vvEPA
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/2-84-134
August 1984
Research and Development
Design Manual:
Removal of
Fluoride from Drinking
Water Supplies by
Activated Alumina
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EPA-600/2-84-134
August 1984
DESIGN MANUAL
REMOVAL OF FLUORIDE FROM
DRINKING WATER SUPPLIES
BY
ACTIVATED ALUMINA
by
Frederick Rubel, Jr., P.E,
Rubel and Hager, Inc.
Tucson, Arizona 85711
Contract No. 68-03-2917
Project Officer
Steven W. Hathaway
Drinking Water Research Division
Muinicipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
ntoi Protection Agency
. Environmental r*,
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DISCLAIMER
"The information in this document has been funded wholly or in
part by the United States Environmental Protection Agency under Contract
No. 68-03-2917 to AWARE, Inc. It has been subject to the Agency's peer
and administrative review, and it has been approved for publication as an
EPA document. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use."
ii
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FOREWORD
The U.S.- Environmental Protection Agency was created because of
increasing public and government concern about the dangers of pollution
to the health and welfare of the American people. Noxious air, foul
water, and spoiled land are tragic testimonies to the deterioration of
our natural environment. The complexity of that environment and the
interplay of its components require a concentrated and integrated attack
on the problem.
Research and development is that necessary first step in problem
solution; it involves defining the problem, measuring its impact, and
searching for solutions. The Municipal Environmental Research Laboratory
develops new and improved technology and systems to prevent, treat, and
manage wastewater and solid and hazardous waste pollutant discharges from
municipal and community sources, to preserve and treat public drinking
water supplies, and to minimize the adverse economic, social, health,
and aesthetic effects of pollution. This publication is one of the
products of that research and provides a most vital communications link
between the researcher and the user community.
The pollution of our nation's groundwater has been called the
environmental problem of the 1980s. When polluted groundwater serves
as a source of public drinking water, pollutants must be removed to
levels below standards regulated by the Safe Drinking Water Act (Public
Law 93-523). Fluoride, in concentrations exceeding the optimum level
beneficial to teeth, can become detrimental to new tooth formation in
infants and children up to about 12 years old. This design manual shows
step by step the actual methods for designing a central water treatment
plant for removal of excess fluoride from small community water supplies.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
iii
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ABSTRACT
This manual is an in-depth presentation of the steps required to design
and operate a water treatment plant for removal of excess fluoride using the
activated alumina method. Low capital and operating costs, simple operation,
and ability to .closely control the effluent fluoride level are features that
highlight this process. The alumina process requires adjustment of raw water
pH to 5.5 prior to passing through the treatment media; after treatment, the pH
is readjusted to the desired level. Initially, the process removes more than
95 percent of the fluoride in the raw water. Blending may be practiced if
initial fluoride is low. As treatment continues, the activated alumina grains
adsorb fluoride ions until saturated. Implementation of a caustic soda regen-
eration releases and totally removes fluoride ions in a highly concentrated
wastewater which must be discarded. After regeneration, the pH of the treat-
ment media is lowered to where treatment resumes again and a new cycle
commences.
This manual includes discussion of design requirements and details of
operation and maintenance. It discusses the capital and operating costs
including the many variables which can raise or lower costs for identical
treatment systems. Wastewater disposal is also discussed.
iv
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CONTENTS
Chapter
FOREWORD ill
ABSTRACT iv
CONTENTS v
LIST OF FIGURES viii
LIST OF TABLES ix
ACKNOWLEDGEMENTS x
INTRODUCTION
1.1 Purpose and Scope 1-1
1.2 Background 1-1
1.3 Fluoride in Water Supplies 1-3
1.4 Health Effects 1-3
1.5 Reduction of Fluoride 1-4
1.6 References 1-5
TREATMENT METHODS FOR FLUORIDE REMOVAL
2.1 Introduction 2-1
2.2 Granular Activated Alumina 2-1
2.3 Alternate Treatment Methods 2-3
2.4 References 2-5
DESIGN OF CE.NTRAL TREATMENT SYSTEM
3.1 Introduction 3-1
3.2 Conceptual Design 3-3
3.3 Preliminary Design 3-6
3.3.1 Treatment Equipment Preliminary Design 3-6
3.3.2 Preliminary Equipment Arrangement 3-14
3.3.3 Preliminary Cost Estimate 3-15
3.3.4 Preliminary Design Revisions 3-17
3.4 Final Design 3-17
3.4.1 Treatment Equipment Final Design 3-20
3.4.2 Final Drawings 3-26
3.4.3 Final Capital Cost Estimate 3-26
3.4.4 Final Design Revisions 3-26
3.5 References 3-26
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CONTENTS (continued)
Chapter
4 CENTRAL TREATMENT SYSTEM CAPITAL COST
4.1 Introduction 4-1
4.2 Discussion of Cost Variables 4-2
4.2.1 Water Chemistry 4-3
4.2.2 Climate 4-4
4.2.3 Seismic Zone 4-4
4.2.4 Soil Conditions 4-4
4.2.5 Existing Facility 4-5
4.2.6 Backwash and Regeneration Disposal
Concept 4-6
4.2.7 Chemical Supply Logistics 4-7
4.2.8 Manual Versus Automatic Control 4-7
4.2.9 Financial Considerations 4-7
4.3 Relative Capital Cost of Fluoride Removal
Central Water Treatment Plants Based
Upon Flow Rate 4-8
4.4 References 4-8
5 TREATMENT PLANT OPERATION
5.1 Introduction 5-1
5.2 Initial Startup 5-4
5.3 Treatment Mode 5-4
5.4 Backwash Mode 5-8
5.5 Regeneration Mode 5-9
5.6 Neutralization Mode 5~10
5.7 Operator Requirements 5-11
5.8 Laboratory Requirements 5-11
5.9 Operating Records 5-12
5.9.1 Plant Log 5-12
5.9.2 Operation Log 5-12
5.9.3 Water Analysis Reports 5-12
5.9.4 Plant Operating Cost Records 5-12
5.9.5 Correspondence Files 5-14
5.9.6 Regulatory Agency Reports 5-14
5.9.7 Miscellaneous Forms 5-14
5.10 Treatment Plant Maintenance 5-14
5.11 Equipment Maintenance 5-14
5.12 Treatment Media Maintenance 5-14
5.13 Treatment Chemicals Supply 5-15
5.14 Housekeeping 5-15
vi
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CONTENTS (continued)
Chapter Page
6 CENTRAL TREATMENT PLANT OPERATING COST
6.1 Introduction 6-1
6.2 Discussion of Operating Costs 6-2
6.2.1 Treatment Chemical Costs 6-2
6.2.2 Operating Labor Costs 6-6
6.2.3 Utility Cost 6-7
6.2.4 Replacement Treatment Media Cost 6-8
6.2.5 Replacement Parts and Miscellaneous
Material Costs 6-10
6.3 Operating Cost Summary 6-10
APPENDIX A SUMMARY OF SUBSYSTEMS INCLUDING COMPONENTS A-l
APPENDIX B TREATMENT SYSTEM DESIGN EXAMPLE B-l
APPENDIX C DISCUSSION OF ACID CONSUMPTION REQUIREMENTS
FOR pH ADJUSTMENT OF RAW WATER C-l
APPENDIX D TABULATIONS OF CAPITAL COST BREAKDOWNS
FOR CENTRAL FLUORIDE REMOVAL WATER
TREATMENT PLANTS BASED UPON FLOW RATE D-l
APPENDIX E ENGLISH/METRIC CONVERSIONS E-l
Vll
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FIGURES
Number Page
3-1 Water Analysis Report Form 3-2
3-2 Basic Flow Diagram 3-5
3-3.1 Process and Instrumentation Diagram (P&ID) 3-7
3-3.2 Process and Instrumentation Diagram (P&ID) 3-8
3-4 Treatment Bed and Vessel Design Calculations 3-10
3-5 Preliminary Equipment Arrangement Plan 3-11
3-6 Preliminary Equipment Arrangement Elevations 3-16
3-7 Chemical Mixing Tee Detail 3-23
4-1 Cost of Fluoride Removal at an Ideal Location 4-9
4-2 Cost of Fluoride Removal for a Typical Location 4-10
5-1 Valve Number Diagram 5-2
5-2 Basic Operating Mode Flow Schematics 5-7
5-3 Fluoride Removal Water Treatment Plant Operation
Log 5-13
5-4 5,000 Gallon Chemical Storage Tank-Liquid Volume 5-16
6-1 Curve Illustration Rule of Thumb for Volume of
Water to be Treated Per Cycle vs. Raw Water
Fluoride Level 6-5
A-l Schematic Flow Diagram A-2
C-l Graph of pH as a Function of Total Alkalinity
and Free Carbon Dioxide C-2
viii
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TABLES
Number
1.1 Maximum Contaminant Levels for Fluoride 1-2
3.1 Preliminary Cost Estimate-Example for Fluoride
Removal Water Treatment Plant Preliminary
Capital Cost Estimate 3-17
3.2 Final Cost Estimate-Example for Fluoride Removal
Water Treatment Plant Final Capital Cost
Estimate 3-18
4.1 Final Cost Estimate Example for Ideal Location
Fluoride Removal Water Treatment Plant Final
Capital Cost Estimate 4-3
5.1 Fluoride Removal Water Treatment Plant valve
Operation Chart 5-3
5.2 Calculated Downflow Pressure Drop Data 5-5
6.1 Price for Alcoa F-l, 28-48 Mesh Activated Alumina 6-9
6.2 Operating Cost Tabulation 6-10
D.I Tabulation of Estimated Capital Cost* of Fluoride
Removal Central Water Treatment Plants Based
Upon Treatment Flow Rate in Dollars Rounded Off
to the Nearest Thousand D-l
D.2 Tabulation of Estimated Capital Cost* of Minimum
Fluoride Removal Central Water Treatment Plants
Based Upon Treatment Flow Rate in Dollars Rounded
Off to the Nearest Thousand D-2
IX
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ACKNOWLEDGEMENTS
This is to acknowledge the efforts of all those involved in the creation
and development of this manual. These include:
Manual Preparation
AWARE Inc., Nashville, Tennessee
Project Manager: Dr. Ann N. Clarke
Production Staff: Marlayne Clark, Dee Biggert, Sue Prosch, Jackie Thomas
(drafting)
Technical Direction
CERI Project Officer: James Smith, CERI, EPA, Cincinnati, Ohio
Technical Project Officer: Steve Hathaway, MERL, EPA, Cinncinati, Ohio
x
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CHAPTER 1
INTRODUCTION
1.1 PURPOSE AND SCOPE
This manual has been prepared to present up-to-date information on design
of central treatment plants for the removal of excess fluoride from potable
water supplies.
This manual is an independent document. The detailed design information
presented herein applies exclusively to granular activated alumina technology
for selective removal of excess fluoride. Several other treatment methods have
been employed for this application, but none with the cost-effectiveness and
process efficiency of the activated alumina method. Some of the more familiar
methods and their limitations are covered in Chapter 2.
When excess fluoride is present in potable water in combination with
excess quantities of other organic and/or inorganic contaminants, the acti-
vated alumina method may not be optimum for the application. Those water
supplies must be evaluated on a case-by-case basis for selection of the appro-
priate treatment method, or combination of methods, for the application. That
technology is beyond the scope of this manual.
There has been interest exhibited in "point-of-use" application of the
activated alumina technology; however, that area is not included in the scope
of this manual.
1.2 BACKGROUND
Under the National Interim Primary Drinking Regulations, maximum contami-
nant levels (MCL) in potable water supplies have been established for ten
inorganic chemicals, including fluoride. The MCL for fluoride varies from 1.4
to 2.4 mg/1 depending upon the annual average of maximum daily air temperatures
(see Table 1.1). Since it became known that excess fluoride in drinking water
caused mottled teeth in children , many methods of removing fluoride have been
developed. The activated alumina method is one of them.
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TABLE 1.1. MAXIMUM CONTAMINANT LEVELS FOR FLUORIDE
"c
12.0
12.1-14.6
14.7-17.6
17.7-21.4
21.5-26.2
26.3-32.5
Average Maximum Daily
"F
53.7
53.8-53.3
58.4-63.8
63.9-70.6
70.7-79.2
79.3-90.5
Fluoride
Level
mg/1
2.4
2.2
2.0
1.8
1.6
1.4
Although many investigators have found that activated alumina is quite
effective in reducing fluoride to very low levels in treated water, there is
confusion, as to the procedure for using the activated alumina process.
Churchill , in his 1936 patent on the use of activated alumina for fluoride
removal, states that a pH of 5 to 6.5 should be used for treatment for best
results. There is no stated capacity in his patent. E. A. Savinelli and A.
R. Black , in their 1958 bench experiments, '.showed that a capacity of 3,400
grains/cu ft was achieved when the treated waiter pH was 5.6. These studies
were made with tap water to which sodium fluoride had been added. Yeun C. Wu
showed that treatment pH is quite important for high removal capacities. He
reported maximum removals of 4,200 grains/cu ft^with treatment at pH 5 on pure
sodium fluoride solutions. Other investigators who have made bench, pilot
or commercial installation studies have reported much lower capacities because
they have not understood or chosen to operate at optimum pH conditions.
There are three plants at which there have been several years of low-cost
operating experience in producing waters with fluoride concentrations reduced
to acceptable levels. They are:
1. Lake Tamerisk, Desert Center, California (1,100 gpm) - 1970
2. Rincon Water Company, Vail, Arizona ( 500 gpm) - 1972
3. Town of Gila Bend, Arizona ( 900 gpm) - 1978
By paying close attention to pH control, the three plants are able to
operate routinely with removal capacities exceeding 2,000 grains/cu ft.
As the raw water fluoride concentration increases, the activated alumina
capacity increases. For a water with a fluoride concentration of 22 mg/1 (not
a normal level in U.S.A.), the alumina capacity reaches 4,500 grains/cu ft.
The granular activated alumina employed at the above treatment plants is
Alcoa Grade F-l with mesh size of 28-48. Larger mesh sizes have been tried;
they work, but their fluoride capacities are lower. Finer mesh material has
not been used in other than laboratory bench-scale work. A new pelletized
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material, F-100, has been developed by Alcoa and has been tested in the field.
This material will soon be available. It is the same mesh size (28-48) as the
F-l and has the same fluoride removal capacity. Its advantage is in having
very few fines. It is, therefore, easier to handle. There are other manufac-
turers that produce an activated alumina product similar to the Alcoa F-l.
However, to-date, there has been very little demonstration work to verify the
performances.
1.3 FLUORIDE IN WATER SUPPLIES
Fluorine, a gaseous halogen, is not found in the free state, but occurs in
combination with other elements as fluoride compounds. Most of these compounds
are a complex of calcium-fluoride-phosphate. Fluoride ions normally exist in
small concentrations in all water supplies. Unless contaminated by fluoride-
bearing wastes, the concentrations in surface water supplies are normally low.
Frequently surface waters with low fluoride concentrations receive fluorida-
tion treatment to raise the level to an optimum desired for consumer protection
from tooth decay. The optimum level established by the U.S. Public Health
Service is one-half of the MCL. Well water supplies have higher fluoride
concentrations due to the fact that exposure to fluoride-bearing minerals is
far greater. There are, however, many well water supplies with fluoride levels
low enough to require the above-mentioned fluoridation treatment. The vast
majority of well water contains fluoride levels close to optimum, or within the
MCL. Nevertheless, per Letkiewicz , there are more than 2,000 water supplies
in the United States in which the fluoride MCL is exceeded. Of those, nearly
all have fluoride levels occurring between the MCL and 12 mg/1. There are
known water supplies with natural fluoride levels as high as 30 mg/1. In those
water supplies, the concentration of other minerals is usually too high to be
used for potable water service without desalinization.
1.4 HEALTH EFFECTS
Due to the natural affinity of fluoride ions for calcium, there is a
complex interaction between ingested fluoride and skeletal components. Med-
ical studies have been conducted for many years to determine the health effects
on animals and humans resulting from that interaction. Results have not been
conclusive. These studies are very difficult to control because, except for
dental fluorosis (mottled teeth) in children, the skeletal effects develop
over long periods of time. During those periods there are many other elements
interacting with the skeletal system as well as with the fluoride ions. The
specimens observed during the studies may also have ingested fluoride from
sources other than water; or may have absorbed airborne fluoride ions through
the lungs or even the skin.
In the field of veterinary medicine there are many documented cases,
covering dairy cattle and other farm animals, that have experienced fluoride
toxicosis (bone deterioration due to excessive fluoride) from ingestion of
water with fluoride levels ranging from 6 to 12 mg/1. This affliction results
in crippling and death.
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Dental fluorosis is recognized as a direct result of ingestion of water
with fluoride content exceeding the MCL by children ranging in age up to twelve
years old. Dental fluorosis can vary from a mild discoloration of the tooth
enamel to a severe pitting and embrittlement of the tooth structure. The
severity of the condition varies directly with the concentration of the fluor-
ide and the amount of water ingested. Once the adult teeth are fully formed,
there is no further deterioration. This condition is considered as a health
problem by some health experts; but others state that it is a cosmetic problem
which is not to be considered as detrimental to health.
1.5 REDUCTION OF FLUORIDE
It is desirable to control the concentration of fluoride in potable water
supplies as close to the optimum level as possible. The optimum is one-half of
the MCL (see Table 1.1). In water supplies where the fluoride level exceeds
the MCL, steps must be taken to reduce that level to below the MCL (preferably
to the optimum level). This design manual addresses removal of excess fluoride
by the activated alumina method. There are other treatment methods which could
be considered (see Chapter 2). There are also other options which may offer
less costly solutions. These optional solutions all involve alternate sources
of supply.
The first choice is an existing water supply within the service area with
known quality that complies with the fluoride MCL in addition to all other
MCL's (both organic and inorganic). If another source complies with the
fluoride MCL but exceeds another MCL (or MCL's), it may still be feasible to
blend the two sources and achieve a water quality that complies with all MCL's.
There are other features of this option that may present liabilities during its
consideration. These would include, but not be limited to, high temperature or
undesirable quantities of non-toxic contaminants such as turbidity, color,
odor, hardness, iron, manganese, chloride, sulfate, sodium, etc.
Another option is to drill a new well (or wells) within the service area.
This approach is attempted only when there is sound reason to believe that
sufficient quantity of acceptable quality water can be located. The cost (both
capital and operating) of a new well must not exceed the cost of treating the
existing source. There is an element of risk in this approach.
Another approach is to pump good quality water to the service area from
another service area. As the distance increases, the rise in elevation
increases and/or the existence of physical barriers occurs, the costs of
installing the delivery system and delivering the water become increasingly
unfavorable. Similar to the alternate source within the service area, this
imported source can also be blended as described above.
Use of bottled or other modes of imported acceptable quality water to be
used only for potable water purposes is also an option. The reliability, the
cost and the assurance that the consumers will only use that source are deter-
rents to be considered.
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Other options such as "point-of-use" treatment systems are viable alter-
natives. However, the treatment reliability of such units cannot be assured
unless there are stringent controls governing their operation and maintenance.
Also the problem of assuming that all users consume only water that has been
treated where untreated water is also available must be addressed.
1.6 REFERENCES
1. Dean, L.T., Arnold, F.A., Jr., & Elvove, E., Domestic Water and Dental
Caries., Pub. Health Rep. 57:1155 (1942).
2. Churchill, H.V., U.S. Patent 2,059,553 (Nov. 3, 1936).
3. Savinelli, E.A. and A.P. Black, Defluoridation of Water with Activated
Alumina., Journal AWWA, 50:33 (1958).
4. Wu, Yeun C., Activated Alumina Removes Fluoride Ions from Water, Water and
Sewage Works, 125:6:76 (June 1978).
5. Boruff, C.S., Removal of Fluorides from Drinking Waters, IEC, 26:69
(1934).
6. Goetz, P.C., U.S. Patent 2,179,227 (December 6, 1938).
7. Maier, F.J., Defluoridation of Municipal Water Supplies, Journal AWWA,
45:879 (1953).
8. Swope, H.G. and R.H. Hess, Removal of Fluorides from Natural Waters by
Defluorite. IEC, 29:424 (1937).
9. Zabban and R. Helrick, Defluoridation of Waste Water, Proc. 30th Ann.
Purdue Industrial Conference (1975).
10. Zabban and N.W. Jewett, The Treatment of Fluoride Wastes, Proc. 22nd Ann.
Purdue Industrial Waste Conference, Engineers Bulletin No. 129 (1967).
11. Rub'el, F., Report on Feasibility Evaluation of the Removal of Excess
Fluoride from Mine Water, (Confidential), C-b Shale Oil Venture, Rio
Blanco, Colorado (June 1, 1978).
12. Shupe, J.L. and A.E. Olson, Clinicopathic Features of Fluoride Toxicosis
in Animals, Proceedings of the International Fluoride Symposium, Utah
State University, (May 24-27, 1982).
13. Letkiewicz, F., Occurrence of Fluoride in Drinking Water, Air and Food,
EPA Draft Report, ODW (October 1983).
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CHAPTER 2
TREATMENT METHODS FOR FLUORIDE REMOVAL
2.1 INTRODUCTION
There are several central treatment plant methods that can remove excess
fluoride from potable water supplies. This manual only addresses the activated
alumina method which to date has been the most successful. Alternative physi-
cal/chemical processes which include adsorption, ion exchange, membrane separ-
ation and chemical precipitation are described briefly in this chapter. The
status of the alternate methods has already been summarized by several authors.
An AWWA Journal article by Sorg covers the subject quite well.
2.2 GRANULAR ACTIVATED ALUMINA
The granular activated alumina method which is an adsorption process is
the most efficient and least costly treatment method available to date. Excep-
tions can occur at existing treatment installations where minor modifications
to the treatment process can remove the necessary quantity of fluoride. This
design manual is directed toward implementation of the granular activated
alumina method for the selective removal of excess fluoride from potable water
supplies.
The treatment media specification is provided in Chapter 1. The material
is a by-product of aluminum production. It is primarily an aluminum oxide
which has been activated by exposure to high temperature and caustic soda. The
material is extremely porous. Therefore, the surface area per unit of weight
is quite high. The material is ground into a granular form, and screened into
various mesh sizes ranging from one half inch gravel down to fine dust which
passes a 325 mesh screen. Each of the various sizes is adapted to specific
applications , which include drying of air/gas and catalysts.
There have been many papers written on the application of granular activ-
ated alumina to the removal of fluoride from water. Some of these are included
in the References for Chapter 1. One of the earliest and most publicized
activated alumina fluoride removal plants which was built in Bartlett, Texas in
1952 operated for many years; the raw water fluoride level was 8 mg/1.
Initially the raw water pH which was above 8.0 was not adjusted. Eventually,
it was adjusted to 7.0. The alumina capacity for fluoride ions was reported at
700 grains/cu ft. At a later date, a new well was developed which had a
fluoride level of 3 mg/1. With raw water pH adjusted to 7.0, the reported
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fluoride capacity of the alumina was reduced to 450- grains/cu ft. This plant
is no longer operational. The current basic process technology was formally
published in an EPA Technical Report in 1978. Other researchers have since
duplicated this work and published reports covering laboratory, pilot-scale
and full-scale plant projects.
By carefully adjusting raw water pH to 5.5, maximum fluoride removal is
reliably achieved. Fluoride ions are attracted and held to the vast surface
area thorughout the pores of the activated alumina grains. The attractive
forces are strongest in the pH range of 5.0-6.0. As p'H deviates from that
range, fluoride adsorption forces decrease at an increasing rate. In this
optimum pH range other ions that compete with fluoride for the same adsorption
sites are not adsorbed. Included are silica which is adsorbed in the pH range
6 through 10 and some hardness ions which are removed in the pH range 7 through
10. Hardness removal occurs at the start of a treatment run. However,
activated alumina adsorption is preferential to fluoride; therefore, as the
run progresses, hardness removal ceases. Alkalinity is not adsorbed at the
optimum fluoride removal pH; in the pH range 7 through 10 a negligible amount
of alkalinity is removed. At the optimum fluoride removal pH, some organic
molecules and some trace heavy metal ions are adsorbed; however, except for
arsenic, these are completely regenerated along with the fluoride. Since these
ions compete for the same adsorption sites with the fluoride, their presence
depletes the alumina capacity for fluoride. Arsenic presents a problem as it
is preferentially adsorbed over fluoride by the alumina at the same optimum pH.
Arsenic is more difficult to regenerate than fluoride. Therefore, when excess
fluoride and arsenic are present in a water supply, a special treatment tech-
nique is required. That subject is beyond the scope of this manual.
Modes of operation for this process are described in detail in Chapters 4,
5, and 6 of this manual.
Several investigators have developed varying theories that cover the
physical/chemical interaction between activated alumina and fluoride ions dur-
ing the separate modes' of operation. Singh and Clifford have researched this
subject. They suggest the following simplified series of chemical reactions to
explain the ion exchange adsorption of fluoride and the subsequent regenera-
tion of the packed bed of fluoride - exhausted alumina:
SIMPLIFIED PICTURE OF ALUMINA
ADSORPTION AND REGENERATION REACTIONS
1. NEUTRAL ALUMINA
Alumina + HOH Alumina HOH
2. ACIDIFICATION
Alumina HOH + HC1 Alumina HC1 + HOH
3. ION EXCHANGE IN ACIDIC SOLUTION
Alumina HC1 + NaF Alumina HF + NaCl
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4. REGENERATION
Alumina HF + 2NaOH Alumina NaOH + NaF + HOH
5. ACIDIFICATION
Alumina NaOH + 2HC1 Alumina HC1 + NaCl + HOH
2.3 ALTERNATE TREATMENT METHODS
Some of the methods that have been employed to remove excess fluoride from
potable water include bone char adsorption, ion exchange, reverse osmosis,
electrodialysis, alum coagulation and lime softening. A brief summary of these
methods is included for reference only.
The bone char process for fluoride removal is very similar to the
activated alumina process. It selectively removes fluoride (and arsenic) and
is regenerated by means of dilute caustic soda. However, it has drawbacks
which normally disqualify it when compared to activated alumina. The media
(when produced) cost 50 percent more than the alumina; its initial fluoride
capacity was far less than the alumina; its fluoride capacity was lost during
each successive regeneration; was susceptible to attack by low pH; and irrever-
sibly adsorbed arsenic. These negative characteristics have discouraged
further development of the bone char method.
Several full scale fluoride removal plants using bone char have been
operated for varying periods. The one most publicized was the USPHS plant at
Britton, South Dakota which operated from 1953 to 1971. The reported data
indicate that this plant removed 5 mg/1 fluoride and that the average fluoride
capacity of the media was 450 grains/cu ft.
There is no current interest in this method.
The ion exchange treatment method is not considered viable for the removal
of fluoride from potable water supplies. Strong base anion resins have the
ability to remove fluoride along with all other anions. However, the cost of
this treatment for potable water supplies is not compatible with the financial
resources of the small community. Some researchers have reported on this
method, but their findings are not favorable.
The reverse osmosis (R/0) process employs the use of semi-permeable mem-
branes for the separation of dissolved solids from water. The process is
primarily used to reduce the total dissolved solids (TDS) content of a water
supply. When used for potable water applications, its function is to reduce
the TDS to below the recommended maximum of 500 mg/1 which is a secondary EPA
standard. If the high TDS water also has excessive levels of fluoride, R/0 may
reduce the fluoride to a level within the MCL.
Fluoride ion rejection by R/0 membrane is pH and temperature sensitive.
At low pH (5.5), the fluoride rejection is close to 50 percent. Therefore,
adequate fluoride removal can only be accomplished at relatively low raw water
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fluor-ide concentrations ( 4 mg/1) unless the pH is raised. At the higher pH,
calcium fluoride precipitation creates membrane fouling problems. New mem-
brane development indicates that fluoride rejection approaching 90 percent can
be achieved in the lower pH range.
Reverse osmosis is an energy intensive process. Energy cost is a function
of raw water IDS and reject water flow rate. Although, under some conditions
higher product to reject water flow ratios (conversion) can be used, 75 percent
is usually an upper limit. Therefore, at least 25 percent of the raw water
pumped through the process must go to waste. Discharge of that water is also a
large cost item associated with this process. This water also contains at
least 90 percent of the original TDS in the raw water.
Desalting systems such as R/0 and electrodialysis (E/D) cannot be cost
competitive with the activated alumina process for the selective removal of
excess fluoride except for very small systems. This applies to both installa-
tion and operating costs. However, low solids water achieved by these proces-
ses produce other desirable qualities such as: low hardness, low sodium, and
low sulfate which may have appeal to select groups. Thereby, "high purity"
water could be an attraction in health oriented, prestige, or retirement
communities. In communities with very high population densities a two pipe
system (one with desalted water for potable service, the other with untreated
water for toilets, bathing, laundry, and irrigation) could be economically
feasible.
Electrodialysis is also a membrane separation method that is used to
remove dissolved salts from brackish water. The process removes ionized salts
from water by the passing of ions through ion permeable membranes by means of
direct current electrical energy. The membranes are stacked in pairs of
anionic and cationic permeable membranes. Raw water flows between pairs
through labyrinths which create turbulence while the direct current drives the
anions through the anion permeable membrane and the cations through the cation
permeable membrane. These ions collect in a reject stream which flows to waste
or can be partially recycled. As with R/0, the E/D process is not selective;
it removes all inorganic ions. It does not remove non-ionic dissolved solids
or suspended solids. Also, as with R/0, concentrations of ions in the brine or
reject stream can lead to precipitation of scale-forming material which can
foul the process. Presence of hardness, iron and manganese ions, can lead to
high maintenance cost. Membrane maintenance is an economic drawback for this
system.
The advantage of E/D is that it operates at low pressure where R/0 oper-
ates at pressures approaching 400 psig. E/D is still an energy intensive
process due to the current required to move the charged ions through their
respective membranes.
The E/D method like R/0 is not practical for selective removal of fluoride
from potable water. However, when fluoride is present in a brackish water
supply, and the capital requirements are within the means of the community,
9
2-4
-------
these membrane separation methods are technically capable of delivering the
desired treatment water quality.
Alum coagulation is a chemical precipitation process which employs alum,
an inorganic coagulant aid, to react with fluoride and other ions in solution
to form an insoluble solid^ This process, though effective for some applica-
tions, is expensive. Sorg reports on other researchers who found that 250
mg/1 of alum were required to reduce the fluoride level in a water supply from
3.5 mg/1 to 1.5 mg/1 and 350 mg/1 of alum were required to reduce the fluoride
level to 1.0 mg/1. Many variables such as pH, temperature, raw water chemistry
and mixing procedures affect this process.
Q Q 1 f\
Several investigators ' ' have shown that lime softening, a chemical
precipitation process, can remove fluoride from potable water supplies. The
fluoride removal mechanism is a co-precipitation with magnesium hydroxide.
Finkbeiner reported that according to his formula 70 mg/1 of magnesium must
be removed to reduce fluoride from 4 mg/1 to 1.5 mg/1 and 137 mg/1 magnesium
removal reduces fluoride from 8 mg/1 to 1.5 mg/1. If sufficient magnesium is
not present in the water, magnesium salt in appropriate quantities must be
added to accomplish the desired level of fluoride removal.
Because of the large quantities, and therefore costs, of chemicals
required, this method is very limited. It does apply to water supplies with
moderate levels of fluoride that require lime softening for large amounts of
magnesium.
2.4 REFERENCES
1. Sorg, T.J., "Treatment Technology to meet the Interim Primary Drinking
Water Regulations for Inorganics", AWWA Journal 70:105-112 (February
1978).
2. Alcoa Activated Aluminas, Form F37-14-370 (1982).
3. Rubel, F. and R.D. Woosley, Removal of Excess Fluoride from Drinking
Water, EPA Technical Report 570/9-78-001 (January 1978).
4. Rubel, F. and F.S. Williams, Pilot Study of Fluoride and Arsenic Removal
from Potable Water, EPA Report 600/2-80-100 (August 1980).
5. Singh, G. and D.A. Clifford, The Equilibrium Fluoride Capacity of Activ-
ated Alumina, EPA Report 600/S2-81-082 (July 1981).
6. Thompson, J., and F.Y. McGarvey, Ion Exchange Treatment of Water
Supplies, AWWA Journal 45:2:145 (February 1953).
7. Katz, W.E., Electrodialytic Saline Water Conversion for Municipal and
Governmental Use, Proceedings of Western Water and Power Symposium, Los
Angeles, California (April 8-9, 1968).
10
2-5
-------
8. Boruff, C.S., A.M. Buswell, and W.V. Upton, Adsorption o£ Fluorides from
Salt by Alum Floe. Ind. Engrg. Chem. 29:10:1154 (October 1937).
9. Scott, R.D., et al. Fluoride in Ohio Water Supplies-Its Effect. Occur-
rence, and Reduction Journal. AWWA, 29:1-9 (January 1937).
10. Finkbeiner, C.S. Fluoride Reduction Plant Installed at Village of Bloom-
dale, Ohio. Water Works Engrg. 91:7:990 (July 1938).
11
2-6
-------
CHAPTER 3
DESIGN OF CENTRAL TREATMENT SYSTEM
3.1 INTRODUCTION
The design of a central treatment plant for the selective removal of
fluoride from potable water supplies is a straightforward process. Fluoride
removal treatment can be applied to existing potable water systems that have a
history of high fluoride and new wells with high fluoride which must be reduced
prior to being allowed to deliver to distribution.
The designer must be careful to clearly define the design criteria prior
to initiating the preliminary design. The most important items are the
following:
1) Comprehensive chemical analyses (see Figure 3-1) of representative raw
water samples (includes all historical analyses).
2) Treated water quality compliance standards issued by the regulatory
agency within whose jurisdiction the system resides.
3) Wastewater discharge ordinance issued by the responsible regulatory
agency.
4) Accurate data on system production and consumption requirements (present
and future).
5) State and local codes and health department requirements.
6) Comprehensive climatological data.
The treatment system is a subsystem within the larger water utility
system. Other subsystems are the well pump, the storage reservoirs, the
pressurization system and the distribution system. Defluoridation generally
is the only treatment required; however, removal of other contaminants such as
bacteria, suspended solids, hardness, organics or other objectionable qual-
ities may also be required.
The sequence of other treatment steps must be compatible with fluoride
removal. Removal of suspended solids, organics and hardness should take place
upstream of the fluoride removal process. Disinfection with chlorine should
12
3-1
-------
EXAMPLE
FLUORIDE REMOVAL WATER TREATMENT PLANT
REPORT OF WATER ANALYSIS
NAME AND ADDRESS
SOURCE OF WATER
CONTAINER
SAMPLE DATE
TAKEN BY:
Analysis No. /Date
^ Calcium
z Magnesium
£ Sodium
o
=> Total Cations
^ Total Alkalinity(M)
o
Phenalphthalein
< Alkalinity (P)
o Total Hardness
IJ Sulfate
2: Chloride
% Nitrate
Q. ' "
ifi
ec
*- Total Non-Carbonate
Solids
Silica
Free Carbon Dioxide
Iron (Fe) Unfiltered
o Iron (Fe) Filtered
-j Manganese (Mn)
r Turbidity
£ Co1or
n
Fluoride
^ Arsenic
o.
PH
Specific Conductance
(micromhos)
Temperature (UF)
WATER ANALYSIS REPORT FORM
FIGURE 3-1
13
3-2
-------
take place after fluoride removal because chlorine exposure degrades activated
alumina performance. No known investigation has revealed the amount of chlo-
rine that can be tolerated by the alumina; however, process degradation has
been eliminated on projects where pre-chlorination was terminated. Other
treatment processes may be required upstream of the fluoride removal, but the
decision must be made on a case by case basis.
The most practical concept is to install the treatment plant in the
immediate vicinity of the well (space permitting). The well pump will then
deliver the water through treatment into distribution and/or storage. If the
existing well pump is oversized (pumps at a much higher flow rate than the
maximum daily requirement), it should be resized to deliver slightly more (say
125 percent) than the peak requirement, the reason being that the flow rate
dictates the treatment equipment size and therefore, the capital cost.
Reducing flow rate for an oversized pump results in excessive energy costs. As
explained later, the treatment media volume is a function of flow rate.
Consequently, the treatment vessels, pipe sizes and chemical feed rates all
increase as the flow rate increases. Storage should be provided to contain a
minimum of one half the maximum daily consumption requirement. This is based
on the premise that consumption takes place during twelve hours of the day.
Then, if treatment operates during the entire twenty four hours, storage draw-
down occurs during twelve hours and recovers during the remaining twelve hours.
Materials of construction must comply with local building code and health
department requirements in addition to being suitable for the pH range of 2-13.
Treatment system equipment must be protected from the elements. Although not
mandatory, it is prudent to house the system within a treatment building.
Wastewater resulting from backwash and regeneration of the treatment media can
only be discharged in accordance with local ordinance. There are several
options for disposal; however, they are subject to climate, space and other
environmental limitations. Since each of the variables can significantly
affect both capital and operating costs, the designer must carefully evaluate
the available wastewater handling options prior to making conceptual selec-
tions.
Throughout this manual English Units are employed. For designers working
with Metric Units, a tabulation of English to Metric conversion is provided in
Appendix E.
3.2 CONCEPTUAL DESIGN
The basic design for an activated alumina fluoride removal water treat-
ment plant is very flexible. This stage of design provides a definition of the
process. However, it does not provide equipment size, arrangement, material
selection detail or specifications.
The designer has four basic options from which to select a conceptual
design. Every combination of options will perform the process and, under a
14
3-3
-------
selected set of conditions, a certain combination may be preferred. The
options are as follows:
1) gravity or pressure flow
2) single or multiple treatment bed(s)
3) upflow or downflow treatment flow direction
4) series or parallel treatment vessel arrangement
Through extensive experimentation the most efficient, cost effective
configuration was found to be the parallel downflow multiple bed pressure
system. For maximum cost effectiveness (both capital and operating) two treat-
ment beds are optimum. The two bed series configuration yields the highest
fluoride loading on the treatment media and the lowest treated water fluoride
level. However, this low fluoride level is undesirable and the benefits
(economy and water quality) achieved in the blending of treated product water
of the parallel bed configuration (described in Chapter 5) are not available.
The multiple bed parallel configuration also provides greater flexibility in
treatment flow rate than the series configuration. The single treatment unit
configuration is less efficient unless there is an exceptionally large treated
water storage capacity. In that case, the economy of treated water blending
can take place in storage. Because of the space and capital requirements, this
is not an economic concept. A gravity flow system does not provide the
economics of a pressure system. Treatment flow rates are lower; repumping of
treated water is always required; and capital costs are higher. Unless extra-
ordinary measures are taken to allow for loss of head, gravity flow can be
sensitive to fine suspended solids in the raw water. Downflow treatment in
pilot test experiments has consistently yielded higher fluoride removal
efficiency than upflow. Since the downflow concept utilizes a packed bed, the
flow distribution has been superior. If the upflow beds were restrained from
expanding, they would in effect also be packed. However, they would forfeit
the necessary capability to backwash. Once the bed configuration is defined, a
basic schematic flow diagram is prepared (See Figure 3-2). This diagram
presents all of the subsystems. A summary of this information, including
subsystem components, is listed in Appendix A. Figure 5-3 is included in
Chapter 5, "Treatment Plant Operation", to assist the designer in under-
standing the flow pattern for a treatment unit during each mode of operation.
Regeneration wastewater treatment is a separate technology which can be
handled by several different processes. That subject is beyond the scope of
this manual. For this design manual the lined evaporation pond concept is
implemented for disposal of regeneration wastewater. This concept is only
applicable in arid climates where evaporation rates are high and land required
for the basins is available at low cost. In regions where evaporation rates
are low, backwash and regeneration wastewater can be neutralized and contained
in a surge tank from which slow discharge to a sewer system is permissible.
This latter disposal method can only be employed when local-regulatory agency
approval is provided.
15
3-4
-------
Raw Water
Sample
PH
SENSORl
Treated Water To
_T* Indicator & Alarm
CAUSTIC
PUMPS
CAL
0
A A
.Vent
Vo
STIC DAY
TANK
ACID-
PUMPS
TREATMENT
UNIT NO. 2
—00
CAUSTIC STORAGE
TANK
^Vent
ACID DAY
TANK
ACID STORAGE
TANK
-| Future Conn.
H Future Conn.
^Backwash Wastewater
Regeneration Wastewater
LINED EVAPORATION POND
FIGURE 3-2 BASIC FLOW DIAGRAM
16
3-5
-------
Prior to proceeding with the design, financial feasibility must be deter-
mined. Funding limits for the project must be defined. The designer must make
a determination that funding is available to proceed with the project; this
requires a preliminary rough project estimate with an accuracy of plus or minus
thirty percent (+30%). If the preliminary rough estimate exceeds the available
funds, adjustments must be made to increase funding or reduce project costs.
Prior to proceeding into the next phase, Preliminary Design, the designer
must finalize the Design Criteria listed in Section 3.1.
3.3 PRELIMINARY DESIGN
After completion and approval of the Conceptual Design by the client, the
regulatory agency(s), and any other affected party, the designer proceeds with
the Preliminary Design. This includes sizing of the equipment, selecting
materials of construction, determining an equipment layout and upgrading the
Preliminary Capital Cost Estimate to a 20 percent (j+20%) accuracy. The
deliverable items are:
1) Process & Instrumentation Diagrams (See Figures 3-3.1 and 3-3.2)
2) Preliminary Process Equipment Arrangement Drawings (See Figures 3-5 and
3-6)
3) Outline Specifications
4) Preliminary Capital Cost Estimate (See Figure 3-7)
Upon completion and approval of the Preliminary Design, the designer
proceeds with the Final Design.
3.3.1 Treatment Equipment Preliminary Design
This section provides the basic methodology for sizing equipment items
and selecting materials of construction. An example illustrating this method
is provided in Appendix B.
3.3.1.1 Treatment Bed and Vessel Design
Per discussion presented in Section 3.1, the recommended treatment
concept is based upon the use of two treatment pressure vessels piped in
parallel using the downflow treatment mode. The recommended materials of
construction are carbon steel (grade selection based upon cost effective
availability) for ASME Code - Section VIII, Division 1 pressure rating with
3/16 in. thick potable water grade natural rubber interior lining. Vessel
pressure rating to be minimum necessary to satisfy system requirements.
Basic technology which has evolved from experience at existing central
plants dictates that the volume of treatment media (V) be one cubic foot per
17
3-6
-------
Acid - 1/2" 316 S.S.
70-50 PSI
HX»—&- TV
Sample
1/2* PVC
pH SENSOR
LEGEND
PVC - Polyvlnyl Chloride
C.S.- Carbon Steel
S.S.- Stainless Steel
fX - Shut-off Valve
S! - Butterfly Valve
r-s| - Check Valve
IS] - Pressure Control Valve
H - Expansion Joint
- Pressure Indicator
- Temperature Indicator
- Pressure Indicator/Totalizer
- Pressure Relief Valve
$/S - Straight Side
Sample -1/2"PVC
Backwash Wastewater-
'6"PVC
Regeneration Wastewater
LINED EVAPORATION POND
TREATMENT UNITS NO. 1 & 2
Vertical Cylindrical C.S.
Pressure Vessel
ASME Code 50 PSIG § 175°F
9'-0" Dia.x 8'-0" S/S
Lining-3/16" Natural White
Rubber
NOTE
The Design Data Shown on
This Diagram Are Taken From
Example in Appendix B
FIGURE 3-3.1 PROCESS AND INSTRUMENTATION DIAGRAM (P & ID)
18
3-7
-------
< *".
3 CO
- CO
0«
^/ ^B
£C UJ
o w
£co
Acid 1/2"316 S.S
*
Acid 1/2" 316 S.S
I
to
6
•
t-
,0
*-
0}
3
CO
O
CO*
t
p
*
' w
*»*
T
_0
•»*
(0
s
«
o
X '
U. '
P3 k>4
ACID PUMPS T^
T
r-, 2"C.S.
r
P4
]
**
c
o
> /•
/
/
r »IM*«A
^^Vent 2"C.S.
* *\ -
0 \ =
»- 1 U.
w TO 1
1
o y i-M-t»4-
2"c-s- P 4 Drain
Apin "TnnAr**r TAMIIT
- MOIL/ O 1 w ri rt O C. IMIMrx
ACID DAY TANK-T4
pH ADJUSTMENT ^<}ID STORAGE ACID DAY
ACID PUMPS -P3 ,P4 TANK -T2 TANK-T4
PVC Head, Teflon 5000 Gallon C.S. 100 Gallon
Diaph., 0.5-5.0 GPH Horizontal Cycindrical Polypropylene
50 PSIG., 110V, 10, 60 HZ, Pressure Vessel Cycindrical,
Interlock W/Well Pump 8 ' -0"0 x 11'-6"S/Sx h" tw. Flat Bottom
W/Cover
y" c.s.
J
'
£ i
PI rk 1P2
, CAUSTIC U h
PUMPS
-3..
1
4-*
C
> /
/
r «I»*A^
p^Vent 2" C.S.
? -\
£ \ =
JTi 1 ,
^ 1 "-
® Tl 1
> y i ^^
j
Vy.O. -1 5
-1 CAUSTIC STORAGE TANK
CAUSTIC DAY TANK-T3
REGENERATION
CAUSTIC PUMP-PI
Cast Iron Positive Displacement
2 GPM, 50 PSIG, 110V, 10, 60 HZ
Interlock W/Well Pump
pH ADJUSTMENT
CAUSTIC PUMP -P2
CAUSTIC STORAGE
TANK -Tl
PVC Head, Teflon
Oiaph.,0.25-2.5 GPH
50 PSIG.,110V,10,60HZ
5000 Gallon C.S.
Horizontal Cycindrical
... Pressure Vessel
Interlock W/Well Pump 8'-0"0 x U'-6" S/S X 3/8" tw.
W/10KW Inversion
Heater
CAUSTIC DAY
TANK -T3
150 Gallon
Polypropylene
Cycindrical
Flat Bottom
W/Cover
FIGURE 3-3.2 PROCESS AND INSTRUMENTATION DIAGRAM (P & ID)
19
3-8
-------
gallon per minute of treated water flow rate (g). This provides a superficial
(or empty bed) residence time of 7.5 minutes, which is conservative. Actual
residence time is approximately half the superficial residence time. That is
true because the space between the grains of media is approximately 50 percent
of the total bed volume. Where multiple beds are used, the volume of treatment
media per unit is equal to the total treatment flow rate divided by the number
of treatment beds (N). See Figure 3-4 for Treatment Unit illustration. (NOTE:
When raw water is bypassed and blended back with treated water, only the
treated water is included in sizing the bed.) In order to prevent "wall
effects", bed diameter (d) should be equal or greater than the bed depth (h).
Good practice dictates that bed depth be a minimum of three feet and a maximum
of six feet. At lesser than minimum depth, distribution problems may develop;
and, at greater than maximum depth, fine material removal and pressure loss may
become a problem.
At the Gila Bend, Arizona fluoride removal plant, there are two 10 ft-
0_in. diameter by 5 ft-0 in. deep treatment beds. At design flow each 380
ft bed treats 380 gpm. Each treatment unit operates at 450 gpm during peak
consumption periods. Each unit has been successfully operated at treatment
flows as high as 600 gpm, a treatment rate that exceeds one and one-half
gallons per minute per cubic foot. That flow rate reduces the superficial
residence time to five minutes which is recommended as a minimum limit. As the
superficial residence time decreases, two undesirable features occur. First,
the treatment is less efficient, that is, treated water fluoride concentration
does not reach as low a level; and second, regeneration frequency increases
requiring more operator attention and proportionately more downtime for
regeneration of the beds. Conversely, lowering the treatment flow rate below
the suggested 1 gpm/ft level increases the size of the treatment beds and
their vessels, thereby increasing capital cost and space requirements.
Pressure vessel fabrication is standardized by diameter in multiples of
6 in. increments. Tooling for manufacture of pressure vessel dished heads is
set up for that standard. Design dimensions differentiate between pressure
vessel and treatment bed diameters. The vessel outside diameter (D) is approx-
imately 1 in. greater than the bed (or vessel inside) diameter which provides
for both vessel walls with lining. If the pressure is high (100 psig or
greater) the 1 in. will increase to reflect the increased vessel wall thick-
ness.
Although there are many methods of distributing the water flow through a
treatment bed, the method which has been successfully used in fluoride removal
plants that are presently in operation is recommended. The water is piped
downward into the vessel. This diverts the flow into a horizontal pattern.
From there it radiates in a horizontal plane prior to starting its downward
flow through the bed. The bed, in turn, is supported by a false flat bottom
which is supported by the bottom head of the vessel by means of concentric
rings. The false flat bottom also supports the horizontal header and plastic
fabric sleeved perforated lateral collection system. Treatment media is
placed in the vessel through a circular manway (minimum diameter 16 in.) with
20
3-9
-------
FREEBOARD
50% BED
EXPANSION
TREATMENT
MEDIA
TREATMENT VESSEL
SYMBOLS
q - Treated water flow rate (gpm)
N - Number of Treatment Beds.
d - Treatment bed diameter (ft.)
h - Treatment bed depth (ft.)
V - Treatment bed volume - ird h (ft. )
Md - Density of Treatment Media (Ib./ft. )
M - Weight of Media
D - Outside diameter of Treatment Vessel (ft.)
du - Depth of Dished Pressure Head (ft.)
H
H - Overall height of Treatment Vessel (ft.)
GIVEN
h < d, 3'-0" < h < 6'-0", V - C./N (ft.3)
H - 2 dH + h + h/2 + 6", d - *»q/N -a h
D - d + 1"
M. • 50 Ib./ft (varies with packing characteristics of media in vessel)
M^ - Md x V - 50V (Ib.)
FIGURE 3-4 TREATMENT BED AND VESSEL DESIGN CALCULATIONS
21
3-10
-------
4'-0"
*
CAUSTIC
STORAGE TANK
TREATMENT
UNIT NO. 2
TREATMENT
UNIT NO. 1
FIGURE 3-5 PRELIMINARY EQUIPMENT ARRANGEMENT PLAN
22
3-11
-------
hinged cover in the top head of the vessel. The Treatment Bed and Vessel
Design is illustrated in Figure 3-4. A typical example for determining treat-
ment bed and treatment vessel dimensions is presented in Appendix B.
3.3.1.2 Pipe Design
Material must be suitable for ambient temperature, pH 2-13, system press-
ure and potable water service. Due to the low pH, carbon steel is not accept-
able. Stainless steel is acceptable; however, it is too costly. There are
several plastic materials such as PVC, polypropylene, and high density poly-
ethylene that are satisfactory. Of those, PVC is usually the best selection
because of its availability and ease of fabrication and assembly. The draw-
backs to the plastic materials are their loss of strength at elevated tempera-
tures (above 100 F); their coefficient of thermal expansion; their external
support requirements; their deterioration from exposure to sunlight; and their
vulnerability to damage from impact. Nevertheless, these liabilities are
greatly outweighed by the low cost and suitability for the service. The
designer can easily protect the piping from all of the above concerns, except
elevated ambient and/or water temperatures. If elevated temperature exists,
the use of polypropylene lined carbon steel flanged pipe (and cast iron
fittings) is recommended. This material provides the strength and support that
is lacking in the pure plastic materials.
The designer must economically size the piping system to allow for deliv-
ery of design flow without excessive pressure losses. If water velocities
present conditions for water hammer (due to fast closing valves, etc.), the
designer must include shock absorbing devices to prevent that occurrence.
Isolation and process control valves should be wafer style butterfly
type, except in low flow rate systems where small pipe size dictates the use of
true union ball valves (See Figure 3-2 for location). The use of inexpensive,
easily maintained valves that operate manually is recommended. The valves
could also be automated by the inclusion of pneumatic or electric operators and
controls. Automation is not recommended because the cost of the hardware and
its maintenance outweighs the savings of plant operators' time.
See Appendix B for pipe;size design using the example previously employed
for vessel and treatment media design.
3.3.1.3 Instrumentation Design
Design is a misnomer for this category of equipment. Literally the
designer specifies the system functional requirements which are adapted to
commercially available instruments. Included are:
Instrument Range Accuracy
pH sensor/indicator/alarm 0-14 +^ 0.1
pressure indicator varies* +_ 1%
temperature indicator (optional) 30 -120 F +_ 1%
flow indicator/totalizer varies* +_ 2%
*range to be compatible with application, maximum measurement not to exceed
90 percent of range.
23
3-12
-------
3.3.1.4 Acid Storage and Feed Subsystem
The acid storage tank is sized to contain tank truck bulk delivery quanti-
ties of concentrated sulfuric acid. Bulk delivery provides the lowest unit
price for the chemical. In small plants (less than 175 gpm) acid consumption
may not be enough to justify large volume purchase of chemicals. In the
smaller plants, drums or even carboys may be more practical; therefore, for
that type operation, the requirement for a storage tank is eliminated. A
50,000 pound tank truck delivers 3,250 gallons of 66 B'H^O (15.5 Ib/gal). A
5,000 gallon tank provides a 50 percent cushion. The example in Appendix B
illustrates the method of designing the components of this system.
The carbon steel tank does not require an interior lining; however, the
interior must be sand blasted and vacuum cleaned prior to filling with acid.
The storage tank must be placed outside of the treatment building. The
66 B'H SO, freezes at -20 F. Therefore unless the treatment plant is located
in an extremely cold climate, no weather protection is required. The tank
should be painted white to reflect sunlight; this will prevent heat gain in the
tank which heats the acid making it more aggressive. All piping is to be 2 in.
carbon steel with threaded cast iron fittings.
The acid pumps are standard diaphragm models with materials of construct-
ion suitable for 66 B'H.SO, service. Standard chemical pumps are specified by
the designer. In the preliminary design, the sizing is adequate for layout and
estimating. Acid feed rate varies with the total alkalinity and the free
carbon dioxide content of the raw water, and in some cases, is much higher,
requiring larger pumps and day tanks. The actual acid feed rate is easily
determined experimentally by adjusting a raw water sample pH to 5.5 by acid
titration. Acid consumption for raw water pH reduction ( is discussed in
Appendix C. In normal treatment plant operation, the water quality will vary
from time to time. Therefore, the plant operator must check the pH period-
ically and maintain it at 5.5. The pump stroke speed and length are to be
adjustable to accommodate these variations. The pH probes that are used to
control pH must be calibrated against standard buffers at least once per month.
3.3.1.5 Caustic Soda Storage and Feed Subsystem
The caustic soda storage tank is also sized to contain tank truck bulk
delivery quantities of 50 percent sodium hydroxide. The caustic is used for
treatment bed regeneration and neutralization of treated water. Regeneration
frequency is a function of raw water fluoride concentration, flow rate and
treatment media fluoride capacity. The amount of caustic required to
neutralize the treated water, that is to raise the pH from 5.5 to 7.5, varies
considerably. The actual caustic feed rate is easily determined experi-
mentally by readjusting the treated water pH by titrating a sample with caustic
until the desired pH is achieved. In raw water with high alkalinity the
lowering of pH produces high levels of dissolved carbon dioxide (CO.). In
those waters removal of the CO^ by aeration raises the pH to the desirea level
providing a less expensive alternative than addition of caustic. In low
alkalinity water the chemical addition is less expensive. The sizing of the
carbon steel caustic storage tank is covered in Appendix B. This vessel must
24
3-13
-------
be heat treated to stress relieve welds. The carbon steel does not require an
interior lining; however, it does require sand blasting and vacuum cleaning
prior to filling. All piping is to be 2 in. carbon steel with threaded cast
iron fittings.
Fifty percent sodium hydroxide freezes at 55 F; therefore, it must main-
tain a minimum temperature of 70 F. This is handled by a temperature
controlled electrical immersion heater. For safety reasons the storage tank
must be outside of the treatment building where ambient temperatures might drop
quite low. To conserve electrical energy required for heating, the storage
tank may be insulated and/or housed in a separate enclosure. If not insulated
or housed, the tank must be painted white to reflect sunlight and prevent
chemical overheating.
A pump is required to feed 50 percent NaOH into the effluent main where
the low pH treated water is neutralized. For regeneration, a larger caustic
feed pump is required for pumping the concentrated caustic to a mixing tee in
the raw water branch pipe. In the mixing tee the caustic is diluted to the 1
percent (by weight) concentration required to regenerate the treatment bed.
3.3.1.6 Wastewater Lined Evaporation Pond
In the example used in Appendix B we have assumed that the wastewater
disposal option that is most cost effective as well as preferred by the regu-
latory agency is a lined evaporation pond. This method is used in arid regions
in the desert southwest. It is not a viable method in the humid southeast or
cold climate of the northern tier of states. In those areas a viable disposal
option is to neutralize the regeneration wastewater with acid as it leaves the
treatment vessel and collect the entire regeneration wastewater batch in a
surge tank. The neutralized wastewater is then bled at a controlled flow rate
to the sanitary sewer. In the sewer it blends with the defluoridated water
that has been discharged to waste.
To size the lined evaporation pond the basic information required is the
average annual volume of regeneration wastewater to be evaporated and the
average annual evaporation rate. The former is determined by the designer and
the latter is obtained from the national weather bureau (or in some cases,
state university climatological departments). Treatment plant production is
normally much higher in summer than winter, and evaporation rate is also
correspondingly higher in summer. The ponds have sloped sides, pond depth to
be 8 ft (minimum). Ponds are to be lined with 30 mil reinforced hypalon, a
material that is not vulnerable to ultraviolet radiation deterioration or
exposure to pH 12. The dissolved solids will concentrate and precipitate in
the pond.
3.3.2 Preliminary Equipment Arrangement
With all of the major equipment size and configuration information avail-
able, the designer proceeds to prepare a layout (arrangement drawings). The
layout provides sufficient space for proper installation, operation and main-
tenance for the treatment system as well as each individual equipment item.
^ O
3-14
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U.S. Occupational Health and Safety Administration (OSHA) regulations must be
applied to the designer's decisions during the equipment arrangement effort.
These requirements may be supplemented or superceded by state or local health
and safety regulations, or, in some cases, insurance regulations. The designer
must also adhere to a compact arrangement to minimize space and resulting cost
requirements. Figures 3-5 and 3-6 illustrate a typical preliminary arrange-
ment plan and elevation. This arrangement provides no frills; but it does have
ample space for ease of operation and maintenance. Easy access to all valves
and instruments reduces plant operator effort.
The building that protects the treatment system (and operator) from the
elements is normally a standard pre-engineered steel building. These build-
ings which are modularized units are low cost. The designer selects the
standard building dimensions that satisfies the installation, operation and
maintenance space requirements for the treatment system. There are many
suppliers of this type of building; installed costs are highly competitive.
The building must provide access doors, emergency shower and eye wash, and a
lab bench with sink. All other features are optional.
When the arrangement is completed, the designer can proceed with the
preliminary cost estimate.
3.3.3 Preliminary Cost Estimate
The designer prepares the preliminary cost estimate based upon the equip-
ment that has been selected, the equipment arrangement and the building selec-
tion. The designer then takes off the equipment, applies unit prices to labor
and material, and finally summarizes in a format that is preferred by the
owner. (See Table 3-1 for example). This estimate is to have an accuracy of
plus or minus 20 percent (j+20%). In order to assure sufficient budget for the
project it is prudent to estimate on the high side at this stage of design.
This may be accomplished by means of a contingency to cover unforeseen costs,
an inflation escalation factor, or estimating with budget prices furnished by
suppliers and contractors. Budget prices are roughly 10 percent higher than
competitive bid prices.
26
3-15
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CO
I
FRONT ELEVATION
ACID STORAGE TANK
II
SIDE ELEVATION
FIGURE 3-6 PRELIMINARY EQUIPMENT ARRANGEMENT ELEVATIONS
-------
TABLE 3.1. PRELIMINARY COST ESTIMATE-EXAMPLE FOR
FLUORIDE REMOVAL WATER TREATMENT PLANT
PRELIMINARY CAPITAL COST ESTIMATE
Location:
Flow Rate: 600 gpm
Date:
Process Equipment Cost, $
Treatment Vessels 37,000
Treatment Media 21,000
Process Piping, Valves and Accessories 18,000
Instruments and Controls 10,000
Chemical Storage Tanks 22,000
Chemical Pumps, Piping and Accessories 6,000
Subtotal 114,000
Process Equipment Installation
Mechanical 35,000
Electrical 10,000
Painting and Miscellaneous 5,000
Subtotal 50,000
Miscellaneous Installed Items
Wastewater Lined Evaporation Pond 140,000
Building and Concrete 30,000
Site Work, Fence and Miscellaneous 10,000
Subtotal 180,000
Contingency 10% 36,000
*Total 380,000
*Engineering, Finance Charges, Real Estate Cost and Taxes not included.
3.3.4 Preliminary Design Revisions
The Preliminary design package (described above) is then submitted for
approval prior to proceeding with the Final Design. This package may require
the approval of regulatory authorities, as well as the owner. If there are any
changes requested, the designer must incorporate them and resubmit for
approval. Once all requested changes are included and Preliminary Design
approval is received, the designer can proceed with the Final Design.
3.4 FINAL DESIGN
After completion and approval of the Preliminary Design by the client et
al, the designer proceeds with the Final Design. This includes detail design
' 6 28
3-17
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of all of the process equipment and piping, complete process system analysis,
complete detail design of the building including site work, and a final capital
costs estimate accurate to within ten percent. The deliverable items are:
1) Complete set of construction plans and specifications
2) Final Capital Cost Estimate (See Table 3-2)
TABLE 3.2. FINAL COST ESTIMATE-EXAMPLE FOR
FLUORIDE REMOVAL WATER TREATMENT PLANT
FINAL CAPITAL COST ESTIMATE
Location:
Flow Rate: 600 gpm
Date:
Process Equipment Cost, $
Treatment Vessels 33,000
Treatment Media 20,500
Process Piping, Valves and Accessories 16,400
Instruments and Controls 8,300
Chemical Storage Tanks 21,000
Chemical Pumps, Piping andf Accessories 6,300
Subtotal 105,500
Process Equipment Installation
Mechanical . 36,000
Electrical 7,000
Painting and Miscellaneous 4,500
Subtotal 47,500
Miscellaneous Installed Items
Wastewater Lined Evaporation Pond 138,000
Building and Concrete 28,000
Site Work, Fence and Miscellaneous n,QQQ
Subtotal 177,000
Contingency 4% 17,000
*Total 347,000
*Engineering, Finance Charges, Real Estate Cost and Taxes not included.
29
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The designer starts the Final Design with the treatment system equipment
(including the lined evaporation pond); continues with the building (including
concrete slabs and foundations, earthwork excavation/backfill/compaction,
heating, cooling, bathroom, painting, lighting and utilities); and completes
with the site work (including utilities, drainage, paving and landscaping).
The latter items apply to every type of treatment plant; but, though they are
integral with the treatment system, they are not addressed in this manual. The
only portions of the Final Design that will be discussed are the pertinent
aspects of the treatment equipment which were not covered in the Preliminary
Design sections. During the Conceptual Design and Preliminary Design the
designer concentrated on defining the basic equipment that accomplished the
required function. The decision was cost conscious using minimum sizes (or
standard sizes) and least expensive materials that satisfied the service
and/or environment. However, in the Final Design this effort can be defeated
by not heeding simple basic cost control principles. Some of these are:
1) Minimize detail (e.g. pipe supports-use one style, one material and
components common to all sizes).
2) Eliminate bends in pipe runs (some bends are necessary - those that
are optional increase costs).
3) Minimize field labor-shop fabricate where possible (e.g. access
platforms and pipe supports can be supported by brackets that are
shop fabricated on vessel).
4) Skid mount major equipment items (skids distribute weight of vessels
over large floor areas, thereby costly foundation work is
eliminated).
5) Use treatment vessels as heat sink to provide building cooling or
heating or both. (Eliminates heating and/or cooling equipment in
addition to reducing energy cost.)
6) Simplify everything.
Besides holding down costs the designer must analyze all subsystems
(refer to P&ID in Figures 3-3.1 and 3-3.2) and account for all components in
both equipment specifications and installation drawings. The drawings must
provide all information necessary to manufacture and install the equipment.
The designer must exercise extra effort to eliminate ambiguity in detail and/or
specified requirements. All items must be satisfactory for service conditions
besides being able to perform required functions. Each item must be easy to
maintain; spare parts necessary for continuous operation must be included with
the original equipment. All tools required for initial startup as well as
operation and maintenance must be furnished during the construction phase of
the project. Once construction, equipment installation and check out are com-
plete, the treatment plant should proceed into operation without disruption.
30
3-19
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When all components in each of the subsystems have been selected, the
designer should run hydraulic analysis calculations to determine the
velocities and pressure drops through the system. Calculations are to be run
for normal treatment flow and backwash flow. The latter is more severe but of
short duration. If pressure losses are excessive, the designer must modify the
design by decreasing or eliminating losses (e.g., increase pipe size,
eliminate bends or restrictions).
The designer must include several functional checkout requirements to be
accomplished upon completion of installation. All piping must be cleaned and
pressure tested prior to startup. All leaks must be corrected and retested.
Recommended test pressure is 150 percent of design pressure. Potable water
piping and vessels must be disinfected prior to startup. All electrical
systems must satisfy a functional checkout. All instruments are to be cali-
brated; if accuracy does not meet requirements stated in Section 3.3.1.3, the
instruments are to be replaced.
When the plant operation begins, a check on actual system pressure drop is
required. If there is a discrepancy between design and actual pressure drop,
the cause must be determined (obstruction in line, faulty valve, installation
error, design error, etc.) and rectified. Pressure relief valves must be
tested; if not accurate, they must be adjusted or replaced.
3.4.1 Treatment Equipment Final Design
This section provides discussion on details that apply specifically to
Fluoride Removal Water Treatment Plants.
3.4.1.1 Treatment Bed and Vessel Design
The treatment medium was designed by determination of bed dimensions and
resulting weight in the Preliminary Design (see Section 3.3.1.1). It is
recommended that ten percent extra treatment medium be ordered. For lowest
price and ease of handling, the material is to be ordered in 100 pound bags on
pallets. The material specification requires Alcoa F-l, 28+48 mesh activated
alumina, or equal (see Section 1.2). If an "equal" is to be furnished, a pilot
test must demonstrate that the process capability as well as the physical
durability of the substitute material be equal to that of the specified
material.
The vessel design must be simple. The vessel must have a support system
to transfer its loaded weight to the foundation and ultimately to the soil.
The loaded weight includes the media, the water, attached appurtenances (plat-
form, pipe filled with liquid, etc.) as well as the vessel itself. The support
legs should be as short as possible reducing head room requirements as well as
cost. The legs are to be integral with a support frame (skid) that will
distribute the weight over an area greater than the dimensions of the vessel.
This distribution eliminates point loads of vessel support legs, thereby
costly piers, footings, and excavation requirements are eliminated. The skid
31
3-20
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must have provisions for anchorage to the foundation. Exterior brackets (if
uniform and simply detailed) are not costly and provide supports that eliminate
need for cumbersome costly field fabrications. Conversely, interior brackets
though required to anchor (or support) vessel internal distribution or collec-
tion systems must be held to bare minimum as they are very costly to rubber
line. Rubber lining is recommended over less costly coatings because of its
resistance to granular activated alumina abrasion. Rubber lining resiliency
provides better resistance to abrasion than hard epoxy type linings. Vessel
interior lining is to extend through vessel openings out to the outside edge of
flange faces. Openings in the vessels must be limited to the following:
1) Influent pipe - enters vertically at center of top head.
2) Effluent pipe - exits horizontally through vertical straight side
immediately above false flat bottom in front of vessel.
3) Air/vacuum valve (vent) - mounts vertically on top head adjacent to
influent pipe.
4) Media Removal - exits horizontally through vertical straight side
immediately above false flat bottom at orientation assigned to this
function.
5) Manway - 16 in. diameter (minimum) mounted on top head with center
line located within three feet of center of vessel and oriented
towards work platform. Manway cover to be hinged or davited.
It is recommended that pad flanges be used for pipe openings in lieu of
nozzles. Pad flanges are flanges that are integral with the tank wall. The
exterior faces are drilled and tapped for threaded studs. These save cost of
material, labor and are much easier to line; they also reduce the dimensional
requirements of the vessel. The vessel also requires lifting lugs suitable for
handling the weight of the empty vessel during installation. Once installed
the vessel must be shimmed and leveled. All space between the bottom surface
of the skid structure and the foundation must be sealed with an expansion type
grout; provisions must be included to drain the area under the vessel.
The type of vessel internal distribution and collection piping used in
operational fluoride removal plants is defined in the Preliminary Design (see
Section 3.3.1.1). Since there are many acceptable vessel internal design
concepts, configuration details will be left to sound engineering judgement.
The main points to consider in the design are as follows:
1) Distribution to be uniform
2) Provide minimum pressure drop through internal piping (but
sufficient to assure uniform distribution)
3) Prevent wall effects and channeling
32
3-21
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4) Collect treated water within two inches of bottom of treatment bed
5) Anchor internal piping components to vessel to prevent any hori-
zontal or vertical movement during operation
6) Materials of construction to be suitable for pH range of 2-13, (PVC,
polypropylene, stainless steel are acceptable)
Underdrain failures are undesirable; treatment media loss, service dis-
ruption and labor to repair problems are very costly. A service platform with
access ladder is required for use in loading treatment media into the vessel.
Handrail, toe plate and other OSHA required features must be included.
3.4.1.2 Pipe Design
The designer reviews each piping subsystem to select each of the subsystem
components (see P&ID, Figures 3-3.1 and 3-3.2). Exclusive of the chemical
subsystems, there are five piping subsystems which are listed in the Conceptual
Design (see Section 3.2); they are:
1) Raw water influent main
2) Treated water effluent main
3) Wastewater discharge main
4) Treatment unit branch piping
5) Sample panel piping
The designer now proceeds with the detail design of each of those sub-
systems. First, the designer defines the equipment specification for each
equipment component in each subsystem. This is followed by a detailed instal-
lation drawing which locates each component and provides access for operation
and maintenance. As each subsystem nears completion the designer incorporates
provisions for pipe system support and anchorage, as well as for thermal
expansion/contraction.
The interface where the concentrated chemical and treatment unit branch
piping join is designated as a mixing tee. A special detail (see Figure 3-7)
is required to assure that heat of dilution of concentrated corrosive chemicals
imparts no damage to the piping materials. The key factor is to prevent flow
of concentrated chemical when raw water (dilution water) is not flowing. The
dilution water will dissipate the heat. The actual injection must take place
in the center of the raw water pipe through an "injection quill" that extends
from the concentrated chemical pipe. The quill material must be capable of
withstanding the high heat of dilution that develops specifically with sul-
furic acid and to a lesser degree with caustic soda. Type 316 stainless steel
and teflon are satisfactory. It is also very important that the concentrated
33
3-22
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RAW
PVC
>(J
(
t
t
c
t
If
1
1'-0 P-L
*
-_
I
I 2'0 P-L
PVC
L
0*
T'C.S.NPT
1/2"x .049 tw-316 S/S TUBING
50% NaOH «6*Be'H2SO4
POLYPROPYLENE ORIFICE RING SPACER
316 S/S TUBING
PVC - POLYVINYLCHLORIDE PIPE
P-L - POLYPROPYLENE LINED PIPE
FIGURE 3-7 CHEMICAL MIXING TEE DETAIL
34
3-23
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chemical be injected upward from below; otherwise concentrated chemicals with
specific gravity higher than the water will seep by gravity into the raw water
when flow stops. As described later, the chemical pumps are to be de-energized
when the well pump is not running.
The treated water pH must be carefully monitored. A pH sensor installed
in the treated water main indicates the pH at an analyzer mounted at the sample
panel. This analyzer is equipped with adjustable high and low level pH alarms.
The alarms are interlocked with the well pump control (magnetic starter), shut-
ting it down when out of tolerance pH excursions occur. A visual and/or audio
alarm is also initiated to notify the operator regarding the event.
A chemical mixing tee identical to those in the treatment unit branch
piping is employed in the treated water main for the injection of caustic to
raise pH in the treated water. If aeration for removal of CO is used in lieu
of caustic injection for raising treated water pH, then system pressure is
dissipated and the treated water must be repressurized. If the water utility
has ground level storage tanks, the aeration-neutralization concept can be
accomplished without need for a clearwell and repressurization. The aerator
can be installed at an elevation that will permit the neutralized treated water
to flow to storage via gravity.
Easy maintenance is an important feature in all piping systems. Air bleed
valves shall be installed at all high points; drain valves shall be installed
at all low points. This assists the plant operator in both filling and
draining pipe systems. Air/vacuum valve and pressure relief valve discharges
are to be piped to drains. This feature satisfies both operator safety and
housekeeping requirements. Bypass piping for flow control, pressure control,
flow meter and other in-line mechanical accessories is optional. Bypass piping
is costly and requires extra space. However, if continuous treatment plant
operation is mandatory, bypass piping must be included.
3.4.1.3 Instrument Design
Ease of maintenance is very important. Instruments require periodic
calibration and/or replacement. Without removal provisions, the task creates
a mess. Temperature indicators require thermal wells installed permanently in
the pipe. Pressure indicators require gauge cocks to shut off flow in the
branch to the instrument. pH probes require isolation valves and union type
mounting connections (avoids twisting of signal cables). Supply of pH standard
buffers (4.0, 7.0 and 10.0) are to be specified for pH instrument calibration.
A lab bench is to be located near the Sample Panel. Lab equipment to be
specified to include wall cabinet, base cabinet with chemical resistant
counter top and integral sink (with cold water tap), 110V/10/60Hz 20 amp duplex
receptacle, lab equipment/glassware/reagents for analysis of fluoride and
other ion.°.
3.4.1.4 Acid Storage and Feed Subsystem
Operator safety for work within close proximity of highly corrosive chem-
icals takes priority over process functional requirements. Emergency shower
35
3-24
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and eyewash must be located within thirty feet of any work area at which
operator exposure to acid (or caustic soda) exists. Protective clothing must
be specified. Neutralization materials (e.g. sodium carbonate) must be pro-
vided to handle spills. Potential spill areas must be physically contained.
Containment volumes must be sufficient to retain maximum spillage.
To minimize corrosion of acid pipe material, acid flow rate is recommended
to be less than 0.1 ft/sec. Threaded pipe and fittings are not recommended;
tubing and Swagelok fittings are recommended. PVC is also adequate except for
its vulnerability to damage from external loads for which reason it is not
recommended. Positive backflow prevention must be incorporated in each
branch. Day tanks must be vented to atmosphere, have a valved drain, and have
a fill line float valve for fail safe backup control to prevent overflow.
There is one acid feed pump for each treatment vessel. Acid pump power
should be interlocked with the well pump so that the acid pump is de-energized
when well pump is not running. Acid pumps are to have ball checks and pressure
relief which recycles acid back to the day tank. Acid flow rate is to be
manually controlled to provide the required raw water pH. If the feed pumps
are mounted above the day tank, foot valves are required. The designer must
also include anti-siphon provisions in the system.
3.4.1.5 Caustic Soda Storage and Feed System
The safety requirements stated for acid (Section 3.4.1.4) also apply to
caustic soda. Vinegar is satisfactory for - neutralization of minor caustic
spills.
The day tank and pump design features recommended for acid systems also
apply to caustic. The polypropylene day tank should be translucent with gallon
calibrations on the tank wall. The regeneration pump can be calibrated by
means of timing the flow and adjusting as necessary to arrive at the design
flow rate. An optional rotameter can be used, but varying caustic temperatures
will affect accuracy. Carbon steel threaded pipe is recommended for the
service. PVC is not recommended because of its vulnerability to damage from
external loads.
3.4.1.6 Wastewater Lined Evaporation Pond
Pond bottom and top of berm elevations are to be established to provide:
1. Positive drainage away from pond.
2. Anchorage for pond liner on top of berm.
3. Balance of cut and fill. All excavated material is used to form
berm.
4. Top of berm to provide 1 ft-0 in. minimun freeboard above top level
of pond. In high wind locations, the designer must provide
i
36
3-25
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sufficient freeboard to prevent waves from breaking over top of
berm.
The hypalon liner is to be factory assembled for minimum number of field
joints. Placement of liner and sealing of field joints must be performed under
strict supervision of manufacturer's trained representatives. A steel or
concrete splash pad is required to absorb impact of wastewater stream entering
pond. The hypalon liner does not require protective gravel, sand or soil on
its sloped banks; however, in order that the liner be held in place, six inches
of water shall be placed in the pond immediately after placement and testing.
3.4.2 Final Drawings
As stated above, all of the information required for complete installa-
tion of a fluoride removal water treatment plant must appear in the final
construction drawing and specification package.
Isometric drawings for each piping subsystem are recommended; these views
clarify the assembly for the installer. Cross referencing drawings, notes, and
specifications are also recommended.
3.4.3 Final Capital Cost Estimate
Similar to the preparation of the preliminary cost estimate, the designer
prepares the final cost estimate based upon a take off of the installed system.
The estimate is now based upon exact detailed information rather than general
information which was used during the preliminary estimate. The estimate is
presented in the same format (see Table 3-2) and is to be accurate within ten
percent (^10%). Since financial commitments are consummated at this stage,
this degree of accuracy is required.
3.4.4 Final Design Revisions
Upon their completion, the final construction drawings and specifications
are submitted for approval to the owner and the regulatory authorities. If
there are changes or additional requirements requested, the designer must
incorporate them and resubmit for approval. If the designer has communicated
with the approving parties, time consuming resubmittals should not be neces-
sary. Upon receipt of approval, the owner with assistance from the engineer
goes out for bids for the construction of the fluoride removal water treatment
plant.
3.5 REFERENCES
1. Alcoa Product Data, Calculating Pressure Drop through Packed Beds of
Spheres and Mesh Granular Material, January 1, 1971, #GB4A, Aluminum
Company of America, Pittsburgh, Pennsylvania.
37
3-26
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CHAPTER 4
CENTRAL TREATMENT SYSTEM CAPITAL COST
4.1 INTRODUCTION
The designer is obligated to provide his client with the least expensive
central treatment system that can remove the excess fluoride from a sufficient
quantity of potable water that will satisfy all consumption requirements. The
economic feasibility evaluation must include the initial capital cost along
with follow-up operating and maintenance costs. This chapter is devoted to the
capital cost which is affected by many factors including operating costs.
The amount of water to be treated is the most obvious factor by which
capital costs are based; but it is never the only factor, and may not even be
the most significant one. Other factors which can have varying impact upon the
capital cost include, but are not limited to, the following:
1) Raw water quality (temperature, pH, fluoride concentration, alkalinity,
iron, manganese, arsenic, sodium, sulfate, etc.)
2) Climate (temperature, evaporation rate, precipitation, wind, etc.)
3) Seismic zone
4) Soil conditions
5) Existing facility - number of wells (location, relative to each other)
storage, distribution
- water storage (amount, relative elevation, relative
location)
- distribution (relative location, peak flows, total
flow, pressure, etc.)
- consumption (daily, annual)
6) Backwash and regeneration wastewater disposal concept
7) Chemical supply logistics
8) Manual versus automatic control
9) Financial considerations (cost trends, capital financing costs, cash
flow, labor rates, utility rates, chemical costs, etc.)
38
4-1
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Once familiar with the capital cost impact that each of the above vari-
ables can create, the designer quickly realizes that a cost curve (or tabula-
tion) based upon flow rate alone is meaningless. Such a curve is presented
later in this chapter, employing the hypothetical design example used in
Appendix B. A tabulation of the breakdown of these capital costs is provided
in Appendix D. If the cost derived from that curve with the influence
associated with the variables are weighed, the designer can arrive at a
meaningful Preliminary Rough Project Cost Estimate (as described in Section
3.2 - Conceptual Design).
4.2 DISCUSSION OF COST VARIABLES
Each of the variables mentioned above has direct impact upon the total
installed cost for a central treatment system. Ideally, conditions could exist
Which allow the designer to design a minimum cost system. A hypothetical
example would resemble the following:
1) Raw water quality presents no problem (moderate temperature, low
alkalinity, etc.)
2) Warm moderate climate (no freezing, no high temperature, minimal precipi-
tation, no high wind-therefore, no requirement for weather protection)
3) No earthquake requirements
4) Existing concrete pad located on well compacted high bearing capacity
soil
5) Single well pumping to subsurface storage reservoir with capacity for
peak consumption day
6) Existing wastewater disposal capability adjacent to treatment site (e.g.
a large tailings pond at an open pit mine)
7) Acid and caustic stored in large quantities on the site for other purposes
8) Manual operation by labor that is normally at the site with sufficient
spare time
9) Funding, space, etc. available
This ideal situation, though possible, never exists in reality.
Occasionally one, or more, of the ideal conditions occur; but the frequency is
low. If we revise the final estimate for the example used in Appendix B to
incorporate the above ideal conditions, the cost estimate would be reduced from
$347,000. to $132,300 (see Table 4-1). Conversely adverse conditions could
accumulate resulting in a cost in excess of $500,000 for the same treatment
capability. The following subsections provide the designer with the basic
insight needed to minimize the cost impact resulting from the above variables.
39
4-2
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TABLE 4.1. FINAL COST ESTIMATE EXAMPLE FOR IDEAL LOCATION
FLUORIDE REMOVAL WATER TREATMENT PLANT
FINAL CAPITAL COST ESTIMATE
Location:
Flow Rate: 600 gpm
Date :
Process Equipment Cost, $
Treatment Vessels 33,000
Treatment Media 20,500
Process Piping, Valves and Accessories 16,400
Instruments and Controls 8,300
Chemical Storage Tanks , 0
Chemical Pumps, Piping and Accessories 5,300
Subtotal 83,500
Process Equipment Installation
Mechanical 30,000
Electrical 5,000
Painting and Miscellaneous 4,000
Subtotal 39,000
Miscellaneous Installed Items
Wastewater Lined Evaporation Pond 0
Building and Concrete 3,500
Site Work, Fence and Miscellaneous 0
Subtotal 3,500
Contingency 5% 6,300
*Total 132,300
*Engineering, Finance Charges, Real Estate Cost and Taxes not included.
4.2.1 Water Chemistry
The water chemistry can affect capital as well as operating costs. With a
clear picture of the raw water quality, its possible variations and its adverse
characteristics, the designer can readily determine its effect on the capital
cost. High water temperature (greater than 100°F) requires higher cost piping
material and/or pipe support. Varying water temperature requires inclusion of
special provisions for thermal expansion and contraction. Very high fluoride
(greater than 8 mg/1) may ^require larger treatment units to reduce the fre-
quency of regeneration. High alkalinity requires higher acid consumption for
pH adjustment resulting in larger feed pumps, day tank, piping, etc. This
40
4-3
-------
would also probably result in an aeration step for post treatment pH adjustment
in lieu of caustic addition. High arsenic, iron, manganese, and/or suspended
solids can require the addition of pretreatment steps to accomplish removal
prior to fluoride removal.
Each of the physical and chemical characteristics of the raw water must be
evaluated by the designer. The technical as well as the economical feasibility
for the entire project could hinge on these factors.
4.2.2 Climate
Temperature extremes, precipitation and high wind will necessitate a
building to house the treatment system equipment. High temperature along with
direct sunlight adversely affects the strength of plastic piping systems.
Freezing is obviously damaging to piping and in some extreme cases also to
tanks. Temperature variation introduces requirements for special thermal
expansion/contraction provisions. A building with heating and/or cooling and
adequate insulation will eliminate the above problems and their costs; but will
introduce the cost of the building. The building cost will reflect wind loads
as well as thermal requirements. Operator comfort in lieu of economic con-
siderations may dictate building costs.
The evaporation rate will dictate lined evaporation pond disposal of
regeneration wastewater technical feasibility as well as cost.
The installed cost of building and evaporation ponds along with their
associated civil work become a major portion of the overall capital cost. The
designer must exert great care in interpreting the climatological conditions
and their requirements.
4.2.3 Seismic Zone
The designer must adhere to the seismic design requirements of the local
building codes. Buildings and tall slender equipment are vulnerable to seismic
loads. The designer must determine magnitude of seismic design requirements
and adhere to them. In zones of extreme seismic activity low profile equipment
and buildings are recommended.
4.2.4 Soil Conditions
Unless soil boring data is already available for the treatment system
site, the designer is advised to require at least one boring in the location of
the foundation for the heaviest equipment item (either treatment vessel or
sulfuric acid storage tank). If the quality of the soil is questionable (fill,
or very poor load bearing capacity), a soil boring should be obtained for each
major equipment item. Poor soil may require costly excavation/backfill and
foundations.
41
4-4
-------
Combinations of poor soil with rock or large boulders can make foundation
work more complex and costly. Rock and boulders in combination with extreme
temperatures can result in very high installation costs for subsurface raw,
treated and wastewater pipe mains.
4.2.5 Existing Facility
There are many existing facility configurations that can either signif-
icantly increase or decrease the capital cost. The most important factors are
discussed here.
4.2.5.1 Number and Location of Wells
When there is only one well, the removal of excess fluoride must be
accomplished prior to entering the distribution system. Theoretically, treat-
ment can occur before or after entering storage. Practically speaking, treat-
ment prior to entering storage is much easier to control because the treatment
plant flow rate will be constant. If treatment takes place after storage, or
if there is no storage, flow rate is intermittent and variable. Then pH
control is only achievable by sophisticated automatic pH control/acid feed
systems. These are expensive and have difficulty maintaining the required
tight pH treatment tolerance.
When there is more than one well, the designer must decide whether a
single treatment plant treating water from all wells manifolded together or
individual treatment plants at each well present a more efficient and cost
effective concept. Factors such as distance between wells, distribution
arrangement, system pressure, variation in water quality, etc. must be weighed
in that decision. If all of the wells are in close proximity and pump similar
quantity and quality water, a single treatment plant serving the entire system
becomes preferable. When wells are widely dispersed manifolding costs become
prohibitively expensive thus dictating implementation of individual treatment
plants at each well. Frequently the distances may be such that the decision is
not clear cut; the designer then has to relate to other variables such as water
quality, system pressure, distribution configuration, land availability, etc.
Systems that require multiple treatment plant installations can achieve
cost savings by employing an identical system at each location. This results
in an assembly line approach to procurement, manufacture, assembly, installa-
tion and operation. Material cost savings, labor reduction and engineering for
a single configuration will reduce the cost for the individual plant.
4.2.5.2 Storage Facilities
Similar to the wells, the number, size and location of storage tanks can
greatly affect treatment plant size (flow rate) and capital cost. If there is
no storage capacity in the system, the well pump must be capable of delivering
a flow rate equal to the system momentary peak consumption; this could be many
times the average flow rate for a peak day. The designer will quickly conclude
that if there is no existing storage capacity, a storage tank must be added
with the treatment system.
42
4-5
-------
Most systems have existing storage capacity. The storage may be under-
ground reservoirs, ground level storage tanks or elevated storage tanks
(located on high ground or structurally supported standpipes). The first two
require repressurization; the latter does not. The elevated storage tanks
apply a back pressure on the ground level treatment system requiring higher
pressure (more costly) construction of treatment vessels and piping systems.
If aeration of treated effluent for pH adjustment is selected with an elevated
storage tank, the treated water must be contained in a clearwell and repumped
to storage. However, the treatment system vessels and piping may be low
pressure construction. When ground or below ground level storage, loss of
system pressure is not a factor.
The amount of storage capacity is also a factor affecting treatment system
cost. The larger the storage capacity (within limits) the lower the required
treatment plant flow rate (and resulting cost). A minimum storage capacity of
one half of system peak day consumption is recommended.
4.2.5.3 Distribution and Consumption
These are the factors that determine the sizing of the treatment system
(including the well pump flow rate, the storage capacity, etc.). Those fea-
tures must be coordinated to provide a capacity to deliver a peak treated water
supply to satisfy all possible conditions of peak consumption. If there is
adequate storage capacity, the momentary peaks are dampened out. The peak day
then defines the system capacity. The well pump is then sized to deliver a
minimum of the peak daily requirement. The treatment system in turn is sized
to treat a minimum of what the well pump delivers.
The distribution system may anticipate future growth or increased con-
sumption. The well pump must then either pump a flow equal to or larger than
the maximum anticipated peak daily flows or be able to adjust to future
increased flow rate. The treatment plant in turn must incorporate capacity to
treat the ultimate peak flow rate or include provisions to increase the treat-
ment capacity in the future.
4.2.6 Backwash and Regeneration Disposal Concept
Depending on discharge limits established by the EPA, state and local
regulatory agencies, waste disposal can be the single most costly item in the
capital (and operating) cost projection. Requirements can vary from zero
discharge to discharge in an available existing receiving facility. The zero
discharge can be accomplished by chemical precipitation of either calcium
fluoride or aluminum hydroxide with subsequent dewatering of solids and
adjustment of pH. The wastewater supernatant is then fed back to the head of
the treatment plant. This has been successfully accomplished on a pilot scale.
However, this concept has not been incorporated in a full scale treatment
plant. There a.re many other methods of disposal; however, as mentioned prev-
iously, those are beyond the scope of this manual.
43
4-6
-------
4.2.7 Chemical Supply Logistics
Sulfuric acid (normally 66°B'H2S04) and caustic soda (normally 50 percent
NaOH) are readily available and are usually the least expensive chemicals to
use for pH adjustment. Other chemicals such as hydrochloric acid and caustic
potash are technically acceptable, but almost always more costly, and there-
fore not used. The acid and caustic are much cheaper when purchased in bulk
quantities, usually 50,000 pound tank trucks. In very small plants, the cost
of storage tanks for those volumes is not justified and therefore, higher unit
price, smaller volumes are procured (drums and carboys). In very large treat-
ment plants procurement via 200,000 pound railroad tank cars present a still
cheaper mode. This concept, however, requires a rail siding and rail unloading
facility. Nevertheless, it does present an option of lowering the overall
cost.
A chemical unloading rail terminal presents another intriguing option for
facilities with multiple treatment plants. In this concept smaller site
storage tanks are supplied via "mini tank trucks" relaying chemicals to the
treatment site from the rail terminal. This brings down the size (and cost) of
chemical storage tanks at each site. However, this could increase the truck
traffic of corrosive chemicals through populated areas, a risk which may not be
acceptable.
4.2.8 Manual Versus Automatic Control
Automatic controls are technically feasible. However, the periodic
presence of an operator is always a requirement. The capital cost of automa-
tion (valve operators, control instrumentation, etc.) as well as maintenance
costs are usually a burden which the client will not accept. However, in
locations where operating labor rates are extremely high, the client may prefer
an automatic system.
4.2.9 Financial Considerations
Many financial factors must be considered by the designer and his client.
The client can superimpose financial restrictions (beyond any of the technical
factors mentioned above) upon the designer which result in increased (or
decreased) capital cost. These include, but are not limited to the following:
inflationary trends, interest rates, financing costs, land costs (or avail-
ability), cash flow, labor rates, electric utility rates, chemical costs, etc.
All or part of this group of factors could effect the capital cost of a given
treatment plant. The client may desire higher capital investment with reduced
operating cost because interest rates are low, inflation is anticipated, cash
is available, labor and electric utility rates are high. Or the opposite can
be true. The varying combinations of these factors which could develop are
numerous; each one will affect the ultimate capital cost.
44
4-7
-------
4.3 RELATIVE CAPITAL COST OF FLUORIDE REMOVAL CENTRAL WATER TREATMENT PLANTS
BASED UPON FLOW RATE
The relative capital costs of central treatment plants based upon the
treated water flow rate are presented in Figures 4-1 and 4-2. Both cost curves
are based on the same treatment system design criteria. Tabulations of the
breakdowns of the capital costs for both curves is provided in Appendix D. The
curve in Figure 4-1 is based on the facility criteria employed in the hypo-
thetical design for the 600 gpm treatment fluoride system in Appendix B. The
curve in Figure 4-2 is based on the "bare bones" facility requirements pre-
sented earlier in this chapter for the same treatment system (see Table 4-1).
This information demonstrates the dramatic differences in capital cost that
can occur for the same treatment plant in different circumstances. The costs
related to the curve in Figure 4-1 are representative of average capital costs.
4.4 REFERENCES
1. Rubel and Hager, Inc., Final Report - Pilot Test Program - Removal of
Excess Fluoride from Activated Carbon Effluent at Rocky Mountain Arsenal,
Colorado, April 30, 1980.
45
4-8
-------
4.0
n
§ 3.0
cd
2
±'<
2.0
x
8
o
1.0
0 100 200 400 600 800 1000 1200
FLOW . gpm
1400 1600
1800 2000
FIGURE 4-1 COST OF FLUORIDE REMOVAL AT AN IDEAL LOCATION
-------
-p-
H-• '
o
12.0
11.0
10.0
e.o
7.0
6.0
X
*t 5.0
a>
8 4-°
3.0
2.0
1.0
(0
,
0 100 200 400 600 800 1,000
FLOW, gpm
1,200
1,400
1,600
1,800
2,000
FIGURE 4-2 COST OF FLUORIDE REMOVAL FOR A TYPICAL LOCATION
-------
CHAPTER 5
TREATMENT PLANT OPERATION
5.1 INTRODUCTION
Upon completion and approval of the final design package (plans and speci-
fications), the owner (client) proceeds to advertise for bids for construction
of the treatment plant. The construction contract is normally awarded to the
firm submitting the lowest bid. Occasionally, circumstances arise that
disqualify the low bidder in which case the lowest qualified bidder is awarded
the contract. Upon award of the construction contract, the engineer (designer
or his representative) may be requested to supervise the work of the construc-
tion contractor. This responsibility may be limited to periodic visits to the
site to assure the client that the general intent of the design is being
fulfilled; or it may include exhaustive, day to day inspection and approval of
the work as it is being performed. The engineer is requested to review and
approve all shop drawings and other information submitted by the contractor
and/or subcontractors and material suppliers. All acceptable substitutions
are to be approved in writing by the engineer. Upon completion of the
construction phase of the project, the engineer is normally requested to
perform a final inspection. This entails a formal approval indicating to the
owner that all installed items are in compliance with the requirements of the
design. Any corrective work required at that time is covered by a punch list
and/or warranty. The warranty period (normally one year) commences upon final
acceptance of the project by the owner from the contractor. Final acceptance
usually takes place upon completion of all major punch list items.
Preparation for treatment plant startup, startup and operator training
may or may not be included in the construction contract. Although this area of
contract responsibility is not germane to this manual, the activities and
events that lead up to routine operation are. This chapter discusses those
steps in the sense that the operator is performing them. The operator could be
the contractor, the owner's representative or an independent third party.
System operating supplies, including treatment chemicals, laboratory
supplies and recommended spare parts must be procured, and set in place. The
treatment plant operating and maintenance instructions (O&M Manual) must be
available at the project site. Included in the O&M Manual are the valve number
diagram (see Figure 5-1) which corresponds to brass tags on the valves and a
Talve directory furnished by the contractor, and a valve operation chart (see
Me 5-1).
48
5-1
-------
{XI - Shut-off Valve
SI - Butterfly Valve
fXI - Check Valve
jjq - Pressure Control
Valve
Expansion Joint
Pressure Indicator
rWent
CAUSTIC DAY TANK
Pressure Indicator/
Totalizer
Pressure Relief Valve
Valve Numbers
DrainSS
CAUSTIC STORAGE TANK
Vent
^~
ACID STORAGE TANT
pH SENSOR
Backwash Wastewater
Regeneration Wastewater
LINED EVAPORATION POND
FIGURE 5-1 VALVE NUMBER DIAGRAM
49
5-2
-------
TABLE 5-1. FLUORIDE REMOVAL WATER TREATMENT PLANT VALVE OPERATION CHART
(Refer to Figure 5~1 for Valve Location)
Cn
Valve
Function
Unit No. 1
Treatment
Drain
Backwash
Drain
Upflow Regen.
Upflow Rinse
Drain
Downflow Regen.
Drain
Neutralization
Treatment
Treatment
Shu toff
Treatment
Treatment
Treatment
Treatment
Treatment
Treatment
Treatment
Treatment
Unit No. 1
Operation
Unit No. 2
Treatment
Treatment
Shu toff
Treatment
Treatment
Treatment
Treatment
Treatment
Treatment
Treatment
Treatment
Drain
Backwash
Drain
Up flow Regen.
Upflow Rinse
Drain
Downflow Regen.
Drain
Neutralization
Treatment
11
0
X
0
X
0
0
X
0
X
0
0
0
X.
0
0
0
0
0
0
0
0
12
0
X
X
X
X
X
X
X
X
X
0
0
X
0
0
0
0
0
0
0
0
13
0
X
X
X
X
X
X
0
X
0
0
0
0
0
0
0
0
0
0
0
0
14
X
X
0
X
0
0
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
15
X
X
0
X
0
0
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
16
X
0
X
0
X
X
0
0
0
0
X
X
X
X
X
X
X
X
X
X
X
21
0
0
X
0
0
0
0
0
0
0
0
X
0
X
0
0
X
0
X
0
Q
Unit No. 2
Operation
22
0
0
X
0
0
0
0
0
0
0
0
X
X
X
X
X
X
X
X
X
0
23
0
0
0
0
0
0
0
0
0
0
0
X
X
X
X
X
X
0
X
0
0
24
X
X
X
X
X
X
X
X
X
X
X
X
0
X
0
0
X
X
X
X
X
25
X
X
X
X
X
X
X
X
X
X
X
X
0
X
0
0
X
X
X
X
X
26
X
X
X
X
X
X
X
X
X
X
X
0
X
0
X
X
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Numb e r s
System
Isolation
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
3
X
0
0
0
0
0
0
0
0
0
X
0
0
0
0
0
0
0
0
0
X
4
X
0
0
0
X
X
X
X
X
X
X
0
0
0
X
X
X
X
X
X
X
5
X
X
X
X
0
0
0
0
0
0
X
X
X
X
0
0
0
0
0
0
X
6
p
X
X
X
X
X
X
X
X
X
p
X
X
X
X
X
X
X
X
X
•p
7
X
X
0
X
p
X
X
p
X
p
X
X
0
X
p
p
X
p
X
p
X
Sample
17
P
X
X
X
X
X
X
X
X
0
p
p
X
X
X
X
X
X
X
X
p
18
p
X
X
X
X
X
X
X
X
p
p
p
X
X
X
X
X
X
X
X
p
27
P
P
X
X
X
X
X
X
X
X
p
X
X
X
X
X
X
X
X
0
p
28
P
P
X
X
X
X
X
X
X
X
p
X
X
X
X
X
X
X
X
p
p
31
0
X
X
X
X
X
X
X
X
0
0
0
X
0
0
0
0
0
0
0
0
Chemical
Shutoff
32
0
0
X
0
0
0
0
0
0
0
0
X
X
X
X
X
X
X
X
0
0
41
X
X
X
X
0
X
X
0
X
X
X
X
X
X
X
X
X
X
X
X
X
42
X
X
X
X
X
X
X
X
X
X
X
X
X
X
0
X
X
0
X
X
X
43
0
0
X
0
0
0
0
0
0
0
0
0
X
0
0
0
0
0
0
0
0
Legend: 0 - Valve Open
X - Valve Closed
P - Periodic Sample
-------
The treatment bed material is then placed in th.e treatment vessels and the
plant is ready to start operation.
There are four basic modes of operation: treatment, backwash, regenera-
tion and neutralization. Operating details for each of these modes are covered
in this chapter. It is important to note that each of the above modes uses raw
water during each operation, never treated water.
5.2 INITIAL STARTUP
The operator first thoroughly reviews the O&M Manual, familiarizes him-
self with every component of the plant and resolves any question that he may
have.
The placement of the activated alumina in the treatment vessel which takes
place immediately prior to startup is a critical step in the future system
performance. The dry material is delivered in 100 pound bags (least expen-
sive), 100 pound drums, or 400 pound drums. The volume of the media is
determined on a dry weight basis. The actual density vanies with the degree of
packing of the bed, (45-55 pounds/ft ). Fifty pounds/ft is recommended. The
virgin granular material is "coated" with caustic. There is a small amount of
fines (less that 1 percent) that can become airborne and are irritating to the
personnel who are handling them. Eye, skin, and inhalation protection are
mandatory during vessel loading activity. The vessel should be half filled
with water prior to placing the alumina. As the alumina is carefully distrib-
uted into the vessel from above, the water dissipates the heat generated by the
heat of wetting of the caustic "coating" on the alumina grains. This prevents
cementing of the bed. The water also separates the fines from the granular
materials, protects the underdrain assembly from impact, and initiates strat-
ification of the bed. It is recommended that the bed be placed in two or three
lifts. In treatment systems with two or more treatment beds, alternate placing
of media and backwashing steps can be worked together between the treatment
units. Thereby, media placement can be a continuous operation. The bed is to
be thoroughly backwashed with raw water after each lift. During bed placement,
each backwash step should be a minimum of thirty minutes and could extend to
two hours. The purpose of this stringent effort is to remove all of the fines
from the bed. If the fines remain in the bed, possible problems such as
channeling, excessive pressure drop or even cementing can develop. The extra
backwashing effort during bed placement permits fines at the bottom of the bed
to work their way up and out to waste. Since the lower portions of the bed
which contain the largest particles do not expand during backwash, fines not
backwashed out of the bed at that stage may be permanently locked into the bed.
The initial backwash water should be directed to the lined evaporation pond.
5.3 TREATMENT MODE
Upon completion of backwashing of a virgin bed, the bed should be drained
and the vessel opened. Approximately 1/8-1/4" of fine bed material should be
skimmed from the top of the bed. This is the finest grain material which tends
51
5-4
-------
to blind the bed causing channeling and/or excessive pressure drop. Once that
material is removed, the vessel can be closed and refilled with water.
At this point the plant should be cleaned up. Airborne fines that form a
dust like coating on piping and equipment must be removed. Good housekeeping
should begin now and .be continued on a permanent basis.
The pressure loss checkout mentioned in Section 3.4, Final Design, should
be accomplished at this point, just prior to startup. See Table 5.2 for calcu-
lated pressure drop through the treatment media. If there is a pressure loss
problem, it should be corrected prior to treatment startup.
TABLE 5.2. CALCUALTED DOWNFLOW PRESSURE DROP DATA
Alcoa F-l, 28-48 Mesh Activated Alumina
Modified
Water flow rate Pressure drop in PSI Reynolds
gpm/ft per foot of bed depth number
2.0 0.10 2375
3.0 0.018 3555
4.0 0.028 4735
5.0 0.040 5900
6.0 0.053 7111
7.0 0.068 8291
Prior to start of operation, the pH instrumentation is to be calibrated.
The most critical requirement for efficient low cost operation is the control
of the raw water adjusted pH. The optimum environment for fluoride removal
exists when the treatment pH is in the range of 5.0-6.0. The best results have
occurred when the pH is held rigidly at 5.5.. Because acid feed rates are a
function of raw water alkalinity, they vary from one water to another. As raw
water pH moves above 6.0 or below 5.0 fluoride removal capacity deteriorates at
an increasing rate. However, when the alkalinity of the raw water is extremely
high and/or the cost of acid is very high, it can be more cost effective to
operate in a pH range of 6.0-6.5 to reduce the acid consumption (even though
fluoride removal efficiency is also reduced).
The downflow treatment for the first (virgin) run can now begin. See
Valve Operation Chart (Table 5-1) for valve positions for this function. It is
recommended that one vessel be placed in operation at a time. This allows the
operator to concentrate on initial raw water pH adjustment on one treatment
unit until it is in stable operation; he can then devote full concentration to
the next treatment unit. It is also beneficial to stagger treatment unit
operation so that treated water from each unit is at different stages of its
respective treatment run. That facilitates blending of treated water which
provides the most cost effective operation. Water flow rate can be controlled
52
5-5
-------
accurately through each treatment vessel by manually adjusting the effluent
valve (valve numbers 12 and 22) or the influent valve (valve numbers 11 and
21).
The basic flow schematic for the treatment mode is illustrated in
Figure 5-2.
The initial effluent pH is high with no fluoride removal (similar to the
neutralization mode explained later). After a short period both pH and fluo-
ride in the treated water drop to anticipated levels. At that time the treated
water can be directed to storage and/or distribution. Depending on the
requirements of the state or local regulatory agency, samples may have to be
analyzed at a certified testing laboratory prior to approval of distribution of
treated water.
The fluoride in the treated water drops rapidly to a very low level
(normally less than 0.2 mg/1) and remains stable until breakthrough begins. At
that point, the fluoride level increases gradually until the treatment run is
terminated.
Concurrently, the treated water pH gradually drops to the adjusted raw
water pH level where it remains through the duration of the run. This level is
lower than the normally accepted minimum pH of 6.5; therefore, it must be
raised either by chemical addition, aeration or blending with raw water.
Regardless of the method of adjustment, it must take place and be stabilized at
the desired level prior to delivering the treated water into distribution.
High pH in the treated water is also a concern. Normally the maximum allowable
pH is 8.5; however, there are exceptions where 9.0 is permitted. Most systems
desire pH in the 7.5-8.0 range. When the treated water is approved and the pH
stabilized for distribution, it flows out of the plant past a fail-safe pH
sensor with high and low level alarms. If there is a pH excursion exceeding
the allowable limits, an interlock (incorporating the pH alarms with the well
pump(s) magnetic starter) de-energizes the well pump(s). Simultaneously, the
chemical pumps shut down as their controls are interlocked with the well
pump(s) power circuitry. The fail-safe pH override automatically prevents any
treated water, which is out of tolerance pH, from entering the distribution
system. In the event of such an excursion, the operator manually controls the
well pump(s) to divert the unacceptable water to waste, determine the cause of
the deviation and make corrections prior to placing the treatment system back
on line. Probable causes for treated water pH deviations are: change in water
flow rate, change in acid flow rate, change in caustic flow rate, change in raw
water chemistry.
A treatment run can be extended by blending treated water in which the
fluoride level exceeds the MCL with treated water with a low fluoride level.
This can either be done in the effluent main leaving the treatment plant, in
the storage reservoir or bypassing raw water to blend with treated. During a
treatment run there is a long period when the fluoride content of the treated
water is well below the optimum level (one half of the MCL). As breakthrough
53
5-6
-------
Raw Water
Acid
Treated Water
TREATMENT
UNIT
hrH
TREATMENT AND DOWNFLOW
RINSE
Raw Water
TREATMENT
UNIT
Waste
BACKWASH AND UPFLOW RINSE
Raw Water
TREATMENT
UNIT
.Caustic
Raw Water
TREATMENT
UNIT
Caustic
Waste
DOWNFLOW REGENERATION
Waste
UPFLOW REGENERATION
NOTE: For Clarity Only Relevant
Pipes And Shutoff Valves
Are Shown.
FIGURE 5-2 BASIC OPERATING MODE FLOW SCHEMATICS
54
5-7
-------
occurs, there is a long period of slowly increasing fluoride concentration in
the treated water. Blending in the effluent main entails staggering the
treatment cycles of two or more treatment units. This can be accomplished by
continuing treatment in one unit after its increasing fluoride level has sur-
passed the MCL and blending it with low fluoride effluent from one (or more)
unit that is in the early stage of a treatment cycle. The operator can extend
the run until the fluoride level reaches at least twice the MCL before termi-
nating the run. As the fluoride level gets higher the operator must reduce the
flow rate to maintain the combined high and low fluoride " levels at an accept-
able average. The same processes take place in the storage reservoir using one
(or more) treatment unit(s).
This increases the fluoride loading on the alumina and results in lower
operating cost. The loading can significantly exceed the 2000 grains/ft
mentioned in the design criteria in Chapter 3. Capacities in the 2500-3000
grains/ft are normal. Capacities exceeding 4000 grains/ft have been
achieved in certain waters. It should be noted that the higher the raw water
fluoride level, the greater the adsorption (driving force) capacity. For
example, the alumina capacity for a water with a fluoride level of 3 mg/1 may
only be 2100 grains/ft while the capacity for a similar water with a fluoride
level of 8 mg/1 is 3000 grains/ft . Since there are many other factors that
can affect this capacity, the precise amount is difficult to predict. The
operator must be cognizant of the fact that the more water treated during a
run, the lower the operating cost.
In raw waters where the fluoride level does not exceed two times the MCL,
part of the raw water can bypass treatment and be blended back with the treated
water. Water with higher fluoride levels can also profit from bypassing, but
the economic benefits rapidly diminish.
The operator can reduce chemical consumption by blending high pH with low
pH treated waters. This is accomplished during the period when one treatment
unit has recently been regenerated and treated water pH is still high. A
skilled operator develops many techniques such as this to minimize operating
costs.
High iron content in the raw water can cause problems during a treatment
run. The ion oxidizes, precipitates, and is filtered from solution by the
treatment media. This results in increased pressure drop, channeling, prema-
ture fluoride breakthrough, and shortened treatment runs. Raw water iron
content greater than 1.0 mg/1 is cause for concern. Special backwashing
procedures during treatment runs can be employed to cope with this problem.
Special procedures such as intra-run backwashing are beyond the scope of this
manual.
5.4 BACKWASH MODE
For two reasons it is important that the bed be backwashed with raw water
after each treatment run prior to regeneration. First, any suspended solids
55
5-8
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that have been filtered from the raw water by the treatment bed tend to blind
the bed. Therefore, these particles must be removed from the bed. Second,
even though filtration may have been negligible, the downward flow tends to
pack the bed. An upflow backwash will then expand the bed, and break up any
tendency towards wall effects and channeling. A backwash rate of 8-9 gpm/ft
will expand the bed approximately 50 percent, which is recommended. As men-
tioned in prior sections, this rate varies with extreme water temperatures.
Care must be taken to avoid backwashing granular bed material out of the
treatment unit. Normally backwashing lasts ten minutes.
Refer to Table 5-1, Valve Operation Chart, for valve positions for the
backwash mode. The basic flow schematic for the backwash mode is illustrated
in Figure 5-2. For most effective backwash, it is recommended that the vessel
be drained prior to backwash. As backwash water flows into a drained bed, it
lifts the entire bed approximately one foot prior to the bed fluidizing. This
a.ction provides an efficient scouring action without excessive abrasion to the
alumina grains. Backwash water samples must be inspected frequently to deter-
mine that filtered material is still being removed and treatment media is not
being washed out of the bed. Excessive backwash causes abrasion that wears
down the alumina grains. That also wastes raw water and increases the waste-
water disposal volume. Therefore, backwash volume must be minimized. It is
prudent to periodically inspect the media level of each treatment bed.
5.5 REGENERATION MODE
The most efficient cost effective method of regenerating a treatment bed
upon completion of a treatment run includes two discrete regeneration steps.
The first step is upflow following draining of the bed after the backwash mode.
The regeneration is followed by an upflow rinse. The unit is then drained to
the top of the treatment bed prior to the second regeneration step (which is
downflow). Both steps use a 1 percent (by weight) NaOH solution.
The objective of regeneration is to remove all fluoride ions from the bed
before any part of the bed is returned to the treatment mode. Fluoride ions
lose their attraction (adsorption force) and become repelled by the alumina
when the pH rises above 10.5. The higher the pH, the faster and more efficient
the regeneration. However, too high a pH not only costs more (because of
higher caustic consumption), but is also increasingly aggressive to the alum-
ina. The above mentioned one percent NaOH solution is the maximum concentra-
tion required for high efficiency regeneration (recovery of total fluoride
capacity). A skilled operator can reduce the concentration of the NaOH to 0.75
percent with the same high efficiency performance. However, below 0.75 per-
cent, efficiency deteriorates rapidly. This lower caustic concentration can
reduce caustic consumption for regeneration up to 25 percent. As described in
Chapter 3, the dilution of the caustic takes place at a mixing tee in the raw
water branch piping at each treatment unit. Both the raw water and the 50
percent NaOH are metered prior to entering the mixing tee. The accuracy of the
metering ranges from +2 percent to +5 percent depending on the quality of the
flow meters. If using a 0.75 percent NaOH concentration, meter readings that
56
5-9
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are low for water and high for caustic result in a lower than planned caustic
concentration and loss of regeneration efficiency.
The rule of thumb for the volume of one percent caustic solution required
per regeneration step is fifteen gallons per cubic foot of treatment media.
The minimum time recommended for the solution to flow through the bed is thirty
minutes. The maximum time is unlimited; but for practical purposes, thirty-
five minutes is recommended. For a 5'-0" deep treatment bed a flow of 2.5
gpm/ft for a period of thirty minutes for each regeneration step is suffic-
ient. This equates to 0.2 gallons 50 percent NaOH per cubic foot of treatment
media for each regeneration step (upflow and downflow).
For the valve positions during each step of the regeneration mode, refer
to Table 5-1. The basic flow schematics for the regeneration modes are
illustrated in Figure 5-2. After backwash, prior to the upflow regeneration
step, the bed must be drained to remove water which dilutes the caustic concen-
tration. Upon completion of draining, the upflow regeneration starts as des-
cribed above. Upon completion of the upflow regeneration, the caustic feed
pump is turned off and the day tank refilled. The raw water continues to flow
for sixty minutes at 2.5 gpm/ft flow rate upward through the bed, flushing out
the fluoride. After this rinse step is completed, the vessel is drained to the
top of the treatment bed, again to remove dilution water. The downflow regen-
eration is followed by draining of the bed prior to the start of the neutrali-
zation mode.
5.6 NEUTRALIZATION MODE
The neutralization mode is critical to the success of the following treat-
ment run. The object of this mode is to return the bed to the treatment mode as
rapidly as possible without dissolving the activated alumina. The pH of the
treatment media after completion of the regeneration is 12+. It must be
adjusted down to 5.5. Therefore, it must pass through pH ranges where ions
that compete for adsorption sites on the alumina will be loaded into the bed.
The minimum pH that can be safely exposed to the granular activated alumina is
2.5. A pH lower than that is too aggressive and is not recommended.
At the start of the downflow neutralization mode the valves are positioned
per Table 5-1, and after fifteen minutes the flow is adjusted to the normal
treatment mode rate. The basic flow schematic for the neutralization mode is
illustrated in Figure 5-2. The acid pump is started; and the pH of the raw
water is adjusted to 2.5. Acid feed rate again varies with the alkalinity of
the raw water. The raw water flow rate may have to be reduced to achieve pH 2.5
at the maximum acid pump feed rate.
As the neutralization mode proceeds, the pH of the treated water gradually
drops below 12. The rate of pH reduction increases at an increasing rate. As
the treated water pH drops below 10, the treated water fluoride level begins to
drop below that of the raw water. At that time, treatment begins. At the point
where the fluoride level drops below the MCL, the water becomes usable and can
57
5-10
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be directed to storage. The pH may still be high (9.5) in the water; however,
this can be blended with treated water with lower pH from other treatment
units. When the treated water pH drops to 8.5, the raw water pH is adjusted up
to 4.0 as the bed rapidly neutralizes. When the treated water pH drops to 6.5,
the raw water pH is adjusted up to 5.5 where it remains through the duration of
the run. The operation is now starting the next cycle in the treatment mode.
The volume of wastewater produced during the regeneration of a treatment
bed will vary with the physical/chemical characteristics of the raw water. A
rule of thumb that can assist the operator in his logistical handling is "300
gallons of wastewater is produced per cubic foot of treatment media during each
regeneration". Typical volumes of wastewater generated during each regenera-
tion step for a hypothetical treatment bed are as follows:
Backwash - 60 gallons
Upflow Regeneration - 15 gallons
Upflow Rinse - 30 gallons
Downflow Regeneration - 15 gallons
Neutralization - 180 gallons
Total 300 gallons
Operational experience at a specific treatment plant will present devia-
tions from these quantities.
5.7 OPERATOR REQUIREMENTS
A qualified operator for a fluoride removal water treatment plant must
have thorough fluoride removal process training, preferably at an existing
treatment plant. The operator must be able to service pumps, piping systems,
instrumentation, and electrical accessories. The operator must be totally
informed about the characteristics of both acids and caustics in all concentra-
tions. Corrosive chemical safety requirements as to clothing, equipment,
antidotes, and procedures must be thoroughly understood. The operator must be
thoroughly trained to run routine water analyses including at least two methods
for determining fluoride levels. The operator must be well grounded in mathe-
matics for operation cost accounting and treatment run record keeping. The
operator, above all, must be dependable and conscientious.
5.8 LABORATORY REQUIREMENTS
In addition to the Operations and Maintenance (O&M) Manual, the treatment
plant should have the latest edition of Standard Methods for the Examination of
Water and Wastewater prepared jointly by the APHA-AWWA-WPCF (American Public
Health Association - American Water Waste Association - Water Pollution
Central Federation). This supplies the plant operator with all necessary
information for acceptable methods for analyzing water. A recommended list of
items for analysis is illustrated in Figure 3-1. The primary requirement is
for accurate analysis of fluoride and determination of pH. As long as pH
meters are calibrated and cleaned regularly, high precision measurements are
58
5-11
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easily obtained. Care must be exercised to prevent contamination of pH
buffers. Fluoride measurement can be achieved in several ways. Ion-specific
electrodes are accurate and reliable provided that the correct buffer (TISAB)
is employed for the water to be treated. There are two wet chemistry methods
which are also quite accurate. They are SPADNS and Alizarin. Distillation
and/or correction for interfering ions (e.g. alkalinity, aluminum, iron,
sulfate, etc.) are required for accurate results.
5.9 OPERATING RECORDS
A system of records must be maintained on file at the treatment plant
covering plant activity, plant procedures, raw water chemical analyses, plant
expenditures, and inventory of materials (spare parts, tools, etc.). The plant
operator should have the responsibility of managing all aspects of the treat-
ment plant operation. The operator is accountable to the water system manage-
ment. The recommended record system should include, but not be limited to the
following items:
5.9.1 Plant Log
A daily log in which the plant operator records daily activities at the
plant. This record should include a listing of scheduled maintenance, unsched-
uled maintenance, plant visitors, purchases, abnormal weather conditions,
injuries, sampling for state or other regulatory agencies, etc. This record
should also be used as a tool for planning future routine and special
activities.
5.9.2 Operation Log
The operator should maintain a log sheet for each treatment run for each
treatment unit. Thereby, a permanent plant performance record will be on file.
Figure 5-3 illustrates a copy of a suggested form.
5.9.3 Water Analysis Reports
The plant operator should run an analysis of raw and treated fluoride
levels once each day for each unit. He should run a total raw water analysis
once per week. Changes in raw water may necessitate changes in the treatment
process. Figure 3-1 illustrates a copy of a suggested form. A permanent file
of these reports will be a valuable tool.
5.9.4 Plant Operating Cost Records
Using accounting forms supplied by the water system's accountants, the
plant operator should keep a complete record of purchases of all spare parts,
chemicals, laboratory equipment and reagents, tools, services, and other sun-
dry items. This should be supplemented by a file of up-to-date competitive
prices for items that have been previously purchased.
59
5-12
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FIGURE 5-3
FLUORIDE REMOVAL WATER TREATMENT PLANT
Unit # Run #
SERVICE TO RESERVOIR
Meter End
BACKWASH TO SEWER
Meter End
REGENERATION SOLUTION TO
Upf low:
Meter End
Down flow:
Meter End
RINSE TO POND
Meter End
OPERATION LOG
Date Start Date End
Meter Start Total Treated M-Gal.
Meter Start Total M-Gal.
POND
Meter Start Total M-Gal.
Meter Start Total M-Gal.
Meter Start Total M-Gal.
NEUTRALIZATION RINSE TO POND
Meter End
TOTAL WASTE WATER SUMMARY
Total to Pond
Total to Sewer
Total to Waste
Meter Start Total M-Gal.
gal. TOTAL WATER USED Gallons
qal .
!_ PbRCbNI WASIb %
TREATED WATER LOG
Date
Meter
Read! ng
M-Gal
(A)
M-Gal
Total
(oj
-ua I
FR
Raw
Fl uor Ide
FR (mg/ll
FT
Treated
Fl uor i de
FT (mg/1)
(A) FTAvg.
Z(A)FTAvg.*
0
*Average Treated Water Fluoride
60
5-13
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5.9.5 Correspondence Files
The plant operator should retain copies of all correspondence pertaining
to the treatment plant in chronological order. Included would be intra-
departmental notes and memos, in addition to correspondence with other
individuals and/or organizations.
5.9.6 Regulatory Agency Reports
The plant operator should maintain a complete file of copies of all
reports received from state, county, or other regulatory agencies pertaining
to the treatment plant.
5.9.7 Miscellaneous Forms
The operator should have an adequate supply of accident, insurance, and
other miscellaneous forms.
5.10 TREATMENT PLANT MAINTENANCE
The maintenance concept for the fluoride removal water treatment plant is
to isolate the equipment to be serviced by means of shutoff valves, vent and
drain lines (as required), repair or replace equipment, fill lines, open
valves, and start service. To accomplish this, all equipment items are equip-
ped with isolating valves, and all piping systems have vents at high points and
drains at low points.
Equipment manufacturer's recommended spare parts are to be stocked at the
treatment plant to avoid lengthy maintenance shutdowns.
If the entire treatment plant needs to be shutdown, the plant itself can
be bypassed. This can be done by closing the butterfly valves in the raw water
and treated water line and then opening the butterfly valve in the bypass line.
This would result in untreated water with excessively high fluoride being
pumped to distribution, an event that should not occur without the approval of
the water system manager.
In the event the entire treatment plant must be shut down, the local
regulatory agency must be notified immediately.
5.11 EQUIPMENT MAINTENANCE
Equipment manufacturer's maintenance instructions are to be included in
the Suppliers Equipment Instructions Section of the O&M Manual.
5.12 TREATMENT MEDIA MAINTENANCE
Plant operator should inspect the surface of each treatment bed at least
once every three regenerations. If the level of a bed lowers more than eight
61
5-14
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inches, makeup activated alumina must be added. Makeup alumina should be
evenly distributed. There should be a minimum depth of l'-0" of water above
the surface of the existing bed. The vessel should be closed immediately and
backwashed at flow rates varying between 8 and 9 gpm/ft for at least one hour.
It is very important to flush the fines out of the virgin activated alumina as
soon as it is wetted.
It is important that the treatment beds should not remain in the drained
condition for more than an hour. Treatment units not in use must remain
flooded.
5.13 TREATMENT CHEMICALS SUPPLY
The operator should carefully monitor the consumption of liquid chemicals
and reorder when necessary. He must have a method of determining the depth of
liquid in the storage tank (e.g. dip stick) and equating that to the volume of
liquid in the tank. Figure 5-4 illustrates a liquid depth versus volume curve
for a 6,000 gallon horizontal cylindrical tank with dished head.
5.14 HOUSEKEEPING
The plant operator should wash down all equipment at least once per month.
Floors should be swept daily. Bathroom and laboratory fixtures should be
cleaned once per week. All light bulbs should be replaced immediately upon
failure. Emergency shower and eyewash should be tested once per week. Any
chemical spill should be neutralized and cleaned up immediately. Hardware
should be polished once per month and lubricated per manufacturer's direc-
tions. Equipment should be repainted at least once every five years.
62
5-15
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9i-g
£9
LIQUID VOLUME (1,000 GALLONS)
O -» N CO *» Ol 0>
-^:
^
X
X
/
X
y
X
X
X
X
r
X
X
x"
^
^—"
\
Horizontal Cylindrical Vessel
8'-0"£x 11'-6"S/S With Flanged
And Dished Heads
6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96
DEPTH OF LIQUID (INCHES)
FIGURE 5-4 5,000 GALLON CHEMICAL STORAGE TANK-LIQUID VOLUME
-------
CHAPTER 6
CENTRAL TREATMENT PLANT OPERATING COST
6.1 INTRODUCTION
The prime objectives in central treatment plant design are to provide the
client with a low-capital cost installation that works efficiently and
reliably; is simple to operate; and above all, is inexpensive to operate.
Operating costs are normally passed directly onto the water user in the monthly
water bill. These costs include the following:
1. Treatment chemical costs
2. Operating labor costs
3. Utility costs
4. Replacement treatment media costs
5. Replacement parts and miscellaneous materials costs
As the bill is normally based on metered water consumption, the costs for
treatment are prorated on the unit of volume measurement. The units are
usually 1,000 gallons, and occasionally 100 ft (750 gallons). Some systems do
not meter consumption; instead they charge a flat monthly rate based upon size
of branch connection to the water main. Though this latter mode of distribu-
tion saves the cost of meters as well as the reading of meters, it does not
promote water conservation. Therefore, far more water is pumped, treated and
distributed, resulting in a net increase in operating cost. The accounting/
billing methods are handled in many ways; that subject, however, is not
addressed in this manual. The common denominator that applies to both the
operating cost and the bill for water consumption is the unit of volume, 1,000
gallons. Each operating cost factor can be reduced to cost/1,000 gallons.
Each of the above mentioned operating costs is discussed in the following
sections. The sum total of the annual operating costs based upon total water
production yields the cost per 1,000 gallons (the unit cost to be applied to
the consumer's bill).
64
6-1
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6.2 DISCUSSION OF OPERATING COSTS
Similar to capital cost, there are many variables that affect operating
cost. Operator attitude is a key intangible which has an impact on the
ultimate cost. The conscientious operator strives to improve plant perform-
ance and reduce operating cost. In contrast, the disinterested operator is not
concerned with plant performance or cost. The following subsections delve into
each of the operating costs previously listed.
6.2.1 Treatment Chemical Costs
The treatment chemicals discussed herein are limited to sulfuric acid and
caustic soda. There are other acids and bases than can be substituted for
those chemicals; but they are more costly which defeats a prime objective of
this process. Other chemicals could also be used for special requirements such
as: corrosion inhibition, precipitation of regeneration wastewater solids,
dewatering of precipitated solids in wastewater, etc.; however, these are site
specific requirements that are not covered in this manual.
Since these chemicals are being used in treatment of water for public
consumption, it is recommended that samples of each chemical delivery be
analyzed for chemical content. It is also recommended that the chemical
supplier be required to certify that the containers used to store and deliver
the chemicals have not been used for any other chemical; or if they have, that
they have been decontaminated according to procedures required by the govern-
ing regulatory agency.
Chemical costs are variable. Like all commodities, they are sensitive to
the supply and demand fluctuations of the marketplace. The geographic location
of the treatment plant site in relation to that of the supplier has a major
impact on the delivered cost. In many cases, the delivery costs are much
greater than the cost of the chemical. The commodity price of each chemical
can vary dramatically from one region of the country to another. The designer
in his conceptual design must evaluate the chemical logistics and determine the
most cost effective mode of procurement.
The chemistry of the raw water to be treated is the most significant
factor affecting treatment chemical consumption and cost. Fluoride and alka-
linity are the key ingredients in the raw water; the higher that each of these
are, the higher the chemical cost.
6.2.1.1 Acid Cost
The most cost effective commercially available chemical available for
lowering pH is concentrated sulfuric acid. The commercial designation is
66°B'H SO,; its concentration is 93.14 percent. The remaining 6.86 percent is
water tplus other constituents). The other chemicals that could be present
must be evaluated. Frequently, these are small quantities of iron and trace
65
6-2
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amounts of heavy metals. For potable water service, there are stringent limits
on the levels of contaminants in the acid which must and rigidly enforced.
The acid usually is a byproduct of the copper smelting process. Sulfide
in the ore is oxidized to sulfur dioxide which is then converted to sulfuric
acid. Some sulfuric acid supplies are only suitable for commercial applica-
tions; not potable water treatment. These are designated as "dirty acid".
Reputable suppliers screen the chemicals when they are advised of the service
requirements. Therefore, when placing an order for acid, "Potable Water
Service" must be designated. The most economical method of procuring acid is
in tank truck quantities (50,000 pounds) which are 3,200 gallons each. The
tank trucks are loaded at the acid manufacturer's site and delivered directly
to the treatment plant where it is transferred to the acid storage tank.
Transfer is accomplished by means of compressed air which is provided by an air
compressor on the truck. In addition to the lower commodity price resulting
from minimum handling and storage of the chemical, there is minimum chance of
contamination. At large treatment plants where there is potential for high
acid consumption, rail tank car quantity (200,000 pounds) delivery, which is
still cheaper, may be justified. Capital expenditure for a 16,000 gallon
(minimum) storage tank and a rail spur with unloading equipment are then
required.
The delivered cost of tank truck quantities of sulfuric acid presently
ranges from $30-$125/ton depending on the geographic location of the treatment
plant. Rail tank car delivered costs can provide savings ranging up to 40
percent.
The acid is consumed in two phases of the treatment process at every
fluoride removal plant. First, it is used to adjust the raw water pH to the
treatment requirement (5.5); secondly, it is used to rapidly neutralize the
treatment bed immediately after regeneration. At some locations, it is also
used to neutralize the high pH of regeneration wastewater for discharge to
sewers or other receiving facilities. This latter application does not apply
to treatment systems that discharge regeneration wastewater to lined evapora-
tion ponds. The raw water alkalinity dictates the weight of acid required for
the pH adjustment step. The activated alumina fluoride removal process has
been employed on natural waters with alkalinities ranging from 10-1,500 mg/1.
The acid consumption for pH adjustment can be accurately projected by
running a titration on a raw water sample. The cost of acid required for pH
adjustment is then determined by extending the acid addition in mg/1 to the
weight (Ibs.) required per 1,000 gallons and multiplying by the commercial rate
for the acid.
The acid consumption for neutralization after regeneration is a function
of the caustic concentration employed during regeneration and the raw water
alkalinity. Once again, even though small, this quantity does vary consider-
ably from site to site. The consumption is also a function of the raw water
fluoride level which dictates the frequency of regeneration and the volume of
66
6-3
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water over which this cost is dispersed. The higher the fluoride level, the
less gallons treated per regeneration. A rule of thumb to employ when project-
ing chemical costs and volumes is 10,000 gallons of treated water per cycle per
ft of treatment media with 6 mg/1 raw water fluoride (this decreases to 4,000
gallons/ft at 20 mg/1 fluoride and increases to 16,000 gallons/ft at 3 mg/1
fluoride). This rule of thumb information is presented in Figure 6-1. The
weight of acid required for neutralization after regeneration should be in the
range of 1-2 Ibs/ft of treatment media.
The actual acid cost will normally fall in the range of $0.02 to $0.08 per
1,000 gallons of treated water.
6.2.1.1 Caustic Cost
Caustic soda (sodium hydroxide) can be procured in either solid (100
percent NaOH) or liquid (50 percent NaOH or lower). The 50 percent NaOH is the
most practical concentration to obtain for water treatment applications. That
concentration is a byproduct of the chlorine manufacturing process. There-
fore, it requires minimum handling to place it into a 50,000 pound tank truck
(4,000 gallons) or a 200,000 pound rail tank car. At plants where tank car
delivery of caustic is feasible, a 20,000 gallon (minimum) storage tank is
required. The main problem with the 50 percent NaOH concentration is that it
freezes at 55 F; it is also very viscous at temperatures below 70 F. There-
fore, it frequently requires heating. Also, since it is 50 percent water by
weight, the freight is a major cost factor. Solid caustic in bead or flake
form is also readily available in drums or bulk. Its freight cost is roughly
half that of the liquid, but getting it into solution is difficult and dan-
gerous. Regardless of the economics, solid caustic is not recommended for this
application. Caustic in the 20 percent NaOH concentration which is commer-
cially available has a freezing point of -20 F; however, freight costs for
shipping this material are very high (80 percent water). Capital cost for much
larger storage and pumping requirements are also increased. Even though heat-
ing and temperature protection are required, the 50 percent NaOH is recom-
mended. Transferring caustic from tank trucks to storage tanks is accomplished
with compressed air similar to the method for acid.
The delivered cost of tank truck quantities of 50 percent NaOH presently
ranges from $150-$350/ton depending on the geographic location of the treat-
ment plant. Rail tank car delivered costs can provide savings up to 25
percent.
The caustic is consumed in two phases of the treatment process. First, it
is used to raise the pH of the raw water to the level required for treatment
media regeneration; secondly, it is used to raise the pH of the treated water
back to the level desired for distribution. The latter phase may be replaced
by aeration of the treated water to strip the free carbon dioxide. The volume
of 50 percent NaOH required for a 1 percent NaOH concentration regeneration
(includes upfLow and downflow requirements) is 0.4 gallons (5 Ibs.) per ft per
regeneration. As with the acid required for neutralization, the causti con-
sumption is a function of the raw water fluoride level which dictates the
67
6-4
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16
14
J 12
UJ ' ^
Ul
_J
UI
Q
oc 10
O
D
oc
111 fi
t- 8
\
6 8 10 12 14 16 18
THOUSAND GALLONS OF TREATED WATER / cu ft Media
20
FIGURE 6-1 CURVE ILLUSTRATION RULE OF THUMB FOR VOLUME OF WATER TO BE
TREATED PER CYCLE VS. RAW WATER FLUORIDE LEVEL
-------
frequency of regeneration and the volume of water over which this cost is
dispersed. This varies from site to site.
The caustic consumption for treated water pH adjustment is also a function
of raw water alkalinity. The concentration of free CO in the water after the
initial pH adjustment with sulfuric acid will determine the caustic require-
ment. High C0~ concentration (or community objection to addition of sodium to
the water supply) could dictate the aeration method for pH adjustment. In
general, when cost dictates the method, caustic pH adjustment is recommended
when alkalinity is less than 100 mg/1 and aeration is recommended when alkalin-
ity is over 200 mg/1. In the alkalinity range 100-200 mg/1, a general recom-
mendation is difficult; other factors such as storage tank elevation must be
considered. If caustic is used to raise the pH of the treated water, the
quantity will be small. The consumption requirement is again accurately deter-
mined by continuing the original titration required for acid to lower the pH to
the treatment level of 5.5; then adding the 50 percent NaOH required to raise
the pH to the desired level (7.5). The cost of caustic required is then
determined by extending the caustic addition in mg/1 to the weight required per
1,000 gallons and multiplying by the commercial rate for the caustic. The
actual caustic cost will normally fall in the range of $0.02 to $0.12/1,000
gallons.
6.2.2 Operating Labor Costs
This area of operating labor cost is the most difficult to quantify. The
operator is required to be dependable and competent. However, it is not a full
time position, and the educational and experience requirements for this posi-
tion does not dictate a high salaried position. It is impractical to establish
this as a full-time position for a highly skilled operator. Depending on the
size of the system and the other duties available for the operator, his time
should be spread over several accounting categories. Except for days when
regeneration takes place, the treatment plant requires 1-2 hours per day of
operator attention. During regeneration, the operator is required to spend
approximately 6-8 hours over a twelve hour period. On the routine operating
days, he merely checks the system to see that pH is being controlled, takes and
analyzes water samples, checks instrument (flow, temperature, pressure), and
makes entries in daily logs. During the remainder of the time, he is able to
operate and maintain other systems (distribution, pumps, storage, etc.), read
meters or handle other municipal responsibilities (e.g. operate sewage treat-
ment plant). The salary for a qualified individual for such a position will
range from $12,000-$30,000 per year depending upon the size and economic con-
ditions in the community. There should always be a second operator available
to take over in case of an emergency, that is an individual well versed in the
operation of the plant.
Using the example treatment plant presented in the design section, the
cost of operational labor will be as follows: (it is assumed that the hours
not used for treatment plant operation will be efficiently used on other
duties).
69
6-6
-------
Given
flow rate = 600 gpm
annual average utilization = 40%
number of regenerations per year = 50
operator annual salary = $18,000
overhead and fringe benefits = 30%
available man hours per year = 2,000/man
Then:
number of hours on regeneration/year 50 x 8 400 hours
number of hours on routine operation/year (365-40) = 472.5 hrs.
Total plant operator time 872.5 hrs.
Operator hourly rate - 18,000/2,000 - $9.00/hr.
30% (overhead and fringe benefits - $2.70/hr
Operator Rate $11.70/hr
Total operator cost 872.5 hours x $11.70/hr. = $10,208
Total gallons water produced = .4(600 gpm) x 1440 min/day x 365 days/year
= 126,144,000 gallons/year
Labor cost/1000 gallons $10,200/126,144 (1000 gallons) = $0.08/1000 gal
If the operator had no other responsibilities and his entire salary were
expended against this treatment plant operation, the operating labor cost
would become $0.18/1,000 gallons. As the reader can readily see, there are
many variables which can be controlled in different ways. Depending on the
motivation of the designer/planner/manager, the operating labor cost can be
minimized or maximized over a very broad range. In the case of a very high
production plant, the reader will see that the operating labor requirement is
not significantly larger than that for a very small treatment plant. Therefore,
depending on relative salaries, the resulting cost per 1,000 gallons can range
from a few cents to a dollar. In proper perspective, the operating labor cost
should always fall in the $0.03 to $0.10/1,000 gallon range.
6.2.3 Utility Cost
The utility cost is normally electric utility. However, there can also be
telephone and natural gas (or oil). Telephone service to the treatment build-
ing is recommended as a safety precaution in case of accident as well as
operator convenience. Cost for that service should be the minimum available
monthly rate. Depending upon the local climate, the cost for heating can vary.
The purpose of the building is to protect the equipment from elements (pri-
marily freezing) not for operator comfort. Normally the treatment units act as
heat sinks maintaining an insulated building at a temperature near that of the
raw water. In cold climates, the building must have an auxiliary heat source
to prevent freezing of pipes in the event that the water is not flowing. If the
70
6-7
-------
client determines that the treatment building is 'to serve additional func-
tions, heating to a comfort temperature could be an additional required cost.
Electric power must be provided for the following functions:
1. chemical pumps
2. pH controls
3. caustic storage tank immersion heater
4. lighting
5. convenience receptacle
6. (optional) aeration unit blower
7. (optional) repressurization pump
8. extra load on well pump for regeneration/backwash wastewater, and loss of
head through the treatment system
Items 1, 2, 4 and 5 are negligible. Item 3 is a function of the climate
and the heat losses through the insulation. The designer must incorporate
provisions to conserve energy for this function. Item 6 is a relatively small
load (1-2 HP blower motor). Item 7 is potentially the biggest electrical load.
This requirement only exists when aeration is used to adjust treated water pH,
and the water must be pumped to an elevated storage tank. This electrical load
can be equal to the original well pump motor load. However, when repressuri-
zation is a requirement, then the original well pump should be modified to
reduce its discharge pressure capability to only that which is required to pump
the raw water through treatment into the clearwell in lieu of the pressure to
pump to the elevated storage tank. Then the net increase of electrical energy
consumption is nearly negated. Item 8 amounts to 3-5 percent of the well pump
electrical energy consumption.
The electrical utility rate also varies considerably from one geographic
location to another. In, March 1983 rates vary from $0.03 to $0.12/KWH. The
electrical utility cost will range from $0.005 to $0.02 per 1,000 gallons under
normal conditions. Under abnormal conditions, it could be 5<:/l,000 gallons or
higher.
6.2.4 Replacement Treatment Media Cost
The consumption of treatment media should be close to zero in a well
operated activated alumina fluoride removal water treatment plant. However,
there are ways" in which the media can be expended.
71
6-8
-------
The most obvious loss of media occurs during backwash. Excessively long
backwash periods will cause the granular particles to wear down and leave the
bed. This is defined as attrition; it can be minimized. An excessive backwash
rate can expand the treatment media out of the vessel resulting in a massive
loss of media. Monitoring the backwash water will prevent that.
During regeneration and neutralization, excessively high and/or low pH
exposure will attack the treatment media. If the pH of the regeneration
solution exceeds 1.5 percent NaOH, the solution becomes increasingly aggres-
sive to the activated alumina. Similarly, if the pH of the neutralization
solution is lower than pH 2.0, a more drastic dissolving of the alumina takes
place. Samples taken during the regeneration cycle should periodically be
analyzed for aluminum.
A final way for the alumina to be lost is through the effluent underdrain
(collection system) within the bed. If alumina grains ever appear in the
treated effluent, the treatment unit should immediately be taken out of service
for inspection (and repair) of the collection system.
Media replacement costs are extremely hard to predict. The only known
instance of significant media replacement has occurred at a treatment plant
where extensive backwash has been required to remove filtered solids from the
media. The plant is also a high production plant requiring frequent extended
backwashing.
A conservative bed replacement estimate is 10 percent per year. In our
previous example where two 300 ft beds are used, the media replacement will
be:
.10(600 ft3) x 50 lb/ft3 = 3,000 Ib/year
Assuming media cost to be $0.70/lb. (see Table 6-1 for current activated
alumina costs), the annual cost will be $2,100.00/year and the cost per 1,000
gallons will be:
$2,100/126,144 (1,000 gallons) = $0.015/1,000 gallons
TABLE 6.1. PRICE FOR ALCOA F-l, 28-48 MESH ACTIVATED ALUMINA
Quantity Price*
2,000-10,000 Ibs. $0.697/lb.
12,000-20,000 Ibs. 0.594/lb.
22,000-38,000 Ibs. 0.548/lb.
40,000 Ibs. and over 0.516/lb.
—. ..-.T: ':: "' ~~ " " ~" \ _ -- - -- - - - .--—-i--.--.-i _ - -:-^ _
* 100 pound bags, 2,000 pounds/pallet, FOB Bauxite, Arkansas
72
6-9
-------
The projected cost for treatment media replacement is $0.005 to $0.03 per
1,000 gallons of treated water.
6.2.5 Replacement Parts and Miscellaneous Material Costs
This is a very small operational cost item. Replacement parts (e.g.,
chemical, pump diaphragms, seals and replacement pump heads) should must be
kept in stock in the treatment plant, to prevent extended plant shut down in
the event a part is required. Also included are consumables such as laboratory
reagents (and glassware), record keeping supplies, etc. An operative
allowance of $0.01/1,000 gallons of treated water is conservative.
6.3 OPERATING COST SUMMARY
The range of fluoride removal water treatment plant operating costs
discussed above are summarized in Tab/le 6.2. As has been pointed out, the
range of costs is very broad.
TABLE 6.2. Operating Cost Tabulation
Operating cost items
Dollars/1000 gallons treated water
min. max. average
$ $
Treatment Chemicals
Operating labor
Utility
- acid
- caustic
Replacement Treatment Media
Replacement Part &
TOTAL
Misc. Material
0.02
0.02
0.03
0.005
0.005
0.05
0.085
0.08
0.12
0.10
0.05
0.03
0.1
0.39
0.05
0.05
0.06
0.01
0.02
0.01
0.20
The designer and treatment plant operator are the keys to continued
improvement in plant performance and reduction in operating costs.
Their close liaison is necessary to achieve and maintain minimum operating
cost performance.
73
6-10
-------
APPENDIX A
SUMMARY OF SUBSYSTEMS INCLUDING COMPONENTS
The items that are designated as "optional" are not mandatory require-
ments. Some of those items may already be included in systems other than
treatment and therefore, would be redundant. Other items, though desirable,
are not mandatory. And, finally as in the case of backwash water and regenera-
tion wastewater disposal, only one of the optional methods would be used.
For Schematic Flow Diagram, see Figure A-l.
1) Raw Water Influent Main (manifold)
a) Flow control (optional)
b) Flow measurement (optional)
c) Temperature indicator (optional)
d) Pressure indicator (optional)
e) Pressure control (optional)
f) Pressure relief (optional)
g) Backflow preventer (optional)
h) Sample piped to sample panel (optional)
i) Isolation valve
2) Treated water effluent main (manifold)
a) Caustic injection for pH adjustment (optional)
b) pH measurement, indicator, alarm and fail-safe control
c) Sample (after pH adjustment) piped to sample panel
d) Pressure indicator (optional)
e) Flow rate indicator (optional)
f) Flow totalization (optional)
g) Aeration subsystem (optional)
i) Air blower (optional)
ii) Clearwell (optional)
h) Booster or repressurization pump (optional)
i) Disinfection injection (optional)
j) Isolation valve
3) Wastewater discharge main (manifold)
a) Backflow preventer
b) Process isolation valves
74
A-l
-------
PVC
c.s.
s.s.
LEGEND
Polyvinyl Chloride
Carbon
Steel
Stainless Steel
Shut-off Valve
Butterfly Valve
Check Valve
Pressure Control Valve
Expansion Joint
Pressure Indicator
Temperature Indicator
Pressure Indicator/Totalizer •.£
rressure rseiier vaive a
-*w-
O
£i (ji)
_jXr t iS^ f
Raw Water
i Sample ^
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m ft
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To UNIT NO. 1 lL I
Waste
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-> Backwash Wastewater
Regeneration Wastewater
\
LINED EVAPORATION POND
FIGURE A-1 SCHEMATIC FLOW DIAGRAM
75
A.-2
-------
c) Acid injection for pH adjustment (optional)
d) Coagulation chemical injection (optional)
c) Sample (after chemical injection) piped to sample panel
4) Treatment Unit Branch Piping
a) Isolation valves (influent and effluent)
b) Process control valves (manual or automatic)
c) Acid injection (lower pH for treatment)
d) Caustic injection (raise pH for regeneration)
e) Pressure indicator (influent and effluent)
f) Flow rate indicator
g) Flow totalization
h) Sample (influent after pH adjustment and effluent) piped to sample
panel
i) Connections to influent, effluent and wastewater discharge manifolds
j) Pressure relief (optional)
k) Air/vacuum valve
5) Treatment Unit
a) Pressure vessel
b) Treatment media
c) Internal distribution and collection piping
d) Operating platform and/or ladder (optional)
6) Sample Panel
a) Manifolds
i) Influent manifold (influent main sample and raw water samples
from each treatment vessel after pH adjustment)
ii) effluent manifold (effluent main sample after pH adjustment,
treated water samples from each treatment vessel and wastewater
manifold sample after pH adjustment and chemical injection)
iii) pH indicator (influent sample manifold and effluent sample
manifold)
iv) sample collection spigots with drain
b) Wet chemistry lab bench with equipment, glassware, reagents, etc.
7) Acid Storage and Feed Subsystem ,
a) Emergency shower and eye wash
b) Acid storage tank (outside treatment building)
i) fill, discharge, drain, vent, and overflow piping
ii) liquid level sensor (optional)
iii) Desiccant air dryer in vent (optional)
iv) weather protection (optional)
v) diked containment area (optional)
c) Acid day tank (inside treatment building)
i) fill pipe float valve
ii) drain valve
iii) curbed containment area (optional)
76
A-3
-------
d) Acid pumps
i) treatment unit pH adjustment (one pump for each unit)
ii) wastewater pH adjustment (optional)
e) Acid piping (interconnecting piping)
i) between storage tank and day tank
ii) between feed pumps and injection points
iii) between feed pump and wastewater main injection point
(optional)
iv) backflow prevention
8) Caustic Storage and Feed Subsystem
a) Emergency shower and eye wash
b) Caustic storage tank (outside treatment building)
i) fill, discharge, drain, vent, and overflow piping
ii) liquid level sensor (optional)
iii) immersion heater with temperature control
iv) weather protection (optional)
v) diked containment area (optional)
c) Caustic day tank (inside treatment building)
i) fill line float valve
ii) drain valve
iii) curbed containment area (optional)
d) Caustic piping (interconnecting piping)
i) between storage tank and day tank
ii) between regeneration feed pump and injection points in treat-
ment and branch piping
iii) between feed pump and treated effluent main injection point
(optional)
iv) backflow prevention
9) Non-toxic Backwash Water Disposal System
a) Surge tank (optional)
b) Lined evaporation pond (optional)
c) Unlined evaporation pond (optional)
d) Sewer (optional)
e) Drainage ditch (optional)
f) Other discharge method (optional)
10) Toxic Regeneration Wastewater Disposal System
a) Surge tank (optional)
b) Lined evaporation pond (optional)
c) Wastewater reclamation system (optional)
d) Other discharge method (optional)
77
A-4
-------
Appendix B
Treatment System Design Example
Given: g (flow rate) = 600 gpm
N (number of treatment vessels) = 2
Raw water fluoride level =5.0 mg/1
Treated water fluoride level =1.0 mg/1
Treatment media fluoride removal capacity = 2,000 grains/ft
Pipe material - Type I schedule 40 PVC,
v pipe velocity = 5'/sec. (max.)
for higher velocities shock preventers are
required to eliminate water hammer
P (Pressure) = 50 psig (max.)
T (Ambient temperature) = 95°F (max.)
Ta (Water temperature) - 85°F (max.)
w
I Vessel and Treatment Bed Design
Solve for: h (Treatment bed depth)
d (Treatment bed diameter)
V (Treatment bed volume)
N.Mw (Total weight of treatment media)
D (Vessel outside diameter)
H (Vessel overall height)
Reference; Figure 3-4
First, q/N = 600 gpm/2 treatment beds = 300 gpm/treatment bed
Then, using one ft treatment media per gpm treatment-flow we require 300
ft treatment media per treatment bed or, V = 300 ft = -rd h/4
Then, try h = 5'-0" ^ „
Then, d = 4V = 4 x 300 ft 1(5 ft) x TT = 240 ft Iir
Then, d = 8'-9", D must employ the next even multiple of 6" or
D = 9'-p" >8'-9"
Then, d = D-(l") = 9'-0" - (1") = 8'-ll" >5'-0" OK
Then, h = 5';rO" and d = 24" (standard dished head)
Then, V = 7rd"h/4 = ^18.92') /rr = (5')/4 = 312 ft-
Then, N.Mw = N.V.Md = 2 x 312 ft x (50 Ib./ft ) = 31,200 Ib
Then, H = 1" + 2 (dR) + (h/2) + (6") = 1" + 2(24") + 60" + 30" = 6" = 12'-1"
78
B-l
-------
II Pipe Sizing
Solve for:
A) Sizes of raw and treated water pipe mains
B) Sizes of treatment unit branch piping
A) Mains; q = 600 gpm
Try 6", v = 6.8'/sec. > 5'/sec., therefore NG
Try 8", v = 3.9'/sec. > 5'/sec., therefore OK
Use 8" schedule 40 PVC
B) Branches
qB = q/2 = 300 gpm
Try 4", v = 7.7'/sec. > 5'/sec., therefore NG
Try 6", v = 3.4'/sec. > 5'/sec., therefore OK
Use 6" schedule 40 PVC
N
Note: During backwash of one treatment bed the flow rate can
increase up to 600 gpm. Backwash rate is not to exceed rate
required for 50 percent treatment bed expansion. This rate is
sensitive to raw water temperature. Lab bench tests determined
that 9.5 gpm/ft backwash flow rate with water at 104 F expanded
the specified bed material 50 percent. Since bed expansion
will increase as water temperature decreases, an 8 gpm/ft
backwash rate for the 95 F water used in this example will
expand the bed material 50 percent.
Ill Acid System Design
A) Storage Tank Size
Storage tank size is based upon logistical requirements which are a
function of treatment plant acid consumption rate and tank truck
deliveries of bulk acid. The tank truck can deliver up to 50,000 Ibs. of
66° B' H SO, . The density of this liquid is 15.5 Ibs/gallon. Therefore,
a delivery contains 3,250 gallons.
In this example the peak treatment flow is 600 gpm, and we shall assume
that the acid consumption is 0.10 gallons/1,000 gallons treated water (an
above average acid requirement). Then the acid consumption is 3.6
gallons/hour, and a tank truck load would supply a minimum of 900 hours of
treatment operation. Acid consumption for raw water pH reduction, which
is a function of total alkalinity and free carbon dioxide, is discussed in
Appendix C.
A 5,000 gallon storage tank provides capacity for lh bulk tank truck loads
of 66 B' H SO, . Therefore, when half a truckload is consumed, there is a
minimum of a 450 hour (18.75 day) acid storage available before the acid
supply is-expended. In practice it would probably be at least two times
that minimum. At any rate, the 5,000 gallon storage capacity will easily
maintain operation while awaiting delivery.
79
B-2
-------
B) Day Tank Size
The storage tank supplies a polypropylene day tank located inside of the
treatment building. A 100 gallon day tank will satisfy acid requirements
for 1,000,000 gallons of treated water which exceeds the treatment flow
for one day.
C) Acid Pump Size
The maximum acid feed rate required for the treatment mode feed rate for
each pump is: 300 gpm x 60 min/hr x 0.10 gallons acid/1,000 gallons water
= 1.8 gph
The acid feed rate must be increased during the neutralization mode (see
Section 5.6) to adjust raw watfer pH to 2.5. Positive displacement
diaphragm type metering pumps with materials of construction suitable for
66 B' H^SO, service rated at 5.0 gph and a 10:1 turndown rate are suitable
for acid feed to the mixing tee where dilution takes place in the influent
branch to each vessel.
IV Caustic System Design
A) Storage Tank Size
Given: Raw water fluoride - 5.0 mg/1
Treated water fluoride -1.0 mg/1 „
Treatment media Fluoride capacity - 2,000 grains/ft
Density of 50 percent NaOH-12.6 Ib/gal
Find: Frequency of Regeneration
Amount of fluoride removed = 5.0 - 1.0 = 4.0 mg/1
Converting mg/1 to grains/gal multiply by .058 = (4.0) x (.058) = 0.23
grains/gal
3
Quantity of water treated/treatment run = 2,000 grains/ft x
312 ft /0.23 grains/gal = 2,700,000 gal
During maximum treatment flow continuous operation minimum regenera-
tion frequency would be six days per bed. Using the two bed system in
this example, the maximum regeneration frequency could be as often as
once every three days. The amount of 50 percent caustic soda
required per regeneration is as follows: Weight of regeneration
solution = 2 x (15 gallons 1 percent NaOH/ft bed) x (312 ft bed) x
(8.4 Ib/gal) = 78,600 Ib
Weight of 50 percent NaOH/regeneration = 1,572/lbs = Volume of 50
percent NaOH/regeneration = 1,572 lbs/(12.6 Ibs/gal) = 125 gallons
80
B-3
-------
A tank truck 50 percent NaOH delivery contains 50,000 Ibs or approxi-
mately 4,000 gallons, enough to supply 32 regenerations (neglecting
caustic feed requirements for neutralization of treated water).
For sizing of the caustic storage tank in the example, we are using a
50 percent NaOH feed rate of .02 gallons/1,000 gallons of treated
water. This requires 50 percent NaOH feed rate of 0.72 gph. (or 17
gpd). When adding this maximum caustic feed rate for neutralization
to the maximum required for regeneration (17 gpd + 125/3 days) = 76
gpd, if we employa 5,000 gallon storage tank identical to that used
for acid storage in this example, we find that a 40,000 gallon
delivery allows a 1,000 gallon maximum supply in storage at time of
delivery. The 1,000 gallons will supply the treatment plant for a
minimum of 13 days during periods of maximum caustic consumption,
which is adequate. Therefore, the 5,000 gallon caustic storage tank
can be used.
In cases where the raw water fluoride is higher and/or the treatment
flow rate is higher, the rate of caustic consumption will require
larger storage capacity.
B) Day Tank Size
The tank a polypropylene day tank located inside of the treatment
building. A 100 gallon day tank will satisfy caustic requirements
for one of the two phases of the regeneration. This size day tank
will require refilling during the upflow rinse after the upflow
regeneration. A 150 gallon day tank will satisfy the entire regener-
ation plus the caustic required for neutralization of the treated
water. Therefore, use the 150 gallon day tank.
C) Caustic Pump Sizing
A positive displacement diaphragm caustic feed pump with materials
of construction suitable for 50 percent NaOH service, sized for a
miximum flow of 2.5 gph with a 10:1 turndown ratio, will be satis-
factory for the treated water neutralization caustic feed require-
ment (0.72 gph).
For the neutralization step a 2 gpm metering pump with materials of
construction suitable for 50 percent NaOH service is satisfactory.
Each regeneration step (upflow and then downflow) requires 62.5
gallons of 50 percent NaOH to be fed into the mixing tee where it is
diluted to 1 percent NaOH. Each regeneration step is designed to
last between 30 and 35 minutes.
81
B-4
-------
V Lined Regeneration Wastewater Disposal Evaporation Pond Design
A) Assumptions:
1) Average treatment plant average utilization = 40 percent
2) Annual average net evaporation (less rainfall) rate = 6'- 0"
B) Find; Evaporation pond size
Total annual volume of water treated = 40 percent (600ggpm) = 240 gpm
(240 gpm) (1,440 min/day) (365 days/gear) = 126 x 10 gpy &
Number of regenerations: 126 x 10 gpy treated water/(2.7 x 10
gal/regeneration) = 47 regenerations/year
Experience dictates that 300 gallons of wastewater per cubic foot of
treatment media are produced per regeneration. Therefore, each
regeneration yields 312 ft x 300 gal/ft = 93,600 gallons of
wastewater.
The total wastewater produced per year is: (93,60Q
gallons/regeneration) x .,(47 regenerations year) = 4.4 x 10
gallons/year = 586,000 ft /year.
Using an average annual net evaporation of 6'-0" and deducting I'-O"
for deviation from average we have (6'-0")-(1'-0") = 5'-0" net
minimum evaporation rate per year.
To determine the required pond areas we divide the total annual
wastewater produced by the net evaporation.
Pond Area = 586,000 ft3/5 ft = 117,200 ft-
Pond Depth to be 8' (minimum)
82
B-5
-------
APPENDIX C
DISCUSSION OF ACID CONSUMPTION REQUIREMENTS FOR
pH ADJUSTMENT OF RAW WATER
The practical method described in the text which is used to determine the
acid feed requirement for lowering the raw water pH to 5.5 is acid titration.
However, this can also be accomplished theoretically when a raw water analysis
is available and raw water samples are not. This method requires the pH, the
total alkalinity (M as ppm CaCO.,), and/or the free carbon dioxide CO. as ppm)
from the raw water analysis in addition to the graph illustrated in Figure C-l.
If only two of the three raw water analysis items are available, the third is
determined by the graph. The pH curves illustrated in Figure C-l were
developed from theoretical chemical formulae which integrate the relationship
between pH, alkalinity and free C0_ . This theory is beyond the scope of this
manual. Trial and error usage of these curves rapidly leads the designer to
the acid feed requirement for the desired pH adjustment. The objective is to
determine the amount of alkalinity reduction that is required to lower the pH
the desired amount, and then to convert the alkalinity reduction to acid
addition. The designer must be aware of the fact that the reduction in
alkalinity coincides with the corresponding increase in free carbon dioxide.
The following examples best illustrate this method:
Example 1:
Given: Raw Water pH = 8.0
Raw Water M = 220 ppm as CaCO-
Raw Water CO = 4 ppm
Find: a) M and free CO for pH adjusted to 5.5
b) 66°B' H SO, required feed rate to adjust pH to 5.5
a) Try reducing M by 200 ppm (as CaCO ) to 20 ppm (as CaCO ).
Then, increase in free CO (M multiplied by 0.88), 200 x 0.88 = 176
ppm
Then, total free CO = 176 + 4 = 180 ppm
Then, using graph we find that the pH is 5.4 when:
83
C-l
-------
1000
10 100
TOTAL ALKALINITY AS CaCO3-p.p.m.
1000
FIGURE C-1 GRAPH OF pH AS A FUNCTION OF TOTAL ALKALINITY AND
FREE CARBON DIOXIDE
84
C-2
-------
1) M = 20 ppm (as
2) CO = 180 ppm Therefore, NG
Therefore, too much alkalinity was removed. Try reducing M by 196 ppm
(as CaCO ) to 24 ppm (as CaCO )
Then, increase in free Co2 = 196 x 0.88 = 172.5
Then, total free C02 = 172.5 + 4 = 176.5 ppm
Then, using graph we find that the adjusted raw water pH is 5.5 when:
1) M =24 ppm CaCO
2) C02 = 176.5 ppm Therefore, OK
b) For each 100 ppm (as CaCO,) reduction of total alkalinity, 105 ppm
66 B1 sulfuric acid must be added. Therefore, reduce M by 196 ppm
(as CaCO ) by feeding 1.96 x 105 ppm = 205.8 ppm 66-B' sulfuric acid
to adjust raw water pH to 5.5. If we desire to find what acid feed
rate would be required per thousand gallons of treated water, we find
that:
Feed rate = (205.8 x 10~6ppm) x (1,000 gal x 8.34 lb/gal)/(15.5 Ib/gal) =
0.11 gal H2S04/1,000 gal water
Example 2;
Given: Raw Water M - 100 ppm (as CaCO )
Free CO = 6 ppm
Find: a) Raw Water pH
b) M and free CO. for pH adjusted to 5.5.
c) 66 B1 H SO, required feed rate to adjust pH to 5.5
a) From graph we find raw water pH to be 7.5
b) Try reducing M by 80 ppm (as CaCO,) to 20 ppm (as CaCO )
Then, increase in free CO = 80 x 0.88 = 70.4 ppm
Then, total free CO = 70.4 + 6 = 76.4 ppm
Then, using the graph we find the adjusted pH to be 5.75 when:
1)M =20 ppm (as CaCO,)
85
C-3
-------
2) CO = 76.4 ppm Therefore, NG
Therefore, too little alkalinity was removed, try reducing M by 87
ppm (as CaCO ) to 13 ppm (as CaCO ).
Then, increase in free CO = 76.5 + 6 = 82.5 ppm
Then, using the graph we find the adjusted pH to be 5.55 when:
1)M =13 ppm (as CaC03)
2) C02 = 82.5 ppm Therefore, NG
Therefore, too little alkalinity was removed, try reducing M by 88
ppm (as CaCO.,) to 12 ppm (as CaCO.,)
Then, increase in free CO = 88 x 0.88 = 77.5 ppm
Then, total free CO = 77.5 + 6 = 83.5 ppm
Then, using the graph we find the adjusted raw water pH to be 5.5
wh en:
1) M =12 ppm (as CaCO )
2) CO =83.5 ppm Therefore, OK
c) Therefore, reduce M by 88 ppm (as CaCO ) by feeding 0.88 x 105 = 92.4
ppm 66—B1 sulfuric acid to adjust raw water pH to 5.5
Acid feed rate = (92.4 x 10~6ppm) x (1,000 gal x 8.34 Ib/gal)/(15.5 Ib/gal) =
0.05 gal H2S04/1,000 gal water
86
C-4
-------
APPENDIX D
TABULATIONS OF CAPITAL COST BREAKDOWNS FOR CENTRAL FLUORIDE
REMOVAL WATER TREATMENT PLANTS BASED UPON FLOW RATE
H
z
E-
i
< Q
ll
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Ig
go
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Q Q-
2 gS
a 2 o
§§°,
§ §£
t. w >
* 3t
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gg5
" 3
<= S
iE
gz
M g
sS
K ^
TABULATI
1ASED UPC
P3
O
C
o
CM
O
CO
O
o
o
o
— <
o
o
CM
O
O
o
o
o
CO
o
o
o
o
o
o
co
o
o
CM
o
o
e
a
s
$
5
i
Jj
rt
0>
p
0s. O en ^ CM ^-< sj r— -^ CM O CMlACMO
CM -H ^J LA
O O co CM r-* — oo m o cc fi IA m m un
CM m OiT3C
a>S&, AJ3r-( ft G r-« --I CCOr-'
• -I 'HUWprfCO -H r-tr-fcoro »-* PTO tO
3 4JUfx cp-r-t^ e s-i-'S^
co u i-i a P •!-!•»-( D m « u aj n M 01*0 9
to cccOy-uEgw » ^UCW *j —< ft) O5
ly Q> r-*TO O C03-H
O HHfrf en
CM
C 4J
*u 5 J
CM H
o c o
rj [t] E-J
87
D-l
-------
'05
, O3
TABLE D-2. TABULATION OF ESTIMATED CAPITAL COST* OF MINIMUM FLUORIDE REMOVAL CENTRAL WATER TREATMENT PLANTS
BASED UPON TREATMENT FLOW RATE IN DOLLARS ROUNDED OFF TO THE NEAREST THOUSAND
(Multiply by ?1,000)
Treatment Flow Rate ( gpra)
Process Equipment
Treatment Vessels
Treatment Media
Process Piping, etc.
Instrument and Controls
Chemical Storage Tanks
Chemical Pumps, Piping, etc.
Sub to ta 1
Process Equipment Installation
Mechanical
Electrical
Painting and Miscellaneous
Subtotal
Misc. Installed Items
Wastewater Pond
Building and Concrete
Site Work and Miscellaneous
Subtotal
Contingency 5%
Engineering Fees 10%
TOTAL
100
14
4
10
6
—
5
39
20
2
3
25
_..
2
—
2
4
_7
77
200
16
3
12
6
—
5
47
22
3
3
28
..
2
—
2
4
_8_
89
300
21
11
14
7
—
6
59
25
4
3
32
„
3
—
3
5
9
108
400
25
14
16
7
—
6
68
28
5
3
36
__
3
—
3
5
11
123
500
33
21
16
8
—
6
84
30
5
4
39
..
3
—
3
6
13
145
800
40
27
17
9
—
7
100
35
5
4
"44
„
4
—
4
7
15
168
1000
45
34
18
9
—
7
113
42
5
4
51
„
4
—
4
9
17
194
1200
50
41
20
9
—
8
128
47
6
5
58
_.
5
—
5
10
20
221
1400
bO
48
22
10
—
9
149
55
6
6
67
__
5
—
5
11
23
255
1600
70
54
25
12
—
10
171
58
7
7
72
_
5
—
5
13
26
287
1800
80
60
28
12
—
11
191
63
8
9
80
__
6
—
6
14
29
320
2000
90
66
32
14
12
214
68
9
11
88
„
7
—
7
16
32
357
*March 1983 prices.
-------
APPENDIX E
ENGLISH TO METRIC CONVERSION TABLE
English
Inches (in)
. 2
in
. 3
in
Feet (ft)
ft2
ft3
Gallon (gal)
gal
gal
Grains (gr)
gr/ft3
pounds (Ib)
2
Ib/in (psi)
lb/ft2 (psf)
C/1000 gal
Multiply by
0.0254
0.000645
0.000016
0.03048
0.0929
0.0283
0.2642
0.0038
0.0038
0.0649
2.2919
0.4545
0.00689
4.8922
0.2642
Metric
meter (m)
m2
3
m
m
2
m
m3
liters (1)
3
m
kiloliter (kl)
gam (g)
g/m3
kilograms (kg)
megapascals (MP)
kg/m
C/1000 liters
89
E-l
• US GOVERNMENT PRINTING OFFICE 1984- 759-102/10648
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