United States
Enyironmenta,f,£rotecti°n
Design Manual
Removal of Arsenic from
inking Water by
Exchange
Vi/N
As (III)
As(V)
xxxx
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EPA/600/R-03/080
June 2003
Design Manual:
Removal of Arsenic from
Drinking Water by Ion Exchange
by
Frederick Rubel, Jr.
Rubel Engineering, Inc.
Tucson, Arizona 85712
EPA Contract No. 68-C7-0008
Work Assignment No. 4-32
Awarded to
Battelle Memorial Institute
Columbus, Ohio 43201
Work Assignment Manager
Thomas J. Sorg
Water Supply and Water Resources Division
National Risk Management Research Laboratory
Cincinnati, Ohio 45268
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
/T~y Recycled/Recyclable
Printed with vegetable-based ink on
paper that contains a minimum of
50% post-consumer liber content
processed chlorine free.
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Disclaimer
The information in this document has been funded by the United States Environ-
mental Protection Agency (U.S. EPA) under Work Assignment (WA) No. 4-32 of Con-
tract No. 68-C7-0008 to Battelle. It has been subjected to the Agency's peer and
administrative reviews and has been approved for publication as an EPA document.
Mention of trade names or commercial products does not constitute an endorsement
or recommendation for use.
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with pro-
tecting the Nation's land, air, and water resources. Under a mandate of national envi-
ronmental laws, the Agency strives to formulate and implement actions leading to a
compatible balance between human activities and the ability of natural systems to
support and nurture life. To meet this mandate, EPA's research program is providing
data and technical support for solving environmental problems today and building a
science knowledge base necessary to manage our ecological resources wisely,
understand how pollutants affect our health, and prevent or reduce environmental
risks in the future.
The National Risk Management Research laboratory (NRMRL) is the Agency's
center for investigation of technological and management approaches for preventing
and reducing risks from pollution that threaten human health and the environment.
The focus of the Laboratory's research program is on methods and their cost-
effectiveness for prevention and control of pollution to air, land, water, and sub-
surface resources; protection of water quality in public water systems; remediation of
contaminated sites, sediments and ground water; prevention and control of indoor air
pollution; and restoration of ecosystems. NRMRL collaborates with both public and
private sector partners to foster technologies that reduce the cost of compliance and
to anticipate emerging problems. NRMRL's research provides solutions to environ-
mental problems by: developing and promoting technologies that protect and improve
the environment; advancing scientific and engineering information to support regula-
tory and policy decisions; and providing the technical support and information transfer
to ensure implementation of environmental regulations and strategies at the national,
state, and community levels.
This publication has been produced as part of the Laboratory's strategic long-term
research plan. It is published and made available by EPA's Office of Research and
Development to assist the user community and to link researchers with their clients.
Hugh W. McKinnon, Director
National Risk Management Research Laboratory
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Abstract
This design manual is an in-depth presentation of the steps required to design and
operate a water treatment plant for removing arsenic in the As(V) form from drinking
water using the anion exchange process. Because As(lll) occurs as an uncharged
anion in ground water in the pH range of 6.5 to 8, the process will not remove As(lll)
unless it is first oxidized to As{V). The manual also discusses the capital and oper-
ating costs, including many of the variables that can raise or lower costs for identical
treatment systems.
The anion exchange treatment process is very reliable, simple, and cost-effective.
The treatment process removes arsenic using a strong base anion exchange resin in
either the chloride or hydroxide form, with chloride the preferred form because salt
can be used as the regenerant. The process preferentially removes sulfate over
arsenic; and, therefore, as the sulfate increases in the raw water, the process
becomes less efficient and more costly. Furthermore, because sulfate occurs in
significantly higher concentrations than arsenic, treatment run lengths are dependent
almost entirely on the sulfate concentration of the raw water. The ion exchange
process is a proven efficient and cost-effective treatment method for removing As(V)
from water supplies with low sulfate levels.
The configuration of an anion exchange system for As(V) removal can take several
forms. The method presented in this design manual uses three vertical cylindrical
pressure vessels operating in a downflow mode. Two of the three treatment vessels
are piped in parallel to form the primary arsenic removal stage. The third treatment
vessel is piped in series in the lag position. In the primary stage, raw water flows
through one of the two treatment vessels while the second vessel is held in the
standby position. When the treatment capacity of the first vessel approaches exhaus-
tion, it is removed from service and replaced by the second primary stage vessel.
While out of service, the first vessel is regenerated and placed in the standby
position. The role of the third treatment vessel in the lag position is to ensure that any
arsenic that breaks (peaking) through one of the lead vessels does not enter the
distribution system. Although this design concept results in higher capital costs, it
prevents high arsenic concentrations in the treated water, if operated properly.
IV
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Contents
Foreword iii
Abstract iy
Figures vii
Tables viii
Abbreviations and Acronyms ix
Acknowledgments x
1.0 Introduction 1
1.1 Purpose and Scope 1
1.2 Background 1
1.3 Arsenic in Water Supplies 4
1.4 Arsenic Speciation 4
1.5 Removal of Arsenic 4
2.0 Arsenic Removal by Ion Exchange Treatment 5
2.1 Introduction 5
2.2 Ion Exchange Process 5
2.2.1 Effect of Sulfate on Arsenic Removal 6
2.2.2 Effect of Multiple Contaminants 6
2.2.3 Low Effluent pH in the Early Stages of a Treatment Cycle 7
2.2.4 Spent Brine Reuse 7
2.3 Manual vs. Automatic Operation 7
3.0 Design of Central Treatment System 9
3.1 Assemble Design Input Data and Information 9
3.2 Conceptual Design 11
3.2.1 Manual Operation 12
3.2.2 Automatic Operation 12
3.2.3 Semiautomatic Operation 14
3.3 Preliminary Design 15
3.3.1 Treatment Equipment Preliminary Design 15
3.3.1.1 Treatment Bed and Vessel Design 15
3.3.1.2 Pipe Design 18
3.3.1.3 Instrumentation Design 18
3.3.1.4 Salt (NaCI) Storage and Feed Subsystem 19
3.3.2 Preliminary Treatment Equipment Arrangement 19
3.3.3 Preliminary Cost Estimate 19
3.3.4 Preliminary Design Revisions 20
3.4 Final Design... .20
3.4.1 Treatment Equipment Final Design 22
3.4.1.1 Treatment Bed and Vessel Design 22
3.4.1.2 Pipe Design 23
3.4.1.3 Instrument Design 23
3.4.1.4 Regeneration Wastewater Surge Tank 23
3.4.2 Final Drawings 24
3.4.3 Final Capital Cost Estimate 24
3.4.4 Final Design Revisions 24
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4.0 Central Treatment System Capital Cost 26
4.1 Introduction 26
4.2 Discussion of Cost Variables 26
4.2.1 Water Chemistry 27
4.2.2 Climate 27
4.2.3 Seismic Zone 28
4.2.4 Soil Conditions 28
4.2.5 100-Year Flood Plain 28
4.2.6 Existing and Planned (Future) Potable Water System
. Parameters 28
4.2.6.1 Number and Location of Wells 28
4.2.6.2 Potable Water Storage Facilities 28
4.2.6.3 Distribution and Consumption 29
4.2.7 Backwash and Regeneration Disposal Concept 29
4.2.8 Chemical Supply Logistics 29
4.2.9 Manual vs. Automatic Operation 30
4.2.10 Financial Considerations 30
4.3 Relative Capital Cost of Arsenic Removal 30
5.0 Treatment Plant Operation 35
5.1 Introduction 35
5.2 Plant Preparation 35
5.2.1 Operation Review 35
5.2.2 Resin Loading 35
5.2.3 Initial Startup Preparation 37
5.3 Treatment Mode 38
5.4 Backwash Mode 41
5.5 Regeneration Mode 41
5.6 Rinse (Slow and Fast) Mode 41
5.7 Regeneration Wastewater 42
5.8 Operator Requirements 42
5.9 Laboratory Requirements 42
5.10 Operating Records 43
5.10.1 Plant Log 43
5.10.2 Operation Log 43
5.10.3 Water Analysis Reports 43
5.10.4 Plant Operating Cost Records 43
5.10.5 Correspondence Files 43
5.10.6 Regulatory Agency Reports 43
5.10.7 Miscellaneous Forms 43
5.11 Treatment Plant Maintenance 43
5.12 Equipment Maintenance 45
5.13 Ion Exchange Resin Maintenance 45
5.14 Treatment Chemical Supply 45
5.15 Housekeeping 45
6.0 Central Treatment Plant Operating Cost 46
6.1 Introduction 46
6.2 Discussion of Operating Costs 46
6.2.1 Treatment Chemical Cost 47
6.2.1.1 Salt Cost 47
6.2.1.2 Pre-Treatment Oxidation Chemical Cost 47
6.2.2 Operating Labor Cost 48
6.2.3 Utility Cost 48
6.2.4 Replacement Ion Exchange Resin Cost 49
6.2.5 Replacement Parts and Miscellaneous Material Costs 49
6.3 Operating Cost Summary 49
VI
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7.0 References 51
Appendix A: Summary of Subsystem Including Components 53
Appendix B: Treatment System Design Example 57
Appendix C: Tabulations of Estimated Capital Cost Breakdowns for Arsenic
Removal Water Treatment Plants by Means of the Ion Exchange
Process at Typical and Ideal Locations 61
Appendix D: English to Metric Conversion Table 64
Figures
Figure 1-1. Arsenic Breakthrough Results of Full-Scale Arsenic Removal
Anion Exchange System 2
Figure 1-2. Examples of Arsenic Removal Ion Exchange System Designs 3
Figure 2-1. Treatment Runs (Experimental) to Arsenic Breakthrough with
Varying Sulfate Concentrations in Raw Water 7
Figure 3-1. Water Analysis Report 10
Figure 3-2. Ion Exchange Treatment System Flow Diagram 13
Figure 3-3. Treatment Bed and Vessel Design Calculations 16
Figure 3-4. Treatment System Plan 17
Figure 3-5. Treatment Vessels Piping Isometric 25
Figure 4-1. Capital Cost vs. Flowrate at Typical Locations for Arsenic
Removal Water Treatment Plants by Means of the Ion Exchange
Process 31
Figure 4-2. Capital Cost vs. Flowrate at Ideal Locations for Arsenic Removal
Water Treatment Plants by Means of the Ion Exchange Process 31
Figure 4-3. Code Pressure Vessel Fabricator Quotation for Ion Exchange
Treatment Vessels 32
Figure 4-4. Example of SBA Resin Quotation for Arsenic Removal Drinking
Water Treatment Systems Provided by Prominent Manufacturer 33
Figure 4-5. Process Pipe, Fittings, and .Valves: Itemized Cost Estimate for a
Manually Operated 620-gpm Arsenic Removal Water Treatment
System 34
Figure 5-1. Valve Number Diagram 36
Figure 5-2. Basic Operating Mode Flow Schematics 39
Figure 5-3. Resin Removal Capacity Based on Sulfate Concentration and
Resin Capacity 40
Figure 5-4. Arsenic Removal Water Treatment Plant Operation Log 44
VII
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Tables
Table 3-1. Preliminary Capital Cost Estimate Examples for Two Types of Ion
Exchange Arsenic Removal Water Treatment Plants at a Typical
Location 20
Table 3-2. Final Capital Cost Estimate Examples for Two Types of Ion
Exchange Arsenic Removal Water Treatment Plants at a Typical
Location 21
Table 4-1. Final Capital Cost Estimate Examples for Two Types of Ion
Exchange Arsenic Removal Water Treatment Plants at an Ideal
Location 27
Table 5-1. Valve Operation Chart for Treatment Vessels in Treatment and
Regeneration Operational Modes 37
Table 5-2. Typical Manufacturer's Downflow Pressure Drop Data 38
Table 5-3. Typical Regeneration Process 42
Table 6-1. Operating Cost Tabulation 50
VIM
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Abbreviations and Acronyms
ANSI American National Standards Institute
APHA American Public Health Association
ASME American Society of Mechanical Engineers
AVWVA American Water Works Association
BAT best available technology
BV bed volume(s)
CPVC chlorinated polyvinyl chloride
EBCT empty bed contact time
EPDM ethylene propylene diene monomer
ETV Environmental Technology Verification
FRP fiberglass reinforced polyester
GFAA graphite furnace atomic absorption
GHAA gaseous hydroxide atomic absorption
gpd gallons per day
gpm gallons per minute
ICP-MS inductively coupled plasma-mass spectrometry
MCL maximum contaminant level
N/A not applicable
NPT National Pipe Thread
NSF NSF International
O&M operations and maintenance
OSHA Occupational Safety and Health Administration
PL Public Law
PLC programmable logic controller
psi pounds per square inch
psig pounds per square inch gage
PVC polyvinyl chloride
SBA strong base anion
SDWA Safe Drinking Water Act (of 1974)
STP stabilized temperature platform
TCLP Toxicity Characteristic Leaching Procedure
TDS total dissolved solids
U.S. EPA United States Environmental Protection Agency
WEF Water Environment Federation
IX
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Acknowledgments
This manual was written by Frederick Rubel, Jr., Rubel Engineering, Inc., with input
from Thomas Sorg, United States Environmental Protection Agency (U.S. EPA). The
manual was reviewed by the following people, and their suggestions and comments
were of valuable assistance in preparing the final document:
Dr. Dennis Clifford, University of Houston, Houston, TX
Dr. Abraham Chen, Battelle Memorial Institute, Columbus, OH
Mr. Jeff Kempic, U.S. EPA, Washington, DC
Mr. Rajiv Khera, U.S. EPA, Washington, DC
Dr. Jerry Lowry, Lowry Environmental Engineering, Blue, ME
Mr. Bernie Lucey, State of New Hampshire, Concord, NH
Mr. Michael McMullin, ADI, Fredericton, NB, Canada
Mr. Edward Robakowski, Kinetico, Inc., Newberry, OH
Mr. Thomas Sorg, U.S. EPA, Cincinnati, OH
Ms. Lili Wang, Battelle Memorial Institute, Columbus, OH
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1.0 Introduction
1.1 Purpose and Scope
This manual has been prepared to present up-to-date
information on designing central treatment plants for
removing arsenic from water supplies using the strong
base anion (SBA) exchange process. Although the infor-
mation in this manual is provided to serve small central
water treatment plants ranging in capacity from 30,000
to 1,000,000 gallons per day (gpd), the treatment infor-
mation can be adapted to both larger and smaller sys-
tems. For very small systems having capacities of less
than 30,000 gpd (20 gallons per minute [gpm]), some of
the equipment may be different and less expensive (for
example, fiberglass-reinforced polyester [FRP] tanks and
automatic control valves would probably be used). The
detailed design information presented herein applies
exclusively to ion exchange technology employing SBA
resin in the chloride form for removing arsenic from
water supplies.
When arsenic is present above the maximum contami-
nant level (MCL) in a water supply and is combined with
quantities of other organic and/or inorganic contaminants
that exceed their respective MCLs, this method may not
be the best selection. Such water supplies should be
evaluated on a case-by-case basis to select the appro-
priate treatment method or combination of methods.
1.2 Background
The Safe Drinking Water Act (SDWA) of 1974 mandated
that the United States Environmental Protection Agency
(U.S. EPA) identify and regulate drinking water contami-
nants that may have an adverse human health effect
and that are known or anticipated to. occur in public
water supply systems (Public Law, 1974). In 1975, under
the SDWA, U.S. EPA established a MCL for arsenic at
0.05 mg/L (U.S. EPA, 1975). During the 1980s and early
1990s, U.S. EPA considered, but did not make, changes
to the MCL. In 1996, Congress amended the SDWA,
and these amendments required that the U.S. EPA
develop an arsenic research strategy, publish a proposal
to revise the arsenic MCL by January 2000, and publish
a final rule by January 2001 (Public Law, 1996).
On January 22, 2001, U.S. EPA published a final Arse-
nic Rule in the Federal Register thai revised the MCL for
arsenic to 0.01 mg/L (10 pg/L) (U.S. EPA, 2001). Two
months later, in March 2001, the effective date of the
rule was extended to provide time for the National Acad-
emy of Sciences to review new studies on the health
effects of arsenic and for the National Drinking Water
Advisory Council to review the economic issues associ-
ated with the standard. After considering the reports by
the two review groups, the U.S. EPA finalized the
arsenic MCL at 0.01 mg/L (10 ug/L) in January 2002. In
order to clarify the implementation of the original rule,
U.S. EPA revised the rule text on March 25, 2003 to
express the MCL as 0.010 mg/L (U.S. EPA, 2003). The
final rule requires all community and nontransient, non-
community water systems to comply with the rule by
February 2006.
Ion exchange is one of several treatment processes that
the U.S. EPA has listed as a best available technology
(BAT) for removing arsenic [As(V)] in the final Arsenic
Rule (U.S. EPA, 2001). By placing it on the BAT list,
U.S. EPA determined that the process met the seven
criteria required of BAT, including its ability for high arse-
nic removal, a history of full-scale operation, and its
reasonable cost and service life. However, the process
was recommended as a BAT in the final Arsenic Rule
primarily for sites with a low sulfate contaminant level
(50 mg/L or less) because sulfate is preferred over arse-
nic. In the proposed Arsenic Rule (U.S. EPA, 2000a), the
practical application was listed for sites with sulfate con-
taminant levels below 120 mg/L. The upper bound was
lowered in the final Arsenic Rule because of several
factors, including cost and the ability to dispose of the
brine stream.
The ion exchange process for arsenic removal is similar
to the ion exchange softening process except that the
resin employed is an anion resin rather than a cation
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resin. Arsenic [As(V)] is removed by passing the source
water under pressure through a packed bed resin col-
umn; the resin being an SBA exchange resin in either
the chloride or hydroxide form. The chloride form is pre-
ferred because regeneration is accomplished with salt
rather than caustic that is more costly and more difficult
to handle. The operation consists of two cycles; treat-
ment followed by regeneration (backwash, brine addi-
tion, rinse, and fast rinse). During the treatment cycle,
the arsenic [As{V)] and other competing anions such as
sulfate, nitrate, and bicarbonate are exchanged with the
chloride ions on the resin. When the resin reaches its
removal capacity, it is regenerated using a concentrated
chloride solution (salt brine) that results in the chloride
(because of the high concentration) replacing the arsenic
and other anions on the exhausted resin.
The efficiency of the anion exchange process for arsenic
removal is very dependent on the concentrations of other
competing anions, particularly sulfate, that is more pre-
ferred by the resin than As{V). Clifford (1999) reported
the selectivity sequence for SBA resin as follows:
-4 > SCV2 > HAsCV2 > NCV1
SeCV2 > NOf1 > OP1 > HCCV1 > F'1
Because the anion exchange with the sulfate is preferred
over that with the As(V) and because sulfate occurs in
significantly (mg/L) higher concentrations than As(V)
(ug/L), the removal capacity for arsenic is directly
dependent on the sulfate level of the source water. What
is more important, however, is that the more preferred
sulfate can replace the less preferred anions of arsenic
and nitrate and cause them to be eluted from the resin
column if regeneration is not performed at the appro-
priate time. When sulfate replaces less preferred ions,
the concentration of the arsenic (or nitrate) in the effluent
water can be many times higher than the concentration
of the arsenic in the source water. This phenomenon is
referred to as "chromatographic peaking" or "dumping."
An example of arsenic dumping that occurred with a
small, full-scale arsenic removal ion exchange system is
shown in Figure 1-1. When this ion exchange system was
first put on line, the system was set to be regenerated
Raw Water
Effluent from storage tank
following ion exchange system
Breakthrough
Arsenic "Dumping"
I I \^ \IIT
10 12 14 16 18 20 22 24
Week
Influent water: pH 7.5, alk 90 mg/L (CaCQ,), Fe <0.03 mg/L
Figure 1-1. Arsenic Breakthrough Results of Full-Scale Arsenic Removal Anion Exchange System
(Wang, 2002)
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after four months of treatment based on the estimated
average daily flow and sulfate level of the raw water.
After several years of operation, the average flow
increased, and the system was run past arsenic break-
through because regeneration was established on a time
basis rather than a flow basis. As shown in Figure 1-1,
the arsenic levels of the treated water following a stor-
age tank that was immediately downstream of the ion
exchange system exceeded that in the raw water by
about 100%. The storage tank immediately following the
ion exchange system provided for some blending of the
treated water from the ion exchange system. If the water
samples had been collected immediately following the
ion exchange system, the chromatographic peak would
have been even higher. Shortly after the arsenic peaking
problem was discovered, the treatment run time before
regeneration time was shortened to four weeks.
Because bicarbonate is also removed by SBA resins, a
drop in the pH of the effluent water will generally occur,
particularly during the beginning part of the treatment
cycle. The pH decrease is water quality dependent and,
if significant, it could require post-pH adjustment.
The potential problems of arsenic "dumping" and pH
decrease can be minimized by system design. Very
small, simple design systems of one column provide the
greatest opportunity for these conditions to occur, and
extreme care must be taken in operation to prevent
dumping. Operation of multiple columns in parallel and/
or in series, in combination with storage, can decrease
the risk of arsenic dumping and the potential need for
post-pH adjustment. Examples of system configuration
for the anion exchange process for arsenic removal are
provided in Figure 1-2.
The treatment system presented in this design manual is
shown in Figure 1-2(e)—a three-column system with the
first two columns in parallel followed by the third column
in series. As discussed in the following chapters, this
(a) Simple single-column system with
storage.
(b) Two parallel column system with
storage: both columns operating at same
time; staggered exhaustion cycles of
columns.
(c) Two serial column system with
storage: both columns operating at same
time.
Explanation
(d) Three parallel column system with
storage: all three columns operating at
same time; staggered exhaustion cycles
of columns.
(e) Three-column system with storage:
one lead column and lag column operating
at one time. Second lead column in
standby.
Anion Resin Columns
Storage Tank
ARSENIC REMOVAL.CDR
Figure 1-2. Examples of Arsenic Removal Ion Exchange System Designs
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design is conservative and minimizes the risk of arsenic
dumping. Although the design results in higher capital
cost, if operated properly, it prevents high arsenic levels
in the finished water.
1 .3 Arsenic in Water Supplies
Arsenic occurs in combination with other ions as arsenic
compounds. Unless contaminated by arsenic-bearing
wastes, the concentrations in surface water supplies are
normally less "than the MCL. Ground water has higher
arsenic concentrations than surface water, which may
exceed the MCL due to the exposure to arsenic-bearing
materials. Because of the revision of the arsenic MCL, a
large number of systems that had previously been in
compliance will require treatment for the removal of
arsenic.
1.4 Arsenic Speciation
Arsenic is a common, naturally occurring drinking water
contaminant that originates from arsenic-containing rocks
and soil and is transported to natural waters through
erosion and dissolution. Arsenic occurs in natural waters
in both organic and inorganic forms. However, inorganic
arsenic is predominant in natural waters and is the most
likely form of arsenic to exist at concentrations that
cause regulatory concern.
The valence and species of inorganic arsenic are de-
pendent on oxidation-reduction conditions and the pH of
the water. As a general rule of thumb, arsenite, the
reduced, trivalent form [As(lll)], is found in ground water
(assuming anaerobic conditions) and arsenate, the oxi-
dized, pentavalent form [As(V)], is found in surface water
(assuming aerobic conditions). This rule, however, does
not always hold true for ground water. Some ground
water has only As(lll), some only As(V), and some the
combination of both As(lll) and As(V). Arsenate exists in
four forms in aqueous solution, depending on pH:
, H2AsO4~, HAsO42~, and AsC^3". Similarly, arse-
nite exists in five forms: H^sOa*. HsAsOs, H2AsO3~,
HAs032~, and AsOs3". In the common ground water pH
range of 6 to 9, the predominant As(lll) species is neutral
), whereas the As(V) species are monovalent
"
(H2AsO4~) and divalent (HAsQ
2-\
Until recently (Gallagher et al, 2001), studies on the
preservation of the arsenic species concluded that there
was no effective method for preserving As(lll) and As(V)
in water samples. Because of the lack of a good preser-
vation method, field separation methods developed by
Ficklin (1982), Clifford et al. (1983), and Edwards et al.
(1998) have been used that employ an anion exchange
column as the separation procedure. All the methods are
effective, and their use is recommended to determine
the oxidation state of the arsenic in the source water to
be treated.
1.5 Removal of Arsenic
In water supplies where the arsenic level exceeds the
MCL, steps should be taken to reduce the level to below
the MCL. This design manual addresses removal of
excess arsenic by means of the ion exchange method.
However, other treatment methods exist, such as
adsorptive media, membrane separation, chemical coag-
ulation/filtration, and iron removal. Also, other options,
including alternate sources of supply, may offer lower-
cost solutions. The first choice is to locate an existing
water supply within the service area with known quality
that complies with the arsenic MCL in addition to all
other MCLs (both organic and inorganic). If another
source complies with the arsenic MCL, but exceeds
another MCL (or MCLs), it may still be feasible to blend
the two sources and achieve a water quality that com-
plies with all MCLs. Other features associated with this
option may present liabilities, including, but not limited to
high temperature, or undesirable quantities of nontoxic
contaminants such as turbidity, color, odor, hardness,
iron, manganese, chloride, and/or sodium.
A second option is to pump good quality water to the
service area from another service area. Similar to the
alternate source within the service area, this imported
source can be blended. However, the costs of installing
the delivery system and delivering the water become
increasingly unfavorable as the distance increases, the
elevation rises, and/or physical barriers are encountered.
The reliability, the cost, and the assurance that the
consumers will only use that source are factors to be
considered. Another option (which includes an element
of risk) is to drill a new well (or wells) within the service
area. This approach should be attempted only when
there is sound reason to believe that a sufficient quantity
of acceptable quality water can be located. The cost
(both capital and operating) of a new well should not
exceed the cost of treating the existing source. Other
options such as point-of-use treatment systems are
viable alternatives. However, the treatment reliability of
such systems cannot be assured unless stringent con-
trols govern 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.
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2.0 Arsenic Removal by Ion Exchange Treatment
2.1 Introduction
Several central treatment methods can remove excess
arsenic from drinking water supplies, including chemical
coagulation/filtration, adsorptive media, ion exchange,
iron removal processes, and membrane separation
(Chowdhury et al., 2002; Sorg and Logsdon, 1978; U.S.
EPA, 2001). This manual addresses the ion exchange
method, specifically anion exchange, that has been
demonstrated to effectively remove arsenic from ground
water to below the MCL of 0.01 mg/L (Wang et al.,
2002). This chapter provides an overview of the ion
exchange process, including the advantages and dis-
advantages of the process for arsenic removal.
2.2 Ion Exchange Process
The ion exchange process with regeneration capability is
a proven efficient and cost-effective treatment method
for removing As{V) from water supplies and has been
listed as a BAT by U.S. EPA for source water with low
sulfate levels (<50 mg/L) (U.S. EPA, 2001). This process
does not remove As(lll) unless the As(lll) is preoxidized
to As(V) prior to entry into the ion exchange process.
Moreover, this process preferentially removes sulfate
before As(V); and, therefore, as the sulfate concentration
in the raw water increases, the process becomes less
efficient.
The treatment method presented in this design manual
for the ion exchange method uses three vertical cylindri-
cal pressure vessels containing SBA resin beds operat-
ing in a downflow mode (Figure 1-2[e]). Two of the three
treatment vessels are piped in parallel to form the pri-
mary arsenic removal stage. The third .treatment vessel
is piped in series in the lag position to form the second-
ary treatment stage. In the primary stage, the raw water
flows through one of the two treatment vessels in which
the arsenic is removed while the second vessel is held in
the standby position. As the treatment capacity of the
first vessel approaches exhaustion, it is removed from
service and replaced by the second primary stage ves-
sel. While out of service, the first vessel is regenerated
and placed in the standby position. It remains there until
the arsenic removal capacity of the second vessel
approaches exhaustion, at which time that vessel is
removed from service and replaced by the first vessel.
Care must be exercised to prevent arsenic breakthrough
from occurring. Breakthrough results in discharge of the
arsenic removed during the entire treatment cycle from
the treatment vessel in a surge that is much higher than
the arsenic concentration in the raw water (chromato-
graphic -peaking or dumping), as explained in Section
1.2. To ensure that such an event does not result in
treated water with a high arsenic concentration entering
the distribution system, the second stage treatment ves-
sel is provided. Though this design concept results in
higher capital costs, it reduces the risk of high arsenic
concentrations in the treated water. Use of the second
stage treatment vessel provides insurance against a
potential dumping event that could expose consumers to
high arsenic levels in treated water.
Several papers and reports have been written on the
application of the ion exchange method for removing
arsenic from water (Clifford, 1999; Chowdhury et al.,
2002; U.S. EPA, 2000b). The process consists of pass-
ing As(V)-containing raw water through a bed of
chloride-form SBA resin (designated by RCI), during
which the chloride arsenate ion exchange reaction,
Eq. (1), takes place to yield resin in the arsenate form
(R2HAsO4). When the column capacity for arsenic is
exhausted, the arsenic breaks through into the effluent,
and its concentration rises rapidly and can exceed the
influent arsenic concentration if the treatment run goes
beyond breakthrough. The reaction is easily reversed;
and regeneration, according to Eq. (2), returns the resin
to the chloride form, ready for another treatment cycle:
2 RCI + HAsO42 = R2HAsO4 + 2CP
R2HAsO4 + 2NaCI = 2 RCI + Na2HAsO4
(1)
(2)
-------
The advantages of the ion exchange process for remov-
ing arsenic from water are as follows:
1. The process is simple. The process is considered
economical for removing As(V) from water with
sulfate levels less than 50 mg/L.
2. The process can be operated manually or
automatically.
3. The process is capable of lowering As(V) to a level
that meets regulatory requirements.
4. The process is effective in the pH range of 6.5 to 9.0
in which As(V) is present. Feedwater pH adjustment
is, therefore, not required.
5. The exchange kinetics are very fast, resulting in
empty bed contact times as low as 1.5 to 3.0 min.
6. The process can remove other contaminants
including, but not limited to, nitrate, nitrite, uranium,
chromate, and selenium.
7. Exhausted resin can be regenerated using NaCI
brine.
8. Spent regenerant may be reusable.
The disadvantages of the ion exchange process are as
follows:
1. The process does not remove As(lll). When present,
As(lll) must be oxidized to As(V). Excess oxidizing
chemical might degrade the resin; therefore, its
removal may be required prior to contact with the
resin.
2. Sulfate is removed preferentially to As(V). The
length of an ion exchange treatment run is, there-
fore, directly dependent on the sulfate concentration.
The higher the sulfate concentration, the shorter the
treatment run.
3. There is a potential for discharge of higher arsenic
concentrations in the treated water. For water sup-
plies also containing nitrate, there is potential for
discharging high concentrations of both nitrate and
arsenic.
4. Chloride ions will increase in the treated water at an
exchange rate of up to two for each sulfate and
arsenic ion removed.
5. Effluent pH may be reduced to an unacceptably low
level due to bicarbonate conversion to carbonate
and CO2 by the resin. If the treated water pH is too
low, post-treatment chemical addition including pH
adjustment and/or corrosion inhibitor addition may
be required.
6. Foulant formation on resin beads rapidly degrades
process performance. Prefiltration upstream of the
ion exchange column may be required for removing
silica, colloidal matter, etc., to prevent resin fouling.
7. The process will remove uranium that could poten-
tially create a waste handling and disposal problem
of the spent brine when the resin is regenerated.
8. Spent brines require disposal. Spent brines
containing more than 5.0 mg/L of arsenic will be
classified as a hazardous waste based on the U.S.
EPA Toxicity Characteristic Leaching Procedure
(TCLP).
2.2.1 Effect of Sulfate on
Arsenic Removal
Because arsenic is a trace species, its concentration
does not greatly accelerate the run length to arsenic
breakthrough. However, because ion exchange with sul-
fate, a common ion, is preferred over arsenate, nitrate,
bicarbonate, and other common anions, its concentration
largely determines the run length to arsenic break-
through (Ghurye et al., 1999). The results of ion
exchange pilot tests for arsenic removal with several
resins and varying sulfate concentrations in the raw
water are shown in Figure 2-1. Higher sulfate concen-
trations lead to shorter arsenic removal runs, and this
can lead to chromatographic peaking of arsenic after
arsenic breakthrough. These peaks are avoided by
stopping a run prior to arsenic breakthrough. Concern for
potential breakthrough of arsenic must be eliminated.
One design that can reduce the risk of arsenic break-
through is the inclusion of a second stage polishing
vessel in series that will remove any arsenic that might
exit the primary stage treatment vessel (Figure 1-2[e]).
2.2.2 Effect of Multiple Contaminants
If nitrate is present along with arsenic and sulfate, the
SBA resin will remove the nitrate along with the arsenic
and sulfate. Because nitrate is less preferred than
arsenic and sulfate, nitrate will break through prior to
both arsenic and sulfate. Although nitrate is less pre-
ferred than arsenic, arsenic levels occur in significantly
tower concentrations (ug/L) than nitrate (mg/L). There-
fore, arsenic will not have a major effect on nitrate dump-
ing if the system is run beyond nitrate breakthough.
However, substantial nitrate dumping, similar to arsenic
dumping, can occur in the effluent if the treatment cycle
-------
« 1,000
w
•S
£
"5
|
"o
•o
«
ED
800
600
400
200
50 100 150
Sulfate Concentration - mg/L
200
250
-Resin A
• Resin B
•ResinC
Figure 2-1. Treatment Runs (Experimental) to Arsenic Breakthrough with Varying Sulfate
Concentrations in Raw Water (Ghuryeetal., 1999)
is allowed to run past sulfate breakthrough. To prevent
the possibility of nitrate dumping, the treatment run
should be terminated prior to nitrate breakthrough. This
results in shorter run lengths, but will avoid exceeding
the nitrate MCL. Concern for potential breakthrough of
nitrate and arsenic should be eliminated. This risk can
be reduced by including the above-mentioned second
stage treatment vessel in series, which will remove any
nitrate and arsenic that might exit the primary stage
treatment vessel.
2.2.3 Low Effluent pH in the
Early Stages of a
Treatment Cycle
When a chloride-form SBA resin is used to treat natural
water as in the arsenic ion exchange process, the efflu-
ent pH during the first 50 to 300 bed volumes can be.
significantly reduced compared with the influent pH.
Effluent pH as low as 5.0 has been observed (Clifford,
1999). The reason for the pH reduction is the conversion
of bicarbonate to carbonate by the resin (Horng and
Clifford, 1997). This conversion occurs with the resulting
expulsion of a proton (H* ion), which increases the H+
ion concentration and lowers the pH. The bicarbonate-
to-carbonate reaction occurs because all standard SBA
resins prefer divalent (e.g., carbonate) to monovalent
(e.g., bicarbonate) ions at the typical total dissolved sol-
ids (TDS) levels found in drinking water supplies.
The extent of the pH lowering depends primarily on the
characteristics of the resin and the bicarbonate concen-
tration in the raw water. If the treated water pH is low or
possesses corrosive characteristics, corrective measures,
including pH adjustment and/or addition of a corrosion
inhibitor, might be required. Post-treatment chemical
feed may be required for such adjustments.
2.2.4 Spent Brine Reuse
Direct reuse of the spent arsenic-contaminated ion
exchange brine is possible to regenerate the spent resin
(Clifford and Ghurye, 1998). Brine reuse can substan-
tially cut down on (a) the volume of brine discharged,
and (b) the amount of salt (NaCI) consumed by the pro-
cess. This option, which can be incorporated into the
process in various ways, has not been tried in full-scale
systems and, therefore, is not included in the scope of
this manual.
2.3 Manual vs. Automatic Operation
The water utility owner should be informed of the advan-
tages and disadvantages of the operational options prior
to finalizing the decision relating to the mode of opera-
tion. The system can be operated manually, automati-
cally, or semiautomatically. Automatic operation reduces
operator effort, but increases the cost of instrumentation
and control equipment, as well as the skill level required
of the operator, who should be able to maintain more
sophisticated equipment.
Treatment systems using ion exchange resin are suitable
for manual operation. That operational mode requires the
treatment plant operator to accomplish the following:
-------
1. Start/stop operation. Adjust flowrate.
2. Start/stop and adjust rate of brine feed. Monitor
concentration.
3. Monitor and adjust system operating pressure.
4. Start/stop/control backwash, drain, regeneration,
and rinse steps.
5. Monitor arsenic concentration of raw water, treated
water, and intermediate sample points.
6. Monitor pH of treated water.
A fully automatic instrumentation and control system
includes a programmable logic controller (PLC), an oper-
ator interface (screen with graphics), software, automatic
instrumentation (sensors, transmitters, controllers, alarms,
electrical conductors, pneumatic tubing, etc.) and auto-
matically controlled equipment (valves, pumps, chemical
feed pumps, air compressor, etc.). The instruments can
monitor and control flow, level, pressure, pH, and tem-
perature. Arsenic concentration analyses require a man-
ual laboratory procedure.
Semiautomatic operation entails automating any part of
the instrumentation and control functions, while the
remainder are accomplished manually. Not included are
the PLC, operator interface, and required software. This
operational mode reflects choices made by the owner
with the advice of the designer. The choices require
analysis of risk and treatment process efficiency vs.
investment in equipment and labor. This design manual
presents information regarding instrumentation and con-
trol functions, all of which can be accomplished auto-
matically or manually. The only exception is the labora-
tory analysis requirement for determination of arsenic
concentration in raw water, treated water, wastewater,
and at intermediate sample points.
-------
3.0 Design of Central Treatment System
The design of the ion exchange system presented in this
manual provides information to adapt anion resins in the
chloride form to remove As(V) from drinking water
sources. Because As(lll) cannot be removed by ion
exchange SBA resin, all As(lll) in the source water must
be preoxidized to As(V) to accomplish maximum arsenic
removal.
As{lll) can be easily converted to As(V) by several
commonly used chemical oxidants. A laboratory study
on six chemical oxidants has recently been completed
by Ghurye and Clifford (2001). The results of this study
showed that chlorine, potassium permanganate, and
ozone were very effective oxidants, whereas chlorine
dioxide and monochloramine were not. The actual
amounts necessary to oxidize As(lll) must take into
account other oxidant demand substances in the source
water such as iron, manganese, and sulfide. The study
also showed that a solid oxidizing media used for iron
and manganese removal has the ability to oxidize As(lll).
Air oxidation that is effective for oxidizing iron has been
found to be ineffective for As(lll) oxidation {Lowry and
Lowry, 2002). The selection of the oxidation method
should be based on a number of factors, including the
capital and operation costs, water quality, disinfection
requirements, and impact on resin.
It is very important to thoroughly investigate the indi-
vidual resin that will be applied to the treatment system.
The physical performance characteristics vary among
resins. The variables include, but are not limited to, resin
capacity, backwash requirements, treatment flowrate,
regeneration brine flowrate, brine concentration, brine
volume, etc. The information included in this manual
allows flexibility to adapt to any combination of the above
variables.
A four-step design process is employed in this manual.
The steps are as follows:
1. Assemble design input data and information.
2. Conceptual design.
3. Preliminary design.
4. Final design.
3.1 Assemble Design Input Data
and Information
The design input data and information should be col-
lected prior to initiating the conceptual design. The design
input data and information include, but are not limited to,
the following:
1. Chemical analyses (see Figure 3-1) of representa-
tive raw water samples (includes all historical
analyses). Comprehensive raw water analyses of all
inorganic, organic, radionuclide, and bacteriological
contaminants are also required to verify that the ion
exchange process is the best available method for
the treatment system requirements.
2. Treated water quality compliance standards issued
by the regulatory agency with jurisdiction in the area
where the system resides.
3. Regulatory design standards.
4. Wastewater and waste solids disposal ordinances
issued by the responsible regulatory agency.
5. Data on system production and consumption
requirements (present and future).
6. Manual vs. automatic operation.
7. State and local codes, and Occupational Safety and
Health Administration (OSHA) requirements.
8. Comprehensive climatological and seismic design
data.
The treatment system is a subsystem within the larger
water utility system. Other subsystems include the raw
water feed pump, the storage reservoirs, the pressur-
ization subsystem, and the distribution subsystem. This
design manual is applicable when arsenic removal is the
-------
EXAMPLE
ARSENIC REMOVAL WATER TREATMENT PLANT
REPORT OF WATER ANALYSIS
NAME AND ADDRESS
SOURCE OF WATER
CONTAINER
SAMPLE DATE
TAKEN BY:
Analysis No.
Calcium
Magnesium
Sodium
Total Cations
Total Alkalinity (M)(a)
Phenolphthalein Alkalinity (P)(a)
Total Hardness(fl)
Sulfate
Chloride
Nitrate
Total N on carbonate Solids
Silica - Si02
Free Carbon Dioxide
Iron (Fe) Unfiltered
Iron (Fe) Filtered
Manganese
Turbidity (NTU)
Color (Units)
Fluoride
Arsenic - Total
Soluble Arsenic
P articulate Arsenic
Arsenic (III)
Arsenic (V)
PH
Specific Conductance (micro-mhos)
Temperature (°F)
(a) mg/L as CaCO3.
All units expressed as mg/L except as noted.
Figure 3-1. Water Analysis Report
10
-------
only treatment requirement. However, removal of other
contaminants such as bacteria, suspended solids, hard-
ness, organic and/or inorganic contaminants, may also
be required. In those cases, alternative treatment pro-
cesses and/or additional treatment processes should be
evaluated.
The sequence of additional treatment steps should be
compatible with the ion exchange arsenic removal meth-
od. Removal of suspended solids, organics, and other
contaminants that might foul the resin should take place
upstream of the ion exchange arsenic removal process.
Preoxidation of As(lll) takes place upstream of the ion
exchange process. If a preoxidizing chemical is required,
the resin manufacturer should be contacted to determine
if the chemical has detrimental effects on the resin or the
acceptable exposure concentration and the possible
need to take steps to prevent the chemical from coming
in contact with the resin. Other treatment processes may
be required upstream or downstream of the arsenic
removal process, but that decision shall be made on a
case-by-case basis.
For ground water systems, 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 fiowrate than the maximum
daily fiowrate requirement), it should be resized to
deliver slightly more (i.e., 125% minimum) than the peak
requirement. The fiowrate dictates the treatment equip-
ment size and capital cost. The design rate should be
minimized to the extent possible to ensure that the cap-
ital cost of the treatment system is minimized. Reducing
fiowrate for an oversized pump can result in excessive
equipment wear and energy costs. The treatment media
volume is a function of fiowrate. The treatment vessels,
pipe sizes, and chemical feedrates aif increase as the
fiowrate increases. A well-matched pump can handle
any additional head loss associated with the treatment
system without a significant drop in pump efficiency. If
the additional head loss cannot be met with the existing
pump, several options exist: increasing the size of the
motor, increasing the size of the impeller, or replacing
the pump. Storage should be provided to contain a
minimum of one half the maximum daily consumption
requirement. This is based on the premise that maxi-
mum consumption takes place during 12 hours of the
day. Then, if the treatment system operates during the
entire 24 hours, storage drawdown occurs during
12 hours and recovers during the remaining 12 hours.
Construction materials must comply with OSHA stand-
ards, local building codes, health department and pos-
sibly other requirements in addition to being suitable for
the applicable pH range and compatible with any pre-
treatment oxidizing chemicals used (e.g., chlorine,
ozone). Both drinking water treatment chemicals and
system components should comply with NSF Inter-
national/American National Standards Institute (NSF/
ANSI)STD61.
Treatment system equipment should be protected from
climatic conditions. Although not mandatory, in some
locations, it is prudent to house the system within a
building.
Wastewater resulting from backwash and regeneration
of the resin can only be disposed of in a manner per-
mitted by state and/or local regulatory ordinances (SAIC,
2001). There are several options for disposal; however,
they are subject to climate, space, and other environ-
mental limitations. Because each of the variables can
significantly affect both capital and operating costs, the
available wastewater handling options should be evalu-
ated carefully prior to making conceptual selections.
Waste disposal plays an important role in treatment pro-
cess selection. Waste disposal regulatory requirements
and disposal options (MacPhee et al., 2000) may be an
important factor in selecting an anion exchange treat-
ment process because the brine wastewater probably
will be classified as a hazardous waste.
3.2 Conceptual Design
The second step in the design process is the Conceptual
Design, which provides a definition of the process. How-
ever, this step does not provide equipment size,
arrangement, material selection, details, or specifica-
tions.
There are four basic options from which a Conceptual
Design can be selected. Every combination of options
may not be able to perform the process. Therefore, the
options should be screened to determine which combi-
nations are applicable. The options are as follows:
1. Gravity or pressure flow.
2. Upflow or downflow treatment flow direction.
3. Single or multiple treatment vessel(s).
4. Series or parallel treatment vessel arrangement.
A gravity flow system is not compatible with the ion
exchange process, Downflow treatment consistently
yields higher treatment efficiency than upflow. Because
the downflow concept uses a packed bed, flow distribu-
tion is superior. If the upflow beds are restrained from
expanding, they would in effect also be packed. How-
ever, they would forfeit the necessary capability to
backwash.
11
-------
Examples of several designs of treatment vessel
arrangements are shown in Figure 1-2. Each design has
its advantages and disadvantages when considering the
potential of arsenic dumping, decreases in the pH of the
effluent water, and the problems associated with each
situation.
The design concept presented in this manual provides
sound, risk-reduction features for a pressure system
using a primary stage, downflow treatment vessel, fol-
lowed in series by a second stage downflow treatment
vessel (Figure 1-2[e]). For maximum risk reduction, two
treatment vessels in series are recommended. The
simple single-treatment unit configuration introduces a
greater risk of release of a high (peak) arsenic concen-
tration in the treated water (Figure 1-2[a]).
The primary stage (of the two vessels in series design)
consisting of two parallel treatment vessels provides an
operating treatment vessel and a standby treatment
vessel. As the operating treatment vessel approaches
exhaustion of ion exchange capacity, it is removed from
service and replaced by the standby treatment vessel.
Ion exchange capacity exhaustion is discussed in Chap-
ter 5.0. The backwash/regeneration/rinse then takes
place at a time scheduled by the plant operator prior to
exhaustion of the other primary stage treatment vessel.
To reduce the risk of arsenic breakthrough entering the
distribution system, the second stage treatment vessel is
permanently piped in series in the lag position with the
two primary stage treatment vessels permanently in the
lead position.
For economy of treatment, an optional raw water bypass
and reblending capability can be included. For systems
in which the raw water arsenic concentration is slightly
above the arsenic MCL, bypassing and reblending a
fraction of the raw water with the remaining fraction that
is treated should be evaluated. This option saves treat-
ment chemicals, extends treatment media cycle life, and
reduces operating cost. If bypassing and blending is
feasible, the; treatment system can be sized to treat less
than 100% of the total flow.
Once the bed configuration is defined, a basic schematic
flow diagram is prepared (see Figure 3-2). This diagram
presents all of the subsystems.
Prior to proceeding with the Preliminary Design, financial
feasibility should be determined. Funding limits for the
project should be defined. A determination that funding
is available to proceed with the project should be made.
This requires a preliminary rough project estimate with
an accuracy of £30%. If the preliminary rough estimate
exceeds the available funds, adjustments should be
made to increase funding or reduce project costs.
3.2.7 Manual Operation
In manual operation, the treatment plant operator person-
ally performs all of the operating functions and makes all
operating decisions. The treatment plant equipment
does not accomplish any function independent of the
operating personnel. The equipment is simple and
performs the basic functions that the operator imple-
ments. Manual operation includes the following:
1. Motors (pumps, chemical pumps, etc.) with manual
start/stop controls. Some motors have manual
speed adjustment capability. Chemical pumps
have manual speed and stroke length adjustment
capability.
2. Valves with manual handle, lever, handwheel, or
chainwheel operators.
3. Instrumentation sensors with indicators. Instru-
mentation is installed in-line where operating data
(flowrate, total flow, pressure, and pH) are indicated.
In-line pH sensors are the only instruments that
require electric service.
3.2.2 Automatic Operation
In an automatic operation the treatment plant is operated
by a PLC, which initially is programmed by the operator,
the designer, the computer supplier, or an outside
specialist. If programmed by someone other than the
plant operator, the operator should be trained by that
individual to adjust program variables and, if necessary,
modify the program. The operator interface and printer
are the equipment items that the operator uses during
the performance of treatment plant functions. In addition,
the operator should calibrate and check all of the com-
ponents of the automatic operating equipment system on
a routine periodic basis. Finally, the treatment plant
operator or a designated instrumentation and control
specialist should be capable of performing emergency
maintenance and/or repairing all components. Every
function included in an automatic system should include
a manual override.
The equipment is more sophisticated and costly than
that used in manual operation. When functioning nor-
mally, automatic operation can function continuously
with minimal operator attention. This is recommended for
treatment systems in remote areas, or areas that are
difficult to access, and for systems for which operator
availability is limited. Automatic operation includes the
following:
1. Motors (pumps, chemical pumps, air compressors,
etc.) with automatic start/stop and speed adjustment
12
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controls. Chemical pumps may also have manual
stroke length adjustment. Motors should also have
manual on/off controls.
2. Valves with either pneumatic or electric operators.
Flow or pressure control valves with electronic posi-
tioners for valves with automatic operators. Valves
require manual overrides for operation during start-
up, power failure, or compressed air failure. Valves
should have opening and closing speed controls to
prevent water hammer during automatic operation.
Valve electronic position indicators are optional.
3. Automatic instrumentation may be electronic,
pneumatic, or a combination. The instruments and
controls should always be capable of transmitting
and receiving electronic information to and from the
PLC. In a fully automatic system, all of the control,
monitoring, and alarm functions are monitored and
controlled by the PLC. Backup manual instruments
(e.g., flowrate indicators, pressure indicators, pH
indicators, and liquid level indicators) are recom-
mended to provide verification of automatic instru-
mentation if treatment plant budget is available.
Comprehensive automatic alarms that notify
operators and/or shut down increments or the entire
treatment system relating to every type of system
malfunction at the moment such events occur is a
necessary function that should be incorporated in all
applicable instrumentation components.
3.2.3 Semiautomatic Operation
Semiautomatic operation that employs individual control-
lers to automatically start/stop or adjust some, but not
all, of the operational items in the system, can contribute
significantly to the treatment system operation without
computer control of the entire operation. Semiautomatic
functions can include alarms that notify operators of pro-
cess functions exceeding limits established for effective
and/or safe operation. Alarm events can be staged at
single (e.g., high) or dual (e.g., high-high) levels. In a
dual-level alarm, the first level notifies the operator that
the performance is out of tolerance; and the second level
shuts down either a single process function (e.g., a pump)
or the entire process. Examples of semiautomatic opera-
tional functions include, but are not limited to, the
following:
1. Flow control loop — includes an electronic flow
sensor with totalizer (e.g., magnetic flowmeter) that
sends an electronic signal to an electronic flow
controller (with high or low flowrate alarms), which in
turn sends an electronic signal to a flow control
valve (butterfly valve or ball valve) with an actuator
and electronic positioner. The plant operator
designates the required flowrate at the flow
controller. The controller receives the flowrate
measurement from the flow sensor and transmits
signals to the flow control valve positioner to adjust
the valve position until the flowrate matches that
required by the process. If the flowrate deviates
from the limits established for the process, a high
flowrate or low flowrate alarm will be issued.
2. Pressure control loop — includes an electronic
pressure transmitter that sends an electronic signal
to an electronic pressure controller (with high or low
pressure alarms), which in turn sends an electronic
signal to a pressure control valve with an actuator
and electronic positioner. The plant operator desig-
nates the required pressure at the pressure control-
ler. The controller receives the pressure measure-
ment from the pressure transmitter and transmits
signals to the pressure control valve positioner to
adjust the valve position until the pressure matches
that required by the process. If the pressure devi-
ates from the limits established for the process, a
high pressure or low pressure alarm should be
issued.
3. Treated water pH control loop — includes an
(optional) electronic pH sensor that transmits a pH
signal to a pH analyzer (with high or low level
alarms), which in turn sends an electronic signal to
shut off the raw water feed pump. The plant opera-
tor designates the required pH at the pH analyzer.
The pH analyzer receives the pH measurement from
the pH sensor and transmits signals to a chemical
feed pump. If the pH deviates from the limits estab-
lished for the process, a pH alarm should be issued.
4. Liquid level control loop — includes an electronic
liquid level sensor (e.g., ultrasonic level sensor),
which transmits an electronic liquid level signal to a
level controller that indicates the liquid level and
transmits an electronic signal to one or more motors
(pump, etc.) to start or stop. At the level controller,
the plant operator designates the required liquid
levels at which motors (pumps or mixers) are to start
and stop. The level controller receives the liquid
level measurement from the liquid level sensor and
transmits signals to the motor(s) to start or stop. If
the liquid level deviates from the limits established
for the process, then a high or low liquid level alarm
should be issued.
Many other process functions are performed automat-
ically by means of relays and other electrical devices. An
example is the electrical interlock of chemical feed
pumps with raw water pumps, which prevents chemical
feed into the process without the flow of process water.
14
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Another example is the use of a flow switch in a pres-
sure relief valve discharge pipe that, upon detection of
water flow, issues an alarm and stops the process feed
pump. The list of individual fail-safe automatic functions
is extensive and beyond the scope of this design
manual. All applicable codes, standards, and OSHA
requirements should be reviewed to determine which
requirements are applicable to the project. Then, based
on sound judgment, available budget, and treatment
plant operator capability and availability, a decision
should be made as to whether a given function should
be automatic or manual.
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 Preliminary Design should be devel-
oped. This includes sizing the equipment, selecting con-
struction materials, determining an equipment layout,
and upgrading the preliminary capital cost estimate to an
accuracy of ±20%. The deliverable items are:
1. Schematic flow diagrams (see Figure 3-2).
2. Preliminary process equipment arrangement
drawings (see Figures 3-3 and 3-4).
3. Outline specifications.
4. Preliminary capital cost estimate.
3.3.1 Treatment Equipment
Preliminary Design
This section provides the basic methodology for sizing
equipment items and selecting construction materials for
arsenic removal treatment systems using the ion
exchange treatment method with preoxidation of As(lll)
and regeneration of exhausted resin. An example illus-
trating this method is provided in Appendix B. The exam-
ple is based on use of a chloride-form SBA resin with
preoxidation of As(lll), reduction of free preoxidation
chemical, regeneration of exhausted resin, and manual
operation. The empty bed contact time (EBCT) selected
for this design example is 3 min. For systems using
different process parameters, the design information pre-
sented in this document is easily adjusted. For automatic
or semiautomatic operation, the system's basic design
does not change; however, equipment material and
installation costs can vary significantly.
3.3.1.1 Treatment Bed and Vessel Design
As discussed in Section 2.2, the recommended treat-
ment concept is based on the use of two vertical cylin-
drical pressure vessels piped in parallel followed by a
single vertical cylindrical pressure vessel piped in series
in the lag position. The treatment mode is downflow.
Treatment vessel piping should be configured to also
provide for resin backwashing (upflow). The treatment
vessel material employed in the design example pre-
sented in Appendix B is carbon steel (grade selection
based on cost-effective availability). Its fabrication,
assembly, and testing should comply with American
Society of Mechanical Engineers (ASME) Code — Sec-
tion VIII, Division 1. The interior should be lined with
abrasion-resistant material. Interior lining material should
be NSF-certified for potable water application and suit-
able for exposure to 10% sodium chloride (NaCI) regen-
eration solution. Vessel pressure rating should be
50 pounds per square inch gage (psig) (or the minimum
necessary to satisfy system requirements). FRP pres-
sure vessels frequently are used in place of lined carbon
steel. For very small systems, FRP pressure vessels are
preferred. For pressure vessels larger than 36 inches in
diameter, the lined carbon steel material is preferred.
Other vessel materials of construction (e.g., fiberglass),
internal lining materials (e.g., abrasion resistant epoxy,
rubber), and stainless steel without lining may also be
employed.
Basic technology that has evolved from experience
indicates that the downflow treatment process flowrate
should be 8 to 12 gpm/ft2. The data presented in this
design manual is based on a flowrate of 10 gpm/ft2
through the treatment bed. Then, using a 4-ft-deep bed,
the volume of resin (V) in each treatment vessel
provides a 2.5 gpm process water flowrate per cubic foot
of resin. This provides an EBCT of 3 min. An EBCT as
low as 1.5 min has been successfully used with some
resins. Standard FRP pressure vessels are available
with 6-ft straight sides and other sizes. A bed depth of
3 ft is recommended for those treatment vessels. FRP
pressure vessels utilizing 3-ft-deep beds will reduce the
flowrate to 7.5 gpm/ft2 to achieve the same 3-min EBCT.
Because the space between the grains of resin is
approximately 50% of the total bed volume, actual
residence time is approximately half the EBCT time. See
Figure 3-3 for treatment vessel design procedure.
When raw water is bypassed and blended back with
treated water, only the treated water is included in sizing
the treatment bed. To minimize wall effects, bed
diameter (d) should be equal to or greater than one-half
the bed depth (h). Good practice indicates that bed
depth should be a minimum of 30 inches and a maxi-
mum 6 ft. However, deeper beds have been applied
successfully. At less than minimum depth, distribution
problems may develop; and, at greater than maximum
depth, fine material removal and pressure loss become
problems.
15
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FREEBOARD
90% BED
EXPANSION
TREATMENT
MEDIA
4"
0.9h
SS
TREATMENT VESSEL
Minimum clearance
required between
bottom of vessel and
concrete pad
SYMBOLS
- TREATED WATER FLOW RATE (gpm)
- TREATMENT BED DIAMETER (ft.), d =
- TREATMENT BED DEPTH (ft.)
TREATMENT BED VOLUME - sd!tL (ft.1)
4
q
d
h
V
EBCT = -jj-
Md - DENSITY OF TREATMENT MEDIA (lb./ft/ )
Mw - WEIGHT OF MEDIA (Ibs.)
D - OUTSIDE DIAMETER OF TREATMENT VESSEL (ft.)
dH - DEPTH OF DISHED PRESSURE HEAD (ft.)
H - OVERALL HEIGHT OF TREATMENT VESSEL (ft.)
SS - STRAIGHT SIDE (ft.)
GIVEN
d > h/2. 2'-6" < h < 6'-0"
H = 2 dH + h + 0.9h + 6" + 1"
D = d + 1"
Md = 42 Ib./ft3 (VARIES WITH ION EXCHANGE RESIN)
Mw= Md x V - 42V (Ib.)
Figure 3-3. Treatment Bed and Vessel Design Calculations
16
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c
~O
J3
CN
CO
ZJ
D)
a.
a
3
D)
17
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As stated above, 3 min is the EBCT (2.5 gpm/ft3)
employed in the example in Appendix B. As the EBCT
decreases, regeneration of spent resin frequency in-
creases, requiring more operator attention and propor-
tionately more downtime. Conversely, decreasing the
treatment flowrate below the suggested 2.5 gpm/ft3
(3 min EBCT) rate increases the size of the treatment
beds and the treatment vessels, thereby increasing
capital cost and space requirements.
Carbon steel cylindrical pressure vessel fabrication is
standardized by diameter in multiples of 6-inch outside
diameter increments. Tooling for manufacture of pres-
sure vessel dished heads is set up for that standard.
Design dimensions differentiate between pressure ves-
sel and treatment bed diameters. The vessel outside
diameter (D) is approximately 1 inch greater than the
bed (or vessel inside) diameter, which conservatively
provides for both vessel walls with lining as well as
fabrication tolerances. If the pressure is high (100 psig or
greater), the 1 inch will increase to reflect the increased
vessel wall thickness. Unless system requirements
dictate higher operating pressure, low pressure (50 psig)
results in lower equipment cost.
Although there are many methods of distributing the
water flow through an ion exchange treatment bed, a
method that has been successfully used in operation is
recommended. The water is piped downward into the
vessel through an inlet diffuser. This diverts the flow into
a horizontal pattern. From there it radiates in a horizontal
plane prior to starting its downward flow through the
resin bed. The bed, in turn, is supported by a false flat
bottom, which is supported by the bottom head of the
pressure vessel by means of concentric support rings.
The false flat bottom also supports the horizontal header
and perforated plastic, fabric-sleeved lateral collection
system. Resin is placed in the vessel through circular
manway(s) with hinged cover(s) in the top head of the
vessel. The regeneration brine is fed into the treatment
bed through an injection distributor that penetrates into
the vessel through the vessel's straight side at a level
2 inches above the top of the resin bed. The injector is
supported by brackets integral with the treatment vessel
wall. A viewing window to determine water level during
the regeneration procedure vessel drain steps described
later in this design manual is also provided in the treat-
ment vessel wall. The treatment bed and vessel design
are illustrated in Figure 3-3. A typical example for deter-
mining treatment bed and treatment vessel dimensions
is presented in Appendix B.
3.3.1.2 Pipe Design
Material should be suitable for ambient temperature,
exposure up to 10% NaCI solution, system pressure,
and potable water service. Because of the high chloride
concentration, except for Alloy 20 and Hastalloy, metallic
materials are not suitable. Plastic materials such as PVC
or CPVC are satisfactory. PVC is usually the best selec-
tion because of its availability, NSF certification for pota-
ble water service, low cost, and ease of fabrication and
assembly. The drawbacks of PVC are its loss of strength
at elevated temperatures (above 100°F), high coefficient
of thermal expansion, external support requirements,
deterioration from exposure to sunlight, and vulnerability
to damage from impact. Nevertheless, these liabilities
are outweighed by the low cost and suitability for the
service. The piping should be protected from all of the
above concerns, except elevated water temperatures. If
elevated temperature exists (>100°F), the use of FRP
pipe is recommended. This material provides the
strength and support that is lacking in pure plastic.
The piping system should be economically sized to allow
for delivery of design flow without excessive pressure
losses. If water velocities present conditions for water
hammer (due to fast-closing valves, etc.), shock-
absorbing equipment should be provided.
Isolation and process control valves should be wafer-
style butterfly type, except in low flowrate systems where
small pipe size dictates the use of true union ball valves.
Using inexpensive, easily maintained valves that operate
manually minimizes capital cost. The valves can be
automated by the inclusion of pneumatic or electric
operators with electronic positioners.
Pressure regulators and flow control valves are recom-
mended for safe operation of manually controlled treat-
ment systems. See Appendix B for pipe size design
using the example previously employed for vessel and
resin bed design.
3.3.1.3 Instrumentation Design
System functional requirements that are adapted to
commercially available instruments should be specified.
Included are:
Range Accuracy
Variesta) ±2%
Instrument
1. Flow sensor
(indicator/totalizer)
2. Pressure indicator Variesta) ±1%
3. pH sensor/analyzer/alarm 0-14 ±0.1
4. Level sensor/indicator Varies(a) ±1%
5. Temperature indicator 30-120°F ±1%
(optional)
(a) Range to be compatible with application, maximum measurement
not to exceed 90% of range.
18
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3.3.1.4 Salt (NaCI) Storage and
Feed Subsystem
Salt feed and storage subsystems are required for
regeneration for each arsenic removal ion exchange
treatment plant. Depending on the size of the treatment
plant, salt can be procured in bags loaded on pallets, or
in 48,000-lb truckload bulk quantities. The salt grade is
normally coarse solar, with particle sizes ranging from
0.1 to 0.375 inch and a specific gravity of 70 Ib/ft Bulk
delivery provides the lowest unit price for this commod-
ity; but an atmospheric vertical cylindrical bulk storage
tank is required. The bulk storage tank capacity should
have a minimum of 72,000 Ib (1.5 truckloads); giving the
treatment plant operator adequate time for salt delivery
prior to consuming the remaining salt.
The bulk salt is fed by means of chute, hopper, con-
veyor, or other mechanism into a brine tank that also
receives water for dissolving the salt, A brine tank is
required to produce saturated brine solution whether it is
fed salt mechanically from a storage tank or manually by
the treatment plant operator. Saturated (26% NaCI) brine
solution is produced in the brine tank. The brine tank
volume requirement should be 150% (minimum) of the
brine required for regeneration of one treatment vessel.
The brine amount and concentration requirement vary
among resins. Therefore, the regeneration procedure
and brine quantity requirements should be obtained
directly from the resin manufacturer.
The storage tank and brine tank can be processed as a
single FRP unit. The storage tank (or brinemaker) should
be protected from the elements and include a contain-
ment basin located outside of the treatment building.
Typically the containment basins are sized for 110% of
the liquid contents of the brine tank. Except for the fresh
water feed pipe, no freeze protection is required. A feed
line from the brine tank is connected to an eductor that
will draw the concentrated brine into a dilution water
stream to form a concentration recommended by the
resin manufacturer. There should be ftowrate indicators
and flow totalizers in both the brine and dilution water
lines feeding the eductor so brine concentrations can be
controlled precisely. The example in Appendix B illus-
trates the method of designing the components for this
subsystem.
3.3.2 Preliminary Treatment
Equipment Arrangement
Once all of the major equipment size and configuration
information is available, a layout (arrangement drawing)
is prepared. The layout provides sufficient space for
proper installation, operation, and maintenance of the
treatment system, as well as each individual equipment
item. OSHA standards should be applied during the lay-
out stage. These requirements may be supplemented or
superceded by state or local health and safety regula-
tions or, in some cases, insurance regulations. A com-
pact arrangement to minimize space and resulting costs
should be furnished. Figure 3-4 illustrates a typical
preliminary arrangement plan. These arrangements pro-
vide no frills, but do include ample space for ease of
operation and maintenance. Easy access to all valves
and instruments reduces plant operator effort.
The type of building used to protect the treatment sys-
tem (and operator) from the elements depends on the
climate. Standard pre-engineered steel buildings are
low-cost, modular units. Concrete block or other material
also may be used. Standard building dimensions that
satisfy the installation, operation, and maintenance
space requirements for the treatment system should be
selected. The building should provide access doors,
lighting, ventilation, emergency shower and eye wash,
and a laboratory bench with sink. All other features are
optional.
Manual operation is the method employed in the design
example in Appendix B. The basic process requirements
should be reviewed at each stage of design to assure
that every item required to operate the process is
included. Although detailed design occurs during the
final phase, provision for operator access for every
equipment item should be provided.
Automatic operation does not require total accessibility;
access may only be necessary for maintenance func-
tions, for which ladder or scaffold access will suffice. The
extra equipment items required solely for automatic
operation (including, but not limited to, PLC, operator,
interface) occupy minimal space and are placed in loca-
tions that are most accessible to the operator.
3.3.3 Preliminary Cost Estimate
The preliminary cost estimate is prepared based on the
equipment selected, the equipment arrangement, and
the building selected. The material/equipment quantities,
labor quantities, labor unit pricing, and material/equip-
ment unit pricing should be summarized in a format that
is preferred by the owner. (See Table 3-1 for an exam-
ple.) This estimate should have an accuracy of ±20%. 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 and/or an inflation escalation
factor.
19
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Table 3-1. Preliminary Capital Cost Estimate Examples for Two Types of Ion Exchange Arsenic Removal Water
Treatment Plants at a Typical Location
Location:
Flowrate: 620 gpm
Date:
Cost ($1,000)
Manual
Operation
Treatment Vessels
Process Equipment
100
Ion Exchange Resin (750 ft3) 130
Process Piping, Valves, and Accessories 60
Instruments and Controls 13
Salt and Brine Storage _22
Subtotal 325
Mechanical
Electrical
Painting and Miscellaneous
Process Equipment Installation
35
12
Subtotal
63
Miscellaneous Installed Items
Regeneration Wastewater Surge Tank 70
Building and Concrete BO
Site Work, Fence, and Miscellaneous _20
Subtotal 170
Contingency 20% 112
Total" 670
Automatic
Operation
100
130
88
70
22
441
45
42
16
103
70
80
20
170
143
857
(a) Engineering, exterior utility pipe and conduit, wastewater and waste solids processing
system, finance charges, real estate cost, and taxes not included.
3.3.4 Preliminary Design Revisions
The Preliminary Design package (described above) is
submitted for approval prior to proceeding with the Final
Design. This package may require the approval of regu-
latory authorities, as well as the owner. If any changes
are requested, they should be incorporated and resub-
mitted for approval. Once all requested changes are
implemented and Preliminary Design approval is
received, the Final Design can proceed.
3.4 Final Design
After completion and approval of the Preliminary Design,
the Final Design is developed. This includes designing
all of the process equipment and piping, analyzing the
process system, designing the building (including site
work), and estimating the capital cost within 10%. The
deliverable items are:
1. Complete set of construction plans and
specifications.
2. Final capital cost estimate (see Table 3-2).
3. Design report (includes design calculations for
regulatory agency review).
The Final Design starts with the treatment system equip-
ment, continues with the building (including concrete
slabs and foundations, earthwork excavation/backfill/
compaction, heating, cooling, painting, lighting, utilities,
laboratory, personnel facilities, etc.); and completes with
the site work (including utilities, drainage, paving, and
landscaping). The latter items apply to every type of
treatment plant; although they are integral to the treat-
ment system, they are not addressed in this manual. The
only portions of the Final Design that will be addressed
are the pertinent aspects of the treatment equipment that
are not covered in the Preliminary Design section.
During Conceptual Design and Preliminary Design, the
basic equipment that accomplishes the required func-
tions is defined. The decisions are cost-conscious, using
minimum sizes (or standard sizes) and the least expen-
sive materials that satisfy the service and/or environ-
ment. However, in the Final Design, this effort can be
defeated by not heeding simple basic cost control prin-
ciples. Some of these are:
1. Minimize detail (e.g., pipe supports—use one style,
one material, and components common to all sizes).
2. Minimize the number of 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
mounted on brackets that are shop fabricated on
vessel).
20
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Table 3-2. Final Capital Cost Estimate Examples for Two Types of Ion Exchange Arsenic Removal Water Treatment
Plants at a Typical Location
Location:
Flow/rate: 620 gpm
Date:
Cost ($1,000)
Manual
Operation
Treatment Vessels
Process Equipment
99
Ion Exchange Resin (750 ft3) 127
Process Piping, Valves, and Accessories 45
Instruments and Controls 12
Salt and Brine Storage 20
Subtotal 303
Mechanical
Electrical
Painting and Miscellaneous
Process Equipment Installation
45
10
14
Subtotal 69
Miscellaneous Installed Items
Regeneration Wastewater Surge Tank
Building and Concrete
Site Work, Fence, and Miscellaneous
Subtotal
Contingency 10%
Total"'
67
74
17
158
53
583
Automatic
Operation
99
127
88
73
20
407
50
40
14
104
67
74
17
158
67
736
(a) Engineering, exterior utility pipe and conduit, wastewater and waste solids processing
system, finance charges, real estate cost, and taxes not included.
4. Skid-mount major equipment items {skids, in place
of piers and spread footings, distribute the weight of
vessels over small mat foundations, thereby
eliminating costly foundation work).
5. Where ambient conditions permit, use treatment
vessels as a heat sink to provide insulated building
cooling or heating or both (eliminates heating and/or
cooling equipment in addition to reducing energy
cost.) Consideration must be given, however, to
humid climates where cold tanks will result in
sweating problems.
6. Simplify everything.
All subsystems should be analyzed (refer to schematic
flow diagram in Figure 3-2) to account for all compo-
nents in both equipment specifications and installation
drawings. The drawings and specifications should pro-
vide all information necessary to manufacture and install
the equipment. Extra effort to eliminate ambiguity in
detail and/or specified requirements should be exer-
cised. All items should be satisfactory for service con-
ditions besides being able to perform required functions.
Each item should be easy to maintain; spare parts
necessary for continuous operation should be included
with the original equipment. All tools required for initial
startup, as well as operation and maintenance, should
be furnished during the construction phase of the
project.
Once construction, equipment installation, and check out
are complete, the treatment plant should proceed into
operation without disruption. After all components in
each of the subsystems have been selected, hydraulic
analysis calculations should be made to determine the
velocities and pressure drops through the system.
Calculations should be prepared for normal treatment
flow and backwash flow. The latter is more severe, but of
short duration. If pressure losses are excessive, the
design should be modified by decreasing or eliminating
losses (e.g., increase pipe size, eliminate bends or
restrictions).
Upon completion of installation, functional checkout
requirements should be accomplished. All piping should
be cleaned and hydrostatics I ly pressure-tested prior to
startup. All leaks should be corrected and retested.
Recommended test pressure is 150% of design pres-
sure. Potable water piping and vessels should be dis-
infected prior to startup. Disinfection procedures should
be in compliance with regulatory agency requirements
and material/equipment manufacturers' requirements/
limitations. All electrical systems should satisfy a func-
tional checkout. All instruments should be calibrated; if
accuracy does not meet requirements stated in Section
3.3.1.3, the instruments should be replaced.
21
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When the plant operation begins, a check on actual sys-
tem pressure drop is required. If there is a discrepancy
between design and actual pressure drop, the cause
should be determined (obstruction in line, defective
valve, installation error, design error, etc.) and rectified.
Pressure relief valves should be tested; if not accurate,
they should be adjusted or replaced.
3.4.1 Treatment Equipment
Final Design
This section provides details that apply specifically to
arsenic removal water treatment plants.
3.4.1.1 Treatment Bed and Vessel Design
The resin volume was determined based on bed dimen-
sions and the resulting weight in the Preliminary Design
(see Section 3.3.1.1). It is recommended that a minimum
of 10% extra resin be procured. For the lowest price and
ease of handling^ the resin should be ordered in fiber
drums {5 to 8 fr) on pallets. Several sources of SBA
resin are available for service in the application. If an
"equal" is to be furnished, a pilot test should demonstrate
that the process capability as well as the physical
durability of the substitute material is equal to that of the
specified material.
The vessel design should be simple. The vessel should
have a support system to transfer its loaded weight to
the foundation and ultimately to the soil. The loaded
weight includes the resin, the water, attached appurte-
nances (platform, pipes filled with liquid, etc.), the
vessel, and applicable seismic and/or wind loads. The
support legs or skirt should be as short as possible to
reduce head room requirements as well as cost.
If the vessels are skid-mounted, the support legs should
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, so costly piers, footings, and exca-
vation requirements are eliminated. The skid should
have provisions for anchoring to the foundation. Exterior
brackets (if uniform and simply detailed) are not costly
and provide supports that eliminate the need for cumber-
some costly field fabrications. Conversely, interior brack-
ets though required to anchor (or support) vessel internal
distribution or collection systems should be held to a
bare minimum because they are costly to line. Interior
linings should be abrasion-resistant. Alternatively, ves-
sels may be constructed of stainless steel (no lining
required). Vessel interior lining should extend through
the vessel opening to the outside edge of the flange
faces. Openings in the vessels should 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 or vertically at the center of the
bottom head.
3. Brine feed pipe — enters horizontally through
vertical straight side three inches above top of
treatment bed.
4. Air/vacuum valve (vent) — mounts vertically on top
head adjacent to influent pipe.
5. Resin removal — exits horizontally through vertical
straight side immediately above false flat bottom at
orientation assigned to this function.
6. Sight glass (12 inches high x 2 inches wide) —
located vertically with centertine at top of treatment
bed (serves to locate liquid level during drain steps
and to observe level of top of bed).
7. Manway — 16-inch-diameter (minimum) mounted on
top head with center line located within 3 ft of center
of vessel and oriented toward work platform.
Manway cover to be hinged or davited.
Pad flanges are recommended for pipe interfaces in
place of nozzles. Pad flanges are integral with the tank
wall. The exterior faces should be drilled and tapped for
threaded studs. Pad flanges save the cost of material
and 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 should be shimmed and leveled. All space
between the bottom surface of the skid structure and the
foundation should be sealed with an expansion-type
grout; provisions should be included to drain the area
under the vessel.
The type of vessel internal distribution and collection
piping used in operational arsenic removal plants is
described in the Preliminary Design (see Section 3.3.1.1).
Because there are many acceptable vessel internal
design concepts, configuration details will be left to
sound engineering judgment. The main points to con-
sider in the design are as follows:
1. Maintain uniform distribution.
2. Provide minimum pressure drop through internal
piping (but sufficient to assure uniform distribution).
3. Prevent wall effects, channeling, and dead areas.
22
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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 horizontal or vertical movement during
operation.
6. Ensure that construction materials are resistant to
corrosive inorganic ions (PVC and stainless steel are
acceptable).
Underdrain failures create significant problems; resin
loss, service disruption, and labor to repair problems are
very costly. A service platform with an access ladder
should be required for use in loading resin into the
vessel. A handrail, toe plate, and other OSHA-required
features should be included.
3.4.1.2 Pipe Design
Each piping subsystem should be reviewed to select
each of the subsystem components (see Figure 3-2).
Exclusive of the chemical subsystems, seven piping
subsystems are listed in the Conceptual Design (see
Section 3.2); they are:
1. Raw water influent main.
2. Intervessel pipe manifold.
3. Treated water effluent main.
4. Raw water bypass main.
5. Backwash/regeneration feed manifold.
6. Wastewatermain.
7. Sample panel (optional).
At this point, the design of each of the above sub-
systems proceeds. First, the equipment specifications for
each equipment component in each subsystem should
be defined. Then, a detailed installation drawing is devel-
oped that locates each component and provides access
for operation and maintenance. As each subsystem
nears completion, provisions for pipe system support
and anchorage, as well as for thermal expansion/con-
traction, should be incorporated in the Final Design.
Easy maintenance is an important feature in all piping
systems. Air bleed valves should be installed at all high
points; drain valves should 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 should be piped to waste. This feature satis-
fies both operator safety and housekeeping require-
ments. Bypass piping for maintenance of flow control,
pressure control, flowmeter, and other in-line mechanical
accessories is optional. Individual equipment item bypass
piping is costly and requires extra space. However, if
continuous treatment plant operation is mandatory,
bypass piping Should be included.
3.4.1.3 Instrument Design
Ease of maintenance is very important. Instruments
require periodic calibration and/or maintenance. Without
removal provisions, the task creates process control
problems. Temperature indicators (optional) require
thermal wells installed permanently in the pipe. Pressure
indicators require gauge cocks to shut off flow in the
branch to the instrument. pH sensing probes (optional)
require isolation valves and union type mounting con-
nections (avoids twisting of signal cables). Supply of pH
standard buffers (4.0, 7.0, and 10.0) should be specified
for pH instrument calibration. A laboratory bench should
be located adjacent to the sample panel. The sample
panel receives flow directly from sample points located
in the process piping. The sample panel consists of a
manifold of PVC or polyethylene tubing with shutoff
valves, which allows the plant operator to draw samples
from any point in the process at the laboratory bench.
Laboratory equipment should include a wall cabinet,
base cabinet with chemical-resistant countertop and
integral sink, 115V/1(J>/60Hz 20-amp duplex receptacle,
and laboratory equipment/glassware/reagents for analy-
sis of pH, arsenic, sulfate, and other ions. A detonized
water capability for cleaning glassware and dilution of
samples should be included.
3.4.1.4 Regeneration Wastewater
Surge Tank
Although treatment and disposal of regeneration waste-
water are not covered in this design manual, a surge
tank to receive the wastewater is provided. The waste-
water surge tank should receive the entire batch of back-
wash and regeneration wastewater from the start of
backwash to the completion of rinse steps. In the design
example used in this manual, the wastewater surge tank
is sized to contain 150 gal/ft3 of ion exchange resin in
the treatment vessel. However, because wastewater vol-
umes vary for each ion exchange resin, verification with
the ion exchange resin manufacturer and/or field pilot
test to precisely determine the required capacity of the
wastewater surge tank is recommended. This tank should
be a ground-level atmospheric carbon steel tank and
should include a carbon steel floor and roof and an
interior epoxy lining. The tank should be placed in a
reinforced concrete containment structure and should
include fill, chemical feed, drain, overflow vent, multiple
discharge, and multiple sample pipe connections. The
tank also should include one ground-level and one roof
manway (with safety ladder and handrails), provisions
for a liquid level indicator, an ultrasonic liquid sludge
level sensor, a liquid level controller, and a side-entry
mixer.
23
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3.4.2 Final Drawings
As stated above, all of the information required for
complete installation of an arsenic removal water
treatment plant should appear in the final construction
drawings and specification package.
Isometric drawings for clarification of piping subsystems
are recommended; these views clarify the assembly for
the installer (see Figure 3-5). Cross referencing draw-
ings, notes, and specifications are also recommended.
3.4.3 Final Capital Cost Estimate
Similar to the preparation of the preliminary cost esti-
mate, the final cost estimate, which is based on a takeoff
of the installed system, is prepared. The estimate now is
based on exact detailed information rather than the
general information that was used during the preliminary
estimate. The estimate is presented in the same format
(see Table 3-2) and is to be accurate within ±10%.
Because 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 should be submitted for approval to
the owner and the regulatory authorities. If changes or
additional requirements are requested, they should be
incorporated and resubmitted for approval. If clear com-
munication with the approving parties is provided, time-
consuming resubmittals should not be necessary. Upon
receipt of approval, the owner, with assistance from the
engineer, requests bids for the construction of the
arsenic removal water treatment plant.
24
-------
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4.0 Central Treatment System Capital Cost
4.1 Introduction
The client should be provided with the least expensive
ion exchange resin central treatment system that can
remove arsenic from a sufficient quantity of water that
will satisfy all potable water consumption requirements.
The economic feasibility evaluation should include the
initial capital cost along with the follow-up operating and
maintenance costs. This chapter covers the capital cost
that is affected by many factors including operating
costs.
The amount of water to be treated is the major, but not
the only, factor affecting capital costs. Other factors that
can have varying impact on the capital cost include, but
are not limited to, the following:
1. Raw water quality (temperature, pH, arsenic,
trivalent arsenic, sulfate, alkalinity, iron, manganese,
sodium, etc.).
2. Climate (temperature, precipitation, wind, etc.).
3. Seismic zone.
4. Soil conditions.
5. 100-year flood plain.
6. Existing and planned (future) potable water system
parameters:
a) Number of wells, location, storage, distribution
b) Water storage (amount, elevation, location)
c) Distribution (location, peak flows, total flow,
pressure, etc.)
d) Consumption (daily, annual, seasonal).
7. Backwash and regeneration wastewater disposal
concept.
8. Manual vs. automatic operation.
9. Financial conditions (cost trends, capital financing
costs, cash flow, labor rates, utility rates, chemical
costs, etc.).
Once the capital cost impacts that each of the above
variables can create have been determined, it becomes
apparent that a cost curve (or tabulation) based on flow-
rate alone is inadequate. Such a curve is presented later
in this chapter. A tabulation of the breakdown of these
capital costs is provided in Appendix C. If the impact of
these variables on the cost curve is considered, a mean-
ingful preliminary project cost estimate (as described in
Section 3.3.3) can be produced.
A user-friendly cost-estimating computer program (using
Microsoft® Excel Visual Basic) recently has been devel-
oped by Battelle on the use of adsorptive media and ion
exchange for arsenic removal (Battelle, 2002). This pro-
gram was funded by the U.S. EPA under Work Assign-
ment 3-20 of Contact No. 68C7-0008. A copy of the
computer program and the associated document can be
obtained from U.S. EPA National Risk Management Re-
search Laboratory, Water Supply and Water Resources
Division, in Cincinnati, OH 45268.
4.2 Discussion of Cost Variables
Each of the variables mentioned above has a direct
impact on the total installed cost for a central treatment
system. Ideally, conditions could exist that allow a mini-
mum cost system to be designed. A hypothetical exam-
ple would resemble the following:
1. Raw water quality presents no problem (no trivalent
arsenic, no sulfate, moderate temperature, etc.).
2. Warm moderate climate (no freezing, no high
temperature, minimal precipitation, no high wind).
3. No seismic requirements.
4. Existing concrete pad located on well compacted,
high-bearing-capacity soil.
26
-------
5. Single well pumping to subsurface storage reservoir
with capacity for peak consumption day.
6. Existing wastewater disposal capability adjacent to
treatment site.
7. Water softener salt and brinemaker on 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 the final estimate for
the example used in Appendix B is revised to incor-
porate the above ideal conditions, the cost estimate
would be reduced from $583,000 to $391,000 (see
Tables 3-2 and 4-1). Conversely, adverse conditions
could accumulate, resulting in a cost far in excess of that
for the typical treatment system for the same treatment
capability. The following subsections provide the basic
insight needed to minimize the cost impact resulting from
the above variables.
4.2.1 Water Chemistry
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
capital cost can be determined. High water temperature
(greater than 100°F) requires higher-cost piping material
and/or pipe support. To treat water that varies in temper-
ature beyond a certain range requires special provisions
for thermal expansion and contraction. Presence of
trivalent arsenic, manganese, turbidity, suspended sol-
ids, colloidal material, and/or other contaminants can
require the addition of pre-treatment steps to accomplish
removal prior to arsenic removal.
Each of the physical and chemical characteristics of the
raw water should be evaluated. The technical, as well as
the economic, feasibility of 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 materials.
Freezing is obviously damaging to piping and, in
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 increase the cost of the
building. The building cost will reflect wind loads, as well
as thermal and seismic requirements. Operator comfort
Table 4-1. Final Capital Cost Estimate Examples for Two Types of Ion Exchange Arsenic Removal Water Treatment
Plants at an Ideal Location
Location:
Flowrate: 620 gpm
Date:
Cost ($1,000)
Manual
Operation
Treatment Vessels
Salt and Brine Storage
Mechanical
Electrical
Painting and Miscellaneous
Miscellaneous Installed Items
Regeneration Wastewater Surge Tank 0
Building and Concrete 6
Site Work, Fence, and Miscellaneous 0
Subtotal 6
Contingency 10% 36
Total(a) 391
Automatic
Operation
Process Equipment
99
Ion Exchange Resin (750 ft") 127
Process Piping, Valves, and Accessories 45
Instruments and Controls 12
6
Subtotal 289
Process Equipment Installation
42
6
12
Subtotal 60
99
127
88
73
6
393
50
40
12
102
0
6
0
6
50
551
(a) Engineering, exterior utility pipe and conduit, wastewater and waste solids processing
system, finance charges, real estate cost, and taxes not included.
27
-------
rather than economic considerations may dictate build-
ing costs.
The aggregate cost for the building and regeneration
wastewater surge tank installation, along with their asso-
ciated civil work, becomes a major portion of the overall
capital cost (see Table 3-2). Great care should be
exerted in interpreting the climatological conditions and
their requirements.
4.2.3 Seismic Zone
Seismic design should comply with the requirements of
the local building codes. Buildings and tall slender equip-
ment are vulnerable to seismic loads. In zones of
extreme seismic activity, low profile equipment and
buildings are recommended.
4.2.4 Soil Conditions
Unless soil boring data are already available for the
treatment system site, borings should be required where
the foundations for heavy equipment items (e.g., treat-
ment vessels and regeneration wastewater surge tank)
will be located. If the quality of the soil is questionable
(fill or very poor load bearing capacity), additional soil
borings should be obtained. Poor soil may require costly
excavation/backfill and foundations.
Combinations of poor soil with rock or large boulders can
make foundation work more complex and costly. Rocks
and boulders, combined with extreme temperatures, can
result in very high installation costs for subsurface raw,
treated, and wastewater pipe mains.
4.2.5 100-Year Flood Plain
For water treatment facilities located within a 100-year
flood plain, the entire site should either be relocated
outside the 100-year flood plain, be elevated 3 ft above
the 100-year flood plain level, or be protected on all
sides by an armored berm that extends a minimum of
3 ft above the 100-year flood plain level.
4.2.6 Existing and Planned (Future)
Potable Water System Parameters
Many existing and planned (future) facility configurations
can significantly increase or decrease capital costs. The
most important factors are discussed below.
4.2.6.1 Number and Location of Wells
When there is only one well, excess arsenic should be
removed from the water before it enters the distribution
system. Theoretically, treatment can occur before or
after entering storage. Practically speaking, treatment
prior to entering storage is easier to control because the
treatment plant flowrate will be constant. If treatment
takes place after storage, or if there is no storage, flow-
rate is intermittent and variable. Treatment before stor-
age also can reduce or possibly eliminate the need for
adjusting the pH of the treatment water entering the
distribution system by blending the treated water in the
storage tank. As discussed in Section 2.2.3, during the
early part of the treatment cycle, the pH of the treated
water can be significantly reduced (bicarbonate remov-
al). Storage after treatment allows for blending of this
low pH water with the higher pH water produced during
the later part of the treatment cycle. The pH of the
distribution water will be the pH of the blended water in
the storage tank that may not require adjustment.
When more than one well requires treatment, a decision
is required regarding whether a single treatment plant,
treating water from all welis manifolded together, or
individual treatment plants at each well is more efficient
and cost-effective. Factors such as distance between
wells, distribution arrangement, system pressure, and
variations in water quality should be evaluated in the
decision. If all of the wells are in close proximity and
pump a similar quantity and quality of water, a single
treatment plant serving the entire system is preferable.
When wells are widely dispersed, manifolding costs
become prohibitively expensive, dictating implementa-
tion of individual treatment plants at each well. Fre-
quently the distances may be such that the decision is
not clear-cut; the designer then has to decide based on
other variables such as water quality, system pressure,
distribution configuration, and land availability.
Systems that require multiple treatment plants can
achieve cost savings by employing an identical system
at each location. This results in an assembly line
approach to procurement, manufacture, assembly,
installation, and operation. Material cost savings, labor
reduction, and engineering for a single configuration will
reduce the cost for the individual plant.
4.2.6.2 Potable Water Storage Facilities
Similar to the wells, the number, size, and location of
storage tanks can affect treatment plant size (flowrate)
and capital cost. If there is no storage capacity in the
system, the well pump should be capable of delivering a
flowrate equal to the system momentary peak consump-
tion; this could be many times the average flowrate for a
peak day. If there is no existing storage capacity, a
storage tank should be added with the treatment system.
Most systems have existing storage capacity. The stor-
age may be underground reservoirs, ground-level stor-
age tanks, or elevated storage tanks (located on high
28
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ground or structurally supported standpipes). The first
two require repressurization; the latter does not. Ele-
vated storage tanks apply a back pressure on the
ground-level treatment system, requiring higher pressure
(more costly) treatment vessels and piping systems.
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
flowrate (and resulting cost). A minimum storage capac-
ity of one half of system peak day consumption is
recommended.
As discussed in Section 4.2.6.1, storage after treatment
also provides the benefit of blending the treated water
prior to distribution. This blending may reduce or elimi-
nate the need for pH adjustment of the distributed water.
4.2.6.3 Distribution and Consumption
The factors that determine the sizing of the treatment
system are the well (or feed) pump flowrate, frequency
of treatment vessel regeneration, storage capacity, and
system consumption characteristics. Those factors
should be coordinated to provide a capacity to deliver a
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 (or feed)
pump is sized to deliver the peak daily requirement. The
treatment system in turn is sized to treat a minimum of
what the well (or feed) pump delivers.
The distribution system may anticipate future growth or
increased consumption. The well (or feed) pump should
then either pump a flow equal to or larger than the
maximum anticipated peak daily flows or be able to
adjust to a future increased flowrate. The treatment plant
in turn should incorporate capacity to treat the ultimate
peak flowrate or include provisions to increase the treat-
ment capacity in the future.
4.2.7 Backwash and Regeneration
Disposal Concept
Regeneration wastewater and waste solids processing
and disposal are not covered in the scope of this docu-
ment, but information on disposal options and labora-
tories studies have been reported on by MacPhee et al.
(2001). Spent brines containing more than 5.0 mg/L of
arsenic would be classified as a hazardous waste based
on the U.S. EPA TCLP. Depending on wastewater dis-
charge limits established by the U.S. EPA and state and
local regulatory agencies, wastewater disposal can be a
very significant cost item that should be evaluated in the
capital (and operating) cost projection. Requirements for
the disposal of the brine can vary from zero discharge to
discharge in an available existing receiving facility.
Brine can be pre-treated by chemical coprecipitation of
arsenic, with the addition of iron or aluminum coagulants
and appropriate pH adjustment for minimum solubility of
the precipitated metal hydroxides (MacPhee et al.,
2001). Dewatering of precipitated suspended solids (pre-
cipitated iron or aluminum hydroxides) should result in
the dewatered solids passing the U.S. EPA TCLP test.
The supernatant wastewater, though containing very low
arsenic concentration, should contain elevated levels
ofTDS. If the regulatory agency permits disposal of
the supernatant by conventional methods (surface dis-
charge, percolation), the disposal costs are not large.
The total volume of wastewater is normally less than
150 gal/ft3 of ion exchange resin. The treated water per
treatment cycle per cubic foot of ion exchange resin
varies significantly, depending primarily on the sulfate
concentration in the raw water and the capacity of the
resin. For example, if the resin capacity is 1.28 eq/L
(28 Kgrains as CaCO3 per ft3) of resin and the source
water has a sulfate concentration of 10 mg/L and an
arsenic concentration of 0.1 mg/L (0.209 meq/L - total),
then the treated water per cycle is 45,765 gal/ft3. Con-
versely, if the resin capacity is 0.67 eq/L (15 Kgrains as
CaCO3 per ft3) and the source water has a sulfate con-
centration of 50 mg/L and an arsenic concentration of
0.1 mg/L (1.041 meq/L - total), then the treated water
per cycle is 4,812 ga!/ft3. Therefore, the variation of the
ratio of wastewater to treated water can be significant.
This factor should be evaluated carefully when selecting
the ion exchange treatment method versus an alternate
treatment method.
4.2.8 Chemical Supply Logistics
Water softener salt (NaCI) is normally the cleanest grade
of sodium chloride solid-phase material available. It is
produced in various mesh sizes that can affect the dis-
solving rate, ease of handling, and cost. The material
can be procured in truckload bulk quantities or bags. The
truckload quantities are much cheaper and less labor
intensive and, therefore, more desirable. Truckload
quantity procurement requires bulk storage capability on
site with capability to transfer the salt to the brine pro-
duction/storage tank. There are commercially available
stand-alone salt storage/brinemaking systems units that
require very little operation time and are synergistic with
automatic operation. The systems are completely con-
tained in single vertical cylindrical fiberglass vessels.
They are complete packages including piping for pneu-
matic transfer of granular salt from delivery trucks and
dust collection. The vessels require a significant amount
of headroom (25-30 ft), which might not be available.
29
-------
Smaller brine tanks, sized specifically for the individual
system, require operator manual transfer of salt {by
means of bags) into the tank. The larger the ion
exchange resin bed, the greater the operator effort. The
NaCI requirement varies with the ion exchange resin
selected, but 10 Ib/ft3 can be used as a rule of thumb.
4.2.9 Manual vs. Automatic Operation
Automatic operation is technically feasible. However, the
periodic presence of an operator is always a require-
ment. The capital cost of automation (computer hard-
ware/software, valve operators, controls, instrumentation,
etc.), as well as maintenance costs may exceed budget
limits. Therefore, either manual or semiautomatic opera-
tion is normally furnished. The advantages and dis-
advantages of manual, automatic, and semiautomatic
operation require careful evaluation prior to determina-
tion of the proper selection.
4.2.10 Financial Considerations
Many financial factors should be considered by the
designer and his client. The client can superimpose cri-
teria (beyond any of the technical factors mentioned
above) that result in increased (or decreased) capital
cost. These include, but are not limited to, inflationary
trends, interest rates, financing costs, land costs (or
availability), cash flow, labor rates, electric utility rates,
and chemical costs. Alt or part of this group of factors
could affect the capital investment because interest rates
are low, inflation is anticipated, cash is available, or labor
and electric utility rates are high. Or the opposite can be
true. The varying combinations of these factors that
could develop are numerous; each will affect the ultimate
capital cost.
4.3 Relative Capital Cost of
Arsenic Removal
The relative capital costs of central ion exchange
treatment plants based on the treated water flowrate 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 are provided in Appendix C. The curve in
Figure 4-1 is based on the facility criteria employed in
the hypothetical design for the 620 gpm arsenic removal
treatment system in Appendix B. These costs are repre-
sentative of average capital costs. The curve in Figure 4-2
is based on the same treatment system located at an
ideal location at which the facility requirements are
eliminated or minimized (see Section 4.2 and Table 4-1).
This information demonstrates significant differences in
capital costs that can occur for the same treatment plant
at different sites.
Figures 4-3, 4-4, and 4-5 provide examples of the equip-
ment and material itemized cost data utilized during the
preparation of the capital cost estimates in this manual.
A complete material and labor takeoff is required for the
preparation of a capital cost estimate for any given
project. Current equipment and material unit cost infor-
mation should be obtained from the original manu-
facturer or distributor for each item. The assembly/
installation costs for each unit of each item should be
obtained from the provider of that service. The capital
material and labor costs for the installed treatment plant
are then obtained by means of tabulations inclusive of all
items, along with quantities of each item and the asso-
ciated equipment/material/labor unit costs. Figure 4-3
provides an example of an ASME Code pressure vessel
manufacturer's proposed price for a treatment vessel.
Figure 4-4 provides an ion exchange resin manufactur-
er's published price information for SBA resin in compli-
ance with NSF drinking water requirements. Figure 4-5
provides pipe, fitting, and valve itemized cost estimating
information based on a major material distributor's pro-
posed material prices and an experienced mechanical
system installation contractor's proposed labor prices. In
addition to the basic costs provided in the above figures,
additional costs include, but are not limited to, tools, mis-
cellaneous materials (nuts, bolts, washers, gaskets, pipe
supports, ladders, etc.) freight handling/storage/protec-
tion of materials/equipment, mobilization, and demobili-
zation. Though not individually itemized in the cost tabu-
lation presented in the tables included in this manual, all
such costs have been included. Therefore, the estimated
capital cost provided in the tabulations in Appendix C
and the curves in Figures 4-1 and 4-2 exceed the spe-
cific costs provided in Figures 4-3, 4-4, and 4-5.
30
-------
5.0
3 4.0
3.0
200
300 tOO
FLOWRATE, gpm
SOD
Figure 4-1. Capital Cost vs. Flowrate at Typical Locations for Arsenic Removal Water Treatment Plants
by Means of the Ion Exchange Process (for itemized cost breakdown, see Appendix C)
5,0
8 «
3.0
2.0
1.0
Figure 4-2. Capital Cost vs. Flowrate at ideal Locations for Arsenic Removal Water Treatment Plants by
Means of the Ion Exchange Process (for itemized cost breakdown, see Appendix C)
-------
CODE PRESSURE VESSEL FABRICATOR QUOTATION
FOR ION EXCHANGE TREATMENT VESSELS (three required)
Vessel Specification and Quotation #1280m
Customer
Attention
R.F.Q. Pricing for your Arsenic Removal Water Treatment Project
07/24/01
Description
Size
Design Pressure and Temp
Corrosion Allowance
Design Criteria
Radiography
Code Stamp
Constructed of
Supports
Vertical Skid-Mounted Vessel
120" O.D. x 8' 0" S/S; Capy, 5,450 gal
50 psig @ 175 degrees Fahrenheit
None requested or provided
A.S.M.E. Section VIII, Div. 1
Spot (RT-3)
Yes and National Board Registration
Carbon steel
(4) carbon steel legs with skid to provide 24" to bottom seam
Nozzles and Appurtenances:
2 20" quick opening manways
1 4" - CL150 FF single-tapped pad flange, hillside-type
1 4" - CL150 FF single-tapped pad flange
2 8" - CL150 FF single-tapped pad flanges
1 12" x 3" vertical viewing window
1 False bottom
8 Interior carbon steel lateral support clips
1 Interior carbon steel header support clip
2 sets Exterior pipe support brackets
2 Lifting lugs
1 Skid
Valves, gauges, gaskets, or any items not listed above are excluded.
Surface Preparation and Coatings:
Interior surface prep: SSPC-SP-5 white metal sandblast
Interior surface coat: Plasite 4006 HAR (35 MDFT)
Exterior surface prep: SSPC-SP-6 commercial sandblast
Exterior surface primer: Rust inhibitive primer
Exterior topcoat: None requested or provided
Note, interior coating is forced cured to meet NSF STD 61 requirements for potable water
Shipping: weight, 9,500 Ib; dimensions, 10' diameter x 12.5' OAL.
Price: FOB Madera CA, $ 27,500.00 each, not including taxes.
Price based on a quantity of 2, and is valid for 90 days.
Delivery schedule: based on current schedule.
Drawings for approval: 2 weeks after order
Fabricate and ship: 12 to 14 weeks after drawing approval.
Terms: Progress payment to be arranged.
Figure 4-3. Code Pressure Vessel Fabricator Quotation for Ion Exchange Treatment Vessels
32
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August 21, 2001
Mr. John Doe
ABC Engineering, Inc.
P.O. BoxlOOO
DEFG.AA 10000-1000
Ref: Municipal Bid Quotation for Arsenic Removal Ion Exchange Resin
Dear Mr. Doe,
XXXXZ is a Type I strong base anion (SBA) resin that has exhibited excellent performance for the removal of arsenic
(As +5) and in its subsequent capacity regain through regeneration with salt (NaCI). XXXXZ undergoes rigorous
cleaning steps for potable water application. This is to remove the organic extractabies as well as taste and odor
caused by leftover by-products that are common to SBA resins. This cleaning process which is designated by the
postscript "Z" sets XXXXZ apart from other strong base resins with similar function. XXXXZ has been evaluated and
is certified under NSF STD 61 for potable water applications.
The pricing on XXXXZ will vary with the quantity, ship to location, and exact resin specifications (such as particle size
range and packaging). Although municipal applications can be very large, they can also be very modest. A good
range to use would be $165 to $300 per cu ft, with the upper range being applied to volumes of less than 100 cu ft
and the lower range being applied to purchases of multiple truckloads (i.e., >2,000 cu ft). Use a price of $250 for 200
cu ft, $200 for 400 cu ft, and $185 for 800 cu ft (full TIL) quantities. Beyond that, the economies of scale diminish
rapidly.
We have many successful installations of XXXXZ in use for arsenic removal. The end results are generally
nondetectable levels of arsenic, providing the original influent was properly speciated and, when necessary, an
oxidation system was incorporated into the pre-treatment design.
Yours truly,
Jane Roe
Area Representative
Figure 4-4. Example of SBA Resin Quotation for Arsenic Removal Drinking Water Treatment Systems
Provided by Prominent Manufacturer
33
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Item
8" SCH 80 PVC Pipe (PIE)
6" SCH 80 PVC Pipe (P/E)
4" SCH 80 PVC Pipe (P/E)
1%" SCH 80 PVC Pipe (P/E)
8" SCH 80 PVC Tee (s * s x s)
6" SCH 80 PVC Tee (s x $ x S)
4" SCH 80 PVC Tee (s x s x s)
8" SCH 80 PVC 90° ELL (s x s)
6" SCH 80 PVC 90° ELL (s x s)
4" SCH 80 PVC 90° ELL (S x s)
W SCH 80 PVC 90° ELL (s x s)
8" SCH 80 PVC Reducer (s x S)
6" SCH 80 PVC Reducer (s x s)
4" SCH 80 PVC Reducer (s x S)
8* SCH 80 PVC Coupling (s x S)
6" SCH 80 PVC Coupling (s x s)
4" SCH 80 PVC Coupling (s x S)
W SCH 80 PVC Coupling (s x s)
8" SCH 80 PVC Van Stone Flange (s)
6" SCH 80 PVC Van Stone Flange (s)
4" SCH 80 PVC Van Stone Flange (s)
8" Wafer Style PVC Butterfly Valve
6" Wafer Style PVC Butterfly Valve
4" Wafer Style PVC Butterfly Valve
1/2" PVC Ball Valve (s x s)
8" PVC Wafer Style Check Valve
TOTALS
Qty
380ft
170ft
90ft
30ft
24
6
5
19
5
8
8
8
2
1
5
5
4
2
62
16
19
14
8
7
2
3
Material
Unit Price(a)
($)
8.00/ft
5.00/ft
3.50/ft
1.00/ft
170ea.
70 ea.
50 ea.
120 ea.
45 ea.
20 ea.
Sea.
70 ea.
30 ea.
25 ea.
45 ea.
35 ea.
20 ea.
5ea.
55 ea.
35 ea.
20 ea.
280 ea.
225 ea.
180ea.
60 ea.
650 ea.
Total
Material
($)
3.040
850
270
30
4,080
420
250
2,280
225
160
40
560
60
25
225
175
80
10
3,410
560
380
3,920
1,800
1,260
120
1.850
26,080
Labor Unit
Price(b)
($)
5.00/ft
4.00/ft
3.00/ft
2.00/ft
15.00 ea.
15.00 ea.
10.00 ea.
12.50ea.
12.50 ea.
10.00ea.
7.50 ea.
12.50 ea.
12.50ea.
10.00ea.
12.50 ea.
12.50 ea.
12.50 ea.
10.00 ea.
12.50ea.
12.50ea.
10.00ea.
50.00 ea.
40.00 ea.
25.00 ea.
25.00 ea.
1 00.00 ea.
Total Labor
($)
1,900
680
270
60
360
90
50
240
65
80
60
100
25
10
65
65
50
20
775
200
190
700
320
175
50
300
6,900
Total
($)
4,940
1,530
540
90
4,440
510
300
2,520
290
240
100
660
85
35
290
240
130
30
4,185
760
570
4,620
2,120
1,435
170
2.150
32,980(c)
(a) Prices effective August, 2001 (markup included).
(b) Labor rate @ $50/hour.
(c) Tools, installation equipment, pipe supports, accessories
bolts, nuts, gaskets, mobilization, material storage, etc. not included.
Figure 4-5. Process Pipe, Fittings, and Valves: Itemized Cost Estimate for a Manually Operated
620-gpm Arsenic Removal Water Treatment System
34
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5.0 Treatment Plant Operation
5.1 Introduction
Upon completion and approval of the final design pack-
age (plans, specifications and cost estimate), the owner
(client) advertises for bids to construct the treatment
plant. The construction contract is normally awarded to
the firm submitting the lowest bid. Occasionally, circum-
stances arise that disqualify the low bidder, in which
case the lowest qualified bidder is awarded the contract.
Upon award of the construction contract, the design
engineer may be requested to supervise the work of the
construction contractor. This responsibility may be lim-
ited to periodic visits to the site to assure the client that
the general intent of the design is being fulfilled, or it
may include day-to-day inspection and approval of the
work as it is being performed. The engineer should
review and approve all shop drawings and other informa-
tion submitted by the contractor and/or subcontractors
and material suppliers. All acceptable substitutions
should 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 inspec-
tion. 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.
Plant operation consists of five basic modes: treatment,
backwash, regeneration, slow rinse, and fast rinse.
Operating details for each of these modes follow. It is
important to note that each of the modes of operation
uses raw water, never treated water. Before the plant is
put into full operation, however, several plant preparation
steps that lead up to routine operation must be com-
pleted. These steps include operation review, resin load-
ing, resin backwashing and regeneration, and initial
startup preparation.
5.2 Plant Preparation
Preparation for treatment plant startup, startup, and
operator training may or may not be included in the con-
struction contract. Although this area of contract respon-
sibility is not germane to this manual, the activities and
events that lead up to routine operation are discussed.
This section discusses the steps in the sequence that
the operator performs them. The operator can be the
contractor, the owner's representative, or a third party.
5.2.7 Operation Review
Following construction and prior to plant startup, system
operating supplies, including treatment chemicals, labor-
atory supplies, and recommended spare parts, should
be procured and properly stored. The treatment plant
operations and maintenance instructions (O&M Manual)
also should be available at the project site. Included in
the O&M Manual are the valve number diagram (which
corresponds to tags on the valves), a valve directory,
and a valve operation chart (see Figure 5-1 and Table 5-
1), The operator should thoroughly review the O&M
Manual, become familiar with every component of the
plant, and resolve any questions that arise prior to
startup.
5.2.2 Resin Loading
Before the plant can be operated, the ion exchange resin
must first be placed in the treatment vessels. Before
loading the resin, the treatment vessels and piping
should be disinfected in accordance with American
Water Works Association (AWWA) standards (C653-97)
or state regulations.
The placement of the SBA resin in the treatment
vessels, which takes place immediately prior to startup,
is a critical step in system performance. The SBA resin
is usually delivered in drums. The amount of resin is
35
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or
o
o
•^
=3
m
in
o
s
O)
ra
15
i—
0)
J3
E
IO
D)
36
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Table 5-1. Valve Operation Chart for Treatment Vessels in Treatment and Regeneration Operational Modes(a)
Mode
Treatment
Backwash
Drain to top of bed
Fill tank with brine
Regeneration
Drain to top of bed
Fill tank with water*'
Slow rinse(t>>
Fast rinse
Standby
Treatment
Flowrate
{gpm/ft1)
10
Regeneration
3-4
Gravity
2
2
Gravity
2
2
10
-
10
Flow
Duration
(min)
W
20 (max.)
5
20
20
5
20
20
30 (max.)
-
w
1
•
X
X
X
X
X
X
X
•
X
•
2
•
X
X
X
X
X
X
X
X
X
•
Valve No.
3 4
X
•
X
X
X
X
X
X
X
X
X
X
•
X
X
X
X
X
X
X
X
X
5
X
X
X
•
•
X
•
•
X
X
X
6
X
X
•
X
•
•
X
•
•
X
X
(a) Refer to Figure 5-1 for valve location.
(b) Water feed to eductor to bypass eductor during water fill step.
(c) Treatment cycle duration.
Legend: x = valve closed; • = valve open.
Vessel 1A
Valve No.
A1 Feedwater
A2 Treated water
A3 Backwash feed
A4 Backwash to waste
A5 Brine feed
A6 Regeneration to waste
Vessel 1B
Valve No.
B1 Feedwater
B2 Treated water
B3 Backwash feed
B4 Backwash to waste
B5 Brine feed
B6 Regeneration to waste
Vessel 2
Valve No.
21 Feedwater
22 Treated water
23 Backwash feed
24 Backwash to waste
25 Brine feed
26 Regeneration to waste
determined on a volumetric basis. The actual density
varies with the degree of packing of the bed and, unless
instructed otherwise by the manufacturer, 42 Ib/ft3 is a
recommended resin density for use in weight calcula-
tions. The resin contains a small amount of fines that
can interfere with efficient process flow. Eye, skin, and
inhalation protection are, therefore, recommended dur-
ing vessel loading.
The vessel should be filled half way with water prior to
placing the ion exchange resin through a manway in the
top head of the vessel. Then the resin should be care-
fully distributed into the vessel from above. The water
separates the fines from the resin beads, protects the
underdrain assembly from impact, initiates stratification
of the bed, and thoroughly wets the resin. It is recom-
mended that the bed be placed in two lifts. In the three-
bed treatment system, resin and backwashing steps can
be alternated between the three treatment vessels.
Thereby, the resin placement process can be a continu-
ous operation.
Each bed should be thoroughly backwashed with raw
water after each lift. The backwash should expand the
bed approximately 90% unless directed otherwise by the
resin manufacturer. To accomplish this, the backwash
flowrate should be in the range of 3 to 4 gpm/ft for the
area determined by the top of the treatment bed. The
backwash rate is sensitive to water temperature. During
bed placement, the duration of each backwash step
should be a minimum of 20 min; and, depending on the
quantity of fines in the resin, should extend until the
wastewater is clear. 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 channel-
ing, excessive pressure drop, or wall effects can devel-
op. The extra backwashing effort during bed placement
permits fines at the bottom of the bed to work their way
up and out to waste. The backwash water should be
directed to the wastewater surge tank. Care must be
taken to prevent loss of resin during backwash. An in-
line sight glass, plus a manual sample point incorporated
in the backwash wastewater pipe, will allow the plant
operator to immediately detect the presence of resin
beads leaving the treatment vessel. Subsequent to back-
wash, each treatment vessel should undergo the entire
regeneration cycle.
5.2.3 Initial Startup Preparation
After the resin has been loaded in the vessels and thor-
oughly backwashed, each treatment vessel should
37
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undergo an entire regeneration cycle prior to placing the
plant on line. It is highly recommended that representa-
tives of the controls and instrumentation suppliers be on
hand to assist the operator during the initial regeneration
cycle.
Prior to starting operation, all instruments should be
calibrated. If chemical preoxidation is required, the pre-
oxidation feed equipment and the preoxidation chemical
reduction equipment that removes excess oxidant (if
required) from the feedwater stream also should be
adjusted and placed into operation.
Pressure drop should be checked (see Section 3.4) just
prior to plant startup. See Table 5-2 for a typical manu-
facturer's calculated pressure drop through a represent-
ative ion exchange resin at varying treatment downflow
rates and water temperature. If there is a pressure loss
problem, it should be corrected prior to treatment
startup.
Table 5-2. Typical Manufacturer's Downflow Pressure
Drop Data
Strong Base Anion Ion Exchange Resin
Water flowrate
(gpm/ft2)
6.0
8.0
10.0
12.0
14.0
16.0
Pressure drop in psi
per foot of bed depth
0.5
0.7
1.0
1.3
1.6
2.0
Note: Water temperature BO"F.
At this point the plant should be cleaned up. Good
housekeeping should begin at this time and be contin-
ued on a permanent basis.
5.3 Treatment Mode
After the plant preparation steps have been completed,
the downflow treatment for the first (virgin) run can now
begin. See Table 5-1 for valve positions for this function.
One of the primary stage treatment vessels is placed
into operation while the other primary stage treatment
vessel is placed in the standby mode. The second stage
(or lag) treatment vessel is then placed into operation,
where it remains as a fail-safe polishing treatment step,
specifically to prevent any arsenic leakage from ever
entering the distribution system. In the event that break-
through occurs in a primary stage treatment vessel, the
arsenic peak enters the second stage treatment vessel.
The second stage treatment vessel then performs its
designated function; prevention of the arsenic peak from
entering the distribution system. The second stage
should be regenerated as soon as practical following the
breakthough of any arsenic into the second stage col-
umn. In no case should completion of the regeneration
of the second stage treatment vessel be deployed
beyond completion of the treatment cycle of the second
primary stage treatment vessel. In the meantime, treat-
ment is immediately resumed in the other primary stage
treatment vessel, which is transferred from the standby
to the operational mode.
The basic flow schematic for the treatment mode is
illustrated in Figure 5-2.
Depending on the requirements of the state or local reg-
ulatory agency, water samples may have to be analyzed
at a certified testing laboratory prior to approval of dis-
tribution of treated water.
In the parallel process using two treatment vessels, the
entire arsenic removal process takes place in one ves-
sel. The operator must understand that sulfate ions are
removed preferentially over arsenic ions. Therefore, a
band of arsenic ions moves through the resin column
ahead of the sulfate ions that proceed downward
through the bed, exhausting the ion exchange capacity
until the arsenic breaks through. Breakthrough is defined
as the first measurable appearance of As(V) in the
effluent from a treatment vessel. Although the detectable
level will vary depending on the analytical method used
to measure the arsenic, it probably would be near
3 ug/L. At arsenic breakthrough, the arsenic concentra-
tion in the treated water surges to a level higher than
that in the raw water. An example of this phenomenon is
shown in Figure 1-1. This event must be prevented.
Immediately prior to arsenic breakthrough, the process
flow should be switched to the standby primary stage
treatment vessel. The spent treatment vessel should
then be regenerated and placed in the standby mode.
Upon exhaustion of the ion exchange capacity of the
other primary stage treatment vessel, the first primary
stage treatment vessel should be returned to the
treatment mode.
Several methods can be used to anticipate or project
arsenic breakthrough from the lead vessel and the time
for regeneration. First, if a pilot plant study was con-
ducted prior to design and operation, the information
from this study could be used to predict run lengths and
regeneration time. Another method is doing a theoretical
calculation based on the feedwater chemistry and the
resin manufacturer's resin exchange capacity. As has
been mentioned frequently in previous sections of this
manual, run lengths are very sulfate-dependent because
sulfate is preferred over arsenic, nitrate, bicarbonate,
and other anions removed by the process. Conse-
quently, a rough treatment run length can be calculated
based on the sulfate concentration and the resin
38
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<§>
TREATMENT FLOW - VESSEL "1A" IN LEAD POSITION
<&>
TRBWEXT
wssa
1A
I
VESSEL "lA" BACKWASH
«MCNt)
VESSEL "1A' REGENERATION & SLOW RINSE
VESSEL 1"A" FAST RINSE
Figure 5-2. Basic Operating Mode Flow Schematics (Note: chemical bulk storage tanks not shown for
clarity) (see Figure 5-1 for symbol legend)
manufacturer's published resin exchange capacity. A
theoretical calculation of run length in bed volumes
based solely on the sulfate concentration of the source
water is shown in Figure 5-3. Actual treatment run
lengths would be less because of the removal of other
anions and operational variables.
Using the run length estimate from either pilot plant data
or a theoretical calculation, the plant operator should
initially provide a capacity cushion of 10% in determining
the volume of water to be treated to prevent arsenic
breakthrough at the exhaustion of ion exchange resin.
Arsenic field test kits also can be used to obtain rapid
39
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20
40 60 80- 100 120
Sulfate Concentration - mg/L
160
•0.8 eq/L Resin Capacity
•1.0 eq/L Resin Capacity
•1.25 eq/L Resin Capacity
Figure 5-3. Resin Removal Capacity Based on Sulfate Concentration and Resin Capacity
detection of arsenic breakthrough events. By limiting the
volume of water to be treated to 90% of the estimated
capacity, a 10% cushion is provided for a category of
adverse conditions/events that can reduce the estimated
capacity of that resin. These adverse items include, but
are not limited to, the following:
1. Flow channeling.
2, Flow wall effects.
3. Uneven flow conditions that distort the treatment
wave front.
4. Defective resin beads.
5. Uneven feedwater distribution and/or treated water
collection subsystems characteristics due to treat-
ment vessel internal piping design/manufacture/
assembly (including dead areas).
6. Variation of raw water sulfate and arsenic
concentrations.
The treatment plant operator should focus attention on
the quality of the treated water. Special attention is
required as the treated water volume approaches resin
capacity exhaustion. As the experience data base for the
treatment system expands, a predictable performance
pattern develops that results in a routine repeatable treat-
ment cycle. If the 10% resin capacity cushion does not
prevent arsenic breakthrough, the cushion should be
increased until breakthrough is consistently prevented.
Conversely, to reduce regeneration wastewater produc-
tion and reduce treatment system operating cost, the
plant operator may try to expand the treatment capacity
of the first stage treatment vessel by reducing the capac-
ity cushion below 10%. The treated water distribution sys-
tem should always be protected from an arsenic break-
through event by the second stage treatment vessel.
When the treated water is approved for distribution, it
flows through an (optional) 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 feed pump magnetic starter) de-energizes the
feed pump. Simultaneously, the preoxidation and (op-
tional) pH adjustment chemical pumps shut down
because their controls should be interlocked with the
feed pump power circuitry. The (optional) pH override
automatically prevents any treated water for which pH is
out of tolerance from entering the distribution system. In
the event of such an excursion, the operator (either
manually or automatically) diverts the out-of-tolerance
water to waste, determines the cause of the deviation,
and makes corrections prior to placing the treatment
system back on line.
The operator should be cognizant of the fact that the
more water treated during a run, the lower the operating
cost. In raw waters where the arsenic level is very low,
part of the raw water can bypass treatment and be
blended back with the treated water. A skilled operator
develops many techniques to minimize operating costs.
High iron content in raw water can cause problems
during a treatment run. The iron oxidizes, precipitates,
and is filtered from solution by the ion exchange resin.
This results in an increased pressure drop and short-
ened treatment runs. Raw water iron content greater
40
-------
than 0.3 mg/L is cause for concern. However, if the iron
concentration is above 0.3 mg/L, the secondary MCL, an
iron removal process should be considered as the
treatment process for arsenic removal in place of the ion
exchange process.
5.4 Backwash Mode
It is important to backwash the bed with raw water after
each treatment run prior to regeneration, for two
reasons. First, any suspended solids that have been
filtered from the raw water by the treatment bed tend to
blind the bed. Therefore, these particles should be
removed from the bed prior to regeneration. Second,
even though filtration may have been negligible, the
downward flow tends to pack the bed. An upflow back-
wash will expand the bed and break up any tendency
toward wall effects and channeling. A backwash rate of
3 to 4 gpm/ft2 (depending on water temperature) will
expand the ion exchange resin approximately 90%,
which is recommended by some resin manufacturers
and is employed in the example presented in this
manual. Some resin manufacturers recommend lower
backwash flowrates, resulting in less bed expansion (but
never less than 50%). As mentioned in prior sections,
this rate varies with resin bead size, material density,
and water temperatures. Care must be taken to avoid
backwashing the resin out of the treatment unit. Back-
washing normally takes 15 to 20 min to eliminate filtered
suspended solids from the resin. It is important to pro-
vide sufficient time during the backwash mode to not
only expand the bed, but also to carry out the back-
washed particulate material.
Refer to Table 5-1 for valve positions for the backwash
mode. The basic flow schematic for the backwash mode
is illustrated in Figure 5-2. Backwash water samples
should be inspected to determine that filtered material is
being removed and resin is not being washed out of the
bed. A sight glass should be provided in the wastewater
pipe to observe the clarity of the backwash water.
Excessive backwash causes abrasion that results in
attrition of the resin beads. That also wastes raw water
and increases the wastewater disposal volume. There-
fore, the backwash volume should be minimized. The
resin level of each treatment bed should be inspected
periodically through a viewing window provided in the
treatment vessel to determine whether bed volume has
changed. Upon detection of resin loss, makeup resin
should be added.
5.5 Regeneration Mode
The most efficient method of regenerating a treatment
bed upon completion of a treatment run is by a downflow
feed of a 6% to 10% NaCl brine solution. The concen-
tration and the amount vary with each resin. Drain steps
prior to and after feed of the brine solution minimize dilu-
tion of the brine. A 6% NaCl concentration is adequate
for this process. If drain steps are provided during the
regeneration mode, these steps must be performed by
manual operation because such steps are not included
in automatic control systems^
The objective of regeneration is to remove all arsenic
ions from the bed before it is returned to the treatment
mode. A skilled operator might be able to reduce the
concentration of the NaCl to lower than 6% with the
same high efficiency performance. This lower brine con-
centration and lower total brine feed can reduce con-
sumption for regeneration and wastewater for disposal.
As described in Chapter 3.0, the dilution of the saturated
brine takes place at an eductor in the regeneration feed
piping. Both the raw water and the 26% NaCl are
metered prior to mixing in the eductor in the regeneration
pipe. The accuracy of the metering ranges from ±2% to
±5% depending on the type of flow measurement. If
using a 6% NaCl concentration, meter readings that are
high for water and low for brine result in lower than
planned brine concentration and loss of regeneration
efficiency.
The volume of 6% brine solution required per regenera-
tion will vary with each resin. Therefore, the requirement
should be verified with each resin manufacturer. The
volume of 6% NaCl brine solution per regeneration used
in the example in this manual is 20 gal/ft3 of resin. That
is based on a flowrate of 0.5 gpm/ft3 for a period of
40 min. Once again, the designer should check with the
resin manufacturer to verify the regeneration require-
ments. The minimum time recommended for the solution
to flow through the bed is 30 min. In the example in this
manual, a 4-ft-deep treatment bed with a flow of
2 gpm/ft2 for a period of 40 min is used.
For the valve position during each step of the regenera-
tion mode, refer to Table 5-1. The basic flow schematic
for the regeneration mode is illustrated in Figure 5-2.
After backwash, prior to the regeneration step, the bed
should be drained to remove water that dilutes the con-
centration. Upon completion of the regeneration, the
feed is turned off, and the brine tank refilled. Again the
brine is drained to within 1 inch of the top of the treat-
ment bed to prevent dilution of the brine.
5.6 Rinse (Slow and Fast) Mode
In the example presented in this manual, for the slow
rinse, the raw water flows for 40 min at a 2 gpm/ft2 flow-
rate downward through the bed, flushing out the brine
and the arsenic. Some manufacturers advocate that this
step should be completed in 20 min, resulting in a
41
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smaller quantity of wastewater produced. The downflow
fast rinse then takes place at the treatment flowrate for a
period of time sufficient for nine bed volumes to flow
through the treatment bed. Therefore, for a 4-ft bed depth
and a treatment flowrate of 10 gpm/ft2, the resulting fast
rinse flow volume is 270 gal/ft2 and the flow time
required is 27 min. Some manufacturers advocate fast
rinses specifying only these bed volumes. The regener-
ated treatment vessel should then be placed into service
in the standby position. It should remain there until the
treatment vessel in the operating position is removed for
regeneration.
5.7 Regeneration Wastewater
A summary of the regeneration process employed in the
example presented in this manual is shown in Table 5-3.
As previously mentioned, the regeneration may produce
less wastewater. However, because it is necessary to
provide a surge tank with sufficient capacity to contain a
complete batch of regeneration wastewater, it is recom-
mended that the surge tank be conservatively oversized.
The volume of wastewater produced during the regen-
eration of a treatment bed will vary with the physical/
chemical characteristics of the ion exchange resin. Typ-
ical volumes of wastewater generated per cubic foot of
resin during each regeneration cycle are shown in Table
5-3. Operational experience at a specific treatment plant
will present deviations from these quantities. A conserv-
ative rule of thumb is that 150 gal of wastewater is pro-
duced per cubic foot of resin during each regeneration.
5.8 Operator Requirements
A qualified operator for an arsenic removal water treat-
ment plant should have thorough arsenic removal pro-
cess training, preferably at an existing treatment plant.
The operator should be able to service pumps, piping
systems, instrumentation, and electrical accessories.
The operator must be totally informed about the safety
requirements and physical/chemical characteristics of
pre-treatment oxidizing chemicals. Corrosive chemical
safety requirements as to clothing, equipment, antidotes,
and procedures should be thoroughly understood. The
operator should be thoroughly trained to run routine
water analyses, including the method for determining
arsenic levels. The operator should be well grounded in
mathematics for operation cost accounting and treat-
ment run record keeping. The operator, above all, should
be dependable and conscientious.
5.9 Laboratory Requirements
In addition to the 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 American Public Health Association
(APHA), AWWA, and Water Environment Federation
(WEF). This manual supplies the plant operator with all
necessary information for acceptable methods for ana-
lyzing water. A recommended list of items for analysis is
illustrated in Figure 3-1. The primary requirement is for
accurate analysis for arsenic. As long as the pH meters
are calibrated and cleaned regularly, high precision mea-
surements are easily obtained. Care should be exer-
cised to prevent contamination of pH buffers.
Total arsenic can be preserved effectively in field sam-
ples and analyzed by several analytical methods down
to the MCL of 10 ug/L or less. Total arsenic is preserved
by acidifying the sample to pH <2. The Arsenic Rule lists
four U.S. EPA-approved analytical methods: inductively
coupled plasma-mass spectroscopy (ICP-MS), graphite
furnace atomic absorption (GFAA), stabilized tempera-
ture platform (STP) GFAA, and gaseous hydroxide
atomic absorption (GHAA). These methods are U.S.
EPA-approved for compliance requirements and require
expensive analytical equipment that is found only at
extremely large water treatment plants.
During the past few years, several companies have
developed portable test kits for field analysis of arsenic.
Some of these tests kits have been evaluated under the
U.S. EPA Environmental Technology Verification (ETV)
program by the Advanced Monitoring Systems Center
managed by Battelle in partnership with U.S. EPA.
These kits were tested for monitoring arsenic in the 1 to
Table 5-3. Typical Regeneration Process
Step
No. Step
1 Backwash
2(a) Regeneration
3 Slow rinse
4 Fast rinse
Liquid
Raw water
6-10% NaCI
Raw water
Raw water
Flow
Direction
Upflow
Downflow
Downflow
Downflow
Rate
(gpm/ft2 or as noted)
3-4
0.5 gpm/ft3
2
10
Time
(Minutes or Wastewater
Bed Volume) (gal/ft3)
5-20 min
40 min
40 min
9BV
Total
20
20
20
70
130
(a) Resin manufacturer should be consulted on specific regeneration requirements.
42
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100 (jg/L range. Information on the test kits can be found
on the Internet (http://epa.gov/etv/verifications/vcenter1-
21.html). Although these test kits may be adequate for
monitoring process performance, they are not U.S. EPA-
approved methods for use in reporting MCL compliance
data. For regulatory data, water samples must be ana-
lyzed by U.S. EPA/state-certified testing laboratories
employing U.S. EPA-approved methods.
5.10 Operating Records
A system of records should be maintained at the treat-
ment plant covering plant activity, plant procedures, raw
water chemical analyses, plant expenditures, and inven-
tory of materials (spare parts, tools, etc.). The plant
operator should have the responsibility of managing all
aspects of the treatment plant operation. The operator is
accountable to the water system management. The
recommended records system should include, but not be
limited to, the items described in the following sub-
sections.
5.10.1 Plant Log
A daily log should be maintained in which the plant oper-
ator records daily activities at the plant. This record
should include a listing of scheduled maintenance,
unscheduled maintenance, plant visitors, purchases,
abnormal weather conditions, injuries, sampling for state
and other regulatory agencies, etc. This record should
also be used as a tool for planning future routine and
special activities.
5.70.2 Operation Log
The operator should maintain a log sheet for each treat-
ment run for each treatment unit so that a permanent
plant performance record will be on file. Figure 5-4 illus-
trates a copy of a suggested condensed form.
5.10.3 Water Analysis Reports
If the plant operator has the ability to analyze for arsenic
onsite with a field test kit, a schedule for arsenic analysis
of the raw water, effluent from the lead vessel, and
effluent from the second vessel should be established,
with the lead vessel effluent schedule based on the
estimated length of the treatment run. During the first
several (3 to 5} treatment cycles, it is recommended that
one or more effluent samples from the lead vessel be
collected toward the end of each of the treatment cycles
to confirm that the arsenic has not broken through the
lead vessel and entered the second vessel. Once the
operator determines that a predictable and repeatable
performance pattern has developed, the number and
frequency of sampling can be reduced.
The schedule for sampling the raw water and effluent
from the second vessel can be less frequent than for the
effluent from the lead vessel. Once-per-month total raw
water sampling for analysis of arsenic, sulfate, etc. gen-
erally is adequate because most ground water does not
undergo a drastic change in quality. Changes in raw
water can occur, however, that 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 reference tool.
5.10.4 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, labora-
tory equipment and reagents, tools, services, and other
sundry items. This should be supplemented by a file of
up-to-date competitive prices for items that have been
purchased previously.
5.10.5 Correspondence Files
The plant operator should retain copies in chronological
order of ail correspondence pertaining to the treatment
plant, including intradepartmental notes and memos and
correspondence with other individuals and/or organiza-
tions.
5.10.6 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.
5.10.7 Miscellaneous Forms
The operator should have an adequate supply of acci-
dent, insurance, and other miscellaneous forms.
5.11 Treatment Plant Maintenance
The maintenance concept for the arsenic 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 equip-
ment items should have isolating valves, and all piping
systems should have vents at high points and drains at
low points. Equipment manufacturers' recommended
spare parts should be stocked at the treatment plant to
avoid lengthy maintenance shutdowns.
If the entire treatment plant needs to be shut down and
the plant has a bypass, the plant itself can be bypassed.
43
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ARSENIC REMOVAL WATER TREATMENT PLANT
Unit* Run#
TREATMENT TO RESERVOIR
Meter End
BYPASS TO RESERVOIR
Meter End
BACKWASH TO WASTE
Meter End
REGENERATION TO WASTE
Meter End
SLOW RINSE TO WASTE
Meter End
FAST RINSE TO WASTE
Meter End
TOTAL WASTEWATER SUMMARY
Total to Tank
OPERATION LOG
Date Start
Meter Start
Meter Start
Meter Start
Meter Start
Meter Start
Meter Start
k-gal PERCENT WASTE
Date End
Total Treated
Total Treated
Total
Total
Total
Total
k-qal
k-aal
k-aal
k-aal
k-aal
k-aal
%
TREATED WATER LOG
Date
Treatment
Meter
(k-gal)
A Meter
(k-gal)
£ A Meter
(K-gal)
Raw As
(mg/L)
Treated
As
(mg/L)
A As
(mg/L)
As
Removed
(mg)
IAS
removed
(mg)
Figure 5-4. Arsenic Removal Water Treatment Plant Operation Log
44
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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 arsenic being
pumped to distribution, an event that should not occur
without the approval of the water system manager and
the regulatory agency.
5.12 Equipment Maintenance
Equipment manufacturer's maintenance instructions
should be included in the "Suppliers Equipment Instruc-
tions" section of the O&M Manual.
5.13 Ion Exchange Resin
Maintenance
The plant operator should inspect the surface of each
treatment bed at least once a month. If the level of a bed
lowers more than two inches, makeup ion exchange
resin should be added after completion of a treatment
run, prior to backwash and regeneration. Makeup ion
exchange resin should be evenly distributed. There
should be a minimum depth of 2 ft of water above the
surface of the existing bed, through which the makeup
ion exchange resin should be added. The vessel should
be closed immediately and backwashed at 4 gpm/ft2 for
at least 20 min. It is very important to flush the fines out
of the virgin ion exchange resin as soon as it is wetted.
It is important that the treatment beds should not remain
in the drained condition for more than 30 min. Treatment
units not in use should remain flooded.
5.14 Treatment Chemical Supply
The operator should carefully monitor the consumption
of salt and liquid chemicals and reorder when necessary.
The operator should have a method of determining the
depth of liquid in day tanks and the brine tank and
equating that to the volume of liquid in the tank.
5.15 Housekeeping
The plant operator should wash down all equipment at
least once per month. Floors should be swept. 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 neu-
tralized and cleaned up immediately. Equipment should
be repainted at least once every five years.
45
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6.0 Central Treatment Plant Operating Cost
6.1 Introduction
The prime objectives of central treatment plant design
are to provide the client with a low-capital cost installa-
tion that works efficiently and reliably, is simple to oper-
ate, and is inexpensive to operate. Operating costs are
normally passed directly on to 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 ion exchange resin costs
5. Replacement parts and miscellaneous materials
costs
6. Wastewater and waste solids processing and
disposal costs (not included this manual).
Because the consumer's water bill normally is based on
mete red water consumption, the costs for treatment are
prorated on the unit of volume measurement. The units
of volume are usually 1,000 gal or 100 ft3 (750 gal). The
rate units employed in this design manual are 0/1,000
gal. Some systems do not meter consumption; instead
they charge a flat monthly rate based on size of branch
connection to the water main. Though this latter mode of
distribution saves the cost of meters as well as of read-
ing meters, it does not promote water conservation.
Therefore, more water is pumped, treated, and distrib-
uted, resulting in a net increase in operating cost.
The common denominator that applies to both the oper-
ating cost and the bill for water consumption is the unit of
volume, 1,000 gal. Each operating cost factor can be
reduced to cost/1,000 gal. Each of the above-mentioned
operating costs is discussed in the following sections.
The sum total of the annual operating costs based on
total water production yields the cost per 1,000 gal (the
unit cost to be applied to the consumer's bill).
6.2 Discussion of Operating Costs
Similar to capital cost, many variables affect operating
cost. This manual discusses the types of operating cost
variables that are evaluated during each stage of the
design phase of the project and during the operation of
the treatment plant. The example method employed in
this manual provides the user with the ability to design
the treatment system with maximum capability and mini-
mum cost. The system includes anion exchange resin
with spent resin regeneration (with manual or automatic
operation).
The size of system is a variable that impacts the cost of
operation. Operating labor requirements generally do not
vary with the size of the system, except possibly for the
very small systems. Therefore, the smaller the system,
the greater the labor cost per volume of water treated.
Items that influence the selection of method of operation
are the feed water arsenic concentration and the arsenic
removal capacity of the ion exchange resin. The fre-
quency of regeneration, cost of treatment chemicals,
cost of ion exchange resin, cost of regeneration waste-
water disposal, and cost/availability of operating person-
nel not only vary with geographic locations, but are also
sensitive to price volatility.
The manual operation method is satisfactory for the ion
exchange arsenic removal process; however, automatic
operation is a common method of running ion exchange
systems. Although operator skill and knowledge require-
ments are greater for automatic operation, there is an
overall benefit and cost saving potential by not requiring
operator presence during regeneration. The following
subsections delve into each of the operating costs previ-
ously listed.
46
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6.2.1 Treatment Chemical Cost
The treatment chemicals discussed are limited to salt
and pre-treatment oxidation chemicals. Other chemicals
may be required for special requirements such as pH
adjustment, corrosion inhibition, precipitation of regener-
ation wastewater contaminants, dewatering of precipi-
tated solids in wastewater, disinfection, etc.; however,
these are site-specific requirements that are not covered
in this manual.
Because the chemicals are used in the treatment of
water for public consumption, it is recommended that
samples of each chemical delivery be analyzed for
chemical content. It also is recommended that the chem-
ical 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 governing regulatory agency. Finally, the
treatment chemicals should comply with NSF/ANSI STD
60.
Chemical costs are variable. Like all commodities, they
are sensitive to the supply and demand fluctuation 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 some cases, the delivery
costs are greater than the cost of the chemical. The
commodity price of each chemical can vary from one
region of the country to another, as well as from supply/
demand marketplace forces. In the Conceptual Design,
the chemical logistics should be evaluated and the most
cost-effective mode of procurement should be deter-
mined.
The chemistry of the raw water to be treated is the most
significant factor affecting treatment chemical consump-
tion and cost. Sulfate is the key ingredient in the raw
water; the higher the sulfate, the higher the chemical
cost.
6.2.1.1 Salt Cost
The most economical method of procuring softener salt
is in bulk truck quantities (48,000 pounds). The trucks
are loaded at the manufacturer's/distributor's site and
delivered directly to the treatment plant where the salt is
transferred to a storage tank equipped with dust-
containment equipment. Transfer is accomplished pneu-
matically by a blower on the truck (unless the treatment
plant can provide compressed air). From the storage
tank, the salt is conveyed or transferred to the brine tank
where dissolution takes place, resulting in a 26% satu-
rated brine solution. In addition to the lower commodity
price resulting from minimum handling and storage of
the salt, there is minimum chance of contamination.
Alternatively, the softener salt can be procured in 50-lb
bags on pallets (49 bags/pallet) for easy manual loading
into the brine tank by the plant operator. For potable
water service, there are stringent limits on the levels of
contaminants in the salt that should be rigidly enforced.
The delivered cost of truck quantities of softener salt
ranges from 3 to 60/lb, depending on the geographic
location of the treatment plant. Similarly, pallets of bags
of salt range in price from 6 to 100/lb.
The salt is consumed in the regeneration process as the
chloride ions replace the As(V), sulfate, and other anions
removed from the water during treatment. The salt con-
sumption is a function primarily of the raw water sulfate
level that dictates the frequency of regeneration and the
volume of water over which this cost is distributed. The
higher the sulfate level, the fewer gallons treated per
regeneration.
In the example in Appendix B, the cost of the salt is
4^/1,000 gal. The actual salt cost should normally fall in
the range of 10 to 60 per 1,000 gal of treated water.
6.2.1.2 Pre-Treatment Oxidation Chemical Cost
As discussed previously, various preoxidation chemicals
such as chlorine, potassium permanganate, and ozone
are capable of oxidation of As(lll) to As(V). This design
manual does not address the preoxidation chemical
selection. However, it is necessary to stress that excess
preoxidation chemicals can possibly be detrimental to
the ion exchange resin. If preoxidation is required, the
resin manufacturer should be contacted to determine if
the chemical selected has detrimental effects on the
resin or the acceptable exposure concentration. If the
preoxidation chemical must be removed from the source
water before ion exchange treatment, removal measures
must be incorporated into the design. For example,
sodium hypochlorite (chlorine) can accomplish the pre-
oxidation function. If the free chlorine remaining in solu-
tion after the oxidation of As(lll) to As(V) must be
removed, it can be done by a bed of granular activated
carbon (GAG) that will convert the excess chlorine to
chloride.
Reaction time, feedrate, shelf life, degradation character-
istics, selection of compatible materials for handling/stor-
age, etc. should be determined and incorporated into the
design for the selected preoxidation chemical. The cost
for the equipment and consumable chemicals is not a
major factor in the total capital and operating cost for the
ion exchange treatment system.
47
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6.2.2 Operating Labor Cost
Operating labor is the most difficult cost to quantify. The
operator is required to be dependable and competent;
however, the position is not always a full-time one.
Depending on the size of the system and other duties,
the operator's time should be spread over several
accounting categories. Except for days when regenera-
tion takes place for manually operated systems, the
treatment plant normally requires less than 1 hour per
day of operator attention. During regeneration, operator
time will be approximately 4 hours.
On routine operating days, the operator merely checks
the system to see that preoxidation chemical feed (if
used) is being properly controlled, takes and analyzes
water samples, checks instruments (flow, temperature,
pressure), and makes entries in daily logs. Exceptions to
the normal routine include, but are not limited to, arsenic
analyses in the treatment plant laboratory, equipment
maintenance, and salt truck deliveries. During the
remainder of the time, the operator should be able to
operate and maintain other systems (distribution, pumps,
storage, etc.), read meters, or handle other municipal
responsibilities (e.g., operate sewage treatment plant).
For ion exchange treatment systems with automatic
operation, the operator requires specialized skills to
service the automatic instruments and controls. This
class of operator may justify a higher salary. There are
several other variables that can influence the rate of pay
for this category of operator; and, unless these skills can
be utilized for other assignments, the higher pay rate
may not be justified. Another factor is the availability of
outside personnel for service for the automatic instru-
ments and controls. That variable has to be evaluated on
a case-by-case basis. In this manual, an increase in
salary of $2.50 per hour is utilized to illustrate the cost
impact A second operator should be available to take
over in case of an emergency; that individual should be
well trained in the operation of the plant.
Using the example treatment plant presented in Appen-
dix B, the cost of operating labor will be as follows: (it is
assumed that the hours not used for treatment plant
operation will be efficiently used on other duties).
Given:
Flowrate = 620 gpm
Annual average utilization = 50%
Number of regenerations per year = 65
Operator annual salary = $30,000
Overhead and fringe benefits = 30%
Available man hours per year = 2,000/man
Then:
Manual Automatic
Operation Operation
Number of hours on
regeneration/year 65 x 4 hr = 260 hr
Number of hours on routine
operation/year (365-65) x 1 = 300 hr 365 hr
Number of hours on extra
tasks 50 x 2 hr = 100hr 100hr
Total plant operator time = 660 hr 465 hr
Ohr
Operator hourly rate:
$30,000/2,000 hr
30% (overhead and fringe
benefits)
Operator rate
= $15.00/hr
= $ 4.50/hr
$19.50/hr $22.00/hr
Total manual operation operator cost:
660 hrx$l9.50/hr = $12,870
Total automatic operation operator cost:
465 hrx$22/hr= $10,230
Total gallons water produced:
0.5 (50% utilization) (620 gpm) x 1,440 min/day x
365 days/year = 163,000,000 gal/year
Manual operation labor cost/1,000 gal:
$12,820/163,000 (1,000 gal) = $0.08/1,000 gal
Automatic operation labor cost/1,000 gal:
$10,230/163,000 (1,000 gal) = $0.06/1,000 gal.
If the operator for the manual method had no other
responsibilities and the entire salary was expended
against this treatment plant operation, the operating
labor cost would become $0.24/1,000 gal. For the auto-
matic method, the operating labor cost would become
$0.27/1,000 gal. Obviously, there are many variables
that can be controlled in different ways. Depending on
the motivation of the utility management, the operating
labor cost can be minimized or expanded over a very
broad range. In the case of a very high production plant,
the operating labor requirement is not significantly larger
than that for a very small treatment plant. Therefore,
depending on relative salaries, the resulting cost can
range from a few cents to more than a dollar per 1,000
gal. However, the operating labor cost should always fall
in the $0.02 to $0.30/1,000-gal range.
6.2.3 Utility Cost
The utility cost is normally electric utility. However, there
can also be telephone and natural gas (or oil) utility
costs. Telephone service to the treatment building is
48
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recommended as a safety precaution in case of an acci-
dent, as well as operator convenience. Cost for that ser-
vice should be the minimum available monthly rate.
Depending on the local climate, the cost for heating can
vary. The purpose of the building is to protect the equip-
ment from elements (primarily 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
should have an auxiliary heat source to prevent pipes
from freezing if water is not flowing. If the client deter-
mines that the treatment building is to serve additional
functions, heating to a comfort temperature could be an
additional required cost.
Electric power will be needed for the following functions:
1. Chemical pumps.
2. Instrumentation and alarms.
3. Lighting.
4. Convenience receptacle.
5. Extra load or feed pump for regeneration/backwash
wastewater and loss of head through the treatment
system.
Electric utility rates may vary considerably from one
geographic location to another. In, August 2001, rates
varied from $0.03 to S0.20/KWH. The electric utility cost
can range from $0.001 to $0.01 per 1,000 gal under
normal conditions. Under abnormal conditions, it could
be $0.02/1,000 gal or higher.
6.2.4 Replacement Ion Exchange
Resin Cost
The consumption of resin due to attrition during back-
wash/regeneration of exhausted resin and the loss of ion
exchange capacity caused by performance degradation
during normal operation are the primary factors requiring
the addition of fresh resin in the treatment vessels. Back-
wash, if conducted carelessly, can result in resin carry-
over. An excessive backwash rate can expand the resin
by an amount that carries the resin out of the vessel,
resulting in a loss of resin. Monitoring the backwash
water will detect and provide protection from that occur-
rence. If backwash water flows into the wastewater surge
tank, the lost resin can be recovered.
Another way for the ion exchange resin to be lost is
through the effluent underdrain (collection system) within
the bed. If ion exchange resin beads ever appear in the
treated effluent, the treatment vessel should immediately
be taken out of service for inspection (and repair) of the
underdrain system.
A conservative bed replacement estimate is 20% per
year. In the Appendix B example where two 250-ft3 beds
are used, the attrition in the polishing vessel should be
zero.
The cost of replacement resin is as follows:
Cost = Number of beds * volume of resin/bed * resin
cost x 20% = 2 x 250 ft3 x $165/ft3x 0.20 = $16,500
Then, the ion exchange replacement cost = $16,500/
163,000 (1,000 gal) = $0.10/1,000 gal.
SBA resin costs vary significantly with the quantity of the
order, as well as other market variables including, but
not limited to, geographic location, competition, etc. Per
price quotations presented in Figure 4-4, the cost for
truckload quantities of resin is $165/ft3; quotations for
less than truck quantities range up to $300/ft3. For cost
estimating purposes in this design manual, the $165/ft3
cost is used for the largest systems and graduates up to
$300/ft3 for the smallest system. However, the actual
cost for a given treatment plant should be negotiated on
a case-by-case basis. The cost for makeup ion exchange
resin should range between $0.05 to $0.20 per 1,000 gal
of treated water.
6.2.5 Replacement Parts and
Miscellaneous Material Costs
Parts and material are very small operational cost items.
Replacement parts (e.g., pump, diaphragms, seals, and
replacement pump heads) should be kept in stock in the
treatment plant to prevent extended plant shutdown in the
event a part is required. Also included are consumables
such as chemicals, laboratory reagents (and glassware),
and record keeping supplies. An operating allowance of
$0.01/1,000 gal of treated water is conservative.
6.3 Operating Cost Summary
The arsenic removal water treatment plant operating
costs discussed above are summarized in Table 6-1. For
ion exchange arsenic removal water treatment plants in
which flowrates, raw water arsenic concentration, raw
water sulfate concentration, ion exchange, labor rates,
and utility rates vary from the values used in the exam-
ple in Appendix B, the operating costs will deviate from
those indicated in Table 6-1.
49
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Table 6-1. Operating Cost Tabulation*8'
Dollars/1,000 gal Treated
Water
Operating Cost Items
Flowrate: 620 gpm
Treatment Chemicals
Operating Labor
Utility
Replacement Ion Exchange Resin
Replacement Part and Misc.
Material
TOTAL
Manual
Operation
($)
0.04tD)
0.08
0.01
0.15
0.02
0.30
Automatic
Operation
($)
0.04(D)
0.06
0.01
0.15
0.02
0.28
(a) Wastewater and waste solids, processing and disposal not
included.
(b) Cost to oxidize As(lll) to As(V) not included.
50
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7.0 References
Battelle, 2002. Cost Estimating Program for Arsenic
Removal by Small Drinking Water Facilities. Developed
for the United States Environmental Protection Agency,
National Risk Management Laboratory, Cincinnati, OH.
December.
Clifford, D.p 1999. Ion Exchange and Inorganic Adsorp-
tion. Water Supply and Treatment, 5th ed. McGraw-Hill,
New York, NY.
Clifford, D., Ceber, L, & Chow, S., 1983. Arsenic{lll)/
Arsenic(V) Separation by Chloride-Form Ion-Exchange
Resins. Proceedings of the Tenth American Water
Works Association (AWWA) Water Quality Technology
Conference, Norfolk, VA.
Clifford, D.A. etal., 1998. Arsenic Ion-Exchange Process
with Reuse of Spent Brine. Proceedings of the American
Water Works Association (AWWA) Water Quality
Technology Conference, Dallas, TX.
Chowdhury, Z. et. al., 2002. Implementation of Arsenic
Treatment Systems, Part 1. Process Selection.
AWWARF Final Report.
Edwards, M. et al., 1998. Considerations in As Analysis
and Speciation. J. AWWA, 90:3:103-113.
Ficklin, W.H., 1982. Separation of Arsenic (III) and Arse-
nic (V) in Groundwaters by Ion Exchange. Talanta,
30:5:371-373.
Gallagher, P.A. et al., 2001. Speciation and Preservation
of Inorganic Arsenic in Drinking Water Sources Using
EDTA with 1C Separation and ICP-MS Detection.
J, Environ. Monit, 3:371.
Ghurye, G.L., & Clifford, D., 2001. Laboratory Study on
the Oxidation of Arsenic III to Arsenic V. EPA/600/R-01/
021. United States Environmental Protection Agency,
National Risk Management Laboratory, Cincinnati, OH.
Ghurye, G.L. et al., 1999. Combined Arsenic and Nitrate
Removal by Ion Exchange. J. AWWA, 91:10:85.
Horng, LL, & Clifford, DA, 1997. The Behavior of Poly-
protic Anions in Ion Exchange Resins. Reactive and
Functional Polymers, 35:1/2:41.
Lowry, J.D., & Lowry, S.B., 2002. Oxidaton of As(lll) by
Aeration and Storage. EPA/600/R-01/102. United States
Environmental Protection Agency, National Risk Man-
agement Laboratory, Cincinnati, OH.
MacPhee, M.J. etal., 2001. Treatment of Arsenic Resid-
uals from Drinking Water Removal Processes. EPA/
600R-01/033. U.S. EPA, National Risk Management
Research Laboratory, OH.
Public Law (PL) 93-523. 1974. Safe Drinking Water Act.
Public Law (PL) 104-182. 1996. Safe Drinking Water Act
Amendments.
SAIC (Science Applications International Corporation),
2000. Regulations on the Disposal of Arsenic Residuals
from Drinking Water Treatment Plants. EPA/600/R-
00/025, United States Environmental Protection Agency,
National Risk Management Research Laboratory, OH.
Sorg, T.J., & Logsdon, G.S., 1978. Treatment Technol-
ogy to Meet the Interim Primary Drinking Water Regu-
lations for Inorganics: Part 2. J. AWWA, 70{7):379.
U.S. EPA, 1975. National Interim Primary Drinking Water
Regulations, Federal Register, 40:248.
U.S. EPA, 2000a. Proposed Arsenic Rule, Federal
Register, 40 CFR, Parts 141 and 142.
U.S. EPA, 2000b. Technologies and Costs for Removal
of Arsenic from Drinking Water. EPA 815-R-00-028.
Washington, DC.
U.S. EPA, 2001. National Primary Drinking Water Regu-
lations; Arsenic and Clarifications to Compliance and
New Source Contaminants Monitoring: Final Rule. 40
CFR, Parts 9, 141, and 142.
51
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U.S. EPA, 2003. Minor Clarification of the National Pri-
mary Drinking Water Regulation for Arsenic. Federal
Register, 40 CFR Part 141. March 25.
Wang, L. etal., 2002. Field Evaluation of As Removal by
IX and AA. J. AWWA, 94:3:161.
52
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Appendix A
Summary of Subsystem including Components
The items that are designated as "optional" are not man-
datory requirements. Some of those items may already
be included in systems other than treatment, and there-
fore would be redundant. Other items, though desirable,
are not mandatory. Automatic and semiautomatic opera-
tion is optional. Therefore, for each instrument and con-
trol item, though not indicated for clarity, there is an
automatic option.
For Schematic Flow Diagram, see Figure A-1.
1. Raw Water Influent Main
a. Flow control
b. Flowrate measurement, flow total
c. Preoxidation chemical injection for oxidation of
As(lll)toAs(V)
d. Excess preoxidation chemical removal
e. Pressure indicators
f. Pressure control (optional)
g. Backflow preventer
h. Sample before preoxidation chemical injection
piped to sample panel
i. Sample after preoxidation chemical injection
piped to sample panel
j. Sample after excess preoxidation chemical
removal piped to sample panel
k. Isolation valve
I. Temperature indicator
2. Intel-vessel Pipe Manifold
a. Process control valves
b. Pressure indicator
c. Sample piped to sample panel (optional)
d. pH sensor, conductor, alarm
e. Vessel 2 bypass valve
3. Treated Water Effluent Main
a. Process control valves
b. Chemical injection for pH adjustment(optional)
c. pH measurement, indicator, alarm and fail-safe
control
d. Sample after pH adjustment piped to sample
panel
e. Pressure indicator
f. Booster or repressurization pump (optional)
g. Disinfection injection (optional)
h. Isolation valve
4. Raw Water Bypass Main (optional)
a. .Flowcontrol
b. Flowrate measurement, flow total
c. Backflow preventer
d. Isolation valve
5. Backwash/Regeneration Feed Manifold
a. Process control valves
b. Isolation valves
c. Backflow preventers
d. Flow controls
e. Flowrate measurements, flow totals
f. Brine tank
g. Brine eductor
h. Brine injectors
i. Pressure indicators
j. Backflow preventers
k. Sample brine eductor piped to sample manifold
6. Wastewater Main
a. .Process control valves
b. Backflow preventers
c. Process isolation valves
d. Sight glass
e. Sample piped to sample panel
7. Treatment Vessels
a. Pressure vessel
b. Treatment media
c. Internal distribution and collection piping
d. Pressure relief valve
e. Air/vacuum valve
f. Operating platform and/or ladder (optional)
53
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54
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8.
9.
Sample Panel (optional)
a. Sample tubing from sample points with shut off
valves
b. Wet chemistry laboratory bench with equipment,
glassware, reagents, etc.
b.
c.
Softener Salt Storage and Feed Subsystem
a. Emergency shower and eyewash
Softener salt storage tank (optional)
i. Fill, discharge, and vent
ii. Level sensor (optional)
iii. Dust collection in vent
iv. Weather protection
Brine tank
i. Water fill pipe with float valve
ii. Softener salt feed pipe (optional)
iii. Drain valve
iv. Containment basin
10. Preoxidation Chemical Storage and Feed
Subsystem (optional)
a. Emergency shower and eye wash
b. Preoxidation chemical storage tank outside
treatment building (optional)
i. Fill, discharge, drain, vent, and overflow
piping
ii. Liquid level sensor (optional)
iii. Immersion heater with temperature control
iv. Weather protection
v. Containment basin (optional)
c. Preoxidation chemical day tank (inside treatment
building)
i. Fill line float valve
ii. Drain valve
iii. Containment basin (optional)
d. Preoxidation chemical piping (interconnecting
piping)
i. Between storage tank and day tank
ii. Between feed pump and, feedwater main
injection point
iii. Backflow prevention
11. Backwash Water Disposal System (optional)
a. Surge tank (optional)
b. Unlined evaporation pond (optional)
c. Sewer (optional)
d. Drainage ditch (optional)
e. Other discharge method (optional)
12. Toxic Regeneration Wastewater Disposal System
a. .Surge tank (optional)
b. Wastewater reclamation system (optional)
c. Other discharge method (optional)
55
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Appendix B
Treatment System Design Example
This design example is applicable to a specific manually
operated ion exchange arsenic removal water treatment
system. This example is applicable to any of the follow-
ing combinations of options:
1. Adjustment of EBCT
2. Adjustment of flowrate
3. Adjustment of arsenic concentration
4. Adjustment of raw water chemical analysis
5. Automatic operation in lieu of manual operation
Given:
q (flowrate) = 620 gpm
N (number of treatment trains) = 1
n (number of treatment vessels) = 3 (1 A, 1B and 2)
Treatment vessel designations
1A - Primary Stage - (operating)
1B - Primary Stage - (standby)
2 - Second Stage - (polishing)
Raw water arsenic concentration = 0.100 mg/L
(0.002 meq/L)
Raw water sulfate concentration = 34 mg/L
(0.68 meq/L)
Arsenic MCL = 0.010 mg/L
Treated water arsenic design concentration =
0.008 mg/L (max)
SBA resin manufacturer's published capacity =
1.016 eq/L (22,222 grains as CaCCVft3 or
50,930 g/m3)
SBA resin removal capacity* = 0.915 eq/L (20,000
grains as CaCCVft3 or 45,838 g/m3)
Salt consumption rate per regeneration = 10 Ib/ft3
EBCT = 3 min
Md (media density) = 42 Ib/ft3
h(treatment bed depth) = 4 ft
Mw = Md x v (media volume/vessel) * n (number of
treatment vessels)
Treatment flowrate = 10 gpm/ft2
Backwash flowrate = 4 gpm/ft2
Brine flowrate = % gpm/ft2
Pipe material - Type I Schedule 80 PVC, v (pipe
velocity) = 5 ft/second (max.)
p (system pressure): 50 psig (max.)
T (ambient temperature): 95°F (max.)
Tw (water temperature): 85°F (max.)
Vessel and Treatment Bed Design (reference: Fig-
ure 3-3)
Solve for: d (treatment bed diameter)
V (treatment bed volume)
Mw (total weight of treatment media)
D (vessel outside diameter)
H (vessel overall height)
When EBCT = 3 min, then flowrate = 21/2 gpm/ft3
media
Then, when q = 620 gpm; then
v= 620 gpm ft,
2.5 gpm/ft3
Then, when h = 4 ft,
A = V_=248ft3_
~ h ~ 4ft
Then,
= 62 ft2
Then, d = 8.89'=8'101/2"
Then, D = d + 1" = 8' 111/2", therefore use D = 9' 0"
t nno,
90% of manufacturer's theoretical capacity.
57
-------
Then,
Then, Mw = 3 x 250 ft3 x 42 Ib/ft3 = 31,500 Ib
Because the media quantity is almost a 40,000-lb
truckload, it is prudent to procure a truckload quan-
tity. That will provide an initial supply of makeup
media.
Then the treatment vessel dimensions are as fol-
lows:
48" + 44" + 4" + 2
108"
2. Pipe Sizing
Solve for: Sizes for water pipe mains
a. Raw and treated water mains:
q = 620 gpm (max)
Try 6", v = 7.0 ft/sec > 5 ft/sec, therefore NG
Try 8", v = 4.0 ft/sec > 5 ft/sec, therefore OK
Use 8" Schedule 80 PVC
b. Backwash pipe main:
q = 4 gpm/ft2 x 62 ft2 = 248 gpm
Try 4", v = 6.2 ft/sec, therefore NG
Try 6", v = 2.8 ft/sec, therefore OK
Use 6" Schedule 80 PVC
c. Brine (6% NaCI) pipe main:
q = 2 gpm/ft2 x 62 ft2 = 124 gpm
Try 3", v = 5.3 ft/sec, slightly over 5 ft/sec -
However low pressure, therefore OK
Use 3" Schedule 80 PVC
d. Concentrated brine (26% NaCI) pipe main
q = 0.2 x 2 gpm/ft2 x 62 ft2 = 25 gpm
Try 11/2P1, v = 4.0 ft/sec, therefore OK
Use 11/2" Schedule 80 PVC
Note: During backwash of one treatment bed, the
flowrate shall not exceed 250 gpm. Backwash
rate is not to exceed rate required for 100%
treatment bed expansion. This rate is sensitive
to raw water temperature.
3. Softener Salt System Design
a. Storage Tank Size
Storage tank size is based on logistical require-
ments which are a function of treatment plant
salt consumption rate and tank truck deliveries
of granular softener salt. The tank truck can
deliver up to 48,000 Ib of softener salt.
In this example, the design treatment flow is
620 gpm, and it is assumed that the salt con-
sumption is 1.33lb/1,000 gal treated water.
Then the salt consumption is 50 Ib/hr, and a
truckload would supply a minimum of 960 hours
of treatment operation.
A commercially available "brinemaker" includes
storage capacity for 72,000 Ib, which provides
capacity for 1% bulk tank truckloads of salt.
Therefore, when half a truckload is consumed,
there is a minimum of a 450-hour (18.75-day)
salt storage available before the salt supply is
exhausted. In practice, it could be two times that
minimum. The 36-ton storage capacity will easily
maintain operation while awaiting delivery.
b. Day Tank Size
The "brinemaker" includes brine production
(26% NaCI @ 40 gpm). A 1,200-gal brine day
tank will satisfy the NaCI requirement for
1,875,000 gal of treated water, which exceeds
the treatment flow for two days.
4. Regeneration Wastewater Surge Tank Design
Given:
Maximum volume of regeneration wastewater per
.cubic foot media = 150 gal/ft3
Number of cubic feet of media per regeneration =
250ft3
Tank construction - epoxy interior lined carbon steel
Find:
Volume of wastewater per regeneration = 150 gal/ft3
x 250 ft3 = 37,500 gal = 5,000 ft3
Dimensions of surge tank (use height = 16 ft)
Then,
(diameter)2 = 4x5-°00ft3=398 ft2
v ' Tt16ft
58
-------
Then, diameter = 20 ft
Then, tank dimensions = 20' (J> * 16' h
Preferred Containment Basin Dimensions: length
40', width 35', height 4', volume = 5,600 ft3 =
42,000 gal >37,500 gal
5. Annual Regeneration Requirements
To appropriately plan operational labor, cost, and
wastewater disposal requirements, the treatment
system design shall determine the number of treat-
ment vessel regenerations that will be required per
year. Due to variation in seasonal demand for
treated water, treatment cycle frequency increases
during high consumption and decreases during low
consumption periods. As described earlier in this
manual, the treatment system is designed to treat at
least 125% of the maximum consumption day. Dur-
ing low consumption periods the treated water
requirement might be one third (or less) of the maxi-
mum consumption day. For purposes of this exam-
ple, it is determined that the annual average utiliza-
tion is 50%. Therefore, the treatment plant shall pro-
duce treated water 50% of the time on an annual
basis.
Then, number of treatment vessel regenerations/
year equals:
q (gpm) x 1,440 (min/day) x 365 (day/year) x
average utilization x (As + SO4) (mg/L)
V (ft3) x 90% removal capacity (gr/gal) x
17.1(mg/L)/(gr/gal)
= 65
620 (gpm) x 1,440 (min/day) x 365 (day/year) x
0.50x34.1 (mg/L)
250 n3x 20,000 (gr/gal) x
17.1 (mg/L)/(gr/gal)
or calculated using meq/L units:
q (gpm) x 3,785 (L/gal) x 1,440 (min/day) x
365 (day/year) x average utilization x
(As+ SO4) (meq/L)
V (ft3) x 28.3 (L/ft3) x 90% removal capacity (eq/L) x
1,000(meq/eq)
620 gpm x 3,785 (L/gal) x 1,440 (min/day) x
365 (day/year) x 0.50 x 0.682 (meq/L)
250 (ft3 )x 28.3 (L/ft3 )x 0.915 (eq/L) x
1,000 (meq/eq)
= 65
These calculations do not include any regeneration
of the second stage treatment vessel. Any regenera-
tions required of the second stage treatment vessel
are in addition to the regeneration count of the first
stage treatment vessel.
59
-------
-------
Appendix C
Tabulations of Estimated Capital Cost Breakdowns for Arsenic Removal
Water Treatment Plants by Means of the Ion Exchange Process
at Typical and Ideal Locations
Contents
C-1. Tabulation of Estimated Capital Cost Breakdowns for Central Arsenic Removal Water Treatment Plants at
Typical Locations by Means of the Ion Exchange Process with Manual Operation
C-2. Tabulation of Estimated Capital Cost Breakdowns for Central Arsenic Removal Water Treatment Plants at
Typical Locations by Means of the Ion Exchange Process with Automatic Operation
C-3. Tabulation of Estimated Capital Cost Breakdowns for Central Arsenic Removal Water Treatment Plants at
Ideal Locations by Means of the Ion Exchange Process with Manual Operation
C-4. Tabulation of Estimated Capital Cost Breakdowns for Central Arsenic Removal Water Treatment Plants at
Ideal Locations by Means of the Ion Exchange Process with Automatic Operation
61
-------
Table C-1. Tabulation of Estimated Capita! Cost(a) Breakdowns for Central Arsenic Removal Water Treatment Plants
at Typical Locations by Means of the Ion Exchange Process with Manual Operation (Multiply by $1,000)
Treatment Flowrate (gpm)
Process Equipment
Treatment Vessels
Ion Exchange Resin
Process Piping, etc.
Instruments and Controls
Salt and Brine Storage
Subtotal
Process Equipment Installation
Mechanical
Electrical
Painting and Miscellaneous
Subtotal
Misc. Installed Items
Wastewater Surge Tank
Building and Concrete
Site Work and Miscellaneous
Subtotal
Contingency 10%
Total
65
41
22
17
8
3
91
28
7
6
41
14
41
12
67
_2fi
219
115
47
37
17
8
3
112
29
7
8
43
16
53
13
82
24
261
230
55
62
32
10
_§
164
34
8
11
53
22
53
14
89
31
337
330
63
79
34
11
5
192
36
9
Jl
57
34
64
16
114
36
399
480
87
96
34
11
5
233
36
9
12
57
46
64
16
126
42
458
555
95
117
41
12
_2Q
285
44
10
14
68
60
74
17
151
50
554
620
99
127
45
12
20
303
45
10
14
69
67
74
17
158
53
583
700
104
138
45
12
20
319
45
10
14
69
74
74
17
165
55
608
(a) August 2001 prices.
Note: Engineering, exterior utility pipe and conduit, wastewater and waste solids processing system, finance charges, real estate cost and taxes
not included.
Table C-2. Tabulation of Estimated Capital Cost(a) Breakdowns for Central Arsenic Removal Water Treatment Plants
at Typical Locations by Means of the Ion Exchange Process with Automatic Operation
(Multiply by $1,000)
Treatment Flowrate (gpm)
Process Equipment
Treatment Vessels
Ion Exchange Resin
Process Piping, etc.
Instruments and Controls
Salt and Brine Storage
Subtotal
Process Equipment Installation
Mechanical
Electrical
Painting and Miscellaneous
Subtotal
Misc. Installed Items
Wastewater Surge Tank
Building and Concrete
Site Work and Miscellaneous
Subtotal
Contingency 10%
Total
(a) August 2001 prices.
65
44
22
42
57
3
168
31
29
7
67
14
41
_12
67
_2Q
332
115
47
37
43
60
4
191
32
30
_S
70
16
53
_ia
82
_34
377
230
55
62
70
68
_5
260
37
32
_u
80
22
53
14
89
_42
472
330
63
79
74
72
5
293
40
33
12
85
34
64
_1S
113
_42
540
Note: Engineering, exterior utility pipe and conduit, wastewater and waste solids processing system,
not included.
480
87
96
74
72
_§
334
40
35
_aa
87
46
64
-Ifi
126
_5§
602
555
95
117
82
73
20
387
49
40
14
103
60
74
17
151
_M
705
finance charges,
620
99
127
88
73
^a
407
50
40
14
104
67
74
17
158
_§2
736
700
104
138
88
73
_2Q
423
50
40
_14
104
74
74
_1Z
165
_SZ
761
real estate cost and taxes
62
-------
Table C-3. Tabulation of Estimated Capital Cost(a> Breakdowns for Central Arsenic Removal Water Treatment Plants
at Ideal Locations by Means of the Ion Exchange Process with Manual Operation (Multiply by $1,000)
Treatment Flowrate (gpm)
Process Equipment
Treatment Vessels
Ion Exchange Resin
Process Piping, etc.
Instruments and Controls
Salt and Brine Storage
Subtotal
Process Equipment Installation
Mechanical
Electrical
Painting and Miscellaneous
Subtotal
Misc. Installed Items
Wastewater Surge Tank
Building and Concrete
Site Work and Miscellaneous
Subtotal
Contingency 10%
Total
65
41
22
17
B
3
91
25
3
5
33
0
4
0
4
13
141
115
47
37
17
8
3
112
26
3
6
35
0
4
0
4
15
166
230
55
62
32
10
5
164
31
4
7
42
0
5
0
5
21
232
330
63
79
34
11
5
192
33
5
10
48
0
5
0
5
25
270
480
87
96
34
11
5
233
33
5
10
48
0
5
0
5
29
315
555
95
117
41
12
6
271
41
6
12
59
0
6
0
6
34
370
620
99
127
45
12
6
289
42
6
_aa
60
0
6
0
6
36
391
700
104
138
45
12
6
305
43
6
12
61
0
6
0
6
37
409
(a) August 2001 prices.
Note: Engineering, exterior utility pipe and conduit, wastewater and waste solids processing system, finance charges, real estate cost and taxes
not included.
Table C-4. Tabulation of Estimated Capital Cost(a) Breakdowns for Centra! Arsenic Removal Water Treatment Plants
at Ideal Locations by Means of the Ion Exchange Process with Automatic Operation (Multiply by $1,000)
Treatment Flowrate {gpm)
Process Equipment
Treatment Vessels
Ion Exchange Resin
Process Piping, etc.
Instruments and Controls
Salt and Brine Storage
Subtotal
Process Equipment Installation
Mechanical
Electrical
Painting and Miscellaneous
Subtotal
Misc. Installed Items
Wastewater Surge Tank
Building and Concrete
Site Work and Miscellaneous
Subtotal
Contingency 10%
Total
65
41
22
42
57
3
165
31
34
5
70
0
4
0
4
24
263
115
47
37
43
60
4
191
32
35
6
73
0
4
0
4
27
295
230
55
62
72
68
5
262
37
37
7
81
0
5
0
5
35
383
330
63
79
74
72
5
293
40
38
10
88
0
5
0
5
39
425
480
87
96
74
72
5
334
40
40
10
90
0
5
0
5
43
472
555
95
117
82
73
6
373
49
45
12
106
0
6
0
6
49
534
620
99
127
88
73
6
393
50
45
12
107
0
6
0
6
51
557
700
104
138
88
73
6
409
50
45
12
107
0
6
0
6
52
574
(a) August 2001 prices.
Note: Engineering, exterior utility pipe and conduit, wastewater and waste solids processing system, finance charges, real estate cost and taxes
not included.
63
-------
Appendix D
English to Metric Conversion Table
English
inches (in)
square inches (in2)
cubic inches (in3)
feet (ft)
square feet (ft2)
cubic feet (ft3)
cubic feet (ft3)
cubic feet (ft3)
equivalents/liter (eq/L)
gallons (gal)
gallons (gal)
gallons (gal)
grains (gr)
grains (gr)
grains/ft3
Kgrains as CaCCVft3
pounds (Ib)
Ib/in2 (psi)
Ib/ft2 (psf)
c/1,000(gal)
Multiply by
0.0254
0.000645
0.000016
0.3048
0.0929
0.0283
28.3
7.48
21.8
3.785
0.0038
0.0038
64.8
0.0649
2.2919
0.0458
0.4545
0.00689
4.8922
0.2642
Metric
meter (m)
m2
m3
m
m2
m3
liters (L)
gal
Kgrains as CaCOa/ft3
liters (L)
kiloliter (kl_)
m3
mg
grams (g)
g/m3
eq/L
kilograms (kg)
megapascals (MP)
kg/m2
c/1,0001
64
-------
-------
-------
-------
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Environmental Protection
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Research Laboratory
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