such as plant and bacterial antibiotics which lower their number. The budgets for phosphorus

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235 Table 3-58 Comparative additions to groundwater (GW) of nitrogen, phosphorus BOD ( organic compounds) and fecal coliform from domestic sewage in a I-square-kilometer area of study site with and without the use of wetland treatment systems. Item Addition to GW Addition to GW Reduction in kg Percent without use of with use of ( or number of reduction by wetlands wetlands bacteria) use of wetlands + mangroves ---~~ -.... Nitrogen 466.7 41.5 425.2 kg 91% Phosphorus 83 kg 8.3 kg 74 7 kg 90% BOD 1504 kg 75 kg 1429 kg 95% Fecal 1.04 El4 0 001 E14 1.039 E14 99.99+% coliform bacteria bacteria bacteria Notes: wastewater infiltration based on 30 gal/person/day estimate. 30 gal/per pers./day 250 people* 365 day/yr* m3/264 gal= 10,370 m3 With use of wetlands estimated ET losses of wastewater are 200/o (from research for this study) therefore ET is increased by 2 070 m3 and wastewater infiltration is 8 300 m3 N based on average input levels of 45 mg/I and discharge levels of 10 mg/I in wetland system effluent (from this research study) 45 mg/I* 10001/m3 10 370 m3 kg/E6 mg= 466 7 kg IO mg/I 1000 l/m3 8 300 m3 kg/E6 mg = 83 kg 50% reduction in mangroves = 41. 5 kg P based on average input levels of8 mg/land discharge of 1.6 mg/l in wetland system effluent (from this research study) 8 mg/1 * 1000 1/m3 10,370 m3 kg/E6 mg= 83 kg 80% reduction in wetlands + 50% in mangroves= discharge of8. 3 kg P (reduction of74.7 kg P) BOD based on average input of 145 mg BOD/kg and discharge of 18 mg/l in wetland system effiuent (from this research study) 145 mg/I* 1000 l/m3 10 370 m3 kg/E6 mg= 1504 kg BOD 18 mg/I* 1000 l/m3 8 300 m3 kg/1000 mg= 149 kg+ 50% reduction in mangroves= 75 kg Coliform numbers based on influent of IE6 per 100 ml (IE7 per liter) and discharge of2000 per 100 ml (2E4 per liter) in wetland system effiuent (from this research study) 1E7/liter 1000 l/m3 10 370 m3= 1.04 E14 coliform 2E4/liter 10001/m3 8 300 m3 = 1.66Ell coliform (0 .001 E14)

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236 nitrogen, organic materials (BOD) and coliform inputs, are shown in Tables 3-59 3-60 3-61 and 3-62 and are diagrammed in Figures 3-62 3-63, 3-64 and 3-65. These regional budgets indicate that for a population of 250 people along 1 square kilometer of developed Yucatan coastlines, the use of the wetland treatment units will reduce yearly discharge to the sea of around 680 kg of organic matter (BOD) 190 kg of nitrogen, 50 kg of phosphorus and reduce total coliform discharge by over 1E13 coliform bacteria.

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237 Table 3-59 Phosphorus budget of a developed square kilometer of coastline Akumal Mexico with no sewage treatment and changes if wetland systems are installed. Item Quantity of water m3/ yr InQuts to system : In water : 1 precipitation l.05E3 2 pumpedGW 1.728 E4 used by people 3 Inland groundwater flow 8 6E6 4 Tidal exchange 36 5E6 In solids : 5 Food ----------Total in 45.123 E6 Inside system : 6 Addition to groundwater 1.037 E4 from domestic sewage 7 Increase in storage : limestone + vegetative/bacteria biomass Oumuts from system: 8 ET 8 59 E5 9 Subsurface groundwater 44 26441 E6 discharge to sea Notes: (see also notes to Table 3-50 and 3-52 ) 2 Quantity of P kgP/ yr neg 0 5 258 3.7 83.0 345 2 83. 0 86.3 Negligible 258 9 Change if wetland treatment systems used k p / 8.3 ( difference is 7 4 7) 140.3 (difference is + 54) Negligible. 204 9 ( difference = -54 ) based on estimated population of 250 people x 50 gallons/person/day 250 50 gallons* 365 = 4 56 E6 gal/yr m3/264 gal = 17, 280 m3 P content based on average of 15 groundwater samples collected by C. Shaw and M Nelson 12 Jan 97 and analyzed at the labs of the Soils Dept. Univ of Florida, which

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Table 3-59 continued had avg P of 0 03 mg/I. 238 P = 0 03 mg/I* 1000 l / m3 1.728 E4 m3 kg/1 E6 mg= 0.52 kg P 3 based on estimate (Back, 1985) on average discharge of groundwater per km of coastline in northeastern Yucatan P = 0 03 mg/I 1000 l / m3 8 6 E6m3 kg/1 E6 mg= 258 kg P 4 tidal exchange -estimated on basis that 1 m of saltwater underlies and mixes with freshwater : 1 000m 1 000m 1 m = 1E6m3 and that turnover is every 10 days 365 / 10 = 36 5 /yr 1 E 6m3 = 36.5 E 6m3 / yr P concentration in seawater (Drever 1988 ) averages 0 00 1 mg/kg total P = 36.5E6m3 0 001 mg/kg* kg/1E6mg 1.025E3kg/m3 = 3 7 kg 5 food P matches approx discharged Pin sewage (see note 6) 6 wastewater infiltration based on 30 ga l/ person/day estimate. 30 gal/per pers ./ day 250 people 365 day /yr m3 / 264 gal = 10 370 m3 P based on average levels of 8 mg/ I in septic tank effluent (from this research study) 8 mg/1 1000 l/ m3 10 370 m3 kg/E6 mg= 83 kg addition to groundwater = 75% x 83 = 62 3 (w/ o wetland sewage treatment ) Reduction in wetland treatment systems : 80% in wetlands (from this study) + 50% in mangrove (est.) 83 2 = 16 6 .5 = 8 3 kg Padded to groundwater with sewage treatment (a reduction of74. 3 kg) 7 if no sewage treatment estimate storage in limestone + vegetative/bacterial biomass = 25% of Pin groundwater from sewage additions and natural inputs ) 345.2 0 25 = 86 3 wetland + mangrove sewage treatment removes 7 4 7 kg P of wastewater P and natural removal is 25% of262. 2 kg P ( other inputs of P) = 65 55 ; total storage = 56 1 + 65.55 = 140 3 kg P 9 if assume in scenario of development without sewage treatment that uptake of P by limestone and bacteri a/ vegetation is 25%, Pis reduced from (6.222 E4 + 5 24 E 2 = 6.274 E4) / 4 = 4 71 E4 in scenario of wetland treatment systems P is further reduced by mangrove receiving wetlands ( data forthcoming from ongoing research) If reduction is 90%, then P reduces from (9 .13 E3 + 5 24 E 2 = 9.654 E3) (0 1) = 9.65 E2

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239 a/ Phosphorus budget without sewage treatment Food 83 Tide+ Inland groundwater + pumped water 262.2 One square kilometer developed coastline Akumal Mexico Phosphorus flow kg/yr 83 b/ Phosphorus budget with constructed limestone wetland treatment systems + receiving wetlands Food --Tide+ inland GW + pumped water 83 One square kilometer developed coastline Akumal, Mexico groundwater from sewage 8 3 (-7 4 7) Phosphorus flow kg/yr Subsurface discharge to sea 258 9 Subsurface discharge to sea 204.9 (-54) Figure 3-62 Diagram of phosphorus budget of one square kilometer of developed coastline, Akumal, Mexico Figures in parentheses show changes in budget if all sewage is treated by constructed limestone wetlands and receiving wetlands

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240 Table 3-60 Nitrogen budget of a developed square kilometer of coastline Akumal Mexico with no sewage treatment and changes if wetland systems are installed. Item Inputs to system : In water: 1 Precipitation 2 PumpedGW Used by people Quantity of waterm3/ yr 1.05 E3 1.728 E4 Quantity ofN kgN/ yr 786 19. 5 3 Inland groundwater flow 8 6 E6 9720 4 Tidalexchange Subtotal ( water inputs) 5 In solids : Food Total In Inside system : 36 5 E6 45 .123 E6 6 Addition to groundwater 1.037 E4 from domestic sewage 7 Increase in storage within system Outputs from system : 18.7 10,526 467 10, 993 467 2748 8 ET 8 5859 E5 Neg 9 Subsurface groundwater 44.26441 E6 5,492 discharge to sea Notes: (see also notes to Table 3-65 and Table 3-67) Change if wetland treatment systems used __ Jcg N / yr ... 41.5 (difference = -425 5) 3045 (difference = + 297) Neg 5,305 ( difference = 187) 1 Based on averafe precipitation of 1050 mm for Yucatan (Lesser 1976) 1.05 1000 m = 1050 m3

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241 Table 3-60 continued N-content of precipitation based on Valiela and Teal (1979) in their N budget for a Cape Cod salt marsh concluded rainfall contributed 0 786 gN/ m2/yr or 7 86 kg N/ha/yr. There are 100 hectares in 1 k:m2 hence : 7 86 kg* 100 = 786 kg 2 based on estimated population of250 people x 50 gallons / person/day 250 50 gallons* 365 = 4 56E6 gal/yr m3/ 264 gal = 17 280 m3 N content based on average of 15 groundwater samples collected by C. Shaw and M Nelson 12 Jan 97 and analyzed at the labs of the Soils Dept. Univ of Florida which had avg N of 1 .13 mg/1. N = 1.13 mg/I 1000 l/m3 1.728E4 m3 kg/1E6 mg= 19 5 kg N 3 based on estimate (Back, 1985 ) on average discharge of groundwater per km of coastline in northeastern Yucatan N = 1.13 mg/ 1 1000 l/m3 8 6E6m3 kg/1E6 mg= 9 720 kg N 4 tidal exchange -estimated on basis that 1 m of saltwater underlies and mixes with freshwater : 1000m 1 000m 1 m = 1E6m3 and that turnover is every 10 days 365 / 10 = 36 5 /yr 1 E6m3 = 36 5 E 6m3 /yr N concentration in seawater (Drever 1988) averages 0 005 mg/kg total N = 36 5E6m3 0 005 mg/kg* kg/1E6mg 1.025E3kg/m3 = 18 7 kg 5 Food inputs ofN taken to be equal to sewage-content ofN 6 wastewater infiltration based on 30 gal / person/da r estimate 30 gal/per pers ./ day 250 people 365 day /yr* m / 264 gal = 10 370 m3 N based on average levels of 45 mg/1 in septic tank effluent (from this research study ) 45 mg/I 1000 l/ m3 10 370 m3 kg/E6 mg= 466 7 kg with wetland treatment: 10 mg N / 1 1000 l/m3 8300 m3 kg/E6 mg= 83 kg 50% reduction in mangrove: 41.5 kg 7 storage w / o treatment based on 25% uptake ofN (see note 9): 2748 kg storage with treatment: 25% of 10526 kg N = 2631.5 + 50% of 425 5 kg N reduction of sewage : 413 = 3045 kg N 9 without sewage treatment: if 50% of input N (10 993) is either volatilized as N2 gas or taken up by sediments bacteria and vegetation in the coastal zone then 5 492 kg will be re l eased to the sea in subsurface flow wetland systems with further treatment in receiving wetland : discharge = 5 x 10 526 = 5263 + 41.5 from sewage = 5 305 kg

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242 a/ Nitrogen budget without sewage treatment Food --4-67-~ Tide+ inland GW +pumped wate~ One square kilometer developed coastline Akumal, Mexico Nitrogen kg N/yr 467 b/ Nitrogen budget with constructed limestone wetland treatment systems + receiving wetlands Foo:.:d=----467 Tide+ inland GW, +pumped ---:------:-:-:---:------.. One square kilometer developed coastline Akumal, Mexico wale~ 10,526 Nitrogen kg N/yr 41.5 (-425 5) Figure 3-63 Diagram of nitrogen budget of one square kilometer of developed coastline Akumal Mexico Figures in parentheses show changes in budget if all sewage is treated by constructed limestone wetlands and receiving wetlands Subsurface discharge to sea 5,492 Subsurface discharge to sea 5,305 (-187)

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243 Table 3-61 Organic compounds (BOD) budget of a developed square kilometer of coastline, Akumal, Mexico, with no sewage treatment and changes if wetland systems are installed. Item Inguts to system : In water : 1 Precipitation 2 pumpedGW used by people 3 Inland groundwater flow 4 Tidal exchange Subtotal in ( water inputs) In solids : 5 Food Total in Inside system: 6 Addition to groundwater from domestic sewage 7 Increases in storage in the system Oumuts from system : 8 ET Quantity of water m3/yr 1.05E3 1.728 E4 8.6E6 36.5 E6 45.123 E6 -------------1.037 E4 --------------8.5859 E5 9 Subsurface groundwater 44 26441 E6 discharge to sea Notes: (see also notes to Table 3-65 and Table 3-67) 6 BOD kg/yr neg neg neg neg neg 1504 1504 1504 752 752 wastewater infiltration based on 30 gal/person/day estimate 30 gal/per pers./day 250 people* 365 day/yr* m3/264 gal = 10, 370 m3 75 ( difference is 1429 kg BOD) 1429 75 ( difference is 677 kg BOD) BOD based on average input of 145 mg BOD/kg and discharge of 18 mg/I in wetland system effluent (from this research study) 145 mg/I* 1000 Vm3 10,370 m3 kg/E6 mg= 1504 kg BOD 18 mg/I* 1000 Vm3 8,300 m3 kg/1000 mg= 149 kg + 50% reduction in mangroves= 75 kg 9 d i scharge to sea : if50% of BOD is removed in groundwater : 752 stored in biota

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244 al Organic matter (BOD) budget without sewage treatment Food-----... 1504 Tide+ inland GW +pumped water One square kilometer developed coastline Akumal, Mexico BOD kg BOD/yr -,--.;:. 1504 Subsurface discharge to sea 752 b/ Organic matter (BOD) budget with constructed limestone wetland treatment systems + receiving wetlands Food-----... Tide+ inland GW +pumped water 1 neg. One square kilometer developed coastline Aku~al, Mexico sewage -----...;::i... BOD kg BOD/yr 75 (-677) ,---:~ Subsurface discharge to sea 75 (-677) Figure 3-64 Diagram of organic matter (BOD) budget of one square kilometer of developed coastline, Akumal, Mexico. Figures in parentheses show changes in budget if all sewage is treated by constructed limestone wetlands and receiving wetlands -

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245 Table 3-62 Coliform bacteria budget of a developed square kilometer of coastline Akumal, Mexico, with no sewage treatment and changes if wetland systems are installed Item Quantity of # of fecal Changes if wetland water m3/ yr coliform systems are used 1 2 3 4 5 6 7 Notes: --------... Inputs to system : Precipitation PumpedGW used by people Inland groundwater flow Tidal exchange Total in Inside system : Addition to groundwater from domestic sewage Outputs from system : ET Subsurface groundwater discharge to sea 1.05 E3 1.728 E4 8 .6E6 36 5 E6 45 123 E6 1.037 E4 8.5859 E5 44 26441 E6 (see also notes to Table 3-50 and Table 3-52) 5 neg neg neg. neg. neg. 1.04 El4 1.04 El3 wastewater infiltration based on 30 gal/person/day estimate 30 gal/per pers./day 250 people* 365 day /yr* m3/264 gal = 10 ,370 m3 # of fecal coliform 0 001 El4 ( difference = -1.039 El4) 0 005 El3 ( difference = 1.035 El3 coliform) Col i form numbers based on influent of 1E6 per 100 ml (1E7 per liter) and discharge of 2000 per 100 ml (2E4 per liter) in wetland system effluent (from this research study) 1E7/liter 1000 l/m3 10 ,370 m3= 1.04 E14 coliform 2E4/liter 1000 l/m3 8 ,300 rn3 = 1.66El 1 coliform (0. 001 E14) 7 without sewage treatment : if coliform are reduced 90% before discharge to sea : = 1.04E14 .1 = 1.04E13 with wetland treatment systems : if receiv ing wetlands further reduce coliform by 50 % then discharge w ater will contain 0 01E13 5 = 0 005E13

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246 a/ Coliform bacteria budget without sewage treatment One square kilometer developed coastline Akumal, Mexico Subsurface discharge to sea Tide+ inland GW +pumped water Gdditionin ewage isposal 1.04 E14 1 04 E13 Tide+ inland GW +pumped water negl. Coliform bacteria # b/ Coliform bacteria budget with constructed limestone wetland treatment systems + receiving wetlands One square kilometer developed coastline Akumal, Mexico Gdditionin sewage disposal 0 .001 E14 Coliform bacteria # (-1. 039 E 14) Subsurface discharge to sea 0.005 E13 (1.035 E13) Figure 3-65 Diagram of coliform bacteria budget of one square kilometer of developed coastline Akumal, Mexico Figures in parentheses show changes in budget if all sewage is treated by constructed limestone wetlands and receiving wetlands

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CHAPTER4 DISCUSSION Contribution of Research to Science of Ecological Engineering The principal contributions of the present research to the science of ecological engineering are in its use of local limestone gravel as substrate for the wetland, the demonstration that high species diversity can be maintained from the outset in a constructed wetland and its successful integration in the regional environment by the use of mangrove wetlands as the final bio-filter for the treated wastewater. Limestone proved to be effective in improving phosphorus treatment by the wetlands (Figure 3-39 and Figure 3-40) Since limestone is a local Yucatan material, it also was important in lowering cost of construction and increasing the use of regional natural resources compared to alternative, conventional sewage treatment systems Although the research aimed at high diversity, it was unexpected that the wetlands would substantially increase and sustain plant species beyond the 35 planted (Table 3-1 ), demonstrating that species from the local environment were able to successfully invade and contribute to the ecosystem. This runs counter to current practice in constructed wetlands for sewage treatment where few species are planted, and almost all of which tend to be dominated by aggressive pioneer species of wetland bulrush reed and cattail. 247

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248 The use of mangroves as a final bio-filter and recipient of the effiuent from the limestone wetlands may be an important advance in ecologically engineering for usually constructed wetlands are placed into environmental contexts with little regard for their integration in the larger ecological system In coastal Yucatan the mangroves are the natural interface between the human economy and the beach/marine zone and off er great advantages in that they have an organic sediment which can function as a biotic filter for groundwater flow of nutrients This type of mangrove use should increase awareness of the importance of the mangroves in maintaining environmental health in the region and offer cogent reasons to prevent their continued destruction for tourist development. The wetlands have also been shown to be less costly in construction and operation than conventional sewage treatment (Tables 3-34 and 3-35) The limestone wetlands also use far more local resources and less imported goods and services (Tables 3-36 and 337) Both these factors facilitate their practical application for third world tropical countries where capital and technical expertise is limited Analysis of the regional nutrient budgets show that the wetlands would prevent virtually all anthropogenic nutrients from entering the groundwater and impacting coastal ecosystems (Tables 3-59 to 3-62) This type of ecologically engineered system may help ensure the health of regional ecosystems normally put at risk by tourist development. Ecological Succession in the Limestone Wetland Units The Akumal limestone wetlands have demonstrated a rapid pattern of ecological succession In August 1996 the wetlands were first planted and initially had only partial cover of the ground little canopy structure and an average height of 0.5 m. The wetlands

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249 were not connected to sewage flow until December, 1996 and during that period demonstrated little growth Once sewage flow commenced, plant growth and canopy development were quite rapid as ecological succession theory would suggest. By May 1997 when the first extens i ve surveys were conducted, the dominant plants were C anna edulis Ner i um oleand e r T ypha domingen s is and Aloca sia e sculenta and average height had increased to lm. By December 1997 and July 1998 the increasing prominence of upper canopy trees and palms was evident. Lower canopy vegetation remained, but the system now favored shade-tolerant species Lower canopy and annual species were the most likely species to be lost from the system. By July 1998 canopy closure averaged 85% in the wetlands (Table 3-15) light interception was around 90% (Table 3-14) and average plant height was around 2 m (with some of the top canopy reaching 4-5 m). It appears that the wetlands are still in early succession On each of the last two surveys (December 1997 and July 1998) about 20% of previous species were lost and were replaced by new species Some of the differences in development may be the result of stochastic processes and even from the random choice of which plants were placed in the different cells While the striking difference in plant development and leaf area index between first and second cells has been eliminated in Wetland System 2 there is still a marked difference in Wetland System 1 (Table 3-11 ) Odum (1994 ) notes that the equalization of productivity and respiration seen in the later stages of many successions may not apply in situation where ecosystems receive a continued input of nutrients and convert it into organic storage as in a sewage treatment wetland Detritus flushed into mangroves is likely to be beneficial. Currently

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250 plant growth and canopy development still continues and may be expected to do so until trees and palms attain their full height. Succession theory predicts that organic matter will build in the ecosystem ( Odum 1971) a result not seen in the two years since construction (Figure 3-26) However, the original sawdust mulch has been replaced by litterfall and as biomass continues to increase one would expect the quantity of litterfall will increase Animal usage of the wetlands was not monitored in this research but it was noted that frogs invaded the wetlands within months of its creation. Snake skins have been found in the system and birds have been observed in the system Dozens of insects were observed during the studies of leaf holes (Tables 3-12 and 3-13) on the plants, evidence of active herb ivory Figure 3-45 summarizes the main processes in the ecosystem during its first two years including the inputs and transpiration of water the production and deposition of organic matter the absorption of nutrients and possible role of salt in maintaining biodiversity. Comparison of the Akumal Systems with other Treatment Approaches The Akumal wetlands are low in cost and low in requirements for imported goods and electricity as are other low-tech approaches such as use of surface flow wetlands and aerated lagoons. However aerated lagoons and surface flow wetlands may not be suitable for use in the Yucatan unless built with impermeable liners as otherwise wastewater will be lost to the permeable limestone before adequate treatment is effected

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251 Conventional sewage treatment plants are very capital-intensive Three-quarters of overall costs are involved in the pumping required to move raw sewage to the centralized sewage plant ( Southwest Wetland Group 1995) Much of the cost for conventional sewage treatment is for purchased goods which originates outside the region and frequentl y is imported in third world countries Operation and maintenance costs are high, since such facilities require highly trained technicians and engineers For example the University of Florida wastewater treatment facility has capital costs over three times higher per person than the Akumal wetlands and operating costs at $27 / person/year are nine times higher (Appendix D Table 3-36 ) Electrical costs are high for conventional sewage treatment plants since much of the system process relies on machinery Maintenance for such systems can be expected to be more expensive in the Yucatan because of the tropical environment, salt-spray and saline groundwater and the high cost of importing equipment from elsewhere in Mexico or the United States Treatment by package plants decreases over time with poor maintenance of equipment and inadequate technical supervision (Reed et. al. 1995) In addition, conventional treatment systems and package plants are designed to achieve secondary treatment standards ( < 30 mg/1 of biochemical oxygen demand and total suspended solids) which may be inadequate for preventing eutrophication of marine and terrestrial environments Large amounts of sludge are produced which are difficult in an environment like the Yucatan to dispose / use in a responsible manner. For example, the sewage treatment system for the city of Cancun Quintana Roo has contributed to pollution of the Cancun lagoon

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252 Shallow-well injection following septic tank residence is low cost but not very effective in reduction of organic compounds, nutrients or coliform bacteria or in preventing their impact on sensitive coastal marine ecosystems Septic tank residence with adequate holding time, only reduces influent BOD < 50% (TV A, 1993) Wastes in partially treated wastewater are likely to accumulate in the groundwater and coastal waters of the Yucatan In similar geological setting, in the Florida Keys sewage injected into shallow wells on land was found less than one mile away in off-shore waters ( Shinn et al 1992) Aquatic plant treatment systems (Wolverton, 1987) and surface flow wetlands have the advantages of being low cost to build and operate and have been applied in many ecosystems and climatic zones, using locally available wetland species They often are designed for secondary / tertiary wastewater treatment with lagoons or other settling devices accomplishing primary treatment before release of the wastewater However surface flow wetlands require more area than subsurface wetlands T his is because subsurface flow wetlands are designed to make the wastewater flow through the entire volume of their gravel substrate as contrasted with surface flow wetlands where wastewater flows over the top of the soil bed. Thus the surface area of each piece of gravel in a subsurface system can function as a locale for hosting microorganisms and as a site for wastewater filtration sedimentation and microbial interaction A rule of thumb is that surface flow wetlands require about 100 hectares (250 acres) for treatment of I-million gallons/day wastewater loading vs 5-10 hectares (12-25 acres) for subsurface flow wetlands such as were used in Akumal (Kadlec and Knight 1996).

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253 The cost of the medium (generally gravel) and liners usually makes the cost per area more for constructing subsurface flow wetlands but this is offset by the smaller area and heavier loading that such systems receive. Thus subsurface wetlands are usually less expensive than aquatic plant systems or surface flow wetlands (TVA, 1993 Reed et al. 1995) For these reasons and because such systems would need to be lined if applied in the Yucatan, there is probably limited scope for the use of surface flow wetlands for wastewater treatment in the region Aquatic plant constructed wetlands may also generally require biomass harvesting (Bagnall et al 1993) which requires additional labor and is seldom cost-effective (Reed et al 1995). There may be applications where use of several approaches can be usefully combined. For example in some constructed wetland systems ponds have been used rather than septic tanks as the primary treatment stage to reduce construction costs Wetlands have also been used following conventional treatment or package plants to increase nutrient recycling and produce higher quality effluent water. There are numerous natural freshwater and saltwater wetlands that occur in the coastal zone of the Yucatan. E nvironmental protection regulations in the U.S have made it more difficult to obtain permits for the use of natural wetlands for sewage treatment or disposal, despite the fact that there are numerous examples of successful historical and recent use of natural wetlands for this purpose In the Yucatan the relatively open hydrology of wetlands due to the limestone geology and rapid movement of water into and through the underlying limestone cautions against the use of natural wetlands as a primary mechanism of sewage treatment. However these wetlands are the only coastal ecosystems with a substantial

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254 organic soil component, and as such they function as natural bio-filters. Perhaps the most appropriate use of such wetlands is as a final step in sewage treatment, following primary and secondary treatment, such as was done in Akumal. Comparisons with Temperate Latitude Interface Systems Nutrient removal of the Mexican constructed wetland systems compares very favorably with those of similar systems previously applied in temperate latitudes. The 85% BOD removal achieved in the Mexican wetlands (Table 3-21) is in the range of 8090% reduction reported for most wetland systems (EPA, 1992). However, temperate latitude wetlands are reported to achieve nitrogen reduction of <30% and phosphorus reduction of <15% (EPA, 1992), compared with the Akumal data which indicate reductions of 79% for nitrogen and 77% for phosphorus (Tables 3-19 3-17) respectively Reduction of coliform bacteria is generally 90-99% (EPA, 1993b), while the Yucatan wetlands have averaged over 99 8% removal over the course of this study (Table 3-27) Table 4-1 compares the Akumal wetland units with average values for subsurface and surface flow wetlands in North America (Kadlec and Knight, 1996) BOD loading for the Akumal wetlands is slightly higher than the average subsurface wetland and removal rates are higher (88% vs 69%) Total phosphorus loading in Akumal is less than 40% that of average North American systems and removal is 76% vs. 32%. Nitrogen loading in Akumal is around 4/5 that of typical subsurface flow wetlands, and removal efficiency is 79% vs 56% for North American systems. Many subsurface flow wetlands in temperate climates are started with just a few plant species, often virtually monocultural systems. These systems composed exclusively

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255 Table 4-1 Comparison of loading rates and removal efficiency of Akumal treatment wetland units with average North American surface and subsurface flow wetlands (Kadlec and Knight, 1996). Parameter Wetland system In Out Removal Loading m __ l .... msfl % kglha/d BOD Akumal wetlands 145 17.6 87.9 32 1 (Biochemical oxygen demand) Average temperate surface 30. 3 8.0 74 7.2 flow wetlands Average temperate subsurface 27 5 8 6 69 29. 2 flow wetlands TP Akumal wetlands 8.05 1.9 76.4 1.7 (Total phosphorus) Average temperate surface 3 .78 1.62 57 0.5 flow wetlands Average temperate subsurface 4.41 2.97 32 5.14 flow wetlands TN Akumal wetlands 47.6 10. 0 79 10. 3 (Total nitrogen) Average temperate surface 9.03 4.27 53 1.94 flow wetlands Average temperate subsurface 18. 9 8.41 56 13.19 flow wetlands Note: Akumal wetland data based on loading of 2. 7 m3 wastewater per day on area of 130 m2, using average wastewater data from this study. As designed, full loading would be over twice as much

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256 of Typha latifolia, Scirpus spp. or Phragmites australis are less attractive and less beneficial for wildlife However, some large surface flow systems have included natural wetlands and been managed to foster a wider biodiversity of plants and habitats (Kadlec and Knight 1997 ; Reed et al, 1995) Comparison ofEmergy Indices of Akumal Units Table 4-2 summarizes the emergy evaluation of the treatment system as compared with a package plant treatment and a larger conventional treatment system at the University of Florida (see Appendix C) Figure 4-1 presents an aggregated systems diagram of the Akumal treatment units and mangroves with flows of emdollars For the Akumal treatment wetland units, the majority of emergy apart from sewage was from local sources These inputs include wind energy, limestone gravel limestone rock and wetland plants. Purchased imported goods are less than one-third of the total emergy ( excluding that of the sewage itself) in the systems. Since the construction was labor-intensive, requiring local workers for excavation, construction of the concrete liners and placement of the gravel, the system to a large extent draws on and keeps both monetary transactions and emergy within the area By contrast the University of Florida system derives over 220 times more emergy from purchased goods and services than from free environmental resources ( excluding the wastewater) and the package plant derives over 2600 times as much emergy from purchased goods and services rather than from free environmental resources. The transformity of the output (treated effluent) (6.85 E6 sej / J) from the wetland system is higher than that of the Akumal package plant (4.83 E6 sej / J) reflecting the fact

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257 Table 4-2 Comparison of emergy indices for Akumal treatment units package plant at Akumal and the University of Florida wastewater treatment system (Appendix C) a/ Based on transformity for wastewater calculated as co-product of total emergy required to support people Emergy index Akumal wetland Package plant at University of units Akumal Florida conventional .-.... ..... v.-.......... ----~ .. .. ------------~--~---~-------treatment s y stem Purchased / Free 0 39 2 693 220 ( excluding sewage ) Transformity of output 6 .85 E6 sej/J 4 .83 E6 sej / J 4 .71 E6 sej/J Empower density 2 5 E19 sej/ha/yr 7.4 E 19 sej/ha/yr 14. 3 E20 sej/ha/yr ( emergy / area/time ) Purchased emergy per 0.3 E14 sej 2 3 E14 sej 1.0 El4 sej rson b / Based on transformity of wastewater of 1 0 E6 sej/J (food/services / water used) Emergy index Akumal wetland Package plant at University of units Akumal Florida treatment s stem Purchased / free 0.39 2 693 220 ( excluding sewage ) Empower density 6 2 El8 sej/ha/yr 1.95 E19 sej/ha/yr 3.3 E20 sej/ha/yr ( emergy / area/time ) Purchased emergy per 0 3 E14 sej 2.3 E14 sej 1.0 E14 sej person Erner rson 2.4 E14 se 2 5 E14 se 72 8 E14 se

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258 Sewage Free environmental resources Limestone Wetland Treatment System Emdollars (thousands) Figure 4-1 Diagram showing annual emdollar contributions in the constructed wetland system in Akumal, Mexico. From the economy Purchased Goods+ 258 5 Water

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259 that far less treated wastewater is discharged from the constructed wetland since more wastewater is utilized within the system Such use of emergy within the system rather than passing it out helps produce a high quality ecosystem The wetland transformity for treated wastewater is also higher than the University of Florida system (4 .71 E6 sej / J) perhaps reflects the economy of scale of a large wastewater plant and its very large throughput of wastewater Though the Mexican wetlands use a far greater proportion of locally available resources, and little purchased goods such systems require more space (land area) per person and time (hydraulic residence time) than large conventional treatment systems utilize. The Akumal wetlands use less than 15% the purchased emergy per person compared to the package plant (0 3 El4 sej vs 2 3 E 14 sej) while the University of Florida facility uses three times as much purchased emergy per person ( 1 0 E 14 sej / person) The wetlands have the lowest empower density with the package plant almost three times greater, and the University of Florida system being the highest (Table 4-2) Table 4-2 also presents the results of emergy comparisons if the treated sewage is treated as a product of the food water and services supporting their population rather than as a co-product of the total emergy support Green (1992) calculated the transformity of raw domestic wastewater to be 5. 54 E5 sej / J for Nayarit Mexico Bjorklund et al (1998) calculate a transformity of 5.46 E6 sej / J for Sweden Using a transformity in-between these values (1 E6 sej/J) since Akumal has many of the characteristics of a developed economy in its reliance on imported foods Using this

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260 transformity for wastewater has the consequence of reducing emergy flows by around 4 5 However the main relationships observed between the limestone wetland units package plant at Akumal and the University of Florida system persist. The purchased to free environmental ratio is unchanged, and the wetland systems still have the lowest empower density and the lowest emergy use per person (Table 4-2) Role of Limestone Substrate Unlike unreactive gravel (igneous and metamorphic rock) that has been predominantly used in subsurface flow wetlands, the use of local limestone as the primary substrate in the Mexican wetland units was important in controlling and stabilizing its biogeochemistry and treatment efficiency Limestone is predominately calcium/magnesium carbonate and its chemistry is dominated by the common ion effect which carbonate dissociation shares with the hydration of carbon dioxide (to form carbonic acid). The pH of the water determines which form, H2CO3 HCO3 1 or co3 2 will predominate in the system In subsurface wetland units where water level is kept below ground, algae and aquatic plants are absent. Photosynthesis occurs above the limestone / wastewater level. Thus photosynthesis had little impact on carbon dioxide levels in the underground Instead respiration by roots and bacteria increased carbon dioxide concentrations in the water column Limestone also aided phosphorus removal because of the reaction of calcium with phosphate as was illustrated in the laboratory experiments conducted during this study (Table 3-31). This is especially the case in these alkaline conditions where reactions

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261 with calcium and magnesium are the main determinants controlling phosphorus fixation (Reddy and D Angelo 1994) The addition of organic materials with the wastewater probably increased microbial respiration and CO2 production However, increase in carbon dioxide was buffered by reacting with the limestone to form bicarbonates. In contrast, anaerobic decay reactions which predominate in a subsurface flow wetland using wastewater high in sulfates tend to increase carbonate saturation and deposition (Drever 1988) Just as the dissolution of limestone is the controlling geochemical reaction in the Yucatan region we can also anticipate the slow dissolution of the large quantity of limestone initially placed in the Mexican wetland units Indeed, observations of discharge water from the treatment cells reveals a whitish color, indicative of carbonate dissolution materials Seasonal Changes and Effect of the Dry Season Although the climate of the Yucatan has a sharp dry season the coastal microclimate is moderated by steady flows of maritime tropical air from the east augmented by the sea breezes Annual temperatures do not show great variability in the Yucatan, with the hottest average monthly temperature (26 2 deg C.) occurring in June, and the lowest 23 1 deg. C. in December (Vi qui era et al., 1994 ) Average relative humidity is even more constant with a high of 88% in September and the low in March/ April with 81 % (Ibarra and Davalos 1991 ). As a consequence potential evapotranspiration is high year-round, averaging 4-5 mm/day in the rainy season yet still

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262 3 mm/day in the dry season. (SARR, 1997). Conditions were uniform enough for vegetation to flourish through wet and dry seasons. The Yucatan is a region with a marked period of higher monthly rainfall May through October when over 70% of the 1100 mm annual rainfall occurs, and a drier season November through April (Viquiera et al. 1994) During the warmer, rainy months, direct rainfall and freshwater subsurface inflow from inland result in larger groundwater prominence of the freshwater and in a net freshwater discharge to the sea. Consequently, there is a seasonal variation in salinity in the water supply of the treatment units and in the mangroves which receive their discharge effluent. Average phosphorus and nitrogen reductions were slightly greater in the dry, cooler months with 79% and 81 % reductions compared to 74% and 68% reductions respectively, in the warmer, rainy season. But biochemical oxygen demand reduction was greater in the warmer, rainy months with 94% reduction vs 86% in the dry cool season (Tables 3-17 3-19 and 3-21) The two-year data suggest that constructed wetlands for sewage treatment in the Yucatan can remain quite effective in its treatment results year-round Even in the drier winter months, solar insolation and warm temperatures permit active growth of vegetation and high metabolic functioning of microbes, since adequate water and nutrients are maintained though sewage inputs to the system. Hydraulic residence is longer since rain dilution of the wetlands is less Treatment efficiency in the wet season is assisted by higher average air temperatures, but diminished by loss of insolation through cloud cover and dilution by rainwater.

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263 Treatment of Wastewater Containing Sea Salt The wastewaters at Akumal are salty because the town water supply is pumped from groundwater where there is mixing of seawater with freshwater. The high biological diversity maintained by the Akumal systems showed that the regional vegetation was adapted to salinity in this range These biodiversity results were in contrast to the lower diversity saltwater wastewater mesocosms studied in North Carolina (Odum 1985) The salt content of the wastewater may be a contributing factor in the establishment and maintenance of high plant biodiversity Species tolerant of high salt content such as occur nearby in the mangrove wetlands have been able to survive in the system as have many non-halophytic plants that are able to withstand the moderate salinity of the wastewater and salt aerosols carried from the sea Indeed having an intermediate salinity may have been a factor holding in check species capable of aggressive dominance ( e .g. Typha spp ). The wastewater being treated in Akumal is saline generally averaging 3-5 ppt salt. This is in marked contrast to most wastewater treatment facilities that handle fresh originally potable water The presence of seawater means that in addition to NaCl there is a strong presence of sulfates since seawater contains 2700 mg SOJl on average (Da y et al, 1989) In the anaerobic conditions of wetlands containing saltwater, sulfate reduction usually dominates rather than the methanogenesis that often prevails in freshwater conditions T his is attributed to the competition for electron donors the larger thermodynamic yield and higher affinity of sulfate reducers to utilize compounds

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264 potentially usable by methanogenic bacteria (Capone and Kiene, 1988 ; Achtnich et al 1995) Simulation of Hydrological Extremes Simulations of the water budget model for the wetland treatment unit and mangroves indicate water flows and turnover times that help understand the processing of the various inputs What if? experiments with the model suggest the range of water volumes that may develop with extreme events Simulations were conducted examining the impacts of hurricane events increased population and sewage loading and decrease of inland groundwater due to interior development. Increasing population so that wastewater inputs are ten times greater results in increased water levels in the mangrove and increases biomass especially in the treatment wetlands (Figure 3-57 ) Development inland reducing groundwater discharge to the mangroves has the effect of lowering groundwater levels in the mangrove results in diminished water level (Figure 3-58). A hurricane producing heavy rainfall high tides and winds that reduce vegetation by half in the wetlands and mangroves leads to increased flow of treated effiuent into and out of the mangroves. Recovery of vegetative biomass to previous levels requires years The high tides are quickly flushed so that the flooding of the mangroves is a transient event (Figure 3-59). Transpiration of Treatment Systems Because vegetation productivity has been related to transpiration an estimate o f transpiration of the Akumal treatment systems is a productivity index as well as a major component of the hydrological budget. Evaporative water loss was limited since

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265 wastewater was maintained below the surface of the wetland air exchange was reduced by the dense plant canopy (Table 3-14 and Table 3-15) and because the ground was mulched and shaded Loss of water through transpiration increases total treatment efficiency of the Akumal wetland compared with conventional sewage treatment facilities The residence time in conventional treatment sewage facilities is 2-4 hours allowing for little loss from evaporation so that virtually all the influent water leaves the system However in the wetlands the loss of20-30% of water through transpiration means that total pollutant removal on a mass balance basis is greater than is indicated by discharge water analysis alone For example if P levels in the discharge water are 75% lower than those in the septic tank in the wetlands and transpiration removes 20% of the wastewater actual phosphorus reduction totals 80% If transpiration is 30% of wastewater then phosphorus removal increases to 82 .5%. Transpiration of freshwater tends to increase salinity of the wastewater in the treatment units since relatively freshwater is lost through plant leaves. However the measured salinity in the treatment cells over the course of this study showed predominantly a slight decrease in salinity (Table 3-26) presumably because of dilution by rainfall on the wetlands Maintaining Vegetative Biodiversity In the two-year study survival of planted species and environmental seeding produced a dense high diversity ecosystem. Maintenance of high biodiversity long-term will require successful re-establishment of seedlings of the wetland plants Some of the

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266 loss of species already seen may have resulted from the death of annuals, and the suppression of lower canopy plants and seedlings due to shading (Table 3-1 ) The maintenance of high species diversity is of theoretical interest. Some of the factors which may have helped maintain diversity and prevented a few species from dominating the system are 1. the use of slightly saline which allows a range of both freshwater and salt-tolerant plants ( as noted above) 2 continued inputs of nutrients which may act as a stress keeping the ecosystem in a productive, intermediate stage between primary succession and maturity (Odum 1994) 3 nearly constant water temperature (27 0.5 C year-round) 4 t he pulses of nutrient input which low and high tourist season occupancy produce Impacts of Effluent Disposal on the Mangroves Results from the present study have shown that there has been an only moderate increases in nutrient levels in mangrove groundwater (Table 3-46, Table 3-47) and soil sediments (Table 3-43, Table 3-45). Longer-term effects on the mangroves need to be assessed Feller (1995), Lugo et al (1976), and Sell (1975) indicated that mangroves typically are nutrient limited both for nitrogen and phosphorus and can increase productivity with added nutrient inputs Walsh (1967 cited in W.E, Odum et al, 1982) found mangroves were net sinks for nitrogen and phosphorus Nutrients are removed in mangrove ecosystems by prop root periphyton, the fine root system, organic sediments,

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267 algae and bacteria/fungi Thus there is a good likelihood that mangroves will continue to be effective at nutrient removal from wastewater discharge. Clough et al ( 1983) expressed concerns that the addition of water containing organic carbon compounds will lead to increased anaerobic conditions in the sediments further lowering redox potentials However, W .E. Odum et al. (1982) note that the sediments underlying many mangroves tend to be very anaerobic with redox values of 100 to -400 mv due to their high organic matter content. The 75-80% organic matter content in the Akumal mangroves before wastewater discharge exceeds the 10-20% considered more typical of mangrove soils and is indicative of isolation from tidal erosion (W E Odum et al 1982) After discharge of treated sewage salinity levels were reduced (Table 3-52 ), and the small extent of phosphorus increase in soil sediments indicate phosphorus use by the mangroves (T able 3-45). Carrying Capacity for People Coastal Development Potential To anticipate the potential value of these wetland treatment units in preventing pollution caused by tourist development an emergy evaluation was made of a developed square kilometer of coastline around the Akumal study site supporting 225 people and employing 125 people (Table 3-55). Without a good treatment I recycle system large amounts of anthropogenic organics nutrients and coliform bacteria will be released into the coastal and marine environment (Table 3-58 ) with impact on coral reefs beaches health and tour i st economy In addition if development results in further loss of the mangrove areas

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268 nutrients flowing subsurface from inland sources that are currently intercepted will also be discharged to the marine environment. Thus future planning should ensure adequate area is left in all de v elopments for installation of adequate wetland treatment areas to absorb the additional nutrient loading tourist development brings. Needed for one kilometer of coastal development supporting around 250 people are some 900 square meters of constructed wetland plus 1-2000 square meters of mangroves Currently development is concentrated on the coastal zone itself but the location of more human population and/or industry in inland areas will impact sustainability of coastal resources by diverting groundwater and increasing nutrient loading of remaining groundwater Percent of Economy Required for Wastewater Processing Kadlec and Knight (1996) indicated that constructed wetlands are at least 50% less expensive than conventional sewage treatment in capital costs. Operational and maintenance costs are even lower averaging 10% However this varies considerably depending on land costs Tables 3-34 and 3-35 show the economic advantages of the Akumal wetland treatment. Capital costs for the limestone wetlands were around $165 / person compared to $385 / person for a package treatment plant ; and maintenance costs for the wetland were $3/ person compared to $27 / person for the package plant. On a regional basis the constructed wetlands would require 0 3% of yearly monetary flows along a square kilometer of developed coastline vs 1 1 % for the package plant ( Table 3-34 Table 3-35 and Table 3-55).

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269 The limestone wetlands cost approximately $450 per year ( over its 20 year anticipated operation ) to treat 3000 gallons per day which is $0 .15 per gallon of wastewater. This is considerably lower than the $0 62 per gallon reported in a survey of subsurface flow wetlands in the United States (EPA, 1993b) This may reflect lower labor and construction costs in Mexico as well as the fact that the research wetlands entailed no land costs as they were built on land already allocated for landscaping purposes Perspectives from Regional Simulation Model A regional simulation model was developed in order to elucidate a few of the important interactions between the natural environment and the human economy including tourism in the Yucatan F igure 4-2 shows the systems diagram with equations Figure 4-3 shows calibration storages and flows and Figure 4-4 shows a simulation run of the model showing changing levels of assets coral algae nitrogen and image as development proceeds Table 4-3 presents the program in BASIC for the simulation model. In the systems diagram algae (A ) and Coral (C ) compete for sunlight energy (J ), with some sunlight (R1 ) going to the algae and a portion of the remainder (R2 ) to the corals Algal growth ( ki) is autocatalytic using sunlight nutrients (N), and algal standing biomass for increase and declining through respiration/death (k5). Coral growth is also autocatalytic depending on the interaction of sunlight and coral biomass Natural coral losses (k13) are augmented by anthropogenic damage linked to increased development (k16) Coral presence adds to the regions image (I) which in turn helps attract income

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270 To Sea Akumal R1 = J/(1 + k1*N*A) di = k7*C k14*I Rz = R1/(l + kz*C) dS = k9*S*M/P1 k13*S dA = k4*R1 *N*A -k5*A dM = k11 *l*Td k1 z*M dC = k3*Rz*C kG*C*S k16*C dN = Jn + k1 o*S*(M/P1) ks*N*R1 *A k1 s*N Figure 4-2. Systems diagram and difference equations used for simulation model of the interactions between the natural environment and the human economy along the Yucatan coastline.

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271 To Sea 8 Akumal Figure 4-3. Systems diagram for Yucatan coastal model. Values shown are steady-state storages and flows between components

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272 N Time-----,:>~ Assets (S) 1_6Q Nitrogen (N) 3_70 Coral (C) _160 Algae (A) 160 Image (I) p.4 I N Figure 4-4 Computer simulation of the Yucatan coastal model. The legend gives the full scale values of the ordinate for each quantity.

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273 Table 4 3 Program in BASIC for simulation model of interactions between natural environment and human economy along the Yucatan coast. lOCLS 20 Screen 0 1 30 Color 0 1 40 Line (0 0)-(320 180) 1 B 60A= 5 70 C = 95 80N= 10 90 I = 1 110 S = 10 120M= I 150 Td= 50 160 J = 100 165 No = 5 170 Rem Coefficient values 172 Pl= 100 175 T = 1 178dt= O l 180 kl = 0 0000958 190 k2 = 0 020606 200 k3 = 1.212121 E-3 210 k4 = 7.492537 E-4 220 k5 = 0 5 230 k6 = 0 0001 240 k7 = 0 002 250 k8 = 1.492537 E-4 260 k9 = 0 5 270 klO = 9 5 280 kl I = 0.4 290 k12 = I 300 kl3 = 0 05 310 k14 = 0 2 320 kl5 0.5 330 kl6 = 0 03 Rem Scaling factors 350 AO = 2 360 TO= I 370 co = 2 380 NO= I 390 so= 2 400M0= 2 410 IO= 50 440 PSET (T 180 I / IO), 3 420 PSET (T 180 A / AO), 1 430 PSET (T 180 C / C0),2 440 PSET (T 180 I / IO), 3 480 PSET (T 180 S I SO), 4 490 PSET (T 180 M / MO), 5 500 PSET (T 180 N I NO), 6 505 PSET (T 180 A I AO), I 510 PSET (T 180 C / C0),2 540 R 1 = J / ( 1 + k 1 *N* A) 550 R2 = RI / (1 + k2 C) 560 dA = (k4*Rl *N* A) (K5* A) 570 dC = (k3*R2*C)-(K6*C*S)-(K16*C) 580 dS = (k9*S*M / Pl)(K13*S) 590 dM = (kl I *I*Td) -(Kl2*M) 600 dN = No + (K10*S*(M/Pl)) (K8*N*Rl *A ) -(Kl5*N) 610 dI = (K7*C) -(Kl4*I) 620 A = A + dA *dt 640 N = N + dN*dt 660 T = T + dt 700 If N < 0 then N = 0 710 If A > 100 then A = 100 720 If C > 100 then C = 100 730 If A < 0 then A = 0 740 If C < 0 then C = 0 750 If M < 0 then M = 0 760 If T < 640 goto 540 770 Print "A=", A ; C=", C N =", N S =", S

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274 (k11) from tourism (Td) This income adds to the region s money (M) and is used ( k12) to purchase goods and services (Gs) The growth of development structure (S) is autocatalytic (k15) from the interaction of goods and services (Mk12/P1 ) and existing structure. The increased development process both increases coral loss and adds (k10) to the quantity of nutrients (N) which can impact the natural environment. Nutrients receive a flow from the natural environment (J0 ) as well as from economic development (k10) while some of the nutrient outflow is taken by algae (k8 ) and the rest goes to the deeper ocean (k11) The coral reef plays a major role in sustaining the positive image of the region which helps attract investment and tourist flow to the region Decreased coral cover resulting from development without adequate sewage treatment increases algal domination which acts to lower the image thus dampening tourist development. Over time these balance and the overall system adjusts to a level of development far below the early boom ". Coral cover at first rapidly decreases, then recovers as development tapers down (Figure 4-4) Simulation results are sensitive to starting conditions If nitrogen begins at much higher levels tourist development peaks at far lower levels and the system regains a steady state earlier (Fi gure 4-5a) If coral begins at zero the system crashes since there is no pull for continued investment and tourist development (Figure 4-5b ) If assets and money begin at much lower levels the process of boom takes longer to develop but rises to a greater peak, and steady state conditions at the end have less coral cover than under the model s standard run (Figure 4-5c )

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al bl cl I I i I I L 275 Assets (S) 1_6Q Nitrogen (N) J20 Coral (C) _160 Alg:ie (A) 160 Image (I) 6.4 Cl.. ,J Assets (S) 1_6Q Nitrogen (N) J20 Coral (C) .160 Alg:ie (A) 160 Im:ige (I) 6 4 Assets (S) 1_6Q Nitrogen (N) 320 Cora.I (C) .160 Alg:ie (A) 160 Im:ige (I) 6 4 r Figure 4-5 Simulation runs of the interaction of the environment and human economy in the Yucatan. a/ Impact of starting with nitrogen at ten times higher value b/ Impact of starting with coral at zero c / Impact of starting with money and assets at 1/10 value

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276 The model simulates some components of the present situation in the Yucatan, since diving, snorkeling and fishing are a significant part of the tourist appeal of the area. Most of the hotels offering coral reef exploration now have inadequate sewage treatment, and much current development is threatening other parts of the environment, such as mangroves which help protect the marine environment. If the coral reef suffers great degradation (as occurred in Jamaica) it seems clear that tourist revenues will decline as a result. Future Potentials of the Designed Treatment System The scope for application of the wetland treatment system along the Yucatan coast is great. Already interest in such systems from those who have seen the prototype systems at Akumal has led to some fifteen additional systems being built from Tulum to Playa del Carmen . The scale thus far has been from individual house systems hotels/condominiums of up to 50 people and a theme park with 1500 visitors per day. In the Cancun area the government has decided that no new connections will be made to the existing municipal sewage treatment plant which is already over-loaded, obliging new businesses and homeowners to do on-site treatment. The principal advantages that have attracted new applications are the low-cost and low-maintenance of the wetlands plus their attractiveness To lower costs oflarger systems, it is anticipated that rubber or polyethylene liners will be used instead of concrete Each new system has served as a testing ground for planting new plant species and an additional 10-15 palm tree and shrub varieties show promise of doing well in the wetland systems The search for suitable wetland

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277 plants that have economic potential continues Already bananas in several systems have successfully produced fru it. Several of the palms in the Ak:umal systems have value as thatching material. In order to develop systems which will be inexpensive enough to be used by local Mayan families and communities construction costs need to be lowered and more useful products produced Ideally it may be possible for a local family or community to build such systems themselves (thus lowering construction costs ) and to contract with local farmers to maintain the system in return for harvesting rights Long-Term System Prospects It is unknown how long the wetland system will remain effective at sewage treatment. A number of subsurface flow wetlands have been operating successfully for over 10-20 years (Kadlec and Knight 1996 ; EPA, 1992). While BOD reduction tends to be adequate phosphorus and nitrogen removal have sometimes been inadequate in wetlands constructed in temperate latitudes (EPA, 1992). The limestone may remain effective at phosphorus uptake for a considerable time as its starting concentration was quite low (40 mg/kg). The 6 mg P/kg uptake of the limestone during the first year of operation may reflect the rapid increase in plant and microbial biomass during early succession in the wetlands It is to be expected that biotic primary productivity will decline or stabilize as time goes on, thus placing increasing importance on the limestone to act as a sink for influent phosphorus The phosphate mining district of Florida demonstrates that phosphate substitution for carbonate in limestone (over geologic periods ) can continue indefinitely producing minerals that are 5-20% phosphorus (Gilliland 1973 : Odum et al 1998 ) At

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278 the rate of 50-100 mg/kg of phosphorus emichment it would take some 100-200 years before the wetland limestone gravel reaches 1 % phosphorus content. While occupation of surface area may be a limiting factor in such uptake bioturbation and the high porosity / permeability of limestone may continue to ensure continued uptake Nitrogen removal by the wetlands increased over the first two years of operation as plant productivity and root penetration of the subsurface zone increased From half to two-thirds of nitrogen removal in constructed wetlands comes from gaseous release of the nitrogen after nitrification/denitrification processes (EPA 1992) Therefore oxygenation of the rhizosphere by plant roots is an important factor for otherwise onl y a reducing environment might prevail under the surface of the limestone. The inclusion of wetland species able to deeply penetrate and the inclusion of a diversity of plant species with varying rooting patterns may help to maintain adequate oxygenation For the Akumal system the inclusion of the mangrove as a final treatment step gives a safety factor for ensuring continued effective wastewater treatment. Should additional nutrients be discharged from the constructed wetlands the mangroves may help prevent additional nutrients from reaching marine ecosystems This may be especially true for phosphorus which is the most limiting nutrient for mangroves along this coastal zone (Feller 1995). The diversity of the wetland vegetation may also offer long-term performance benefits as it will tend to make the system less prone to system failure due to disease or other plant failure than if the system was dominated by several plant species.

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279 Hurricane events which are a periodic event along the Yucatan coastline may act to reset the successional clock", dramatically decreasing canopy cover and system biomass in both constructed wetlands and mangrove ecosystems In the event of long-term decrease of limestone uptake of P below acceptable levels or to decrease of system performance because of clogging through deposition of sewage solids or organic material the system may be regenerated by installation of fresh limestone The old limestone may be used as a slow-release fertilizer for area gardens or farms. Since the limestone accounts for less than 20% of original construction costs, it will be cost-effective to replace the limestone on this periodic basis if necessary Authorization Meeting in Mexico On August 18 1998 representatives of Planetary Coral Reef Foundation Mexico were invited to the University of Quintana Roo at the state capital of Chetumal in order to present the limestone wetland systems to the faculty and federal and state government agencies. Those present included the Commission National de Agua (CNA) and Recursos Naturales y Pesco de Quintana Roo. Results from the present research study were presented, as well as many of the additional systems that have been built along the Yucatan coast to date Questions raised following the presentation covered the economics of wetland treatment compared to other alternatives the impact of catastrophic events such as hurricanes the mechanisms responsible for nutrient uptake and coliform reduction, and the methods by which larger cities might benefit from such approaches

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280 Many of those present indicated that there is growing concern in the government and university that t he development in the northern portion of the state and particularly Cancun was allowed to proceed too rapidly Thus there was inadequate regard for issues such as preservation of key ecosystems such as the mangrove and other wetlands and before adequate sewage treatment systems were available. The southern portion of the state (from the Sian K an Biosphere Reserve to the Belize border) is still in very early stages of tourist and other development and could still put in place better measures for integration of the human and natural environment. At the conclusion of the three hour meeting the head of the University of Quintana Roo Rector Efrain Villaneuva Arco announced support of the installation of a demonstration limestone wetland to treat the sewage of 200 people at the University as a facility for on-going research and education. The author was invited to design the wetland working with faculty of the University who are developing improved designs for septic tanks which will serve as the primary treatment of the system Questions for Research Important topics that need future research are the following: Biodiversity What impact does the presence of high biodiversity have on system performance in treating wastewater? Will anaerobic conditions in the subsurface rhizosphere limit the variety of plants? Can such high biodiversity be maintained long-term? Which factors are responsible for the maintenance of high biodiversity (salt, nutrient inputs original

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281 planting proximity to seed sources wind or animal seed dispersal)? With increasing scale of such wetland systems will biodiversity patterns be different? Mangrove Change Will the mangrove ecosystem be fundamentally altered by the addition of treated effiuent? What impact will be seen on growth rates of different mangrove species and on other system parameters such as canopy closure soil depth hydrological regime species abundances? What impact will wastewater effiuents have on permanent and migratory fauna that utilize the mangroves? What loading ratios will sustain mangroves? Useful Life of the Wetland System What is the likely longevity of the wetland treatment units? Will there be gradual loss of hydraulic conductivity and at what rates through deposition of secondary minerals suspended solids or filling of void spaces by deposition of peat from anaerobic carbon reduction? Will the limestone continue to play a role in the retention of phosphorus or will this be diminished over time as gravel surface area is occupied? Will bioturbation ensure continuous availability of limestone substrate for phosphorus reactions? Acceptability and Affordability by Local People What modifications such as using geomembrane liners rather than concrete can be made to further lower construction costs? Can the systems be made profit creating rather than simply low-cost by concentrating on the inclusion of usable products (timber fuel food and fiber) which can be harvested from the wetland units? Which products are most desired by and acceptable to the Mayans living in the area?

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282 Summary Over the course of a two year study, a new system of limestone subsurface flow wetlands was developed and coupled to final treatment in mangrove wetlands The units recycled nutrients and improved the quality of saline domestic wastewater The system has maintained a high level of biodiversity of wetland plant species. After two years the upper canopy of wetland palms and trees is 4-5m (13-16 feet) tall with dense canopy closure. Canopy closure and Interception of light after just two years is already similar to that of natural Yucatan wetlands This system is inexpensive and with advantages over alternative sewage treatment approaches in using a preponderance oflocal resources, few imports and little use of machinery and electricity Its two stages were adapted to the hydrogeological setting of the Yucatan coast ; limestone gravel helped ensure adequate treatment before release and natural mangrove wetlands were utilized as the most appropriate biofilter for nutrients remaining in the effluent from the constructed wetlands . Emergy evaluations show the ratio of imported inputs to free, environmental inputs is small Economically, the system compares favorably in having low capital and operating costs In addition there are aesthetic benefits habitat protection for wildlife and producing useful products such as fruit fiber building materials etc Yucatan limestone used in the system contains very little phosphorus, and the rate of increase during operation was small, suggesting the substrate may remain effective in phosphorus uptake long-term. Nitrogen and phosphorus increase in the mangrove soils

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283 was small ( < 15%) Coliform bacteria concentrations and chemical oxygen demand were at background levels within 6 m of discharge. The eastern Yucatan is in the midst of extremely rapid tourist development. The present work demonstrates the feasibility of designing and implementing ecological engineering solutions that can help integrate the human economy with the natural environment. This wastewater treatment system has potential for more widespread application in tropical coastlines and countries that are in great need of low-cost low tech solutions that employ natural systems to solve environmental challenges

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APPENDIX A CHART RECORDER DATA FOR AKUMAL 284

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Scale .. 285 WfM ,, ::--==='--L_, ===-=--=---=--=-.. ..:..... _ _ _ _ _ _ ___ __;_ __ 9;/1271~ ~ ~/2-.,"' __ -. F i gure A1 Water level record for cenote near wetland treatment unit, 2 7-28 May 1 997 I ,,._, ''e'.i-J_,-i~-+D ~

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r-= L:: I J . r ----Scale ,, .. 286 ., r ' ' ... ' ... ------~~-----_ _________ Figure A-2 Water level record for cenote near wetland treatment unit 28-29 May 1997 i ---

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287 ' I Scale ~------r--------------. r"" -------Figure A-3 Water level record for cenote near wetland treatment unit 29-30 May 1997.

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--288 -'\ Scale ..... --,,,1" r ,. , ., f--'--'----1...-L_ --=--== ~uf_ ,_.;,..__:._ ::t ~ -~-----------------------Figure A-4 Water level record for cenote near wetland treatment unit, 30-31 May 1997

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,-..=--= ->-:===l _..:,__1 --:t--: --, Scale t--.. -.e--I I ... --~ >---~J 289 t -t--.:=~ 1----1---1-:.:i---=~.~l --~-~=::=-:1 -:-:::..:_:: -_ '. I :==-~-, :.::.=.::-.: :.:..:~_:_-=::: ; -, .. t: ::.. --;. -~I r:::-: ,.:_ ,-I : : --+--.:L:;_::=1,....=====-~ E : :==== ~-__ I :----,.. --. ........ ,..,., -' ll ---------. --.... .. ....... r.. --..... ..:.:=::: ~ .:_:. : _~_ . ... ... t ,.;..._ -f'' ... ,.-,--,-c -J 'J' -r= -----=1== -1----~t=~~-=1=~::-~---... ,.._ :t:::. : r--:: .. _:.. f:.E : .. -i--,.... -:...-.::-:j:::' c:::~; L 1-. .-t.. 1---r---.. -----: E: 1----... -i":.::: 1 ~..:.~ : ::.~ : 1--.. . : =-: t= ... -::_:: :_t=_::_:\ :i ~ : f==: _-_ :t-I -'--...__ Figure A-5 Water level record of tidal heights at Yal-Ku Lagoon 27-28 May 1997.

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~F ,t::::t :..-.---....;..,....-----::.:::~ :~n:=-.:: ::~ I --" r _.,._ ,_______ -;-T---: I=#/"~ t::=i1 ---~ ~-__ __._ -, :. ~ -,-,,,, ,-, .... 1-i ,-,. ~-If _w..;__ .::,':' t- ---t--r--r Scale rt----,~ H I 290 ---,--+--1-,-+---, ~ ----+-~ -+---:, : :;:;: r .--1 ~-..,.. -:--,-i-i--f-~~,_. I, c-t+ .,-,.. --1:.~--, ~-L f:=l I ,~.::t,4-;::.~l : r 1 ___ : ~ .. _.: Q ,:,, :-: -'!--:::F-= -, -. t -. .. ~ . ... -1.:. ---+ -t : "====+-=-: ::-+= ... --.. -. L. - :::.:;:.r--=~-,: : : _ ;_ ... : ::: -------. ---:..~. --_ ,_ -, :_;_~"f-,-. Figure A-6 Water level record of tidal heights at Yal-Ku Lagoon, 13-i6 December 1997

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: ..... ,, 1--r----f u ...I -1,~ -;,, -1 --.---...,.---.... ---t-..,.....-r-r-, _ ,_-_-_-..-_ _,,4-_'-l;~.,,-A--;.----,-Scale I < N _]-1 -r--291 ,..,...._. ..... -...:.----~-----I----r-~ . ::.... :: _,._____. ____ :. ; .. ---~--r:;::.-~::E ~..;;.:::-,..: -~:;.::....:: :==-::f~::: ~ -. .. :-~...:rh:.:: r--r-~---...,. .. f" : _.:::_~-:-:::. T-!:.::;::: . ,_. ._ .. --. ... ...,... --,....,....+-t--1--r-+-----,---r---,--,-~ r ->--Figure A-7 Water level record of tidal heights at Yal-Ku Lagoon, 16-17 December 1997. .

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,-. ... . -:..J...-... 1---+ -;----~ -~--: ~.-~ Scale ------ga -f-292 .:.:------. ---1--=== --~ -~-=---t _ --:= -, -_-+;_----l_.__::::-:::-:~~ -I-_ _;_. ~ --, . t. -.. --I'.-,---..... 7 : .... ~ -::::.: : ::-:.:-:. : : : : : ~ : : : : : : : ... ::-r:-.:-. ::. : _:-:.i . .. : : . : :: : :-. : ___ : : :;-r. :.: ~: --=... : ~ --=--;_~--~ -=~ : :~: ~ 1 : ==-::~~~-: ~ : ::_:: --. . --,--~ -----L------.;_1--,._ ===f .. -. ---. -. : .:.= .-: -:3=-= ~-_-.1--=-r--=---:::-.l-~--:--_-'~..+-__ .;._.:.:. _ --== --~~~-!: ___ --~ ft: : ~ ::; ... --:. -~==---::-.:.:.. .. ::~ _ : : .... ::. +----1---.:...:... --_. _:_~,-. _ -------~~--._--__ :--~ ----~ -_:.: 1-_ ,__ ---. 1--__ _.,. ----------= i-,---r--_,.. --,-. : : ~!'-~-::-~----... :-!t _:r-------..: i ----r------,-------~ ------t--: -: -: .:::-:-::. ::t:~::-=:: = t :'." -=-== ... -+1:t:.:-______ +-1..:.-___ _;__;.;.+-:.;~;.:.i-:=-.;:=f.:....~ -+:::...;: +-==~+.=, .:::..=:::::f=-=:::;:.:: ~ .:.:.;.!..;:.-::~:.;-:~_.;._;_:C l:.::::7:::_ :-:: :: T:::: : : .. : _~.-. = __ :-_~_-~_: -_-: : : -::!I...,....::= =r-..~ ;,: ; : .. -_-. -_: :_;=~ --,-. -: = ::::::-;-: o J ~ = -:-_-_-:-= IN:~.=-~-=-:~=~ :~~.: . -=:;i:\.....:_,..... -1.1 ----.---t--.._:---::.= ~ "'~ -. . . -r----._..__ ::;;a .. --L-. ~::_,.,,,._ .. ~----....... -n..(,~ -... ----t : ~ ~:: 1.::~>--___ ---11-~-..--,._ --1--------r-. ... .... >-~-.. -~---L-, ----.. ~ ~--:.~1: ~ r-, ~ -'r. ---r--.... L.-------'--,,, ~ ~-izt't:L: -t-T--Figure A-8 Water level record of tidal heights at Yal-Ku Lagoon, 17-19 December 1997.

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Scale -+--. -t----r--~:... .... ...... :..:i . .,-. -: ... ,.~-::i :. : ::_---r293 --~-+ --t-----~~~ .. : : : --: _,___ r---=i .. : --r-,----I 1 ..::------~ --i -~::?: : ~ : : ,_;_ .. -!l.f . _:~ : : -r ,-_ _:.t. ~ ---.---..:.:. i::~:-;~ ~~~=~=:::: I F I .,-:::-----,----t--;:,:;:::;.:; __,...-,. -i--__,_, .. ,~. ---.... --r-,.. .. .., r-,_r: -: ::~ ;-._ _, : 1 -; I : I:;> i i : J .. ;..,-:q:::. r :.;:: : ... ,:,-:: :~ 1-:: .-r--~: ~ -~-~;:.:.., : . : .. --~ :::. :..., __ ,...;:__,;_ _.. -~-r -r 'Tl.,,,_,'. ----::::f -==r:=. _____ -:i_ .::. i --. . ~:::-... .-: ::::--~ ,-----t-_:;-: .. . -., -; ---:::\: . 1 ~ --= _==; ____ .. ----. --. ---.-.... ... :;:: -= :::-: . ... -. ~-=-. :: ____ -~\-:f : r-r--_.. .... .... ::-:-+-': ,-~--,---....:= r -~ -7",r ::!= '. ::!:::-:.t::-:~:;:= T:;:;.:.::. i --,. 'f' I I o I ~-~;+:' ~ --;:;::;:,-~--== :.. .. --: :_ ,-. -----,-. -. ,--_ -_ __ ... ~ --... --------~ ~-. -:: -=-~~ -::;.=-=t::.=:. : -:.::___,...= 12/ z v Figure A-9 Water level record of tidal heights at Yal-Ku Lagoon, 19-22 December 1997

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=-=-I~ :.==~-}~ -----------:--=--====,_-_ -_: ~~\~~---_-_-_::-_::-_---:-;__ -_~---_::-_::-_-_-_-_-_-_-_-_-_-_::-_ _-_::-_-_-_-_-_ _-~ ~ :4=~ ,_{;=:. I: ~~ ~, f-:'.-'H ,.._ __ I :L ,._,.-t_i. ~ -_ ,.,.tf--,,,-r--c,-, -Y-------,----_ i "-: ,294 v-. l--------+-1---1-------------+-+---+--l_j__ -------+-t---l---i----------+------"--1---1----lf-l---, ---+ !I i---------.--11-----+----'-------+--lr---'-+---+-+----'l----t-t---r---t---t--:-t-'li, . Scale .-:.. ,. I ------= :=-==-=========--=--=-t-=--=--=----_-_-_-___-_-:_-_-_: ~j ,-~ l _-_ -_ -_ -_ --.L~ -_ _ -_ -_ :::._ ::: ____ -_ -_ -_ -__ _ ,-_--+----;__-+,-~--'-------f---'--Figure A-10 Water le v el record for cenote near wetiand treatment unit, 10-14 December 1997.

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~=====:::::::=:::; Scale 1-~---lf-----+---------t----t---;---11~ -,. V -:,- /i. .,-i295 ,. ,n 7 +---~-~J--1111r-_-r-t-_-_-_ ~--,)--v ?It~~ V ;;A~ Figure A-11 Water level record for cenote near wetland treatment unit, 14-17 December 1997.

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--~ ----. .... -L;-l}Tl u ,.,,;; _ nil"~ Scale :_.a .. '" 296 ,; ; -J l ,..., IL rot"======== Figure A-12 Water level record for cenote near wetland treatment unit, 17-20 December 1997

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_____________ __.._ ._____-._____ ,I -" t:=== == == Scale I I ------------------------------------297 ---.. ---.........---. N -::.,.........., .. ~-,:a..:_ I' I' ----1' --Figure A-13 Water level record for mangrove near wetland treatment unit, 9-14 December 1997

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.. '. ~ Scale 298 L "'"" .. -I I ._: ~ Figure A-14 Water level record for mangrove near wetland treatment unit, 14-17 December 1997. --I ~----,_,_!..J

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I = Scale I : 299 ,.._ .-,.-,, Figure A-15 Water level record for mangrove near wetland treatment unit, 17-20 December 1997.

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---~--'-~ Scale 300 .,--+, 1 I Figure A-16 Water level record for mangrove near wetland treatment unit, 18-21 July 1997 :s. ...

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301 :--~---~-----------------,-------+---------t---------.-------r--~--:-:-t----~------+-------------+-------l--------+-------r----~---r-~--t--L ,-.=-------+------t----~-----'-----f----.;----...;...-;I' 1---"-',._, _____ --t---'--'------+------------'-t-.,.---,f----+----+---'---. ~ -----.--\" ii:: ;.=t------------"'--,------------""'..., .... -_--:.--:.-:.-:.-:.::.:::'....'"""~-,--: ~-t---_-_-_-_-_-_-_--:._-_-_-_.,'t:ic"H"!---_-_-_-_-_-_-_--:_-_-_-_-_-_-_-_-_-_-_-_-..,-_...,_.,._--:._-_-_-_-_-_-_-_--.~'-'--_-_-_-_--:._-_-.. -_-_-_--;_r_-_-_-_--:._-_-_-_-_-_-_-_-_ ... _-_--:._-_-_-_-_---l+_-_-_-_--'-_-_'----'-+_1---;,+--'-''-----_-_-_---l+_-_--'_":_,..lt-----_-_-_-_-_-_-_-_--:._-_-+t----'---~----_-_--'-~--I+_-_-_-_-_-_---:: l )-"I J--,1-------i--;,------,---~-------1---, l--,~0----------,-----+-----,----+---+--------'--t------_,,.___ =-~--------= Scale -----i--~-----_ -_-_-_-_+.,.-_-_-_ -_-_ -_ ~ -"----~~------~+---_-_-_-..= -_ -++ -_ -_ -_ -_ -_ -_ -_ ---1..r-'---_ -_ -_ -_ -_ -_ -_ "'"+ -_ -_ -_ -_ -~--_ -.., -_ -_ -_ -_ -_ -_ -..., --t-1--_ -_-_-rt---1_.;_ --~--++ -_ -_ -_ -_ -_ -_ -_ --t-t---_ -_ ----;--_ -_-_ -.,.---_-_ --"~;;;= r.::::::::::====== -~t ...... ~---Figure A-17 Water level record for mangrove near wetland treatment unit, 22-25 July 1997.

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L1; .,,. .. ----::=====;:===;== :::-===.:::-====: Scale "\~ ~ ......... 302 ..... ...... ,, ---"'Figure A-18 Water level record for mangrove near wetland treatment unit,.25-28 July 1997.

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.. I I '--t ___ S I I I ---_: .--.-.I. j-1 ---!---... _____ _! _ 'i I I .., ... 1 __ . _ : I. <" I I lf . .. : --. I C I --. I i I i I -I . : . I I i I ,.! I I ---~! :::-I : I : : I -: I I -1' . : : . .: I i !I I ... I I I; i I I I -i i 8 _ .:.j .c,_ (mi i :.Lf -. ---2. I i 303 I I : I i :_: I : I i I I I ----?---~---i ?...J.f~r s -~ale ' : I:.'. -----..:. -~-'. ~i t: ~i.: .: .. __ :j; ___ :_l ,1 ., : : i;'. i : I i I I I I i I I 6 ~1 .. 1 -I '2 . --. .. l--. i -. t..r t j 1 :ir: I (\. J() -~~ 1--: .. 1 .. l -~l\ t i --; : I L~~ J ~ lt_. '.l ~:. -~:_ __ -_~1 ..... i 1 I I I ~-! I I -I' I I ! ., ; I-: ''f i;-;~ I I i .. i I. I I -.. I I.: --~ I I .. :_, l i ... --1 I i i I ~ .. Figure A-19 Water level record of tidal heights at Yal-Ku Lagoon, 24 July1 August 1997

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APPENDIXB NOTES AND TABLES FOR WATER BUDGET SIMULATION MODEL Notes on literature values used to estimate storage values and pathway flows in the water budget simulation model:. 1. Tides. Tidal range is typically 15-20 cm during full moons with a high of 40 cm and a low of 6 cm observed in the last two years (Shaw pers. comm ) For Puerto Moreles 80 km further north up the coast average tidal height is 18.1 cm (Ibarra and Davalos, 1991) 2. Rainfall. Average monthly rainfall at Tulum a coastal town 20 km further south of Akumal (Viquiera et al 1994) is presented in Table B-1. Average rain per day is 3.02 mm. 3 Potential evapotranspiration (PET). Potential evapotranspiration (PET) measured at Tulum between 1983-1996 (SARH 1997) totals 1450 mm and is shown in Table B-2 Average yearly evapotranspiration has been estimated to total 900 mm. Average daily PET is 3.99 mm and average daily evapotranspiration = 900 / 365 = 2.47 mm. 4 Relative humidity / temperature / saturated and air vapor pressure Table B-3 shows relative humidity temperature data for the Yucatan coast. Average monthly relative humidity for the area according to governmental meteorological data from 1958-1980 ( cited in Ibarra and Davalos, 1991) shows little variance with March at 81 % the lowest and September at 88% being highest. Temperature is from Viquiera et al 1994 304

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305 for Tulum. Saturated vapor pressure is from temperature tables contained in Lee, 1978 and air vapor pressure is calculated from relative humidity and temperature monthly averages 5 Wind. Average wind velocity for the area is 5 m/sec. Table B-4 presents average monthly wind velocity (Ibarra and Davalos, 1991 ). 6 Inland freshwater groundwater flow Average groundwater flow was calculated (Back 1985) by dividing drainage area of 65,500 km2 by coastal length of 1,100 km Of the 8.6 E3 m3/ yr through each meter of the receiving wetland, Table B-5 presents estimates of monthly flow by correlation with monthly share of annual rainfall ( see note 2). Average daily groundwater flow= 8630/365 = 23 64 m3 and average monthly groundwater flow is 8630 /12 = 719 16 m3 In the simulation model, average monthly groundwater flow is taken as 0 30 above datum (1 meter below surface of mangrove, 0.32 m below mean sealevel) The low months (February-April) were taken as 0.2 m height of water in mangrove, and top month (May) as 0.6.Therefore, following gives monthly values, expressed in height (m) of water in mangrove m2 : January 0 254 February 0 2, March 0 2, April 0 2, May 0 6 June 0.47, July 0 29, August 0.33, September 0.47 October 0.44 November 0 22 and December 0.21. 7 Solar insolation. The value for solar insolation used by Odum et al (1986) for the Amazon is 140 Kcal/cm2/ yr or 3835 Kcal/m2/day, with presumably higher cloud interference with solar radiation Brown et al (1992) use 180 Kcal/cm2 / yr for Nayarit (World Energy Data Sheet) or 4932 Kcal/m2/ yr From Sellers (1965) diagram

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306 relating latitude to average yearly solar radiation at 20 deg N latitude gives 110 kilo langley / cm 2 / yr = 110 Kca l/ cm 2/ yr = 3013 Kca l/ m 2 / day 8. Mangrove primary productivity and biomass Productivity in mangrove swamps varies greatly and several characteristic ecosystem types have been traditionally identified. Riverine mangroves are the most productive followed by fringing mangrove areas and basin mangroves (Table B-6) Less productive are hummock mangroves growing in unfavorable locations Lugo and Brinson (1979) reviewed the literature and gave data on net primary productivity (NPP) of these mangrove types in Florida Using an average value of 1.5% N for mangrove plant tissue we have translated their numbers into average annual N assimilation by mangroves which shows that Nedwell et al s productivity calculation places their mangrove system as intermediate between riverine and fringing in N-uptake Cintron et al (1985) (cited i n Mitsch and Gosselinke 1993 ) give a range of biomass of 0 8 -15. 9 kg/m 2 for fringe mangroves and 1.6 28 7 kg/m 2 for basin mangroves We can use an average figure of 16 kg/m 2 for this model. 9 Primary productivity and biomass of treatment wetland unit. Richardson (1979 ) estimates net primary productivity in freshwater marshes as follows : Typha wetlands : 2740 670 grams of organic matter ( m 2)-L yr -2 ; reed wetlands (Phragmit es c ommuni s, Scirpu s spp., Jun c u s effus u s, Cy p e ru s papyru s ) 2100 580 grams of organic matter (m2)-1 yr-2 and freshwater tidal marshes (P e ltandra virginica A corus c alamus Zi z ania aquati c a): 1600 200 grams of organic matter (m 2y1 y(2 T hese three data average 2154 grams of organic matter (m 2r1 yr -2 or 5.9 g (m 2r1 daf2 Total biomass

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307 estimates for tidal marshes range from 0 .145 -0 725 kg/m2 for a freshwater tidal marsh (Simpson et al 1983 cited in Mitsch and Gosselink 1994) to estimates for peak standing crop of the salt marsh species Spartina a/temiflora of 0 754 -0 903 kg/m2 (Hopkinson et al 1980 and Kaswadji et al 1990 cited in Mitsch and Gosselink, 1994) which probably comprise 20-30% of total biomass and 6 55 kg/m2 for total above and belowground biomass in a Louisiana salt marsh (Buresh et al., 1980 cited in Day et al 1989). We can use 6 kg/m2 as an estimate for the treatment wetland unit's biomass since they include larger tree and palm species as well as wetland grasses and shrubs 10 Wastewater inputs. At design loading, for the 81.6 m2 wetland, inputs are 24 people x 0.115 cum/day= 2 76 m3/ day / 81.2 m2 or 0 034 m/day Our model will use 0 34 m/day wastewater input for October April and in the off-tourist months of May September a loading of 0 22 m/day

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308 Table B-1 Average monthly rainfall at Tulum, 20 km south of study site Month Rainfall mm ...................... January 77 9 February 41.3 March 42 3 April 41.2 May 166 6 June 143. 3 July 88.1 August 101.1 September 149 7 October 140 9 November 74 7 December 57.0 Total : 1 104.1 (Viquiera et al, 1994).

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309 Table B-2 Measured evaporation at Tulum 20 km south of study site along the Yucatan coast. Actual evapotranspiration is estimated at 900 mm for the Yucatan The last column is a calculation of evapotranspiration based on the percentage of yearly evaporation that occurs in each month .. Month Average monthly potential Percentage of Monthly evapotranspiration, mm. Yearly ET, evapotranspiration % if year total is 900 mm January 89 2 6.1 54.9 February 102.5 7 0 63.0 March 129 9 8 9 80. 1 April 148 1 10 2 91.8 May 142.1 9 8 88 2 June 141.9 9 8 88. 2 July 150 8 10.4 93 6 August 144 1 9 9 89 1 September 125.9 8 7 78 3 October 101.8 7 0 63.0 November 94.5 6 5 58.5 December 83.8 5 7 51.3 1454 6 { Tota Q 100 900 0 (SARR, 1997)

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310 Table B-3 Average monthly relative humidity temperature and air vapor pressure calculated for the given temperature and relative humidity for the Yucatan coast. Month Average Temperature Saturated vapor Air vapor relative degrees C. pressure at monthly pressure humidity average temp ., mb at average percent relative humidity and temp for month mb January 84 23 3 28 .61 24 03 February 83 23. 5 28 96 24 04 March 81 24 7 31.12 25 .21 April 81 25.5 32.64 26.44 May 82 25 8 33 22 27 24 June 85 26 2 34 02 28 92 July 86 26 0 33.61 28 90 August 86 26.0 33 .61 28 90 September 88 25.0 31.67 27.87 October 87 24.9 31.49 27.39 November 84 24.8 31.31 26 30 December 85 23. 1 28 26 24.02 Average 84 24 9 31.49 26.45 (Ibarra and Davalos 1991, Viquiera et al 1994 Less 1978 )

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311 Table B-4 Average wind vel~ity, measured at Puerto Moreles Mexico 80 km north of study site Month Average wind velocity meters / second -.. January 5 0 February 6 6 March 4 3 April 4.4 May 5.6 June 5.4 July 4 5 August 3 6 September 4.1 October 4.4 November 5 9 December 6 7 Avera s e 5 0 (Ibarra and Davalos 1991 )

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312 Table B-5 Estimates of monthly groundwater flow based on data and average monthly rainfall in the Yucatan. Month Share of annual rainfall Groundwater flow per Decimal s~uare meter of mangrove wetland m / rn/yr -January 0 .07 604 1 February 0 04 345.2 March 0 04 345.2 April 0 04 345.2 May 0 .15 1294 5 June 0 .13 1121.9 Jul y 0 08 690.4 August 0 09 776.7 September 0.13 1121.9 October 0 12 103 5 6 November 0 06 517 8 December 0 05 431.5 Total 100 8630 Back (1985)

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313 Table B-6 Net primary productivity (NPP) in mangrove ecosystems. Mangrove System NPP grams organic matter / m2/ day .. P-~-n -- - "" Riverine 12. 6 Basin 5 6 Fringe 2 9 Hummock 2.6 Average 5 .85 (Lugo and Brinson 1979). NPP perr,_ (gOM/m / yr) 4600 2044 1059 949 2163

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APPENDIXC COMPARISON WITH UNIVERSITY OF FLORIDA SEWAGE TREATMENT FACILITY Table D-1 presents an emergy evaluation of the University ofFlorida Water Reclamation Facility The University of Florida Water Reclamation Facility is an activated sludge wastewater plant similar to those used in many cities in the United States and Europe It includes primary treatment with screens and grit chambers for removal of large particles followed by alternating treatment in anaerobic and aerobic basins Clarification, settling tanks allow sludge to settle and be removed. Effluent water is filtered and treated with chlorine for sterilization Disposal is via groundwater injection (84%) use in air-conditioner cooling towers (8%) and use in campus irrigation (4%) Wastewater flow totals about 2 million gallons per day for a population of about 40 000. This amounts to 50 gallons per person, however, since most of the population do not live on-campus wastewater generation is even higher. If assumed to be equivalent to a full-time residence for 20 000 people wastewater flow is around 100 gallons/person Capital investment for the University of Florida treatment plant was around $11.2 million The University of Florida system is dependent on the use of much electricity (even ignoring electricity used to pump to the facility) and uses 4 1 E6 kilowatt-hours annually to operate the mechanical aerators grinders, and pumps Chemicals are also used: alum for coagulation chlorine for disinfection. Freshwater totaling 7 3 million 314

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315 gallons / year is used at the University of Florida facility for disinfection and general plant operations Emergy analysis of the University of Florida treatment plant (Table 5-1) shows that > 99% of resources are non-renewable (raw wastewater) and purchased goods are 0 5% and services 0 1 % Renewable resources contribute less than 0 001 % of emergy inputs. The purchased / renewable ratio is 220 for the University of Florida facility (220 times as much purchased inputs as renewable resource emergy inputs) Emergy required per person is 314 E 14 / person. Empower density ( energy per area per time) is 14 .3 E20 sej/ha/yr. for the University of Florida system.

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316 Table C-1 Emergy analysis of the University of Florida sewage treatment facility Note Item Data EMERGY / unit SOLAR Em$* (sej/unit) EMERGY ----_ (x E17 sej) Renewable Resources 1 Sunlight 2 6 E13 J / yr 1 < 0 001 19 2 Wind 2.53 E13 J /yr 663 sej/J 0 .18 12, 244 Subtotal 0 .18 12, 244 Non-renewable resources 3 Raw sewage 714 1 E6 8.76 Ell 6256 456 644,230 gallons/yr sej / gallon Purchased Goods 4 Electricity 1.18 E13 J/yr 173681 sej/J 20.49 1 825 552 5 Fuel 1.52 El 1 J /yr 6.6 E4 sej / J 0 .11 7 308 6 Water 1.36 Ell J/yr 665714 sej / J 0.91 66,085 7 Chlorine 6.37 El 1 J/yr 39800 sej / J 0.25 18, 514 8 Capital Costs $546 750 1.37 El2 sej / $ 7.49 546 750 9 Maintenance $365 000 1.37 E12 sej/$ 5.00 365 000 (Goods) Subtotal 34 .34 2 829 209 Purchased Goods 10 Operating and Services Maintenance $385 118 1.37 E12 sej / $ 5 28 385 118 Total 6295.8 124 174 853 11 Yield Treated sewage 13. 36 E13 4 71 E6 sej/J 6295 8 124 174 853 J I *Based on 1.37 EI2 sej / $ 1993 values (Odum, 1996, p. 314) Sunlight received in Gainesville Florida with albedo estimated at 10% x 44 ha (size of sewage facility): (1.58 x 1 OE6 kcal/sq m/yr) (.90)(1 x 10 E4 sq m/ha) (4186 J/kcal) (0.44ha) = 2.62E 13 or 0 262E 14 J /yr (Odum 1996, p 114) 2 Based on method given in Odum, 1996 p 294 with values of eddy diffusion and vertical gradient from Tampa, Florida and using wind of 10 m height as relevant for re

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317 Table C-1 continued aeration of microbial reactor tanks of facility: (10 m)(I. 23 kg/cum) (2. 8 cu m/m/sec) (3. 154E7 sec/yr) (2 3 m/sec /m)E2 (4400 sq m) = 2.53 EI3 J /yr Transformity for wind from Odum, 1996 p. 186 3 Yearly inputs of raw sewage : 714 1 E6 gallons Transformity based on emergy needed to sustain people in Florida : 32 El5 sej/yr (Odum et al 1998) divided by yearly outputs of wastewater per person = 100 gallons/day *365 days = (3 65E4 gallons) 32 El5 sej /yr / 3.65 E4 gallons = 8 .76 El 1 sej / gallon 4 Electricity chemical potential : (3, 291 300)60 kWh/yr) (3.6E6 J/kWh) = 1. 1 8EI3 J /yr (Odum, 1996 p 300) Mean transformity for electricity (Odum, 1996 p 305) 5 Fuel chemical potential based on P Green, 1992 p 27: (1000 gal/yr) (3 7 Ugal) (41 J/L) = 1. 5 2Ell J /yr Fuel transformity based on calculation of Slesser 1978 cited in Odum, 1996 p '308 6 Water Chemical Potential Energy : 4940 J/kg given in Odum, 1996 p 120 density of water at 20 deg C = 998 2 kg/ cum (Kraut, Fluid Mechanics for Technicians 1992 p. 365 ; (7 296 700 gal/yr) (1 cu in/ 264 gal) (4940 J/kg) (998.2 kg/cum) = 1.36EI I J /yr Transformity of water from Brown and Arding 1991 Transformity Working Paper 7 Chlorine : (7E6 kcal/ton) (4186 J/kcal) (21.75 tons/yr) = 6.37EI 1 J /yr and the transformity of coal (Odum 1996 p 194) 8 Capital Costs: Facility excluding the sludge drying component $10 935 000 / 20 yrs lifetime = $546 750 x 1.37E l2 sej/$ = 749 05EI7

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318 Table C-1 continued 9 Maintenance (goods) $365 000 1.37 El2 sej/$ = 749.05 El 7 1 0 Operation : labor costs: $385 118 / yr x l.37EI2 sej/$ = 527 .61 E 17 sej 11 Discharge of treated wastewater: 714 1 E6 gallons / yr Chemical potential of wastewater : 714 1E6 gal* 1 cu m/264 gal* 10E6 g/cu m 4 94 J i g = B.36 EB J Transformity of treated wastewater: 6295 .8 El 7 sej I 13. 36 EB J = 4.71 E6 sej/J

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BIOGRAPHICAL SKETCH Mark Nelson was born 29 May 1947 in Brooklyn, New York and was educated at Dartmouth College where he graduated Summa Cum Laude in 1968, with high honors in philosophy and was elected a member of Phi Beta Kappa His M.S. degree (1995) is from the University of Arizona s School of Renewable Natural Resources Tucson A founding director and currently Chairman and C.E.O of the Institute of Ecotechnics London Mark has worked in demonstration ecological projects in the United States and Australia for over two decades His research interests includes pasture improvement and regeneration of tropical savannah ecology, high desert orchardry and silvicultural systems, ecological engineering and closed ecological systems Mark served as director of Environmental and Space Applications for the Biosphere 2 project in Oracle AZ from 1985-1994 He was a member of the eight-person biospherian crew that operated and researched Biosphere 2 during its first two year closure experiment 19911993 He is currently a Contributing Editor for the journal Life Support and Biosphere Science. As Vice President for Wastewater Recycling Systems for Planetary Coral Reef Foundation he has designed and implemented constructed wetland systems in Mexico Bali and the United States He is also a director of Eco-Frontiers Inc. which owns and manages projects in a number of challenging environments around the world. 330

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I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy ~f1~ Howard T Odum, Chairman Graduate Research Professor of Environmental Engineering Sciences I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philos1 Mark'T.Brown, Co-chairman Assistant Professor of Environmental Engineering Sciences I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality as a dissertation for the degree of Doctor of Philoso hy of Environmental Engineering Sciences I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality as a dissertation for the degree of Doctor of Phi losop}'\ '. ~Kj~~~~2:::=9 =====--Konda R. Reddy Graduate Research Professor of Soil and Water Science I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality asadissertationforthedegreeofDoctorh~0 4,, o, --~ Daniel P. Spangler Associate Professor of Geology This dissertation was submitted to the Graduate Faculty of the College of Engineering and to the Graduate School and was accepted as partial fulfillment of the requirements for the degree of Doctor of Philosophy

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December 1998 t--< Winfred M Phillips Dean College of Engineering M.J Ohanian Dean Graduate School

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