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)

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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

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             « 1,000
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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

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                                       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

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 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

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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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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

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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

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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

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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

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                     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)

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                          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

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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

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    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

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   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

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                                     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

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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

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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

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          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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