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.



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 fimits), 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

29

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
of TDS. If the regulatory agency permits disposal of
the supernatant by conventional methods (surface dis-
charge, percolation), the disposai costs are not large.

The total volume of wastewater is normally less than
150 gal/ft® 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
tesin. For example, if the resin capacity is 1.28 eq/L
(28 Kgrains as CaCOs per ft*) 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/ft®. Con-
versely, if the resin capacity is 0.67 eq/L. (15 Kgrains as
CaCO; per ft’) 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 gal/ft®. 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 (NaCl) 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 Jess 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.



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Material Total Labor Unit
Unit Price® Material Price” Total Labor Total
item Qty (%) ($) ($) ($) ()
8" SCH 80 PVC Pipe (P/E) 380 ft 8.00/ft 3,040 5.00/ft 1,900 4,940
6" SCH 80 PVC Pipe (P/E) 170 ft 5.00/t 850 4.00/ft 680 1,530
4" SCH 80 PVC Pipe (P/E) 90 ft 3.50/ft 270 3.00/ft 270 540
1%" SCH 80 PVC Pipe (P/E) 30 ft 1.00/f 30 2.00/ft 60 90
8" SCH 80 PVC Tee (s * s x 8) 24 170 ea. 4,080 15.00 ea. 360 4,440
6" SCH 80 PVC Tee (s x s xs) 6 70 ea. 420 15.00 ea. 90 510
4" SCH 80 PVC Tee (s x s x 8) 5 50 ea. 250 10.00 ea. 50 300
8" SCH 80 PVC 90° ELL (s * s) 19 120 ea. 2,280 12.50 ea. 240 2,520
6" SCH 80 PVC 90° ELL (s x s) 5 45 ea. 225 12.50 ea. 65 290
4" SCH 80 PVC 90° ELL (s * s) 8 20 ea. 160 10.00 ea. 80 240
1%" SCH 80 PVC 90° ELL (s * s) 8 5 ea. 40 7.50 ea. 60 100
8" SCH 80 PVC Reducer (s * s) 8 70 ea. 560 12.50 ea. 100 660
6" SCH 80 PVC Reducer (s * s) 2 30 ea. 60 12.50 ea. 25 85
4" SCH 80 PVC Reducer (s x s) 1 25 ea. 25 10.00 ea. 10 35
8" SCH 80 PVC Coupling (s  s) 5 45 ea. 225 12.50 ea. 65 290
6” SCH 80 PVC Coupling (s  s) 5 35 ea. 175 12.50 ea. 65 240
4" SCH 80 PVC Coupling (s x s) 4 20 ea. 80 12.50 ea. 50 130
1%" SCH 80 PVC Coupling (s * s) 2 5 ea. 10 10.00 ea. 20 30
8" SCH 80 PVC Van Stone Flange (s) 62 55 ea. 3,410 12.50 ea. 775 4,185
6" SCH 80 PVC Van Stone Flange (s) 16 35 ea. 560 12.50 ea. 200 760
4" SCH 80 PVC Van Stone Flange (s) 19 20 ea. 380 10.00 ea. 190 570
8" Wafer Style PVC Butterfly Valve 14 280 ea. 3,920 50.00 ea. 700 4,620
6" Wafer Style PVC Butterfly Valve 8 225 ea. 1,800 40.00 ea. 320 2,120
4" Wafer Style PVC Butterfly Valve 7 180 ea. 1,260 25.00 ea. 175 1,435,
1%" PVC Ball Valve (s * s) 2 60 ea. 120 25.00 ea. 50 170
8" PVC Wafer Style Check Valve 3 650 ea. 1,850 100.00 ea. _300 2,150
TOTALS 26,080 6,900 32,980°

(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



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:

90

UO2(CO3)3* > SO,? > HAsO, > NOs" >
SeO,;* > NO, > CI? > HCOs* > F

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

Breakthrough i
Arsenic “Dumping" |

|

a Q N @
oO o (=) o
i 1 1 1

Arsenic concentration - ug/L
>
Oo
1

4 Raw Water

= = Effluent from storage tank
following ion exchange system

System
regenerated

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)



Table C-1. Tabulation of Estimated Capita! Cost Breakdowns for Central Arsenic Removal Water Treatment Plants
at Typical Locations by Means of the lon Exchange Process with Manual Operation (Multiply by $1,000)

Treatment Flowrate (gpm) 85 115 230 330 480 555 620 700

Process Equipment
Treatment Vessels 4t 47 55 63 87 95 99 104
lon Exchange Resin 22 37 62 79 96 117 127 138
Process Piping, etc. 17 17 32 34 Kod 4 45 45
Instruments and Controls 8 8 10 11 1 12 12 12
Salt and Brine Storage 3 _3 si —5 —5 20 20 20
Subtotal 91 112 164 192 233 285 303 319

Process Equipment Installation

Mechanical 28 29 34 36 36 44 45 45
Electrical 7 7 8 9 9 10 10 10
Painting and Miscellaneous 6 _8 11 12 12 14 14 14
Subtotal 4 43 53 57 87 68 69 69

Misc. installed Items
Wastewater Surge Tank 14 16 22 34 46 60 67 74
Building and Concrete 4 53 53 64 64 74 74 74
Site Work and Miscellaneous 12 13 14 16 16 iz 17 12
Subtotal 67 82 89 114 126 151 158 165
Contingency 10% 20 ~24 <3 36 42 50 -53 55
Total 219 261 337 399 458 554 $83 608

(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 Breakdowns for Central Arsenic Removal Water Treatment Plants
at Typical Locations by Means of the lon Exchange Process with Automatic Operation
(Muitiply by $1,000)

Treatment Flowrate (gpm) 65 115 230 330 480 555 620 700
Process Equipment
Treatment Vessels 44 47 55 63 87 95 99 104
jon Exchange Resin 22 7 62 79 96 117 127 438
Process Piping, etc. 42 43 70 74 74 82 88 88
Instruments and Controls 57 60 68 72 72 73 73 73
Salt. and Brine Storage —3 —4 —_ 2 —5 20 -20 -20
Subtotal 168 191 260 293 334 387 407 423
Process Equipment Installation
Mechanical i] 32 7 40 40 Ag 50 50
Electrical 29 30 32 33 35 40 40 40
Painting and Miscellaneous Zz _8 = 12 12 14 14 44
Subtotal 67 70 80 85 87 103 104 104
Misc. Installed Items.
Wastewater Surge Tank 14 16 22 34 46 60 67 74
Building and Concrete 41 53 53 64 64 74 74 74
‘Site Work and Miscellaneous 12 13 14 15 16 17 17 17
Subtotal 67 82 89 113 126 151 158 165
Contingency 10% 30 ~34 43 49 —55 84 — 82
Total 332 377 472 540. 602 705 736 761

(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.

62



ARS! REM WATER TREATMENT PLANT
OPERATION LOG

Unit # Run # Date Start Date End

REATMENT TO RESERVOIR
Meter End Meter Start Total Treated

BYPASS TO RESERVOIR
Meter End Meter Start Total Treated

BACKWASH TO WASTE
Meter End Meter Start Total

REGENERATION TO WASTE
Meter End Meter Start Total

SLOW RINSE TO WA‘
Meter End Meter Start Total

FAST RINSE TO WASTE
Meter End Meter Start Total

TOTAL WASTEWATER SUMMARY
Total to Tank k-gal PERCENT WASTE

TREATED WATER LOG

Treatment Treated y As
Meter 4 Meter | Raw As As removed

(k-gal) (k-gal) (mg/L) (mg/L) (mg)

Figure 5-4. Arsenic Removal Water Treatment Plant Operation Log

44



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/ft’, the resulting fast

rinse flow volume is 270 gal/it? 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,

Table 5-3. Typical Regeneration Process

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 ail, 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 yig/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

Time

Step Flow Rate (Minutes or Wastewater
No. Step Liquid Direction (gpmift? or as noted) Bed Volume) (gal/tt*)
1 Backwash Raw water Upflow 3-4 5-20 min 20
2 — Regeneration — 6-10% NaC! Downflow 0.5 gpm/tt* 40 min 20
3 Slow rinse Raw water Downflow 2 40 min 20
4 Fast rinse Raw water Downflow 10 9 BV 70
Total 130

(a) Resin manufacturer should be consulted on specific regeneration requirements.

42



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 manhours per year = 2,000/man

48

Manual Automatic

Then: Qperation _Operation
Number of hours on

regeneration/year 65 « 4 hr = 260 hr Ohr
Number of hours on routine

operation/year (365-65) x 1 = 300hr 365 hr
Number of hours on extra

tasks 50 x 2 hr = 100hr 100hr
Total plant operator time = 660hr 465 hr
Operator hourly rate:

$30,000/2,000 hr = $15.00/hr
30% (overhead and fringe

benefits) = $ 4.50/hr
Operator rate $19.50/hr $22.00/hr

Total manual operation operator cost:
660 hr x $19.50/hr = $12,870

Total automatic operation operator cost:
465 hr x $22/hr = $10,230

Total gallons water produced:
0.5 (50% utilization) (620 gpm) * 1,440 min/day «
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


U.S. EPA, 2003. Minor Clarification of the National Pri- | Wang, L. et al., 2002. Field Evaluation of As Removal by
mary Drinking Water Regulation for Arsenic. Federal IX and AA. J. AWWA, 94:3:161.
Register, 40 CFR Part 141. March 25.

52



Bed Volume of Treated Water

80: 100 120

Sulfate Concentration - mg/L

[=e=0.8 eqit Resin Capacity —a— 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.
Flow wall effects.

Uneven flow conditions that distort the treatment
wave front.

Defective resin beads.

Uneven feedwater distribution and/or treated water
collection subsystems characteristics due to treat-
ment vessel internal piping design/manufacture/
assembly (including dead areas).

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



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.
lon 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.

12

3.2.1 Manual Operation

In manual operation, the treatment plant operator person-
ally performs ail 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.

Valves with manual handle, lever, handwheel, or
chainwheel operators.

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



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
NaCl requirement varies with the ion exchange resin
selected, but 10 Ib/ft® 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. All 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.



Appendix C

Tabulations of Estimated Capital Cost Breakdowns for Arsenic Removal

C-2.

C-3.

C-4.

Water Treatment Plants by Means of the lon Exchange Process
at Typical and Ideal Locations

Contents

Tabulation of Estimated Capital Cost Breakdowns for Central Arsenic Removal Water Treatment Plants at
Typical Locations by Means of the lon Exchange Process with Manual Operation

Tabulation of Estimated Capital Cost Breakdowns for Central Arsenic Removal Water Treatment Plants at
Typical Locations by Means of the lon Exchange Process with Automatic Operation

Tabulation of Estimated Capital Cost Breakdowns for Central Arsenic Removal Water Treatment Plants at
Ideal Locations by Means of the lon Exchange Process with Manual Operation

Tabulation of Estimated Capital Cost Breakdowns for Central Arsenic Removal Water Treatment Plants at
Ideal Locations by Means of the lon Exchange Process with Automatic Operation

61



Foreword

The U.S. Environmental Protection Agency (EPA) is charged by Congress with pro-
tecting the Nation's and, air, and water resources. Under a mandate of national envi-
tonmental 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

iti



Appendix D

English to Metric Conversion Table

English Multiply by Metric
inches (in) 0.0254 meter (m)
square inches (in?) 0.000645 = m*
cubic inches (in°) 0.000016 = m*
feet (ft) 0.3048 m
square feet (ft) 0.0929 m?
cubic feet (ft°) 0.0283 m
cubic feet (ft*) 28.3 liters (L)
cubic feet (ff°) 7.48 gal
equivalents/liter (eq/L) 21.8 Kgrains as CaCO,/ft®
gallons (gal) 3.785 liters (L)
gallons (gal) 0.0038 kiloliter (kL)
gallons (gal) 0.0038 m
grains (gr) 64.8 mg
grains (gr) 0.0649 grams (g)
grains/ft® 2.2919 gim®
Kgrains as CaCOyft® 0.0458 eq/L
pounds (lb) 0.4545 kilograms (kg)
Ib/in? (psi) 0.00689 megapascals (MP)
lb/ft? (psf) 4,8922 kgim?
¢/1,000 (gal) 0.2642 /1,000 L

64



Table C-3. Tabulation of Estimated Capital Cost Breakdowns for Central Arsenic Removal Water Treatment Plants
at Ideal Locations by Means of the lon Exchange Process with Manual Operation (Multiply by $1,000)

Treatment Flowrate (gpm) 65 415 230 330 480 555 620 700

Process Equipment
Treatment Vessels 44 47 55 63 87 95 99 104
lon Exchange Resin 22 37 62 79 96 117 127 138
Process Piping, etc. 17 17 32 34 34 44 45 45
Instruments and Controls 8 8 10 11 "1 12 12 12
Salt and Brine Storage 3 _3 _5 5 _5 _6 _6 _6
Subtotal 91 112 164 192 233 271 289 305

Process Equipment Installation

Mechanical 25 26 31 33 33 4 42 43
Electrical 3 3 4 5 5 6 6 6
Painting and Miscellaneous _5 _6 _2 10 10 42 42 42
Subtotal 33 35 42 48 48 59 60 61

Misc. Installed Items
Wastewater Surge Tank 0 0 0 0 0 0 oO 0
Building and Concrete 4 4 5 5 5 6 6 6
Site Work and Miscellaneous _0 _0 _o _0 _o _o _o _o
Subtotal 4 4 5 § 5 6 6 6
Contingency 10% 13 15 21 25 29 34 36 37
Total 141 166 232 270 315 370 391 409

(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 Breakdowns for Central Arsenic Removal Water Treatment Plants
at Ideal Locations by Means of the lon Exchange Process with Automatic Operation (Multiply by $1,000)

Treatment Flowrate (gpm) 65 416 230 330 480 555 620 700

Process Equipment
Treatment Vessels 4 47 55 63 87 95 99 104
lon Exchange Resin 22 37 62 79 96 117 127 138
Process Piping, etc. 42 43 72 74 74 82 88 88
Instruments and Controls 57 60 68 72 72 73 73 73
Salt and Brine Storage 3 —_4 —5 5 —5 _6 6 _6
Subtotal 165 191 262 293 334 373 393 409

Process Equipment Installation

Mechanical 31 32 37 40 40 49 50 50
Electrical 34 35 37 38 40 45 45 45
Painting and Miscellaneous 8 —& 7 10 19 12 12 12
Subtotal 70 73 81 88 90 106 107 107

Misc. Installed Items
Wastewater Surge Tank 0 o 0 0 0 0 O O
Building and Concrete 4 4 5 5 5 6 6 6
Site Work and Miscellaneous 2 mY 2 oO zm 2 a) 2
Subtotal 4 4 5 5 5 6 6 6
Contingency 10% 24 <2 38 -39 43 4g 1 52
Total 263 295 383 425 472 534 557 574

(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





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 tabor 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:

Raw water influent main.

Intervessel pipe manifold.

Treated water effluent main.

Raw water bypass main.
Backwash/regeneration feed manifold.
Wastewater main.

Sample panel (optional).

NOORONs

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.

23

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/1g/60Hz 20-amp duplex receptacle,
and laboratory equipment/glassware/reagents for analy-
sis of pH, arsenic, sulfate, and other ions. A deionized
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/f® 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
Teinforced 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
fevel sensor, a liquid level controller, and a side-entry
mixer.



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(iIl) cannot be removed by ion
exchange SBA resin, all As(III) in the source water must
be preoxidized to As(V) to accomplish maximum arsenic
removal.

As(lil) 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(IIl) 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(iII).
Air oxidation that is effective for oxidizing iron has been
found to be ineffective for As(IIl) 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



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(III)
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(Ill), 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-

15

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 (upftow). 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 (NaCl) 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 gpmitt’. The data presented in this
design manual is based on a flowrate of 10 gpmitt?
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
tesins. 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/ft? 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.



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(Ill) 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 flowrate than the maximum
daily flowrate requirement), it should be resized to
deliver slightly more (i.e., 125% minimum) than the peak
requirement. The flowrate 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
flowrate for an oversized pump can result in excessive
equipment wear and energy costs. The treatment media
volume is a function of flowrate. The treatment vessels,
pipe sizes, and chemical feedrates aif increase as the
flowrate 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
42 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

11

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) STD 61.

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,
atrangement, 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.



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

24

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.



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 NaCl
brine.

8. Spent regenerant may be reusable.

The disadvantages of the ion exchange process are as
follows:

1. The process does not remove As(IIl). When present,
As(Ill) 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 CO; 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.

al

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.

cd

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
lower 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





Table 6-1. Operating Cost Tabulation

Dollars/1,000 gel Treated

Water

Manual Automatic
Operating Cost Items Operation Operation
Flowrate: 620 gpm ($) (8)
Treatment Chemicais 0.047 0.047
Operating Labor 0.08 0.06
Utility 0.01 0.01
Replacement lon Exchange Resin 0.15 0.15
Replacement Part and Misc. 0.02, 0.02

Material

TOTAL 0.30 0.28

(a) Wastewater and waste solids, processing and disposal not
included.
(b) Cost to oxidize As(III) to As(V) not included.

50


Table 3-1.

Table 3-2.

Table 4-1.

Table 5-1.

Table 5-2.

Table 5-3.
Table 6-1.

Tables

Preliminary Capital Cost Estimate Examples for Two Types of lon
Exchange Arsenic Removal Water Treatment Plants at a Typical

Final Capital Cost Estimate Examples for Two Types of lon
Exchange Arsenic Removal Water Treatment Plants at a Typical
Location.

Final Capit pl yp

Exchange Arsenic Removal Water Treatment Plants at an Ideal

Valve Operation Chart for Treatment Vessels in Treatment and
Regeneration Operational Modes we sceeeneeneen
Typical Manufacturer's Downflow Pre:

Typical Regeneration Process.

Operating Cost Tabulation...



Table 3-2. Final Capital Cost Estimate Examples for Two Types of lon Exchange Arsenic Removal Water Treatment

Plants at a Typical Location

Locatic

Flowrate: 620 gpm Cost ($1,000)

Date: Manual Automatic

Operation Operation

Process Equipment

Treatment Vessels 98 99

lon Exchange Resin (750 ft?) 127 127

Process Piping, Valves, and Accessories 45 88

Instruments and Controls 12 73

Salt and Brine Storage 20 —20
Subtotal 303 407

Process Equipment installation

Mechanical 45 50

Electrical 10 40

Painting and Misceltaneous 4 14
‘Subtotal 69 104

Miscellaneous Installed items

Regeneration Wastewater Surge Tank 67 67

Building and Concrete 74 74

Site Work, Fence, and Miscellaneous 17 17
Subtotal 158 188

Contingency 10% 53 87

Total® 583 736

(a) Engineering, exterior utility pipe and conduit, wastewater and waste solids processing
system, finance charges, real estate cost, and taxes not included.

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).

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

21

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 hydrostatically 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.



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:

APON>

Adjustment of EBCT

Adjustment of flowrate

Adjustment of arsenic concentration
Adjustment of raw water chemical analysis
Automatic operation in lieu of manual operation

Given:

q (flowrate) = 620 gpm

N (number of treatment trains) = 1

n (number of treatment vessels) = 3 (1A, 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 CaCO,/fit* or
50,930 g/m”)

SBA resin removal capacity* = 0.915 eq/L (20,000
grains as CaCO,/ft? or 45,838 g/m*)

Salt consumption rate per regeneration = 10 Ibift®

EBCT = 3 min

Ma (media density) = 42 Ib/ft®

h(treatment bed depth) = 4 ft

My, = Mg x V (media volume/vessel) * n (number of
treatment vessels)

Treatment flowrate = 10 gpm/ft?

Backwash flowrate = 4 gpm/ft?

+ 90% of manufacturer's theoretical capacity.

57

Brine flowrate = % gpm/ft?

Pipe material - Type | Schedule 80 PVC, v (pipe
velocity) = 5 ft/second (max.)

p (system pressure): 50 psig (max.)

T (ambient temperature): 95°F (max.)

Ty (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)
My (total weight of treatment media)
D (vessel outside diameter)
H (vessel overall height)

When EBCT = 3 min, then flowrate = 2% gpm/ft®
media

Then, when q = 620 gpm; then

= 8209PM__ 44 43
2.5 gpmift®
Then, when h = 4 ft,
3
na = 248 _ go 42
h 4ft
Then,
2
d? = 4A _ 4x62 ft" _ 78 94 ft?
TM w

Then, d = 8.89' = 8' 10%"

Then, D=d + 1" = 8' 11%", therefore use D = 9' 0"



Then, diameter = 20 ft
Then, tank dimensions = 20' o « 16'h

Preferred Containment Basin Dimensions: length
40', width 35’, height 4’, volume = 5,600 f=
42,000 gal >37,500 gal

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 shail pro-
duce treated water 50% of the time on an annual
basis.

Then, number of treatment vessel regenerations/
year equals:

59

g(gpm) x 1,440 (min/day) x 365 (day/year) x
average utilization x (As + SO, ){mg/L)
V (ft?) x 90% removal capacity (gr/gal) x
17.1(mg/L)/(gr/gal)

620 (gpm) x 1,440 (min/day) x 365 (day/year) x
0.50 x 34.1 (mg/L)
250 ft® x 20,000 (gr/gal) x
17.1 (mg/L)/(gr/gal)

=65

or calculated using meq/L units:

q (gpm) x 3,785 (Ligal) x 1,440 (min/day) x
365 (day/year) x average utilization x
(As + SO, )(meq/L)
V (it?) x 28.3 (Lift?) x 90% removal capacity (eq/L) x
1,000 (meq/eq)

620 gpm x 3,785 (Ligal) x 1,440 (min/day) x
365 (day/year) x 0.50 x 0.682 (meq/L)
250 (ft°) x 28.3 (Lift) 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.





As stated above, 3min is the EBCT (2.5 gpm/t’)
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/ft®
(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 vessei 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% NaCl solution, system pressure,

18

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 contro! 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:

Instrument " Range = Accuracy
1. Flow sensor Varies £2%
{indicator/totalizer)
2. Pressure indicator Varies £1%
3. pH sensor/analyzer/alarm 0-14 £0.1
4. Level sensor/indicator Varies £1%
5. Temperature indicator 30-120°F t1%

(optional)

(a) Range to be compatible with application, maximum measurement
not to exceed 90% of range.



Contents

Foreword
Abstract .
Figures
Tables.
Abbrevi:
Acknowledgments

1.1
Background .
Arsenic in Wat
Arsenic Speciation.
Removal of Arsenic

pass
aaownr

2.0 Arsenic Removal by lon Exchange Treatment.
2.1 Introduction...

2.2 lon Exchange Proces:
2.2.1 Effect of Sulfate on Arse!

2.2.2 Effect of Multiple Contaminants......

2.2.3 Low Effluent pH in the Early Stages of a Treatment Cycle

2.2.4 Spent Brine Reuse .

2.3 Manual vs. Automatic Operation

3.0 Design of Central Treatment System
3.1 Assemble Design Input Data and Information.
3.2 Conceptual Design...

3.2.1. Manual Operation...

3.2.2 Automatic Operation

3.2.3 Semiautomatic Operatio

3.3 Preliminary Design ...

3.3.1 Treatment Equipment Preliminary Design.

3.3.1.1 Treatment Bed and Vessel Design.

3.3.1.2 Pipe Design ........

3.3.1.3 Instrumentation Desig!

3.3.1.4 Salt (NaCl) Storage and Feed Subsystem

3.3.2 Preliminary Treatment Equipment Arrangement.
3.3.3 Preliminary Cost Estimate

3.3.4 Preliminary Design Revision:

3.4 Final Design...:........ weve 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 .

3.4.1.3 Instrument Desig 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 ..



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(IIl) occurs as an uncharged
anion in ground water in the pH range of 6.5 to 8, the process will not remove As(III)
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 tower 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.



5 1,000

> «800

3

£ 600

3 400

i

2

8 200

3 i
o oO +

0 50 100 150 200

250

Sulfate Concentration - mg/L

[ee Resina

—m Resin B

—t-Resinc |

Figure 2-1.

Treatment Runs (Experimental) to Arsenic Breakthrough with Varying Sulfate

Concentrations in Raw Water (Ghurye et al., 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
tesins prefer divalent (e.g., carbonate) to monovatent
(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 (NaCl) 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:



7.0 REfCTENCES ........eccssccssessseessutesseesssecsseesercsssessseessvecssesssessereesnecnuessiessieesneesnesnetanees 54

Appendix A:
Appendix B:
Appendix C:

Appendix D:

Figure 1-1.

Figure 1-2.
Figure 2-1.

Figure 3-1.
Figure 3-2.
Figure 3-3.
Figure 3-4.
Figure 3-5.
Figure 4-1.
Figure 4-2.
Figure 4-3.
Figure 4-4.
Figure 4-5.
Figure 5-1.
Figure 5-2.
Figure 5-3.

Figure 5-4.

Summary of Subsystem Including Components
Treatment System Design Example
Tabulations of Estimated Capital Cost Breakdowns for Arsenic
Removal Water Treatment Plants by Means of the lon Exchange
Process at Typical and Ideal Locations
English to Metric Conversion Table .

Figures

Arsenic Breakthrough Results of Full-Scale Arsenic Removal
Anion Exchange System
Examples of Arsenic Removal lon Exchange System Designs.
Treatment Runs (Experimental) to Arsenic Breakthrough with
Varying Sulfate Concentrations in Raw Water.
Water Analysis Report .............:css00
lon Exchange Treatment System Flow Diagram
Treatment Bed and Vessel Design Calculations
Treatment System Plan
Treatment Vessels Piping
Capital Cost vs. Flowrate at Typical Locations for Arsenic
Removal Water Treatment Plants by Means of the lon Exchange
Process
Capital Cost vs. Flowrate at Ideal Locations for Arsenic Removal

Water Treatment Plants by Means of the lon Exchange Process........ 31
Code Pressure Vessel Fabricator Quotation for lon Exchange
Treatment Vessels see
Example of SBA Resin Quotation for Arsenic Removal Drinking
Water Treatment Systems Provided by Prominent Manufacturer .
Process Pipe, Fittings, and Vaives: Itemized Cost Estimate for a
Manually Operated 620-gpm Arsenic Removal Water Treatment
System
Valve Number Diagram
Basic Operating Mode Flow Schematics .
Resin Removal Capacity Based on Sulfa
Resin Capacity
Arsenic Removal Water Treatment Plant Operation Log.

vii



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36



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



ANSI
APHA
ASME
AWWA

BAT
BV

CPVC

EBCT
EPDM
ETV

FRP

GFAA
GHAA
gpd
gpm
ICP-MS
MCL

N/A
NPT
NSF

O&M
OSHA

PL
PLC
psi
psig
PVC
SBA
SDWA
STP

TCLP
TDS

U.S. EPA

WEF

Abbreviations and Acronyms

American National Standards Institute
American Public Health Association
American Society of Mechanical Engineers
American Water Works Association

best available technology
bed volume(s)

chlorinated polyvinyl chloride

empty bed contact time
ethylene propylene diene monomer
Environmental Technology Verification

fiberglass reinforced polyester

graphite furnace atomic absorption
gaseous hydroxide atomic absorption
gallons per day

gallons per minute

inductively coupled plasma—mass spectrometry
maximum contaminant level

not applicable
National Pipe Thread
NSF International

operations and maintenance
Occupational Safety and Health Administration

Public Law

programmable logic controller
pounds per square inch
pounds per square inch gage
polyvinyl chioride

strong-base anion
Safe Drinking Water Act (of 1974)
stabilized temperature platform

Toxicity Characteristic Leaching Procedure
total dissolved solids

United States Environmental Protection Agency

Water Environment Federation



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:

41. 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 $0.20/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 lon 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 ioss of resin. Monitoring the backwash
water will detect and provide protection from that occur-
tence. 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

49

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-ft* beds
are used, the attrition in the polishing vessel should be
zero.

The cost of replacement resin is as follows:

Cost = Number of beds x volume of resin/bed * resin
cost x 20% = 2 x 250 ft x $165/ft* x 0.20 = $16,500

Then, the ion exchange replacement cost = $16,500/
463,000 (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/ft°; quotations for
less than truck quantities range up to $300/ft°. For cost
estimating purposes in this design manual, the $165/f°
cost is used for the largest systems and graduates up to
$300/ft® 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.



CODE PRESSURE VESSEL FABRICATOR QUOTATION
FOR ION EXCHANGE TREATMENT VESSELS (three required)

Vessel! Specification and Quotation #1280m 07/24/01
Customer

Attention

R.F.Q. Pricing for your Arsenic Removal Water Treatment Project

Description Vertical Skid-Mounted Vessel

Size 120" O.D. x 8' 0" S/S; Capy, 5,450 gal

Design Pressure and Temp 50 psig @ 175 degrees Fahrenheit

Corrosion Allowance None requested or provided

Design Criteria A.S.M.E. Section VII, Div. 1

Radiography Spot (RT-3)

Code Stamp Yes and National Board Registration

Constructed of Carbon steel

Supports (4) carbon steel legs with skid to provide 24" to bottom seam

Nozzles and Appurtenances:

2 20" quick opening manways
4" -CL150 FF single-tapped pad flange, hillside-type
4” - CL150 FF single-tapped pad flange
8" - CL150 FF single-tapped pad flanges
12" x 3" vertical viewing window
False bottom
Interior carbon steel lateral support clips
Interior carbon steel header support clip
Exterior pipe support brackets
Lifting lugs
Skid

1
1
2
1
1
8
1
ts
2
1

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 lon Exchange Treatment Vessels



Table 3-1. Preliminary Capital Cost Estimate Examples for Two Types of lon Exchange Arsenic Removal Water

Treatment Plants at a Typical Location

Location:
Flowrate: 620 gpm
Date:

Cost ($1,000)

Automatic
Operation

Manual
Operation

Process Equipment

Treatment Vessels
lon Exchange Resin (750 ft*)
Process Piping, Valves, and Accessories
Instruments and Controls
Salt and Brine Storage
Subtotal

100

Process Equipment installation

Mechanical
Electrical
Painting and Miscellaneous
Subtotal

Regeneration Wastewater Surge Tank
Building and Concrete
Site Work, Fence, and Miscellaneous
Subtotal
Contingency 20%
Total”

35
12

16
63
Miscellaneous installed items

70
80
20
170
112

670 857

(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.

Final capital cost estimate (see Table 3-2).

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

20

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).

Minimize the number of bends in pipe runs (some
bends are necessary—those that are optional
increase costs).

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).



Table 5-1. Valve Operation Chart for Treatment Vessels in Treatment and Regeneration Operational Modes

Flow
Flowrate Duration Valve No.
Mode {gprvft’) (min) 1.203 4 5 6
Treatment 10 © eo 8 KX KX KX xX
Regeneration
Backwash 34 20 (max.) x xX @ @© x x
Drain to top of bed Gravity 5 x x x x x .
Fill tank with brine 2 20 x xX x xX © x
Regeneration 2 20 x xX x x @ @
Drain to top of bed Gravity 5 x x x xX KX @
Fill tank with waterTM 2 20 x xX xX xX © x
Slow rinse” 2 20 x xX xX XK @ ©
Fast rinse 10 30 (max.) e x Kx KX XK ®@
Standby - - x x x x x x
Treatment 10 0 ee 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 Vessel 1B Vessel 2
Valve No. Val Valve No.
Al Feedwater Bi Feedwater 21 Feedwater
A2 Treated water B2 Treated water 22 Treated water
A3 Backwash feed B3 Backwash feed 23 Backwash feed
A4 Backwash to waste B4 Backwash to waste 24 Backwash to waste
AS Brine feed BS Brine feed 25 Brine feed
A6 Regeneration to waste B6 Regeneration to waste 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 lb/ft? 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

37

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



3.3.1.4 Salt (NaCl) 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-Ib 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 lb/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% NaCl) 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 flowrate 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

19

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
fow-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.





4.0 Central Treatment System Capital Cost .

5.0

6.0

4.1 Introduction.............
4.2 Discussion of Cost Variables.
4.2.1
4.2.2
4.2.3 .
4.2.4 Soil Condition
4.2.5 100-Year Flood Plain
4.2.6 Existing and Planned (Future) Potable Water System
Parameters

nN
BoaarN

Nn

4.2.6.2 Potable Water Storage Facilities

4.2.6.3 Distribution and Consumption ...

4.2.7 Backwash and Regeneration Disposal Concept
4.2.8 Chemical Supply Logistics ..

4.2.9 Manual vs. Automatic Operati

4.2.10 Financial Considerations .......

4.3 Relative Capital Cost of Arsenic Removal.

BSOOGGHGBXD

wo

Treatment Plant Operation. 35
5.1 Introduction... 5
5.2 Plant Preparation. 5
5.2.1 Operation Review .. 5
5.2.2 Resin Loading... 5
5.2.3 Initial Startup Preparation 7
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 Requirement 42
5.10 Operating Record: 43
5.10.1 Plant Log 43
5.10.2 Operation Log 243
5.10.3 Water Analysis Repot 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
§.11 Treatment Plant Maintenance -43
§.12 Equipment Maintenance... 45
§.13 lon Exchange Resin Maintenance. 45
5.14 Treatment Chemical Supply . 45
5.15 Housekeeping... 45

Central Treatment Plant Operating Cost.
6.1 Introduction
6.2 Discussion of Operating Costs .
6.2.1 Treatment Chemical Cost
6.2.1.1 Salt Cost seeeseenesaesens
6.2.1.2 Pre-Treatment Oxidation Chemical Cost.
6.2.2 Operating Labor Cos!
6.2.3 Utility Cost............
6.2.4 Replacement lon Exchange Resin Cos!
6.2.5 Replacement Parts and Miscellaneous Material Costs.

6.3 Operating Cost Summary

vi



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)

Phenolphthalein Alkalinity (P)

Total Hardness”

Sulfate

Chloride

Nitrate

Total Noncarbonate Solids

Silica - SiOz

Free Carbon Dioxide

Iron (Fe) Unfiltered

Iron (Fe) Filtered

Manganese

Turbidity (NTU)

Color (Units)

Fluoride

Arsenic - Total

Soluble Arsenic

Particulate Arsenic

Arsenic (Ill)

Arsenic (V)

pH

Specific Conductance (micro-mhos)

Temperature (°F)

(a) mg/L as CaCOs.
All units expressed as mg/L except as noted.

Figure 3-1. Water Analysis Report

10



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

47

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/paltet) 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
Tanges from 3 to 6¢/lb, depending on the geographic
location of the treatment plant. Similarly, pallets of bags
of salt range in price from 6 to 10¢/Ib.

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 1¢ to 6¢ 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(III} 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(tll) to As(V) must be
removed, it can be done by a bed of granular activated
carbon (GAC) 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.



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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
Teality. 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 lon Exchange Arsenic Removal Water Treatment

Plants at an Ideal Location

Location:

Flowrate: 620 gpm Cost ($1,000)

Date: Manual Automatic

Operation Operation

Process Equipment

Treatment Vessels 99 99

lon Exchange Resin (750 ft°) 127 127

Process Piping, Valves, and Accessories 45 88

Instruments and Controls 12 73

Salt and Brine Storage —& 68
Subtotal 289 393

Process Equipment installation

Mechanical 42 50

Electrical 6 40

Painting and Miscellaneous 12 12
Subtotal 60 102

Miscellaneous installed Items

Regeneration Wastewater Surge Tank ti) 0

Building and Concrete 6 6

Site Work, Fence, and Miscellaneous _0 _o
Subtotal 6 6

Contingency 10% 36 50

Total® 391 $51

(a) Engineering, exterior utility pipe and conduit, wastewater and waste solids processing
system, finance charges, real estate cost, and taxes not included.

27





rather than economic considerations may dictate build-
ing costs.

The aggregate cost for the building and regeneration
wastewater surge tank installation, along with their asso-
ciated civil work, becomes a major portion of the overall
capital cost (see Table 3-2). Great care should be
exerted in interpreting the climatological conditions and
their requirements.

4.2.3. Seismic Zone

Seismic design should comply with the requirements of
the local building codes. Buildings and tall slender equip-
ment are vulnerable to seismic loads. In zones of
extreme seismic activity, low profile equipment and
buildings are recommended.

4.2.4 Soil Conditions

Unless soil boring data are already available for the
treatment system site, borings should be required where
the foundations for heavy equipment items (e.g., treat-
ment vessels and regeneration wastewater surge tank)
will be located. If the quality of the soil is questionable
(fill or very poor load bearing capacity), additional soil
borings should be obtained. Poor soil may require costly
excavation/backfill and foundations.

Combinations of poor soil with rock or large boulders can
make foundation work more complex and costly. Rocks
and boulders, combined with extreme temperatures, can
Tesult 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

28

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 wells 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



100 ug/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 taboratories
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.

5.10.2 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.

43

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 all 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.



FREEBOARD "
90% BED 0.9h
EXPANSION d
ss
H
TREATMENT h
MEDIA
4
L— Minimum clearance
required between
TREATMENT VESSEL bottom of vessel and
concrete pad
SYMBOLS
aq — TREATED WATER FLOW RATE (gpm)
d  — TREATMENT BED DIAMETER (fl), d = /4V/sh
h —— TREATMENT BED DEPTH  ({t.)
V-= TREATMENT BED VOLUME - sith (ft?)
epct = —
M, — DENSITY OF TREATMENT MEDIA (Ib./ft.” )
My ~ WEIGHT OF MEDIA  (Ibs.)
0 — OUTSIDE DIAMETER OF TREATMENT VESSEL  (ft.)
d, — 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 = 2dy +h + 09h + 6" + 1"
D=ag+1"
M,= 42 Ib./ft? (VARIES WITH ION EXCHANGE RESIN)
My= M, x V = 42V. (Ib.)

Figure 3-3. Treatment Bed and Vessel Design Calculations

16



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:

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
metered 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 f° (750 gal). The
rate units employed in this design manual are ¢/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.

46

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 feedwater 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.



8. Sample Panel (optional)

b.

Sample tubing from sample points with shut off
valves

Wet chemistry laboratory bench with equipment,

glassware, reagents, etc.

9. Softener Salt Storage and Feed Subsystem

a.
b.

Emergency shower and eyewash
Softener salt storage tank (optional)
i. Fill, discharge, and vent

Level sensor (optional)

iii. Dust collection in vent

iv. Weather protection

Brine tank

i. Water fill pipe with float valve
Softener salt feed pipe (optional)
iii. Drain valve

iv. Containment basin

10. Preoxidation Chemicai Storage and Feed
Subsystem (optional)

a.
b.

Emergency shower and eye wash

Preoxidation chemical storage tank outside

treatment building (optional)

i. Fill, discharge, drain, vent, and overflow
piping

ii, Liquid level sensor (optional)

55

iii, Immersion heater with temperature control
iv. Weather protection
v. Containment basin (optional)
¢. 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)
Surge tank (optional)

Unlined evaporation pond (optional)
Sewer (optional)

Drainage ditch (optional)

Other discharge method (optional)

oao079

12. Toxic Regeneration Wastewater Disposal System
a. Surge tank (optional)
b. Wastewater reclamation system (optional)
c. Other discharge method (optional)



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.



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 pliant 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.

35

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.

5.2.1 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



August 21, 2001

Mr. John Doe

ABC Engineering, Inc.
P.O. Box 1000

DEFG, AA 10000-1000

Ref: Municipal Bid Quotation for Arsenic Removal lon Exchange Resin

Dear Mr. Doe,

XXXXZ is a Type | 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 (NaCl). XXXXZ undergoes rigorous
cleaning steps for potable water application. This is to remove the organic extractables 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 T/L) 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



Then,

2
v= GS2T*Sr _ 260

Then, My = 3 x 250 ft x 42 Ib/ff® = 31,500 Ib

Because the media quantity is almost a 40,000-Ib
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:

H=h+0.9h+4"+(2)D/4+1"=

48" +44" +4" +2 (*) +4175 151" = 13'1"

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
lule 80

b. Backwash pipe main:

q = 4 gpmift? x 62 ft? = 248 gpm
Try 4", v = 6.2 ft/sec, therefore NG
Try 6", v = 2.8 ft/sec, therefore OK
Use 6" I VC

c. Brine (6% NaCl) pipe main:
q = 2 gpmitt x 62 ft? = 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% NaCl) pipe main
q = 0.2 * 2 gpmift? x 62 ft? = 25 gpm
Try 1%", v = 4.0 ft/sec, therefore OK
Use 1%" 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%

58

treatment bed expansion. This rate is sensitive
to raw water temperature.

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 1.33 1b/1,000 gal treated water.
Then the salt consumption is 50 lb/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% NaCl @ 40 gpm). A 1,200-gal brine day
tank will satisfy the NaCl 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/ft®

Number of cubic feet of media per regeneration =
250 f°

Tank construction - epoxy interior lined carbon steel

Find:

Volume of wastewater per regeneration = 150 gal/ft®
x 250 f° = 37,500 gal = 5,000 ft°

Dimensions of surge tank (use height = 16 ft)

Then,

4x 5,000 ft°

_ 2
nien  R

(diameter ? =


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.

columns.

(d) Three parallel column system with
storage: all three columns operating at
same time; staggered exhaustion cycles

of columns. standby.

(b) Two parallel column system with
storage: both columns operating at same
time; staggered exhaustion cycles of

(@) Three-column system with storage:
‘one lead column and tag column operating
at one time. Second lead column in

(c) Two serial column system with
storage: both columns operating at same
time.

Explanation

f Anion Resin Columns

CJ Storage Tank

ARSENIC REMOVAL COR]

Figure 1-2. Examples of Arsenic Removal lon Exchange System Designs



This can be done by closing the butterfly valves in the
Taw 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 lon 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

45

be closed immediately and backwashed at 4 gpm/ft 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 ofce per week. Any chemical spill should be neu-
tralized and cleaned up immediately. Equipment should
be repainted at least once every five years.



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., 1999. lon Exchange and Inorganic Adsorp-
tion. Water Supply and Treatment, 5th ed. McGraw-Hill,
New York, NY.

Clifford, D., Ceber, L., & Chow, S., 1983. Arsenic(III)/
Arsenic(V) Separation by Chloride-Form lon-Exchange
Resins. Proceedings of the Tenth American Water
Works Association (AWWA) Water Quality Technology
Conference, Norfolk, VA.

Clifford, D.A. et al., 1998. Arsenic lon-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 (Ill) and-Arse-
nic (V) in Groundwaters by lon Exchange. Talanta,
30:5:37 1-373.

Gallagher, P.A. et al., 2001. Speciation and Preservation
of Inorganic Arsenic in Drinking Water Sources Using
EDTA with IC Separation and ICP-MS Detection.
J. Environ. Monit., 3:371.

Ghurye, G.L., & Clifford, D., 2001. Laboratory Study on
the Oxidation of Arsenic Ill 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 lon Exchange. J. AWWA, 91:10:85.

51

Horng, L.L., & Clifford, D.A., 1997. The Behavior of Poly-
protic Anions in lon Exchange Resins. Reactive and
Functional Polymers, 35:1/2:41.

Lowry, J.D., & Lowry, S.B., 2002. Oxidaton of As(Iil) by
Aeration and Storage. EPA/600/R-01/102. United States
Environmental Protection Agency, National Risk Man-
agement Laboratory, Cincinnati, OH.

MacPhee, M.J. et al., 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.



2.0 Arsenic Removal by lon 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 lon 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(IIl) unless the As(Ill) 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
(R HAsO, ). 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:

2RCi+HAsO? =RHASO, + 2Cr (1)

R,HASO, + 2NaCl =2RCI+Na,HAsO, (2)



EPA/600/R-03/080
June 2003

Design Manual:

Removal of Arsenic from
Drinking Water by lon 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

Recycled/Recyclable
Printed with vegetable-based ink on
Paper that contains a minimum of
50% post-consumer fiber content
processed chlorine free,



4.1 Introduction

The client should be provided with the least expensive
ion exchange resin central treatment system that can
Temove 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)

¢) 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.

4.0 Central Treatment System.Capital Cost

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:

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).

No seismic requirements.

4. Existing concrete pad located on well compacted,
high-bearing-capacity soil.



SEPA

United States
Environmental Protection
Agency

National Risk Management
Research Laboratory
Cincinnati, OH 45268

Official Business
Penalty for Private Use
$300

EPA/600/R-03/080
June 2003

Please make all necessary changes on the below label,
detach or copy, and return to the address in the upper
left-hand corner.

It you do not wish to receive these reports CHECK HEREL] ;
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EPA
PERMIT No. G-35



controls. Chemical pumps may also have manual
stroke length adjustment. Motors should also have
manual on/off controls.

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.

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. Ina 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:

4. 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

14

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.

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.

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.

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.





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
Ttequired) 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
tates 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 ton Exchange Resin

Water flowrate Pressure drop in psi
(gpm?) per foot of bed depth

6.0 0.5

8.0 0.7

10.0 1.0

12.0 1.3

14.0 16

16.0 2.0

Note: Water temperature 80°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
levet will vary depending on the analytical method used
to measure the arsenic, it probably would be near
3 g/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



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 removai 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 ft’) 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:

22

Influent pipe — enters vertically at center of top
head.

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.

Brine feed pipe — enters horizontally through
vertical straight side three inches above top of
treatment bed.

Air/vacuum valve (vent) — mounts vertically on top
head adjacent to influent pipe.

Resin removal — exits horizontally through vertical
straight side immediately above false flat bottom at
orientation assigned to this function.

Sight glass (12 inches high x 2 inches wide) —
located vertically with centerline at top of treatment
bed (serves to locate liquid level during drain steps
and to observe level of top of bed).

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 instailed,
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:

41. 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.



50

20

CAPITAL COST, $ x 100,000 (AUGUST 2001)

a

o 9% 100 200 500 600 700

10
FLOWRATE, gpm

Figure-4-1. Capital Cost vs. Flowrate at Typical Locations for Arsenic Removal Water Treatment Plants
by Means of the lon Exchange Process (for itemized cost breakdown, see Appendix C)

80

70

60

3 |
i. ae
8
:" — mo |
- cc,
. 5 =
5 |
a

400
FLOWRATE, gpm

Figure 4-2. Capital Cost vs. Flowrate at ideal Locations for Arsenic Removal Water Treatment Plants by
Means of the lon Exchange Process (for itemized cost breakdown, see Appendix C)

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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 contro! 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 that 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 Nationa! 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 pg/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.

lon 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 fevels 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



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.

4. Raw Water Influent Main

a. Flow control

b. Flowrate measurement, flow total

c. Preoxidation chemical injection for oxidation of
As(III) to As(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

. Isolation valve
|. Temperature indicator

2. Intervessel 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

53

sa >o

Sample after pH adjustment piped to sample
panel

Pressure indicator

Booster or repressurization pump (optional)
Disinfection injection (optional)

lsolation valve

Raw Water Bypass Main (optional)

ao79

.Flow control

Flowrate measurement, flow total
Backflow preventer

Isolation valve

Backwash/Regeneration Feed Manifold

xT seme aocD

Process control valves

Isolation valves

Backflow preventers

Flow controls

Flowrate measurements, flow totals
Brine tank

Brine eductor

Brine injectors

Pressure indicators

Backflow preventors

Sample brine eductor piped to sample manifold

Wastewater Main

gpaooM

T
a
b.
Cc.
d.
e.
f.

Process control valves
Backflow preventers

Process isolation valves

Sight glass

Sample piped to sample panel

treatment Vessels

Pressure vessel

Treatment media

Internal distribution and collection piping
Pressure relief valve

Air/vacuum valve

Operating platform and/or ladder (optional)



TREATMENT FLOW - VESSEL "1A" IN LEAD POSITION

VESSEL "1A" REGENERATION & SLOW RINSE

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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



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 wail effects and channeling. A backwash rate of
3to 4 gpm/ft” (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-

ra

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 NaCi 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/ft® of resin. That
is based on a flowrate of 0.5 gpm/ft® 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/ft” 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 fo 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/ft* 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



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(III)], 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 Asi(III), some only As(V), and some the
combination of both As(IIl) and As(V). Arsenate exists in
four forms in aqueous solution, depending on pH:
HsAsO,, H2AsO,, HAsO,”, and AsO,°. Similarly, arse-
nite exists in five forms: HsAsO3’, H3sAsOs, HAsO”,
HAsO, and AsO; In the common ground water pH
range of 6 to 9, the predominant As(IIl) species is neutral
(H3AsO3), whereas the As(V) species are monovalent
(H2AsO,°) and divalent (HAsO,”).

Until recently (Gallagher et al., 2001), studies on the
preservation of the arsenic species concluded that there
was no effective method for preserving As(III) 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 manuai 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.