• TABLE OF CONTENTS
HIDE
 Title Page
 Acknowledgement
 Table of Contents
 List of Tables
 List of Figures
 Executive summary
 Introduction
 Methods
 Results
 Ability of the marsh to assimilate...
 Summary and conclusion
 Appendix
 Bibliography














Title: Final report to City of Clermont, Florida Removal of nutrients from treated municipal wastewater by freshwater marshes,
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Permanent Link: http://ufdc.ufl.edu/UF00017054/00001
 Material Information
Title: Final report to City of Clermont, Florida Removal of nutrients from treated municipal wastewater by freshwater marshes,
Physical Description: Book
Language: English
Creator: Zoltek, John Jr.
Bayley, Suzanne E.
Hermann, Albert J.
Tortora, Louis R.
Dolan, Thomas J.
Graetz, Donald A.
Erickson, Nancy L.
Publisher: Center for Wetlands, University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: October 1979
 Record Information
Bibliographic ID: UF00017054
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltqf - AAA9716

Table of Contents
    Title Page
        Page i
        Page ii
    Acknowledgement
        Page iii
        Page iv
    Table of Contents
        Page v
        Page vi
        Page vii
        Page viii
    List of Tables
        Page ix
        Page x
        Page xi
        Page xii
        Page xiii
        Page xiv
    List of Figures
        Page xv
        Page xvi
        Page xvii
        Page xviii
        Page xix
        Page xx
        Page xxi
        Page xxii
    Executive summary
        Page 1
        Page 1a
        Page 2
        Page 3
        Page 4
    Introduction
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
    Methods
        Page 13
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        Page 15
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    Results
        Page 48
        Page 49
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    Ability of the marsh to assimilate phosphorus and nitrogen from secondarily treated wastewater
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    Summary and conclusion
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    Appendix
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    Bibliography
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Full Text








FINAL REPORT


TO
CITY OF CLERMONT
FLORIDA



REMOVAL OF NUTRIENTS FROM TREATED MUNICIPAL
WASTEWATER BY FRESHWATER MARSHES



JOHN ZOLTEK, JR. AND SUZANNE E. BAYLEY, PRINCIPAL INVESTIGATORS
ALBERT J. HERMANN, Louis R. TORTORA, AND THOMAS J. DOLAN
GRADUATE RESEARCH STUDENTS
WITH CONTRIBUTIONS FROM
DONALD A. GRAETZ AND NANCY L. ERICKSON
SOILS SCIENCE DEPARTMENT




CENTER FOR WETLANDS
UNIVERSITY OF FLORIDA
GAINESVILLE, FLORIDA 32611


OCTOBER 1979




ACKNOWLEDGMENTS
We express special appreciation to Linda Hoffman and Erik Melear
for their invaluable laboratory analyses. Field and laboratory
assistance was provided by Robert Tatum, Gary Goforth, Peter Straub,
Brian Kramer, Richard Wallace, Patricia Welsh, Angelo Masullo,
Glenn Schuster, Alex Procho, Frances Larusso, and Charles Hucks. In
Clermont, William (Bill) Daily,, Preston Davies,: and the city of
Clermont's sewage treatment plant personnel gave essential support in
field operations.
Typing was done by Nancy Steele, Joan Breeze, and Ann Stokes.
Bruce Heinley was the draftsman.
The research was supported by joint funds form the city of
Clermont, the Lake County Board of Commissioners, and the Lake County
Water Authority. The prisoners of the Lake County Correctional
Institute provided labor during the site construction.
Claude Smoak, the mayor of the city of Clermont, was
responsible more than any individual for the inception of this
project. His constant support throughout the study was invaluable
and greatly appreciated.
iii





CONTENTS
LIST OF TABLES................. ..................... ............... ix
LIST OF FIGURES ........................... ......................... xv
EXECUTIVE SUMMARY ................................. ................. 1
INTRODUCTION...................................................... 5
Overview ....................................................... 5
Project Objective ............................................. 8
Description of Study Area............. .......................... .. 8
Marsh Vegetation and Substrate................................. 10
METHODS............................................................ 13
Experimental Plots............................................. 13
Water Chemistry ................................................ 17
Hydrologic Measurements ....................... ................ 20
Specific Yields............................................ 18
Evapotranspiration ......................................... 20
Outflow........................................................... 25
Distribution of Applied Water.............................. 26
Plant Community Measurements ................................... 28
Biomass Measurements ....................................... 28
Decomposition Measurements ................................. 31
Peat Soil Measurements......................................... 36
Nitrification and Denitrification Studies...................... 39
Preliminary Nitrification Studies in Marsh................. 39
Preliminary Denitrification Studies.......... .................. 41
Nitrification and Denitrification Using
Soil:Water Columns ..................................... 41
Ammonia Volatilization Study .............................. 43
In Situ Nitrification and Denitrification Studies.......... 44
Microbial Studies: Total, Nitrifying, and Denitrifying
Populations ............................................ 45
Analytical Methods for Nitrification-Denitrification Study. 46
RESULTS ............................................................ 48
Characteristics of the Peat Soil............................... 48
Moisture Content, Organic Matter Content and Bulk Density.. 48
Specific Yield ............................................. 50
Hydrologic Considerations ...................................... 54
Seasonal Water Table Fluctuations and Hydrologic Inputs.... 54
Water table elevations ............................... .. 54
Hydrologic inputs ...................................... 54
v





Evapotranspiration ......................................... 59
Evapotranspiration from the research marsh ............59
Model of evapotranspiration ...... ......................61
Water Storage and the Distribution of the Applied
Treated wastewater .....................................65
Water storage .......................................... 65
Distribution of treated wastewater within the plot.....69
Hydrologic Budgets for the Control Plot, High Rate Treated
Wastewater Plot, and the "Average" Marsh ...............81
Plant Production ...............................................88
Live and Dead Aboveground Standing Crop ....................88
Belowground Standing Crop..... .............................93
Net Production ....... ........................ ..............99
Phosphorus Considerations.....................................101
Phosphorus Water Values ................................. 101
Phosphorus Aboveground Vegetation Values ..................119
Phosphorus Belowground Vegetation Values ..................129
Phosphorus in Peat Soil ....................................131
Peat Soil Adsorption Studies..............................137
Dry Year Plant Decomposition and Phosphorus...............143
Phosphorus Budget for Plots H and C...........................147
Treated Wastewater Phosphorus Loading.....................147
Rainfall Phosphorus Loading ...............................152
Outflow of Phosphorus from Plots H and C... ...............152
Dry Year Budget ...........................................158
Wet Year Budget ..............................................161
Nitrogen Considerations ....................................... 164
Model of Microbial Transformations of Nitrogen ............164
Nitrification ............................... .............167
Laboratory experiments ................................167
In situ investigations ................................185
Denitrification ........... o..............................191
Laboratory experiments ............ .......................191
In situ investigations ...............................200
Nitrogen Fixation .........................................206
Nitrogen Water Values .............. .....................207
Belowground nitrogen water values .....................207
Aboveground nitrogen water values .....................233
Nitrogen Vegetation Values................................241
Nitrogen aboveground vegetation values ...............241
Nitrogen belowground vegetation values ................246
Nitrogen vegetation summary...........................249
Nitrogen in Peat ...................... ...................252
Plant Decomposition and Nitrogen ..........................258
Nitrogen Budget for Plots H and C ..............................265
Treated Wastewater Nitrogen Loading .........................265
Freshwater Nitrogen Loading ...............................265
Rainfall Nitrogen Loading.. ..................................265
Nitrogen Fixation.........................................270
Changes in Aboveground Biomass Nitrogen....................270
Changes in Belowground Biomass Nitrogen...... ................ 273
vi





Nitrogen Adsorption by Soil ...............................273
Potential Denitrification ...... ..........................273
Export of Nitrogen in Outflowing Water ....................275
Total Organic Carbon, Suspended Solids and
Pathogenic Quality .................... .......................292
Total Organic Carbon .................................................292
Suspended Solids ..........................................292
Pathogenic Quality ........................................293
ABILITY OF THE MARSH TO ASSIMILATE PHOSPHORUS AND
NITROGEN FROM SECONDARILY TREATED WASTEWATER ..................296
Comparison with Other Research...... .. ...... ..........................296
Model of the Study System ..... .................................. 297
General Considerations.......... .................................297
Loading Rate.................................................... 297
Application System .. .... ......... .........................303
Fluctuating Water Table .... ........ .........................304
Prototype Marsh Similarities as Compared to
the Experimental Marsh.....................................305
Nutrient Export ........................................... 306
SUMMARY AND CONCLUSIONS .......................... .................307
APPEND IX .............................................313
BIBLIOGRAPHY ......................................................319
vii





LIST OF TABLES
Table Page
1 Dominant marsh plants of the research area. 11
2 Summary of sampling dates for biomass, water 32
samples, peat soil, litter bags, water level,
and rainfall in the marsh.
3 Three physical characteristics of the peat 49
soil: moisture content, weight loss on igni-
tion, and bulk density.
4 Representative specific yield values for Plots 53
C and H.
5 Historical monthly rainfall averages for north 58
central Florida, observed rainfall in north
central Florida, and observed rainfall in the
research marsh.
6 Quantities of treated wastewater and fresh 60
water applied to the experimental plots.
7 Empirical estimates of monthly evapotranspira- 62
tion rates in the marsh.
8 Estimates of average daily evapotranspiration. 64
9 Estimated evapotransporation in Plot C (4.4 66
cm/wk fresh water) and Plot H (9.6 cm/wk
treated wastewater).
10 Monthly changes in water storage in the peat of 67
Plot H (9.6 cm/wk treated wastewater).
11 Average concentrations of chloride in medium 78
depth wells of the experimental plots and the
natural marsh (1/78-12/78).
12 Estimated mass inflows and outflows of chloride 79
in Plots C and H (1/78-12/78).
13 Average concentrations of chloride ion in sur- 80
face samples from Plot C, Plot H, and the nat-
ural area (8/78-5/79).
ix





Tablel- Page
14 Hydrologic budget for Plot C (4.4 cm/wk fresh 81
water).
15 Hydrologic budget for Plot H (9.6 cm/wk). 84
16 Hydrologic budget for the average marsh. 86
17 Summary of two years of hydrologic data from 87
May 1977 through April 1979.
18 Belowground live plus dead biomass. 98
19 Net annual aboveground production of plots. 100
20 Total phosphorus removal efficiencies for wells 105
located in Plots H, M, and L.
21 Chlorophyll-a results for Plots H, M, L, and C 117
(9.6, 3.7, and 1.5 cm/wk of treated wastewater
and 4.4 cm/wk of fresh water, respectively),
and the undisturbed natural marsh.
22 Phosphorus content of marsh vegetation in Plot 120
H (9.6 cm/wk).
23 Phosphorus content of marsh vegetation in Plot 121
C (4.4 cm/wk).
24 Phosphorus content of marsh vegetation in Plots 122
H and C (9.6 and 4.4 cm/wk).
25 Uptake of phosphorus by aboveground live vege- 125
station in Plot H.
26 Changes in phosphorus storage in aboveground 126
dead vegetation in Plot H.
27 Uptake of phosphorus in aboveground live 127
vegetation in Plot C.
28 Changes in phosphorus storage in aboveground 128
dead vegetation in Plot C.
29 Phosphorus uptake by roots in Plot H. 132
30 Phosphorus uptake by roots in Plot C. 133
31 Overall phosphorus content of soil samples 134
collected in March 1978, September 1978, and
February 1979 from Plots C, H, M, and an
undisturbed natural area.
x





Table Page
32 Uptake of phosphorus by the peat soil in the 136
natural marsh and Plots H and C.
33 Phosphorus adsorption study. 138
34 Estimated adsorption capacity as determined by 145
the Freundlich model.
35 Phosphorus loading rates for Plot H. 150
36 Phosphorus loading rates for Plot C. 151
37 Phosphorus loading from rainfall. 153
38 Outflow of phosphorus from Plot H. 155
39 Outflow of phosphorus from Plot C. 157
40 Phosphorus budget for the dry year for Plot H. 159
41 Phosphorus budget for the dry year for Plot C. 160
42 Phosphorus budget for Plot H for the wet year. 162
43 Phosphorus budget for Plot C for the wet year. 163
44 Ammonium, nitrate, dissolved oxygen, and pH 168
values measured in nonaerated and aerated marsh
water incubated in the laboratory without
soil.
45 Effect of charcoal filtration and inoculation 170
with soil water extract on nitrification in
marsh and lake waters without soil.
46 Ammonium removal rates in laboratory studies 181
using columns containing ammonium-amended
treated wastewater overlying 45 cm of peaty
marsh soil.
47 Ammonium concentration data in soil:water 183
columns of nitrification experiment.
48 Nitrate nitrogen concentration data in 181
soil:water columns of nitrification experiment.
49 Ammonium, nitrate, dissolved oxygen, pH, and 187
groundwater levels determined after in situ
incubation of soil samples in polyethylene
bags.
xi





Table Page
50 Total, nitrifying and denitrifying bacterial 190
populations in marsh soils obtained directly
from the marsh and in soils incubated in situ
in polyethylene bags for 27 days.
51 Nitrate removal from water alone and in contact 192
with soil, incubated in the laboratory.
52 Ammonium concentration data in soil:water 197
columns of denitrification experiment.
53 Nitrate nitrogen concentration data in 198
soil:water columns of denitrification experi-
ment.
54 Nitrate removal rates in laboratory studies 201
using columns containing nitrate-amended sewage
effluent overlying 45 cm of peaty marsh soil.
55 Ammonium, nitrate, dissolved oxygen, pH, and 202
groundwater levels determined after in situ
incubation of soil samples in polyethylene
bags.
56 Average yearly concentrations of nitrogen in 229
treated wastewater.
57 Average concentrations of nitrogen species for 231
the natural marsh and the northwest corner
medium-depth wells of Plots C, L, M, and H.
58 Average yearly concentrations of nitrogen 232
species for treated wastewater and medium-depth
wells W3M and W23M.
59 Average concentrations of nitrogen species in 239
surface waters of the natural marsh and the
inside and outside regions of the 4.4 cm/wk
fresh water (Plot C) and 9.6 cm/wk treated
wastewater (Plot H) plots.
60 Average concentrations of nitrogen species in 240
treated wastewater and Plot H surface stations
H-I and H-0.
61 Aboveground live biomass nitrogen storage for 242
the entire region of each plot.
62 Aboveground dead biomass nitrogen storage for 245
the entire region of each plot.
xii





Table Page
63 Aboveground live plus dead biomass nitrogen 247
storage for the entire region of each plot.
64 Belowground live plus dead biomass nitrogen 248
storage for the entire region of the plots.
65 Total nitrogen content of peat in the marsh. 256
66 Adsorbed ammonium in the peat complex. 257
67 Nitrogen loading to Plot H in applied treated 266
wastewater.
68 Average nitrogen content of fresh water applied 267
to Plot C.
69 Nitrogen loading in fresh water to Plot C. 268
70 Nitrogen in bulk precipitation. 269
71 Nitrogen loading in bulk precipitation through- 271
out the research marsh.
72 Changes in aboveground biomass nitrogen storage 272
for Plots H and C.
73 Changes in nitrogen storage of belowground bio- 274
mass.
74 Nitrogen export from Plot H in outflowing 276
water. Well W23M data used.
75 Nitrogen export from Plot H in outflowing 277
water. Well W23M data used.
76 Nitrogen export from Plot C in outflowing 278
water.
77 Nitrogen budget for the dry year in Plot H. 280
78 Nitrogen budget for the dry year in Plot C. 282
79 Nitrogen budget for the wet year in Plot H. 283
80 Nitrogen budget for the wet year in Plot C. 285
81 Percentage removal of nitrogen from treated 291
wastewater applied to Plot H.
xiii





Table Page
82 Organic N:total N and organic P:total P ratios 308
for applied treated wastewater, fresh water,
and exported water from Plots H and C.
83 Average molar total N:total P ratios for 309
treated wastewater, exported waters from the
high-rate loading plot, surface water in the
high-rate loading plot, natural marsh surface,
and adjacent channel waters.
xiv





LIST OF FIGURES
Figure Page
1 Aerial photograph of the experimental site. 2
2 Map showing location of research marsh in 9
relation to the city of Clermont and the
Palatlakaha chain of lakes.
3 Illustration of the structure of the experi- 12
mental plot, marsh vegetation, and the physi-
cal structure of the marsh.
4 Map showing the four experimental plots in 14
relation to Lake Hiawatha and Clermont's sew-
age treatment plant together with the orienta-
tion of the two water table transects (A and
B).
5 Detailed map of the experimental plots, the 16
location and depths of the groundwater wells,
and the location of the surface water sampling
stations.
6 Summary of significant water flows into and 19
out of each experimental plot in the marsh.
7 Four-day record of the water table elevations 22
in Plot C.
8 Evapotranspiration model and equation which 24
describes the interaction.
9 Map showing location of the 18 wells used in 27
the chloride tracer study conducted in Plot H
(9.6 cm/wk effluent).
10 Experimental design for preliminary nitrifica- 40
tion study.
11 Experimental setup for nitrification and 42
denitrification studies using soil:water
columns.
12 Ratio of water table rise to rainfall event 51
versus the depth to the water table in Plot C
xv





Figure Page
(3.8 cm/wk fresh water). The straight line
represents the least squares regression equa-
tion.
13 Ratio of water table rise to rainfall event 52
versus the depth to the water table in Plot H
(9.6 cm/wk treated wastewater).
14 Seasonal water table elevations in Plot H 55
(19.6 cm/wk) and Plot C (4.4 cm/wk of fresh
water).
15 Stage-duration curve, Lake Minnehaha, Lake 56
County, June 1945 September 1964.
16 Mean annual water level elevations in Lake 57
Minnehaha, 1946-1948.
17 Average monthly evapotranspiration versus the 63
product of average live aboveground biomass
and average saturation deficit.
18 Results of the chloride tracer study in Plot 70
H (9.6 cm/wk treated wastewater) from the
medium depth (1.5 m) wells.
19 Results of the chloride tracer study in Plot 71
H (9.6 cm/wk treated wastewater) from the deep
(2.5 m) wells.
20 Chloride concentration in the secondarily 72
treated wastewater.
21 Chloride concentration in wells in the natural 73
marsh.
22 Chloride concentration in wells in Plot H. 74
(9.6 cm/wk of treated wastewater).
23 Chloride concentration in wells in Plot M, 75
Plot C, and Plot L.
24 Chloride concentration in deep wells in the 76
natural marsh and the Palatlakaha River.
25 Aboveground live biomass for Plots C, M, and 89
H in the inside section of the plots (near the
distribution pipe) and in the outside section
of the plots.
26 Aboveground dead biomass for Plots C, M, and 92
H in the inside section of the plot (near the
xvi





Figure Page
distribution pipe) and in the outside section
of the plots.
27 Aboveground live and belowground live and dead 94
biomass for the inside region (near the dis-
tribution pipe) of Plot C.
28 Aboveground live and belowground live and dead 95
biomass for the inside region (near the dis-
tribution pipe) of Plot M (3.7 cm/wk).
29 Aboveground live and belowground live and dead 96
biomass for the inside region (near the dis-
tribution pipe) of Plot H (9.6 cm/wk).
30 Phosphorus in applied secondarily treated 102
wastewater.
31 Comparison of total phosphorus levels between 103
selected wells and applied secondarily treated
wastewater.
32 Total phosphorus for northwest corner medium- 106
depth wells.
33 Total phosphorus for Plot H wells (9.6 107
cm/wk).
34 Orthophosphate for Plot H wells (9.6 cm/wk of 108
treated wastewater).
35 Phosphorus concentrations for wells in Plot C. 110
36 Total phosphorus concentrations for the 111
natural marsh wells.
37 Orthophosphate concentrations for the natural 112
marsh wells.
38 Phosphorus concentrations for the natural 113
marsh deep wells.
39 Surface water total phosphorus concentrations 114
for Plot H, Plot C, and the undisturbed
natural marsh.
40 Surface water orthophosphate concentrations 115
for Plot H, Plot C, and the undisturbed
natural marsh.
xvii





Figure Page
41 River phosphorus concentrations. 118
42 Average phosphorus concentrations in live 124
aboveground biomass in Plot C (4.4 cm/wk fresh
wwate) and Plot H (9.6 cm/wk treated waste-
water).
43 Inside (near the distribution pipe) root phos- 130
phorus concentrations for Plot H (9.6 cm/wk).
44 Adsorption isotherms for peat taken from the 139
natural marsh.
45 Freundlich isotherm for peat depth 0-25 cm for 140
the natural marsh.
46 Freundlich isotherm for peat depth 25-50 cm 141
for the natural marsh.
47 Fruendlich isotherm for peat depth 50-75 cm 142
for the natural marsh.
48 Plot of observed phosphorus concentration with 144
peat depth.
49 Dry year decomposition bag experiment. 146
50 Phosphorus concentration in decomposing marsh 148
vegetation during the dry year.
51 Percent phosphorus remaining in the decom- 149
position bags during the dry year.
52 Microbial transformations and sources of nit- 166
rogen in the marsh.
53 Ammoniacal nitrogen remaining in flooded soil 173
core (15 cm of water) inoculated with ammonium
at day 0 and day 18.
54 Nitrate nitrogen present in flooded soil core 174
(15 cm of water) inoculated with ammonium at
day 0 and day 18.
55 Ammoniacal nitrogen remaining in flooded soil 175
core (30 cm of water) inoculated with ammonium
at day 0 and day 18.
56 Nitrate nitrogen present in flooded soil core 176
(30 cm of water) inoculated with ammonium at
day 0 and day 18.
xviii





Figure Page
57 Ammoniacal nitrogen remaining in intermit- 177
tently flooded soil core (30 cm of water)
inoculated with ammonium at day 0 and day 30.
58 Nitrate nitrogen present in intermittently 178
flooded soil core (30 cm of water) inoculated
with ammonium at day 0 and day 30.
59 Ammoniacal nitrogen remaining in flooded soil 179
core (15 cm of pH adjusted water) inoculated
with ammonium at day 0, day 18, and day 30.
60 Nitrate nitrogen present in flooded soil core 180
(15 cm of pH adjusted water) inoculated with
ammonium nitrogen at day 0, day 18, and day 30.
61 Ammonium concentrations in ammonium-amended 186
marsh soil after in situ incubation in poly-
ethylene bags.
62 Nitrate concentrations in marsh soil amended 188
with ammonium and/or lime after in situ incu-
bation in polyethylene bags.
63 Nitrate nitrogen remaining in flooded soil 193
core (15 cm of water) inoculated with nitrate
nitrogen at day 0 and day 18.
64 Nitrate nitrogen remaining in flooded soil 194
core (30 cm of water) inoculated with nitrite
nitrogen at day 0 and day 18.
65 Nitrate nitrogen remaining in intermittently 195
flooded soil core (30 cm of water) inoculated
with nitrate nitrogen- at day 0 and day 34.
66 Nitrate nitrogen remaining in flooded soil 196
inoculated with nitrate nitrogen at day 0 and
day 18.
67 Nitrate removal from nitrate-amended marsh 203
soil after in situ incubation in polyethylene
bags.
68 Ammonium production in marsh soil amended with 204
nitrate and/or lime after in situ incubation
in polyethylene bags.
69 Organic nitrogen concentrations in the treated 208
wastewater and the medium-depth natural
wells.
xix





Figure Page
70 Organic nitrogen concentrations in the wells 209
in Plot H (9.6 cm/wk of treated wastewater).
71 Organic nitrogen concentrations for the wells 210
in Plot C (4.4 cm/wk of fresh water) and Plots
L and M (1.5 and 3.7 cm/wk of treated waste-
water).
72 Organic nitrogen concentrations in deep nat- 211
ural wells, the Palatlakaha River, and Lake
Hiawatha.
73 Composited ammonia nitrogen in the applied 213
treated wastewater.
74 Ammonia nitrogen concentrations in the wells 214
in Plot H (9.6 cm/wk of treated wastewater).
75 Ammonia nitrogen concentrations in wells in 215
Plot L (1.5 cm/wk of treated wastewater),
M (3.7 cm/wk of treated wastewater) and Plot C
(4.4 cm/wk of fresh water).
76 Ammonia nitrogen concentrations in the natural 216
marsh wells, the Palatlakaha River, and Lake
Hiawatha.
77 Nitrate plus nitrite concentrations in natural 218
marsh wells and treated wastewater.
78 Nitrate plus nitrite concentrations for wells 219
in Plot H (9.6 cm/wk of treated wastewater).
79 Nitrate plus nitrite concentrations for wells 220
in Plot C (4.4 cm/wk of fresh water), Plot L
(1.5 cm/wk of treated wastewater), and Plot M
(3.7 cm/wk of treated wastewater).
80 Nitrate plus nitrite concentrations in deep 221
natural marsh wells, the Palatlakaha River,
and Lake Hiawatha.
81 Breakdown of the nitrogen forms in the applied 224
secondarily treated wastewater.
82 Total nitrogen concentrations for wells in 225
Plot H (9.6 cm/wk of treated wastewater).
83 Total nitrogen concentrations for wells in 226
Plot C (4.4 cm/wk of fresh water), Plot L (1.5
cm/wk of treated wastewater), and Plot M (3.7
cm/wk of treated wastewater).
xx





Figure Page
84 Total nitrogen concentrations in natural marsh 227
wells and wells to the west of Plot H (9.6
cm/wk of treated wastewater).
85 Total nitrogen concentrations in deep natural 228
marsh wells, the Palatlakaha River, and Lake
Hiawatha.
86 Organic nitrogen concentrations in surface 234
water in Plots C, H, and the natural marsh.
87 Ammonia concentrations in surface water in 235
Plots C, H, and the natural marsh.
88 Nitrate plus nitrite concentrations in surface 236
water in Plots C, H, and the natural marsh.
89 Total nitrogen concentrations in surface water 238
in Plots C, H, and the natural marsh.
90 Total nitrogen content in above- and below- 250
ground biomass in Plot H (9.6 cm/wk of treated
wastewater) near the distribution pipe.
91 Total nitrogen content in above- and below- 251
ground biomass in Plot C (4.4 cm/wk of fresh
water) near the distribution pipe.
92 Total nitrogen content in above- and below- 253
ground biomass in Plot H.
93 Total nitrogen content in above- and below- 254
ground biomass in Plot M.
94 Total nitrogen content in above- and below- 255
ground biomass in Plot C.
95 Average nitrogen content of dry matter remain- 259
ing in litter bags during the "dry" year on
each sampling date.
96 Percentage of original nitrogen mass content 260
of litter bagsduring the "dry" year remaining
on each sampling date.
97 Percentage of original dry weight remaining in 261
litter bags during the "wet" year on each
sampling date.
98 Average nitrogen content of dry matter remain- 263
ing in litter bags during the "wet" year on
each sampling date.
xxi





Figure Page
99 Percentage of original nitrogen mass content 264
of litter bagsduring the "wet" year remaining
on each sampling date.
100 Treated wastewater loading and hydrologic 287
export of nitrogen in Plot H (9.6 cm/wk of
treated wastewater).
101 Freshwater loading and hydrologic export of 288
nitrogen from Plot C (4.4 cm/wk of fresh
water).
102 Treated wastewater and freshwater loadings and 290
observed hydrologic export of nitrogen from
Plots C (4.4 cm/wk of fresh water) and H (9.6
cm/wk of treated wastewater) during wet and
dry years.
103 Summary of sources, changes in storage, and 298
export of nitrogen and phosphorus in Plot H
during the dry year.
104 Summary of sources, changes in storage, and 299
export of nitrogen and phosphorus in Plot C
during the dry year.
105 Summary of sources, changes in storage, and 300
export of nitrogen and phosphorus in Plot H
during the wet year.
106 Summary of sources, changes in storage, and 301
export of nitrogen and phosphorus in Plot C
during the wet year.
Al Description of symbols used in models. 314
A2 Water table elevations measured along the 316
south-north transect.
A3 Water table elevations measured along the 317
west-east transect.
xxii





EXECUTIVE SUMMARY
TO
CITY OF CLERMONT
FLORIDA
REMOVAL OF NUTRIENTS FROM TREATED MUNICIPAL
WASTEWATER BY FRESHWATER MARSHES
JOHN ZOLTEK, JR. AND SUZANNE E. BAYLEY, PRINCIPAL INVESTIGATORS
ALBERT J. HERMANN, LOUIS R. TORTORA, AND THOMAS J. DOLAN
GRADUATE RESEARCH STUDENTS
WITH CONTRIBUTIONS FROM
DONALD A. GRAETZ AND NANCY L. ERICKSON
SOILS SCIENCE DEPARTMENT
CENTER FOR WETLANDS
UNIVERSITY OF FLORIDA
GAINESVILLE, FLORIDA 32611
SEPTEMBER 1979





REMOVAL OF NUTRIENTS FROM TREATED MUNICIPAL
WASTEWATER BY FRESHWATER MARSHES
EXECUTIVE SUMMARY
Introduction
This report presents the results of two years of application of
secondarily treated wastewater into a freshwater marsh on the out-
skirts of the city of Clermont, Florida. Figure 1 is a photograph of
the four enclosed experimental plots connected by a boardwalk to the
dike surrounding the Clermont Sewage Treatment Plant Percolation
Pond. The entire project was funded by city and county agencies.
The objective of the study was to determine at what rate and in what
manner secondarily treated wastewater could be applied to a fresh-
water marsh with minimal effect on the marsh and surrounding waters.
This study utilized four 0.5 acre (2000 m2) plots. Three of
these received secondarily treated wastewater at the low, medium, and
high rates of 0.6 in./wk (1.5 cm/wk), 1.5 in./wk (3.7 cm/wk), and 3.8
in./wk (9.6 cm/wk), respectively. A fourth plot used as a control
received 1.7 in./wk (4.4 cm/wk) of fresh water from a municipal well.
Collected data included the following: standing crop of vegetation;
phosphorus and nitrogen content of aboveground and soil water,
applied wastewater, and vegetation; volume of rainfall and wastewater
or fresh water loadings; and water table elevation.
Experimental Results
1. A two-year study on the effects of application of secondarily
treated wastewater to a freshwater marsh in central Florida
showed no significant release of nutrients from any plot to the
environment adjacent to or below the experimental plots.
1





.- -
....-...~ .._ '. '.:" ''-" ,. _
.~ '.~,~, .
24cy~>, -9 %s~: A ~ n -. ... ... : ~ ~~ ;.~.,,~,, :,: :
*u ~ ~ ~ ~ ~ ~ ~ ~~~~~~M
AoW.,
i_~~~~~~~~ ..~~_. ,
:~~~~~~~~~~~~~~~~~~j~~~~~~~~~~~~~~~~~~ ~ -. -i..;~ -',~~. ~7 ~ ~..
Eli fV.. ~e.~i;~'.i-..
Figure 1. Aerial photograph of the Clermont Marsh Study Area.
The north direction is from the upper right corner to the lower
left corner. The Palatlakaha River is shown in the foreground.
-~~~~~~~~~~~~~."' .,'"~" '.~ .-''' ./.-?
,...'.~ ..~,..~ . -.,. -? ~, ~~ ~ .~
,~, ~~~,,.~ ....- ,~'....,,,,:...,_,,:,
.. ; '"' '' ""*~"-""~..
~~~~~~~~~~~~~~~~~~~,; .,c .......
:y. ~- : ~ -, ~,'. ~ ~~~~~~ ~~~~~~~~~~~~~~~~~'.~ Ml. '.
"! .~. .~ ., ~,.~, .. .-..
~"~' ~.., ~ ~. "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~; i
'.i'~ '" ":~"" .;. ~
Figure 1. Aerial photograph of the Clemn as td ra
The, n o r t d ietinisfomteuppe righ conrt hoe
lef conerTh Paltla a h Rvri s shownU in~ the: frgon.1





2. Data collected from wells in experimental plots showed a concen-
tration of phosphorus that was not significantly greater than
the concentrations observed in wells located in the natural
marsh (approximately 0.1 mg/1). This represented only 3% of the
applied phosphorus. There was negligible export of phosphorus
out of any plot in the surface water. During the dry year, the
bulk of the applied phosphorus appeared to have been adsorbed by
the soil complex. During the wet year the soil complex may not
have stored phosphorus. The large concentration of phosphorus
(avg. 7.3 mg/1) in the standing water in the high rate loading
plot (3.8 in./wk) was presumed to originate from the applied
water as well as being released from the soil complex.
3. All forms of nitrogen in applied secondarily treated wastewater
approached average background concentrations of the marsh in
both standing water and exported soil water. These results were
obtained under all loading rates for both wet and dry condi-
tions. The bulk of the applied nitrogen was lost to the atmos-
phere in gaseous form (as N2 and N20); a small amount was
deposited as new peat. Of the inorganic nitrogen applied to the
high rate loading plot (3.8 in./wk), 94% was removed by the marsh
system during the dry year. The wet year value was 96%.
4. Applied secondarily treated wastewater stimulated the growth of
semiwoody plants in the dry marsh; specifically, marsh hibiscus
and buttonbush. Algae and duckweed grew in the vicinity of
wastewater application pipes when standing water was present.
Application of Results to Other Areas
1. Any secondarily treated wastewater applied to the marshland must
pass through the peat for maximum removal of phosphorus to
occur. The marsh-treatment system should therefore be designed
so as to insure passage of all applied wastewater through the
peat substrate. In this study, 97% removal of phosphorus and
95% removal of total inorganic nitrogen were obtained in a marsh
having a peat depth of 1.5 m.
3





2. based on the results of this study, an application rate of 1.5
in./wk should not produce detrimental water quality impacts in
groundwater or adjacent water bodies provided the treated waste-
water passes through the peat.
3. The long-term effects (greater than five to ten years) are un-
known for this marsh since the study covered only two years. A
recent study in Wildwood, Florida, indicated that a small
marsh/shrub area within a wooded swamp was still functioning to
remove phosphorus after approximately 20 years.
Application Methodology
1. The experimental plots received secondarily treated wastewater
once a week over a 24-hr period. This provided a six-day
"restoration" period during which time the marsh could assimi-
late the applied load. A similar "restoration" period should be
considered in the design of the proposed wastewater treatment
system.
2. Application of the wastewater was achieved via a low pressure
piping system that provided a relatively uniform distribution
over the interior portion of the experimental plots. All ef-
forts should be made to achieve a similar distribution in the
proposed application system.
4





INTRODUCTION
Overview
The ability of a freshwater marsh to assimilate the phosphorus
and nitrogen in secondarily treated municipal wastewater was evalu-
ated in this study. The evaluation of a natural ecosystem, which is
to be utilized for advanced waste treatment, raises several important
ecological and engineering issues. One of the important aims of this
research was to determine the structural and functional responses of
the system to the water and nutrient subsidies. The marsh system may
build structure to accumulate the input nutrients. Further, the
treated wastewater subsidies may increase the overall flows of water
and nutrients through the system. From an engineering standpoint, it
is important to consider the ultimate fate of the applied nutrients
and the rate at which the treated wastewater can be applied without
overloading the marsh system. Marsh systems may provide a very
attractive alternative to expensive, fossil fuel-subsidized advanced
waste treatment plants.
There exists a variety of natural systems that have the capabil-
ity of providing advanced waste treatment. The common characteristic
of these ecosystems is their ability to assimilate and store nitrogen
and phosphorus in plant tissue or in the soil. Sopper and Kardos
(1973) illustrated the potential of recycling sewage effluent using
terrestrial systems. Secondarily treated municipal wastewater was ap-
plied to forage crops, red pine plots, and white spruce stands.
Annual crop yields and tree growth were significantly greater with
effluent irrigation. Renovation of the wastewater was particularly
successful in the reed-canary forage grass plots. The annual crop of
reed-canary grass removed 35% of the phosphorus applied and 97% of
the nitrogen. The remaining 65% of the phosphorus was retained by
the soil. There are two drawbacks to extensive use of terrestrial
systems. The treated wastewater pumping and distribution costs may
5





be prohibitively high. In addition, the water stress imposed by the
treated wastewater could limit widespread or long-term use.
Wetlands provide a possible alternative to the use of terres-
trial systems. Marshes and swamps are adapted to flooded soil condi-
tions, and the distribution problem is minimized since the effluent
can be spread by the movement of the already existing standing water
in the system. Marshes and swamps are also two of the most produc-
tive ecosystems in the world (Lieth 1975). This high growth rate
suggests an equally high assimilation of nutrients in plants.
The suitability of swamps to act as nutrient sinks has been
studied extensively in Florida. Cypress domes in central Florida
receiving primary wastewater have shown increased growth. The plant
community together with the soil compartment proved to be an effi-
cient filter for the applied phosphorus and nitrogen (Odum and Ewel
1977). Boyt et al. (1976) found that primarily treated sewage under-
went a 98.0% reduction in the phosphorus concentration and a 89.7%
reduction in the nitrogen concentration after passing through a mixed
hardwood swamp. Growth rates for the cypress trees in the swamp were
also found to be higher than for trees in a control area. Likewise,
trees in a cypress strand receiving raw sewage for the past 40 years
grew significantly more than trees in a control area (Nessel 1978).
The phosphorus concentration of the effluent was significantly
reduced after flowing through the cypress strand.
Wisconsin freshwater marshes have been studied extensively with
regards to cycling of nutrients under natural conditions together
with studies that emphasized the water quality role of the marsh eco-
system (Fetter et al. 1978; Klopatek 1975; Lee et al. 1975). In
Florida, marsh research has centered on the functioning of the Ever-
glades vegetation under both natural and enriched conditions (Davis
1978; Steward and Ornes 1975a, 1975b).
Marshes in a variety of other geographic areas have also been
studied to determine their effectiveness in wastewater renovation.
Michigan peatlands, freshwater tidal marshes, saltmarshes, and man-
made marshes have each been sites for treated wastewater disposal
research. In a Michigan sedge-willow peatland subjected to nearly 6
cm/wk of secondary effluent Kadlec et al. (1977) found that the marsh
6





functioned as a nutrient sink for both nitrogen and phosphorus.
Within 30 m of the effluent discharge point in the peatland, 99% of
the nitrate-nitrite nitrogen, 95% of the total dissolved phosphorus,
and 71% of the ammonia was removed from the effluent. Increased
plant standing crops and higher levels of plant tissue phosphorus
were found in a band extending the length of the effluent discharge
pipe. Higher concentrations of both nitrogen and phosphorus were
also measured in the soil along the discharge pipe. Denitrification
appeared to be an important sink for the applied nitrogen.
In a preliminary study to determine the nutrient renovation
capability of a Delaware River freshwater tidal marsh, experimental
plots have been subjected to a maximum of 12.7 cm/day of secondary
effluent (Whigham and Simpson 1976). Numerous studies have been made
to determine the effect of increased nutrient loads on saltmarsh
vegetation. In Louisiana, the effect of supplemental inorganic
nitrogen and phosphorus on stands of Spartina alterniflora have been
measured (Patrick and Delaune 1976). Valiela et al. (1975) have
reported that application of sewage sludge to S. alterniflora stands
on the coast of Massachusetts caused an increase in the annual maxi-
mum standing crop. On Long Island, New York, a marsh system has been
artificially constructed to determine the feasibility of its use in
the renovation of raw sewage (Small 1977). Results indicate that the
system removes the major portion of nitrogen and orthophosphate in
sewage applied to it (Small 1978).
Whigham and Bayley (in press) reviewed studies of nutrient
absorption in wetlands to determine what ecosystem parameters were
most important in determining the waste treatment capacity of any
particular wetland. They compared the amounts of nitrogen and phos-
phorus that accumulated annually in aboveground vegetation in differ-
ent wetlands. They also compared the removal of nutrients by differ-
ent wetlands as demonstrated by mass balance studies in those
systems. They found that the type of substrate, organic versus inor-
ganic, was potentially important in determining the nutrient assimi-
lation capacity of a wetland. Wetlands with organic peat substrates,
though accumulating less nitrogen and phosphorus in their annual
production of aboveground vegetation, appeared to be more capable of
processing wastewater than wetlands with inorganic substrates.
7





Project Objective
In this study, secondarily treated wastewater was applied to a
freshwater marsh ecosystem located near the city of Clermont in
central Florida from May 1, 1977 through June 1, 1979. The main ques-
tions posed and addressed were the following:
Does the nutrient subsidy in the treated wastewater result in an
increased level of annual net production? Under treated wastewater
application is there a corresponding increase in belowground produc-
tion as well as aboveground production? Does application of treated
wastewater and freshwater significantly alter the hydrology of the
plots as compared to the undisturbed marsh? What is the quality of
the treated wastewater after flowing through the marsh system? How
much phosphorus and nitrogen is exported from the plots compared to
the amount of nutrients applied? What are the major phosphorus and
nitrogen sinks in the marsh? Does the marsh act as an efficient
tertiary treatment facility? What loading rate provides the most
efficient and practical treated wastewater renovation?
Description of the Study Area
The research site lies in the northward flowing Palatlakaha
River watershed, part of the St. Johns River Basin (Fig. 2). The
site is located within the city of Clermont (population 4800), 40 km
to the west of Orlando, Florida. The Palatlakaha chain of lakes is
known for its clear, clean, low productivity waters and is fed by the
Green Swamp located to the south of Clermont (Wilkes and Kaleel
1972). The experimental marsh is located in 32 hectares (ha) of
marsh immediately south of Lake Hiawatha, and it is adjacent to the
city of Clermont's 0.6 mgd sewage treatment plant. The chief land
uses in the Clermont area are either residential or agricultural
(primarily citrus groves).
8





IAKE LAKE MI NEHA
INA^ 4CHERRY
LAE LOUISA
MINNEOLA
LAKE HIAWATHA^ HIW
cm 7km RESEARCH
Figure 2. Map showing location of research marsh in
relation to the City of Clermont and the
PaatakhaCLERMONTs
LAKE PALATLAKAHA
LAKE MINNEHAHA
LAKE LOUISA
I cm -= .771 km
Figure 2. Map showing location of research marsh in
relation to the City of Clermont and the
Palatlakaha chain of lakes.
9





Marsh Vegetation and Substrate
The vegetation in the experimental plots was primarily composed
of emergent aquatic macrophytes. Sagittaria lancifolia (arrowhead),
Pontederia cordata (pickeral weed), Panicum spp. (panic grass), and
Hibiscus spp. (marsh hibiscus) were the dominant species. Table 1 is
a listing of the dominant species present in the experimental site.
Davis (1946) characterized a marsh dominated by these species as a
flag pond marsh. When standing water was present in the marsh, vari-
ous species of blue-green algae, green algae and diatoms, as well as
Lemna sp. (duckweed), were present in that standing water.
The general physical structure of the marsh is schematically
illustrated in Fig. 3. The top layer, approximately 1.5 m thick,
consists of the highly organic, Brighton series, peat soil (USDA
1975). This organic matter was composed of both undIecomposed and
decomposing herbaceous plant material. The peat soils are very
acidic; the pH ranges from 4.15 to 4.78 (Davis 1946) A zone of
saturated coarse sand is found below the peat layer. A confining
layer of kaolinite clay and sand separates the marsh scil water from
a direct connection with the underlying Floridan Aquifer (Knochenmus
and Hughes 1976).
10





Table 1. Dominant marsh plants of the research site.
Species Common Name
Sagittaria lancifolia Arrowhead
Pontederia cordata var. Lancifolia Pickerel weed
Panicum spp. Panic grass
Hibiscus spp. Marsh hibiscus
Peltandra sp.
Ludwigia peruviana Primrose willow
Cephalanthus occidentalis Buttonbush
Mikania sp. Climbing hempweed
Ludwigia spp. ---
Cladium jamaicense Sawgrass
11





_ ,GLASS W
FIBERGLASS TREATED WASTEWATER DISCHARGE PIPE
WATER
). E 0 ^sTABLE
E % *"-,f', PEAT
..- i *. SATURATED SAND .
Figure 3. Illustration of the structure of the experimental plot, marsh
vegetation, and the physical structure of the marsh.





METHODS
Experimental Plots
Four 2000 m2 experimental plots were constructed in the 32-
ha marshland just south of Lake Hiawatha. The layout of the experi-
mental site is shown in Fig. 4. The structural details of each plot
were shown in Fig. 3. The perimeter of each plot consisted of
corregated fiberglass panels supported by wooden posts. The panels
were placed to a depth of 0.6 m in the peat and extended 1.5 m above
the peat surface. Joints and corners were sealed with caulking
compound. The purpose of the wall was to constrain applied surface
water within the area of each plot.
While secondarily treated wastewater was delivered to three of
the experimental plots, a fourth plot recieved municipal fresh water
pumped from a nearby groundwater well. Water was delivered to each
of the plots via a 30 m-long perforated PVC pipe suspended 1.5 m
above the peat surface. The pipes were oriented south-to-north
through the center of each plot. Water was jetted out of the perfor-
ated pipe, under pressure, in a downward direction. Applied water
contacted the marsh surface within a 3 m corridor directly beneath
each application pipe. Since the water was not sprayed, evaporative
loss was minimized. This simplified the eventual development of a
hydrologic budget.
Each plot received its water loading over a 24-hour period once
each week. Plot C, the control plot, received 4.4 cm/wk of fresh
water. Plot L, the lowest-rate plot, received 1.5 cm/wk of treated
wastewater. Plot M received an intermediate rate, 3.7 cm/wk treated
wastewater. Plot H received the highest loading rate, 9.6 cm/wk.
13





I/. wELAKE HIAWATHA s\\ l
PA 1 X
/ l I I n^ ^^
B ...WAGE. SPRAY
PLANTo FIELD
FIELD
['"> J~'PERCOLATION ,' I -
POND
v\~ ~ .I \~~ | | BALLFIELD
^YCX 1.- ^SPRAY
Figure 4. Map showing the four experimental plots in
relation to Lake Hiawatha and Clermont's
sewage treatment plant together with the
orientation of the two water table transects
(A and B). Plot C receives 4.4 cm/wk fresh-
water. Plots L, M, and H receive 1.5, 3.7,
and 9.6 cm/wk treated wastewater
respectively.
14





Application was initiated on May 1, 1977 and continued through
June 1, 1979.
Figure 4 shows the location of the groundwater wells, surface
water sampling stations, water level recorders, and the rain gauge.
Wells consisted of 1.5 in. diameter PVC pipe with approximately 0.25
m of 1.0 in. diameter slotted PVC screening at the bottom. Shallow
wells were placed to a well bottom depth of 0.5 m. Medium depth
wells were placed to the bottom of the peat layer, which was approxi-
mately 1.5 m deep. Deep wells were installed in the sand layer, 2.5
m below the marsh surface.
A hydrographic survey indicated that the water table, when
below the surface of the peat, sloped in a northwesterly direction
(See Appendix). Medium depth wells (W21M, W22M, W23M, W24M) were
placed in the northwest corner of each plot. Water samples from the
wells were considered representative of renovated water leaving each
of the respective plots. A medium depth well located several hundred
feet to the north of the experimental plots (W2M) served as a natural
background control well for water at the bottom of the peat layer.
Deep wells placed along a transect between the percolation pond and
the experimental plots (see Figs. 2 and 5) monitored possible contam-
ination of the sand layer by the percolation pond and regional,
upland seepage.
When the water table was above the surface of the peat, surface
water samples were collected in the marsh. The location of each
surface sampling point is shown in Fig. 5. As shown, sets of three
samples each were collected along north-south transects beneath the
application pipe and approximately 3 m from the western boundary
within each plot. Another three-sample transect was located 10 m
west of Plot H. Two sets of three samples each were collected near
well W2M; samples within each of these two sets were taken within a 3
m radius.
A recording rain gauge (Belfort weighing rain gauge) and four
eight-day water level recorders (Stevens Type F recorder) were posi-
tioned in the marsh as shown in Fig. 5. The recorders in Plots C and
H operated continuously throughout the study. The recorder in the
natural area of the marsh, to the north of the plots, was
15





C I M
I I V N
JM -o
8 D M-I
22 M
L-| SRA WEST
L/1
X | c 4M D..M
\i / |~ I I-~23 12H-I
C E H-9
PLOTLMf6 PLOT Hj
21
! PLOT C
* WELL STATION
S SHALLOW .5m
M MEDIUM 1.5m
D DEEP 2.5m
0 SURFACE WATER STATION
N A WATER LEVEL RECORDER
16 a RAIN GUAGE
C- 4.4 cm/wk freshwater
L-1.5cm/wk treated wastewater
H- 9.6 cm/wk treated wastewater
- 3.7 m/wk treated wastewater
D
'17
Figure 5. Detailed map of the experimental plots, the location
and depths of the groundwater wells,,and the location
of the surface water-sampling stations.
Well numbers hereafter are preceded by a W and followed
by an M (indicating a medium-depth well) or a D (indicating
a deep well).
16





operated from November 14, 1978, through the end of the study. The
recorder in Plot M was operated from May 31, 1978, through the end
of the study.
Water Chemistry
Grab samples of applied treated wastewater were obtained period-
ically during each weekly application date. Each time a grab sample
was obtained, a portion of the sample was added to a monthly compos-
ite frozen sample. Freezing prevented interconversion of the several
nitrogen species prior to analysis. Another portion of each grab
sample was added to a monthly composite unfrozen sample, used for
phosphorus analyses.
Wells and surface water stations were sampled monthly, 24 hours
after the end of the most recent treated wastewater application.
Samples were collected in acid-washed plastic bottles. All wells
were pumped out using a portable hand pump. After May 3, 1978, all
medium and shallow depth wells were pumped dry and allowed to
recharge before taking a sample. All deep wells were flushed by
pumping out 3 liters of water prior to sampling.
Surface samples collected in the marsh were obtained using 150
ml acid-washed plastic bottles. Water was sampled immediately below
the surface. The three 150 ml samples in each set described above
were combined into one composite sample for that set. All samples
were transported back to the lab and immediately refrigerated.
Surface samples were filtered immediately upon return to the lab
using a Reeve Angel 934 AH glass-fiber filter to remove any
suspended algae or floating plants.
After September 1977, all samples were filtered through a Reeve
Angel 934 AH glass-fiber filter prior to analysis. Measurements of pH
were performed within three hours of sampling and again just prior to
analysis using a Corning model 12 pH meter with a catalogue number
476022 electrode. Samples were analyzed for the following para-
meters: nitrate nitrogen, nitrite nitrogen, ammonia nitrogen, total
Kjeldahl nitrogen, orthophosphate, and total phosphorus. Organic
17





nitrogen values were obtained by subtracting the ammoniacal nitrogen
value from the total Kjeldahl nitrogen value for each sample. Total
nitrogen was taken as equal to nitrate plus nitrite plus total
Kjeldahl nitrogen. The procedures used for these analyses followed
those in APHA (1976). Analysis for ammoniacal nitrogen was performed
using the automated colorimetric phenate method. Concentrations of
nitrate nitrogen and nitrite nitrogen were determined using the
automated cadmium reduction method. Total Kjeldahl nitrogen (free
ammonium plus organic nitrogen) was measured using the automated
phenate method. Concentrations of total phosphorus and
orthophosphate were determined by the stannous chloride method
described in APHA (1976).
Hydrologic Measurements
One important goal of this study was to construct an input-
output mass balance for nitrogen and phosphorus in the marsh plots.
Such a mass balance requires estimates of hydrologic flows into and
out of the system. The boundary between the peat and sand layers was
chosen as the lower boundary of the marsh system; flux measurements
for water were derived for the peat and plant community lying above
this lower boundary. The significant fluxes into the system were
applied treated wastewater or fresh water, rainfall, and inflowing
water from the adjoining channel and lake. The significant outward
fluxes were evapotranspired water and outflow to the adjoining chan-
nel and lake. Water flux is summarized in Fig. 6.
Specific Yield
The changes in volume of water contained within the marsh plots
over time were derived from water level records made by the contin-
uous strip chart recorders placed inside the plots (see Fig. 5 for
recorder locations). The volume change represented by a drop or rise
in the water table is a function of the specific yield of the peat.
Specific yield is the ratio of the volume of gravity-drainable
18





TREATED\ EVAPOTRANSPIRATION
WASTE-
WATER
OUTFLOW
-W RIN INFLOW AND
/ \ ,J. PLOT -------- LAKE
( AINFA LL
Figure 6. Summary of significant water flows into and out of
each experimental plot in the marsh. See Appendix
for a description of symbols.
19





water to the volume of soil that contains that water. Gravity-
drainable water is that water free to move under the influence of
hydrostatic pressures in the soil. The remainder of the water is
held immobile by electrostatic forces within the soil complex, though
it may evaporate under dry conditions. Specific yield may vary with
depth in a soil. Specific yield was calculated in this study by
measuring the rise in the water table elevation associated with brief
(less than 1 hour) rainfall events of 1 cm or more.
The ratio of the depth of rainfall (R) to the increase in water
table elevation (W) was considered representative of the specific
yield (S) at the original depth of the water table (d) in the peat
soil:
Sd=(R/ W)d
The calculated specific yield values (Sd) were found to be
linearly correlated with their respective depths (d). Separate
correlations were performed for the two water level recorders in
Plots C and H. This produced a specific yield depth function both
for Plot C and for Plot H. This function was applied to obtain spec-
ific yield values when the water table was less than 2.10 cm above
the surface of the peat in Plot H, and less than 6.13 cm above the
surface of the peat in Plot C. Above these heights, which represent
the values at which the respective specific yield equations yielded a
value of 1.0, actual specific yield in the plots was assumed to be
1.0.
Evapotranspiration
During those periods when the water table was below the surface
of the peat in the marsh, the continuous water level records were
utilized to obtain estimates of evapotranspiration (Heimberg 1976).
The rise or fall of the water table observed during nighttime hours
represented net flow of water to or from the marsh due to hydrostatic
forces alone. The rate of change in water table elevation during
each night was extrapolated up to noon of the following day and back
to noon of the previous day. These noon elevations represented where
the water table would be if no evapotranspiration had occurred over
20





the whole 24-hour period centered on each successive night. The
difference between the elevation extrapolated from the previous night
and the elevation extrapolated from the following night represented
the water loss due to evapotranspiration during that day. An
illustration of this procedure is given in Fig. 7. The method was
applied to the water level recorders in Plots C and H, respectively,
for clear, rainless days. Rain obscured the water table drop. The
observed elevation change due to evapotranspiration was multiplied
by an appropriate specific yield value to get the actual volume of
water lost by evapotranspiration that day. To obtain specific yield,
the water table elevation observed in the plot at noon of that day
was entered into the specific yield depth equation derived for that
particular plot.
The daily evapotranspiration values calculated using the recor-
ders in Plots C and H represented the average transpiration of the
entire marsh area on that day, rather than evapotranspiration spec-
ific to each plot. This was due to the strong hydraulic connection
between each plot and the surrounding area of the marsh. All the
daily evapotranspiration estimates calculated from the recorders in
Plots H and C during a particular month were averaged together to
yield an evapotranspiration rate estimate (in cm/day) for that month.
This method of empirically estimating evapotranspiration could only
be applied during those months when the water table was either below
or near the surface of the peat. When larger amounts of standing
water were present in the marsh, the water surface was contiguous
with the water flowing in the adjacent channel. Due to a suffi-
ciently strong hydraulic connection, any evapotranspired water was
almost immediately replenished by the adjacent waters of the channel.
Thus, no drop attributable to daily evapotranspiration was seen in
the water level records on days when the water table was high. After
June 1978, the water table was too high to employ the method. Before
this month, the method was consistently applied except for December
1977.
Empirical evapotranspiration estimates were thereby avail-
able for only the first 13 months of the study, May 1, 1977 May
31, 1978. These monthly evapotranspiration rate averages
21





WATER
PUMPING
28.65-
w
28.62-
z / A-, WATER OUTFLOW
s2~~ / EVAPO-
W 28.59- TRANSPIRATION
0
> 28.56- ,EVAPOTRANSPIRATION
5 7
5-23-77 5-24-77 5-25-77 5-26-77 5-27-77
DAY
Figure 7. Four day record of the water table elevations in Plot C
(4.4 cm/wk freshwater). The effect of evapotranspiration,
water pumping, and water outflow on the water table is
indicated.





(ETave) were determined to be linearly related to the product
of aboveground live biomass (B) and saturation deficit (SD) for each
respective month:
ETave = (K1 x B x SD) + Ko
This model of evapotranspiration is illustrated in Fig. 8. The coef-
ficients K1 and Ko in the equation were determined by linear
regression of the empirical estimates of evapotranspiration, derived
from the water level records, to measured values of average natural
marsh live biomass and meteorologic data obtained from regional
summaries. For monthly aboveground live biomass the averages of
values obtained for the outside regions of all four plots were used.
This was done because no significant difference in aboveground live
biomass (a = .01) was detected among the plots' outside areas during
either the first or second years. (See live aboveground biomass
section). Hence outside area averages were considered the best
available estimate of natural marsh biomass for both years.
The model of evapotranspiration so derived from the first 13
months' worth of data was subsequently applied to get separate evapo-
transpiration estimates for Plot C, Plot H, and the natural area of
the marsh during that 13-month period. Linear interpolation between
successive biomass measurements was performed to obtain a biomass
estimate for the middle of each month. Saturation deficit values for
each month were derived using monthly means of daytime temperature
and monthly means of the relative humidity occurring at 4:00 p.m., as
given in NOAA (1977, 1978) for Orlando, Florida. Orlando is located
32 km (20 mi) to the west of Clermont. The Smithstonian Metero-
logical Tables (1951) were employed to get the saturation moisture
content of air at each mean monthly temperature. The average above-
ground live biomass values for the entire area of Plot C were
employed to get monthly evapotranspiration rates for Plot C. This
same procedure was applied for Plot H. (See the plant community
measurements section for details on how "entire-area" averages were
calculated.) The average values for the outside regions of all
23





SATURATION
DEFICIT
LiVE
ABOVEGROUND
~\ | ~ ~BIOMASS
7 ; X ' *EVA POTRANSPIRATION
E =KxBxS xW
ASSUMING UNLIMITED WATER:
E =KxBxS
Figure 8. Evapotranspiration model and equation which
describes the interaction. See Appendix
for description of symbols.
24





plots were employed as representative of the natural marsh biomass.
Linear interpolation between successive biomass values was applied as
needed to get averages of biomass for each area for each month.
To estimate evapotranspiration during the second year for Plot
C, Plot H, and the natural area, the same model equation was used
as for the first year. This was necessary since no empirical esti-
mates were available for evapotranspiration during the second year.
Biomass values for the entire areas of Plots C and H and the average
values for the outside regions of Plots C, M, and H were employed in
the model equation for Plot C, Plot H, and the natural marsh area,
respectively.
To derive model coefficents and to predict evapotranspiration
from the model, the woody component of total live biomass in all
areas was excluded from the total live biomass value obtained on
sampling dates December 3, 1977, February 20, 1978, December 15,
1978, and February 18, 1979. This was done because negligible leaf
area was observed on woody species during those sampling periods.
The contribution of such species to marsh evapotranspiration was
probably negligible for those periods. Eliminating the live wood
component helped reduce the variance of biomass estimates within
plots during those periods for use in the evapotranspiration model.
Outflow
Total monthly outflow from each of the plots was computed by
the continuity equation:
0 = W + R ET -A S
where 0 is the total outflow during the month, W is the volume of
treated wastewater or fresh water applied that month, R is the
volume of rainfall for that month, ET is the evapotranspiration as
derived from the evapotranspiration model, and AS is the change in
water storage in the plot between the beginning and end of the
month.
25





Distribution of Applied Water
Throughout the study there was a major concern for the effec-
tive distribution of applied treated wastewater throughout the plots.
In particular, strong assurance was required that applied treated
wastewater flowed past the northwest corner medium depth wells of
Plots L, M, and H. Treated wastewater applied to the plots was known
to contain higher levels of chloride than were present in the undis-
turbed areas of the marsh. Chloride is believed to be a passive,
conservative element in biological systems; it is largely unused by
microbes and plants and does not bind significantly to soil. There-
fore, chloride in applied treated wastewater was used as a tracer in
Plots L, M, and H.
A three-day experiment was conducted to investigate applied
treated wastewater distribution in Plot H. A matrix of nine pairs of
wells was placed within and just exterior to Plot H. Nine of the
wells were installed at the bottom of the peat layer (medium depth
wells), and nine were installed in the sand layer (deep wells) at the
same locations as the medium wells (see Fig. 9). The wells were
sampled via hand pumps on three consecutive days, just prior to,
during, and 24 hours after a weekly pumping of treated wastewater.
All medium depth wells were pumped dry and allowed to refill prior to
sampling. Deep wells were flushed by pumping out 2 liters of water
prior to sampling. A sample of applied treated wastewater was also
collected. The experiment was conducted from March 27, 1978 to March
29, 1979, at which time the water table was 2.4 cm above the surface
of the peat. All samples were analyzed for chloride according to
APHA (1976) procedure.
Between February 9, 1978 and November 10, 1978, all water
samples collected in the marsh, plus the treated wastewater samples
collected each month, were analyzed for chloride content. This
provided further information on the distribution of applied treated
wastewater (under changing hydrologic regimes) throughout the plots
in surface water and groundwater.
26





MO
D
Me
Me Mo MO
DO Do D *
6 7 8 N
TREATED
WASTEWATER
DISCHARGE PIPE
SCALE
- lOm
M-MEDIUM WELL 1.5m depth
M* D-DEEP WELL 2.5m depth
D
Do
9
Figure 9. Map showing location of the 18 wells
used in the chloride tracer study
conducted in Plot H (9.6 cm/wk treated
wastewater).
27





Plant Community Measurements
Biomass Measurement
In order to determine the effects of added nutrients on plant
growth and plant nutrient storage, periodic harvest of aboveground
live, aboveground dead, and belowground live plus dead biomass
samples was carried out in the experimental plots. Harvested areas
were defined using randomly placed 0.25 m2 quadrats. At the out-
set of the study, it was observed that plants were more affected by
applied treated wastewater in the area immediately surrounding the
application pipe. To achieve smaller variance within sampled popu-
lations a stratified sampling procedure was used in each plot.
Three randomly chosen 0.25 m2 squares were harvested from a 462
m2 area defined by a perimeter 7.21 m to either side of the appli-
cation pipe, and 5.15 m from the northern tip of the pipe. This
area was designated as the "inside"(I) region for the plot.
Three randomly chosen 0.25 m2 squares were harvested from the
rest of the plot, in the area further away from the application
pipe. This area was designated as the "outside" (0) region for the
plot. Areas within 2.1 m of each plot's fiberglass border were
excluded from sampling to avoid any influence of the wall on
measured growth. Areas within 1.0 m of the pipe were excluded as
well to avoid any influence of this structure on measured growth.
In dealing with biomass data for the experimental sites average
values were often desired for the entire area of a plot. Area-
weighted averages were derived in such cases. The inside region
comprised 25% of the total area of a plot, while the outside region
comprised 75% of the total area. Thus, area-weighted averages for
the entire plot were computed by :
B entire area =(0.25 x B inside area) + (0.75 x B outside area)
Aboveground live biomass was harvested by clipping plants with
lawn shears down to the surface of the peat. Loose litter was
gathered up by hand; any litter that had become incorporated into
the peat-root mat was excluded. Beginning with the June 28, 1978
28





sample, a hand rake was employed in gathering litter to help dislodge
litter enmeshed between plant stalks.
Belowground biomass, when harvested, was always taken from the
same 0.25 m2 areas harvested for aboveground biomass. Using a
flat blade shovel, the 0.25 m2 area of peat was removed to a depth
of approximately 30 cm. This depth appeared to include nearly all
of the live root biomass. On April 25, 1978, June 25, 1978, September
18, 1978, and February 17, 1979, all of the 0.25 m2 areas harvested
for aboveground biomass were harvested for belowground biomass as
well.
All harvested above and belowground biomass was returned immedi-
ately to the laboratory where it was stored at 10C. Aboveground
plant material was separated into live and dead components as a
preliminary step. Prior to the April 15, 1978 sample live above-
ground biomass was separated by species and plant part. The separa-
tion categories were: 1. Sagittaria leaves; 2. Sagittaria stems; 3.
Pontedaria leaves; 4. Pontedaria stems; 5. Panicium and other grasses;
6. Hibiscus leaves; 7. Hibiscus wood; 8. unidentifiable herbaceous
material; and 9. unidentifiable woody material. Dead material was
separated into: 1. dead herbaceous and 2. dead wood. Beginning with
the April 15, 1978 harvest, the categories used for separation were :
1. live herbaceous excluding grass; 2. live grass; 3. live wood; 4.
dead herbaceous; and 5. dead wood.
Collected root samples with associated peat were immediately
transported back to the laboratory and stored at 10C prior to wash-
ing. The samples were washed gently with tap water over a 1 mm
nylon-mesh screen to remove the finely divided peat enmeshed in the
roots. All root material that did not pass through the screen was
included in subsequent weight and nutrient measurements. For the
June 25, 1978, September 18, 1978, and February 17, 1979 harvest,
roots were given preliminary washing with municipal fresh water in
the field. This preliminary washing removed the bulk of the weighty
peat, thus simplifying transport. No separation of live from dead
roots was attempted in this study, as there was no simple, clear-cut
method available for distinguishing between these two categories.
Thus, each root sample represents both live and dead roots, and
29





includes all tubers, rootlets, and fine roots that did not pass
through the 1mm mesh screen.
Both belowground and aboveground plant materials were dried in a
forced draft oven for at least 72 hours until no further weight
change was observed. Root samples generally required more drying
time than aboveground materials due to the lower surface to volume
ratio of tubers. Dried samples were weighed immediately upon removal
from the drying oven to preclude weight gain via absorption of atmo-
spheric moisture.
All aboveground categories and belowground stock for each
quadrat were individually ground and subsequently analyzed for nitro-
gen and phosphorus content. Representative subsamples consisting of
approximately 25% of the total root biomass from each sampled quadrat
were ground, rather than grinding the entire root sample. All ground
samples were stored in covered styrofoam cups prior to nutrient anal-
ysis.
Nitrogen analyses of biomass were performed using acid digestion
followed by micro-Kjehldahl steam distillation (Jackson 1962, as
modified by the School of Forestry, University of Florida,
Gainesville). Three milliliters of concentrated sulfuric-acid were
added to 0.1 g of sample and a catalyst consisting of 10 g K2S04
and 0.3 g CuSO4. The mixture was boiled in a 30 ml Kjehldahl flask
until all the sample was dissolved by the acid. The contents of the
flask were then brought up to 30 ml with distilled water. Two 5-ml
subsamples, each amended with 4 ml of 40% KOH solution, were
distilled on a Kjehldahl apparatus into boric acid indicator
solution. The indicator solution was subsequently titrated with 0.01
N HC1. The total phosphorus concentration in the plant materials was
analyzed by a procedure developed at the School of Forestry,
University of Florida. A 1 g sample of dried plant material was
ashed for 8 hours at 550C. Three milliliters of concentrated
hydrochloric acid (HC1) were added to the ashed sample, which was
dried at 90C. One milliliter of 6.25 N HC1 was added to the dry
sample and the volume of the sample was brought up to 25 ml with
deionized water. This sample was filtered through a #42 Whatman
filter. The concentration of phosphorus in the sample was determined
by the ascorbic acid method as described in APHA (1976).
30





Net annual aboveground production was defined in this study as
the peak aboveground live standing crop measured during the growing
season. Estimates of aboveground production using peak live standing
crop data will be lower than estimates made using other methods.
This is so because plant mortality, herbivory, and respiration of
plants use production before it can be measured (Odum and Odum 1976;
Westlake 1963). Any tissues that develop after the peak harvest are
likewise not included in this production estimate. If different
species present in the marsh attain their peak biomass at different
times during the year, the peak value for total biomass of all
species combined will necessarily be lower than the sum of individual
species' true peak values (Whigham et al. 1978). Despite these
factors, the net production values derived from peak biomass provided
a useful indicator of the effects of treated wastewater input on
growth in the marsh and of the net amounts of nutrients removed by
live vegetation growth during the year.
Decomposition Measurements
During the first year of this study, three sets of approximately
50 litter bags, each containing freshly cut Sagittaria stems, Sagit-
taria leaves, and Panicum grass, respectively, were spread out in an
undisturbed area of the marsh site. Five bags from each set were
returned immediately on the date of set placement in the marsh.
These were dried in a forced-draft oven at 70C for 72 hours and
weighed to obtain average percent moisture content. Subsequently,
they were ground in a Wiley Mill and analyzed for average initial
total phosphorus and nitrogen content, using the previously described
methods for analysis of phosphorus and nitrogen in vegetation.
Subsets of five bags each from the three sets were collected at
intervals and returned to the lab. Initially, litter bags were
collected every two weeks. After December 3, 1977, bags were
collected less frequently. A summary of the sampling schedule for
biomass, water, litter bags, and soil is given in Table 2. Returned
bags were dried, weighed, and analyzed for total phosphorus and
31





Table 2. Summary of sampling dates for biomass, water samples,
peat soil, litter bags, water level, and rainfall
in the marsh.
Type of Sample Sample Location Sampling Dates
00
N b I_ 00 co 00 cO r' an
CO
o '- i n On ) nO O r- -
- CO J C
tD 10 00 CJ. k O C-
BIOMASS
Aboveground
live and dead Plot C Inside x x x x x x x x x x x x
Outside x x x x x x x x x x x x
Plot L Inside x x x x x x x x
Outside x x x x x x
Plot M Inside x x x x x x x x x x x x
Outside x x x x x x x x x x
Plot H Inside x x x x x x x x x x x x
Outside x x x x x x x x x x x x
Belowground Plot C Inside x x x x x x
Outside x x x x
Plot L Inside x
Outside
Plot M Inside x x x x x
Outside x x x x x
Plot H Inside x x x x x x
Outside x x x x
32





Table 2 Continued.
PEAT SOIL
CO 0C3 O
NO N- N-
Plot C Inside x x x
Outside x x
Plot M Inside x x
Outside x x
Plot H Inside x x x
Outside x x
Natural Marsh x x x
DECOMPOSITION
N- N- N -- N-- N- N- N a>o o- co
C0 N Lo O O C\j 0 CM LOn
C r-- C'l C i-
Fresh-Cut Plant Litter Bags r co c 0 c-J -
Sagittaria x x x x x x x x x
Panicum x x x x x x x x x x x
00
oo c co
-O O .0 Co
Dead Biomass Litter Bags i oo o -
Plot C x x x x x x
Plot M x x x x x x
Plot H x x x x x x
33





Table 2 Continued.
WATER
SAMPLES
N~ r-- N>-^ CO CO CO CO CO N-rh r-^ N- O o.cM 0o Co
rSr-~p-~r~ I_^ rNr^ oo oo oo0 oo r~ co r_ 00 a~ o -. r rm i~^ i~- ro->
-^ r O r. L N '- r ~~ r -ss.rcj o ,- - >- O N- --CO
_-CIOJ C CO C- .- 0 ni ~ COMO v-_ _- i
kO O CO CO Li-i-. O .o CO o r- '
Medium
Depth
Wells x x x x x x x x x x x x x x x x x x x x x x x x
Deep
Wells x x x x x x x x x x x x x x x x x x
River x x x x x x x x x x x x x x x x x x x x x x x x
Surface
Water x x x x x x x x
Treated Wastewater--------------------(Monthly Composites)--------------------
34





Table 2 Continued.
WATER LEVEL RECORDERS
on
Plot C Continuously
Plot H
Natural Marsh _
RAIN GAUGE
0o
,_ co M
)- cj c
mI 1-- laji
aDaily measurements of rainfall collected by treatment plant personnel were
utilized for the period 12/27/79 3/28/79.
35





nitrogen content as described above. Average dry weight remaining,
average total phosphorus and nitrogen concentration, and average
fraction of initial phosphorus and nitrogen content remaining were
computed for each group for each collection date. Rates of decompo-
sition were then derived from the weight loss values.
During most of the second year of this study, the water table
in all areas of the marsh was above the surface of the peat. Rates
of decomposition were expected to change for each species under wet
vs. dry conditions and to vary between control and treated wastewater
plots. In order to obtain an average rate of decomposition for
litter derived from the whole range of species in each plot, subsam-
ples of the aboveground dead material harvested on June 25, 1978,
were placed in 1 mm mesh nylon litter bags. Six sets of six bags
were derived from the litter harvested in each of Plots C, M, and H.
Each six-bag set contained one litter subsample from each of the six
0.25 m2 areas harvested on June 15, 1978. The bags were placed in
the marsh on July 6, 1978. In each case bags were returned to the
plot where their litter was harvested. One of the sets from each
plot was returned immediately to the laboratory on July 6, 1978, and
analyzed for average moisture content and total nitrogen content by
the methods described above for the first year's decomposition study.
Litter bag sets were subsequently collected on the dates shown in
Table 2. Each sample was analyzed for dry weight loss, total
nitrogen concentration, and fraction of original nitrogen content
remaining.
Peat Soil Measurements
Core samples of the peat substrate were taken from several loca-
tions in the marsh on the dates shown in Table 2. The cores were
obtained using a post hole digger with blades 0.25 m long; the resul-
tant core was 0.125 in. in diameter. Samples were obtained for the
depth intervals: 0-25 cm, 25-50 cm, 50-75 cm, and 75-100 cm. After
March 20, 1978, the 75-100 cm core was excluded at each sampling
location. On March 20, 1978, cores were taken at four randomly
36





chosen locations in the inside regions for each of Plots C, L, and H.
Four coring stations were also randomly chosen from a natural area of
the marsh, north of the experimental plots. On September 15, 1978,
and February 17, 1979, during biomass harvest, cores were taken
within 1 m of each of the 0.25 m2 areas harvested. Subsamples of
approximately 100 g each were obtained from the central portion of
each of the cores for each depth interval. These were dried in a
forced-draft oven at 70C for at least 72 hours, until no further
weight loss was observed. Dried peat samples were ground into fine
powder using a mortar and pestle, and then sifted through a 1 mm mesh
nylon screen. Rhizomes and large roots were trapped by the screen.
The powdered peat that passed through the screen was analyzed
for total nitrogen content via acid digestion and subsequent micro-
Kjehldahl steam distillation. As with the biomass samples, 0.1 g of
powdered peat soil was used in the nitrogen analysis. The same anal-
ysis procedure was used for both peat and biomass samples. Peat in
this marsh was found naturally to contain large quantities of nitro-
gen, which obscured any possible differences in nitrogen content due
to treated wastewater application. Adsorption of ammonium onto the
cation exchange sites of the peat was subsequently investigated. The
full set of cores obtained on September 18, 1978, and February 17,
1979, was analyzed for exchangeable ammonium using the KC1 extraction
technique described in Black (1970). Two 100 g subsamples were
obtained from each of the cores for each depth interval. One of the
subsamples was dried in a forced-draft oven at 70C for at least 72
hours, until no further weight loss was observed. Percent moisture
content of the wet peat sample was calculated from the observed
weight loss. The remaining 100 g subsample was shaken mechanically
for one hour with 100 ml of 2 N KC1. Suspended peat was then
filtered out using Whatman #4 (fast) filter paper. The filtrate was
analyzed for ammonium using the MgO method of micro-Kjehladahl steam
distillation (Black 1970). Filtrate was stored in plastic vials at
10C prior to analysis. The 100 g subsamples from September 18, 1978
cores were frozen for storage, prior to KCl extraction. The 100 g
37





subsamples from February 17, 1979 cores were stored at 10C prior to
KC1 extraction.
The total phosphorus concentration of the peat soil was deter-
mined by the use of a procedure developed at the Soil Science Depart-
ment, University of Florida. A 1 g sample of dried soil was dried at
550C for eight hours. Five milliliters of concentrated HCl were
added to the ashed sample. The samples were then dried at 70C. The
volume of the sample was brought up to 25 ml by the addition of 0.1 N
HC1 and vigorously shaken. The sample was filtered through a Whatman
#42 filter. The phosphorus concentration of the sample was deter-
mined by the ascorbic method as described in APHA (1976).
The potential adsorption capacity of the peat soil for phos-
phorus was measured via adsorption isotherms. Two sets of isotherms
were performed on soils representative of the natural marsh at vary-
ing depths (0-25, 25-50, 50-75 cm). The first isotherm was a time
study to determine solution/soil equilibrium times. The second study
entailed adsorption of varying concentrations of orthophosphate.
The soils were ground in a blender to create a relatively homo-
geneous sample. These samples were then autoclaved to reduce biolog-
ical activity within the soil. After autoclaving, samples equivalent
ot 0.4 g dry soil were placed in 250 ml Erlenmeyer flasks.
Phosphorus solutions of varying concentrations and composition
were autoclaved to create sterile conditions. The concentrations
for orthophosphate were 6.3, 12.6, 57.3, 87.3, and 110.7 mg/l. The
pH of each solution was adjusted to 7.0 with 0.2 N NaOH. This pH
was representative of the surface water pH in each of the experi-
mental plots. After pH adjustment, the conductivity of each solution
was adjusted to 670 mhos/cm with saturated KC1 to eliminate any ionic
strength inequalities caused by variation in phosphorus concentration
and NaOH addition.
The isotherm tests were conducted by adding 40 ml of the
prepared phosphorus solution to the wet soil previously placed in
the 250 ml Erlenmeyer flasks. The soil-water samples were sealed
with parafilm and shaken continuously for 48 hours, which had been
38





determined to be the time necessary to reach equilibrium. After 48
hours, the samples were removed from the shaker table and filtered.
Filtration took place in two steps; the sample was passed through a
Whatman qualitative filter and the filtrate was subsequently passed
through a 0.45 mm filter. The filtrates were evaluated for phos-
phorus by the ascorbic acid method outlined in standard methods (APHA
1976). The percent adsorption was determined by calculating the
difference between initial phosphorus concentration and the 48- hour
concentration.
Nitrification and Denitrification Studies
Preliminary Nitrification Studies in Marsh Water
Marsh surface water collected at Clermont was incubated at
25C for 30 days. Half of the samples were amended with ammonium
(as ammonium sulfate) to a concentration of 25 mg/l NH4-N. Half
of the amended and unamended samples were aerated after the air was
humidified by pumping through 400 ml deionized water in a 500 ml
Erlenmeyer flask to reduce evaporation. The humidified air was
routed to the individual replications by a network of tygon tubing
and syringe needles (Fig. 10). Twenty-five-milliliter samples were
taken periodically for analysis. Dissolved oxygen was determined
immediately, and phenyl mercuric acetate (PMA) was added to prevent
microbial growth. The samples were stored at 4C until pH, ammon-
ium, and nitrate were determined.
The second study compared nitrification in water from Lake
Alice on the University of Florida campus to standing water in the
experimental marsh. Yellow-colored, dissolved organic compounds,
commonly called tannins, were removed from half of the marsh water
by adding powdered, activated charcoal, mixing for one hour, and
filtering through a Whatman #42 filter paper. A suspension of nitri-
fiers was obtained by shaking a mixture containing 100 g of soil
known to contain nitrifiers with 150 ml of water for one hour and
allowing the soil to settle out. Ten-milliliter aliquots were used
39





N H4 AMENDED UNAMENDED
STILL AERATED AERATED STILL
o
o
40
o'" AIR
\0 A LPUMP
HUMIDIFIER
Figure 10. Experimental design for preliminary nitrification
study.
40





as nitrifier inoculum for half of the filtered samples and for half
of the unfiltered samples. Twenty-milliliter samples of each treat-
ment group were stored and analyzed as described previously.
Preliminary Denitrification Studies
Initial laboratory studies using test tubes of nitrate-amended
solutions and marsh soil were designed to ascertain if denitrification
was occurring. Solutions of calcium nitrate in deionized water and
potassium nitrate were made in deionized water, in oxidation pond
water from the Clermont sewage treatment plant, and in marsh water
(standing water in the experimental marsh prior to the plots' exis-
tence). A 10-ml aliquot of each solution was gently added to a test
tube (eight replications) containing 6.0 + 0.2 g marsh soil obtained
in bulk from the experimental marsh and incubated at 25C for 11 days.
The same design without the soil was also employed to see if denitri-
fication would occur in the water alone. Sampling involved gently
pouring off the solution and analyzing it for ammonium and nitrate.
Nitrification and Denitrification Studies
Using Soil:Water Columns
In order to better simulate actual marsh conditions, additional
experiments for both nitrification and denitrification were conducted
using intact soil:water columns. Intact soil columns, half with and
half without Sagittaria lancifolia were obtained from randomly
selected sites outside plots in the experimental marsh area. The
columns were 70 X 10 cm diameter PVC pipes, which were sealed at the
bottom with knockout test caps (Fig. 11) after obtaining 45 cm of
soil. Once in the lab, the columns were placed in wooden racks and
allowed to stand for stabilization for two to four weeks while receiv-
ing only enough deionized water to keep the soil saturated. (Those
containing plants were placed under a window.) Several days before
a study began, those columns that required lime received 10.0 g
41





a-V~~~~~~~ A~yAIR
PUMP
HUMIDIFIER
TREATMENT 0 0
AIR STONE
RHIZOME
*.:; _*4\\^^ ,^> 0 ROOTS
'SOIL ;''..:.
Figure 1. Experimental setup for nitrification and denitrification
studies using soil:water columns.
42





powdered CaC03 applied to the surface of the soil. (The lime dosage
was calculated using Yuan's (1974) double buffer method to bring the
top 15 cm of soil to a pH of 7.0.) Treatments in the nitrification
and denitrification studies were the same and involved the water
level overlying the soil (Fig. 11). The following treatments (two
replications) were used with and without plants: 1. Control; treated
wastewater to 15 cm depth. 2. Water depth 15 cm; treated wastewater
to a 15 cm depth. 3. Water depth 30 cm; treated wastewater to 30 cm
depth. 4. Fluctuating water depth; treated wastewater to 30 cm depth,
empty (0 cm) for two weeks, after which fresh treated wastewater
reapplied to a 30 cm depth. 5. Water depth 15 cm, pH adjusted;
treated wastewater to a 15 cm depth over 10 g CaC03.
In all cases, water lost by evaporation and transpiration was
replaced two to four times weekly by adding deionized water to main-
tain the appropriate depth. Columns were aerated in a manner similar
to that described for the previous nitrification study. About 15 ml
of the overlying water in the columns was sampled at mid-depth, i.e.,
7.5 and 15 cm, respectively. PMA was added and the sample was stored
at 4C until ammonium, nitrate, and pH were determined, usually
within 24 hours.
In the nitrification study, ammonium was added to the treated
wastewater obtained from the Clermont sewage treatment plant as ammo-
nium sulfate. In the denitrification study, nitrate was added to the
treated wastewater as potassium nitrate. Ammonium and nitrate were
added to appropriate columns at least once more in column studies.
The second and third application of the appropriate form of nitrogen
was added as a more concentrated solution to the individual soil:-
water columns without changing the treated wastewater except in the
fluctuating columns.
Ammonia Volatilization Study
In order to quantify volatilization of ammonia during column
studies, another soil:water column experiment was conducted.
43





Columns were packed with 30 cm of marsh soil (no plants), and 30 cm
of ammonium-amended treated wastewater was added. The columns (four
replications) were sealed at both ends with knock-out test caps and
aquarium seal. Air going into the columns was bubbled through a
boric acid indicator solution to scrub off any atmospheric ammonia
and humidify the incoming air. Air leaving the columns was forced
through a boric acid indicator (in test tubes) to trap any volatil-
ized ammonia. Care was taken to prevent contact of tygon tubing
with the boric acid indicator solution since it was found that the
indicator solution reacted with tygon. The boric acid was titrated
and replaced after 1, 3, 7, and 20 days and the column water was
analyzed at the beginning and end of the study for pH, ammonium, and
nitrate.
In Situ Nitrification and Denitrification Studies
For the purpose of obtaining natural nitrification and denitri-
fication rates an in situ study was conducted. Eno (1960) and more
recent work by Struble (1977) found polyethylene bags acceptable for
this type of study due to their permeability to gases, specifically
oxygen and carbon dioxide, and impermeability to ions such as
nitrate and ammonium. Polyethylene bags were filled with 100 g
marsh soil and subjected to the following treatments:
1. Control, shallow; soil in bags buried in top 8 cm.
2. Control, deep, lime; soil plus lime in bags buried at 30
cm.
3. Nitrification, shallow; soil amended with ammonium in bags
buried at 30-cm depth.
4. Nitrification, deep; soil amended with ammonium in bags
buried at 30-cm depth.
5. Denitrification, shallow; soil amended with nitrate in
bags buried in top 8 cm.
6. Denitrification, deep; soil amended with nitrate in bags
buried at 30 cm depth.
44





7. Denitrification, deep, lime; soil amended with nitrate
plus lime in bags buried at 30-cm depth.
Bags were flattened to maximize surface area and heat sealed.
Nitrification bags were amended with ammonium as ammonium chloride
to bring the final concentration to about 35 mg/1 NH4-N. The
denitrification bags were similarly amended with nitrate as potas-
sium nitrate. Control bags received no nitrogen. Lime used in all
cases was 0.85 g of finely powdered calcium carbonate per bag, which
was the amount extrapolated from an earlier application of Yuan's
double buffer method and was intended to bring the pH of the soil to
7.0.
Bags were retrieved at selected intervals. Temperature, pH,
and dissolved oxygen readings were taken at each site. After the
bags were removed, the sample pH was determined, and the contents
of each bag were extracted. The extractant was analyzed for ammo-
nium and nitrate.
Microbial Studies: Total, Nitrifying,
and Denitrifying Populations
Shallow soil samples (top 8 cm) were taken in areas with dense
root growth as well as areas with lesser root growth to determine
qualitatively the rhizosphere effect on total bacteria, autotrophic
nitrifier, heterotrophic nitrifier, and denitrifier populations.
Similar analyses were done on rootless soil samples taken at about a
30 cm depth.
Microbial populations from the shallow and deep samples were
further compared with populations existing after 27 days of in situ
incubation in polyethylene bags. This was accomplished by composi-
ting 2 g wet weight subsamples from each of the three replicates of
the following treatments: 1. Control, shallow; total and deni-
trifiers; 2. Control, deep, lime; total and denitrifiers; 3. Deni-
trification, deep; total and denitrifiers; 4. Nitrification, shal-
low; total and heterotrophic and autotrophic nitrifiers. A single
45





2 g wet weight subsample of each treatment was used for each popula-
tion type. A pooled 10 g wet weight sample was used in the natural
marsh studies for plating, 2 g for each of five samples.
Since available carbon is often a factor in bacterial popula-
tion growth, extractable carbohydrates were determined on duplicate
samples from the natural marsh (shallow with roots and deep without)
as well as from the polyethylene bag study (control, deep, lime).
Analytical Methods for Nitrification-Denitrification Study
Ammonium and nitrate plus nitrite determinations were done by
steam distillation as described by Bremmer and Keeny (1965) and
involved collection of the distillate in boric acid indicator and
subsequent titration with H2S04 solution. An Orion 701 or 401
meter was used to measure pH, in conjunction with a Fisher combina-
tion pH electrode. A YSDL model 54 Oxygen meter with a YSI model
5419 probe was used to determine concentrations of dissolved oxygen.
Ammonium, nitrite, and nitrate were extracted from the soil in
the polyethlylene bags in the in situ study by transferring the 100
g of wet organic soil into a polyethylene sample bottle, adding 100
ml of 2 N KC1 solution, shaking briefly and then allowing the suspen-
sion to stand for two hours. The mixture was shaken again before
filtration through a Whatman #40 filter and finally stored with PMA
at 4C until inorganic nitrogen was determined (Bremner 1965).
The total soil bacterial population count was determined by a
dilution plate technique with five plates per 10-fold dilution on a
tryptone, glucose yeast agar (TGY) as developed by Ou et al. (1978).
The dentrifier population was determined by the most probable number
method of Focht and Joseph (1973) and the autotrophic nitrifiers by a
similar method described by Alexander and Clark (1965). The hetero-
trophic nitrifier population was estimated by a method adapted from
Tate (1977) and involved subculturing 100 randomly selected colonies
from the total bacterial count plates into Difco nutrient broth
amended with ammonium sulfate at 0.5% The available organic carbon
was quantified as extractable carbohydrate in a two-step process.
Five grams of oven-dry soil were treated with 50 ml of 0.02 M
46





CaC12 at 100C for one hour and then filtered through a Whatman #40
filter paper (Stanford, 1975). One milliliter of the filtrate was
used in the anthrone method of total carbohydrate determination
(Loewus, 1952; Morris, 1948).
47





RESULTS
Characteristics of the Peat Soil
Moisture Content, Organic Matter Content, and Bulk Density
The peat soil of the research marsh was approximately 1.5 m in
depth. Down to a depth of 75 cm the peat was matted, coarsely
fibrous, and generally brown in color. Below 75 cm the color of the
soil turned brown-black and became more finely fibered. The darker
color at the greater depth possibly indicated a higher degree of
decomposition (Davis and Lucas 1959).
The moisture content, weight loss on ignition, and the bulk
density of peat samples is shown in Table 3. The moisture content
represents the amount of water bound in the soil complex. There was
no large variation in the moisture content from the surface to the
1 m depth. Approximately 90% of the wet weight of the peat soil was
water. The weight loss on ignition values are estimates of the total
organic content of the soil. Successive increases in bulk density
were found in the 0-25, 25-50, and 50-75 cm depth intervals. These
results indicate that each cubic meter of the peat soil contains
approximately 930 kg of water and 70 kg of dry matter.
Davis (1946) provided extensive physical data for Florida
peats. The peat of the marsh research site generally had greater
quantities of organic matter than most of the Florida peats. The
average organic matter content of Everglades peat from Broward
County was 74%. The average organic matter content of the upper 75
cm of the Clermont peat was 89%. This greater organic matter
content may reflect the low sediment loading from the Palatlakaha
River. Lower organic matter values are found in those peats
underlying streams or lakes which contain a high sediment load. The
moisture content of the Clermont peat was also generally higher
48





Table 3. Three physical characteristics of the peat soil: moisture
content, weight loss on ignition, and bulk density. Samples
were collected from an undisturbed portion of the research
marsh. Mean + Standard Error, sample size = n.
Depth Moisture n Weight n Bulk Density n
(cm) Content, Loss on (g dry matter/cm )
% Ignition
November 1977
0-25 89.0+0.6 6 81.7+1.2 8 0.060+0.005 4
25-50 92.0+0.2 6 88.5+0.6 8 0.070+0.002 4
50-75 91.2+0.6 6 93.5+0.9 8 0.082+0.003 4
75-100 86.0+0.4 6 72.6+3.1 8 --
July 1978
0-25 90.7 6 88.1 3
25-50 91.5 6 88.3 3---
50-75 90.6 6 91.9 3
49





than that measured for other Florida peats. Both the organic matter
content and the vegetation type are important in determining a
peat's water-holding capacity.
Specific Yield
The specific yield of the peat soil was measured through
paired observations of rainfall volume and water table rise (see
Methods). Water level recorders in Plots C and H were utilized
for these observations. A paired t-test indicated that the water
table rise per rainfall event was significantly higher (a= .05) in
Plot C than in Plot H. The results for Plot C and Plot H were
plotted separately (Figs. 12 and 13). A significant linear
relationship was found between the water table rise per rainfall
event and the depth to the water table in Plot C and Plot H. The
water table rise per centimeter of rainfall increased as the depth to
the water table increased. This result was consistent with the
finding that the density of the soil increased with depth. With less
pore space at the deeper soil depths a centimeter of water fills up a
greater volume of the soil.
The inverse of the water table rise per rainfall event observa-
tions represents the specific yield of the soil. Table 4 shows
representative specific yield values based upon the water table
rise per rainfall event correlations. The specific yield decreases
with depth. The major differences between the specific yield
values for Plot C and Plot H were evident in the upper 10 cm of the
soil profile. The specific yield at the top of the soil was not
equal to 1.0 due to the presence of dead and live plant matter, which
occupied volume and depressed the specific yield values until the
water table was several centimeters above the ground surface. The
lower specific yields found near the surface in Plot H as compared to
Plot C possibly were a consequence of the larger aboveground and
belowground biomass of Plot H.
50





8-
2a~ ~7- R = .10 x D + 1.21
r2 = .89
z
n-
w 4-
4
a 3--
I-
<
2-
3 /
O- I I l I I .
-10 0 10 20 30 40 50 60
DEPTH TO WATER TABLE (D), cm
(b)
'-Figure-.12. Ratio of water table rise to rainfall, event versus the depth to the
water table in'Plot C (4.4 cm/wk freshwater). The straight line
represents the least squares regression equation.





8-
7-
z R = .08 x D + 1.49
w
> 6- 2=.94
w
-J
I4-
- .-
I-
-10 0 10 20 30 40 50 60
DEPTH TO WATER TABLE (D), cm
(a)
Figure 13. Ratio of water table rise to rainfall event versus the depth to the
water table in Plot H (9.G cm/wk treated wastewater). The straight line
represents the least squares regression equation.





Table 4. Representative specific yield values for Plots C and H.
Values were calculated from water table rise per rainfall
event and depth to water table observations.
Water Table Specific Yield
Depth (cm) Plot C Plot H
0 0.83 0.67
10 0.45 0.44
20 0.31 0.32
30 0.24 0.26
40 0.19 0.21
50 0.16 0.18
53





Hydrologic Considerations
Seasonal Water Table Fluctuations and Hydrologic Inputs
Water table elevations. The water table elevations from the
recorders in Plots C and H are presented in Fig. 14. Except for a
short period in August and September the water table was below the
peat surface for the entire growing season of the first year. During
the winter months of the first year, the water table rose to the
surface or slightly above the surface, and remained near or above
the surface of the peat from mid-July of the second year through the
end of the study. The water level record of Plot C tracked very
closely to the water level record of Plot H over the entire study.
There are no major differences between the seasonal water table
elevations in Plot C and Plot H.
Long-term hydrographic records of Lake Minnehaha are shown in
Figs. 15 and 16. This lake is located near the experiment site (see
Fig. 2). The stage-duration curve for Lake Minnehaha (Fig. 15) was
computed from average daily water levels. The curve indicates that
lake levels near the experimental marsh were above the present aver-
age peat surface roughly 82% of the time between June 1945 and
September 1964. Thus "dry" conditions prevailed 18% of the time,
assuming no appreciable changes in peat depth over that time inter-
val. Average yearly water levels for Lake Minnehaha (USGS 1979) are
shown in Fig. 16 for 1946-1978. It should be noted that after 1959,
a dam regulated outflow from the chain of lakes, including Lake
Minnehaha. Apparently the water surface was generally above the
experimental marsh peat surface both prior to and after the
installation of the dam. Thus "wet" conditions have prevailed more
often than "dry" conditions in the marsh over the past thirty
years.
Hydrologic inputs. Rainfall data, including historical aver-
ages for north central Florida, are shown in Table 5. Rainfall was
58% lower than the historical averages during the interval February
to July 1977. The water table of the marsh was belowground during
this interval. The rainfall was also low during September and Octo-
ber of 1977, which was reflected in the marsh water table record.
54





29.6
1977 1978 1979
29.4
E WATER TABLE PLOT C
29.2 / -
W 29.0
<28.8 _
z
< 28.6 r
u 28.4 _
. i I I I I I i I i I I I I I I I ... i
,1 ^ c A N D J F M A M J J A S O N D J F M A M
9 29.6 I -----
1977 1978 1979
E 29.4-
;- WATER TABLE PLOT H
29.2 -
> 29.0 -
z 28.8-
z2.- / \/ \ -o PEAT SURFACE
> 28.6
J
\/'
28.4
J J A S O N D J F M A M J J A S O N D J F M A M J
Figure 14. Seasonal water table elevations in Plot H (9.6 cm/wk of treated wastewater) and Plot C
(4.4 cm/wk of fresh water).





6 30.00
29.75
w
a
O
E
x 29.25 -
29.00
a AVER AGE M ARSH SURFACE
w _- --_ __- _
w
' 28.75.X
o 28.50
0
> \
w 28.25
_j
w
O 10 20 30 40 50 60 70 80 90 100
PERCENT OF TIME
Figure 15. Stage-duration curve, Lake Minnehaha, Lake
County, June 1945 September 1964. (Adapted
from Bishop 1967).
56





29.8
29.6
29.2
< 29.0
AVERAGE MARSH SURFACE
cn^j 28.8 -
' 28.6 -
28.4
1948 1952 1956 1960 1964 1968 1972 1976 1980
YEAR
Figure 16. Mean annual water level elevations in Lake Minnehaha, 1946-1978.
Data obtained from USGS (1979).





Table 5. Historical monthly rainfall averages for north central Florida,
observed rainfall in north central Florida, and observed rainfall
in the research marsh. All values are expressed as cm H20.
Month Historical North Central Research Marsh
Average Florida Observed
(cm) Observeda (cm) (cm)
January 1977 6.1 9.1 7.5a
February 7.8 7.2 5.2a
March 9.9 3.7 4.2a
April 7.0 1.1 0.4a
May 8.0 4.6 2.1
June 17.9 7.6 5.5
July 20.8 17.4 21.8
August 19.5 22.4 16.2
September 18.4 16.6 13.9
October 10.7 2.9 2.:8
November 4.6 7.7 8.2
December 5.6 10.1 10.4
January 1978 6.1 9.7 7.2
February 7.8 14.9 14.9
March 9.9 8.9 6.6
April 7.0 3.2 1.8
May 8.0 10.0 14.4
June 17.9 18.6 27.6
July 20.8 24.8 32.8
August 19.5 14.5 6.5
September 18.4 8.6 7.9
October 10.7 4.8 4.6
November 4.6 0.3 0.0
December 5.6 10.9 8.9
January 1979 6.1 16.1 17.8
February 7.8 5.6 5.0
March 9.9 8.7 10.0
April 7.0 13.3
303.4 277.5
a Reference, NOAA 1977, 1978, 1979. The North Central Florida values
are an average of 14 stations in this region.
58





During the winter months of 1977-1978, with lower evapotranspiration
and above average rainfall, the marsh water table was near the
surface. The rainfall observed directly in the research marsh was
typical of the north central Florida observations during the first
year of the study.
Rainfall in the marsh was below average in March and April of
1978 and the water table dropped at this time. In June and July of
1978 rainfall was considerably higher than either the historical
average or the concurrent north central Florida average. During this
time the surface water rose to a height of approximately 0.4 m above
the surface of the peat in the marsh. The marsh water surface became
contiguous with the channel and lake surface water during this
period. For August through November 1978, rainfall was below the
historical average. The water table was observed to fall between
September and December 1978 to a level near the surface of the peat.
Above average rainfall for December 1978 through April 1979 caused
the water table to rise once more, to a height of approximately 0.2 m
above the peat at the termination of the study.
Rainfall and water table elevations were below normal in 1977,
with the period May 1977 April 1978 being designated as a "dry
year" for this study. In 1978, rainfall and water table elevations
were average compared with the long-term mean. The period May 1978 -
April 1979 was designated as a "wet year" for comparitive purposes,
since the water table was above the peat surface after June 1978.
The input of treated wastewater or fresh water to the experi-
mental plots is shown in Table 6. Wastewater or fresh water inputs
represented 385% and 175% of rainfall input to Plots H and C, respec-
tively, during the period May 1, 1977 April 31, 1979. Treated
wastewater monitoring for Plots L and M was discontinued after
September 1978.
Evapotranspiration
Evapotranspiration from the research marsh. Empirical esti-
mates of evapotranspiration were calculated for the first 13 months
of the study using the diurnal water table fluctuations as described
59





Table 6. Quantities of treated wastewater and fresh water applied to
experimental plots. All values expressed as cm H20.
Month Plots
C L M H
(cm fresh water) (cm wastewater) (cm wastewater) (cm wastewater)
May 1977 15.3 5.1 15'.3 41.5
June 19.8 6.4 19.3 50.9
July 15.5 5.2 15.2 40.7
August 15.8 5.1 15.2 49.6
September 19.1 6.4 19.3 51.1
October 18.8 5.1 15.0 42.2
November 14.9 5.1 15.2 41.2
December 19.2 6.4 19.3 50.9
January 1978 15.2 5.1 15.2 40.7
February 15.2 5.1 15.2 40.7
March 15.4 5.1 15.4 21.8
April 15.4 5.1 15.4 41.4
May 21.7 13.6 25.0 46.2
June 16.0 15.1 5.0 45.9
July 15.4 5.1 15.4 41.1
August 19.3 6.4 19.3 51.3
September 15.4 5.1 15.4 41.1
October 15.4 -- --- 41.1
November 15.4 --- --- 41.1
December 15.4 --- 41.1
January 1979 15.4 --- --- 41.1
February 34.9 --- --- 32.7
March 34.9 --- 32.7
April 34.9 --- --- 32.7
60





in the Methods section. A paired t-test showed no significant
difference between the evapotranspiration rates calculated from each
recorder located in Plots C and H. Table 7 presents the average
monthly evapotranspiration values determined from May 1, 1977 April
31, 1978, and includes the combined data from both recorders. The
range of daily values found during each month is also shown.
Evapotranspiration was approximately 0.5 cm/d throughout the
growing season of 1977 (May through September). During late fall,
evapotranspiration began to decline and reached the lowest measured
values during January and February of 1978. Values rose through the
spring of 1978. An evapotranspiration rate of 1.0 cm/day was the
largest single observed value, and this value was recorded during
September 1977.
Model of evapotranspiration. A model of evapotranspiration
based on live aboveground biomass and saturation deficit was
constructed (see Methods). Figure 17 shows the plotted values of
evapotranspiration versus the biomass-saturation deficit product for
the first 13 months of the study. The months that exhibited the
highest rates of evapotranspiration cluster in the upper right-hand
corner of the figure. Both the saturation deficit and biomass were
high during June, July, August, and September of 1977, and during May
1978. In the lower left hand corner cluster those months with low
live biomass and low saturation deficits. Figure 17 also presents
the linear correlation (r2 = 0.79) between observed evapotranspira-
tion and the biomass-saturation deficit product for the first 13
months of the study.
A summary of measured evapotranspiration of the natural marsh
area, saturation deficit, estimated aboveground live biomass of the
natural marsh area, and theoretical evapotranspiration derived from
the model, is shown in Table 8. As discussed in the Methods sec-
tion, the model derived from the first year's data was applied to
biomass and saturation deficit data over the entire two-year study
period. Respective data for live biomass in Plots C and H over the
entire two-year period were applied to get separate theoretical
61





Table 7. Empirical estimates of monthly evapotranspiration rates in the
marsh. Values are derived from the combined records of the
water level recorders in Plots C and H. Values expressed as
cm/day.
Month Mean Evapotranspiration Range n
Rate (cm/day)
May 1977 0.42 0.31-0.69 16
June 0.49 0.30-0.76 28
July 0.58 0.39-0.95 19
August 0.48 0.19-0.78 18
September 0.52 0.21-1).00 22
October 0.36 0.14-0.56 26
November 0.22 0.10-0.33 15
December a ---
January 1978 0.11 0.07-0.18 5
February 0.12 0.05-0.18 9
March 0.26 0.09-0.57 18
April 0.45 0.17-0.69 36
May 0.65 0.42-0.84 16
aNo recorded evapotranspiration.
62





0.90
>
o
xX
E 0.80 E = 0.127 + (9.26 x 10 x B x S)
o ,~r2 = 0.79
Z
0 0.70-
o--0 MAY 78
F-
I 0
0.60-_ JUL 77
2Z SEP 77
cr 0.50- AU G
> 040- OC 77
w 77
wLI 0.30 MAR 78
t0- NOV 77
< 0.20
. 'JAN 78
W3 0.30
0.10 FEB
78
1000 2000 3000 4000 5000 6000 7000
BIOMASS X SAT. DEF.
Figure 17. Average monthly evapotranspiration versus the product of average live
aboveground biomass and average saturation deficit. The straight line
represents the least squares linear regression equation.





Table 8. Estimates of average daily evapotranspiration. A model of
the evapotranspiration process as a function of live above-
ground biomass and saturation deficit was used to estimate
the evapotranspiration. Values are expressed as g dry
weight/m2, g H20/m3, and cm/d. Values are monthly means.
Month Live Above- Saturation Estimated Observed
ground Biomass Deficit Evapotrans- Evapotrans-
(g/m2) (g/m3) pirationa pirationb
(cm/d) (cm/d) n
May 1977 277 10.9 0.41 0.42 16
June 310 13.1 0.51 0.49 28
July 346 10.0 0.44 0.58 19
August 433 8.5 0.47 0.48 18
September 443 11.5 0.62 0.52 22
October 344 9.9 0.45 0.36 26
November 241 8.2 0.31 0.22 15
December 156 5.8 0.21 -
January 1978 144 5.6 0.18 0.11 5
February 77 5.1 0.15 0.12 9
March 100 8.4 0.20 0.26 18
April 182 12.1 0.33 0.45 36
May 400 12.6 0.59 0.65 16
June 626 12.2 0.83 --- --
July 728 9.6 0.77 ---
August 773 10.1 0.85
September 819 10.9 0.95 ---
October 675 8.9 0.68 ---
November 505 9.3 0.56 ---
December 340 6.5 0.33 ---
January 1979 256 5.5 0.26 ---
February 171 5.8 0.22 ---
March 240 8.3 0.31 ---
April 329 12.1 0.50 -
aThe following equation was used to estimate evapotranspiration (E):
E = 0.127 + [9.26 x 10 5x (BxS)]
(BxS) is the product of mean biomass and average saturation deficit
for a given month.
bFrom Table 7.
64





estimates of evapotranspiration in Plots C and H for the entire two-
year period. Biomass and theoretical evapotranspiration estimates
for Plots C and H are shown in Table 9. The use of the same model
for both years was necessary since no empirical measurement of evapo-
transpiration using water level records was possible during the
second year, when the water table was above the peat surface.
Several factors affected the accuracy of the theoretical evapotran-
spiration estimate for the first year: 1. The empirical rate esti-
mates from which the theoretical model was derived were made using
water level records for clear, rainless days. Lower evapotranspira-
tion would be expected on rainy days, which experience a lower satu-
ration deficit and less solar insolation than clear days. 2. Varia-
bles such as wind speed, solar insolation, and depth of peat above
the water table probably affected evapotranspiration during the first
year. These factors were not included in the theoretical model.
During the second year, water levels were higher than during
the first year. Thus: 1. evaporation from a free water surface
occurred; 2. transpiration by duckweed, which grew in surface water,
contributed to water loss; 3. previously aerated roots were flooded,
possibly altering water loss by transpiration through rooted plants;
and, 4. the plots' outside region biomass, which was utilized in the
model to get theoretical evapotranspiration in the natural marsh
during both years, was probably influenced by applied water to a
greater degree during the second year than during the first year of
the study.
It is not possible to conclude whether actual evapotranspiration
during the second year was higher or lower than the value predicted
by the model for that year. If the actual evapotranspiration was
slightly higher than the predicted values during any time period,
then outflows of water with associated nitrogen and phosphorus were
slightly lower during that time period.
Water Storage and the Distribution of
the Applied Treated Wastewater
Water storage. The results of the water storage calculations
are presented in Table 10. A comparison of Plot H and Plot C shows
65





Table 9. Estimated evapotransporation in Plot C (4.4 cm/wk freshwater)
and Plot H ( 9.6 cm/wk effluent). The estimates are based upon
a biomass-saturation deficit-evapotranspiration correlation
analysis. Values are monthly means expressed as g dry weight/m2
and cm H20/d.
Plot C Plot H
Month Aboveground Evapotrans- Aboveground Evapotrans-
Live Biomass piration Live Biomass piration
(g/m2) (cm/d) (g/m2) (cm/d)
May 1977 285 0.41 290 0.42
June 339 0.54 380 0.59
July 339 0.44 576 0.66
August 504 0.52 649 0.64
September 576 0.74 777 0.95
October 430 0.52 599 0.68
November 279 0.34 415 0.44
December 167 0.22 269 0.27
January 1978 104 0.18 169 0.21
February 42 0.15 68 0.16
March 94 0.20 129 0.23
April 177 0.32 233 0.39
May 374 0.56 495 0.71
June 577 0.78 766 0.99
July 701 0.75 788 0.83
August 789 0.78 687 0.77
September 878 1.01 586 0.72
October 714 0.72 510 0.55
November 515 0.57 433 0.50
December 322 0.32 358 0.34
January 1979 356 0.26 281 0.27
February 190 0.23 203 0.24
March 241 0.31 263 0.33
April 307 0 47 341 0.51
66





Table 10. Monthly changes in water storage in the peat of Plot H (9.6
cm/wk treated wastewater) and Plot C (4.4 cm/wk fresh water).
Values are expressed as cm H20.
Plot H Plot C
Month Water Speci- Change Water Speci- Change
Table fic in Table fic in
Changea Yieldb Water Change Yield Water
(cm) Storage (cm) Storage
(cm) (cm)
May 1977 -7.3 0.24 -1.7 -6.0 0.21 -1.2
June -18.6 0.18 -3.4 -13.7 0.17 -2.3
July +41.5 0.27 +11.4 +31.4 0.26 +8.3
August +14.4 0.64 +9.2 +14.7 0.59 +8.5
September -4.9 0.70 -3.4 -4.9 0.63 -3.1
October -10.7 0.36 -3.8 -13.4 0.28 -3.8
November +21.4 0.37 +7.9 +21.4 0.28 +6.0
December +3.1 0.78 +2.4 +4.9 0.79 +3.8
January 1978 -3.4 0.83 -2.8 -6.4 0.82 -5.2
February +3.4 0.89 +3.0 +4.0 0.99 +3.9
March -4.9 0.77 -3.8 -5.2 0.79 -4.1
April -16.5 0.47 -7.8 -17.7 0.42 -7.4
May +2.7 0.37 +1.0 +7.0 0.34 +2.4
June +20.1 0.55d +11.0 +18.9 0.62e +11.8
July +22.3 1.00 +22.3 +21.0 1.00 +21.0
August +11.9 1.00 +11.9 +11.9 1.00 +11.9
September -9.1 1.00 -9.1 -9.1 1.00 -9.1
October -11.9 1.00 +11.9 -11.9 1.00 -11.9
November -10.1 1.00 -10.1 -10.4 1.00 -10.4
December -0.9 1.00 -0.9 -0.6 1.00 -0.6
January 1979 +9.8 1.00 +9.8 +9.5 1.00 +9.5
February 0.0 1.00 0.0 0.0 1.00 0.0
March +7.0 1.00 +7.0 +7.0 1.00 +7.0
April -4.9 1.00 -4.9 -4.9 1.00 -4.9
a Water table change represented the difference between water table
elevation at the beginning and end of the month.
b Specific yield derived from the regression equations for Plots C and H,
respectively, relating specific yield to depth. Values were derived for
the depth midway between the depth at the beginning and end of each month.
c Change in water storage represents the product of specific yield and water
table change.
67





Table 10 (continued)
dThe regression equation for specific yield in Plot H was applied only
to a height 6.13 cm above the surface of the peat. Above this height,
specific yield was assumed to be 1.00. The value shown is the average
specific yield for this month.
eThe regression equation for specific yield in Plot C was applied only
to a height of 2.10 cm above the surface of the peat. Above this height,
specific yield was assumed to be 1.00. The value shown is the average
specific yield for this month.
68





no major differences. Both plots undergo similar seasonal changes
in water storage. The largest increases in water storage occurred
during June and July, 1978. These were the two months with the
largest rainfall (see Table 5). No appreciable net storage of
treated wastewater or fresh water occurred in Plot H or Plot C. It
appeared that the applied treated wastewater or fresh water
displaced an equal volume of water out of the plot to which it was
applied within the one-week period following application. If the
water did not entirely flow out between applications, the water
storage in the plots would have shown an overall increase with time.
This was not observed. Applications of treated wastewater or fresh
water only built a temporary hydrostatic head in the plots. The
water table in each plot rapidly returned to equilibrium after each
weekly application. An illustration of the effects of pumping when
the water table was below the surface of the peat was presented in
the Methods section (Fig. 7).
Distribution of treated wastewater within the plot. The extent
of the distribution of the applied treated wastewater in Plot H (9.6
cm/wk treated wastewater) was determined through a chloride tracer
study (see Methods). The results of this experiment are presented
in Figs. 18 and 19. The chloride concentration of the treated waste-
water was 48 mg/l. Six of the seven medium depth wells located
within the plot (Fig. 18) exhibited chloride concentrations that were
higher than the treated wastewater concentration and much higher than
the concentrations in the wells located outside the plot. The chlo-
ride concentrations found in the deep wells (Fig. 19) were less than
the concentrations found in the corresponding medium depth wells.
Only the two deep wells in the center of the plot had concentrations
close to the treated wastewater concentration.
Results of monthly chloride analyses for the applied wastewater
and for sampling stations inside and outside of the experimental
plots are graphed in Figs. 20-24. As shown, the average concentra-
tion of chloride in groundwater from the "natural" marsh area was
significantly lower than the average concentration in the applied
69





II
9
62 59 53
61 60 53
62 58 52
58
59
53 62
40 5463
40 52
39 63
TREATED
WASTEWATER
DISCHARGE PIPE
SCALE
--IOm
10m
EFFLUENT [CI] =48
37
36
35
Figure 18. Results of the chloride tracer study in Plot H (9.6
cm/wk treated wastewater) from the medium depth (1.5 m)
wells. Values represent mg/l C1-. The top number repre-
sents the sample collected prior to treated wastewater
pumping, the middle number represents the sample col-
lected during treated wastewater pumping, and the bottom
number represents the sample collected twenty-four hours
after pumping had ceased.
70





14
12
II
14 26 1)
14 29 10
12 31 9
43
47
49
31
21 39 31
21 49 42
20 48 43
TREATED
-WASTEWATER
DISCHARGE PIPE
SCALE
lIOm
EFFLUENT [C']= 48
23
27
28
Figure 19. Results of the chloride tracer study in Plot H
(9.6 cm/wk treated wastewater) from the deep (2.5 m)
wells. Values listed as described for Fig. 18.
71





100 1977 1978 1979
80-
60-
40
0
C- J
J J A S O N D J F M A M J J A S 0 N D J F M A
Figure 20. Chloride concentration in the secondarily treated wastewater.





100 .
1977 M 1978 .1979
80- W2M
. 0. W M
60 --
U
40
20 : L- _A .
J J A S 0 N O J F M A M i J A S 0 N D J F M A M J
Figure 21. Chloride concentration in wells in the natural marsh. See Fig. 5 for sampling locations.





oo100 i
1977 1978 1979
80 0 W12D
Eo A W12M
0 W23M
60 --
9 80 j. -3M. -: --l. _.
E 0 W3D
j0 40
20 -
' I I I I I I I I I I I i 1 1 ~ .
J J A S 0 .N D J F M A M J J A S 0 N D J F M A M J
.1.00 i i l i l l I l i i '
Figure 22. Chloride concentration in wells in Plot H (9.6 cm/wk of treated wastewater). See Fig. 5
for sampling locations.
'" 80 A W3M
20 7
J J A S 0 N D J F M A M J J A' S 0 N D J F M A M J
Figure 22. Chloride concentration in wells in Plot H (9.6 cm/wk of treated wastewater). See Fig. 5
for sampling locations.





100
1977 1978 1979
Z 80 W15D W24M
E6 OW24M W415M
60
40 -
20
J J A S O N D J F M A M J J A S O N D J F M A M J
100 I I I I I I
1977 1978 1979
^.o w Co I W W
E 80 O WIOD W21M
E O W~21M .* IIOD
JU 60- W22M _----
2 I- ,= ,^
840 \-
20 C -
J J A S O N D J F M A M J J A S O N D J F M A M J
Figure 23. Chloride concentration in wells in Plot M, upper chart (3.7 cm/wk), Plot C, lower chart
(WIOD and W21, 4.4 cm/wk of fresh water) and Plot L (W22, 1.5 cm/wk).(see Fig. 5.for
sampling locations).





I00
o100 --- --I --- [ --i-- [ ( I --- -- I -- I --- I I i ,- I -
1977 1978 1979
_. 80 0 WIlD
cm a W16D
E 60 O W17D
wI
_ 20. I
J J A S O N D J F M A M J J A S 0 N D J F M A M J
100 i i t--I- -|------
1977 1978 1979
80 4 1
s^ .' I HIW|
E 60
40 -
0\- / I J .
J J A S 0 N D J F M A M J J A S 0 N D J F M A M J
Figure 24. Chloride concentration in deep wells in the natural marsh (upper chart) and the Palatlakaha
River (lower chart) (see Figs. 2 and 5 for sampling locations).





treated wastewater. Duncan's multiple range test was applied to the
data for wells in the northwest corner of Plots C, L, M, and H (W21M,
W22M, W24M,and W23M, respectively), and in the natural marsh (W2M).
Results are given in Table 11. The concentration of chloride was
significantly higher ( a = .05) in well W23M than in the natural
marsh. This suggests that chloride, and hence the treated waste-
water, was distributed rather uniformly over Plot H prior to export.
Utilizing the monthly chloride concentrations and estimated
water outflows for the period January December 1978, inflow and
outflow of chloride for Plots C and H were obtained. Results are
shown in Table 12. It must be noted that chloride content was not a
direct indicator of the rate of water flow past any particular
sampling station. Although the values of Table 11 must be viewed
with caution, they nonetheless provide further assurance that
applied fresh water and wastewater were distributed and exported more
or less evenly out through the peat layer in Plots C and H.
Duncan's multiple range test was performed on chloride concen-
tration data for surface station N (average of N1 and N2 data),
located in the natural area of the marsh near well W2M, and stations
HI, HO, CI, and CO, located in the inside and outside regions of
Plots H and C, respectively. Results of the analysis are given in
Table 13. Since natural levels of chloride in the surface water of
the marsh were fairly high, it was difficult to detect a significant
increase in chloride due to the influence of treated wastewater at a
particular surface site. However, a significantly higher (a = .05)
level of chloride was found within this group of stations at the
center of Plot H as compared with the natural area or Plot C.
The conclusions of the chloride tracer study and mass-balance
calculations are as follows:
1. Treated wastewater was distributed throughout the
bottom of the peat layer in Plot H.
2. Some leakage of applied treated wastewater occurred
vertically through the peat, directly beneath the
application pipe in Plot H. However, this leakage
was not great enough to influence the medium or deep
77





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