EPA/600/R-05/001
November 2004
TECHNOLOGY SELECTION AND
SYSTEM DESIGN
U.S. EPA ARSENIC REMOVAL
TECHNOLOGY DEMONSTRATION
PROGRAM ROUND 1
by
Lili Wang
Wendy E. Condit
Abraham S.C. Chen
Battelle
Columbus, OH 43201
Contract No. 68-C-00-185
Task Order No. 0019
Task Order 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
United States Environmental Protection Agency
Cincinnati, Ohio 45268
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DISCLAIMER
The work reported in this document is funded by the United States Environmental Protection Agency
(EPA) under Task Order (TO) 0019 of Contract No. 68-C-00-185 to Battelle. It has been subjected to the
Agency's peer and administrative reviews and has been approved for publication as an EPA document.
Any opinions expressed in this paper are those of the author(s) and do not, necessarily, reflect the official
positions and policies of the EPA. Any mention of products or trade names does not constitute
recommendation for use by the EPA.
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FOREWORD
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the Nation's
land, air, and water resources. Under a mandate of national environmental 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
subsurface resources; protection of water quality in public water systems; remediation of contaminated
sites, sediments and groundwater; 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 environmental problems by: developing and promoting technologies that protect and improve
the environment; advancing scientific and engineering information to support regulatory 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.
Lawrence W. Reiter, Acting Director
National Risk Management Research Laboratory
in
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ABSTRACT
On January 18, 2001, the U.S. Environmental Protection Agency (EPA) finalized the maximum
contaminant level (MCL) for arsenic at 0.01 mg/L. EPA subsequently revised the rule text to express the
MCL as 0.010 mg/L (10 (ig/L). The final rule requires all community and non-transient, non-community
water systems to comply with the new standard by February 2006. In October 2001, EPA announced an
initiative for additional research and development of cost-effective technologies to help small community
water systems (< 10,000 customers) meet the new arsenic standard, and to provide technical assistance to
operators of small systems in order to reduce compliance costs.
As part of this Arsenic Rule Implementation Research Program, EPA's Office of Research and
Development (ORD) proposed a project to conduct a series of full-scale, long-term, on-site
demonstrations of arsenic removal technologies, process modifications, and engineering approaches
applicable to small systems in order to evaluate the efficiency and effectiveness of arsenic removal
systems at meeting the new arsenic MCL. For the Round 1 demonstration study, the selected arsenic
treatment technologies include nine adsorptive media systems, one ion exchange system, one coagulation
/filtration system, and one process modification. The adsorptive media systems use four different
adsorptive media, including three iron-based media (i.e., ADI's G2, Severn Trent and AdEdge's E33, and
USFilter's GFH), and one iron-modified activated alumina media (i.e., Kinetico's AAFS50, a product of
Alcan). The flowrate of these systems ranges from 37 to 640 gallons per minute (gpm).
This report provides the source water quality characteristics at each of the 12 demonstration sites and the
general rationale used to select the technologies for demonstration at each site. Information on the design
and operation of each treatment system also is presented. The selection of the technologies for
demonstration at each location was a cooperative decision made by the water system, state, and EPA.
Many factors were considered in the selection process, including water quality, residual production and
disposal, complexity of system operation, and costs. The selection of the adsorptive media and
pretreatment methods depended on a number of factors that affect the system performance, including
arsenic concentration and speciation, pH, and the presence of competing anions, as well as media-specific
characteristics such as costs, media life, and empty-bed contact time (EBCT) requirements.
IV
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CONTENTS
ABSTRACT iv
FIGURES vi
TABLES vi
ABBREVIATIONS AND ACRONYMS vii
ACKNOWLEDGEMENTS viii
1.0 INTRODUCTION 1
1.1 Purpose and Scope 1
1.2 Background 1
1.3 Occurrence of Arsenic and Source Water Quality 2
2.0 TECHNOLOGY SELECTION 6
2.1 Technology Selection Factors 6
.1 Water Quality 6
.2 Residuals Generation and Disposal 7
.3 Complexity of System Operation 8
.4 Cost 9
.5 Other Factors 9
2.2 Adsorptive Media Technologies 9
2.2.1 Technology Description 9
2.2.2 Adsorptive Media Selection Factors 12
2.2.2.1 Arsenic Concentration and Speciation 12
2.2.2.2 pH Value 12
2.2.2.3 Competing Anions 13
2.2.2.4 Media-Specific Characteristics 13
2.2.2.5 Media Costs 13
2.2.2.6 Regenerability 14
2.3 Ion Exchange Technology 14
2.4 Coagulation/Filtration and Iron Removal Technologies 15
2.4.1 Macrolite® Pressure Filtration 15
2.4.2 System Modification 16
3.0 Technology Design and Operation 17
3.1 Adsorptive Media 17
3.1.1 Bow, NH (G2 Media) 17
3.1.1.1 Treatment System Description 17
3.1.1.2 Treatment System Operation 18
3.1.2 Desert Sands MDWCA, NM (E33 Media) 18
3.1.2.1 Treatment System Description 18
3.1.2.2 Treatment System Operation 19
3.1.3 Brown City, MI (E33 Media) 19
3.1.3.1 Treatment System Description 19
3.1.3.2 Treatment System Operation 19
3.1.4 Queen Anne's County, MD(E33 Media) 19
3.1.4.1 Treatment System Description 20
3.1.4.2 Treatment System Operation 20
3.1.5 Nambe Pueblo, NM (E33 Media) 20
3.1.5.1 Treatment System Description 20
3.1.5.2 Treatment System Operation 20
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3.1.6 Rimrock, AZ (E33 Media) 21
3.1.6.1 Treatment System Description 21
3.1.6.2 Treatment System Operation 21
3.1.7 Rollinsford, NH (E33) 21
3.1.7.1 Treatment System Description 22
3.1.7.2 Treatment System Operation 22
3.1.8 STMGID, NV (GFH Media) 22
3.1.8.1 Treatment System Description 22
3.1.8.2 Treatment System Operation 23
3.1.9 Valley Vista, AZ (AAFS50 Media) 23
3.1.9.1 Treatment System Description 23
3.1.9.2 Treatment System Operation 23
3.2 Ion Exchange 23
3.2.1 Fruitland, ID (Purolite A-520E Resin) 23
3.2.1.1 Treatment System Description 24
3.2.1.2 Treatment System Operation 24
3.3 Coagulation/Filtration 24
3.3.1 Climax, MN 24
3.3.1.1 Treatment System Description 24
3.3.1.2 Treatment System Operation 25
3.3.2 Lidgerwood, ND 25
3.3.2.1 Treatment System Description 25
3.3.2.2 Treatment System Operation 26
4.0 REFERENCES 27
Appendix A: Photographs of Arsenic Removal Treatment Systems A-l
FIGURES
Figure 1 -1. Locations of EPA Round 1 Arsenic Removal Technology Demonstration Sites 3
Figure 2-1. Arsenic Treatment Selection Guide as a Function of Initial Arsenic and Iron
Content of Water 7
TABLES
Table 1-1. General Information of 12 Arsenic Removal Technology Demonstration Sites 2
Table 1-2. Summary of Source Water Quality Data for the 12 Demonstration Sites 5
Table 2-1. Major Decision Factors Considered in the Technology Selection Process 6
Table 2-2. Summary of Residuals Generation and Disposal 8
Table 2-3. Physical and Chemical Properties and Costs of the Adsorptive Media 10
Table 2-4. Water Quality Impact on Pretreatment Requirements at E33 Demonstration Sites 11
Table 2-5. Relative Effectiveness of Various Oxidants for Fe(II) and As(III) Oxidation 12
Table 2-6. Physical and Chemical Properties of Purolite A-520E Resin 14
Table 2-7. Properties of 40/60 Mesh Macrolite® Media 16
Table 3-1. Summary of the Design and Components of the Adsorptive Media Systems 17
VI
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ABBREVIATIONS AND ACRONYMS
AA activated alumina
AM adsorptive media (process)
APU arsenic-package-unit
AWC Arizona Water Company
C/F coagulation/filtration (process)
CO2 carbon dioxide
CS carbon steel
EBCT empty bed contact time
EPA United States Environmental Protection Agency
FRP fiberglass reinforced plastic
GFH granular ferric hydroxide
gpd gallons per day
gpm gallons per minute
HC1 hydrochloric acid
H2SO4 sulfuric acid
HDPE high-density polyethylene
IX ion exchange (process)
KMnO4 potassium permanganate
MCL maximum contaminant level
MDWCA Mutual Domestic Water Consumers Association
MnO2 manganese dioxide
N/A not available
ORD Office of Research and Development
PLC programmable logic controller
PVC polyvinyl chloride
SDWA Safe Drinking Water Act
SM system modification
SS stainless steel
STMGID South Truckee Meadows General Improvement District
TDS total dissolved solids
TO Task Order
ZPC zero point charge
vn
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ACKNOWLEDGEMENTS
This report was prepared by Battelle with input from Thomas J. Sorg, EPA's Task Order Manager.
Darren Lytle and Chris Impellitteri of EPA reviewed the manuscript and provided valuable suggestions
and comments.
Vlll
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1.0 INTRODUCTION
1.1 Purpose and Scope
Battelle, under a contract with the United States Environmental Protection Agency (EPA), is conducting
full-scale demonstration studies on the removal of arsenic from drinking water supplies at 12 water
treatment facilities throughout the United States. These demonstration studies evaluate the efficiency and
effectiveness of the systems in meeting the new arsenic maximum contaminant level (MCL) of 0.010
mg/L (10
This report reviews the source water quality characteristics at each of the 12 demonstration sites and
presents the rationale behind the selection of an arsenic removal technology for each site given its unique
source water quality. The report also summarizes the design and operation of each of the technologies
selected for the demonstration sites. The types of arsenic removal technologies demonstrated in this
project include nine adsorptive media systems, one anion exchange system, one coagulation/filtration
system, and one system modification to a MnO2-coated anthrasand filtration system. Other drinking
water treatment technologies are available for arsenic removal, such as reverse osmosis and
nanofiltration; however, the focus of this report is the technologies selected for the 12 full-scale
demonstration studies.
1.2 Background
The Safe Drinking Water Act (SDWA) mandates that EPA identify and regulate drinking water
contaminants that may have adverse human health effects and that are known or anticipated to occur in
public water supply systems. In 1975 under the SDWA, EPA established an MCL for arsenic at 0.05
mg/L. The SDWA was amended in 1996 and required that EPA develop an arsenic research strategy and
publish a proposal to revise the arsenic MCL by January 2000. On January 18, 2001, EPA finalized the
arsenic MCL at 0.01 mg/L (EPA, 200 la). In order to clarify the implementation of the original rule, EPA
revised the rule text on March 25, 2003 to express the MCL as 0.010 mg/L (10 (ig/L) (EPA, 2003a). The
final rule requires all community and non-transient, non-community water systems to comply with the
new standard by February 2006.
In October 2001, EPA announced an initiative for additional research and development of cost-effective
technologies to help small community water systems (<10,000 customers) meet the new arsenic standard,
and to provide technical assistance to operators of small systems in order to reduce compliance costs. As
part of this Arsenic Rule Implementation Research Program, EPA's Office of Research and Development
(ORD) proposed a project to conduct a series of full-scale, on-site demonstrations of arsenic removal
technologies, process modifications, and engineering approaches applicable to small systems. Shortly
thereafter, an announcement was published in the Federal Register requesting water utilities interested in
participating in the EPA-sponsored demonstration program to provide information on their water systems.
In June 2002, EPA selected 17 sites from a list of 1 15 sites to be the host sites for the demonstration
studies. The selection of the sites was based on a number of factors; the three most significant factors
were geographical location, arsenic concentration of the source water, and size of the system.
In September 2002, EPA solicited proposals from engineering firms and vendors for cost-effective arsenic
removal treatment technologies for the potential 17 host sites. The objective of this solicitation was to
select treatment technologies for the demonstration project, which evaluates the efficiency and
effectiveness of drinking water treatment technologies to meet the new MCL under varying source water
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quality conditions. For the purposes of this solicitation, "treatment technologies" included process
modifications and engineering approaches as well as new or add-on treatment technologies.
EPA received 70 technical proposals for the 17 host sites, with each site receiving from one to six
proposals. In April 2003, an independent technical review panel reviewed the proposals and provided its
recommendations to EPA on the technologies that it determined were acceptable for the demonstration at
each site. Because of funding limitation and other technical reasons, only 12 of the 17 sites were selected
for the demonstration project. A listing of the 12 sites showing the location (sorted geographically from
the Northeast to the Southwest), arsenic concentration of the source water, and size of the water system to
be demonstrated is presented in Table 1-1.
Table 1-1. General Information of 12 Arsenic Removal Technology Demonstration Sites
State
NH
NH
MD
MI
MN
ND
NM
NM
AZ
AZ
ID
NV
Demonstration Site
Bow
Rollinsford
Queen Anne's County
Brown City
Climax
Lidgerwood
Desert Sands MDWCA
Nambe Pueblo
Rimrock
Valley Vista
Fruitland
STMGID
Technology
AM(G2)
AM(E33)
AM(E33)
AM (E33)
C/F
SM
AM (E33)
AM (E33)
AM (E33)
AM (AAFS50)
IX
AM (GFH)
Vendor
ADI
AdEdge
Severn Trent
Severn Trent
Kinetico
Kinetico
Severn Trent
AdEdge
AdEdge
Kinetico
Kinetico
USFilter
Design
Flowrate
(gpm)
70(a)
100
300
640
140
250
320
145
90(a)
37
250
350
Source Water Quality
As
(HS/L)
39
36(b)
19(b)
14(b)
39(b)
146(b)
23(b)
33
50
41
44
39
Fe
(HS/L)
<25
46
270(c)
127«o
546(c)
l,325(c)
39
<25
170
<25
<25
<25
PH
7.7
8.2
7.3
7.3
7.4
7.2
7.7
8.5
7.1
7.8
7.4
7.4
AM = adsorptive media process; C/F = coagulation/filtration process; IX = ion exchange process;
SM = system modification; MDWCA = Mutual Domestic Water Consumers Association;
STMGID = South Truckee Meadows General Improvement District
(a) Due to system reconfiguration from parallel to series operation, the design flowrate is reduced by 50%.
(b) Arsenic exists mostly as As(III).
(c) Iron exists mostly as soluble Fe(II).
Using the information provided by the review panel, EPA in cooperation with the host sites and the
drinking water programs of the respective states selected one technical proposal for each site. The
technologies selected for evaluation include nine adsorptive media systems, one anion exchange system,
one coagulation/filtration system, and one process modification with iron addition. The nine adsorptive
media systems use four different media products, including ADI's G2, Severn Trent's and AdEdge's E33,
USFilter's granular ferric hydroxide (GFH), and Kinetico's AAFS50 (a product of Alcan). Table 1-1
summarizes the locations, technologies, vendors, and key source water quality parameters (including
arsenic, iron, and pH) of the 12 demonstration sites. The locations and technologies also are shown in
Figure 1-1.
1.3
Occurrence of Arsenic and Source Water Quality
Arsenic is a common, naturally-occurring drinking water contaminant that originates from the erosion and
dissolution of arsenic-bearing rocks and soils into groundwater. As shown in Figure 1-1, the levels of
arsenic in groundwater vary widely across the United States, with concentrations detected more
frequently above the new MCL of 10 |o,g/L in the southwest and far west. In addition, certain parts
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jitlaldJD I/
Lidgerwood, ND
(system modification)
Climax, MN
(C/F)
Rollinsford, NH
l'\ (E33)
Queen Anne's
County, MD
(E33)
Desert Sands\
MDWCA, NM I
(E33)
Arsenic Concentrations by County
> 10 |jg/L in 10% or more of samples
> 5 |jg/L in 10% or more of samples
> 3 |jg/L in 10% or more of samples
> 3 |jg/L in fewer than 1 0% of samples
Insufficient data
Base Map Source: Welch, A.M., et al., (U.S. Geological Survey, 2000)
Technology
G2 media
E33 media
GFH media
AAFS media
IX: ion exchange
C/F: coagulation/filtration
System modification
Number of Sites
1
6
1
1
1
1
1
Figure 1-1. Locations of EPA Round 1 Arsenic Removal Technology Demonstration Sites
of the Midwest, Great Lakes, Interior Plains near North and South Dakota, and East to Northeast along
the seacoast show pockets of elevated arsenic concentrations. Arsenic concentrations in groundwater
appear to be generally lower in the Southeast with very infrequent detections above 10 ng/L, but less data
is available in this region than in others (Welch et al., 2000).
Arsenic occurs in natural waters in both inorganic and organic forms. However, inorganic forms such as
arsenite [As(III)] and arsenate [As(V)] are predominant in natural waters. The valence and species of
inorganic arsenic are dependent on the oxidation-reduction condition and pH of the water. As a general
rule of thumb, As(III), the reduced trivalent form, is found in groundwater (assuming anaerobic
conditions); and As(V), the oxidized pentavalent form, is found in surface water (assuming aerobic
conditions). This rule, however, does not always hold true for groundwater. Some groundwaters have
been found to have only As(III), others with only As(V), and still others with the combination of both
As(III) and As(V). Arsenite exits in five forms in aqueous solution, depending on pH: IrLAsOs^ H3AsO3,
H2AsO3 , HAsO32 and AsO33 . Arsenate exists in four forms in aqueous solution, also depending on pH:
H3AsO4, H2AsO4 , HAsO4
andAsO43 (EPA, 2003b).
Source water quality plays an important role in the technology selection and the design and operation of
the treatment system. The source water quality at each of the 12 demonstration sites was characterized
based on historic data and source water samples collected and analyzed by Battelle in 2003. The historic
sampling results were obtained from individual facilities and respective state drinking water officials.
The arsenic speciation samples were collected using an anion exchange resin method modified from
Edwards (1998) by Battelle (EPA, 2000). Table 1-2 provides the range of several water quality
parameters at each site and the one-time arsenic speciation sampling results.
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Total arsenic concentrations at the 12 demonstration sites range from 14.2 to 146 |o,g/L. At six of 12 sites,
As(III) is the most prevalent form of arsenic in groundwater with no distinct pattern noted by geographic
region. Three sites (Lidgerwood, ND, Climax, MN, and Rollinsford, NH) have manganese levels above
the secondary MCL of 50 |o,g/L. Lidgerwood, ND and Climax, MN also have consistently higher iron
levels in groundwater above the secondary MCL of 300 |o,g/L (i.e., with a maximum total iron level of
1,620 |o,g/L and 850 |o,g/L, respectively). At both sites, iron is present predominantly in the Fe(II) soluble
form. In general, iron levels are highest in the Great Lakes Region including Michigan and Minnesota,
and Interior Plains including North Dakota. Iron levels are relatively lower in the Northeast and
Southwest.
Because arsenic readily adsorbs onto iron, the concentration of iron in source water is one of the main
factors considered in the arsenic removal technology selection process. Given various regional water
quality parameters, therefore, the presence of iron plays a prominent role in the technology selection and
the treatability of a given water source. The elevated iron levels in the Interior Plains of North Dakota
and northwestern Minnesota also are associated with very hard water (hardness from 228 to 513 mg/L)
and elevated manganese and sulfate concentrations. However, the high iron levels in Michigan are
associated with softer water (hardness at 83.2 mg/L) and relatively lower levels of manganese and sulfate.
Soft water with hardness of less than 102 mg/L is present in the Northeast to East (New Hampshire and
Maryland) and southwest (New Mexico and Nevada). Hard water is noted at both sites in Arizona.
Typical ranges for SiO2 in the United States are reported at 10 to 30 mg/L (Freeze and Cherry, 1979), so
only the STMGID, NV and Fruitland, ID sites have elevated SiO2 concentrations. Phosphate is less than
0.1 mg/L at all 12 sites. Nitrate is detected above the 10-mg/L MCL only at the Fruitland, ID site, and
antimony was detected above the 0.006 mg/L-MCL only at the STMGID, NV site. The pH values of the
source waters range from 7.1 to 8.5, and four of 12 sites have relatively elevated pH levels at or above 7.7
and may require pH adjustment before treatment (Bow, NH; Rollinsford, NH; Nambe Pueblo, NM; and
Valley Vista, AZ).
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Table 1-2. Summary of Source Water Quality Data for the 12 Demonstration Sites
-S
CO
NH
NH
MD
MI
MN
ND
NM
NM
AZ
AZ
ID
NV
3
a
Bow
Rollinsford
Queen
Anne's
County
Brown City
Climax
Lidgerwood
Desert Sands
MDWCA
Nambe
Pueblo
Rimrock
Valley Vista
Fruitland*0
STMGID(C)
en
O
1
OJ
AM (G2)
AM (E33)
AM (E33)
AM (E33)
C/F
SM
AM (E33)
AM (E33)
AM (E33)
AM (AAFS50)
IX
AM (GFH)
03
H
Mg/L
32.0-47.0
33.8-55.9
17.0-19.0
14.2-31.0
31.0-41.0
108-146
17.0-22.7
29.0-33.2
50.0-63.6
39.0-41.0
37.0-44.0
45.0-87.9
9
"3
CO
Mg/L
44.1
33.9
18.7
12.0
34.6
126
22.3
31.4
64.8
38.1
40.1
89.4
1/3
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2.0 TECHNOLOGY SELECTION
Of the 70 technology proposals submitted to EPA by 19 different vendors for consideration for
demonstration, 41 proposals (10 vendors) received either a recommended or highly recommended rating
by the EPA peer review panel. The technologies selected for the 12 demonstration sites consist of four
types of technologies: adsorptive media, ion exchange, coagulation/filtration, and a system modification
using iron addition.
2.1 Technology Selection Factors
The selection of the technologies to be demonstrated at the 12 locations was a cooperative decision made
by the water system, state, and EPA. Many factors were considered in the selection process with the
primary considerations listed in Table 2-1.
Table 2-1. Major Decision Factors Considered in the Technology Selection Process
Decision Factor
Water Quality
Residuals Generation
Residuals Disposal
Complexity of System Operation
Cost
Other
Issues
Impact of water quality on performance and pretreatment
requirements
Quantity and characteristics
Available disposal methods; state requirements
Operational complexity or level of operator oversight
Capital and operational costs (excluding residual disposal)
Adaptability for expansion or new technology conversion
2.1.1 Water Quality. A number of drinking water treatment technologies are available to reduce
arsenic concentrations in source water to below the new MCL of 10 |o,g/L, including adsorption, ion
exchange, membrane processes such as reverse osmosis and nanofiltration, and coagulation/filtration-
related processes. Many of the most effective arsenic removal processes available are iron-based treat-
ment technologies such as chemical coagulation/filtration with iron salts, and adsorptive media with iron-
based products. These processes are particularly effective at removing arsenic from aqueous systems
because iron surfaces have a strong affinity for adsorbing arsenic.
Because of the unique role that iron plays in facilitating arsenic removal, the level of iron in the source
water is a major consideration in the selection of an optimal treatment technology. Figure 2-1 illustrates
how technology selection was strongly influenced by the initial arsenic and iron concentrations in source
water. This figure breaks down technology selection into the following three categories:
• High Iron Levels. Iron removal processes can be used to facilitate arsenic removal from
drinking water supplies via adsorption and co-precipitation. Iron removal treatment is
best suited to source water with relatively high natural iron levels at an iron to arsenic
ratio of 20:1 or greater (EPA, 2001b and 2002). Therefore, source water with this ratio
would be a potential candidate for arsenic removal by iron removal (refer to Region A in
Figure 2-1). Converting this ratio into a removal guideline indicates that 1 mg/L iron
should be capable of removing up to 50 |o,g/L arsenic. This removal capacity is a "rule of
thumb" and will only be achieved under optimum adsorptive and process operational
conditions.
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• Moderate Iron Levels. If the iron to arsenic ratio in source water is less than 20:1, then
a modified treatment process such as coagulation/filtration with the addition of an iron
salt may be selected (refer to Region B in Figure 2-1).
• Low Iron Levels. Technologies such as adsorptive media, ion exchange, and membrane
processes are best suited to sites with relatively low iron levels in their source water at
less than 300 |o,g/L, the secondary MCL for iron (refer to Region C in Figure 2-1). Above
this level, taste odor, and color problems can occur in treated water, along with an
increased potential for fouling of system components with iron particulates. In addition,
ion exchange resins cannot effectively remove Fe(III)-arsenic complexes (EPA, 2000).
As shown in Figure 2-1, 10 of the 12 sites for this demonstration project are considered low-level iron
sites and only two of the 12 sites have sufficiently high iron levels to be considered for a modified iron
removal process.
Media Adsorption; j,
Ion Exchange; "~
Reverse Osmosis;
Nanofiltration
• RR
Rw «
•
AN
LW
•
Modified Iron Removal Process
B
CM
•
20:1 Fe/As ratio
Iron Removal Process
(Optimized for Maximum As Removal)
A
AN: DSMDWCA, NM
BW: Bow, NH
BC: Brown City, Ml
CM: Climax, MN
FL: Fruitland, ID
LW: Lidgerwood, ND
NP: Nambe Pueblo, NM
RN: STMGID, NV
RR: Rimrock, AZ
RF: Rollinsford, NH
SV: Queen Anne, MD
VV: Valley Visla,AZ
0.6 0.8
Iron (mg/L)
Figure 2-1. Arsenic Treatment Selection Guide as a Function of Initial Arsenic and
Iron Content of Water (Sorg, 2002)
2.1.2 Residuals Generation and Disposal. All arsenic removal technologies produce some
residuals that must be disposed of. Table 2-2 summarizes the type and quantity of residuals that will be
generated from each of the 12 demonstration sites, as well as disposal methods. The residuals may be
either a solid material, such as a spent adsorptive media; or a liquid waste, such as backwash water and/or
spent brine from an adsorptive media, an iron removal, or an ion exchange process. The quantity and
characteristics of the residuals often affect technology selection, especially in western states such as
Arizona and New Mexico, where water conservation is a key issue. The quantity of solid residuals
generated is primarily a function of media life. Spent media most likely will pass the Toxicity
Characteristic Leaching Procedure (TCLP) test for disposal at sanitary landfills. The quantity of liquid
waste generated is a function of backwash/regeneration flowrate and frequency. In general, adsorptive
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media systems are backwashed once to twice per month, producing from 10 to 15 bed volumes of
wastewater with each backwashing. Other technologies such as coagulation/filtration may require more
frequent backwashing to prevent excess pressure buildup or filter leakage and are typically backwashed
on a daily to weekly schedule. The characteristics of the backwash water often are determined by
analytes such as turbidity, total dissolved solids (TDS), arsenic, iron, and manganese. Availability or
non-availability of an on-site method, such as a leach field, a holding pond, or a sanitary sewer, was
important in selecting the best treatment option for a demonstration site. Off-site disposal also might be
an option, such as for the Queen Anne's County, MD site. Recycling of backwash water may be required
at some locations, especially if the treatment system does not have access to an on-site disposal option or
if reclamation of backwash water is economically attractive. State disposal regulations always are a
major concern.
Table 2-2. Summary of Residuals Generation and Disposal
Technology
AM(G2)
AM (E33)
AM (E33)
AM (E33)
AM (E33)
AM (E33)
AM (E33)
AM(GFH)
AM
(AAFS50)
C/F
IX
SM
Site
Bow, NH
Desert Sands
MDWCA, NM
Brown City, MI
Queen Anne's
County, MD
Nambe Pueblo,
NM
Rimrock, AZ
Rollinsford, NH
STMGID, NV
Valley Vista, AZ
Climax, MN
Fruitland, ID
Lidgerwood, ND
Design
Flowrate
(gpm)
70
320
640
300
145
90
100
350
37
140
250
250
Spent Media
per Changeout
(ft3)
170
160
320
160
81
54
54
240
44
N/A
N/A
N/A
Backwash Water
(gal)
(Bed Volume)(a)
2,260 - 3,390
(2 - 3 BV)
12,000 - 18,000
(10-15BV)
24,000 - 36,000
(10-15BV)
12,000 - 18,000
(10-15BV)
6,060 - 9,090
(10-15BV)
4,040 - 6,060
(10-15BV)
4,040 - 6,060
(10-15BV)
12,800-17,100
(7 - 10 BV)
1,100-1,440
(3-4 BV)
1,650 - 1,980
7,000 - 10,500(b)
9,600
Backwash Water
Disposal
Surface leach field
Holding pond
Ditch
Off-site disposal
Holding pond
Recycling of liquid
fraction
Subsurface septic
system
Sanitary sewer
Recycling of liquid
fraction
Sanitary sewer
Sanitary sewer
Recycling of liquid
fraction
(a) Applicable to adsorptive media system only.
(b) Including 1,500 gallons of spent brine.
BV = bed volume
2.1.3 Complexity of System Operation. For small systems, complexity of system operation is
always a concern. Complex systems often require more experienced and skilled operators to operate the
systems. During technology selection, questions often raised by system operators include the frequency
of backwashing, chemical addition requirements (pH adjustment, chlorine addition, etc.), and the
frequency of media replacement. The level of automation available for system operation and data
collection can significantly decrease the complexity, and thus can save time.
-------
2.1.4 Cost. With limited resources available, operational cost is always an issue for most small
systems, and thus is a major consideration in technology selection. For this demonstration study, the
capital costs were generally less emphasized by the 12 water systems because the capital investment for
the treatment systems is funded by EPA. However, the capital costs of treatment systems will be a major
concern for most utilities when selecting technologies in the future. Information on the capital costs of
the 12 treatment systems is reported in an EPA report, entitled Capital Costs of Arsenic Removal
Technologies: U.S. EPA Arsenic Removal Technology Demonstration Program Round 1 (EPA, 2004b).
2.1.5 Other Factors. Other factors that influenced technology selection for the 12 demonstration
sites included the adaptability of a selected process for future expansion and the ability to make changes
to a selected process to take advantages of improvement in technology in the future. For example, for the
adsorptive media processes, it was important to consider whether the technology being put in place could
be easily adaptable to using new and possible less costly adsorptive media that may become available in
the future.
2.2 Adsorptive Media Technologies
2.2.1 Technology Description. The adsorptive media process is a fixed-bed process by which ions
in solution, such as arsenic, are removed by available adsorptive sites on an adsorptive media. When the
available adsorptive sites are filled, spent media may be regenerated or simply thrown away and replaced
with new media. Granular activated alumina (AA) was the first adsorptive media successfully applied for
the removal of arsenic from water supplies. More recently, other adsorptive media have been developed
and marketed for arsenic removal.
The adsorptive media process has many advantages for small systems. The process is relatively easy to
operate, has low maintenance requirements and low costs, and typically generates residuals that can easily
be disposed of. Nine of the 12 sites selected an adsorptive media process for demonstration, and all of
them fall under the category of being a low-iron site, with iron levels in the source water at less than 300
Hg/L. Only four different adsorptive media were selected for use at the nine sites: G2 (ADI), E33 (Severn
Trent and AdEdge), GFH (USFilter) and AAFS50 (Kinetico).
The key physical and chemical properties and unit costs of the four adsorptive media are presented in
Table 2-3. All of these media have been widely evaluated in laboratory and pilot tests and have received
listing under the NSF Standard 61 for use in drinking water applications. These materials are either iron
based or alumina-based media. Differences in their overall composition, valence state of the iron,
crystalline structure, available surface area, and other physicochemical characteristics may result in
different arsenic adsorption capacities and kinetics. In addition, it has been demonstrated that iron-based
media typically have higher arsenic removal capacities compared to alumina-based media (EPA, 2003b).
Other emerging adsorptive media types are currently available, but are not being tested as part of the
Round 1 Arsenic Removal Technology Demonstration Program. These materials include iron-based
media such as Engelhard's ARM 200; titanium-based media such as Hydroglobe's MetSorb and Dow
Chemical's XUR; zeolite-based media such as WRT's Z-33, and iron-modified resin such as Solomex's
As:Xnp. Some of these media are expected to be evaluated in the Round 2 Program. The four media
types to be evaluated as part of Round 1 are further described below:
G2 Media. The ADI system at Bow, NH, uses the G2 adsorptive media. G2 is an iron oxide-modified
adsorptive media developed by ADI specifically for arsenic adsorption. It consists of a diatomaceous
earth substrate coated with ferric hydroxide as the primary constituent and active ingredient. ADI
markets G2 media for both As(V) and As(III) removal. Because it preferentially removes As(V) and the
source water at Bow contains primarily As(V), G2 media should be effective at treating the source water
-------
Table 2-3. Physical and Chemical Properties and Costs of the Adsorptive Media
Parameter
G2
E33
GFH
AAFS50
Physical and Chemical Properties
Matrix/ Active Ingredient
Physical Form
Color
Bulk Density (g/cm3)
Bulk Density (lb/ft3)
BET Area (m2/g)
Particle Size Distribution/
Effective Size (mm)
Zero Point Charge(a)
Operating pH Range
EBCT (min)
Regenerability
Diatomaceous
earth (Si-based)
impregnated with
a coating of
ferric hydroxide
Dry powder
Dark brown
0.75
47
27
0.32
N/A
5.5 to 7.5
10
Yes
Iron oxide composite
(90.1%FeOOH)
Dry granular media
Amber
0.45
28
142
10 x 35 mesh
8.3
6.0 to 8.0
5
No
52-57% Fe(OH)3
and p-FeOOH
Moist granular
media
Dark brown
1.22-1.29
76-81
127
0.32-2
7.6
5.5 to 9.0
5
No
83% A12O3 +
proprietary
additive
Dry granular
media
Light amber
0.91
57
220
28 x 48 mesh
7.3
<7.7
5
No
Media Cost
Vendor
Cost ($/ft3)
Cost ($/lb)
ADI
35
0.75
Severn Trent AdEdge
150 245
5.36 8.75
USFilter
238
3.03
Kinetico
82
1.44
(a) Amy et al. (2004).
N/A = not available.
EBCT = empty bed contact time.
at Bow. The level of iron in the source water is low enough that pretreatment for iron removal is not
necessary prior to adsorption.
G2 media adsorbs arsenic most effectively at a pH value within the 5.5 to 7.5 range, and less effectively at
a higher pH value. Historic pH measurements indicate that the pH values are in the range of 7.7 to 7.8;
therefore, acid addition for lowering the pH is included as part of the treatment system to extend the
media life. The presence of other ions in the source water is not expected to impede the arsenic
adsorption because of their relatively low concentrations and because arsenic is more preferred than other
ions by G2 media.
E33 Media. The Bayoxide® E33 media was developed by Bayer AG for the removal of arsenic from
drinking water supplies. It is a granular ferric oxide media designed to remove dissolved arsenic via
adsorption onto its ferric oxide surface. Severn Trent markets the media in the United States for As III
and As V removal as Sorb-33, and offers several arsenic package units (APUs) with flowrates ranging
from 150 to 300 gallons per minute (gpm). Another company, AdEdge, Inc., provides similar systems
using the same media (marketed as AD-33) with flowrates ranging from 5 to 150 gpm. The Sorb-33
demonstration sites are located at Desert Sands Mutual Domestic Water Consumers Association
(MDWCA), NM; Brown City, MI; and Queen Anne's County, MD. The AD-33 demonstration sites are
located at Nambe Pueblo, NM; Rimrock, AZ; and Rollinsford, NH.
E33 adsorbs arsenic and other ions, such as antimony, cadmium, chromate, lead, molybdenum, selenium,
and vanadium. The adsorption is effective at pH values ranging between 6.0 and 9.0. At pH values
10
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greater than 8.0 to 8.5, pH adjustment is recommended to maintain its adsorption capacity. Two
competing ions that can reduce the adsorption capacity are silica (at levels greater than 40 mg/L) and
phosphate (at levels greater than 1 mg/L). In general, water with an iron content of less than 300 |o,g/L
can be treated with E33 media without any pretreatment. Table 2-4 summarizes the impact of water
quality at the six E33 sites on the need for pretreatment, including pre-oxidation of As(III) to As(V) and
raw water pH adjustment. Pre-chlorination also is used for disinfection with the media having only a
slight chlorine demand for only a short period of time, such as one or two week s.
Table 2-4. Water Quality Impact on Pretreatment Requirements at E33 Demonstration Sites
Site
Pre-Chlorination
pH Adjustment
Water Quality
Severn Trent Systems
Desert Sands MDWCA, NM
Brown City, MI
Queen Anne's County, MD
Yes rAs(III) = 21.6 ug/Ll
No [As(ni) = 11.2ug/L]
No [As(III) = 18.4 ug/L]
No [pH = 7.7]
No [pH = 7.3]
No [pH =7.3]
Sulfate 158 to 190 mg/L
Iron up to 200 ug/L
Not Significant
AdEdge Systems
Nambe Pueblo, NM
Rimrock, AZ
Rollinsford, NH
No [As(III) = 0.2 ug/Ll
No [As(III) = <0.1 ug/L]
Yes [As(III) = 20.1 ug/L]
Yes [pH =8.5]
No[pH = 7.1]
Yes [pH = 8.2]
Not Significant
Not Significant
Manganese up to 100 ug/L
GFH Media. GFH is a granular ferric hydroxide media produced by GEH Wasserchemie GmbH of
Germany and marketed by USFilter under an exclusive marketing agreement. GFH is capable of
adsorbing both As(V) and As(III). GFH media adsorbs arsenic within a pH range of 5.5 to 9.0, but less
effectively at the upper end of this range. Arsenic in the source water at the STMGID, NV site is
predominately As(V). With a moderate pH of 6.9 to 7.9 for the source water, pH adjustment is not
recommended. Competing ions such as silica and phosphate in source water can adsorb onto GFH media,
thus reducing the arsenic removal capacity of the media. Source water at STMGID, NV contains less
than 0.1 mg/L of orthophosphate and 28.0 mg/L of sulfate. Only silica concentrations (68.6 mg/L as
SiO2) appear to be high enough to potentially impact the arsenic adsorption capacity.
AAFS50 Media. The Kinetico arsenic adsorption system at Valley Vista, AZ, uses Alcan's Actiguard
AAFS50 media. AAFS50 media is different from conventional AA because it is engineered with a
proprietary additive to enhance its arsenic adsorption performance. Standard grade AA was the first
adsorptive media successfully applied for the removal of arsenic from water supplies. However, it often
requires pH adjustment to 5.5 in order to achieve optimal arsenic removal. The AAFS50 product is
modified with an iron-based additive to improve its performance and to increase the pH range within
which it can achieve effective removal.
Based on vendor's recommendations, As(III) should be oxidized to As(V) in order to maximize arsenic
removal with this media. Based on the results of the field arsenic speciation at the Valley Vista site, 37.8
Hg/L exists as As(V) and only 0.3 ug/L exists as As(III). For this reason, pre-chlorination at this site was
determined to be unnecessary. Optimal arsenic removal efficiency is achieved with a pH of the feed
water less than 7.7. The pH value of the source water ranges from 7.7 to 8.0, thus, pH adjustment
equipment is used. Competing ions such as fluoride, sulfate, silica, and phosphate can adsorb onto
AAFS50 media, and potentially can reduce its arsenic removal capacity. The source water contained 0.2
mg/L of fluoride, 8.7 mg/L of sulfate, 18.5 mg/L of silica (as SiO2), and less than 0.1 mg/L of
orthophosphate. These concentrations appear to be low enough that the operating capacity should not be
greatly affected. The adsorption capacity of AAFS50 can be impacted by both high levels of silica (>40
11
-------
mg/L SiO2) and phosphate (>1 mg/L). In addition, the vendor recommended that the system be operated
in a series configuration to minimize the chance for arsenic breakthrough to impact drinking water
quality.
2.2.2 Adsorptive Media Selection Factors. The performance of arsenic adsorption treatments
systems depends on several factors including arsenic concentration and speciation, pH, presence of
competing anions, and media-specific characteristics such as media life and empty-bed contact time
(EBCT) requirements. Other factors to consider in media selection include the unit and life-cycle costs of
the media and whether it can be regenerated on site.
2.2.2.1 Arsenic Concentration and Speciation. Both arsenic concentration and speciation play a
role in the effectiveness of arsenic removal in an adsorption system. Total arsenic concentration has an
impact on the life-cycle costs for media replacement, as higher initial arsenic concentrations will exhaust
the media more rapidly. The proportion of As(III) and As(V) in source water also influences the need for
pretreatment because of the potential impact of As(III) on the overall life of the media. In general, As(V)
is more readily adsorbed within the pH range of typical drinking water applications. For this reason, it
may be preferable to oxidize As(III) to As(V) in order to increase the effectiveness of an arsenic removal
system. Oxidation of As(III) often is accomplished using a pre-chlorination step to oxidize As(III) to
As(V) prior to entering adsorption vessels. Table 2-5 summarizes the options available for the effective
oxidation of As(III), including the addition of chlorine and potassium permanganate (often used in
conjunction with manganese greensand systems). The effectiveness of the oxidants for oxidizing Fe(II),
commonly found with As III, also is shown in Table 2-5.
Table 2-5. Relative Effectiveness of Various Oxidants for Fe(II) and As(III) Oxidation
Oxidant
Air (aeration)
Chlorine
Chloramine
Ozone
Chlorine dioxide
Potassium permanganate
Fe(II) Oxidation
Effective
Effective
Not effective
Effective
Effective
Effective
As (III) Oxidation
Not effective
Effective
Not effective
Effective
Not effective
Effective
Note: Adapted from EPA (2004a).
2.2.2.2 pH Value. The arsenic removal capacity for both alumina-based and iron-based adsorptive
media can be enhanced by pH adjustment. The lowering of pH can be accomplished using hydrochloric
acid (HC1), sulfuric acid (H2SO4), or carbon dioxide (CO2). A one-time capital cost increase is required
for chemical feed and storage equipment as well as increased operating cost for consumable acid or
caustic. However, the pH adjustment method may be cost-effective given the potential for a significantly
increased media life. A discussion of the impact of pH on arsenic adsorption for both alumina-based and
iron-based media is provided below.
Alumina-based media can remove mainly As(V). The optimal arsenic removal capacity with standard
grade AA is achieved at a pH value of 5.5. For example, process demonstrations showed that arsenic
removal capacity was reduced by more than 15% at pH 6.0 compared to that of pH 5.5 (Rubel, 1984).
Therefore, adjusting the pH of source water can provide removal capacity advantages. The alumina-
based AAFS50 product used in this study has been modified with an iron-based additive to expand the
operational pH range up to 7.7 for effective arsenic removal.
12
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Iron-based media has an affinity to adsorb both As(III) and As(V). The predominant mechanism in
arsenic adsorption onto the iron oxide or hydroxide surface appears to be electrostatic attraction.
However, the adsorption of As(III) versus As(V) is impacted very differently by source water pH. The
adsorption of As(V) decreases with increasing pH values in the 3 to 10 range because, as the pH
increases, the surface charge of the media becomes less positive and there is less attraction to the
negatively charged As(V) species of H2AsO4" and HAsO42". The As(V) species of H2AsO4 dominates at
a pH value between 2.0 and 7.0, and HAsO42" dominates at a pH value between 7.0 and 11.0. On the
other hand, As(III) adsorption is shown to increase with an increase in pH value with a maximum
adsorption at pH 9.0. This is likely because the uncharged species, H3AsO3 predominates for As(III) in
the pH range of natural waters, and at pH 9.0, the H2AsO3" form occurs, thus increasing the affinity for the
positively-charged iron solid surface. The range of effective adsorption of both As(III) and As(V)
overlaps within the pH range of 6.0 to 7.5, with more As(V) adsorbed at a low value pH and more As(III)
adsorbed at a high pH value (Jain and Loeppert, 2000). The optimal pH range for arsenic removal is
specific to each media type; vendor-reported optimal pH ranges are 5.5 to 7.5 for G2, 6.0 to 8.0 for E33,
and 5.5 to 9.0 for GFH.
2.2.2.3 Competing Anions. The adsorption of arsenic is influenced by the presence of other
competing anions in source water such as fluoride, bicarbonate, sulfate, silica, and phosphate. Anions
compete directly for available binding sites on the surface of the media and also can alter the electrostatic
charge at the media surface. This competition has the potential to reduce the overall effectiveness of
arsenic removal from source water. In order for a competing ion to have an effect, it must be present in
sufficient concentration and/or have a stronger affinity for adsorption onto the media than arsenic.
Competing ions such as silica, phosphate, fluoride, and sulfate may adsorb onto AAFS50 and reduce its
removal capacity for arsenic (Kinetico, 2003). For example, the vendor reports that AAFS50 media is
impacted by both high levels of phosphate (>1 mg/L) and silica (>40 mg/L SiO2). E33 is reported to be
affected by silica at levels greater than 40 mg/L, sulfate at levels greater than 150 mg/L, and phosphate at
levels greater than 1 mg/L. G2 is reported to be unaffected by sulfate concentrations up to 250 mg/L.
GFH also experiences effects from competing ions such as silica, phosphate, and sulfate, but no threshold
values were provided by the vendor.
2.2.2.4 Media-Specific Characteristics. Each media has unique characteristics related to its arsenic
adsorption capacity and the kinetics or rate at which arsenic is adsorbed onto the media. These factors
play a role in its overall cost-effectiveness for technology selection and are related to the chemical
composition of the media, its mesh size and surface area, its pore structure, and other physicochemical
properties (such as zero point charge [ZPC]) that impact adsorption processes. Table 2-3 presents the
vendor-reported data for the four media used in this project, including media surface area and mesh size
and recommended EBCT. The adsorption capacity of the media will impact the overall life-cycle cost for
media replacement, and the EBCT primarily impacts the size of the adsorption vessels and the capital cost
of the equipment.
2.2.2.5 Media Costs. The unit costs of the four media used in this study are provided in Table 2-3.
For the alumina-based media AAFS50, the unit cost is relatively low at $ 1.44/lb compared to the unit cost
of the iron-based media, which ranges from $0.75/lb to $8.75/lb. Although the unit cost may be a factor,
the technology selection should rely on an estimate of the life-cycle cost of the media, which is a function
of the media's arsenic adsorption capacity, its expected media life given influent arsenic and water
quality, the size of the vessels, and other site-specific factors. In general, the alumina-based media have
lower arsenic adsorption capacities compared to the iron-based media. Therefore, the iron-based media
would be more cost-competitive because they would need to be replaced less frequently, which would
decrease the overall life-cycle cost. At the end of the one-year evaluation period, the life cycle costs
associated with these four media will be reported as part of a Final Performance Evaluation Report for
each demonstration site.
13
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2.2.2.6 Regenerability. Some of the commercially available arsenic adsorptive media can be
regenerated by chemical pH adjustment upon exhaustion of the arsenic removal capacity. Chemical
regeneration of adsorptive media is economically sound for large systems with high arsenic
concentrations. As the size of the system decreases and/or the raw water arsenic concentration decreases,
the economic benefit compared to the capital and operating cost is diminished. For very small systems, it
may be more cost-effective to use disposable media. G2 media used at the Bow, NH site can be
regenerated using a caustic solution. The vendor reports that the media can be regenerated 4 to 5 times,
with each regeneration resulting in a 10% decrease in the media's capacity for arsenic adsorption.
However, due to the small size of the system at Bow (40 gpm), it was determined that on-site
regeneration would not be cost-effective.
2.3
Ion Exchange Technology
Ion exchange is a fixed-bed process that involves exchanging ions from solution onto a resin. For arsenic
removal, an anion resin in the chloride form is used to remove As(V). Anion exchange resins also
remove other anions such as sulfate, nitrate, and uranium. Because As(III) occurs in water below pH 9
with no ionic charge, As(III) is not removed by the anion exchange process. When the resin eventually
becomes saturated with arsenate and other anions such as nitrate and sulfate, the resin must be
regenerated. In the regeneration step, a sodium chloride brine solution is passed through the spent resin
where the adsorbed arsenate and other anions are replaced with chloride ions. Because of high
concentrations of arsenic in the spent brine, it likely will be classified as a hazardous waste. The
advantages of the anion exchange technology for arsenic removal is simplicity of operation, long resin
life, ease of regeneration, and lack of impact of pH on the exchange capacity.
A Kinetico IX-248-AS/N Ion Exchange Arsenic-Nitrate Removal System was selected for the Fruitland,
ID demonstration site. The system uses a macroporous strong base resin, Purolite A-520E, to remove
arsenic and nitrate from water. Purolite A-520E resin is approved for use in drinking water applications
under NSF Standard 61. The Purolite resin is formed in a matrix of opaque, cream-colored spherical
beads. The physical properties of this resin are summarized in Table 2-6.
Table 2-6. Physical and Chemical Properties of Purolite A-520E Resin
Parameter
Polymer Matrix Structure
Physical Form and Appearance
Whole Bead Count
Functional Groups
Ionic Form as Shipped
Shipping Weight
Screen Size Range (U.S. Standard Screen)
Particle Size Range
Moisture Retention, Cl" Form
Reversible Swelling, Cl" to SO42"/NO3"
Total Exchange Capacity, Cl" Form
Wet, Volumetric
Dry, Weight
Operating Temperature, Cl" Form
pH Range, Stability
pH Range, Operating
Value
Macroporous sryrene-divinylbenzene
Opaque cream spherical beads
95% minimum
Quaternary ammonium
Cl"
680 g/L (42.5 lb/ft3)
16 - 50 mesh, wet
+1200 mm <5%, -300 mm <1%
50-56%
Negligible
0.9 meq/mL minimum
2.8 meq/g minimum
100°C (212°F) maximum
0-14
4.5-8.5
14
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Total arsenic concentrations of the source water at the Fruitland, ID site range from 37 to 44 |o,g/L. Based
on the speciation sampling event, arsenic exists predominantly as As(V) (39.3 |o,g/L). A small amount of
arsenic also exists as As(III) (0.8 |o,g/L) and particulate As (3.4 |o,g/L). Because arsenic is present
primarily as As(V), pre-chlorination is not required at the site.
The efficiency of the ion exchange process for arsenic removal is strongly affected by competing ions,
such as sulfate, nitrate, and TDS. In general, the ion exchange process is not economically attractive if
source water contains high levels of TDS (>500 mg/L) and sulfate (>250 mg/L). Sulfate concentrations
in the Fruitland raw water range from 57.3 to 64.0 mg/L. Sulfate is more preferred by the ion exchange
resin than arsenate (i.e., H2AsO4"). Nitrate concentrations showed an increasing trend from 5.2 mg/L in
July 1986 to 13.90 mg/L in November 2001. In addition to arsenic, nitrate will be monitored during the
one-year performance evaluation study to ensure that it will not exceed the 10 mg/L MCL.
Total iron concentrations in the source water range from the detection limit to 744 |o,g/L. No pretreatment
for iron is planned before the ion exchange process. The uranium concentration was measured at
22.4 ng/L, but does not exceed the EPA MCL of 30 |o,g/L. Because the ion exchange process can remove
uranium (Clifford, 1999), samples will be collected for uranium analyses during the one-year
performance evaluation study. The pH values of the raw source water range from 7.4 to 7.6. To protect
the ion exchange beds from particulates in the groundwater, bag filters have been installed upstream of
the anion exchange system.
2.4 Coagulation/Filtration and Iron Removal Technologies
Iron removal processes can be used to remove arsenic from drinking water supplies. Iron removal
processes involve the oxidation of soluble iron and As(III), adsorption and/or co-precipitation of As(V)
onto iron hydroxides, and filtration. The actual capacity to remove arsenic during iron removal processes
depends on a number of factors, including the amount of arsenic present, arsenic speciation, pH, amount
and form of iron present, and existence of competing ions, such as phosphate, silicate, and natural organic
matter (EPA, 2004a). The coagulation/filtration system selected for the demonstration study is one that
employs an engineered ceramic filtration media, Macrolite®, to remove arsenic-bearing iron solids. In
addition, a process modification is being implemented to provide supplemental iron addition to source
water to enhance the arsenic removal efficiency of a MnO2-coated anthrasand filtration system. The main
advantage of the process is that it uses the natural iron to remove arsenic. Thus, sites with high iron
concentrations requiring an iron removal process can use one process to remove both iron and arsenic.
2.4.1 Macrolite® Pressure Filtration. A Macrolite® arsenic removal system that uses
coagulation/filtration to remove arsenic-bearing iron solids from source water was selected for the
Climax, MN site. Macrolite® is a low-density, spherical media and is designed to allow for filtration rates
up to 10 gpm/ft2, which is a higher loading rate than commonly used for conventional filtration media.
Macrolite* is manufactured by Kinetico and is listed for use in drinking water applications under NSF
Standard 61. Kinetico attributes Macrolite's® increased capacity for flow, while maintaining filtering
capacity, to its uniform, rounded physical shape and rough surface texture compared to the irregular
angular shapes of conventional granular media. The physical properties of this media are summarized in
Table 2-7. Macrolite® also is chemically inert and compatible with chemicals such as acids, caustics,
oxidants, and coagulant chemicals such as ferric chloride.
Total arsenic concentrations range from 31 to 41 |o,g/L in Climax source water. Based on the source water
sampling result, up to 90% of the total arsenic (38.7 |o,g/L) is present as As(III). The proposed treatment
process relies on the oxidation of As(III) to As(V) via chlorination, the adsorption of As(V), and the
filtration of As(V)-bearing iron solids. The source water has iron levels that range from 546 to 850 |o,g/L.
15
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As shown in Figure 2-1, the iron concentration should be 20 times the arsenic concentration to effectively
co-precipitate the arsenic onto the iron solids. The iron analytical results indicate that iron levels are 13 to
27 times higher than the arsenic levels in the source water. There is no plan at this time to supplement the
natural iron levels. In addition, the pH range of 7.4 to 7.9 is within the target range of 5.5 to 8.5 for
arsenic removal by iron oxides.
Table 2-7. Properties of 40/60 Mesh Macrolite® Media
Property
Color
Thermal Stability
Sphere Size Range
Bulk Density
Specific Gravity
Collapse Strength (for 30/50 mesh)(a)
Value
Taupe, Brown to Grey
2,000°F
0.0 14 -0.009 inch
0.86 g/cm3 or 54 lb/ft3
2.05 g/cm3 or 129 lb/ft3
7,000 to 8,000 psi
(a) Data not available for 40/60 mesh.
2.4.2 System Modification. The facility at Lidgerwood, ND, unlike the other demonstration sites,
has a treatment system in place: a coagulation/filtration treatment system for the removal of elevated
levels of iron, manganese, and arsenic in groundwater. Total arsenic concentrations of source water range
from 108 to 146 |o,g/L and total iron concentrations range from 1,310 to 1,620 p.g/L. The existing
treatment system consists of pre-chlorination, forced draft aeration, potassium permanganate (KMnO4)
oxidation, polymer coagulant addition, detention, gravity filtration, post-chlorination, and fluoridation.
Although the existing system normally reduces the iron level to less than 25 |o,g/L, the system reduces the
arsenic to only 26 to 31 (ig/L. The purpose of the demonstration project is, therefore, to evaluate a
treatment modification that can achieve an arsenic level below the 10-|a,g/L arsenic MCL. The
modification selected consists of adding supplemental iron (i.e., ferric chloride) to increase the overall
arsenic removal efficiency of the treatment system.
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3.0 TECHNOLOGY DESIGN AND OPERATION
This section discusses the design and operation of the technology selected for each demonstration site.
The technologies consist of nine adsorptive systems, one anion exchange system, one coagulation/
filtration system, and one system modification. Photographs of the systems on-line at this time are shown
in Appendix A.
3.1
Adsorptive Media Systems
Nine adsorptive media systems using four different adsorptive media were selected for demonstration.
Six systems use E33 media, one uses G2 media, one uses GFH media, and one uses AAFS50 media. A
summary of the major aspects of the adsorptive treatment systems installed is provided in Table 3-1.
Table 3-1. Summary of the Design and Components of the Adsorptive Media Systems
Media
Type
G2
E33
E33
E33
E33
E33
E33
GFH
AAFS50
Site
Bow,NH
Desert Sands
MDWCA, NM
Brown City, MI
Queen Anne's
County, MD
Nambe Pueblo,
NM
Rimrock, AZ
Rollinsford, NH
STMGID, NV
Valley Vista, AZ
Media Vessels
No.
2
2
4
2
3
2
2
3
2
Configu-
ration
Series
Parallel
Parallel
Parallel
Parallel
Series
Parallel
Parallel
Series
Material
SS
FRP
FRP
FRP
FRP
FRP
FRP
CS
FRP
Media
Volume
per
Vessel
(ft3)
85
80
80
80
27
27
27
80
22
EBCT
at
Design
Flow
(min)
lg(a)
3.7
3.7
4.0
4.2
4.5(a)
4.0
5.1
4.4(a)
Pre/Post-Treatment
Pre-
C12
Yes
Yes
No
No
Yes
Yes
Yes
No
Yes
Pre-
pH
Adjust
ment
H2SO4
No
No
No
C02
No
C02
No
H2S04
Post-
C12
No
No
Yes
Yes
No
No
No
Yes
No
Post-
pH
Adjust
ment
NaOH
No
No
No
No
No
No
No
No
SS = stainless steel; FRP = fiberglass reinforced plastic; CS = carbon steel
(a) EBCT is for one vessel only.
3.1.1 Bow, NH (G2 Media). The 40-gpm Bow, NH water treatment system is owned and operated
by C&C Water Services. The system supplies water to 96 homes in the community of Village Shore
Estates. The source water is groundwater drawn from three on-site wells (No. 1, 2, and 3). The well
pumps are controlled by the water levels in two 15,000-gallon storage tanks. Based on the water demand,
the system runs approximately 6 hours per day.
Prior to the installation of the G2 system, the treatment at Bow included addition of a dilute sodium
hypochlorite solution for disinfection, and of sodium hydroxide for pH adjustment. In addition, about 10
to 15% of the flow was treated through an AA system that had been used at the site for several years.
3.1.1.1 Treatment System Description. The G2 adsorption system was originally designed for the
Allenstown, NH site at a flowrate of 70 gpm with two vessels operating in parallel. The system was
subsequently reconfigured for series operation at the Bow, NH site after the Allenstown, NH site had
17
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withdrawn from the demonstration study. The major components of the G2 treatment system are
described as follows:
• Pre-chlorination. Injection of sodium hypochlorite was previously employed for
disinfection at the site and is continued for both disinfection and As(III) oxidation,
although arsenic in the source water exists predominately as As(V).
• Pre-pH adjustment. The pH of the source water is adjusted to approximately 6.5 ± 0.2
using a 50% sulfuric acid solution.
• G2 media adsorption. The G2 media system consists of two 72-inch-diameter, 72-inch-
tall, 304 stainless steel (SS) pressure vessels in series, each containing about 85 ft3 of G2
media. The filter vessels are rated for 50 psi working pressure and can be reversed in the
lead/lag positions manually using a series of valves.
• Post-pH adjustment. After adsorption, the pH of the treated water is adjusted with
sodium hydroxide to approximately 7.5 ± 0.2 before the water enters the distribution
system for corrosion control.
3.1.1.2 Treatment System Operation. The G2 media system is operated in downflow mode through
the SS adsorption vessels. Flow to each vessel is measured and totalized to record the volume of water
treated. Pressure differential through each vessel also is monitored to track the pressure loss. Based on a
set time or a set pressure differential, the adsorption vessels are taken off-line and backwashed one at a
time using treated water to remove media fines built up in the beds and to "fluff the compacted media
bed. The backwash water is discharged to an on-site surface drainage field for disposal.
G2 media in the lead vessel is replaced when the effluent arsenic concentration from the lead vessel
reaches the influent concentration or when the effluent concentration from the lag vessel reaches 10 (ig/L.
After the spent media in the lead vessel is replaced, this vessel becomes the lag vessel. Based on the
average daily use rate of 15,000 gallons per day (gpd), the size of adsorption vessels, and the chemistry of
the source water, it is expected that the G2 media in the lead vessel has an estimated working capacity of
10,300 bed volumes and will last for more than 14 months before change-out is necessary.
3.1.2 Desert Sands MDWCA, NM (E33 Media). The Desert Sands MDWCA serves 1,886
community members near Anthony, NM using an existing supply, storage, and distribution network that
covers an area of approximately four square miles of unincorporated area in southern Dona Ana County.
The water system consists of two production wells (Wells No. 2 and 3 with a combined capacity of 320
gpm), two steel water storage tanks with capacities of 99,000 and 240,000 gallons, and approximately 30
miles of distribution piping. The water production and consumption have fluctuated over the past several
years with the peak production occurring in 1998 at 63.5 million gallons.
3.1.2.1 Treatment System Description. The Severn Trent APU-300 system has a design flowrate of
320 gpm, but can be operated at 350 gpm. The major components of the treatment system are as follows:
• Pre-chlorination. Sodium hypochlorite is added to raw water for disinfection, hydrogen
sulfide control, and As(III) oxidation. The target chlorine level in treated water is 0.3
mg/L.
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• E33 media adsorption. The system consists of two parallel 63-inch-diameter, 86-inch-
tall fiberglass reinforced plastic (FRP) pressure vessels, each containing about 80 ft3 of
E33 media.
3.1.2.2 Treatment System Operation. The APU-300 system is programmed to perform an automated
backwash every 45 days or on a pressure differential of 10 psi, using untreated well water. The vessels
are taken off-line one at a time for backwash. While one vessel is backwashed, the other remains in
service.
Based on an average daily use rate of about 345,600 gpd, the size of adsorption vessels, and the chemistry
of the source water, it is expected that E33 media has an estimated working capacity of 132,000 bed
volumes, and will last for approximately 15 months before change-out is necessary.
3.1.3 Brown City, MI (E33 Media). Brown City supplies water to approximately 1,334 people
and has 630 service connections. The water source is groundwater from wells at three locations. Prior to
the installation of the APU-300 system, the only treatment provided to the groundwater was chlorination
for disinfection. Two wells (Wells No. 3 and 4) are located at the demonstration site. The water from
Well No. 4 is treated by the APU-300 system and currently is operated on an intermittent basis for
approximately 4-8 hours per day.
3.1.3.1 Treatment System Description. The Severn Trent APU-300 system has a design flowrate of
300 gpm, but can be operated at 350 gpm. Because the Brown City water supply wells are rated at 640
gpm, two APU-300 units were installed. The major components of the treatment system are as follows:
• E33 media adsorption. The units consist of four parallel 63-inch-diameter, 86-inch-tall
FRP pressure vessels, each containing about 80 ft3 of E33 media.
• Post-chlorination. Sodium hypochlorite is added for a target residual level of 0.3 mg/L
(as C12) for free chlorine and 0.4 mg/L (as C12) for total chlorine in the distribution
system.
3.1.3.2 Treatment System Operation. Similar to the Desert Sands MDWCA system, the Brown City
system is backwashed automatically every 45 days using untreated source water. The backwash also can
be initiated manually by the operator. The vessels are taken off-line one at a time for backwash. While
one vessel is backwashed, the other three remain in service.
Based on the average daily use rate of about 192,000 gpd, the size of adsorption vessels, and the source
water chemistry, E33 media has an estimated working capacity of 80,000 bed volumes and will last for
approximately 33 months before change-out is necessary.
3.1.4 Queen Anne's County, MD (E33 Media). The Queen Anne's County facility supplies
water to approximately 300 connections in the community of Prospect Bay. The source water is extracted
from two wells that alternate operation for 3-4 hours every other day. However, for the purpose of the
demonstration study, Well No. 1, which is connected to the APU-300 system, operates for about 7 hours
every day at a rate of 300 gpm.
Prior to the demonstration project, the treatment included chlorination using chlorine gas and the addition
of a corrosion inhibitor (polyphosphate). Treated water was sent to a 300,000-gallon storage tank before
the distribution system.
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3.1.4.1 Treatment System Description. The major components of the Queen Anne's County's APU-
300 treatment system are described as follows:
• E33 media adsorption. The APU-300 system is identical to that installed at Desert
Sands MDWCA, NM.
• Post-polyphosphate addition. A polyphosphate chemical is added to treated water for
corrosion control.
• Post-chlorination. Chlorine gas is added to the treated water for disinfection. The target
total chlorine level in distributed water is 0.5 mg/L (as C12). The APU-300 system is
monitored closely during the course of the study to determine if chlorination should be
moved upstream of the E33 vessels in order to oxidize As(III) to improve the removal
efficiency and the life of E33 media.
3.1.4.2 Treatment System Operation. Backwash of the E33 vessels follows the same procedures as
performed at the Desert Sands MDWCA and Brown City.
According to Severn Trent, the estimated working capacity of the media is 114,000 bed volumes, which is
equivalent to 63 months of useful media life when operating the system on an average use rate of
72,000 gpd. As mentioned above, the system will be closely monitored to determine if E33 media is
effective for As(III) removal.
3.1.5 Nambe Pueblo, NM (E33 Media). The existing water system at Nambe Pueblo, NM
supplies drinking water to approximately 500 community members with 150 service connections. The
system consists of a 145-gpm well in a pump house containing a chlorine feed system and a 17-ft-
diameter, 24-ft-high, 40,000-gallon water storage tank. The well pump is operated for 3 to 4 hours per
day and produces approximately 34,000 gpd. A peristaltic pump injects chlorine into the water upstream
of the water storage tank to maintain a residual chlorine level of 0.2 mg/L in distributed water. Water in
the storage tank is gravity-fed through the distribution system to the community.
3.1.5.1 Treatment System Description. The AdEdge APU-150 system has a design flowrate of
145 gpm, and consists of an APU-100 and an APU-50 unit, with the components programmed to run
cooperatively. The major components of the complete water treatment system are as follows:
• Pre-pH adjustment. The pH will be adjusted from above 8 to 7.0 by adding CO2 to the
water upstream of the APU-150 treatment system.
• Pre-chlorination. The existing chlorine addition system will continue to be used to
achieve a target residual chlorine level of 0.2 mg/L (as C12).
• E33 media adsorption. The adsorptive media system consists of three parallel 36-inch-
diameter, 72-inch-tall FRP pressure vessels, each containing about 27 ft3 of E33 media.
3.1.5.2 Treatment System Operation. The APU-150 system will be programmed to perform an
automated backwash with untreated well water either once a month or when the pressure drop across each
vessel reaches 10 psi. The vessels will be taken off-line one at a time for backwash. While one vessel is
backwashed, the other two will remain in service. CO2 will be added to the water upstream of the APU-
150 to lower the pH to approximately 7.0.
20
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Based on the average daily use rate of about 34,000 gpd, the size of adsorption vessels, and the raw water
chemistry, the E33 media has a working capacity of approximately 76,000 bed volume, and will last
approximately 35 months before change-out is necessary
3.1.6 Rimrock, AZ (E33 Media). The Rimrock, AZ water system is owned and operated by the
Arizona Water Company (AWC). The source water is extracted from Montezuma Haven Wells No. 1
and No. 2 that have a combined capacity of 90 gpm. In the summer of 2003, both wells were taken out of
service due to exceedance of the arsenic levels over the old 50-|o,g/L MCL. A new well, Well No. 3, was
drilled nearby Wells No. 1 and No. 2 with a production capacity of 315 gpm. During the site cleanup in
September 2003, Wells No. 1 and No. 2 were refurbished and developed for the demonstration study.
Later, it was discovered that Well No. 1 went dry and that Well No. 2 only produced about 40 gpm.
3.1.6.1 Treatment System Description. The AdEdge APU-100 system was originally designed for a
flowrate of 90 gpm, having two E33 vessels arranged in parallel. The system design was later modified to
a lead/lag configuration because of the loss of Well No. 1, thus resulting in a reduced system capacity to
45 gpm. The major components of the treatment system are as follows:
• Bag filter. A bag filter is installed before the APU-100 system to remove any sediment
from the well water.
• Pre-chlorination. A sodium hypochlorite solution is added to raw water to prevent
biological growth and for disinfection. The target residual chlorine level is 0.4 mg/L (as
C12) for free chlorine.
• E33 media adsorption. The APU-100 system consists of two 36-inch-diameter, 72-
inch-tall FRP pressure vessels in series, each containing about 27 ft3 of E33 media.
• Backwash recycling. Because of a lack of a sewer system for the backwash water
discharge, a 3,000-gallon high-density polyethylene (HDPE) holding tank was installed
to store the backwash water for recycling, which is accomplished by metering the water
back to the APU-100 system at a rate of 0.5 gpm.
3.1.6.2 Treatment System Operation. For the purpose of the demonstration study, Well No. 2 is
operated at about 30 gpm for 12 hours per day and is controlled by a timer. The system operates at about
30 gpm. During the system operation, the E33 vessels are backwashed automatically every 28 to 29 days
using raw water. The backwash water is filtered through a set of dual bag filters to remove particulates
and filtered water is stored in the 3,000-gallon holding tank equipped with high- and low-level sensors to
control the recycle pump.
The media replacement for this lead/lag-configured APU-100 system is similar to that of the Bow G2
system. After the spent media in the lead vessel is replaced, the vessel is moved to the lag position.
Based on the average daily use rate of 23,760 gpd, the size of adsorption vessels, and the raw water
chemistry, the E33 media has an estimated working capacity of 66,000 bed volumes, and will last for
about 19 months in the lead vessel before change-out is necessary.
3.1.7 Rollinsford, NH (E33). The Rollinsford, NH water system services about 450 connections.
The source water is supplied by three bedrock wells, two of which, Wells No. 3 and No. 4, are located at
Porter well house. Water from these two wells is combined before passing through the distribution
system and is used for the demonstration study. Both wells are operated at near 50 gpm for about 8 to 10
hours per day, depending on the water demand.
21
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The existing treatment system consists of disinfection using a dilute sodium hypochlorite solution fed at a
rate of approximately 1.3 gpd. Treated water is sent directly to the looped distribution system and stored
in a nearby storage tank.
3.1.7.1 Treatment System Description. The AdEdge APU-100 system has a design flowrate of 100
gpm. The major components of the complete water treatment system are described as follows:
• Pre-chlorination. Chlorination was initially applied as a post-chlorination process for
disinfection purposes. After approximately one month of system operation, a rise in
arsenic concentration in treated water was noted and, therefore, the chlorine injection
point was moved to upstream of the adsorption vessels to facilitate the oxidation of
As(III) and improve arsenic adsorption.
• Pre-pH adjustment. After pre-chlorination, the water pH value is adjusted to about 7.0
with CO2 via a controlled injection loop located upstream of the E33 vessels.
• E33 media adsorption. The adsorption media system consists of two parallel 36-inch-
diameter, 72-inch-tall FRP pressure vessels, each containing about 27 ft3 of E33 media.
3.1.7.2 Treatment System Operation. Since the startup of the APU-100 system in January 2004,
high pressure differential readings (over 30 psi at times) have been observed across the adsorption
vessels. Several courses of actions, including retrofitting of some system piping and valving and
aggressive backwashing, have been taken by AdEdge to address the problems. Backwash is performed
manually by the operator using untreated well water with a frequency ranging from a few days to a couple
of weeks.
Based on the source water chemistry and the average daily use rate of about 72,000 gpd, the E33 media
has an estimated working capacity of 74,000 bed volumes, which will allow the media to last for 14
months before media change-out is necessary.
3.1.8 STMGID, NV (GFH Media). The STMGID water system is operated by the Washoe
County Department of Water Resources to supply water to a population of 8,285 in Washoe County
(Reno), NV. The demonstration project was selected for treating the groundwater from its 350-gpm Well
No. 9. The existing treatment system consists of only sodium hypochlorite to provide a free chlorine
residual level of 1.0 mg/L (as C12). The chlorinated water from this well is blended with other source
waters with lower arsenic concentrations prior to supplying the distribution system. Well No. 9 is
normally operated between March 1 and October 31 during periods of high demand. It is usually turned
off by November 1 every year.
3.1.8.1 Treatment System Description. The USFilter GFH system has a design flow of 350 gpm and
consists of three pressure vessels in parallel configuration. The major components of the treatment
process include the following:
• GFH media adsorption. The GFH arsenic removal system is composed of three 66-
inch-diameter and 72-inch-tall vertical carbon steel (CS) pressure vessels, each
containing 80 ft3 of GFH media. The skid-mounted filter vessels are rated for 100 psi of
working pressure.
• Post-chlorination. Post-chlorination with sodium hypochlorite will be used for
disinfection to provide a residual chlorine level of 1.0 mg/L.
22
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3.1.8.2 Treatment System Operation. GFH media is backwashed on a headless or elapsed time
basis. The vessels will be taken off-line one at a time for backwash with treated water from the other two
vessels. The backwash water produced will be discharged to a sanitary sewer.
When the GFH media adsorption capacity is exhausted, the spent media will be removed and replaced
with virgin media. Based on the water quality characteristics and a 75% usage rate, USFilter projects that
the media change-out will take place once every 182 days. The actual run length of the media will be
determined based on the results of the one-year performance evaluation study.
3.1.9 Valley Vista, AZ (AAFS50 Media). The Valley Vista water system is privately owned by
AWC. Raw water is supplied by Well No. 2 with a capacity of 37 gpm. Prior to this demonstration
project, the treatment consisted of only sodium hypochlorite feed to reach a target residual chlorine level
at 0.6 mg/L (as C12). The operation of the well is controlled by water levels in two 20,000-gallon storage
tanks. On average, Well No. 2 is operated for approximately 8 hours per day.
3.1.9.1 Treatment System Description. The Kinetico AAFS50 system has a design flowrate of 37
gpm and consists of two pressure vessels configured in series. The major components of the complete
treatment process include the following:
• Pre-chlorination. Sodium hypochlorite was initially applied after the adsorption vessels
for disinfection. After approximately one month of the system operation, algae growth
on the vessel view glass was noted. Therefore, the chlorine injection point was moved to
before the adsorption vessels to control biological growth. The chlorine residual is
maintained at 0.4 to 0.6 mg/L (as C12) throughout the treatment train.
• pH adjustment. The system has the capability to adjust the pH of the feed water to pH
7.0 using a 37% sulfuric acid. The pH control system consists of a solenoid-driven
chemical metering pump, a 2-inch-diameter inline static mixer, an acid draw assembly
with a low-level float, a pH meter, and a 55-gallon drum containing 37% sulfuric acid.
• Adsorptive media vessels. The treatment system consists of two 36-inch-diameter, 72-
inch-tall FRP vessels, each containing 22 ft3 of the AAFS50 media. The EBCT is 4.4
minute per vessel.
3.1.9.2 Treatment System Operation. AAFS50 media is normally backwashed with treated water
once a month. While one vessel is backwashed, the other is temporarily out of service. Backwash is
semi-automatic and needs to be initiated by an operator. The backwash water produced is stored in a
1,800-gallon holding tank equipped with high/low level sensors. After solids are settled in the tank for a
preset time period, the recycle pump is turned on and the water in the holding tank is filtered through a
bag filter before being blended with the raw water at a maximum ratio of 10%.
When the arsenic removal capacity of the AAFS50 media in the lead tank is exhausted, the spent media
will be removed and virgin media will be loaded into the vessel. Based on the water quality of Well No.
2, Kinetico estimates that the AAFS50 media has a capacity of 18,680 bed volumes, which will last for
173 days, assuming that the system operates 8 hours a day and that the pH of the raw water is adjusted to
pH 7.0. When the system operates for 24 hours a day without pH adjustment, the media in the lead tank
will last for only 56 days before change-out is necessary.
3.2 Ion Exchange
3.2.1 Fruitland, ID (Purolite A-520E Resin). The Fruitland water system supplies drinking water
to approximately 4,000 citizens. Well No. 6 that has a flow capacity of 250 gpm and high arsenic and
23
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nitrate concentrations was selected for the demonstration project. Because of the high nitrate level, this
well was taken off-line several years ago. During the hydraulic testing of the new anion exchange
system, the well produced a large quantity of sediment due to a damaged casing. Because of the problem,
a new well, Well No. 6-2004, was drilled near Well No. 6 as replacement. The new well also operates at
250 gpm and contains the same high levels of arsenic and nitrates as the abandoned well.
3.2.1.1 Treatment System Description. The Kinetico IX-248-AS/N ion exchange arsenic and nitrate
removal system consists of the following components:
• Pre-filtration. The source water passes through a skid-mounted cartridge filtration
system equipped with five 20-|om bag filters. This filtration step prevents the resin bed
from being fouled by particulates.
• Ion exchange system. The ion exchange system consists of two parallel 48-inch-
diameter, 72-inch-tall FRP pressure vessels, each contains 50 ft3 (in 4-ft depth) of
Purolite A-520E strong base anion exchange resin, 3 ft3 of flint gravel support media, and
3 ft3 of polypropylene filler beads. The skid-mounted vessels are rated for 150 psi
working pressure, and piped to a valve rack mounted on a welded steel frame. Each
vessel is equipped with a 125-gpm flow-limiting device. A brine saturator and a 2-hp,
60-gallon vertical air compressor also are included with the system.
3.2.1.2 Treatment System Operation. The Kinetico arsenic/nitrate removal system is a fully
automated system that has an operator interface, programmable logic controller (PLC), and a modem
housed in a control panel. The control panel is connected to various instruments used to track the system
performance, including flowrate and the volume of water treated since the last regeneration.
The system is regenerated based upon nitrate breakthrough, which is estimated to be at 400 to 500 bed
volumes of water treated. Regeneration occurs one vessel at a time, thus temporarily reducing the service
flowrate to 125 gpm. Regeneration is performed in a co-current mode using aNaCl brine solution stored
in a nearby holding tank. The regeneration process is controlled by the system PLC, which is
programmed to initiate the regeneration sequence after a given volume throughput (this volume is
determined by sampling the process effluent during the system startup). The regeneration process
includes three consecutive steps: brine draw, slow rinse, and fast rinse. The salt usage rate is estimated to
be 3.19 lb/1,000 gallons of water treated.
3.3 Coagulation/Filtration
3.3.1 Climax, MN. The City of Climax supplies drinking water to 264 community members. The
source water is supplied by two 141 ft-deep wells, each having a flow capacity of 160 and 140 gpm.
However, only one well is in use at any one time with the two wells alternating on a monthly basis. Both
wells can be used during fire emergencies with a full capacity of 300 gpm. Prior to this demonstration
project, the treatment system consisted of only a chlorine gas feed to reach a target residual chlorine level
of 0.6 mg/L. The water also is fluoridated to a target level of 1.8 mg/L.
3.3.1.1 Treatment System Description. Kinetico's coagulation/filtration system is a skid-mounted
system consisting of two coagulation contact tanks and two pressure filtration tanks. The major
components are described as follows:
• Pre-chlorination. The existing chlorine gas system is used to provide disinfection and
oxidation of As(III) and Fe(II).
24
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• Coagulation. Two 345-gallon, 42-inch-diameter, 72-inch-tall FRP contact tanks
arranged in parallel provide 5 minutes of contact time each to facilitate the formation of
iron floes prior to filtration.
• Macrolite® filtration. Two pressure filtration vessels are arranged in parallel. Both FRP
filtration vessels are 36 inches in diameter and 72 inches in height with 6-inch top and
bottom flanges, and are mounted on a polyurethane coated, steel frame. Each vessel is
filled with approximately 24 inches (14 ft3) of 40/60 mesh Macrolite® media, which is
underlain with a fine garnet fill layered 1 inch above the 0.006-inch slotted SS wedge-
wire underdrain. The flow through each vessel is regulated to 70 gpm using a flow-
limiting device to prevent filter overrun or damage to the system. The normal system
operation with both tanks on-line provides a total system flow of 140 gpm.
3.3.1.2 Treatment System Operation. The system is fully automated with an operator interface,
PLC, and a modem housed in a central NEMA 4 control panel. The control panel is connected to various
instruments used to track system performance including inlet and outlet pressure after each filter, system
flowrate, backwash flowrate, and backwash turbidity.
At a 10 gpm/ft2 loading rate and 24 inches of depth, the pressure drop across a clean Macrolite® filter bed
is usually about 15 psi. The filters are automatically backwashed in upflow mode when the pressure drop
across the bed reaches 25 to 30 psi. The backwash process involves multiple steps: the water is first
drained from the filtration vessel and the filter is then sparged with air at 100 psig. After a brief settling
period, the filtration vessel is backwashed with treated water at a flowrate of approximately 55 gpm. The
backwash is performed one vessel at a time and the resulting wastewater is sent to the sanitary sewer
through a 2-inch-diameter polyvinyl chloride (PVC) line. After backwash, the filtration vessel undergoes
a filter-to-waste cycle before returning to feed service.
3.3.2 Lidgerwood, ND. The Lidgerwood water treatment system supplies drinking water to
approximately 750 community members. The system capacity is 250 gpm for a peak daily demand of
180,000 gpd. The source water is pumped from two wells with the wells alternating every month. The
total arsenic concentrations of the source water range from 38 to 146 |o,g/L. An arsenic speciation test
performed in July 2003 found arsenic (146.2 (ig/L) to be predominately As(III) (82%). The current
treatment process relies on the oxidation of As(III) to As(V) and the adsorption and co-precipitation of
As(V) onto iron solids. The source water has iron levels ranging from 1,310 to 1,620 (ig/L. Historic
analytical results indicate that iron levels typically are 9 to 11 times higher than the arsenic levels in the
source water. The treated water results confirm that incomplete arsenic removal is occurring, with arsenic
concentrations in the gravity filtration cell effluent being measured at 25 to 31 (ig/L.
Treated water is stored in a clearwell before distribution. Two clearwells are located underneath the
treatment building, including the original 16,000-gallon clearwell installed in 1984 and used as a source
of clean backwash water, and the second 30,000-gallon clearwell installed in 1989 and used for
distribution water. A 50,000-gallon water tower is included as part of the distribution for water storage.
3.3.2.1 Treatment System Description. The Lidgerwood treatment system consists of pre-
chlorination, forced-draft aeration, KMnO4 oxidation, polymer coagulant addition, detention, gravity
filtration, post-chlorination, and fluoridation. A brief description of each treatment step is provided
below:
• Pre-chlorination. A chlorine gas feed system is used for pre-chlorination of the
source water to 1.8 mg/L as C12. Pre-chlorination helps prevent biological
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growth in the filters and other system components. Chlorine also oxidizes iron,
manganese, and arsenic in the groundwater.
• Aeration. Forced-draft aeration is used to promote the transfer of oxygen in air
to the extracted groundwater in order to oxidize iron and manganese.
• KMnO4 oxidation. A supplementary oxidation step is provided by the addition
of KMnO4, which is stored in a 50-gallon tank and added at a dosage of
approximately 0.6 to 0.7 mg/L. The potassium permanganate is used to
continuously regenerate the MnO2-coated anthrasand in the filter cells.
• Mixing and detention. Polymer coagulant is stored in a 50-gallon tank and
added to the rapid mix tank just prior to the baffled detention tank. The baffled
detention tank has a capacity of 15,000 gallons, allowing for about 60 minutes of
contact time before gravity filtration.
• Filtration. The particulate matter in the water is removed using four gravity
filter cells with a total cross-sectional area of 120 ft2 that are filled with 20 x 40
mesh MnO2-coated anthrasand. The hydraulic loading to the filters is
approximately 2 gpm/ft2. The anthrasand was most recently changed out in
October 2002.
• Post-chlorination and fluoridation. For post-chlorination, the free chlorine is
targeted at 0.08 mg/L and the total chlorine residual is targeted at 1.9 mg/L. In
addition, fluoride also is added to treated water prior to distribution.
3.3.2.2 Treatment System Operation. The treatment system operates 5 to 6 hours per day depending
on water usage, and backwashing of the filters is performed on a regular schedule every Monday,
Wednesday, and Friday or more frequently as needed. The system is equipped with a backwash recycling
system. The backwash flowrate is about 240 gpm with an air scour pressure of 3.5 Ib. Each backwash
cycle usually lasts for 15 minutes per cell with 5 minutes of air and water supply and 10 minutes of water
supply only. The backwash water produced from each backwash cycle is allowed to settle in a 18,000-
gallon backwash recovery basin for about 6 hours before the supernatant is reclaimed to the mixing tank
at a flowrate of 50 gpm. The sludge accumulated in the bottom of the backwash tank is pumped to a 20-
ft-diameter by 9-ft, 5-inch-tall sludge holding tank and then collected for landfill disposal once every
other year.
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4.0 REFERENCES
Amy, G., Chen, H.W., von Gunten, U., Jekel, M., Banerjee, K. 2004. "Media Performance: Laboratory
Studies (Impact of Water Quality Parameters on Adsorbent Treatment Technologies for Arsenic
Removal)." Workshop on the Design and Operation of Adsorptive Media Processes for the
Removal of Arsenic from Drinking Water. Cincinnati, OH, August 10-11, 2004.
Clifford, D. 1999. "Ion Exchange and Inorganic Adsorption." In American Water Works Association
(Eds.), Water Quality and Treatment: A Handbook of Community Water Supplies, 5th ed.
McGraw-Hill, NY.
Edwards, M., S. Patel, L. McNeill, H. Chen, M. Frey, A.D. Eaton, RC. Antweiler, and H.E. Taylor.
1998. "Considerations in As Analysis and Speciation." J. AWWA (3): 103-113.
EPA, see United States Environmental Protection Agency.
Freeze, R.A., and J.A. Cherry. 1979. Groundwater. Prentice Hall, Englewood Cliffs, NJ.
Jain, A., and R.H. Loeppert. 2000. "Effect of Competing Anions on the Adsorption of Arsenate and
Arsenite by Ferrihydrite." J. Environ. Qual. 29: 1422-1430.
Kinetico. 2003. Vendor Proposal to U.S. EPA Program Treatment Technologies for Arsenic Removal
for Small Drinking Water Systems.
Rubel, F. 1984. Concept Design Report of Arsenic Removal Water Treatment Plants at Fallon, Nevada.
Department of the Navy, Contract No. N62474-81-C-8532. May 14.
Sorg, T.J. 2002. "Iron Treatment for Arsenic Removal Neglected." Opflow, AWWA, 28(11): 15.
United States Environmental Protection Agency. 2000. Arsenic Removal from Drinking Water by Ion
Exchange and Activated Alumina Plants. EPA/600/R-00/088. October 2000.
United States Environmental Protection Agency. 200 la. Federal Register: Final Arsenic Rule. 40 CFR
Parts 9, 141, and 142.
United States Environmental Protection Agency. 200 Ib. National Primary Drinking Water Regulations:
Arsenic and Clarifications to Compliance and New Source Contaminants Monitoring. Fed.
Register., 66:14:6975. January 22.
United States Environmental Protection Agency. 2002. Implementation Guidance for the Arsenic Rule-
Drinking Water Regulations for Arsenic and Clarifications to Compliance and New Source
Contaminants Monitoring. EPA/816/K-02/018. U.S. EPA Office of Water, Washington, DC.
United States Environmental Protection Agency. 2003a. Minor Clarification of the National Primary
Drinking Water Regulation for Arsenic. Federal Register, 40 CFR Part 141. March 25.
United States Environmental Protection Agency. 2003b. Design Manual: Removal of Arsenic from
Drinking Water by Adsorptive Media. EPA/600/R-03/019. March 2003.
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United States Environmental Protection Agency. 2004a. Design Manual Removal of Arsenic from
Drinking Water Supplies by Iron Removal Process. Publication pending.
United States Environmental Protection Agency. 2004b. Capital Costs of Arsenic Removal
Technologies: U.S. EPA Arsenic Removal Technology Demonstration Program Round 1.
Publication pending.
Welch, A.H., D.B. Westjohn, D. Helsel, and R. Wanty. 2000. "Arsenic in Ground Water of the United
States: Occurrence and Geochemistry." Ground Water, 38(4): 589-604.
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Appendix A
Photographs of Arsenic Removal Treatment Systems
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Figure A-l. Bow, NH Treatment System
A-l
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Figure A-2. Desert Sands MDWCA, NM Treatment System
A-2
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Figure A-3. Brown City, MI Treatment System
A-3
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Figure A-4. Queen Anne's County, MD Treatment System
A-4
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Figure A-5. Nambe Pueblo, NM Treatment System
(Photograph Taken before Shipment)
A-5
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Figure A-6. Rimrock, AZ Treatment System
A-6
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Figure A-7. Rollinsford, NH Treatment System
A-7
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Figure A-8. Valley Vista, AZ Treatment System
A-8
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Figure A-9. STMGID, NV Treatment System
(Photograph Taken in the Shop)
A-9
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Figure A-10. Climax, MN Treatment System
A-10
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Figure A-ll. Fruitland, ID Treatment System
A-ll
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Figure A-12. Lidgerwood, ND System Modification (Iron Addition System)
A-12
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