Title: Report on Reverse Osmosis Prepared by Subcommittee on Oversight, Committee on Natural Resources, Fla. House of Representatives
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/WL00004208/00001
 Material Information
Title: Report on Reverse Osmosis Prepared by Subcommittee on Oversight, Committee on Natural Resources, Fla. House of Representatives
Physical Description: Book
Language: English
 Subjects
Spatial Coverage: North America -- United States of America -- Florida
 Notes
Abstract: Jake Varn Collection - Report on Reverse Osmosis Prepared by Subcommittee on Oversight, Committee on Natural Resources, Fla. House of Representatives (JDV Box 43)
General Note: Box 18, Folder 3 ( Treatments of Water - 1983 ), Item 31
Funding: Digitized by the Legal Technology Institute in the Levin College of Law at the University of Florida.
 Record Information
Bibliographic ID: WL00004208
Volume ID: VID00001
Source Institution: Levin College of Law, University of Florida
Holding Location: Levin College of Law, University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Full Text



















REPORT ON

REVERSE OSMOSIS











PREPARED BY: SUBCOMMITTEE ON OVERSIGHT

COMMITTEE ON NATURAL RESOURCES

FLORIDA HOUSE OF REPRESENTATIVES


OCTOBER 28, 1982









EXECUTIVE SUMMARY

Although Florida receives about 56 inches of rainfall on

a yearly average, only about two inches of that 56 inches are

available for surface and groundwater storage, since the remainder

is lost through evapotransporation or runoff. Florida's growth

rate further compounds adequate supplies of potable water, as

most of Florida's growth has been in coastal counties where a

lowering of the groundwater levels has led to an increased potential

of saltwater intrusion and a poorer water quality.

This report examines the desalination process of reverse osmosis

as an alternative to conventional methods of producing potable water

needs. Desalination of saline water is basically a process of

separation. The main types of desalting are by electrodialysis,

ion exchange, and reverse osmosis. Reverse osmosis is a mechanical

technique which in effect separates the impurities out of the water

by forcing the water through a semipermeable membrane at high pressure.

There are currently 70 desalination plants operating in Florida

utilizing reverse osmosis technology. Reverse osmosis was found

to be superior to other methods of desalination and to be generally

competitive on a cost basis with more conventional systems of water

supply. The cost effectiveness of reverse osmosis increases with

the size of the plant and the process is superior to conventional

treatment systems in removing pollutants.

It is recommended reverse osmosis be considered when selecting

a method of water supply in light of its comparable costs, superior

quality of water produced, and reduced impact to groundwater aquifers

as compared with more conventional methods of water supply.










INTRODUCTION

Florida receives between 50 to 60 inches of rainfall on a

yearly average. This is more rainfall than any other state in

the continental United States except Louisiana. Why then does

an adequate supply of potable water appear to be a recurring

problem in certain locations of Florida?

First, this average rainfall data can be somewhat mis-

leading. According to the United States Geological Survey,

while the average rainfall in Florida as a whole is 56 inches

per year, this ranges from 40 inches per year in the Florida Keys

to 64 inches per year in Okaloosa County. Of this 56 inches, an

estimated 40 inches is lost to evapotranspiration and another 13

inches to runoff. Hence only about 2 inches of the original 56

inches is available for surface and groundwater storage.

Secondly, most of Florida's growth to date has been in those

coastal counties least able to provide potable water of sufficient

quantity and quality, especially Brevard, Broward, Dade, Hillsborough,

Lee and Pinellas Counties. Water quantity and quality are inter-

related in providing sufficient amounts of potable water. As

more and more water is extracted from groundwater in coastal

communities, the lowering of the groundwater levels leads to an

increased potential for salt water intrusion and eventually poorer

water quality. A number of coastal areas are currently utilizing

potable water not within the federal "Safe Water Drinking Act"

standards with respect to the amount of dissolved chlorides (i.e.

salts) in the water.







-2-


Given this disparate pattern of rainfall and growth across the

state, the choice for many coastal communities has been one of

attempting to treat relatively "abundant" sources of mineralized

groundwater in the area or relocating water of better quality from

further inland. Historically, the usual practice has been the

latter alternative based on what has been, up to now, the higher

costs of treating the poor quality water from localized sources.

However, this cost advantage may be narrowing, or, in some cases,

even nonexistent when compared with recent treatment technologies such

as reverse osmosis.

This oversight project examines the potential of reverse

osmosis as an alternative to more conventional methods of providing

potable water needs.






-3-


FINDINGS

Desalination techniques are basically a process of separation.

The main types of desalting are by distillation, freezing, and the

use of membranes. Membrane desalting can be electrical (electro-

dialysis), chemical (ion exchange), or mechanical (reverse osmosis).

Electrodialysis and ion exchange are presently unable to commercially

produce potable water, except from low salt concentrations of

brackish water. Reverse osmosis, however, can adequately produce

potable water of a superior quality on a cost comparable to conventional

water systems.

There are currently 72 operational desalination plants in Florida.

As Appendix A illustrates, most of them are located in coastal areas

of the state. Except for two plants, the 2.6 million gallons per

day flash distillation plant in Key West and the 2.1 million gallons

per day electrodialysis plant on Sanibel Island, all the other

desalination operations in the state are reverse osmosis. (Appendix B)

The flash distillation plant in the Keys, which was begun in 1967,

unfortunately has marred the reputation of desalination. Originally

designed to utilize sea water of high saline content, the change to

using brackish water of lower salt content caused unforeseen shut-

downs and malfunctions. Reverse osmosis, on the other hand, appears

to be a mechanical technology which can remove impurities and salt

concentration from brackish or sea water in a dependable fashion.

Osmosis is a natural phenomenon used by plants to move water

to the leaves by transferring it from cell to cell through the

semipermeable cell membranes. Figure 1 illustrates the principles

of osmosis when applied mechanically through reverse osmosis.
















Figure 1


OSMOTIC FLOW


MEMBRANE


FEED
WATER


HIGH PRESSURE
PUMP


OSMOTIC EQUILIBRIUM





OSMOTIC
HEAD
(PRESSURE)







/






E ,SEMIPERMEABLE
MEMBRANE


REVERSE OSMOSIS













/








\SEMIPE RMEABLE
MEMBRANE











SEMI
-PERMEABLE
MEMBRANE





PRODUCT
WATER


REGULATING
VALVE


WASTE WATER





-5-


The pressurized flow through the membrane acts to separate the

"impurities" in the mineralized water from the final product of

potable water. Since 1960 significant advances have been made

in water membrane technology. In particular, fluxes (flow per

unit area of membranes) have been improved two to three fold.

Direct comparisons of water supply costs are difficult since

the final delivered costs depend upon many factors including the

plant capacity, the physical area served, and pre and post-treatment

requirements. As Appendix C illustrates, reverse osmosis is vastly

superior to other treatment methods in removing pollutants. Hence,

the cost of pre and post-treatment requirements in particular must be

considered prior to any direct comparison between reverse osmosis

and conventional water treatment methodologies.

Table 1 gives some sample cost comparisons for various types

of treatment methodologies for plants located in the Southwest

Florida Water Management District.


TABLE 1

Delivered Price Per
Utility Type of Treatment 1000 Gallons (1977)

Lehigh Acres Conventional $1.51

Cape Coral Reverse Osmosis $1.61

Lee County Conventional $1.86

Bonita Springs Conventional $1.86

Sanibel Island Electrodialysis $2.40





-6-


The prices represent the final delivered price (i.e. what the

customers pay) and represents all costs associated for treatment

and delivery, including chemical treatment, debt retirement, energy,

legal and engineering costs as well as operation and maintenance

costs. Necessary periodic replacement of the reverse osmosis

membranes is also included as part of operation and maintenance

costs.

Table 2 is a sampling of production costs for reverse osmosis

plants throughout the country. In general, it can be seen that the

cost of production decreases as the capacity of the plant increases.


Location

Rotunda West, FL

Greenfield, Iowa

Ocean Reef, FL

Ft. Lupton, Colo.

Ft. Stockton, Colo.

Arkansas City, KS.

Artesia, New Mexico


TABLE 2

Capacity
Million Gallons Per Day

.05

.15

.93

1.90

2.80

5.75

6.60


Water Cost Per
1,000 Gallons

$1.25

.77

.90

.60

.66

.52

.48





-7-


This relationship between plant capacity and operating cost

becomes clearer in Table 3 which gives 1982 costs data for Phase I

of the Burnt Storm South Water Retention Plant in Punta Gorda.

(See also Appendix D).



Table 3 RO Cost Data

Burnt Storm South Water Retention Plant, Phase I
Million Gallons
Per Day Capacity Construction Costs Operation & Maintenance Costs

1 mgd $1 million $1.25 per 1,000 gallons

2 mgd $1.7 million $1.13 per 1,000 gallons

5 mgd $3.7 million $1.03 per 1,000 gallons

8 mgd $5.6 million $ .99 per 1,000 gallons

10 mgd $6.7 million $ .97 per 1,000 gallons

15 mgd $9.4 million $ .89 per 1,000 gallons













Source: Ed Clarke, Engineering
Miami, Florida
January 1982






-8-


A review of Appendix B shows that most operational reverse

osmosis plants in Florida are of limited capacity. The largest

existing reverse osmosis facility in Florida began operating

this year in Sarasota. The plant produces 4.5 million gallons

per day at a production cost of $0.71 per 1,000 gallons in 1982

dollars.

On July 1, 1982, the Select Committee on Water Management

attended a presentation and demonstration at this facility. The

committee was told that Sarasota had explored various alternatives

to meet their growing water demand, including surface water,

groundwater sources and the relocation of water from adjacent

Manatee County. Reverse osmosis technology was deemed to be most

cost effective as well as producing the best water quality. At a

cost of $1,750,000 for capital construction, the plant operates 225

membrane units. Each membrane unit lasts from three to five years,

and costs about $4,000 to replace. The 4.5 million gallons per day

produced by reverse osmosis is later blended and softened

with other well water to produce a maximum of 12 million gallons

per day. Waste brine from the reverse osmosis unit is discharged

into Sarasota Bay as approved by Department of Environmental Regulation

permit, where it is monitored regularly for increased total dissolved

solids, chlorides, and turbidity by the Department. (Appendix E).

99 percent of reverse osmosis water in Florida is utilized for

domestic potable water with the remainder going to industrial needs.

Reverse osmosis does have its limitations, but its ability to remove

numerous pollutants makes it superior to coagulation, chlorination





-9-


or active carbon in this consideration. More importantly, reverse

osmosis has the following additional advantages when compared with

conventional water treatment methods:

(1) Ability to meet more stringent drinking water quality

standards without incurring additional treatment to water;

(2) Ability to expand plant capacities by additional wells

into the groundwater and desalting these groundwaters, as opposed

to expanding infrastructure development of the conventional water

plant.

(3) Minimal susceptability to changing climatic conditions

and salt water intrusion.

One problem presented by reverse osmosis is the disposal of the

waste brine, especially in inland areas. However, adequate mitigation

techniques appear to be available through deep well injection in inland

areas and its return to sea water in coastal areas.





-10-


CONCLUSIONS AND RECOMMENDATIONS

The continued growth in Florida's coastal areas along with

unpredictable amounts of adequate rainfall and danger of salt water

intrusion in these areas has led to the increased use of desalination

as a basic water treatment process as well as a supplemental water

source. Of the types of desalination, reverse osmosis is clearly

the choice as the most cost-effective and dependable method. In

addition, the superior ability of reverse osmosis to remove pollutants

and the enhanced taste, smell, and drinkability of water treatment by

reverse osmosis should lend further to its increasing acceptance.

Reverse osmosis plants will probably continue to be concentrated along

coastal areas. There are, however, no major physical or economic

constraints to prevent their location inland.

It should be noted that this report has been limited to the cost

effectiveness of reverse osmosis as a source of water supply and

treatment; other issues affecting the selection of water supply

techniques such as conservation and protection of groundwater aquifers

have been ignored.

The following are suggested as areas for further study:

(1) The use of blending or combining reverse osmosis treated

water with conventionally treated potable water to produce larger

volumes of required potable water.

(2) Exploration of methods to provide incentives to those

utilizing reverse osmosis technology even where not the most cost

effective at the time. Individual incremental expansions in the

water supply capacity may not render reverse osmosis cost





-11-


effective while each additional expansion over the years would

continue to bring the unit cost down. In addition, continued

reliance on conventional water supply techniques from surface and

groundwater sources pose certain long term dangers to the water

supply which might be mitigated by the use of reverse osmosis.

(3) Counties which are considering relocating water from

other counties to meet potable water demand should compare the

cost-effectiveness of reverse osmosis treatment as one alternative.

According to the West Coast Regional Water Supply Authority,

construction costs for pipelines to transport water were

approximately $1 million per mile in 1978 dollars. This does not

include pre-treatment or production costs.









BIBLIOGRAPHY


U. S. Agency for International Development, The U. S. A.
Interior Department Desalination Manual, August, 1980

Pitts, C. E. Jr., "Desalination in Florida", (unpublished
report) 1979.

Kanel, Nagendra and Winn, Starley, "Membrane Plants in South
Florida", South Florida Water Management District, 1979.

Dykes, Glenn M., Jr. "Meeting Quality Standards in Florida"
(unpublished report by Florida Department of Environmental
Regulation) September 1979.

Oak Ridge National Laboratory, "Desalting Seawater and Brackish
Water: Cost Update." 1979.

World Water, "Desalination: Cutting energy and costs,"
August, 1981.

U. S. Department of Interior, Water Resources Scientific Information
Center, Office of Water Research and Technology, (Phone interviews
with Department's employees), June 2-3, 1982.





APPENDIX A


STATE OF FLORIDA


* Location of Desalinization Plants


0 dl
"qc'~


Source: -Florida Department of
Environmental Regulation





APPENDIX B


REVERSE OSMOSIS, DEMINERALIZATION and DESALINIZATION
PLANTS in FLORIDA


PLANT NAMES


ENGINEER


TYPE and
PIANT MANF.


Brevard
Brevard
Charlotte
Charlotte
Charlotte
Charlotte
Charlotte
Collier
Flagler
Flagler
Flagler
Indian River
Indian River
Lake
Lee
Lee
Lee
Lee
Lee
Lee
Lee
Manatee
Martin
Martin
Martin
Monroe

Monroe
Monroe
Orange
Palm Beach
Palm Beach
Palm Beach

Palm Beach
Sarasota
Sarasota
Sarasota
Sarasota
Sarasota
Sarasota
Sarasota
Sarasota
Sarasota
Sarasota
Sarasota


Cove of South Beaches
Chucks Steaks House
Alligator Utilities
Burnt Store Utilities
Eagle Point Nest MHP
Gasparilla Pines
Rotonda West
Pelican Bay
1414 Mobile Home Park
Marineland
Ocean Side Acres Apt.
Seminole Shores
Village Green
Wekiva Falls Park
Cape Coral
Greater Pine Island
Gulf Coast Resort
Imperial Harbor MH Estate
lona Trailer Ranch
Sanibel Island Water Asso.
Useppa Island
Christian Retreat Camp
Indian River Plantation
River Club
Sailfish Point
Keys Aqueduct
Desalination Plant
Aqueduct-Rock Harbor
Ocean Reef Club
KOA Christmas
Shelton Land & Cattle Co.
Okeelanta Sugar
Pheasant Walk (Palm
Beach County System #6)
Riverside Memorial Chapel
Bay Front MHP
Bay Lakes Estates MHP
Camalot Lakes MHP
City of Venice
Fairwinds Condo. Village
Kings Gate TT Park
Lake Village MHP
Lyons Cove Condominium
Myakka River State Park
Nokomis School
Palm & Pines MHP


G.E. Cantelou
A. Price
D. Ambrose
J. Elliott
C. Kimball
A. Conyers
F.L. Bell
P. Buckley
H.R. McMichael
T. Furman
A. Hartenstein
E. Schucker
Beindorf & Asso.
J. Briskey
T. Smallwood
P. Buckley
D. Davis
T. Garrett
I. Stuart
B. Bishop
F. Banks
J. Kennedy
R. Pitchford
Hutcheon
Gee/Jenson
Fluor -
Westinghouse
W. Wardwell
J. Buckley
Kauffman
Hutcheon
A. Tellechea
A. Strock
G. Wren
J. DeBay
D.S. Chambers
W.M. Lindh
R. Woodruff
W. Lindh
Tiona
J. Kennedy
W. Bishop
Tiona
V.E. Lynch
D.S. Chambers
D.S. Chambers


RO-Basic Tech .010
RO-Blend .005
RO-Polymetrics .030
RO-Basic Tech .160
RO- .036
RO-Permutit .010
RO-Permutit .500
RO-Permutit/Low Press. .500*
RO-Dupont .045
RO-Permutit .100
RO-Applied Water .037
RO-Basic Tech .020*
RO-Polymetrics .100
RO-Blend .015
RO-Permutit 3.000
RO-Envirogenics .825
RO-Basic Tech .028
RO-Basic Tech .096
RO-Basic Tech .020
ED-lonics 2.100
RO-Polumetrics .027
RO-Polymetrics .020
RO-Permutit .050
RO-Basic Tech .060
RO-Basic Tech .150*
Flash
Distillation 2.500
RO-Fluid Systems 1.000
RO-Gulf Roga 1.040
RO-Permutit .014
RO-Permutit .004
RO-Dupont .042
RO-Low Pressure
Basic Tech/Permutit 1.080
RO-Basic Tech/Low Press. .001
RO-Continental .002
RO-Dupont/Permasep .043
RO-Basic Tech/Low Press. .100*
RO-Polymetrics 1.000
RO-Polymetrics .043
RO-Purification Tech .060
RO-Polymetrics .060
RO-Gulf Environmental .006
RO-Purification .050
RO-Basic Tech .001
RO-Polymetrics .009


COUNTY


OUTPUT
MGD


PLANT~~ ~ ~ ~ NMSPATMN G




APPENDIX B CONTINUED


Sarasota
Sarasota
Sarasota
Sarasota
Sarasota
Sarasota
Sarasota
Sarasota
Sarasota
Sarasota

Sarasota
St. Johns
St. Lucie

St. Lucie
St. Lucie
St. Lucie
St. Lucie
Volusia
Volusia
Volusia
Volusia
Volusia
Volusia
Volusia


Peterson Manufacturing
Pelican Cove S/D
Sarasota, City of
Sarasota Bay MHP
Siesta Key
Siesta Key
Spanish Lakes MHP
Sorrento Shores
Sorrento Shores S/D
Southbay Yacht & Racquet
Club
Workman Electronic Corp.
Mariner's Watch
Bryn Maur Camp Resort
(formerly Ramada Camp Inn)
Fort Pierce Jai Alai
Harbor Br. Foundation
Ocean Towers
Queen's Cove
City of Ponce Inlet
Indian Harbor Estates
Kingston Shores
River Park MH Colony
Riverwood Park
South Water Front Park
Sugar Mill County Club
Estates


D.S. Chambers
Tri-County
Smith/Gillespie
D.S. Chambers
B. Bishop
RS&H.
W. Lindh
B. Bishop
B. Bishop
M. Wellford

D.S. Chambers
M. Ferguson
C. Donahue

H. Ross
P. Matecchini
L. Brock
R. Hellstrom
A. Gilbert
V. Pearson
W. College
J. Cooper
L. Bennett
P.N. Holly Asso.
C.R. Burdick


* Not yet in service.




Source: Florida Department of Environmental Regulation


iii


RO-Continental
RO-Polymetrics
RO-Polymetrics
RO-Polymetrics
ED-Ionics
RO-Polymetrics
RO-Gulf Environmental
RO-Permutit
ED-Ionics
RO-Permutit

RO-Polymetrics
RO-Permutit
RO-Gulf Environmental

RO-Permutit
RO-Permutit
RO-Basic Tech
RO-Basic Tech
RO-Permutit
RO-Ajax
RO-Permutit
RO-
RO-Blend
RO-
RO-Blend


.0003
.120
4.500
.005
2.000
.625
.060
.400
.100
.125

.0005
.016
.150

.039
.019
.120*
.010
.394
.080
.150
.245
.003
.015
.030





APPENDIX C


THE REMOVAL OF POLLUTANTS FROM SURFACE WATER BY MEANS OF DIFFERENT TREATMENTS

Reverse Active
Chlorination Coagulation Osmosis Carbon
Bacte ia and viruses XXX XXX XXX
Suspended matter XXX XXX XX
Total organic carbon -XX XXX XXX
Pesticides XX XXX XX
Inorganic salts -- XXX
Inorganic toxic compounds XX-XXX XXX
Ammonia (XXX) X
Phenols -X XXX
Taste and odor X XX-XXX XXX
Oil X XXX XX
Detergents X XXX XXX
Hydrocarbons X-XX XXX
Chlorinated hydrocarbons -X-XX XXX
Volatile organic acids X XX
Carbohydrates
Amino acids X XXX XX
Fatty acids
Proteins


XXX 90-100% removal
XX 50-90% removal
X 10-50% removal
< 10% removal

















Source: South Florida Water Management District













REVERSE OSMOSIS COST DATA

Plant

Cost Parameter (a,b) 1.0

Capital Cost ($1000) 1,154

Electric (1000 KwHr./Yr) 2,530

Maintenance Materials ($1000/Yr.) 95

Labor (Hr/Yr) 1,949

Chemicals (Ton/Yr) 56

Total O&M ($1000/Yr) 228

Total Annual Cost ($1000/Yr)(d) 337
(/1000 gal)(d) 92


Size (MGD) (

10

8,216

24,102

734

2,647

564

1,856

2,632
72


50

35,653

116,486

3,436

4,950

2,821

8,803

12,168
67


Notes: (a) Taken From Culp/Wesner/Culp.
Water Reuse and Recycling.
OWRT/RU-79. A report to the
Office of Water Research and
Technology, U.S. Department of
the Interior. 1979.

(b) Costs are in September 1977 dollars.
Power at 4.0/KwHr. Labor at $10/Hr.
(c) For an AWT effluent.

(d) Includes capital costs ammortized at 7.0% for 20 years.


APPENDIX D






APPENDIX E


+. 7 -,4


BRIEF DESCRIPTION OF THE
CITY OF SARASOTA 12 MGD COMBINED
REVERSE OSMOSIS/ION EXCHANGE
WATER TREATMENT PLANT SCHEDULED
TO BE PLACED IN OPERATION
IN JULY 1982


(7uaIt


Ci


*







CITY OF SARASOTA
12 MGD REVERSE OSMOSIS ION EXCHANGE
WATER TREATMENT PLANT


1---*--'.'..gi








_Tr-
-- -- 4#





-'n4_



K-_ )J^ )


i --


Sarasota's water treatment facility is capable of producing twelve million

gallons per day (MGD). Two treatment processes are utilized, each from a

separate source of supply. The products of each process are finally blended to produce

an economic, palatable and safe potable water.

DEMINERALIZATION-REVERSE OSMOSIS TREATMENT PROCESS

The supply for the Reverse Osmosis (R.O.) process is derived from six deep wells

within the City limits, specifically renovated for the purpose.

The water from these wells is relatively high in dissolved solids (1500-2000 parts

per million) which dictates that advanced demineralization be utilized.

Reverse osmosis requires considerable care in the handling of raw water from its

source to the pressure vessel, as the membranes within the vessel are delicate and

easily fouled by compounds which might be formed by chemical reaction. To preclude

the formation of such compounds, by hydrogen sulfide reacting with ferrous metal, the

R.O. supply wells are plastic lined. All R.O. raw water transmission mains are

plastic and concrete, while the pumping equipment utilizes bronze and stainless steel.

Upon entering the treatment plant, the R.O. raw water is acidified with

sulfuric acid. This serves to keep the hydrogen sulfide in solution, and improves

the efficiency of the R.O. process. Next, the feed water is filtered to remove

particulates and sodium hexametaphosphate is added. The sodium hexametaphosphate

stabilizes dissolved salts which otherwise would precipitate as a result of increased

pressure and concentration, thereby causing damage to the membranes.

The feed water is pumped into the membrane vessels at a pressure of more than 400

pounds per square inch. Pure water molecules are forced through a semi-permeable

membrane to become the product, while the dissolved salts are retained on the feed

side of the membrane and flushed from the vessel by incoming feed water. The

concentrate produced in the first stage of each rack becomes the feed to the second

stage. The concentrate remaining from the second stage flows to waste. The vessels

are arranged in three separate racks, each of which holds 75 vessels for the

two stage R.O. process. Each rack is capable of producing 1.5 MGD of finished

product; collectively, 4.5 MGD of product can be produced using all three racks at
the maximum feed of 6.0 MGD.

After leaving the pressure vessels, the product water flows to a degasifier where

hydrogen sulfide and carbon dioxide are removed. An alkaline compound is then added

to neutralize the previously induced acidity.


~-e_



~c









SOFTENING ION EXCHANGE TREATMENT PROCESS


--L-"T~-~"-~-~"-y
----I


C);


'3 1- (


-(i- i


4


The supply for the softening process is provided by the City's Verna Well
Field, located 20 miles east of Sarasota. Water from Verna has a more acceptable
level of dissolved solids, but requires treatment to lower its hardness from 500
parts per million to 8 ppm.
Ion exchange was selected for incorporation into the new plant to produce
5.2 MGD of softened water from a flow of 5.6 MGD of raw water supplied by the Verna
Wellfield.
Softening is accomplished by passing the raw water through vessels containing
Zeolite, a medium which exchanges the hardness ions, primarily calcium and magnesium,
with sodium ions. There are four softening units; three of which are operating
at full production, while the fourth is regenerating through the introduction of
chlorinated sea water which is the source of sodium ions.
0.7 MGD of sea water is used for regeneration, while 0.4 MGD of raw well
water is used for rinse. Both of these are wasted after use.


BLENDING


At Verna Wellfield, raw water is aerated and chlorinated prior to transmission
to the treatment plant. Without further treatment the quality of Verna water is
such that it allows blending of 2.3 MGD, as transmitted from the wellfield, with
9.7 MGD of demineralized/softened treatment plant product.
Blending takes place in a clearwell beneath the R.O. degasifiers, where each of
the final products flow after the respective treatment process. The blending
water is then chlorinated and transferred to storage facilities, from which high
service pumps deliver the water into the distribution system.
Thus, from 13.9 MGD of raw, mineralized well water, the needs of the City of
Sarasota are met with 12 million gallons per day of quality potable water.


viii
















- _- .

)-:0
>-~: ):; 1


(-


I

)QKe
___




University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs