8 Water Research Foundation Bench Scale Removal Options for Hex Chrome_20170726

1 Water
Research
Foundation -
advancing the science of water
Bench -Scale Evaluation of
Alternative Cr(VI) Removal
Options for Small Systems
Project #4561

Bench -Scale Evaluation of
Alternative Cr(VI) Removal
Options for Small Systems

m Water
Research
Foundation
advancing the science of water
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Bench -Scale Evaluation of
Alternative Cr(VI) Removal
Options for Small Systems
Prepared by:
Jeffrey L. Parks, Anurag Mantha, and Marc Edwards
Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
Sunil Kommineni and Yongki Shim
KIT Professionals, Inc., Houston, TX 77042
and
Katie Porter and Greg Imamura
Arcadis US, Inc., Irvine, CA 92618
Sponsored by:
Water Research Foundation
6666 West Quincy Avenue, Denver, CO 80235
Published by:
��1 Water
Research
� Foundation-

DISCLAIMER
This study was funded by the Water Research Foundation (WRF). WRF assumes no
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Copyright © 2017
by Water Research Foundation
ALL RIGHTS RESERVED.
No part of this publication may be copied, reproduced
or otherwise utilized without permission.
ISBN 978-1-60573-286-2
Printed in the U.S.A.

1601LI _Y_MY_ -.1
LISTOF TABLES........................................................................................................................ vii
LISTOF FIGURES....................................................................................................................... xi
FOREWORD................................................................................................................................ xv
ACKNOWLEDGMENTS.......................................................................................................... xvii
EXECUTIVE SUMMARY......................................................................................................... xix
CHAPTER 1: INTRODUCTION................................................................................................... 1
Background and Project Motivation................................................................................... 1
Treatment Techniques for Cr(VI)....................................................................................... 1
Overview of Previous Research.......................................................................................... 2
Research Approach for this Study...................................................................................... 3
Task 1 — Bench -Scale Screening Tests................................................................... 4
Task 2 — Small -Scale Column Tests....................................................................... 5
Task 3 — Practical Application of Results............................................................... 5
CHAPTER 2: SCREENING OF ION EXCHANGE RESINS AND MEDIA ............................... 7
Ion Exchange Resins and Media Included in this Study ..................................................... 7
ParticipatingUtilities.......................................................................................................... 8
AnalyticalMethods............................................................................................................. 8
MetalsConcentrations............................................................................................ 8
Hexavalent Chromium Concentration.................................................................... 8
Anionic Species Concentrations............................................................................. 8
Total Organic Carbon Concentration...................................................................... 8
Alkalinity................................................................................................................ 8
Development of Adsorption Isotherms............................................................................... 9
Water Quality Characteristics................................................................................. 9
Cr(VI) Removal Results for Iron -Based Media ....................................................
10
Cr(VI) Removal Results for Strong Base Anionic (SBA) Resins ........................
12
Cr(VI) Removal Results for Weak Base Anionic (WBA) Resins ........................
13
Effect of Media on Other Water Quality Parameters ............................................
14
Results for Adsorption Isotherm Parameters........................................................
16
Effect of Competing Solutes on Hexavalent Chromium Removal ...................................
19
Sulfate...................................................................................................................
19
Silicon...................................................................................................................
21
Chloride.................................................................................................................
22
Alkalinity..............................................................................................................
24
OrganicCarbon.....................................................................................................
25
Nitrate...................................................................................................................
27
v

CHAPTER 3: WATER QUALITY IMPACTS ON RESINS AND MEDIA
PERFORMANCE............................................................................................................. 29
Materialsand Methods...................................................................................................... 29
Small -Scale Column Tests.................................................................................... 29
LeachingTests...................................................................................................... 30
Results............................................................................................................................... 31
Baseline Test (Gravity Fed).................................................................................. 31
High Sulfate Test (Gravity Fed)........................................................................... 31
Medium Sulfate Test (Pressure System)............................................................... 32
Medium Sulfate Test with Added Nitrate and Arsenic (Pressure System)........... 33
Medium Sulfate Test Repeated with Added Nitrate and Arsenic (Pressure
System)..................................................................................................... 36
High Sulfate Test with Added Nitrate and Arsenic (Pressure System) ................ 41
Low Sulfate Test with Added Nitrate and Arsenic (Pressure System) ................. 46
Summary of Chromatographic Peaking Results ................................................... 50
TCLPTest............................................................................................................. 50
California Waste Extraction Test.......................................................................... 51
CHAPTER 4: FULL SCALE APPLICATIONS GUIDANCE .................................................... 53
Candidate Treatment Technologies.................................................................................. 53
Weak Base Anion (WBA) Exchange.................................................................... 53
Strong Base Anion (SBA) Exchange.................................................................... 64
Granular Iron Media (GIM).................................................................................. 91
Reverse Osmosis(RO).......................................................................................... 93
Reduction Coagulation Filtration (RCF).............................................................. 94
CHAPTER 5: HEXAVALENT CHROMIUM TREATMENT DESIGN AND COSTING
TOOL................................................................................................................................ 97
InputParameters............................................................................................................... 97
ProcessSelection.............................................................................................................. 98
Description of Calculations............................................................................................. 100
CHAPTER 6: SUMMARY AND CONCLUSIONS.................................................................. 103
Summary......................................................................................................................... 103
Conclusions..................................................................................................................... 103
CHAPTER 7: RECOMMENDATIONS..................................................................................... 107
Recommendations for Future Work................................................................................ 107
Recommendations for Utilities....................................................................................... 107
REFERENCES........................................................................................................................... 109
ABBREVIATIONS.................................................................................................................... III
vi

TABLES
1.1 Experimental concentrations of competing solutes.................................................................. 5
2.1 Media tested.............................................................................................................................. 7
2.2 Raw water quality parameters................................................................................................. 10
2.3 Cr(VI) removal using iron -based media................................................................................. 11
2.4 Cr(VI) removal using SBA media.......................................................................................... 13
2.5 Cr(VI) removal using WBA media......................................................................................... 14
2.6 Sulfate, chloride, and nitrate concentrations after 24 hours of contact time ........................... 15
2.7 Silicon, iron, manganese, uranium, and arsenic concentrations after 24 hours of contact
time................................................................................................................................... 16
2.8 Summary of Freundlich isotherm parameters......................................................................... 18
2.9 Nominal concentrations of competing solutes tested in this study ......................................... 19
3.1 Summary of chromatographic peaking of arsenic and nitrate ................................................ 50
3.2 TCLP chromium concentrations............................................................................................. 51
3.3 TCLP results expressed in terms of media loading................................................................ 51
4.1 Strengths and weaknesses of WBA process........................................................................... 55
4.2 WBA treatment design criteria............................................................................................... 55
4.3 Capital cost opinion for 0.5 MGD Cr(VI) treatment using WBA resin .................................. 60
4.4 Capital cost opinion for 1 MGD Cr(VI) treatment using WBA resin ..................................... 61
4.5 Capital cost opinion for 2 MGD Cr(VI) treatment using WBA resin ..................................... 62
4.6 O&M cost opinion for Cr(VI) treatment using WBA resin .................................................... 63
4.7 Strengths and weaknesses of SBA process............................................................................. 66
4.8 Design criteria for SBA resin treatment using single -pass series operation for low sulfate
(< 50 mg/L) waters........................................................................................................... 67
vii

4.9 Design criteria for SBA resin treatment using series operation with onsite regeneration
for low -moderate sulfate (1 — 150 mg/L) waters.............................................................. 67
4.10 Design criteria for SBA resin treatment using parallel operation with onsite
regeneration....................................................................................................................... 68
4.11 Capital cost opinion for 0.5 MGD Cr(VI) treatment using SBA resin, single use, series
operation for low sulfate (< 50mg/L) waters.................................................................... 79
4.12 Capital cost opinion for 1 MGD Cr(VI) treatment using SBA resin, single use, series
operation for low sulfate (< 50 mg/L) waters................................................................... 80
4.13 Capital cost opinion for 2 MGD Cr(VI) treatment using SBA resin, single use, series
operation for low sulfate (< 50 mg/L) waters................................................................... 81
4.14 Capital cost opinion for 0.5 MGD Cr(VI) treatment using SBA resin, series operation
with onsite regeneration for low -moderate sulfate (1 — 150 mg/L) waters ....................... 82
4.15 Capital cost opinion for 1 MGD Cr(VI) treatment using SBA resin, series operation
with onsite regeneration for low -moderate sulfate (1 — 150 mg/L) waters ....................... 83
4.16 Capital cost opinion for 2 MGD Cr(VI) treatment using SBA resin, series operation with
onsite regeneration for low -moderate sulfate (1 — 150 mg/L) waters ............................... 84
4.17 Capital cost opinion for 0.5 MGD Cr(VI) treatment using SBA resin, parallel operation
with onsite regeneration.................................................................................................... 85
4.18 Capital cost opinion for 1 MGD Cr(VI) treatment using SBA resin, parallel operation
withonsite regeneration.................................................................................................... 86
4.19 Capital cost opinion for 2 MGD Cr(VI) treatment using SBA resin, parallel operation
with onsite regeneration.................................................................................................... 87
4.20 O&M cost opinion for Cr(VI) treatment using SBA resin, single use, series operation
for low sulfate (< 50 mg/L) waters................................................................................... 88
4.21 O&M cost opinion for Cr(VI) treatment using SBA resin, series operation with onsite
regeneration for low -moderate sulfate (1 — 150 mg/L) waters ......................................... 89
4.22 O&M cost opinion for Cr(VI) treatment using SBA resin, parallel operation with onsite
regeneration....................................................................................................................... 90
4.23 Strengths and weaknesses of GIM process........................................................................... 92
4.24 Strengths and weaknesses of RO treatment process............................................................. 94
viii

4.25 Strengths and weaknesses of RCF process........................................................................... 96
ix

FIGURES
2.1 Visible iron particles after 24 hours of contact with Cleanit®-LC media .............................. 12
2.2 Visible iron particles after 24 hours of contact with SMI media ............................................ 12
2.3 Hexavalent chromium concentration after 30 minutes of contact time with varying
concentrations of sulfate................................................................................................... 20
2.4 Hexavalent chromium concentration after 4 hours of contact time with varying
concentrations of sulfate................................................................................................... 20
2.5 Hexavalent chromium concentration after 30 minutes of contact time with varying
concentrationsof silicon................................................................................................... 21
2.6 Hexavalent chromium concentration after 4 hours of contact time with varying
concentrations of silicon................................................................................................... 22
2.7 Hexavalent chromium concentration after 30 minutes of contact time with varying
concentrations of chloride................................................................................................. 23
2.8 Hexavalent chromium concentration after 4 hours of contact time with varying
concentrations of chloride................................................................................................. 23
2.9 Hexavalent chromium concentration after 30 minutes contact time with varying levels of
alkalinity........................................................................................................................... 24
2.10 Hexavalent chromium concentration after 4 hours of contact time with varying levels of
alkalinity........................................................................................................................... 25
2.11 Hexavalent chromium concentration after 30 minutes of contact time with varying levels
ofTOC.............................................................................................................................. 26
2.12 Hexavalent chromium concentration after 4 hours of contact time with varying levels of
TOC................................................................................................................................... 26
2.13 Hexavalent chromium concentration after 30 minutes of contact time with varying levels
ofnitrate............................................................................................................................ 27
2.14 Hexavalent chromium concentration after 4 hours of contact time with varying levels of
nitrate................................................................................................................................ 28
3.1 Photo of small-scale column test setup................................................................................... 30
3.2 Hexavalent chromium concentration in effluent during the 150 mg/L sulfate test ................ 32
xi

3.3 Hexavalent chromium concentration in effluent during the 60 mg/L sulfate test .................. 33
3.4 Sulfate concentration in effluent during the 60 mg/L sulfate test ........................................... 33
3.5 Hexavalent chromium concentration in effluent during the 60 mg/L sulfate test with 8
µg/L arsenic and 8 mg/L nitrate........................................................................................ 34
3.6 Sulfate concentration in the effluent during the 60 mg/L sulfate test with 8 µg/L arsenic
and8 mg/L nitrate............................................................................................................. 35
3.7 Arsenic concentration in the effluent during the 60 mg/L sulfate test with 8 µg/L arsenic
and8 mg/L nitrate............................................................................................................. 35
3.8 Nitrate concentration in the effluent during the 60 mg/L sulfate test with 8 µg/L arsenic
and8 mg/L nitrate............................................................................................................. 36
3.9 Hexavalent chromium concentration in effluent during the repeat 60 mg/L sulfate test
with 8 µg/L arsenic and 8 mg/L nitrate............................................................................. 37
3.10 Sulfate concentration in the effluent during the repeat 60 mg/L sulfate test with 8 µg/L
arsenic and 8 mg/L nitrate................................................................................................. 38
3.11 Arsenic concentration in the effluent during the repeat 60 mg/L sulfate test with 8 mg/L
nitrateand 8 µg/L arsenic................................................................................................. 38
3.12 Nitrate concentration in the effluent during the repeat 60 mg/L sulfate test with 8 µg/L
arsenic and 8 mg/L nitrate................................................................................................. 39
3.13 Nitrate, arsenic, and sulfate peaking for ResinTech SBG1 (60 mg/L sulfate small-scale
columntest)....................................................................................................................... 40
3.14 Nitrate, arsenic, and sulfate peaking for Purolite A600E/9149 (60 mg/L sulfate small-scale
columntest)....................................................................................................................... 40
3.15 Nitrate, arsenic, and sulfate peaking for Purolite S 106 (60 mg/L sulfate small-scale
columntest)....................................................................................................................... 41
3.16 Hexavalent chromium concentration in effluent during the 150 mg/L sulfate test with 8
µg/L arsenic and 8 mg/L nitrate........................................................................................ 42
3.17 Arsenic concentration in effluent during the 150 mg/L sulfate test with 8 mg/L nitrate
and8 µg/L arsenic............................................................................................................. 42
3.18 Nitrate concentration in effluent during the 150 mg/L sulfate test with 8 µg/L arsenic
and8 mg/L nitrate............................................................................................................. 43
xii

3.19 Sulfate concentration in effluent during the 150 mg/L sulfate test with 8 µg/L arsenic
and8 mg/L nitrate............................................................................................................. 43
3.20 Nitrate, arsenic, and sulfate peaking for the ResinTech SBG1 (150 mg/L sulfate
small-scale column test).................................................................................................... 44
3.21 Nitrate, arsenic, and sulfate peaking for Purolite A600E/9149 (150 mg/L sulfate
small-scale column test).................................................................................................... 45
3.22 Nitrate, arsenic, and sulfate peaking for the Purolite S106 (150 mg/L sulfate small-scale
columntest)....................................................................................................................... 45
3.23 Arsenic concentration in the effluent during the 20 mg/L sulfate test with 8 mg/L nitrate
and8 µg/L arsenic............................................................................................................. 46
3.24 Nitrate concentration in effluent during the 20 mg/L sulfate test with 8 mg/L nitrate and
8 µg/L arsenic................................................................................................................... 47
3.25 Sulfate concentration in effluent during the 20 mg/L sulfate test with 8 mg/L nitrate and
8 µg/L arsenic................................................................................................................... 47
3.26 Nitrate, arsenic, and sulfate peaking for ResinTech SBG1 (20 mg/L sulfate small-scale
columntest)....................................................................................................................... 48
3.27 Nitrate, arsenic, and sulfate peaking for Purolite A600E/9149 (20 mg/L sulfate small-scale
columntest)....................................................................................................................... 49
3.28 Nitrate, arsenic, and sulfate peaking for Purolite S 106 (20 mg/L sulfate small-scale
columntest)....................................................................................................................... 49
4.1 WBA resin treatment process flow diagram........................................................................... 54
4.2 Conceptual footprint for 0.5 MGD capacity Cr(VI) treatment using WBA resin .................. 57
4.3 Conceptual footprint for 1 MGD capacity Cr(VI) treatment using WBA resin ..................... 58
4.4 Conceptual footprint for 2 MGD capacity Cr(VI) treatment using WBA resin ..................... 59
4.5 SBA resin treatment process flow diagram — single use, series operation for low sulfate
(< 50 mg/L) waters........................................................................................................... 65
4.6 SBA resin treatment process flow diagram, series operation with onsite regeneration for
low -moderate sulfate (1 — 150 mg/L) waters.................................................................... 65
4.7 SBA resin treatment process flow diagram, parallel operation with onsite regeneration....... 66

4.8 Conceptual footprint for 0.5 MGD capacity Cr(VI) treatment using SBA resin, single use,
series operation for low sulfate (< 50 mg/L) waters......................................................... 70
4.9 Conceptual footprint for 1 MGD capacity Cr(VI) treatment using SBA resin, single use,
series operation for low sulfate (< 50 mg/L) waters......................................................... 71
4.10 Conceptual footprint for 2 MGD capacity Cr(VI) treatment using SBA resin, single use,
series operation for low sulfate (< 50 mg/L) waters......................................................... 72
4.11 Conceptual footprint for 0.5 MGD capacity Cr(VI) treatment using SBA resin, series
operation with onsite regeneration for low -moderate sulfate (1 — 150 mg/L) waters ...... 73
4.12 Conceptual footprint for 1 MGD capacity Cr(VI) treatment using SBA resin, series
operation with onsite regeneration for low -moderate sulfate (1 — 150 mg/L) waters ...... 74
4.13 Conceptual footprint for 2 MGD capacity Cr(VI) treatment using SBA resin, series
operation with onsite regeneration for low -moderate sulfate (1 — 150 mg/L) waters ...... 75
4.14 Conceptual footprint for 0.5 MGD capacity Cr(VI) treatment using SBA resin, parallel
operation with onsite regeneration.................................................................................... 76
4.15 Conceptual footprint for 1 MGD capacity Cr(VI) treatment using SBA resin, parallel
operation with onsite regeneration.................................................................................... 77
4.16 Conceptual footprint for 2 MGD capacity Cr(VI) treatment using SBA resin, parallel
operation with onsite regeneration.................................................................................... 78
4.17 Granular Iron Media (GIM) treatment process flow diagram .............................................. 91
4.18 Reverse Osmosis (RO) system process flow diagram.......................................................... 93
4.19 Reduction Coagulation Filtration (RCF) system process flow diagram ............................... 95
5.1 Cr(VI) treatment design and costing tool input form.............................................................. 98
5.2 Cr(VI) treatment process selection flowchart ......................................................................... 99
5.3 Capital, O&M, and total cost computations flowchart ......................................................... 100
5.4 Residuals and plant footprint flowchart ................................................................................ 102
xiv

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xv

ACKNOWLEDGMENTS
The authors of this report are indebted to the cooperation and participation of the utilities
and media suppliers that were involved in this project. The utilities will remain anonymous and
are designated as Utilities A-E throughout the report. Media suppliers included ResinTech (West
Berlin, NJ), Purolite (Bala Cynwyd, PA), North American Hoganas (Hollsopple, PA), and SMI-
PS (Lincoln, CA).
The authors would also like to thank Mary Smith, Water Research Foundation project
manager, and the members of the Project Advisory Committee: Erin Mackey of Brown and
Caldwell (Walnut Creek, CA), Haizhou Liu of UC-Riverside, and Peter McCafferty of
ChemCentre (Bentley WA, Australia).

EXECUTIVE SUMMARY
OBJECTIVES
The primary objective of this study is to provide guidance to utilities needing to treat water
containing greater than 10 µg/L of hexavalent chromium at a flow of 2 million gallons per day
(MGD) or fewer. This guidance includes the effect of various water quality parameters, such as
sulfate, nitrate, and arsenic concentrations, on treatment efficacy; preliminary site layouts for the
most appropriate treatment scheme; and high-level budgetary cost opinions on the selected
treatment scheme.
BACKGROUND
Chromium is an inorganic contaminant that has received a large amount of media attention
over the past 15 years, primarily as a result of legal ramifications of industrial contamination of
groundwater near Hinkley, California. As described below, however, there are many areas where
chromium is present as a result of the regional geology. In aqueous systems, chromium typically
exists in two different oxidation states: the trivalent form (Cr[III]), and the potentially carcinogenic
hexavalent form (Cr[VI]). The U.S. Environmental Protection Agency (EPA) currently has a
maximum contaminant level (MCL) for total chromium species (Cr[III] plus Cr[VI]) of 100 µg/L
(0.1 mg/L), but does not regulate Cr(VI) separately. In July 2011, however, the State of California
established a public health goal (PHG) for Cr(VI) of 0.02 µg/L and has instituted an MCL of 10
µg/L that took effect on July 1, 2014. The EPA is also considering a national standard for Cr(VI),
but must issue its final human health assessment before determining if a regulation is warranted.
Cr(VI) occurrence in the United States outside of California has recently been studied more
thoroughly (Seidel et al. 2012). Most recently, the EPA's third Unregulated Contaminant
Monitoring Rule (UCMR 3) was signed into effect in April 2012 and required many utilities to
monitor 30 contaminants during the years 2013-2015 (EPA 2013). Recently released data indicate
that the vast majority of sites with Cr(VI) greater than 10 µg/L are groundwater utilities located in
EPA Regions 6 and 9 and include the states of Oklahoma, Arizona, and California. In fact, the
only other locations of those surveyed greater than 10 µg/L were in Puerto Rico. Only 2.3% of the
samples collected during that time exceeded the MCL of 10 µg/L; however, there are many small
systems that did not participate in this study and will likely be affected when the California or
national standard goes into effect. The objective of this study was to provide guidance on selecting
and implementing Cr(VI) treatment technologies for smaller systems requiring wellhead treatment
since these systems may not have the same options as larger utilities with more capital.
APPROACH
A bench -scale study of the removal of hexavalent chromium from drinking water was
conducted with the primary focus on affordable treatment technologies for water utilities needing
to treat 2 MGD or fewer. Four ion exchange media, including two SBA (strong base anion) media,
two WBA (weak base anion) media, and two iron -based media were evaluated. The performance
of each media type was assessed in water supplied by five participating utilities that represented a
range of concentrations of various water quality parameters. The media performance was also
xix

evaluated when competing solutes were present. These included sulfate, nitrate, chloride, silicon,
alkalinity, and natural organic matter.
After careful evaluation of all bench -scale results, three media were selected for further
testing in small-scale columns. These media included the two SBA media (ResinTech SBG1 and
Purolite A600E/9149) and the Purolite S 106 WBA media. Synthetically prepared water was
pumped into the top of each column in a down -flow configuration. Column diameter was 1/2 inch,
and media height was 8 inches (20 cm). A two -minute empty bed contact time (EBCT) was used
for all tests. Each column test was run until breakthrough of Cr(VI) (set at 8 µg/L-80% of the CA
MCL) occurred or until the pressure head became too great to maintain the flow. The tests included
various levels of sulfate (20, 60, and 150 mg/L), with or without additional arsenic and nitrate.
Arsenic and nitrate were added to some tests to evaluate whether a phenomenon called
chromatographic peaking occurred and whether it could be a concern for utilities.
Chromatographic peaking occurs when one ion at high concentration displaces another ion that is
also removed by the ion exchange media, resulting in an effluent concentration even greater than
the influent concentration. TCLP and California WET tests were conducted on the spent media
from these tests to provide further information on what to expect during media disposal.
Results from the bench -scale testing and the small-scale column testing were used to
develop practical guidance for selecting a treatment technology for smaller utilities. A Microsoft
Excel spreadsheet tool was created, as well as conceptual treatment footprints and budgetary -level
cost opinions.
RESULTS/CONCLUSIONS
All media tested were able to remove Cr(VI) to levels well below the California MCL;
however, other water quality parameters played an important role in determining the most
appropriate treatment.
The iron -based media removed Cr(VI) to extremely low levels in almost all water
chemistries tested, including when competing ions were present. However, the release of iron from
the media would likely require an additional iron removal treatment process. For this reason, these
media were not evaluated during the column testing portion of this study. However, in situations
where waste disposal might be an issue, the Cleanit®-LC media should be considered.
Although a number of inorganic constituents are critical when evaluating whether SBA is
suitable, SBA media life was highly dependent on influent sulfate concentration. WBA is a more
robust treatment technology, as sulfate concentration has little effect on performance, but this
technology is more complex to operate (primarily due to the pH adjustment required).
• Both SBA and WBA removed sulfate from the influent water while releasing chloride.
• SBA removed nitrate from influent water more efficiently than WBA.
• Both SBA and WBA removed uranium and arsenic, but had no effect on the silicon
concentration.
• Freundlich isotherms proved to be excellent models for Cr(VI) removal from utility -
supplied waters with both the SBA and WBA resins.
• Cr(VI) removal decreased as sulfate concentration was increased with both the SBA
and WBA media.
• Cr(VI) removal decreased as the silicon concentration was increased with the SBA
media, but there was no effect while using WBA.
xx

• The nitrate concentration had no effect on Cr(VI) removal using SBA until a
concentration of 5 mg/L as N was reached, at which point Cr(VI) decreased. Nitrate
concentration adversely affected Cr(VI) while using WBA.
• No consistent trends were observed in Cr(VI) removal when chloride, alkalinity, or
NOM concentrations were varied but sulfate and nitrate were held constant.
During the small-scale column tests, sulfate concentration greatly affected the time to
breakthrough.
• With 20 mg/L sulfate, no breakthrough of Cr(VI) was observed during the test (5000
bed volumes [BVs]) for any of the media tested; in fact, Cr(VI) never increased above
1 µg/L in the column effluent.
• With 60 mg/L sulfate, breakthrough (8 µg/L) of Cr(VI) for SBA occurred at around
6000 BVs. Cr(VI) increased to 7 µg/L at 7000 BVs for WBA.
• With 150 mg/L sulfate, breakthrough of Cr(VI) for SBA occurred around 2500 BVs.
Cr(VI) increased to 6 µg/L at 7000 BVs for WBA, although a brief period between
1600-2200 BVs saw an increase in Cr(VI) above 8 µg/L.
Higher sulfate concentrations can cause chromatographic peaking of nitrate or arsenic
above their respective MCLs if those elements are present in high enough concentrations in the
influent water.
• Huge arsenic peaks (3.6-4.6x influent) can occur at high levels of sulfate (150 mg/L)
using SBA at extremely low run times (400-650 BVs).
• When the sulfate concentration is moderate (60 mg/L), arsenic peaks are about 3x
influent for SBA and occurred at between 850-1400 BVs.
• At low sulfate concentrations (20 mg/L), arsenic peaks are about 1.3-1.4x influent for
SBA and occur between 1300-3400 BVs (i.e., a longer duration but less intense peak).
• No nitrate peaking was observed with WBA.
• Nitrate peaks with SBA occurred nearly concurrently with arsenic peaks, but these were
less intense (1.2x influent at 20 mg/L sulfate; 1.9x influent at 60 mg/L sulfate; 2x
influent at 150 mg/L sulfate).
High influent alkalinity can result in high O&M costs for WBA due to the pH adjustment
required.
ResinTech SBG1 SBA media released less chromium during the TCLP testing than did the
Purolite A600E/9149 SBA media. Very little chromium was released from the Purolite S 106 WBA
media during TCLP testing.
APPLICATIONS/RECOMMENDATIONS
SBA, WBA, and iron -based media have been studied in detail in this project and several
previous projects. This report synthesizes the cumulative results of this body of work into practical
guidance to help utilities anticipating or requiring treatment for Cr(VI) to comply efficiently.
Additional research may assist with the optimization of existing California best available
technologies (BATs), such as:
xxi

• Further developing the understanding of the secondary Cr(VI) removal mechanisms of
WBA will help to refine prediction of performance (and therefore cost) estimates.
• Determining the effect of SBA media on the aggressiveness of product water (through
TDS and alkalinity removal) will help in understanding the potential long-term impacts
on the distribution system.
• Conducting more in-depth study of the chromatographic peaking phenomenon as a
function of sulfate concentration so that utilities can be better informed of the risks.
• Determining if increased hardness results in media scaling and how that can affect
Cr(VI) removal.
Newly developed media should also be evaluated for Cr(VI) removal in a manner similar
to this study so that direct comparisons of efficacy can be made. Granular iron media (GIM) should
be reevaluated if changes are made to the media to control iron release.
Smaller utilities with water requirements of 2 MGD or fewer, and larger utilities with
spread -out wellfields that require wellhead treatment, can benefit from the Microsoft Excel
spreadsheet tool developed as part of this study. This tool incorporates most of the findings of this
study such that an informed choice can be made between SBA and WBA, which have been
identified as probable candidates.
Sulfate concentration and alkalinity are the major drivers when deciding between SBA and
WBA. Increased sulfate concentrations (greater than 50 mg/L) adversely affect SBA media
runtimes and can cause chromatographic peaking of nitrate and arsenic, while waters with high
alkalinity make WBA costly to operate. Operation of lead/lag vessels or parallel treatment may be
required with SBA to counter the peaking of nitrate or arsenic if their influent concentrations are
great enough. The long runtimes capable with WBA can also lead to accumulation of uranium in
residuals, making disposal costlier.
Other California BATS not included in this study should be considered before a final
decision is made. While cost opinions and treatment footprints described in this study can be used
for planning purposes, specific utility circumstances should be fully evaluated, taking into account
site -specific needs.
MULTIMEDIA
A Microsoft Excel spreadsheet was produced as part of this project and can be accessed on
the #4561 project page on the WRF website, posted under Web Tools. This spreadsheet accepts
inputs of key performance and water quality parameters from the user, including well capacity;
pH; alkalinity; hardness; and hexavalent chromium, sulfate, nitrate, and arsenic concentrations;
and provides guidance on selecting the most appropriate and cost-effective treatment technology
for Cr(VI) removal.
PARTICIPANTS
Utilities participating in this study covered a large geographical area and were selected
after being identified as having high levels of natural Cr(VI) in the most recent UCMR 3 database.
Each utility supplied water as necessary for the screening tests. Participating utilities will be
anonymous for this report and are designated as Utilities A—E. Media was supplied by North
American Hoganas, Purolite, ResinTech, and SMI.

CHAPTER I
INTRODUCTION
BACKGROUND AND PROJECT MOTIVATION
Chromium is an inorganic contaminant that has received a large amount of media attention
over the past 15 years primarily as a result of legal ramifications of an industrial contamination of
groundwater near Hinkley, California. In aqueous systems, chromium typically exists in two
different oxidation states: the trivalent form (Cr[III]), and the potentially carcinogenic hexavalent
form (Cr[VI]). The United States Environmental Protection Agency (EPA) currently has a
maximum contaminant level (MCL) for total chromium species (Cr[III] and Cr[VI]) of 100 µg/L
but does not regulate Cr(VI) itself.
In July 2011, California's Office of Environmental Health Hazard Assessment published a
final public health goal (PHG) of 0.020 micrograms per liter (µg/L) for Cr(VI) in drinking water.
The California Department of Public Health (CDPH; now DDW, The Department of Drinking
Water) subsequently published a draft maximum contaminant level (MCL) of 10 µg/L for Cr(VI)
on August 23, 2013. The MCL was finalized May 28, 2014, and became effective July 1, 2014.
The Cr(VI) regulatory horizon and potential compliance requirements are also of interest in other
states. The EPA is evaluating the health risk of ingesting Cr(VI) in order to determine the need
for regulating Cr(VI) and has indicated that it will determine if the existing total chromium (Cr)
MCL needs to be changed or if a Cr(VI)-specific MCL is needed once the occurrence and risk
assessments are complete.
Comprehensive occurrence monitoring performed on California drinking water sources
indicates Cr(VI) is widely found in source waters at levels above 1 µg/L and is a common naturally
occurring species of chromium found in groundwater (Brandhuber et al. 2004, Seidel et al. 2012).
Results from the third Unregulated Contaminant Monitoring Rule (UCMR 3) support this finding
and indicate low levels of Cr(VI) can be expected to be found in most drinking water sources,
although the highest levels appear to be confined to groundwaters of the southwestern states
(Seidel et al. 2012). While larger systems may be equipped to handle additional financial and
operational impacts associated with incorporating Cr(VI) treatment, smaller systems are likely to
have less flexibility in these areas. For these reasons, research on the applicability of Cr(VI)
treatment technologies implementable by small water utilities to a wide range of water quality
characteristics found in drinking water sources was needed. This research was intended to provide
these utilities with a starting point for decision -making stemming from Cr(VI) compliance.
TREATMENT TECHNIQUES FOR CR(VI)
There are numerous methods for removing Cr(VI) from water. A comprehensive review
of Cr(VI) removal was conducted in 2008 (Sharma et al. 2008), and some comprehensive
evaluations of viable treatment processes and cost evaluations have also been completed for Cr(VI)
removal at California utilites (Drago 2001; Lee and Hering 2003; Qin et al. 2005; McGuire et al.
2006; McGuire et al. 2007; Blute et al. 2010; Blute 2010; McGuire 2010; Blute and Wu 2012).
Some of the treatment techniques evaluated were reductive coagulation, weak base anion (WBA)
exchange and strong base anion (SBA) exchange. These studies have shown that reductive
coagulation can easily obtain very low levels (< 5 µg/L) of Cr(VI) in water leaving the treatment
plant. Membranes, WBA exchange and SBA exchange are also effective at relatively higher cost
1

due to residual handling and water losses (Drago 2001; McGuire et al. 2006). WBA treatment
consists of polymeric resin that must be utilized at about pH 6 for effective Cr(VI) removal so pH
readjustment is almost always necessary. SBA resin is also able to remove Cr(VI) from water but
requires significant amounts of salt for regeneration and requires brine disposal. Reductive
coagulation with filtration (RCF) is more labor intensive than either WBA or SBA exchange due
to mulitiple treatment steps and aeration or pH adjustment may be required depending on influent
water chemistry. In addition, wastes from these processes can be classified as hazardous such that
special procedures may be necessary for disposal (Blute and Wu 2012). There is limited work
showing that Cr(III) can be removed during conventional alum or ferric coagulation via co -
precipitation with Al(OH)3 or Fe(OH)3, but this is not effective for removing Cr(VI) unless it is
first reduced to Cr(III) (Sharma et al. 2008). Ultimately, the effectiveness of any method and the
relative cost/benefits will be dependent on the source water chemistry, pre-existing treatment
processes and facilities, and residual handling concerns (McNeill et al. 2013).
OVERVIEW OF PREVIOUS RESEARCH
Sorptive media have been used in several recent studies and have shown promise. One
such study was conducted by Brandhuber et al. (2004). In addition to several other technologies,
these researchers evaluated nine ion exchange resin or other media. The media tested included
granular ferric hydroxide (GFH), granular ferric oxide (GFO), sulfur -modified iron (SMI),
activated alumina (AA), iron -impregnated activated alumina, iron -impregnated zeolite, iron -oxide
coated diatomite, bauxite clay, and a metal -binding ligand. All but the activated alumina removed
Cr(VI) by at least 70% at a media dose of 4 g/L. Cr(VI) removal decreased dramatically for many
of these when a carbonate buffer was added to the test water and pH was maintained. Only the
SMI and `Media I' removed more than 90% of the Cr(VI) at these conditions [Note that Media I
did not appear in authors' descriptive table and it was not made clear what it actually was].
Brandhuber et al. (2004) also looked at the effect of competing solutes on Cr(VI) removal.
Removal using the SMI media was not affected by chloride, sulfate, bicarbonate, total organic
carbon (TOC), or nitrate. For most of the other media, Cr(VI) removal was negatively impacted
by the presence of sulfate, bicarbonate, and total organic carbon (TOC).
Brandhuber et al. (2004) also conducted some small-scale column tests using four
commercially available ion exchange resins. These included Dow Marathon MSA and Purolite
A-600 (two SBA Type I resins) and Amberlite IRA410 and Purolite A-300 (two SBA Type II
resins). They also tested the SMI media in two column tests. The four SBA resins had very similar
performance and appeared to preferentially remove Cr(VI) over sulfate. The column tests with the
SMI media were inconclusive. SMI had the highest capacity for Cr(VI) removal but there was
concern that high levels of iron could be released during its operation. Additionally, the column
and batch tests had conflicting results for Cr(VI) capacity and no reason could be ascertained.
The first major sources of information available on the removal of Cr(VI) from drinking
water to levels of less than 10 µg/L (the California MCL) included two programs: the research
conducted at the City of Glendale, California, and the full-scale SBA exchange systems operated
by Coachella Valley Water District (CVWD).
The Glendale research is described in detail on the City's website. Briefly, bench scale
testing of 25 technologies screened available approaches. Seven technologies identified as capable
of consistently removing Cr(VI) to less than 5 µg/L (the Glendale treatment goal) were then tested
at the pilot -scale under flow -through conditions. Three of the initial 25 technologies were shown
to be effective in pilot testing, including WBA, SBA, and RCF. Reverse osmosis (RO) was also
2

effective at bench scale, but was not tested further due to water losses deemed unacceptable by
Glendale.
Glendale pilot testing was followed by construction of two demonstration -scale facilities:
a 425-gallons per minute (gpm) WBA system, and a 100-gpm RCF treatment system. These
facilities were effective in achieving Cr(VI) performance goals and served water to customers
during the tests. Significant information was gained on design criteria for the approaches,
operational aspects of the technologies, pre- and post -treatment requirements, residuals handling
and disposal options, and costs of technologies.
CVWD's three full-scale ion exchange treatment plants (IXTPs; 1,000 to 4,000 gpm) use
SBA resin to effectively remove arsenic and Cr(VI). These findings are in agreement with the
bench and pilot testing conducted at other utilities.
More recently, multiple studies have investigated Cr(VI) treatment performance of the
leading three technologies at different utilities. WRF projects #4450 (Najm et al. 2014) and #4445
(Chowdhury et al. 2016) in particular studied the impact of ten different utilities' water qualities
on WBA, SBA, and RCF at the bench -scale. Additional testing at Glendale and CVWD evaluated
using microfiltration in the RCF process (i.e., reduction -coagulation -membrane filtration, or
RCMF) and chlorine for ferrous oxidation (Blute et al. 2015a, Chowdhury et al. 2016). Other
options for single -pass media (SBA, WBA, and adsorptive media) were tested in studies with
California Water Service Company's Livermore District and Glendale (Blute et al. 2015b) and
CVWD (Chowdhury et al. 2016). Pacific Gas and Electric (PG&E) provided Cr(VI) treatment to
below 0.06 µg/L for Hinkley, CA via single -pass SBA POE (point -of -entry) units; this work helped
to not only build on previous research, but develop practical insight into operations within the
context of smaller communities.
Key findings from these studies and the PG&E program that are applicable to the findings
in this study (WRF #4561) are:
• WBA showed no major differences in removal performance for different water
qualities with respect to Cr(VI), although pre-treatment costs varied. Varying influent
concentrations can have a significant impact on disposal (and therefore overall) costs.
• SBA showed that Cr(VI) capacity primarily varied with sulfate concentrations. Higher
Cr(VI) capacities may be possible with lower sulfate concentrations. Additional
contaminants (such as nitrate or arsenic) must be considered, as these concentrations
can be increased for a time period due to the non -selective nature of SBA resins
(chromatographic peaking).
• RCF is a promising technology that may be too operationally complex for smaller
systems.
• Iron -based absorptive media tested at the pilot scale was effective at removing Cr (VI)
but leached iron into the effluent. Mitigation for the iron needs to be developed before
this technology is tested at demonstration scale and the additional treatment may not be
cost effective.
RESEARCH APPROACH FOR THIS STUDY
The research in this study was executed in three tasks as follows. In Task 1 (Chapter 2)
bench -scale evaluations were conducted for six different ion exchange media and seven different
water chemistries (obtained from various utilities). The results obtained from Task 1 were used to
3

select the ion exchange media that were used in Task 2. In Task 2 (Chapter 3) seven small-scale
column tests were conducted to test the selected media for capacity and breakthrough. In Task 3
(Chapter 4), practical application of the results from the first two tasks were explored and are
communicated to utilities and consultants with a water quality based decision tree, process flow
diagrams, conceptual site layouts, operational training requirements, residuals handling strategies,
and cost opinions. Each of these tasks is described in more detail in the following sections.
Task 1 — Bench -Scale Screening Tests
Much work has been conducted in the past 10-15 years with respect to the removal of
hexavalent chromium from the drinking water supplies of large utilities via ion exchange resins or
other adsorptive media. In this study, we evaluated a number of these media for their applicability
to small systems. Five utilities supplied a total of seven groundwaters for the bench -scale tests.
These utilities cover a large geographical area and are not just from southern California and all
were identified as having high levels of natural Cr(VI) in the most recent UCMR 3 database.
Hexavalent chromium exists in natural waters as an oxyanion, either HCr04" or Cr04
depending on pH. As such, it is removed by ion exchange media by adsorption to positively
charged surface sites. In many instances it is `exchanged' for chloride which is held at these sites.
In some cases, special media have been designed to be selective for chromate, but in most cases
other anionic species will compete with chromate for these surface sites. Sulfate, in particular, is
of interest because of past experience with using ion exchange for arsenate removal. Arsenic is
very similar to chromate and past studies have shown that ion exchange is not very effective for
arsenic removal in waters with high concentrations of sulfate. Also, ion exchange resins can
exhibit "chromatographic peaking" for co-occurring contaminants such as nitrate. In this study
we evaluated each media in water with high levels of typical anionic species that are found in
source water, including sulfate, nitrate, (bi)carbonate, silicate, chloride, and natural organic matter
(NOM). Six ion exchange resins and media were evaluated during this work, including two SBA,
two WBA, and two iron -based media (described in more detail in Chapter 2).
Adsorption isotherms were developed from the Cr(VI) concentration results for each media
for each water tested. Each isotherm is a plot of the adsorbed Cr(VI) per unit mass of adsorbent
versus the equilibrium Cr(VI) concentration in solution. The most widely used mathematical
model used to describe adsorption is the Freundlich isotherm (Faust and Aly 1987). This isotherm
is expressed by Equation 1.1:
x/m = KCl/n (1.1)
where x is the amount of solute sorbed, in is the mass of adsorbent, C is the equilibrium
solution concentration of solute, and K and n are constants characteristic of the system. This
expression can be linearized by taking logarithms as shown in Equation 1.2:
log(x/m) = log(K) + l/n * log(C) (1.2)
Plotting log(x/m) versus log(C) will result in a straight line with slope equal (1/n) and y-
intercept equal log(K) if the Freundlich isotherm is applicable.
4

Test of Sensitivity to pH and Competing Solutes
As discussed previously, anionic solutes could compete with chromate for adsorption sites
on certain ion exchange media. A study was conducted as part of Task 1 to evaluate each media
for their ability to adsorb Cr(VI) when these competing solutes were present.
For this experiment we used synthetic Blacksburg (VA) water formulated from distilled
water and various salts as the baseline water. However, the pH and anionic species concentrations
were manipulated so that a low, medium, and high concentration of each species could be
evaluated (Table 1.1). These concentrations were selected based on the 10, 50, and 90 percentile
concentrations in United States waters (Snoeyink and Jenkins 1980). Sodium chromate was added
to each test water so that an initial concentration of approximately 100 µg/L Cr(VI) was present.
In-depth analysis of competing solutes has not been conducted in the past. This was a key
focus of this study as these findings are critical to small utilities when making decisions about
which treatment technology to employ.
Table 1.1
Experimental concentrations of competing solutes
Constituent
Concentration
Unit
Low Medium High
Sulfate
5
25
100
mg/L
Nitrate
0
1
10
mg/L
Silicate
5
10
40
mg/LasSi02
TOC
0
2
5
mg/L as C
Chloride
5
10
100
mg/L
Alkalinity (bicarbonate)
30
100
300
mg/L as CaCO3
Task 2 — Small -Scale Column Tests
After completion of Task I the research team, in conjunction with the PAC, determined
which of the three media tested performed the best and would make good candidates for the small-
scale column tests. The column tests were critical in that they provided information on the
breakthrough of hexavalent chromium at the targeted empty bed contact time (EBCT). This
allowed one to predict the life of the resin/media which, in turn, allowed one to predict the yearly
cost of operation. The column tests also created media/resin which was exhausted, which was then
tested for leaching characteristics. Seven small column tests were conducted.
Upon completion of the column testing, the spent media were evaluated using the Toxicity
Characteristic Leaching Procedure (TCLP) and the California Waste Extraction Test (CA WET).
These tests are used to determine if a waste is to be characterized as `hazardous' in terms of
disposal. These tests were designed to simulate leaching in a landfill environment although,
typically, the CA WET is the more aggressive of the two.
Task 3 — Practical Application of Results
Task 3 involved developing practical guidance that impacted small systems could use to
plan and implement hexavalent chromium treatment processes. This guidance includes a water
quality based decision tree and process flow diagrams, concept -level site layouts, residual
5

management strategies, and capital and operation treatment cost opinions for candidate treatment
technologies. Our team identified the following list of candidate treatment technologies for
hexavalent chromium removal:
• Strong base anionic (SBA) resin exchange with replacement of exhausted resin (and no
onsite regeneration)
• SBA resin exchange with onsite regeneration of resin using salt/brine
• Weak base anionic (WBA) resin exchange with replacement of exhausted resin (and
possible pH adjustment for some waters)
• Granular iron media such as sulfur modified iron (SMI) or Cleanit®-LC (with possible
iron removal process to control potential leaching of iron)
• Reduction coagulation filtration (RCF) using granular media filters
• RCF using microfiltration/ultrafiltration (MF/UF) membranes for filtration
• Reverse osmosis
Among the above processes, the RCF and RO treatment processes are complex to operate
and require a higher level of operator attention from skilled operators so small water systems may
not be able to implement the RCF and RO treatment processes at their impacted well sites.
A simple, "interactive" spreadsheet based tool has been developed as a decision tree that
will deliver tailored and specific guidance to the impacted small systems based on the inputs that
the user enters into the input form. The input form will seek inputs related to the impacted well
flows (well capacity, average flow/usage), water quality (hexavalent chromium, pH, alkalinity,
hardness, sulfate, nitrate, arsenic, uranium etc.), site constrains (land available, accessibility, sewer
connectivity etc.) and operator preferences (simple versus complex processes, onsite storage of
chemicals, etc.).
Based on the inputs entered, the spreadsheet tool will screen the candidate treatment
processes and identify the feasible processes for further consideration. For the feasible processes,
the tool will calculate the resin or media replacement/regeneration frequency, treatment footprint
requirements, capital costs, operation and maintenance (O&M) costs, estimates of residuals that
would be generated, quality of residuals, and warnings related to water quality interferences and
residuals disposal.
In addition to the interactive tool, we have developed hardcopy guidance that includes
process flow diagrams for the candidate treatment alternatives, conceptual site layouts, capital and
O&M cost tables for 0.5-2.0 million gallons per day (mgd) flows and discussion of residuals
management strategies. This hardcopy guidance will supplement the spreadsheet tool outputs.
6

CHAPTER 2
SCREENING OF ION EXCHANGE RESINS AND MEDIA
Much work has been conducted in the past 10-15 years with respect to the removal of
hexavalent chromium from the drinking water supplies of large utilities via ion exchange resins or
other adsorptive media. In this study we evaluated a number of these media (described below) for
their applicability to small systems. Water from a number of utilities identified as having high
levels of natural Cr(VI) was used to further develop adsorption isotherms for each media.
Synthetically prepared water was used to evaluate each media in the presence of competing solutes.
These studies are detailed in this chapter.
ION EXCHANGE RESINS AND MEDIA INCLUDED IN THIS STUDY
There are four Best Available Technologies (BATs) recognized by California for Cr(VI)
removal: Weak Base Anion Exchange (WBA-IX), Strong Base Anion Exchange (SBA -IX),
Reduction/Coagulation/Filtration (RCF), and Reverse Osmosis (RO). As noted previously, RCF
is an operationally complex technology that is unlikely to be the first choice for small utilities.
Reverse osmosis (RO) requires intensive capital and O&M investment and results in significant
quantities of wasted water. As a result, these two technologies were not further evaluated in this
study.
Four ion exchange resins (California BATs for Cr(VI)) and two iron based media (while
not California BATs, these media have shown some promise) were evaluated with water
containing between 10 and 100 µg/L Cr(VI) in this study. These resins/media have all been
evaluated previously in various contexts; this research hopes to examine them in both additional
and unifying conditions.
WBA resins tend to have very long life for Cr(VI) before exhaustion, but perform best at
lower pH values (under 6-6.5), and thus require pre- and post -treatment. SBA resins tend to have
lower capacities for Cr(VI) removal before exhaustion than WBA resins due to their nonselective
nature. These resins will remove and be affected by other anions, especially sulfate and nitrate.
Iron -based media, while not a BAT for Cr(VI) and possessing concerns (such as the propensity to
leach significant amounts of iron into the product water), has been shown to be effective for Cr(VI)
removal. The specific media types are displayed in Table 2.1.
Table 2.1
Media tested
Media Type
Media Name
Supplier
SBA
SBGI
ResinTech (West Berlin, NJ)
SBA
A600E/9149
Purolite (Bala Cynwyd, PA)
Fe
C1eanIt-LC
North American Hoganas (Hollsopple, PA)
WBA
SIR-700
ResinTech (West Berlin, NJ)
WBA
S 106
Purolite (Bala Cynwyd, PA)
Fe/S
SMI
SMI-PS Concord, CA
7

PARTICIPATING UTILITIES
Utilities participating in this study covered a large geographical area and were selected
after being identified as having high levels of natural Cr(VI) in the most recent UCMR 3 database.
Each utility supplied water as necessary for the screening tests. Participating utilities will be
anonymous for this report and be designated Utilities A — E.
ANALYTICAL METHODS
The following list of analytical instruments and techniques were used throughout the study
as appropriate:
Metals Concentrations
All samples for total metals concentration were preserved by acidification with trace metal
grade nitric acid to 2% v/v. Samples were analyzed for total chromium, sodium, calcium,
magnesium, potassium, silicon, iron, arsenic, and uranium by inductively coupled plasma mass
spectrometry (ICP-MS) using a Thermo Electron X-Series ICP-MS following Standard Method
3125-B (APHA et al. 1998).
Hexavalent Chromium Concentration
All samples for Cr(VI) concentration were preserved with an ammonium
hydroxide/ammonium sulfate solution prepared per specifications in EPA Method 218.7 (EPA
2011). Cr(VI) concentration was measured with a Dionex ICS 1000 ion chromatograph with post -
column reaction cell (IC-PCR) followed by a variable wavelength detector as specified in EPA
Method 218.7.
Anionic Species Concentrations
All samples for anionic species —such as chloride, sulfate, and nitrate —were stored at 4
°C prior to analysis. These samples were analyzed using a Dionex DX 120 ion chromatograph
(IC) using Standard Method 4110 (APHA et al. 1998).
Total Organic Carbon Concentration
All samples were acidified to a pH of <4 prior to
hydrochloric acid and purged to remove all inorganic carbon.
using a Shimadzu TOC-V, total organic carbon combustion
5310B (APHA et al. 1998).
Alkalinity
TOC analysis using concentrated
TOC concentration was determined
analyzer as per Standard Method
Alkalinity was measured using a burette with standardized sulfuric acid per Standard
Method 2320 (APHA et al. 1998).
8

DEVELOPMENT OF ADSORPTION ISOTHERMS
Adsorption isotherms (see discussion in Chapter 1) for each media discussed above were
constructed using the following protocol. Five 500-mL HDPE bottles were filled with each utility
water containing Cr(VI) and, in most cases, potassium chromate was added to the water so that
there was an approximate initial concentration of 100 µg/L hexavalent chromium. A different
amount of ion exchange media was added to each bottle, including 0, 0.25, 1, 2, and 4 g/L. This
was repeated for each of the media. All bottles were placed on an orbital shaker for 24 hours. At
30 minutes, 2 hours, 4 hours, and 24 hours each bottle was removed from the shaker so that a 20
mL water sample could be collected. Additionally, the pH was measured and adjusted back to the
original value if necessary using I N sodium hydroxide. The sample was passed through a 0.45-
micron nylon syringe filter. A 5 mL aliquot was acidified with 2% v/v trace metal grade nitric
acid and analyzed for metals concentrations. Another 5 mL aliquot was preserved with an
ammonium hydroxide / ammonium sulfate solution prepared per specifications in EPA Method
218.7 and used to measure Cr(VI) concentration. Another 5 mL aliquot was collected for analysis
of anionic species. Finally, a 30 mL aliquot was analyzed for dissolved organic carbon (DOC)
(Note that DOC was only measured at the end of each test due to the larger volume of sample
required for the analysis).
Water Quality Characteristics
Seven waters from the five participating utilities were tested, as Utility A and Utility C
each supplied water from two different wells. All waters tested were groundwater, however raw
water chemistry varied widely as illustrated in Table 2.2. All waters had Cr(VI) concentrations
ranging from 17 to 87 µg/L and these were increased to approximately 100 µg/L using a potassium
chromate solution in most tests. Note that the total chromium and Cr(VI) concentrations are nearly
identical, indicating that approximately 100% of the dissolved chromium is in the +6 form (also
note that in two cases the Cr(VI) actually read slightly higher than the total chromium, but this can
be explained by the precision in the two analytical methods being used). Alkalinities of the utility
waters ranged from 90 to 308 mg/L as CaCO3. Nitrate in both the Utility A wells exceeded the
MCL (I I — 16 mg/L as N) and arsenic in one of the Utility C wells exceeded the MCL (16 µg/L
as N). Each of the utility waters (except Utility E) also contained small concentrations of uranium
(2 — 12 µg/L).
9

Table 2.2
Raw water quality parameters
Parameter
Unit
Utility A
Well A
Utility A
Well B
Utility C
Utility B Well A
Utility C
Well B
Utility D
Utility E
Total Cr (raw)
µg/L
18.9
20.8 17.5 20.3
67.7
84.7
24.7
Cr(VI) (raw)
µg/L
17.9
20.1 n/m 17.0
71.8
86.7
24.5
Cr(VI) test
/L
_
103
101 90.3 140
71.8
86.7
105
pH
-
7.8
7.7 8.2 8.0
8.8
8.1
7.6
Alkalinity
mg/L as CaCO3
148
184 90 87
94
230
308
Sodium
mg/L
37.3
13.2
42.1 223
55.2
113
48.9
Magnesium
mg/L
_
7.4
17.9
2.8 6.3
2.0
5.9
67.3
Silicon
mg/L as Si
_
10.1
11.7
6.1 11.5
7.8
5.0
26.3
2.1
Potassium
mg/L
1.7
4.2 4.8
1.3
1.6
1.2
Calcium
mg/L as Ca
74.9
98.0
14.3 37.0
4.8
8.2
35.2
1 ron
µ g/L
8.5
16.3
3.4 34.1
23.6
34.9
9.1
Manganese
µg/L
0.0
0.0
0.1 2.2
0.0
0.0
0.1
Arsenic
µg/L
3.9
0.1
1.4 21.5
6.0
4.9
0.6
Strontium
µg/L
623
484
253 968
145
423
162
Barium
µg/L
82.5
55.2
_
25.3 40.1
3.6
175
48.5
Uranium
g/L
2.5
3.9
4.4 12.1
2.7
11.4
0.5
TOC
mg C/L
0.2
0.2
0.1 0.3
0.1
0.3
0.3
Fluoride
mg/L
0.1
0.2
0.8 2.2
1.1
0.4
0.6
Chloride
mg/L
30.5
35.4
8.5 215
16.6
18.4
53.9
Sulfate
mg/L
88.8
87.4
50.0 130
16.8
13.4
49.6
Nitrate
mg/L
10.8
15.9
0.3 2.4
1.6
0.3
4.9
n/m = not measured
Cr(VI) Removal Results for Iron -Based Media
The two iron -based media were extremely effective at removing Cr(VI) from all waters
tested; so much so, that the dosage for the SMI media was decreased to 0, 0.1, 0.2, 0.2, and 0.8
g/L in an attempt to have measurable concentrations of Cr(VI) in the water after 30 minutes of
contact. Results for the Cr(VI) removal are shown in Table 2.3 with the red shading indicating
that the Cr(VI) concentration of that test condition was greater than the California MCL of 10
µg/L. As a result of the high Cr(VI) removal at all media doses tested, adsorption isotherms could
not be developed for these media. It is perplexing to note, however, the behavior of the Clean -It
LC media in the Utility D water. At a dose of 0.25 g/L this media was not able to remove enough
Cr(VI) to meet the California MCL of 10 µg/L although Cr(VI) was below detection in all the
other waters tested. The only noticeable difference in water quality was that the barium
concentration was at least twice as high as any of the other waters but we have no theory on why
that might have affected Cr(VI) removal.
10

Table 2.3
Cr(VI) removal using iron -based media
Dose
Contact
Utility A
Utility A
Utility C
Utility C
Media
Utility B
Utility D
Utility E
(g/L)
Time (hr)
Well A
Well B
Well A
Well B
0.5
71.2
50.6
78.7
87.0
61.2
75.3
44.9
2
4.2
2.8
54.0
13.1
36.7
54.8
< 0.1
0.25
4
<0.1
<0.1
10.4
1.4
13.4
40.9
<0.1
24
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
16.2
< 0.1
U
0.5
9.5
3.1
45.2
3.6
44.8
53.5
2.3
2
< 0.1
< 0.1
10.9
< 0.1
4.8
29.3
< 0.1
-1
91
1.0
4
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
16.0
< 0.1
+=
24
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
0.5
< 0.1
0.5
12.5
0.3
15.7
<0.1
29.6
23.8
<0.1
2
< 0.1
0.0
< 0.1
< 0.1
< 0.1
5.6
< 0.1
2.0
4
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
1.2
< 0.1
U
24
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
0.2
< 0.1
0.5
< 0.1
< 0.1
1.1
< 0.1
12.4
20.7
< 0.1
2
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
3.1
< 0.1
4.0
4
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
24
< 0.1
< 0.1
< 0.1
< 0.1
0.1
< 0.1
< 0.1
0.5
6.8
< 0.1
< 0.1
0.4
7.4
0.3
< 0.1
2
< 0.1
< 0.1
0.3
< 0.1
0.1
< 0.1
< 0.1
0.1
4
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
0.0
< 0.1
24
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
0.0
< 0.1
0.5
3.0
< 0.1
< 0.1
5.5
1.8
< 0.1
< 0.1
2
< 0.1
< 0.1
0.3
< 0.1
< 0.1
< 0.1
< 0.1
0.2
_
4
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
73
24
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
C/)
0.5
< 0.1
< 0.1
< 0.1
0.1
0.1
0.2
< 0.1
2
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
0.4
4
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
24
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
0.5
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
2
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
0.8
4
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
24
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
Note: Cr(VI) concentrations are in µg/L; values less than MRL reported as `< 0. V). Red shaded
data are greater than the California MCL of 10 µg/L, while green shaded data are lower. Initial
Cr(VI) concentration of 100 µg/L was spiked using a potassium chromate solution.
While these iron -based media were highly efficient at Cr(VI) removal, this removal came
at a cost. Large amounts of iron particles were visible after prolonged contact with each media
(Figures 2.1 and 2.2). Dissolved iron was extremely high as well in the waters in contact with the
SMI media (I mg/L to as high as 56 mg/L), but much lower in waters in contact with the Cleanit®-
LC media (less than the SMCL of 0.3 mg/L in most cases; data not shown), indicating that only
filtration might be required for the Cleanit®-LC media. In any event, these two media would
undoubtedly require some sort of iron removal unit operation downstream, increasing cost and
complexity.
11

Figure 2.1 Visible iron particles after 24 hours of contact with Cleanit®-LC media
Figure 2.2 Visible iron particles after 24 hours of contact with SMI media
Cr(VI) Removal Results for Strong Base Anionic (SBA) Resins
The two SBA resins were tested at the ambient pH of the utility water; i.e., no pH
adjustment was made at the beginning of the test. The pH tended to decrease slightly during the
test so it was adjusted back to its initial value using a few drops of 1 N NaOH at 30 minutes, 2
hours, and 4 hours. Each media was able to reduce Cr(VI) below 10 µg/L in all utility waters at
the highest media dose and contact time tested (Table 2.4). Also, in most instances, Cr(VI)
removal was similar for both media.
12

Table 2.4
Cr(VI) removal using SBA media
Dose
Contact
Utility A
Utility A
Utility C
Utility C
Media
Utility B
Utility D
Utility E
(g/L)
Time (hr)
Well A
Well B
Well A
Well B
0.5
99.7
70.2
72.9
135.7
66.9
79.9
93.7
2
72.7
72.8
65.6
113.2
50.1
73.8
61.2
0.25
4
56.4
66.0
47.4
129.8
40.9
71.1
52.4
24
30.1
35.7
20.5
69.9
8.8
47.5
20.9
0.5
60.6
74.8
63.0
101.2
62.0
65.8
69.3
(n
1.0
2
44.6
27.8
44.3
71.9
27.4
40.4
15.0
4
28.9
14.4
31.6
51.7
14.7
30.3
4.8
24
2.9
5.8
1.5
22.7
0.7
2.7
3.3
U
N
0.5
63.8
63.3
45.6
78.5
45.9
55.7
48.2
2
9.6
7.4
14.2
49.8
23.2
34.9
3.3
2.0
4
4.2
2.4
7.0
34.6
13.6
25.4
1.4
�
24
1.0
1.4
0.5
9.3
0.2
5.9
1.2
N
0.5
79.7
42.0
40.6
63.7
36.2
43.9
33.4
2
54.1
1.1
6.4
20.3
3.7
19.6
1.9
4.0
4
30.1
0.6
2.4
11.2
0.9
13.0
0.8
24
0.5
0.5
< 0.1
2.9
< 0.1
3.2
0.4
0.5
101.1
90.5
76.0
127.2
62.2
73.8
94.1
2
77.1
79.8
80.6
91.2
40A
48.8
57.3
0.25
4
62.5
59.4
68.1
94.3
22.0
38.7
48.5
24
31.0
33.8
29.8
70.2
0.3
13.7
21.1
O7
0.5
80.8
71.3
48.4
84.7
37.3
64.7
60.5
O
2
41.6
19.2
30.4
27.9
6.6
28.9
11.1
10
CD4
22.3
7.9
18.6
22.2
0.8
20.3
3.8
(0
24
12.2
6.1
0.9
22.0
0.3
2.5
2.9
Q
0.5
51.8
42.2
56.2
60.2
19.9
50.2
33.1
2
12.2
3.3
27.4
10.7
0.7
24.1
1.7
:tf2.0
4
3.6
1.7
14.3
9.7
< 0.1
17.6
1.1
O
24
0.8
1.5
0.4
9.6
0.1
3.8
1.1
0.5
34.2
27.7
41.7
41.9
13.3
39.8
20.5
2
2.3
0.7
15.3
3.9
0.3
17.4
0.6
4.0
4
0.6
0.6
4.9
4.0
< 0.1
11.6
0.5
24
0.4
0.6
< 0.1
3.3
< 0.1
2.7
0.5
Note: Cr(VI) concentrations are in µg/L; values less than MRL reported as `< 0. V). Red shaded
data are greater than the California MCL of 10 µg/L, while green shaded data are lower. Initial
Cr(VI) concentration of 100 µg/L was spiked using a potassium chromate solution.
Cr(VI) Removal Results for Weak Base Anionic (WBA) Resins
The two WBA resins were tested at pH 6 to 6.5 per supplier's recommendations. The pH
of the supplied water was decreased to 6.0 by bubbling with CO2(g) so that alkalinity and other
dissolved salts were not altered. The pH tended to increase slightly during the test but seldom
exceeded pH 6.5 by the end of the tests. Each media was able to reduce Cr(VI) below 10 µg/L in
all utility waters at the 2 g/L media dose and maximum contact time tested (Table 2.5). Also, in
most instances, Cr(VI) removal was similar for both media.
13

Table 2.5
Cr(VI) removal using WBA media
Dose
Contact
Utility A
Utility A
Utility C
Utility C
Media
Utility B
Utility D
Utility E
(g/L)
Time (hr)
Well A
Well B
Well A
Well B
0.5
102.1
92.5
84.7
126.1
61.8
81.1
95.5
O
0.25
2
80.2
87.5
73.7
102.2
46.4
73.7
65.7
O
4
66.9
75.1
59.0
103.5
29.9
68.3
70.8
24
32.1
34.2
23.4
60.1
6.7
37.4
26.0
0.5
71.8
68.3
71.1
87.6
43.3
66.8
66.8
2
32.6
31.4
34.7
51.6
14.0
50.5
23.5
�
1.0
4
17.7
16.7
17.1
33.6
3.5
37.5
12.3
24
5.2
5.0
2.2
13.2
0.7
8.6
5.1
U
0.5
n/m
54.1
70.0
61.4
29.1
52.5
43.2
2
23.2
15.0
18.3
18.9
4.0
32.7
8.0
2.0
4
13.2
5.5
5.8
11.7
0.8
21.2
4.2
24
1.4
1.7
0.4
3.4
0.2
1.7
2.0
0.5
45.3
45.2
47.4
37.3
13.8
41.4
29.6
2
14.7
4.2
15.0
5.5
0.6
26.7
2.9
4.0
4
6.6
1.5
4.7
3.3
0.2
16.8
1.4
24
0.4
0.5
< 0.1
1.3
< 0.1
0.6
0.6
0.5
n/m
97.0
83.5
129.5
63.7
78.0
94.8
2
82.8
85.1
81.0
133.9
54.2
64.8
68.3
0.25
4
68.1
68.2
65.1
123.0
40.8
49.7
58.2
24
33.0
39.1
28.7
68.6
14.4
19.9
30.3
C0
O
0.5
75.4
74.5
70.0
88.1
49.1
73.8
70.2
Ir-
1.0
2
30.6
47.9
39.1
57.4
21.1
45.2
25.0
(n
4
16.9
25.3
20.7
44.6
6.7
26.9
14.2
N
24
7.7
10.6
5.3
17.6
1.6
5.2
8.9
}'
0.5
67.1
60.6
57.5
73.5
35.1
53.5
63.4
0
2
31.7
23.0
26.4
39.8
6.6
26.1
19.3
2.0
4
19.4
10.2
9.7
27.1
1.3
13.8
8.6
:3
24
3.3
3.8
1.2
6.2
0.6
1.7
3.2
0.5
41.3
39.7
51.1
48.2
22.2
69.0
39.6
2
8.3
7.7
19.3
20.6
1.5
11.4
5.0
4.0
4
3.3
2.3
5.6
12.8
0.3
5.4
2.6
24
1.2
1.5
0.4
2.3
0.2
0.8
1.5
Note: Cr(VI) concentrations are in µg/L; values less than MRL reported as `< 0. V). Red shaded
data are greater than the California MCL of 10 µg/L, while green shaded data are lower. Initial
Cr(VI) concentration of 100 µg/L was spiked using a potassium chromate solution.
n/m = not measured
Effect of Media on Other Water Quality Parameters
In addition to the removal of hexavalent chromium, each of the media tested in this study
will also affect other water quality parameters. The effects on sulfate, chloride, and nitrate are
shown in Table 2.6. The data show that the SBA and WBA media remove most of the sulfate
present in the raw water, and release chloride into the water. The two iron -based media appear to
have little effect on sulfate and chloride. Nitrate is a regulated contaminant with an MCL of 10
14

mg/L as N, so it would be beneficial for the media to remove it as well as the Cr(VI). In this study,
SMI media did not remove nitrate, while the other iron -based Cleanit®-LC media removed up to
30% of the raw water nitrate. The two SBA media were much more efficient at removing nitrate
than the two WBA media (75-79% versus 34-56%, respectively).
Table 2.6
Sulfate, chloride, and nitrate concentrations after 24 hours of contact time
Dose
Contact
Utility A
Utility A
Utility C
tili
Uty C
Media
Utility B
Utility D
Utility E
/L
Time hr
Well A
Well B
Well A
Well B
Sulfate (mgk)
Raw water
-
-
88.8
87.4
50.0
130
16.8
13.4
49.6
SBG-1
4
24
1.6
1.3
0.0
16.2
0.0
0.6
1.6
A600/9149
4
24
1.7
1.8
0.0
18.8
0.0
0.0
1.9
Cleanit'l-LC
4
24
86.5
80.0
46.6
126
14.6
13.9
49.3
SIR-700
4
24
1.4
2.4
0.0
8.2
0.0
0.0
1.7
S106
4
24
3.6
4.0
0.0
9.3
0.4
0.0
3.9
SMI
0.8
24
98.0
95.0
52.5
135
16.0
17.7
56.9
Chloride (mg1L)
Raw water
-
-
30.5
35.4
8.5
215
16.6
18.4
53.9
SBG-1
4
24
165
179
89.8
265
80.7
100
147
A600/9149
4
24
161
174
88.7
263
82.1
101
144
Cleanit° LC
4
24
33.8
39.7
11.8
216
20.2
25.3
56.7
SIR-700
4
24
173
181
103
258
40.2
120
116
S106
4
24
94.9
98.2
61.3
217
60.4
71.1
101
SMI
0.8
24
30.0
35.2
8.2
213
14.2
17.4
54.0
Nitrate (mgk)
Raw water
-
-
10.8
15.9
0.3
2.4
1.6
0.3
4.9
SBG-1
4
24
1.4
2.5
0.0
1.3
0.2
0.3
1.4
A600/9149
4
24
1.4
2.4
0.0
1.2
0.0
0.0
1.3
Cleanit°-LC
4
24
7.8
12.7
0.2
2.2
1.5
0.3
4.4
SIR-700
4
24
5.1
7.8
0.0
1.9
0.0
0.2
2.2
S106
4
24
7.0
10.0
0.0
2.0
0.8
0.1
3.4
SMI
0.8
24
10.6
15.6
0.2
2.4
1.2
0.3
4.8
It would also be beneficial to remove uranium and arsenic in some instances (e.g., in
situations where removal could be achieved without raising additional concerns for media
disposal). In this study all media tested removed both uranium and arsenic (Table 2.7). Other
elements that were affected were silicon, iron, and manganese. Both SMI and Cleanit®-LC
removed silicon (average of 69% and 24%, respectively; Table 2.7) and this has the possibility of
competing with Cr(VI) removal (see `Effect of Competing Solutes on Hexavalent Chromium
Removal' section below for more on this). The SBA and WBA media had no effect on silicon.
As mentioned previously, both iron -based media released iron and manganese to the water (Table
2.6) and this would have to be addressed by any utility selecting either of these. (Note that the
dissolved iron for the Cleanit®-LC media is not particularly high, but visually it was apparent that
particulate iron release was very high [see Figure 2.1]).
15

Table 2.7
Silicon, iron, manganese, uranium, and arsenic concentrations after 24
hours of contact time
Dose
Contact
Utility A
Utility A
Utility C
Utility C
Media
Utility B
Utility D
Utility E
/L
Time hr
Well A
Well B
Well A
Well B
Silicon (mg/L as Si)
Raw water
-
-
10.1 ®
11.7
6.1
11.5
8.0 1 5.0
26.3
SBG-1
4
24
10.2
12.4
5.8
11.7
7.5
5.0
25.2
A600/9149
4
24
10.2
12.3
5.8
11.5
7.5
4.9
24.6
Cleanit®-LC
4
24
3.1
I 1.8
2.9
_
1.3
1.7
I 3.2
6.2
SIR-700
4
24
10.2
12.3
5.9
_
11.7
7.6
4.9
25.6
S106
4
24
10.3
12.4
5.9
_
11.3
7.7
5.0
25.6
SMI
0.8
24
7.2
9.8
4.7
10.2
5.8
3.7
16.6
Iron (,u g/L)
Raw water
-
-
< 10.0
16.3
< 10.0
34.1
23.6
34.9
< 10.0
SBG-1
4
24
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
A600/9149
4
24
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
Cleanit®-LC
4
24
< 10.0
22.6
44.0
< 10.0
18.2
18.1
16.8
SIR-700
4
24
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
S106
4
24
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
SMI
0.8
24
10,300
20,700
3,000
56,600
3,070
2,010
21,800
Manganese (,u g/L)
Raw water
-
-
<1.0
<1.0
<1.0
2.2
<1.0
<1.0
<1.0
SBG-1
4
24
<1.0
<1.0
<1.0
2.1
<1.0
<1.0
<1.0
A600/9149
4
24
< 1.0
< 1.0
< 1.0
2.1
< 1.0
< 1.0
< 1.0
Cleanito-LC
4
24
36.0
74.4
33.6
3.0
< 1.0
32.9
38.7
SIR-700
4
24
<1.0
<1.0
<1.0
2.2
<1.0
<1.0
<1.0
S106
4
24
<1.0
<1.0
<1.0
4.0
<1.0
<1.0
<1.0
SMI
0.8
24
303
299
158
379
119
245
556
Uranium (,u g1L)
Raw water
-
-
2.5
3.9
4.4
12.1
2.7
11.4
< 1.0
SBG-1
4
24
<1.0
<1.0
<1.0
<1.0
<1.0
<1.0
<1.0
A600/9149
4
24
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
Cleanit°-LC
4
24
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
4.1
< 1.0
SIR-700
4
24
<1.0
<1.0
<1.0
<1.0
<1.0
<1.0
<1.0
S106
4
24
<1.0
<1.0
<1.0
<1.0
<1.0
<1.0
<1.0
SMI
0.8
24
<1.0
1.0
<1.0
2.8
<1.0
<1.0
<1.0
Aresnic (u g/L)
Raw water
-
-
3.9
< 0.5
1.4
21.5
6.1
4.9
0.6
SBG-1
4
24
< 0.5
< 0.5
n/m
8.8
< 0.5
< 0.5
< 0.5
A600/9149
4
24
< 0.5
< 0.5
n/m
9.1
< 0.5
< 0.5
< 0.5
Cleanit®-LC
4
24
< 0.5
< 0.5
n/m
< 0.5
< 0.5
< 0.5
< 0.5
SIR-700
4
24
< 0.5
< 0.5
n/m
3.8
< 0.5
< 0.5
0.5
S106
4
24
<0.5
<0.5
n/m
5.9
<0.5
<0.5
<0.5
SMI
0.8
24
<0.5
<0.5
n/m
<0.5
<0.5
<0.5
<0.5
n/m = not measured
Results for Adsorption Isotherm Parameters
In most instances the Freundlich isotherm was a better fit for Cr(VI) adsorption than the
Langmuir isotherm based on the correlation coefficients. In three cases (Utility D water with
SBG1 and A600E/9149 media and Utility C Well B with A600E/9149 media) either a data point
was missing or the Cr(VI) concentration did not always decrease as the amount of media increased
16

so these were excluded from further analysis. The two iron -based media were excluded from this
analysis due to the low concentrations of Cr(VI).
A summary of the Freundlich isotherm data is included as Table 2.8. This table includes
the major water quality parameters, values for the Freundlich isotherm variables, and the two
values Q8 and Q 10. Q8 is defined as the amount of Cr(VI) removed (in units of µg) per amount
of media (in units of mg) when the treated water Cr(VI) concentration is 8 µg/L. Likewise, Q10
is defined as the amount of Cr(VI) removed (in µg) per amount of media (in mg) when the treated
water Cr(VI) concentration is 10 µg/L (the California MCL). With this data, a utility could
estimate the amount of media required per volume of water treated. For example, if Utility X
needed to treat water that contained 50 µg/L Cr(VI) and suppose their water chemistry was similar
to that of Utility B. If they wanted to use the ResinTech SBG1 media, the Q8 value is 0.183 µg/mg.
The calculation to estimate the amount of media required is shown in Equation 2.1:
[50 µg Cr(VI)/L — 8 µg Cr(VI)/L] / [0.183 µg Cr(VI) sorbed/mg
media required] = 230 mg media per L of water treated (2.1)
Keep in mind that this is just an estimate. Bench -scale and pilot testing is highly
recommended before a final design is selected.
17

Table 2.8
Summary of Freundlich isotherm parameters
Cr(VI)
Na
Ca
Mg
Si
Cl
SO4
Alkalinity
Freundlich
Isotherm
Q8
Q10
Media
-
2
Source Water
ug/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L as CaCO3
Kf
1/n
R
ug/mg
ug/mg
1
90.3
42.1
14.3
2.8
6.1
8.5
50.0
90
0.0624
0.517
0.997
0.183
0.205
Utility B
m
_
103
37.3
74.9
7.4
10.1
30.5
88.8
148
0.0459
0.572
0.973 -
0.151
0.171
Utility A - Well A
101
13.2
98.0
17.9
11.7
35.4
87.4
184
0.0342
0.550
0.997-
0.107
0.121
UtilityA -WellB
Gj
140
223
37.0
6.3
11.5
215
130
87
0.0161
0.671
0.993
0.065
0.076
-
Utility C - Well A
c
105
48.9
35.2
67.3
26.3
53.9
49.6
308
0.0459
0.659
-
1.000
0.181
0.209
Utility E
v
°C
77.9
54.6
5.0
1.9
7.6
16.6
16.8
94
0.0845
0.524
0.998
0.251
0.283
Utility C - Well B
90.3
42.1
14.3
2.8
6.1
8.5
50.0
90
0.0610
0.455
0.946
0.157
0.174
Utility B
103
37.3
74.9
7.4
10.1
30.5
88.8
148
0.0447
0.457
0.895
0.116
0.128
Utility A - Well A
= m
0 0
101
13.2
98.0
17.9
11.7
35.4
87.4
184
0.0383
0.577
-
0.997
0.127
0.145
Utility A -Well B
a'
140
223
37.0
6.3
11.5
215
130
87
0.0147
0.698
0.996
0.063
0.073
Utility C - Well A
105
48.9
35.2
67.3
26.3
53.9
49.6
308
0.0450
0.678
0.993
0.184
0.214
Utility E
0
90.3
42.1
14.3
2.8
6.1
8.5
50.0
90
0.0439
0.579
0.975
0.146
0.166
Utility B
o
103
37.3
74.9
7.4
10.1
30.5
88.8
148
0.0432
0.533
-
0.998
0.131
0.147
Utility A - Well A
„A
101
13.2
98.0
17.9
11.7
35.4
87.4
184
0.0388
0.581
0.999
0.130
0.148
Utility A -Well B
v
140
223
37.0
6.3
11.5
215
130
87
0.0323
0.569
0.996
0.105
0.120
Utility C - Well A
-
105
48.9
35.2
67.3
26.3
53.9
49.6
308
0.0343
0.675
0.998
0.139
0.162
Utility E
a,
77.9
54.6
5.0
1.9
7.6
16.6
16.8
94
0.0875
0.602
0.999_
0.306
0.350
Utility C - Well B
86.7
113
8.2
5.9
5.0
18.4
13.4
230
0.0293
0.519
0.990
0.086
0.097
Utility D
90.3
42.1
14.3
2.8
6.1
8.5
50.0
90
0.0269
0.648
0.992
0.104
0.120
Utility B
0
103
37.3
74.9
7.4
10.1
30.5
88.8
148
0.0215
0.732
0.999
0.098
0.116
Utility A - Well A
-
v
101
13.2
98.0
17.9
11.7
35.4
87.4
184
0.0196
0.712
0.998
0.086
0.101
Utility A -Well B
01
140
223
37.0
6.3
11.5
215
130
87
0.0215
0.626
0.999
0.079
0.091
Utility C - Well A
°
105
48.9
35.2
67.3
26.3
53.9
49.6
308
0.0188
0.799
0.995
0.099
0.118
Utility E
a
77.9
54.6
5.0
1.9
7.6
16.6
16.8
94
0.0483
0.619
0.991
0.175
0.201
Utility C - Well B
86.7
113
8.2
5.9
5.0
18.4
13.4
230
0.0263
0.765
0.993
0.129
0.153
Utility D
Q8 = µg Cr(VI) removed / mg media, with 8 µg/L Cr(VI) source
Q 10 = µg Cr(VI) removed / mg media, with 10 µg/L Cr(VI) source
18

EFFECT OF COMPETING SOLUTES ON HEXAVALENT CHROMIUM REMOVAL
As discussed previously, anionic solutes could compete with chromate for adsorption sites
on certain ion exchange media and this could dramatically impact the amount of media required
to remove Cr(VI) to an acceptable level. These species include sulfate, silicon, chloride, nitrate,
alkalinity (bicarbonate), and natural organic matter (NOM). A study was conducted as part of this
project to evaluate each of the ion exchange media for their ability to adsorb Cr(VI) when these
competing solutes were present.
For this experiment synthetic water with 100 mg/L as CaCO3 of alkalinity was used as our
baseline water. Additionally, 20 mg/L calcium, 4 mg/L magnesium, 30 mg/L sodium, and
1 mg/L potassium were added. The pH and anionic species concentrations were manipulated so
that a low, medium, and high concentration of each species of interest could be evaluated
(Table 2.9). These concentrations were selected based on the 10, 50, and 90 percentile
concentrations of these constituents in United States' waters (Snoeyink and Jenkins 1980).
Potassium chromate (Matheson Coleman & Bell, ACS grade) was added to each test water so that
an initial concentration of approximately 100 µg/L Cr(VI) was present. Two g/L of each media
(except 0.4 g/L for the SMI media) was used for all solute concentrations.
Table 2.9
Nominal concentrations of comnetinLy solutes tested in this studv
Constituent
Concentration
Unit
Low Medium Medium High
Sulfate
15
50
100
250
mg/L
Silicate
0
5
10
40
mg/L as Si02
Chloride
5
50
100
250
mg/L
Alkalinity (bicarbonate)
-
100
200
300
mg/L as CaCO3
TOC
0
2
4
6
mg/L as C
Nitrate
0
2
3
5
mg/L as N
Sulfate
Sulfate was varied by addition of sodium sulfate. Four levels of sulfate were tested,
including 16, 49, 100, and 251 mg/L (`as measured' concentrations). Cr(VI) concentrations after
30 minutes of exposure were inconclusive in showing the effect of sulfate and exceeded the
California MCL for the SBA and WBA media at all sulfate concentrations tested (Figure 2.3).
However, after 4 hours of exposure, it was clear that an increase in sulfate resulted in decreased
Cr(VI) removal (Figure 2.4). The SBG1 SBA media did not perform as well as the other media in
this test, and none of the SBA or WBA media met the California MCL in the presence of 251 mg/L
sulfate. After 24 hours of contact time all Cr(VI) concentrations were less than the MCL except
for the WBA media S 106 (15.5 µg/L; data not shown).
19

Figure 2.3 Hexavalent chromium concentration after 30 minutes of contact time with
varying concentrations of sulfate
45
■ SO4=16 mg/L
40
■ 5O4=49 mg/L
35 0 SO4z100 mg/L
30 ■ SO4=251 mg/L
J
Q 25
a
L 20
V
15
10 Califo Cr(VI) MCL
MMI
SBG-1 A600/9149 CleanitO-LC SIR-700 S106 SMI
Figure 2.4 Hexavalent chromium concentration after 4 hours of contact time with varying
concentrations of sulfate
20

Silicon
Four levels of silicon were evaluated: 0, 2.2, 4.4, and 17.1 mg/L as Si (Si was added as
sodium metasilicate) (0, 4.7, 9.4, and 36.6 mg/L as SiO2). The alkalinity was approximately 100
mg/L as CaCO3 prior to silicon addition, but increased to 110, 120, and 160 mg/L for the different
amounts of silicon. Initial Cr(VI) was approximately 100 µg/L. Cr(VI) concentrations after 30
minutes of contact were inconclusive in showing the effect of silicon and exceeded the California
MCL for the SBA and WBA media at all silicon concentrations tested (Figure 2.5). However,
after 4 hours of contact, it was clear that an increase in silicon resulted in decreased Cr(VI) removal
for the two SBA media (SBG1 and A600E/9149) and had little effect on the two WBA media
(SIR-700 and S 106) (Figure 2.6).
Figure 2.5 Hexavalent chromium concentration after 30 minutes of contact time with
varying concentrations of silicon
21

so
a Si=O mg/L
45
■ Si=2.2 mg/L
40 ■ Si=4.4 mg/L
35 ■ Si=17.1 mg/L
30
tW
25
20
15
10 California Cr(VI) MCL
5
SBG-1 A600/9149 Cleanit®-LC SIR-700 S106 SMI
Figure 2.6 Hexavalent chromium concentration after 4 hours of contact time with varying
concentrations of silicon
Chloride
Four levels of chloride were evaluated: 7.5, 43, 85, and 227 mg/L (chloride was added as
potassium chloride). The alkalinity was approximately 100 mg/L as CaCO3. Initial Cr(VI) was
approximately 100 µg/L. Cr(VI) concentrations after 30 minutes of contact were once again
inconclusive in showing the effect of chloride (Figure 2.7). After 4 hours of contact, results were
also inconclusive (Figure 2.8). For the two SBA media (SBG1 and A600E/9149) as chloride
increased to 85 mg/L, the Cr(VI) removal actually increased; however, at 227 mg/L chloride the
media were less effective. For the two WBA media (SIR-700 and S 106) there was little effect on
Cr(VI) as chloride increased, although SIR-700 showed a spike in Cr(VI) at 43 mg/L chloride.
After 24 hours of contact, however, Cr(VI) was removed to below 2 µg/L in all cases (data not
shown).
22

Figure 2.7 Hexavalent chromium concentration after 30 minutes of contact time with
varying concentrations of chloride
Figure 2.8 Hexavalent chromium concentration after 4 hours of contact time with varying
concentrations of chloride
23

Alkalinity
In the alkalinity test, three levels of alkalinity were evaluated by adding differing amounts
of sodium bicarbonate. Nominally, these levels were 100, 200, and 300 mg/L as CaCO3. Except
for SIR-700 (one of the WBA media), Cr(VI) removal decreased as alkalinity increased after 30
minutes of contact (Figure 2.9). After 4 hours, however, no consistent trend could be seen,
although in general the two SBA media outperformed the two WBA media (Figure 2.10). Cr(VI)
concentrations were quite low after 24 hours contact time in all cases with concentrations below 2
µg/L (data not shown).
Figure 2.9 Hexavalent chromium concentration after 30 minutes of contact time with
varying levels of alkalinity
24

1s —
■ Alik=100
16 ■ A1k=200
■ A1k=300
14 —
12
= California Cr(VI) MCI.
10
s
u
6 — —
4
2
0 1
56G-1 A600/9149 C9eanit"AC SIR-700 5106 SMI
Figure 2.10 Hexavalent chromium concentration after 4 hours of contact time with varying
levels of alkalinity
Organic Carbon
Four levels of total organic carbon (TOC) were evaluated by adding different amounts of
Suwanee River Fulvic Acid II purchased from the International Humic Substances Society (IHSS).
Nominally, these levels were 0, 2, 4, and 6 mg C/L, but values were measured as 0.7, 1.9, 3.3, and
4.7 mg C/L. After 30 minutes and 4 hours of contact there appeared to be no effect on Cr(VI)
removal (Figures 2.11 and 2.12). Cr(VI) concentrations were quite low after 24 hours contact time
in all cases except SBG1 with no added TOC where the Cr(VI) was still 8.8 µg/L (data not shown).
Keep in mind that other types of TOC and naturally occurring organic matter may behave
differently.
25

Figure 2.11 Hexavalent chromium concentration after 30 minutes of contact time with
varying levels of TOC
50
M TOC=0.7 mg C/L
45
® TOC=1.9 mg C/L
40
- TOC=33 mg C/L
35
TOC=4.7 mg C/L
J 30
_ 25
i
U 20
15
California Cr(VI) MCL
10
5
i
0
SBG-1 A600/9149 +Cleanits-LC SIR-700 S106 SMI
Figure 2.12 Hexavalent chromium concentration after 4 hours of contact time with varying
levels of TOC
26

Nitrate
Four levels of nitrate were evaluated by adding differing amounts of sodium nitrate.
Nominally, these levels were 0, 2, 3, and 5 mg/L as N. After 30 minutes of contact, the highest
level of nitrate appeared to decrease Cr(VI) removal for the two SBA media (SBG1 and
A600E/9149, Figure 2.14). This trend also continued after 4 hours of contact (Figure 2.13).
Additionally, after 4 hours of contact, the two WBA media (SIR-700 and S 106) showed increasing
Cr(VI) concentrations as the nitrate level increased (Figure 2.14). Note that the 5 mg/L nitrate
concentration for SIR-700 did not run correctly so no data is available for this condition. Cr(VI)
concentrations were quite low after 24 hours contact time in all cases with concentrations below
0.6 µg/L (data not shown).
Figure 2.13 Hexavalent chromium concentration after 30 minutes of contact time with
varying levels of nitrate
27

6
■ Nitrate = 0 mg N/L
5 ■ Nitrate = 2 mg N/L
■ Nitrate = 3 mg N/L
a
Nitrate = S mgN/L
J
1
M
7
r. 3
7
J
Z
no
2 E
U)
_ O
ra
1 rp
ra
C 111
58G-1 A600/9149 Cleanit'-LC SIR-700 5106 SMl
Figure 2.14 Hexavalent chromium concentration after 4 hours of contact time with varying
levels of nitrate
28

CHAPTER 3
WATER QUALITY IMPACTS ON RESINS AND MEDIA PERFORMANCE
Small-scale column tests were conducted using the two SBA media and the Purolite S 106
WBA media after completion of the batch -scale isotherm testing. These media were selected for
this testing because, in the majority of circumstances, SBA will be the least expensive and least
complex technology for small systems to implement for Cr(VI) removal. In the cases where sulfate
concentration might be high enough to inhibit SBA efficiency, the next most likely candidate
would be WBA media. The column tests are critical in that they provide information on the
breakthrough of Cr(VI) at the targeted empty bed contact time (EBCT). This allows one to predict
the life of the resin/media which, in turn, allows one to predict the yearly cost of operation. The
column tests also created media/resin that could be tested for chromium leaching characteristics
that might impact resin disposal in landfills. The small-scale column tests conducted in this study
were used to evaluate the effect of various sulfate concentrations, nitrate, and arsenic on the
performance of each media.
MATERIALS AND METHODS
Small -Scale Column Tests
Twenty-one small-scale column tests were conducted during the course of this study.
These were conducted in seven groups of three — Purolite A600E/9149 (SBA) and ResinTech
SBG 1 (SBA) and Purolite S 106 (WBA) resins were evaluated in seven different tests. The column
testing set-up is shown in Figure 3.1. Water is mixed in a 180-liter barrel and transferred to three
20-liter buckets (one for each resin test). Water is pumped from each of buckets to the top of an
ion exchange column using a peristaltic pump. For the first two groups of tests the water was
allowed to flow downward through each column by gravity. Due to the fairly rapid buildup of
pressure drop however, the system was converted to a pressure system as depicted in Figure 3.1.
The effluent from each column flowed into a nearby sink.
Each column test was conducted using an empty bed contact time (EBCT) of two minutes.
This is calculated by dividing the water flow rate (mL/min) by the volume of the column (mL).
The columns used in this study had an inner diameter of 0.5" (12.7 mm) and the media height was
8" (200 mm) for all tests.
The baseline water used in each test was prepared using distilled water, calcium chloride,
sodium bicarbonate, magnesium sulfate, potassium sulfate, and potassium chromate. Baseline
concentrations of most elements varied slightly but alkalinity was 100 mg/L as CaCO3 and
hexavalent chromium was 100 µg/L as Cr for all tests. The pH was approximately 8.0 for the two
SBA media tests. Per the supplier's recommendation and previous work, the pH was lowered to
approximately 6.0 for the WBA media test by sparging the water with CO2 (g).
Effluent samples were collected from each column at least three times per day and analyzed
for Cr(VI) and other metals.
29

Figure 3.1 Photo of small-scale column test setup
Leaching Tests
Upon completion of the column testing, the spent media will be evaluated using the
Toxicity Characteristic Leaching Procedure (TCLP) and the California Waste Extraction Test (CA
WET). These tests are used to determine if a waste is to be characterized as `hazardous' in terms
of disposal. These tests were designed to simulate leaching in a landfill environment although,
typically, the CA WET is the more aggressive of the two.
The TCLP is described in EPA Method 1311 (EPA 1992). The first step in this method is
to determine which of the extraction fluids should be used. Five grams of each media (ResinTech
SBG1, Purolite A600E/9149, Purolite S106) were placed in glass beakers with 96.5 mL of
nanopure water. After stirring for 5 minutes the pH readings were 4.23, 4.20, and 4.90 for each
media, respectively. Since all these were below pH 5 extraction fluid #1 was used for the TCLP
testing. This fluid is prepared by adding 5.7 mL glacial acetic acid and 64.3 mL 1-N sodium
hydroxide in about 500 mL nanopure water and diluting up to 1 L with nanopure water.
In order to evaluate whether the difference in chromium loading at the top of each column
versus the bottom of each column, the media from each column was divided into two halves and
each half was mixed prior to collecting samples. Two grams of media was collected and placed
in a 40 mL glass vial with 40 mL of the TCLP extraction fluid (1:20 ratio as specified in method).
This was done for the media from the top and the bottom of each column for each of the first five
small-scale column tests as well as for two samples of new media (control). All samples were
placed on a rotator operating at 30 rpm for 18 hours. Samples were then diluted 1:10 and analyzed
by ICP-MS for chromium.
30

The media were also evaluated using the CA WET. The extraction fluid for this test is
prepared by dissolving 38.4 g of citric acid in 1 L of nanopure water and titrating to pH 5 with
sodium hydroxide.
The same sampling protocol was followed as in the TCLP testing with the following
exceptions. Four grams of media was collected and placed in a 40 mL glass vial with 40 mL of
the extraction fluid (1:10 ratio as specified in method). This was done for the media from the top
and the bottom of each column for each of the first five small-scale column tests as well as for two
samples of new media (control). All samples were placed on a rotator for 48 hours. Samples were
then diluted 1:10 and analyzed by ICP-MS for chromium.
RESULTS
Baseline Test (Gravity Fed)
Water was prepared with the following concentrations: 45 mg/L Na, 3.5 mg/L Mg, 16 mg/L
sulfate, 30 mg/L chloride, 1 mg/L potassium, 17 mg/L calcium, 100 µg/L Cr(VI) and
approximately 100 mg/L as CaCO3 alkalinity. During the test the WBA media (Purolite S 106)
developed a high pressure drop and we were only able to run to 4500 bed volumes (BV). At that
point no Cr(VI) was seen in the effluent. Also, the only co -competing solute, sulfate, was still
being removed (approximately 5 mg/L in effluent). The pressure drop through the two SBA media
(ResinTech SBG1 and Purolite A600E/9149) eventually increased as well and the test had to be
stopped after 6300 BV. As in the case of the WBA media, no detectable Cr(VI) was in the effluent
and sulfate was still being removed.
High Sulfate Test (Gravity Fed)
The second test was conducted after following some guidance from the Purolite technical
representative. The media was allowed to soak in distilled water for several hours prior to placing
it in its column. Also, after the media was placed in its column, it was backwashed with distilled
water for several minutes to remove the fine particulate matter present in the media. We also
added some height to the columns to allow for more pressure drop. These pre -treatments enabled
us to run the columns longer than the first test, but pressure drop still increased.
For the second test sulfate concentration was increased to approximately 150 mg/L. The
two SBA media built up pressure drop faster than the WBA media in this test and they had to be
shutdown after about 5300 BV. The WBA media (Purolite S 106) was operated until almost 7500
BV. Cr(VI) effluent results are shown in Figure 3.2.
31

40
}ReslnTech 5BG1
35
-wPurolite A600/9149
�J 30
-wPuroiite 5106
2
2.
E
20
X
w 10
s
a
0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000
# Bed Volumes Treated
Figure 3.2 Hexavalent chromium concentration in effluent during the 150 mg/L sulfate test
Cr(VI) effluent from the two SBA media increased rapidly after about 2000 BV and
reached breakthrough (defined as Cr(VI) > 8 µg/L) after 3600 and 4300 BV, respectively. The
WBA media actually achieved breakthrough at 1400 BV but the Cr(VI) effluent decreased later
and remained steady at about 5 µg/L until near the end of the test. Sulfate was removed nearly
completely for each media until it rapidly increased to its influent level at about 1000 BV.
Medium Sulfate Test (Pressure System)
For this test a medium amount of sulfate (60 mg/L) was added to the test water. Water was
prepared with the following concentrations: 65 mg/L Na, 3.5 mg/L Mg, 60 mg/L sulfate, 30 mg/L
chloride, 1 mg/L potassium, 17 mg/L calcium, 100 µg/L Cr(VI) and approximately 100 mg/L as
CaCO3 alkalinity. The columns were operated as described above and shown in Figure 3.1.
Cr(VI) removal by the two SBA media (ResinTech SBGI and Purolite A600E/9149) was
similar (Figure 3.3). Effluent Cr(VI) was low up until about 4,000 BVs treated and then rose
exponentially thereafter. Breakthrough of 8 µg/L Cr(VI) occurred at about 6,000 BVs and
exceedance of the Cr(VI) MCL occurred at about 6,500 BVs. The WBA media (Purolite S 106)
behaved differently. Effluent Cr(VI) concentration increased quickly to about 2 — 3 µg/L but only
gradually increased thereafter. By 8,000 BVs the effluent Cr(VI) had only eluted to about 7 µg/L.
At this point, the pressure drop had increased to a point where the flow could not be maintained
so the test was terminated. Sulfate was removed similarly by each media, becoming saturated at
about 1,200 — 1,500 BVs (Figure 3.4). One important point here is that each media continued to
remove Cr(VI) even after sulfate removal ended.
32

25
-*-ResinTech SBG1
20
fPurolite A600/9149
tw
a tPurolite S106
15
E
O
u
2R
x
x
4y
i
5
0 ■
0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000
# Bed Volumes Treated
Figure 3.3 Hexavalent chromium concentration in effluent during the 60 mg/L sulfate test
70
60
50
Off$ 40
E
-&-ResinTech SBG1
30
`" -e-Purolite A600/9149
20
fPurolite S106
1©
0
0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000
# Bed Volumes Treated
Figure 3.4 Sulfate concentration in effluent during the 60 mg/L sulfate test
Medium Sulfate Test with Added Nitrate and Arsenic (Pressure System)
Nitrate and arsenic were added for this test to evaluate Cr(VI) removal with a number of
competing solutes. Sodium arsenate was added to the same water as the previous test so that the
33

arsenic concentration was approximately 8 µg/L. Sodium nitrate was also added so that the nitrate
concentration was approximately 8 mg/L as N (due to a miscalculation only 1.5 mg/L nitrate was
added for up to 4,000 BVs). These concentrations were selected based on 80% of the MCLs for
each contaminant.
As in the previous test, Cr(VI) removal by the two SBA media (ResinTech SBG1 and
Purolite A600E/9149) was similar (Figure 3.5). Effluent Cr(VI) was low up until about 4,000 bed
volumes and then rose exponentially thereafter. Breakthrough of 8 µg/L Cr(VI) occurred at about
5,000 BVs and exceedance of the Cr(VI) MCL occurred at about 5,500 BVs. The WBA media
(Media E) behaved differently (but similar to how it behaved in the previous test). Cr(VI) quickly
rose to about 2 µg/L in the effluent but only gradually increased thereafter. By 7,000 BVs the
effluent Cr(VI) was still only about 7 µg/L. At this point the pressure drop had increased to a point
where the flow could not be maintained so the test was terminated.
35
-&-ResinTech SBG1
30
#PuroIote A600/9149
J
-a fPuro[ote 5106
3
20
to
s
U
a+ 15
C
W
10
W
5
0
0 1,000 2,,000 3,000 4,000 5,000 6,000 7,ODO 8,000
# Bed Volumes Treated
Figure 3.5 Hexavalent chromium concentration in effluent during the 60 mg/L sulfate test
with 8 µg/L arsenic and 8 mg/L nitrate
Once again, sulfate was removed similarly by each media, becoming saturated at about
1,300 — 1,500 BVs (Figure 3.6). Arsenic was also removed during the first 1,000 BVs; however,
at that point arsenic in the effluent rose dramatically (to 25 µg/L in one case even though the
influent was only 8 µg/L), demonstrating the potential for chromatographic peaking when sulfate
and/or nitrate is also present (Figure 3.7). After about 1,500 BVs arsenic effluent was equivalent
to the influent. Nitrate also behaved in a similar manner as arsenic, except there was not an obvious
chromatographic peak for the WBA media (Figure 3.8).
34

s0
70
60
J 50
E -*-ResinTech 5'BG1
40
y
-wPurolite A600/9149
V1 30
#Purolite S106
20
10
0
0 1,000 2,000 3,000 4,000 5,000 6,000 7.000 3;000
# Bed Volumes Treated
Figure 3.6 Sulfate concentration in the effluent during the 60 mg/L sulfate test with 8 µg/L
arsenic and 8 mg/L nitrate
,_��
25 ResinTech SBG1
e-Puralite A600/9149
20
-wPurolite S106
Ob
u 15
m
L
a
10
5
0
0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000
# Bed Volumes Treated
Figure 3.7 Arsenic concentration in the effluent during the 60 mg/L sulfate test with 8 µg/L
arsenic and 8 mg/L nitrate
35

Figure 3.8 Nitrate concentration in the effluent during the 60 mg/L sulfate test with 8 µg/L
arsenic and 8 mg/L nitrate
Medium Sulfate Test Repeated with Added Nitrate and Arsenic (Pressure System)
The previous test with added nitrate and arsenic was repeated, except sample collection
was performed more regularly, hourly instead of three times per day, for the time period between
700-1700 BVs of water treated. As in the previous test, Cr(VI) removal by the two SBA media
was similar (Figure 3.9). Effluent Cr(VI) was low up until about 4,000 BVs and then rose
exponentially thereafter. Breakthrough of 8 µg/L Cr(VI) occurred at about 5,000 BVs and
exceedance of the Cr(VI) MCL occurred at about 5,500 BVs. The WBA media (Purolite S106)
behaved differently (but similar to how it behaved in the previous test). Cr(VI) quickly rose to
about 2 µg/L in the effluent but only gradually increased thereafter. By 7,000 BVs the effluent
Cr(VI) was still only about 4 µg/L.
36

Figure 3.9 Hexavalent chromium concentration in effluent during the repeat 60 mg/L
sulfate test with 8 µg/L arsenic and 8 mg/L nitrate
Once again, sulfate was removed similarly by each media, becoming saturated at about
1,300 —1,500 BVs (Figure 3.10). Arsenic was also removed during the first 1,000 BVs; however,
at that point arsenic in the effluent rose dramatically (to 25 µg/L in one case even though the
influent was only 8 µg/L). The intensive sampling clearly demonstrates chromatographic peaking
of arsenic in the presence of nitrate and/or sulfate, with the effluent concentrations being
significantly higher (Figure 3.11). After about 1,500 BVs arsenic effluent was equivalent to the
influent. Nitrate also behaved in a similar manner and seemed to peak at about 15 mg/L for the
two SBA media. There was no significant peak for the WBA media (Figure 3.12).
37

Figure 3.10 Sulfate concentration in the effluent during the repeat 60 mg/L sulfate test with
8 µg/L arsenic and 8 mg/L nitrate
30
2S
�ResinTech SBG1
-►-Purolite ► 600/9149
20
-wPurolite 5106
J
t
WO
U 15
GU
a
10
5
0
1,o0c 2,000 3,000 4,000 5.000 6,000 7,000 F,000
# Bed Volumes Treated
Figure 3.11 Arsenic concentration in the effluent during the repeat 60 mg/L sulfate test
with 8 mg/L nitrate and 8 µg/L arsenic
38

Figure 3.12 Nitrate concentration in the effluent during the repeat 60 mg/L sulfate test with
8 µg/L arsenic and 8 mg/L nitrate
The effluent nitrate, arsenic and sulfate concentrations are combined into a single graph for
each media in Figures 3.13, 3.14 and 3.15 and are plotted as normalized concentrations (i.e.,
effluent concentration divided by influent concentration). These charts show the chromatographic
peaking (i.e., C/Co > 1.0) of arsenic and nitrate between 600-1800 BVs of water treated. Both the
SBA media act similarly, with nitrate peaking first, followed by arsenic. The point at which sulfate
concentration rises exponentially, coincides with the arsenic peak (-1100 BVs). It is clear that all
the chromatographic peaking phenomenon lie between 700-1400 BVs. The effluent
concentrations of all the solutes (except Cr(VI)) match that of the influent post-1400 BVs. This
was observed in the previous medium -sulfate column test as well.
39

Note: C/Co = effluent concentration / influent concentration
Figure 3.13 Nitrate, arsenic, and sulfate peaking for ResinTech SBG1 (60 mg/L sulfate small-
scale column test)
Figure 3.14 Nitrate, arsenic, and sulfate peaking for Purolite A600E/9149 (60 mg/L sulfate
small-scale column test)
40

Note: The small `blip' in nitrate, sulfate, and arsenic concentrations between 700 and 900 BVs
has not been explained. It is unlikely to be instrument error since these were analyzed using two
different instruments.)
Figure 3.15 Nitrate, arsenic, and sulfate peaking for Purolite S106 (60 mg/L sulfate small-
scale column test)
High Sulfate Test with Added Nitrate and Arsenic (Pressure System)
Sulfate was increased to 150 mg/L to evaluate the chromatographic peaking phenomenon
observed in the previous tests. We expected to see the breakthrough and the chromatographic
peaks occurring at lower bed volumes and so collected effluent samples every two hours on the
second day of the test.
Cr(VI) removal followed a similar trend as seen in our previous high- sulfate column test.
The SBA media breakthrough was at 2,500 BVs. The effluent Cr(VI) concentrations reached 50
µg/L at about 4,000 bed volumes, at which point the test was ended for both SBA media. The
WBA media saw a brief period of breakthrough (peaking at 10 µg/L) between 1,600-2,200 BVs.
The effluent Cr(VI) concentration decreased to about 6 µg/L and stayed at that level until 7,000
BVs, at which point, the test was terminated (Figure 3.16).
As expected, the peaking of arsenic (Figure 3.17) and nitrate (Figure 3.18) occurred much
earlier than in the medium sulfate concentration test. Unfortunately, the intensive sampling period
did not effectively capture the peaks, as it was even faster than we anticipated. The trend in sulfate
removal (Figure 3.19) was uniform, with saturation occurring at 600 BVs. This also was faster
than the previous medium -sulfate test, where it occurred at 1,000 BVs.
41

70
60
J
A 50
7
E
40
0
L
prr
V
f+ 30
M
z 20
a
2
10
-*-ResinTech SBG1
-wPurolite A600/9149
-FPurolite S106
o -
0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000
# Bed Volumes Treated
Figure 3.16 Hexavalent chromium concentration in effluent during the 150 mg/L sulfate
test with 8 µg/L arsenic and 8 mg/L nitrate
40
A ResinTech SBG1
-wPurolite A600/9149
30
--Purolite S106
J 25
do
7
v 20
.F
ev
L
@ 15
10
5
0
0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000
# Bed Volumes Treated
Figure 3.17 Arsenic concentration in effluent during the 150 mg/L sulfate test with 8 mg/L
nitrate and 8 µg/L arsenic
42

Figure 3.18 Nitrate concentration in effluent during the 150 mg/L sulfate test with 8 µg/L
arsenic and 8 mg/L nitrate
180
160
140
120
J
E100
6J
euv so
75
}Resiffech SBG1
60
r
-P-Purolite A600/9149
40
fPur+olite S106
20
v.
0
1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000
# Bed Volumes Treated
Figure 3.19 Sulfate concentration in effluent during the 150 mg/L sulfate test with 8 µg/L
arsenic and 8 mg/L nitrate
The effluent nitrate, arsenic and sulfate concentrations for the high sulfate concentration
test are combined into a single graph for each media in Figures 3.20, 3.21 and 3.22 and are plotted
43

as normalized concentrations (i.e., effluent concentration divided by influent concentration).
These charts show the chromatographic peaking (i.e., C/Co > 1.0) of arsenic and nitrate between
300-600 BVs of water treated. Both the SBA media act similarly, with nitrate and arsenic peaking
at approximately the same time (difficult to distinguish due to few samples taken that early in
testing). The point at which sulfate concentration rises exponentially, coincides with the end of
the arsenic peak (-600 BVs). It is clear that all the chromatographic peaking phenomenon lie
between 300-600 BVs. The effluent concentrations of all the solutes (except Cr(VI)) match that
of the influent post-600 BVs.
Figure 3.20 Nitrate, arsenic, and sulfate peaking for the ResinTech SBG1 (150 mg/L sulfate
small-scale column test)
44

Figure 3.21 Nitrate, arsenic, and sulfate peaking for Purolite A600E/9149 (150 mg/L sulfate
small-scale column test)
Figure 3.22 Nitrate, arsenic, and sulfate peaking for the Purolite S106 (150 mg/L sulfate
small-scale column test)
45

Low Sulfate Test with Added Nitrate and Arsenic (Pressure System)
For the final column test, we decreased the sulfate to 20 mg/L, with 8 mg/L of nitrate and
8 µg/L of arsenic. The sampling frequency was increased to five times a day for the first half of
the test in an attempt to capture the chromatographic peaks, if there were any.
Breakthrough of Cr(VI) was not observed for any media through the end of the test at 5000
BVs, which is consistent with our previous low sulfate (baseline) column test. The Cr(VI) chart
is not shown as the effluent concentrations were below our reporting level of 1 µg/L.
Arsenic peaked at about 2,000 BVs for all the media and came down to the influent
concentration post 3,000 BVs (Figure 3.23). Nitrate peaked between 1,800-2,200 BVs for the
SBA media and no significant peak was seen for the WBA media (Figure 3.24). The nitrate
concentrations came down to influent levels by 3,500 BVs. Sulfate levels reached saturation for
all the media by 3,200 BVs (Figure 3.25). Clearly, decreasing the sulfate levels slowed the
chromatographic peaking and sulfate saturation time, as compared to the medium- and high -sulfate
column tests.
12
10
8
J
i1q
3
� 6
Ql
2 -A-ResinTech SBG1
4
-*-Purolite A600/9149
--Purolite 51.06
z
0
0 1,000 2,00Q 3,000 4,000 5,000 6,000 7,000 8,000
# Bed Volumes Treated
Figure 3.23 Arsenic concentration in the effluent during the 20 mg/L sulfate test with 8
mg/L nitrate and 8 µg/L arsenic
46

0
0
-*-ResinTech SBG1
♦-Purolite A600/9149
-wPurolite S106
1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000
# Bed Volumes Treated
Figure 3.24 Nitrate concentration in effluent during the 20 mg/L sulfate test with 8 mg/L
nitrate and 8 µg/L arsenic
25
20
61
&-ResinTech SBG1
♦Purolite A600/9149
FPurolite S106
0
0 1,000 2,000 3.00-3 4,000 5,000 6,000 7,000 8,000
#'Bed Vo I u mes Treated
Figure 3.25 Sulfate concentration in effluent during the 20 mg/L sulfate test with 8 mg/L
nitrate and 8 µg/L arsenic
The effluent nitrate, arsenic and sulfate concentrations for the low sulfate concentration
test are combined into a single graph for each media in Figures 3.26, 3.27 and 3.28 and are plotted
as normalized concentrations (i.e., effluent concentration divided by influent concentration).
47

These charts show a wider and less sharp chromatographic peaking (i.e., C/co > 1.0) of arsenic and
nitrate between 800-3500 BVs of water treated. Both the SBA media acted similarly. The point
at which sulfate concentration rose exponentially coincides with the end of the arsenic peak
(-3000-3500 BVs). The effluent concentrations of all the solutes (except Cr(VI)) match that of
the influent post-3500 BVs. For the WBA media (Figure 3.28), no nitrate peaking was observed
although arsenic still peaked between 1000 and 2500 BVs so WBA might be a more attractive
option if nitrate is an issue.
1.4
1.2
1
0.8
0
u
u
0.6
+Nitrate
0.4
—Arsenic
+Sulfate
0.2
-Cr(VI)
0
0
1000 2000 3000 4000 5000 6000
# Bed Volumes Treated
Figure 3.26 Nitrate, arsenic, and sulfate peaking for ResinTech SBG1 (20 mg/L sulfate
small-scale column test)
48

1.6
1.4
1.2
1
d
0.8
-*-Nitrate
0,5
Arsenic
° -*-Sulfate
0.2
Cr(VI)
a
0 1000 2000 3000 4000 5000 6000 7000 8000
# Bed Volumes Treated
Figure 3.27 Nitrate, arsenic, and sulfate peaking for Purolite A6O0E/9149 (20 mg/L sulfate
small-scale column test)
1.6
1.4
1.2
1
0
0.8
u
-♦-Nitrate
0.6
Arsenic
OA -wSulfate
0.2 #Cr(VI)
0
0 1.000 2000 3000 4000 5000 6000 7000 8000
# Bed Volumes Treated
Figure 3.28 Nitrate, arsenic, and sulfate peaking for Purolite S1O6 (20 mg/L sulfate small-
scale column test)
49

Summary of Chromatographic Peaking Results
Sulfate concentration is a key driver in the phenomenon of `chromatographic peaking' for
the waters tested. A summary of the key characteristics observed in the tests described above are
given in Table 3.1. For SBA media the peak arsenic and nitrate concentrations increased as the
sulfate concentration increased. Likewise, the time required to the start of the peaking was also
inversely correlated with sulfate concentration for SBA media. For WBA media, arsenic peaking
was also observed, although at higher sulfate concentrations the peak arsenic concentration is
much less than those observed in the SBA media columns. No nitrate peaking was observed for
the WBA media tests. No Cr(VI) peaking was observed in any of the column tests. These results
were in keeping with expectations based on previous studies.
Table 3.1
Summary of chromatoLyranhic neakine of arsenic and nitrate
Media
Media
Sulfate
Arsenic
Nitrate
Sulfate
Peak Duration (in BV)
Arsenic
Nitrate
Name
Type
(mg/L)
C/Co Peak
C/Co Peak
BV to C/Co =1
SBG-1
SBA
20
1.29
1.25
4000
1300-3400
1500-3800
A600/9149
SBA
20
1.38
1.23
3400
800-3000
1400-3000
S106
WBA
20
1.35
1.04
3400
1200-2400
n/a
SBG-1
SBA
60
2.85
1.94
1500
1000-1400
850-1300
A600/9149
SBA
60
3.12
1.80
1200
850-1400
800-1200
5106
WBA
60
1.60
1.07
1300
700-1300
n/a
SBG-1
SBA
150
3.64
2.14
650
400-650
500-600
A600/9149
SBA
150
4.57
1.96
700
400-650
500-600
5106
WBA
150
1.24
1.03
1400
500-1400
n/a
TCLP Test
Results of the TCLP testing for the first five column tests are presented in Table 3.2.
Several observations can be made. First, all top media samples had greater chromium leaching
than their respective bottom layer samples, indicating that loading is primarily in the top part of
the column, as would be expected. Second, the high sulfate loading in column test #2 resulted in
less chromium removed and therefore, less chromium was leached during the TCLP testing. Also,
the WBA media (Purolite S 106) exhibited the least TCLP leaching despite the fact that more
chromium was removed by this media. This may be a result of the pH of the leaching solution
(pH 5) which is not far removed from the optimum removal pH (pH 6-6.5) for this media.
Column tests 1 and 2 were gravity -fed tests while the remainder of the tests were with a
pressure feed system. This may explain the low TCLP results for the bottom of the SBA media
tests when gravity feed was being used.
Only two TCLP results exceeded the regulatory limit of 5 mg/L (5,000 µg/L). However,
in a real situation the media from the entire column would be tested as one, meaning in this case
the average TCLP for this column would be less than the regulatory limit.
50

Table 3.2
TCLP chromium concentrations
Column
Water Quality
TCLP
- Cr Concentration (ug/L)
Test
Sulfate Nitrate Arsenic
ResinTech SBG1
Purolite A600/9149
Purolite
5106
mg/L
mg/L as N
ug/L
top
bottom
top bottom
top
bottom
1
60
0
0
2,023
36
4,233 6
287
21
2
150
0
0
954
659
2,497 1,710
404
48
3
60
0
0
2,563
1,389
4,350 2,236
461
69
4
60
7
8
2,197
1,376
3,195 2,528
223
25
5
60
7.5
8
2,697
2,055
6,038 3,448
383
108
6
150
8
8.5
783
581
2,329 2,084
419
81
7
20
8
8
1,843
232
6,275 1,391
110
19
A further calculation was performed to determine the amount of chromium removed in
each column test and how this value related to the TCLP leaching amount. Chromium loading
was determined by calculating the amount of chromium removed at each effluent sample collection
time and integrating over the entire testing period. Data is shown in Table 3.3 in units of `mg
chromium per g media'. Likewise, the amount of chromium leached into TCLP extraction fluid
is shown in the same units so side -by -side comparisons can be made. From the data presented it
is apparent that only a fraction of the chromium that was originally removed is mobilized by the
TCLP extraction fluid.
Table 3.3
TCLP results expressed in terms of media loadin
Column
Test
Water Quality
Cr(VI) Loading
mg/gmedia
Cr Leached by TCLP (top)
mg/gmedia
Cr Leached by TCLP (bottom)
mg/gmedia
Sulfate Nitrate Arsenic
mg/L
mg/Las N
ug/L
SBG1
A600/9149
5106
SBG1
A600/9149
5106
SBG1
A600/9149
5106
1
60
0
0
0.76
0.76
0.70
0.040
0.085
0.006
0.001
0.000
0.000
2
150
0
0
0.58
0.61
0.84
0.019
0.050
0.008
0.013
0.034
0.001
3
60
0
0
0.92
0.91
0.92
0.051
0.087
0.009
0.028
0.045
0.001
4
60
7
8
0.83
0.84
0.86
0.044
0.064
0.008
0.028
0.051
0.002
5
60
7.5
8
0.89
0.88
0.94
0.054
0.121
0.008
0.041
0.069
0.002
6
150
8
8.5
0.45
0.46
0.81
0.016
0.047
0.008
0.012
0.042
0.002
7
20
8
8
0.64
0.88
0.87
0.037
0.126
0.002
0.005
0.028
0.000
California Waste Extraction Test
An accident occurred while the samples were rotating and several samples leaked. This
caused the markings on the vials to be washed off so we had no way of ascertaining which samples
were from which media or column test. Even so, we did analyze all the remaining samples with
ICP-MS. Of the 27 samples analyzed, 4 had concentrations greater than 5,000 µg/L chromium,
the regulatory limit.
51

CHAPTER 4
FULL SCALE APPLICATIONS GUIDANCE
This chapter has the practical guidance for small systems that are considering to implement
wellhead treatment of hexavalent chromium. This guidance is developed based on the results of
bench -scale testing discussed in the earlier chapters, findings of previous studies and projects
funded by Water Research Foundation and best professional judgment. The guidance provided in
this chapter is intended for conceptual planning purposes and it is not intended to take the place of
site -specific preliminary or detailed design work.
Capital cost opinions are expressed in March 2016 dollars, corresponding with an
Engineering News Record (ENR) 20-Cities Average Construction Cost Index (CCI) of 10,242.09.
O&M cost opinions are expressed in March 2016 dollars, corresponding with an Engineering
News Record (ENR) 20-Cities Average Skilled Labor Index (SLI) of 9771.84.
CANDIDATE TREATMENT TECHNOLOGIES
Several treatment technologies have been shown to effectively remove hexavalent
chromium from groundwater:
• Weak base anion (WBA) exchange
• Strong base anion (SBA) exchange
• Granular iron media (GIM)
• Reduction coagulation filtration (RCF)
• Reverse osmosis (RO)
Among these technologies, the WBA and SBA exchange processes are significantly
simpler to implement and easier to operate for small systems compared to the other processes.
Therefore, extended guidance is provided for the WBA and SBA exchange processes. This chapter
includes preliminary discussion of GIM, RCF and RO processes. It does not include the footprint
and cost information for GIM, RCF and RO processes since they are fairly complex processes for
small water systems to consider and implement.
Weak Base Anion (WBA) Exchange
Process Description
Ion exchange treatment processes involve the use of synthetic resin beads (or media) which
are saturated with an inert ion such as chloride or hydroxide. During water treatment, the inert ion
is exchanged with an unwanted ion such as chromate (Cr042-) in water. In order to accomplish the
exchange of unwanted ion from water with the inert ion in solid phase, a packed bed of ion
exchange resin media is used. Groundwater is passed through the bed in down flow mode until
the ion exchange resin media is exhausted. When the resin media is exhausted, breakthrough of
the contaminant (i.e., hexavalent chromium) will be observed.
The WBA process has been extensively evaluated and demonstrated in studies conducted
by the City of Glendale, CA, in partnership with the Los Angeles Department of Water and Power,
City of Burbank, City of San Fernando, the California Department of Public Health, the EPA and
53

the Water Research Foundation and other agencies (Brandhuber et al. 2004, McGuire et al. 2006,
Blute et al. 2013). The Glendale, CA studies indicated two possible mechanisms of hexavalent
chromium removal by WBA resin: exchange of chromate ion with chloride ion and reduction of
Cr(VI) to Cr(IIl) on the resin surface. These studies also confirmed that the WBA process requires
suppression of the influent water pH to 6.0 or less.
Shown in Figure 4.1 is a concept -level process flow diagram for the WBA exchange
treatment. This figure only shows the major equipment and chemical injection locations; it does
not include all the piping, valving, and instrumentation and control systems. As shown in the
figure, the influent water pH is adjusted to 6.0 or less using acid addition. The pH of the treated
water has to be adjusted to ambient water pH using caustic addition to avoid corrosion related
issues in the distribution system. The WBA treatment typically involves the use of two pressure
vessels with resin media operated in series. The influent water flows through the lead vessel and
then through the lag vessel. When there is a breakthrough of hexavalent chromium in the lag
vessel, the lead vessel is taken offline, and the resin media in the lead vessel is replaced with new
media. The lead vessel with the new media is moved to the lag position and lag vessel is moved
to the lead position by switching the inter -vessel valves. This lead -lag operation of the WBA resin
vessels result in better usage of the resin before replacement.
The WBA resin requires rinsing when the media is initially installed to remove any
preservatives and media fines that may be present. The WBA resin is backwashed whenever the
head loss through the vessels reaches a pre-set point. Backwashing frequency for WBA resin is
kept minimal to avoid an upset of the mass transfer zone and premature breakthrough of hexavalent
chromium. The spent backwash water is collected in a storage tank and gradually disposed of to
a sanitary sewer (if available), recirculated to the head of the plant or hauled off -site to a disposal
facility.
The exhausted WBA resin is normally not regenerated but is disposed of as a solid waste
after dewatering.
Groundwater =D14
FE �'
Static Mixerca
—
¢_
u PT 7
Cartridge Filter z fx}
a
. Finished Water
Static Mixer
Product
Rinse'
tckwashWater2'so'ts
(Intermittent) Waste Tank Hauled Off -Site j
Deposed to Sewer
Notes
1. WBA resin requires initial rinsing to remove preservatives.
a. WBA resin may require intermittent backwash i ng to manage headloss.
3. Red lines denote backwash and waste streams.
Figure 4.1 WBA resin treatment process flow diagram
54

Advantages and Disadvantages
The key strengths and weaknesses of the WBA process are summarized in Table 4.1.
Table 4.1
Strengths and weaknesses of WBA process
Strengths
WBA resins have longer run lengths and
Cr(VI) exchange capacities compared to SBA
resins.
WBA resin is operated as a single -use, non-
regenerable resin; it is a relatively simpler
process to operate and maintain.
WBA resin process results in minimal amount
of liquid waste streams (liquid waste stream
generated is less than 1 percent (%) of treated
water on a volume basis).
WBA resin process removes other
contaminants such as copper, vanadium and
uranium where they occur (Blute et al. 2012).
This is an advantage if these contaminants
also need to be removed.
Key Design Criteria
Weaknesses
WBA resin process requires pH adjustment to
6.0 or less which can result in higher chemical
costs for moderate -high alkaline waters.
Post -treatment pH adjustment requires
addition of caustic which can also increase the
overall operation costs.
Process requires storage and handling of
hazardous chemicals.
Exhausted or spent WBA resin can
accumulate high concentration of uranium,
and chromium and the waste can be classified
as radioactive or hazardous. This may result
in higher disposal costs.
The key design criteria for WBA treatment are summarized in Table 4.2.
Table 4.2
WBA treatment design criteria
Criteria Units Assumptions and Typical Values
System Configuration -- Lead — Lag Vessels, Series Operation
Hydraulic Loading Rate per gpm / sf 6 — 15
Vessel
Minimum Empty Bed Contact minutes 3
Time per Vessel
Minimum Resin Bed Depth ft 3-4
per Vessel
Rinse / Backwash Rate gpm / sf 1.5 — 2.0 to achieve 50-60 percent media
expansion.
(continued)
55

Table 4.2 (Continued)
Criteria Units Assumptions and Typical Values
Rinse / Backwash Duration minutes 10 — 30
Influent Water pH Target S. U. 6.0 or less
Treated Water pH Target S. U. Ambient groundwater pH.
Note. gpm/sf — gallons per minute per square foot; ft — feet; S.U. — standard units
Residuals Disposal Considerations
The WBA resin requires initial rinsing to remove preservatives and fines and intermittent
backwashing to control head loss. The spent rinse water and backwash wastewater can be collected
in a waste tank, analyzed and disposed to sanitary sewer (if available near the well site) or
transported to a publicly owned treatment works (POTW) facility for ultimate disposal.
The spent WBA resin is replaced with new resin. The spent resin is analyzed for potential
leachates using the Federal Toxicity Leaching Procedure (TCLP) and the California Waste
Extraction Test (WET). The toxicity limit for chromium in the leachate for TCLP testing is 5
mg/L. The soluble threshold limit concentration (STLC) and the total threshold limit concentration
(TTLC) under the California Title 22 for hexavalent chromium are 5 mg/L and 500 mg/kg,
respectively.
In addition to removing hexavalent chromium, the WBA resin can also remove
radionuclides such as uranium. If the groundwater contains radioactive compounds, then the spent
resin has to be analyzed for additional parameters as defined by the Nuclear Regulatory
Commission (NRC). Presence of radionuclides (e.g., uranium) on spent resin can result in its
classification as technologically enhanced naturally occurring radioactive material (TENORM).
Because the naturally occurring radioactive material (NORM) is concentrated due to human
activity, the spent resin is classified as TENORM. Most TENORM resins can be disposed to
landfills. However, the spent resin is classified as a low level radioactive waste (LLRW) if the
total uranium concentration exceeds 500 mg/kg. The waste disposal costs can be significant if the
spent resin is classified as LLRW as there are only a few facilities that can handle radioactive
wastes.
Water systems with uranium in groundwater can consider limiting the operational life of
WBA resin to avoid exceeding the LLRW threshold for radioactivity. Water systems can consider
co -mingling the spent WBA resin with absorbent materials such as bentonite clay to sequester the
free liquid and contain the total uranium concentration in aggregated resin to below 0.05 percent
trigger for radioactivity waste categorization (Blute et al. 2013).
Conceptual Treatment Footprints
The conceptual footprints for hexavalent chromium treatment using WBA resin for 0.5
million gallons per day (MGD), 1 MGD and 2 MGD groundwater plants are respectively shown
in Figure 4.2, Figure 4.3 and Figure 4.4. All major process units are shown in these figures.
However, the footprint and space requirements may vary based on site constraints, well pumping
rates and specific equipment requirements. The conceptual footprints include secondary
56

containment for all chemical and waste storage tanks. The WBA resin vessels may need to be
enclosed depending on the local climate conditions. The treatment footprints do not include the
space for well(s), ground storage tank(s), a pump station, or storm water detention.
---------------------
8 ft�
40 ft Lag Vessel
12
Access
45 ft
Note: Secondary Containment for all tanks are shown in dotted lines
Electrical
& 10 ft
Controls
10 ft
11
--------------
5 ft
-------------
Acid Tank
-------------
5 ft
-------------
Caustic Tank
-------------
5 ft
Chlorine Tank
Figure 4.2 Conceptual footprint for 0.5 MGD capacity Cr(VI) treatment using WBA resin
57

45 ft
------------------------
Electrical
10 ft & 10 ft
Controls
Lead Vessel
10 ft
L----------------------- 12 ft
---------------
--------------------------
5 ft
CLagVessel
Acid Tank
Access
----------------------- 5 ft
Caustic Tank
-------------
12 ft
5 ft
( )
Waste Tank
Chlorine Tank
50 ft
Note: Secondary Containment for all tanks are shown in dotted lines
Figure 4.3 Conceptual footprint for I MGD capacity Cr(VI) treatment using WBA resin
58

----------------------------
12 ft
Lead Vessel
-----------------------------
so ft 12 ft—
ft
Lag Vessel
Electrical
& 10 ft
Controls
10
----------------
12 ft
6)fftt
Access
Acid Tank
55 ft
Note: Secondary Containment for all tanks are shown in dotted lines
-----------------
6 ft
Caustic Tank
-----------------
6 ft
Chlorine Tank
Figure 4.4 Conceptual footprint for 2 MGD capacity Cr(VI) treatment using WBA resin
59

Budgetary -Level Cost Opinions
The budget -level capital cost opinions for 0.5 MGD, 1 MGD and 2 MGD hexavalent
chromium treatment using the WBA resin are summarized in Table 4.3, Table 4.4 and Table 4.5,
respectively. The capital cost opinions were developed by obtaining vendor quotations for all
major equipment, estimating the amount of concrete needed for slabs and facilities and applying
appropriate factors for installation, electrical, instrumentation and controls, general site civil,
valving / piping and appurtenances, and contractor's overhead and profit.
Table 4.3
Cabital cost obinion for 0.5 MGD Cr(VIl treatment usin! WBA resin
DESCRIPTION
CITY
UNIT MEAS.
UNIT COST
TOTAL COST
COMMENTS
Equipment
Acid Feed System
1
LS
$ 50,000
$
50,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Cartridge Filter
2
EA
$ 5,000
$
10,000
1 duty/1 stand-by
Ion Exchange Equipment
2
EA
$ 130,000
$
260,000
8-ft diameter Lead and Lag Vessels
IX Backwash Pumps
2
EA
$ 7,500
$
15,000
1 duty/1 stand-by
Backwash Waste Tank
1
EA
$ 30,000
$
30,000
10-ft diameter FRP Tank; 6,200 gallon
Discharge Pumps
2
EA
$ 5,000
$
10,000
1 duty/1 stand-by
Caustic Feed System
1
LS
$ 30,000
$
30,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Chlorine Feed System
1
LS
$ 30,000
$
30,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Flow Elements or Flow Meter
3
EA
$ 3,000
$
9,000
Flow measurements (with display)
Static Mixer
1
EA
$ 1,800
$
1,800
6-inch diameter mixer
WBA Resin
300
CF
$ 200
$
60,000
Initial Fill
Total Equipment Cost
$
506,000
Installation
30%
$
151,800
Electrical and Instrumentation &
20%
$
101,200
Control
General Site Civil
15%
$
75,900
Valves, Piping and Appurtenance
15%
$
75,900
Concrete
53
CY
$ 600
$
31,800
Equipment pads and other site
pavement
Total Direct Cost
$
943,000
Contractor's Overhead and Profit
15%
$
141,450
Contingency
30%
$
42,435
Total Construction Capital Cost
$
1,127,000
Planning, Engineering, Legal and
11%
$
123,970
Administration
Construction Admin
9%
$
101,430
Total Project Cost
$
1,353,000
Low Estimate
$
947,100
-30%
High Estimate
$
2,029,500
+50%
60

Table 4.4
Capital cost opinion for 1 MGD Cr(VI) treatment using WBA resin
DESCRIPTION
CITY
UNIT MEAS.
UNIT COST TOTAL COST
COMMENTS
Equipment
Acid Feed System
1
LS
$ 60,000
$
60,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Cartridge Filter
2
EA
$ 5,000
$
10,000
1 duty/1 stand-by
Ion Exchange Equipment
2
EA
$ 200,000
$
400,000
10-ft diameter Lead and Lag Vessels
IX Backwash Pumps
2
EA
$ 7,500
$
15,000
1 duty/1 stand-by
Backwash Waste Tank
1
EA
$ 30,000
$
30,000
10-ft diameter FRP Tank; 9,600 gallon
Discharge Pumps
2
EA
$ 5,000
$
10,000
1 duty/1 stand-by
Caustic Feed System
1
LS
$ 40,000
$
40,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Chlorine Feed System
1
LS
$ 40,000
$
40,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Flow Elements or Flow Meter
3
EA
$ 3,000
$
9,000
Flow measurements (with display)
Static Mixer
1
EA
$ 1,800
$
1,800
6-inch diameter mixer
WBA Resin
600
CIF
$ 200
$
120,000
Initial Fill
Total Equipment Cost
$
736,000
Installation
30%
$
220,800
Electrical and Instrumentation & Con 20%
$
147,200
General Site Civil
15%
$
110,400
Valves, Piping and Appurtenance
15%
$
110,400
Concrete
53
CY
$ 600
$
31,800
Equipment pads and other site
pavement
Total Direct Cost
$
1,357,000
Contractor's Overhead and Profit
15%
$
203,550
Contingency
30%
$
61,065
Total Construction Capital Cost
$
1,622,000
Planning, Engineering, Legal and Ada 11%
$
178,420
Construction Admin
9%
$
145,980
Total Project Cost
$
1,947,000
Low Estimate
$
1,362,900
-30%
High Estimate
$
2,920,500
+50%
61

Table 4.5
Capital cost opinion for 2 MGD Cr(VI) treatment using WBA resin
DESCRIPTION
CITY
UNIT MEAS UNIT COST TOTAL COST
COMMENTS
Equipment
Acid Feed System
1
LS
$
70,000
$
70,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Cartridge Filter
2
EA
$
5,000
$
10,000
1 duty/1 stand-by
Ion Exchange Equipment
2
EA
$
220,000
$
440,000
12-ft diameter Lead and Lag Vessels
IX Backwash Pumps
2
EA
$
7,500
$
15,000
1 duty/lstand-by
Backwash Waste Tank
1
EA
$
37,000
$
37,000
12-ft diameter FRP Tank; 14,000 gallon
Discharge Pumps
2
EA
$
5,000
$
10,000
1 duty/lstand-by
Caustic Feed System
1
LS
$
50,000
$
50,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Chlorine Feed System
1
LS
$
50,000
$
50,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Flow Elements or Flow Meter
3
EA
$
3,000
$
9,000
Flow measurements (with display)
Static Mixer
1
EA
$
1,800
$
1,800
6-inch diameter mixer
WBA Resin
1,400
CF
$
200
$
280,000
Initial Fill
Total Equipment Cost
$
973,000
Installation
30%
$
291,900
Electrical and Instrumentation & Coi
20%
$
194,600
General Site Civil
15%
$
145,950
Valves, Piping and Appurtenance
15%
$
145,950
Concrete
53
CY
$
600
$
31,800
Equipment pads and other site
pavement
Total Direct Cost
$
1,784,000
Contractor's Overhead and Profit
15%
$
267,600
Contingency
30%
$
80,280
Total Construction Capital Cost
$
2,132,000
Planning, Engineering, Legal and Adi
11%
$
234,520
Construction Admin
9%
$
191,880
Total Project Cost
$
2,559,000
Low Estimate
$
1,791,300
-30%
High Estimate
$
3,838,500
+50%
62

The O&M cost opinions for hexavalent chromium treatment using WBA resin for 0.5
MGD, 1 MGD and 2 MGD capacities are summarized in Table 4.6. The O&M cost opinions
include the costs for chemicals, power, labor, resin replacement and other miscellaneous items.
The assumptions used for developing the O&M cost opinions are summarized in the footnotes.
The WBA resin life of 250,000 bed volumes is based on an influent hexavalent chromium
concentration of 30 µg/L, and effluent concentration of less than 10 µg/L, (Blute et al. 2013;
Chowdhury et al. 2016). The actual WBA resin life has to be established based on site -specific
pilot testing.
Table 4.6
O&M cost o>ainion for Cr(VI) treatment using WBA resin
Capacity
Item
0.5 MGD
1 MGD
2 MGD
Power 1 $
13,000
$ 15,000
$
17,000
Chemicals z $
34,000
$ 67,000
$
134,000
Resin Replacement 3 $
29,000
$ 63,000
$
139,000
Spent Resin & Wastewater Disposal $
56,000
$ 126,000
$
249,000
Labor $
100,000
$ 100,000
$
100,000
Maintenance & Spare Parts4 $
5,060
$ 7,360
$
9,730
Analytics 5 $
50,000
$ 50,000
$
50,000
Total Annual O&M $
288,000
$ 429,000
$
699,000
Low Estimate $
201,600
$ 300,300
$
489,300
High Estimate $
432,000
$ 643,500
$
1,048,500
Notes:
1. Unit cost of electricity was assumed to $0.12 per kiloWatt hour (kWh).
2. Chemical costs include acid, base and chlorine costs.
3. Resin replacement costs are based assumed resin life
of 250,000 bed volumes prior to breakthrough.
4. Maintenance costs were estimated to be 1% of total installed
equipment costs.
5. Analytical costs include field and laboratory analysis for compliance and process monitoring.
The cost opinions developed with this methodology are considered to fall within the range
of Class 5 estimates as defined by the Association for the Advancement of Cost Engineering
(AACE) International. These levels of engineering cost estimating are generally conducted on the
basis of limited preliminary information and without detailed information such as process and
instrumentation diagrams, engineering layouts, and equipment schedules. This level of cost
estimating is appropriate for budgetary planning purposes, assessment of initial viability and
evaluation of alternative plans. Typical accuracy ranges recognized for AACE Class 5 estimates
are -30% to +50%. The cost tables include low and high ranges for each capacity size.
63

Strong Base Anion (SBA) Exchange
Process Description
The SBA process has been studied and applied by water systems for treatment of nitrate,
arsenic and perchlorate. Previous pilot studies and demonstration studies showed removals of
hexavalent chromium to less than 1 µg/L (McGuire et al. 2007). In the SBA process, the
quaternary amine functional group (-N(CH3)3+) is strongly basic and ionized to the point that the
resin is effective at a broad pH range (Clifford 1999). The anion selectivity for SBA resins is as
shown below:
Cr042- > S042- > HAS042- > NO3- > HCO3-> CY > F-> OH -
Presence of competing anions such as sulfate significantly impact the bed volumes to
breakthrough. Also, SBA resins can result in "chromatographic peaking" which can result
breakthrough of less preferred anions at concentrations higher than the influent water
concentrations.
Shown in Figure 4.5, Figure 4.6 and Figure 4.7 are the concept -level process flow diagrams
for SBA treatment. The SBA resin does not require any pH adjustment. The spent SBA resin can
be regenerated onsite or replaced with new resin. For waters with low sulfate concentrations (<
50 mg/L), the resin is often run to exhaustion and replaced with new resin.
Figure 4.5 shows the lead -lag configuration of SBA resin. The lead -lag configuration with
no onsite regeneration is often used by small systems that have waters with low sulfate
concentration (< 50 mg/L). In this configuration, the influent water flows through the lead vessel
and then through the lag vessel. When there is a breakthrough of hexavalent chromium in the lag
vessel, the lead vessel is taken offline, and the resin media in the lead vessel is replaced with new
media. The lead vessel with the new media is moved to the lag position and lag vessel is moved
to the lead position by switching the inter -vessel valves. This lead -lag operation of the SBA resin
vessels results in better usage of the resin.
Figure 4.6 shows lead -lag operation of SBA resin with onsite regeneration. Onsite
regeneration of the resin is generally considered for waters with low -moderate concentrations of
sulfate (1 - 150 mg/L) wherein the bed volumes to breakthrough are short. Regeneration of SBA
resin is accomplished using brine solution. During regeneration, the anions such as chromate and
sulfate on the resin are exchanged with chloride in the regenerate solution. Onsite regeneration
results in spent brine that is collected, analyzed and disposed.
Figure 4.7 shows the parallel operation of multiple SBA resin vessels with onsite
regeneration capabilities. This mode of operation can be applied for low (< 50 mg/L) and moderate
sulfate (50 — 150 mg/L) waters. In parallel operation, the SBA resin vessels are brought online in
a staggered mode. The vessel that has been in operation the longest duration is taken offline for
regeneration when there is a breakthrough of hexavalent chromium. During regeneration, the
remaining vessels that are in normal operation treat the influent water. In this mode of operation,
there could be several vessels in service at any given time.
64

Greun
Notes
1. Spent SRA resin is hauled off site for regeneration or disposal.
2. SBA resin requires initial rinsing to remove preservatives.
3. No pH adjustment is required for SBA resins and low sulfate waters.
4. Red lines denote waste streams.
later
k
Rinse
Waste Tank Hauled Off Site /
Disposed to Sewer
Figure 4.5 SBA resin treatment process flow diagram, single use, series operation for low
sulfate (< 50 mg/L) waters
Groundwater
1
g
a
m
w
da
Cartridge Filter c
r
Brine Brine
Saturator Hoiding Tank
---------------------------------------
Bline Storage and reed System
Finished Water
Static Mixer
product
Rinse/Backwash; Rinse/Backwash Hauled Off -Site/
Waste Tank Disposed to Sewer
Spent Brine3 Brine Hauled Off -Site)
Waste Tank Disposed to Sewer
"95
I- Red lines denote brine regenerant and waste streams.
2. SOA resin requires initial rinsing to remove preservatives-
3. SBA resin is regenerated upon exhaustion. Regeneration frequency is determined by water quality.
Figure 4.6 SBA resin treatment process flow diagram, series operation with onsite
regeneration for low -moderate sulfate (1 — 150 mg/L) waters
65

c
Groundwater
a c
6 Finished Water
LLI
Static Mixer
i
I
m
a
'"
"'
^'
l7isinfeckant
�tY�
y
Cartridge Filter
Q
7
7
a`
Product
a
r
--------------------------------------
�+
C
Rinsea
Rinse Hauled Off -Site/
f
Waste Tank Disposed to Sewer
o ;
Spent Brine'
Brine Hauled Off -Site/
Waste Tank Disposed to Sewer
Brine Brine
Saturator Holding Tank
µarcs
_____________________________________
''
1.
Red lines denote brine regenerant
and waste streams.
Brine Storage and Feed System
2.
SBA resin requires initial rinsing to remove preservatives.
3.
SBA resin is regenerated upon exhaustion. Regeneration frequency
is determined by water quality.
Figure 4.7 SBA resin treatment process flow diagram, parallel operation with onsite
regeneration
Advantages and Disadvantages
The key strengths and weaknesses of the SBA process are summarized in Table 4.7.
Table 4.7
Strengths and weaknesses of SBA process
Strengths Weaknesses
SBA resins can operate at a broad pH range
and therefore require no pH suppression or
adjustment.
SBA resins are simple to use for low sulfate
(< 50 mg/L) waters (if there is no onsite
regeneration).
SBA resin treatment requires fewer chemicals
(brine is needed if onsite regeneration is
involved).
SBA resin can simultaneously remove other
contaminants such as arsenic and nitrate.
SBA resin capacity is generally short
compared to WBA resin capacity.
Presence of sulfate impacts chromium
breakthrough time and replacement/
regeneration frequency.
SBA resin process can be fairly complex if
onsite regeneration is involved.
Chromatographic peaking can result in
elevated levels of regulated anions in treated
water. Nitrate/arsenic chromatographic
peaking must be accounted for where
applicable.
66

Key Design Criteria
The key design criteria for SBA treatment for the various modes of configuration and
operation are summarized in Table 4.8, Table 4.9 and Table 4.10.
Table 4.8
Design criteria for SBA resin treatment using single -pass series operation for low sulfate
(< 50 mg/L) waters
Criteria Units Assumptions and Typical Values
System Configuration --
Hydraulic Loading Rate gpm / sf
Minimum Empty Bed
minutes
Contact Time
Lead — Lag Vessels, Series Operation
6-15
3
Minimum Resin Bed Depth ft 3-4
Chemical Addition __ No pH adjustment is required for SBA resin.
Treated water is disinfected using chlorine.
Rinse Considerations __ SBA resin requires rinsing when the media is
initially installed into the pressure vessels.
Rinse Duration minutes 10 — 20
Note: gpm/sf — gallons per minute per square foot; ft — feet
Table 4.9
Design criteria for SBA resin treatment using series operation with onsite regeneration for
low -moderate sulfate (1-150 mg/L) waters
Criteria Units Assumptions and Typical Values
System Configuration -- Lead — Lag Vessels, Series Operation
Hydraulic Loading Rate gpm / sf 6 — 15
Minimum Empty Bed
minutes 3
Contact Time
Minimum Resin Bed Depth ft 3-4
Chemical Addition __ No pH adjustment is required for SBA resin.
Treated water is disinfected using chlorine.
Rinse Considerations __ SBA resin requires rinsing when the media is
initially installed into the pressure vessels.
(continued)
67

Table 4.9 (Continued)
Criteria
Units
Assumptions and Typical Values
Rinse Duration
minutes
10 — 20
In this alternative, spent resin is regenerated
Resin Regeneration
onsite using 10-12% strength sodium
chloride/brine solution.
Table 4.10
Design criteria for SBA resin
treatment using parallel operation with onsite regeneration
Criteria
Units
Assumptions and Typical Values
System Configuration
--
Multiple Vessels, Parallel Operation
Hydraulic Loading Rate
gpm / sf
6 — 15
Minimum Empty Bed
3
Contact Time
minutes
Minimum Resin Bed Depth
ft
3-4
Chemical Addition
__
No pH adjustment is required for SBA resin.
Treated water is disinfected using chlorine.
Rinse Considerations
__
SBA resin requires rinsing when the media is
initially installed into the pressure vessels.
minutes
Rinse Duration
10 — 20
In this alternative, spent resin is regenerated
Resin Regeneration
onsite using 10-12% strength sodium
chloridelbrine solution.
Residuals Disposal Considerations
The SBA resin requires initial rinsing to remove preservatives and fines and intermittent
backwashing to control head loss. The spent rinse water and backwash wastewater are collected
in a waste tank, analyzed and disposed to sanitary sewer (if available near the well site) or
transported to a POTW facility for ultimate disposal.
Systems that employ onsite regeneration of SBA resin will generate spent brine that can
contain elevated concentrations of hexavalent chromium and co-occurring anions (arsenic, nitrate,
sulfate). The spent brine has to be characterized prior to disposal. If the concentrations of
hexavalent chromium or the anions exceed the thresholds for toxicity, the spent brine can be
classified as a hazardous waste. Spent brine can be collected, treated onsite, characterized and
disposed to sewer if it meets the local disposal limits. Spent brine can also be collected,
68

characterized and hauled off -site for disposal. Costs for spent brine disposal could vary
significantly based on the water quality, site location, local limits and other factors.
Conceptual Treatment Footprints
The conceptual footprints for hexavalent chromium treatment using SBA resin for 0.5
million gallons per day (MGD), 1 MGD and 2 MGD capacities and various configurations are
shown in Figure 4.8 through Figure 4.16. Shown in Figure 4.8, Figure 4.9 and Figure 4.10 are the
concept -level footprints for SBA resin treatment using single use, series configuration for low
sulfate (< 50 mg/L) waters. Figure 4.11, Figure 4.12 and Figure 4.13 respectively show the
conceptual footprints for SBA resin treatment with onsite regeneration for 0.5 MGD, 1 MGD and
2 MGD. Shown in Figure 4.14, Figure 4.15 and Figure 4.16 are the concept -level footprints for
SBA resin treatment using parallel configuration of vessels. The footprint and space requirements
may vary based on site constraints, well pumping rates and specific equipment requirements. The
conceptual footprints include secondary containment for all chemical and waste storage tanks. The
SBA resin vessels may need to be enclosed depending on the local climate conditions. The
treatment footprints do not include the space for well(s), ground storage tank(s), a pump station,
or storm water detention.
69

---------------------
Electrical
8ft & 10ft
Lead Vessel Controls
:--------------------' 10 ft
---------------------
12 ft
8 ft
ft
40 ft Lag Vessel (i6
lorne
Tank
-- ---- Access
Note: Secondary Containment for all tanks are shown in dotted lines
Figure 4.8 Conceptual footprint for 0.5 MGD capacity Cr(VI) treatment using SBA resin,
single use, series operation for low sulfate (< 50 mg/L) waters
70

40
12
Access
Note: Secondary Containment for all tanks are shown in dotted lines
Electrical
& 10 ft
Controls
10
----------------
6 ft
Chlorine
Tank
Figure 4.9 Conceptual footprint for 1 MGD capacity Cr(VI) treatment using SBA resin,
single use, series operation for low sulfate (< 50 mg/L) waters
71

40 ft-------------- - ------------
12 ft
Lag Vessel
):
-----------------------------
12
Access
Note: Secondary Containment for all tanks are shown in dotted lines
Electrical
& 10 ft
Controls
10
-----------------
6ft
Chlorine
Tank
----------------
Figure 4.10 Conceptual footprint for 2 MGD capacity Cr(VI) treatment using SBA resin,
single use, series operation for low sulfate (< 50 mg/L) waters
72

\
8 ft�
Lead Vessel /
--------------------
---------------------
k8 ft
Lag Vessel
12 ft
Electrical
& 10 ft
Controls
10 ft
-----------------
6 ft
Chlorine
Tank
- ----
Access
'--------------
50
ft
--------------------------
10 ft
10 ft
Brine Holding ,
Brine Waste
Tank
Tank
-----------------------
-------------------------
---------------
---------------------
6 ft
ft
(Waste
Brine
inse
aturator
Tank/
50 ft—
I
Note: Seconaary Containment Tor aii tanKs are shown in aottea nnes
Figure 4.11 Conceptual footprint for 0.5 MGD capacity Cr(VI) treatment using SBA resin,
series operation with onsite regeneration for low -moderate sulfate (1 — 150 mg/L) waters
73

Electrical
& 10 ft
10 ft Controls
Lead Vessel
10 ft
------------------------
-------------------------• 12 ft
6 ft
Chionne
CLag
ft Tank
essel
----------------------- Access
60 ft
10 ft
Brine Waste
10 ft)
t Tank
Brine Holding
Tank
---------------
--------------------------
10 ft
Rinse Waste
10 ft Tank
Brine ;
Saturator `
55 ft
Note: Secondary Containment for all tanks are shown in dotted lines
Figure 4.12 Conceptual footprint for 1 MGD capacity Cr(VI) treatment using SBA resin,
series operation with onsite regeneration for low -moderate sulfate (1 — 150 mg/L) waters
74

----------------------------
Electrical
& 10 ft
12 ft Controls
10 ft
Lead Vessel
----------------------------=
------------------
-- --=-----------
�' 6 ft
12 ft Chlorine
Tank
12 ft
Lag Vessel
-----------------------------
Access
65 ft
-----------------------------
12 ft
Brine Waste
12 ft Tank
Brine Holding
--------------------
Tank
---------------------------- ;-------------------------------------------------------
12 ft-
ft
loft Rinse Waste
Brine Tank
Saturator -------------------------------
Note: Secondary Containment for all tanks are shown in dotted lines
Figure 4.13 Conceptual footprint for 2 MGD capacity Cr(VI) treatment using SBA resin,
series operation with onsite regeneration for low -moderate sulfate (1 — 150 mg/L) waters
75

------------
4 ft
Vessel Electrical
& 10 ft
Controls
------------
10 ft
4 ft 12 ft
Vessel 2
Oft
Chiorme ;
Access Tank
4 ft
Vessel3 ;
45 ft
- -- -- -- -----------------
----------------
�� 6 ft
Brine Waste
6ftTank
Brine Holding;' ;
Tank----------------
---------------------
-----------------
r 8 ft
ft Rinse
Brine ' v Waste Tank
aturato
- -- - -- -
--------------------
45 ft
Note: Secondary Containment for all tanks are shown in dotted lines
Figure 4.14 Conceptual footprint for 0.5 MGD capacity Cr(VI) treatment using SBA resin,
parallel operation with onsite regeneration
76

55 ft
6 ft
Vessel 1
---------------
-----------------
6ft
Vessel 2
12ft
Electrical
& loft
Controls
10 ft
----------------
6 ft
----
Chlorine
Tank
-----------------
Access
; --------------------
6 ft
Vessel 3
8 ft
=---------------
Brine
--------------------
Waste Tan
--------------------
CoIdTanI
-------------------------
10 ft
:r
-----------------
Rinse Waste
6 ft
Tank
Brine
- -
aturato
soft
Note: Secondary Containment for all tanks are shown in dotted lines
Figure 4.15 Conceptual footprint for 1 MGD capacity Cr(VI) treatment using SBA resin,
parallel operation with onsite regeneration
77

60
---------------------
8 ft Electrical
& 10 ft
Vessel 1 Controls
-------------------' 10 ft
8 ft ----------------
12 ft
Vessel 2 6 ft
Chlorine
--------------------'
Tank
---------------------
------------------------
8 ft Access
ft Vessel 3
--------------------
10 t
-------------------------- Brine Waste
Tank
------------------------
10 ft
Brine Holding ----------------------------
Tank
------------------------
------------------------ ;
12 ft
Resin Waste
10 ft Tank
Brine '--------------------
Saturator
55 ft
Note: Secondary Containment for all tanks are shown in dotted lines
Figure 4.16 Conceptual footprint for 2 MGD capacity Cr(VI) treatment using SBA resin,
parallel operation with onsite regeneration
78

Budgetary -Level Cost Opinions
The budget -level capital cost opinions for 0.5 MGD, 1 MGD and 2 MGD hexavalent
chromium treatment using the SBA resin for various configurations and modes of operation are
summarized in Table 4.11 through Table 4.19. The capital cost opinions were developed by
obtaining vendor quotations for all major equipment, estimating the amount of concrete needed
for slabs and facilities and applying appropriate factors for installation, electrical, instrumentation
and controls, general site civil, valving / piping and appurtenances, and contractor's overhead and
profit.
Table 4.11
Capital cost opinion for 0.5 MGD Cr(VI) treatment using SBA resin, single use, series
operation for low sulfate (< 50mg/L) waters
DESCRIPTION
CITY
UNIT MEAS. UNIT COST TOTAL COST
COMMENTS
Equipment
Cartridge Filter
2
EA
$
5,000
$
10,000
1 duty/lstand-by
Ion Exchange Equipment
2
EA
$
150,000
$
300,000
8-ft diameter Vessels
Rinse Waste Tank
1
EA
$
30,000
$
30,000
10-ft diameter Rinse waste Tank; 5,000
gallon
Discharge Pumps
2
EA
$
5,000
$
10,000
1 duty/lstand-by
Chlorine Feed Systems
1
LS
$
30,000
$
30,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Flow Elements / Meters
3
EA
$
3,000
$
9,000
Flow measurements (with display)
Static Mixer
1
EA
$
1,800
$
1,800
6-inch diameter mixer
SBA Resin
300
CF
$
160
$
48,000
Initial Fill
Total Equipment Cost
$
439,000
Installation
30%
$
131,700
Electrical and Instrumentation & Cor
20%
$
87,800
General Site Civil
15%
$
65,850
Valves, Piping and Appurtenance
15%
$
65,850
Concrete
58
CY
$
600
$
34,800
Equipment pads and other site pavemen
Total Direct Cost
$
825,000
Contractor's Overhead and Profit
15%
$
123,750
Contingency
30%
$
37,125
Total Construction Capital Cost
$
986,000
Planning, Engineering, Legal and Adn 11%
$
108,460
Construction Admin
9%
$
88,740
Total Project Cost
$ 1,184,000
Low Estimate
$
828,800
-30%
High Estimate
$ 1,776,000
+50%
79

Table 4.12
Capital cost opinion for 1 MGD Cr(VI) treatment using SBA resin, single use, series
operation for low sulfate (< 50 mg/L) waters
DESCRIPTION
CITY
UNIT MEAS UNIT COST TOTAL COST
COMMENTS
Equipment
Cartridge Filter
2
EA
$
5,000
$ 10,000
1 duty/lstand-by
Ion Exchange Equipment
2
EA
$180,000
$ 360,000
10-ft diameter Vessels
Rinse Waste Tank
1
EA
$
30,000
$ 30,000
10-ft diameter Rinse waste Tank; 8,000
gallon
Dlscharge Pumps
2
EA
$
5,000
$ 10,000
1 duty/lstand-by
Chlorine Feed Systems
1
LS
$
40,000
$ 40,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Flow Elements / Meters
3
EA
$
3,000
$ 9,000
Flow measurements (with display)
Static Mixer
1
EA
$
2,400
$ 2,400
9-inch diameter mixer
SBA Resin
600
CIF
$
160
$ 96,000
Initial Fill
Total Equipment Cost
$ 558,000
Installation
30%
$ 167,400
Electrical and Instrumentation & Coi 20%
$ 111,600
General Site Civil
15%
$ 83,700
Valves, Piping and Appurtenance
15%
$ 83,700
Concrete
63
CY
$
600
$ 37,800
Equipment pads and other site pavemei
Total Direct Cost
$1,043,000
Contractor's Overhead and Profit
15%
$ 156,450
Contingency
30%
$ 46,935
Total Construction Capital Cost
$1,247,000
Planning, Engineering, Legal and Adr 11%
$ 137,170
Construction Admin
9%
$ 112,230
Total Project Cost
$1,497,000
Low Estimate
$1,047,900
-30%
High Estimate
$ 2,245,500
+50%
80

Table 4.13
Capital cost opinion for 2 MGD Cr(VI) treatment using SBA resin, single use, series
operation for low sulfate (< 50 mg/L) waters
DESCRIPTION
CITY
UNIT MEAS. UNIT COST
TOTAL COST
COMMENTS
Equipment
Cartridge Filter
2
EA
$
5,000
$ 10,000
1 duty/lstand-by
Ion Exchange Equipment
2
EA
$
210,000
$ 420,000
12-ft diameter Vessels
Rinse Waste Tank
1
EA
$
37,000
$ 37,000
12-ft diameter Rinse waste Tank; 15,000
gallon
Discharge Pumps
2
EA
$
5,000
$ 10,000
1 duty/lstand-by
Chlorine Feed Systems
1
LS
$
50,000
$ 50,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Flow Elements / Meters
3
EA
$
3,000
$ 9,000
Flow measurements (with display)
Static Mixer
1
EA
$
3,500
$ 3,500
12-inch diameter mixer
SBA Resin
1200
CIF
$
160
$ 192,000
Initial Fill
Total Equipment Cost
$ 732,000
Installation
30%
$ 219,600
Electrical and Instrumentation & Coi
20%
$ 146,400
General Site Civil
15%
$ 109,800
Valves, Piping and Appurtenance
15%
$ 109,800
Concrete
69
CY
$
600
$ 41,400
Equipment pads and other site pavement
Total Direct Cost
$ 1,359,000
Contractor's Overhead and Profit
15%
$ 203,850
Contingency
30%
$ 61,155
Total Construction Capital Cost
$ 1,625,000
Planning, Engineering, Legal and Adr 11%
$ 178,750
Construction Admin
9%
$ 146,250
Total Project Cost
$ 1,950,000
Low Estimate
$ 1,365,000
-30%
High Estimate
$ 2,925,000
+50%
81

Table 4.14
Capital cost opinion for 0.5 MGD Cr(VI) treatment using SBA resin, series operation with
onsite regeneration for low -moderate sulfate (1 - 150 mg/L) waters
DESCRIPTION
CITY
UNIT MEAS UNIT COST TOTAL COST
COMMENTS
Equipment
Brine Feed System
1
LS
$
50,000
$
50,000
Brine Tank and Saturator
Cartridge Filter
2
EA
$
5,000
$
10,000
1 duty/lstand-by
Ion Exchange Equipment
2
EA
$150,000
$
300,000
8-ft diameter Vessels
IX Backwash Pumps
2
EA
$
7,500
$
15,000
1 duty/lstand-by
Rinse Waste Tank
1
EA
$
22,000
$
22,000
8-ft diameter Rinse waste Tank; 4,500gallon
Discharge Pumps
2
EA
$
5,000
$
10,000
1 duty/lstand-by
Brine Waste Tank
1
EA
$
22,000
$
22,000
10-ft diameter Rinse waste Tank; 5,700
gallon
Chlorine Feed Systems
1
LS
$
30,000
$
30,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Flow Elements / Meters
3
EA
$
3,000
$
9,000
Flow measurements (with display)
Static Mixer
1
EA
$
1,800
$
1,800
6-inch diameter mixer
SBA Resin
300
CIF
$
160
$
48,000
Initial Fill
Total Equipment Cost
$
518,000
Installation
30%
$
155,400
Electrical and Instrumentation & Co
20%
$
103,600
General Site Civil
15%
$
77,700
Valves, Piping and Appurtenance
15%
$
77,700
Concrete
72
CY
$
600
$
43,200
Equipment pads and other site pavement
Total Direct Cost
$
976,000
Contractor's Overhead and Profit
15%
$
146,400
Contingency
30%
$
43,920
Total Construction Capital Cost
$1,167,000
Planning, Engineering, Legal and Ad
11%
$
128,370
Construction Admin
9%
$
105,030
Total Project Cost
$1,401,000
Low Estimate
$
980,700
-30%
High Estimate
$ 2,101,500
+50%
82

Table 4.15
Capital cost opinion for 1 MGD Cr(VI) treatment using SBA resin, series operation with
onsite regeneration for low -moderate sulfate (1 - 150 mg/L) waters
DESCRIPTION
CITY
UNIT MEAS UNIT COST TOTAL COST
COMMENTS
Equipment
Brine Feed System
1
LS
$
50,000
$ 50,000
Brine Tank and Saturator
Cartridge Filter
2
EA
$
5,000
$ 10,000
1 duty/1 stand-by
Ion Exchange Equipment
2
EA
$180,000
$ 360,000
10-ft diameter Vessels
IX Backwash Pumps
2
EA
$
7,500
$ 15,000
1 duty/1 stand-by
Rinse Waste Tank
1
EA
$
30,000
$ 30,000
10-ft diameter Rinse waste Tank; 8,000gallon
Dlscharge Pumps
2
EA
$
5,000
$ 10,000
1 duty/1 stand-by
Brine Waste Tank
1
EA
$
30,000
$ 30,000
10-ft diameter Rinse waste Tank; 8,900
gallon
Chlorine Feed Systems
1
LS
$
40,000
$ 40,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Flow Elements / Meters
3
EA
$
3,000
$ 9,000
Flow measurements (with display)
Static Mixer
1
EA
$
2,400
$ 2,400
9-inch diameter mixer
SBA Resin
550
CF
$
160
$ 88,000
Initial Fill
Total Equipment Cost
$ 645,000
Installation
30%
$ 193,500
Electrical and Instrumentation & Cot 20%
$ 129,000
General Site Civil
15%
$ 96,750
Valves, Piping and Appurtenance
15%
$ 96,750
Concrete
100
CY
$
600
$ 60,000
Equipment pads and other site pavemer
Total Direct Cost
$1,221,000
Contractor's Overhead and Profit
15%
$ 183,150
Contingency
30%
$ 54,945
Total Construction Capital Cost
$1,460,000
Planning, Engineering, Legal and Adr 11%
$ 160,600
Construction Admin
9%
$ 131,400
Total Project Cost
$1,752,000
Low Estimate
$1,226,400
-30%
High Estimate
$2,628,000
+50%
83

Table 4.16
Capital cost opinion for 2 MGD Cr(VI) treatment using SBA resin, series operation with
onsite regeneration for low -moderate sulfate (1 - 150 mg/L) waters
DESCRIPTION
CITY
UNIT MEAS UNIT COST TOTAL COST
COMMENTS
Equipment
Brine Feed System
1
LS
$
50,000
$ 50,000
Brine Tank and Saturator
Cartridge Filter
2
EA
$
5,000
$ 10,000
1 duty/1 stand-by
Ion Exchange Equipment
2
EA
$
210,000
$ 420,000
12-ft diameter Vessels
IX Backwash Pumps
2
EA
$
7,500
$ 15,000
1 duty/1 stand-by
Rinse Waste Tank
1
EA
$
37,000
$ 37,000
12-ft diameter Rinse waste Tank; 15,000
gallon
Discharge Pumps
2
EA
$
5,000
$ 10,000
1 duty/1 stand-by
Brine Waste Tank
1
EA
$
37,000
$ 37,000
12-ft diameter Rinse waste Tank; 15,000gallon
Chlorine Feed Systems
1
LS
$
50,000
$ 50,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Flow Elements / Meters
3
EA
$
3,000
$ 9,000
Flow measurements (with display)
Static Mixer
1
EA
$
3,500
$ 3,500
12-inch diameter mixer
SBA Resin
1400
CF
$
160
$ 224,000
Initial Fill
Total Equipment Cost
$ 866,000
Installation
30%
$ 259,800
Electrical and Instrumentation & Co
20%
$ 173,200
General Site Civil
15%
$ 129,900
Valves, Piping and Appurtenance
15%
$ 129,900
Concrete
116
CY
$
600
$ 69,600
Equipment pads and other site pavement
Total Direct Cost
$ 1,629,000
Contractor's Overhead and Profit
15%
$ 244,350
Contingency
30%
$ 73,305
Total Construction Capital Cost
$ 1,947,000
Planning, Engineering, Legal and Ad
11%
$ 214,170
Construction Admin
9%
$ 175,230
Total Project Cost
$ 2,337,000
Low Estimate
$ 1,635,900
-30%
High Estimate
$ 3,505,500
+50%
84

Table 4.17
Capital cost opinion for 0.5 MGD Cr(VI) treatment using SBA resin, parallel operation
with onsite regeneration
DESCRIPTION
CITY 1NIT MEAS UNIT COST
TOTAL COST
COMMENTS
Equipment
Brine Feed System
1
LS
$
50,000
$
50,000
Brine Tank and Saturator
Cartridge Filter
2
EA
$
5,000
$
10,000
1 duty/ 1stand-by
Ion Exchange Equipment
3
EA
$
100,000
$
300,000
4-ft diameter Vessels
IX Backwash Pumps
2
EA
$
7,500
$
15,000
1 duty/1 stand-by
Rinse Waste Tank
1
EA
$
20,000
$
20,000
8-ft diameter Rinse waste Tank; 4,000
gallon
Discharge Pumps
2
EA
$
5,000
$
10,000
1 duty/1 stand-by
Brine Waste Tank
1
EA
$
16,000
$
16,000
6-ft diameter Brine Waste Tank; 1,500
gallon
Chlorine Feed Systems
1
LS
$
30,000
$
30,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Flow Elements / Meters
4
EA
$
3,000
$
12,000
Flow measurements (with display)
Static Mixer
1
EA
$
1,800
$
1,800
6-inch diameter mixer
SBA Resin
200
CF
$
160
$
32,000
Initial Fill
Total Equipment Cost
$
497,000
Installation
30%
$
149,100
Electrical and Instrumentation & Cor 20%
$
99,400
General Site Civil
15%
$
74,550
Valves, Piping and Appurtenance
15%
$
74,550
Concrete
52
CY
$
600
$
31,200
Equipment pads and other site pavement
Total Direct Cost
$
926,000
Contractor's Overhead and Profit
15%
$
138,900
Contingency
30%
$
41,670
Total Construction Capital Cost
$ 1,107,000
Planning, Engineering, Legal and Adn 11%
$
121,770
Construction Admin
9%
$
99,630
Total Project Cost
$ 1,329,000
Low Estimate
$
930,300
-30%
High Estimate
$ 1,993,500
+50%
85

Table 4.18
Capital cost opinion for 1 MGD Cr(VI) treatment using SBA resin, parallel operation with
onsite regeneration
DESCRIPTION
CITY
UNIT MEAS UNIT COST TOTAL COST
COMMENTS
Equipment
Brine Feed System
1
LS
$
50,000
$ 50,000
Brine Tank and Saturator
Cartridge Filter
2
EA
$
5,000
$ 10,000
1 duty/1 stand-by
Ion Exchange Equipment
3
EA
$125,000
$ 375,000
6-ft diameter Vessels
IX Backwash Pumps
2
EA
$
7500
$ 15,000
1 duty/1 stand-by
Rinse Waste Tank
1
EA
$
24,000
$ 24,000
10-ft diameter Rinse waste Tank; 8,000
gallons
Discharge Pumps
2
EA
$
5,000
$ 10,000
1 duty/1 stand-by
Brine Waste Tank
1
EA
$
22,000
$ 22,000
8-ft diameter Brine Waste Tank; 3,000
gallons
Chlorine Feed Systems
1
EA
$
40,000
$ 40,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Flow Elements / Meters
4
EA
$
3,000
$ 12,000
Flow measurements (with display)
Static Mixer
1
EA
$
2,400
$ 2,400
9-inch diameter mixer
SBA Resin
300
CF
$
160
$ 48,000
Initial Fill
Total Equipment Cost
$ 609,000
Installation
30%
$ 182,700
Electrical and Instrumentation & Co
20%
$ 121,800
General Site Civil
15%
$ 91,350
Valves, Piping and Appurtenance
15%
$ 91,350
Concrete
74
CY
$
600
$ 44,400
Equipment pads and other site pavemei
Total Direct Cost
$1,141,000
Contractor's Overhead and Profit
15%
$ 171,150
Contingency
30%
$ 51,345
Total Construction Capital Cost
$1,364,000
Planning, Engineering, Legal and Ad
11%
$ 150,040
Construction Admin
9%
$ 122,760
Total Project Cost
$1,637,000
Low Estimate
$1,145,900
-30%
High Estimate
$ 2,455,500
+50%
86

Table 4.19
Capital cost opinion for 2 MGD Cr(VI) treatment using SBA resin, parallel operation with
onsite regeneration
DESCRIPTION
CITY
UNIT MEAS. UNIT COST
TOTAL COST
COMMENTS
Equipment
Brine Feed System
1
LS
$
50,000
$ 50,000
Brine Tank and Saturator
Cartridge Filter
2
EA
$
5,000
$ 10,000
1 duty/1 stand-by
Ion Exchange Equipment
3
EA
$
150,000
$ 450,000
8-ft diameter Vessels
IX Backwash Pumps
2
EA
$
7,500
$ 15,000
1 duty/1 stand-by
Rinse Waste Tank
1
EA
$
30,000
$ 30,0002-ft
1
diameter Rinse waste Tank; 15,000
gallons
Discharge Pumps
2
EA
$
5,000
$ 10,000
1 duty/1 stand-by
Brine Waste Tank
1
EA
$
24,000
$ 24,000
10-ft diameter Brine Waste Tank; 5,500
gallons
Chlorine Feed Systems
1
EA
$
50,000
$ 50,000
2 chemical feed pumps, 3,000-gallon
double walled storage tank
Flow Elements / Meters
4
EA
$
3,000
$ 12,000
Flow measurements (with display)
Static Mixer
1
EA
$
3,500
$ 3,500
12-inch diameter mixer
SBA Resin
600
CIF
$
160
$ 96,000
Initial Fill
Total Equipment Cost
$ 751,000
Installation
30%
$ 225,300
Electrical and Instrumentation & Coi 20%
$ 150,200
General Site Civil
15%
$ 112,650
Valves, Piping and Appurtenance
15%
$ 112,650
Concrete
94
CY
$
600
$ 56,400
Equipment pads and other site pavement
Total Direct Cost
$ 1,409,000
Contractor's Overhead and Profit
15%
$ 211,350
Contingency
30%
$ 63,405
Total Construction Capital Cost
$ 1,684,000
Planning, Engineering, Legal and Adi 11%
$ 185,240
Construction Admin
9%
$ 151,560
Total Project Cost
$ 2,021,000
Low Estimate
$ 1,414,700
-30%
High Estimate
$ 3,031,500
+50%
87

The O&M cost opinions for hexavalent chromium treatment using SBA resin for 0.5 MGD,
1 MGD and 2 MGD capacities are summarized in Table 4.20 through Table 4.22. The O&M cost
opinions include the costs for chemicals, power, labor, resin replacement and other miscellaneous
items. The assumptions used for developing the O&M cost opinions are summarized in the
footnotes.
The SBA resin life of 40,000 bed volumes for single use, series operation for low sulfate
waters (< 50 mg/L) is based on an influent hexavalent chromium concentration of approximately
20 µg/L and effluent concentration of less than 10 µg/L (Seidel et al. 2014; Chowdhury et al.
2016). The actual SBA resin life has to be established based on site -specific pilot testing.
Table 4.20
O&M cost opinion for Cr(VI) treatment using SBA resin, single use, series operation for
low sulfate (< 50 mg/L) waters
Capacity
Item
0.5 MGD
1 MGD
2 MGD
Power'
$ 12,000
$
13,000
$
13,000
Chemicals Z
$ 9,000
$
18,000
$
36,000
Resin Replacement
$ 97,000
$
196,000
$
391,000
Spent Resin & Wastewater Disposal
$ 187,000
$
374,000
$
748,000
Labor
$ 100,000
$
100,000
$
100,000
Maintenance &Spare Parts4
$ 4,390
$
5,580
$
7,320
Analytics s
$ 50,000
$
50,000
$
50,000
Total Annual O&M 6
$ 460,000
$
757,000
$
1,346,000
Low Estimate
$ 322,000
$
529,900
$
942,200
High Estimate
$ 690,000
$
1,135,500
$
2,019,000
Notes:
1. Unit cost of electricity was assumed to $0.12 per kiloWatt hour (kWh).
2. Chemical costs include chlorine costs.
3. Resin replacement costs are based assumed resin life of 40,000 bed volumes priorto irreversible
fouling.
4. Maintenance costs were estimated to be
1% of total installed equipment costs.
5. Analytical costs include field and laboratory analysis for compliance and process monitoring.
6. Costs are based on low sulfate concentration (i.e., <50 mg/L)
88

In Table 4.21, the SBA resin life of 10,000 bed volumes for series operation for low -
moderate sulfate waters (1-150 mg/L) is based on an influent hexavalent chromium concentration
of approximately 20 µg/L and effluent concentration of less than 10 µg/L (Seidel et al. 2014;
Chowdhury et al. 2016). The SBA resin performance declines with multiple loading -regeneration
cycles and this is attributed to irreversible fouling of the resin (Seidel et al. 2014). For O&M cost
estimates, the resin is assumed to last for approximately 20 regenerations before it has to be
replaced. The actual SBA resin bed volumes and life has to be established based on site -specific
pilot testing of multiple regenerations.
Table 4.21
O&M cost opinion for Cr(VI) treatment using SBA resin, series operation with onsite
regeneration for low -moderate sulfate (1 - 150 mg/L) waters
Capacity
Item 0.5 MGD
1 MGD
2 MGD
Power' $ 55,000
$ 98,000
$
141,000
Chemicals z $ 29,000
$ 68,000
$
156,000
Resin Replacement $ 33,000
$ 51,000
$
91,000
Spent Resin & Wastewater Disposal 4 $ 122,000
$ 224,000
$
433,000
Labor $ 100,000
$ 100,000
$
100,000
Maintenance &SpareParts 5 $ 5,180
$ 6,450
$
8,660
Analytics a $ 50,000
$ 50,000
$
50,000
Total Annual O&M 7 $ 395,000
$ 598,000
$
980,000
Low Estimate $ 276,500
$ 418,600
$
686,000
High Estimate $ 592,500
$ 897,000
$
1,470,000
Notes:
1. Unit cost of electricity was assumed to $0.12 per kiloWatt hour (kWh).
2. Chemical costs include chlorine costs.
3. Resin replacement costs are based assumed resin life of 200,000 bed volumes prior to irreversible fouling.
4. Resin backwash costs are based assumed resin life of 10,000 bed volumes prior
to breakthrough.
5. Maintenance costs were estimated to be 1% of total installed equipment
costs.
6. Analytical costs include field and laboratory analysis for compliance and
process monitoring.
7. Costs are based on moderate sulfate concentration (i.e., 50- 150 mg/L)
89

Table 4.22
O&M cost opinion for Cr(VI) treatment using SBA resin, parallel operation with onsite
regeneration
Capacity
Item 0.5 MGD
1 MGD
2 MGD
Power' $ 55,000
$ 98,000
$
141,000
Chemicals z $ 37,000
$ 68,000
$
146,000
Resin Replacement $ 49,000
$ 109,000
$
194,000
Spent Resin & Wastewater Disposal 4 $ 160,000
$ 335,000
$
618,000
Labor $ 100,000
$ 100,000
$
100,000
Maintenance &SpareParts s $ 4,970
$ 6,090
$
7,510
Analytics 6 $ 50,000
$ 50,000
$
50,000
Total Annual O&M 7 $ 456,000
$ 767,000
$
1,257,000
Low Estimate $ 319,200
$ 536,900
$
879,900
High Estimate $ 684,000
$ 1,150,500
$
1,885,500
Notes:
1. Unit cost of electricity was assumed to $0.12 per kiloWatt hour (kWh).
2. Chemical costs include chlorine costs.
3. Resin replacement costs are based assumed resin life of 200,000 bed volumes prior to irreversible fouling.
4. Resin backwash costs are based assumed resin life of 10,000 bed volumes prior
to breakthrough.
5. Maintenance costs were estimated to be 1% of total installed equipment
costs.
6. Analytical costs include field and laboratory analysis for compliance and
process monitoring.
7. Costs are based on moderate sulfate concentration (i.e., 50- 150 mg/L)
90

Granular Iron Media (GIM)
Process Description
The GIM process has been studied at bench and pilot -scale level to remove hexavalent
chromium from groundwater (Blute et al. 2015b). The two most common adsorptive media that
have been studied in the past and were evaluated in this study in bench -scale testing include sulfur
modified iron (SMI®) and another iron -based adsorptive media (Cleanit(K-LC). While the exact
removal mechanism for hexavalent chromium by GIM is uncertain, it is assumed to include
reduction, adsorption and filtration. The conceptual process flow diagram for GIM treatment is
shown in Figure 4.17. The GIM process involves pH suppression using acid addition, pressure
vessels or reactors that are filled with GIM, and removal of dissolved iron using oxidation and
filtration. As the water flows through the GIM pressure vessel, it has been shown to pick-up excess
concentrations of dissolved iron, which is oxidized by chlorine addition and removed by iron
removal filters. Post -filtration, the pH of the treated water is adjusted to ambient levels. The spent
filter backwash water is collected and disposed to a sanitary sewer or hauled to an offsite disposal
facility. This is a fairly innovative process and may require additional testing to obtain State
approvals prior to full-scale implementation.
M
Hauled Off -Site/
Waste Disposed to Sewer
F° Reclaim
i..
6
O
m U
Reactor Outlet
� o
_ V
RXT-1 n I ^ Finished
O. O water
c
Reactor InletTil � a
° `c
C .R
c a
Static Miter �
Groundwater FE �on . Hex Chrome Reactors 'c^ 1 +
ilff'' t $ IronRemoual
60 `o Filters
61%c Reactor Inlet
iy t L
� V
- --- O b Q fl
j RXT-2 O
ICc Backwash
supply
6
Reactor Outlet Chksritre
Tank
I Notes
"',ryt' °Tank 1. Red lines denote chemical and waste streams.
Arad Storage and
Feed System
Figure 4.17 Granular Iron Media (GIM) treatment process flow diagram
Advantages and Disadvantages
The key strengths and weaknesses of the GIM process are summarized in Table 4.23.
91

Table 4.23
Strengths and weaknesses of GIM process
Strengths Weaknesses
GIM process is not impacted by the presence
of sulfate unlike SBA and WBA exchange
processes.
GIM process can remove co-occurring
contaminants such as arsenic, nitrate and
uranium. Removal efficiencies have to be
bench and/or pilot tested.
Unlike SBA exchange process, GIM process
does not have chromatographic peaking
issues.
Residuals Disposal Considerations
One of the key disadvantages of GIM process
is the inherent leaching of iron from the
media which requires additional treatment
steps.
GIM process may have potentially larger
footprint compared to WBA and SBA
exchange processes.
GIM is a fairly innovative process with fewer
full-scale applications of the process. Some
states may require additional bench and pilot
testing and approvals of design basis prior to
full-scale implementation.
GIM is a fairly complex process and it
involves chemical feed facilities and residuals
handling facilities.
The GIM process generates liquid and solid residuals. The liquid residual streams include
rinse water from GIM pressure vessels or reactors during installation of the media and the spent
filter backwash water from the iron removal filters. The rinse water and spent filter backwash
water would have to be analyzed and characterized prior to disposal. Disposal options for the
liquid streams include sanitary sewer (if available in proximity to the treatment site) or collection
and hauling to a POTW.
The spent GIM will have elevated concentration of chromium and co-occurring
contaminants such as arsenic, nitrate and uranium. The spent media has to be characterized using
TCLP and California WET. The toxicity limit for chromium in the leachate for TCLP testing is 5
mg/L. The STLC and the TTLC limits under the California Title 22 for hexavalent chromium are
5 mg/L and 500 mg/kg, respectively.
In addition to removing hexavalent chromium, the GIM process can also remove
radionuclides such as uranium. If the groundwater contains radioactive compounds, then the spent
GIM has to be analyzed for additional parameters as defined by the NRC. Presence of
radionuclides (e.g., uranium) on spent GIM can result in its classification as a TENORM. Most
TENORM wastes can be disposed to landfills. However, the spent GIM is classified as a low level
radioactive waste (LLRW) if the total uranium concentration exceeds 500 mg/kg. The waste
disposal costs can be significant if the spent GIM is classified as LLRW as there are only a few
facilities that can handle radioactive wastes. Water systems with uranium in groundwater can
consider limiting the operational life of GIM to avoid exceeding the LLRW threshold for
radioactivity.
92

Reverse Osmosis (RO)
Process Description
The RO membrane treatment has been shown to achieve greater than 90 percent (%)
hexavalent chromium removal in bench -scale studies and by point -of -use treatment systems
(Brandhuber et al. 2004). In addition to hexavalent chromium removal, the RO membranes can
remove >99% of divalent ions and >95% monovalent ions. The conceptual -level process flow
diagram for RO treatment is shown in Figure 4.18. The RO treatment involves pre-treatment using
cartridge filters, acid and/or anti-scalant addition, RO membrane skids, post -treatment pH
stabilization, RO membrane clean -in -place (CIP) system and residuals handling systems.
Approximately 10-15% of the RO feed water ends up as concentrate or reject water which has to
be disposed. The RO membranes would require cleaning every 3-4 months using chemicals such
as chlorine, acid and base. RO product water or permeate will require re -stabilization using caustic
or lime addition to prevent distribution system corrosion issues. Presently, there are no full-scale
applications of RO treatment for hexavalent chromium removal in drinking water.
i
o Chlorine
CIPPurnp Base
C CIPTank
n0 Acid
�
� � d
D C?P
c RO Skid
RO Feed RO Product Finished
Groundwater � FF � j (J a
*S={ I�TRO
I !f I Water
Q
ect)aste
c
4 R
O
Granular Cartridge
Media Filter Filter
{Optional]
��
0 0�
Hauled Off -site/
RO RejecVCIP I)isposed to Sewer
Waste Tank
Notes
1. Red lines denote CIP and brine streams.
Figure 4.18 Reverse Osmosis (RO) system process flow diagram
Advantages and Disadvantages
4.24.
The key strengths and weaknesses of the RO treatment process are summarized in Table
93

Table 4.24
Strengths and weaknesses of RO treatment process
Strengths Weaknesses
RO treatment can achieve multiple treatment
objectives - lower hardness and total
dissolved solids (TDS) and remove co-
occurring contaminants (arsenic, nitrate and
radionuclides).
RO treatment has been demonstrated for other
applications and is well understood.
Multiple vendors are available to supply RO
membranes and skids.
Residuals Disposal Considerations
Approximately 10-15% of the RO feed water
ends up as concentrate or reject stream. RO
reject stream is high in TDS, metals and
chromium. Disposal of the reject stream can
be expensive and problematic for some
remote, non -coastal well locations.
RO treatment is energy intensive and
therefore the operating cost for RO treatment
could be high.
RO treatment results in a higher quantity of
water loss (-10-15% as reject).
RO treatment has not been demonstrated at
full-scale for Cr(VI) treatment.
The RO treatment generates a large volume of concentrate or reject stream which needs to
be disposed. The RO reject stream will contain elevated concentrations of hexavalent chromium,
co-occurring contaminants (arsenic, nitrate), salts (TDS), metals and radionuclides (if present in
raw water). The RO reject stream has to be characterized prior to disposal. At some locations, it
is not feasible to dispose the RO reject stream to sanitary sewer due to strict limitations on TDS
and other constituents in the effluents of the POTWs. The POTWs may not be able to handle the
elevated levels of TDS, hexavalent chromium and other constituents of RO reject. Alternative
disposal of RO reject such as deep well injection for non -coastal locations can be fairly expensive,
if they are even viable.
Reduction Coagulation Filtration (RCF)
Process Description
The RCF process has been extensively studied and demonstrated at full-scale level for
hexavalent chromium removal from drinking water (McGuire et al. 2007; Blute et a1.2013). The
conceptual process flow diagram of the RCF process is shown in Figure 4.19. In this process, the
hexavalent chromium (Cr[VI]) is reduced to trivalent chromium (Cr[III]) by ferrous ion from
ferrous sulfate addition. After reduction, the excess ferrous ion is oxidized using aeration or
chlorine addition. Filtration is then used to remove the co -precipitated iron and chromium.
Filtration is accomplished using granular media filters or microfiltration/ultrafiltration membranes.
This process results in backwash water from the filters, which will contain elevated levels of iron
and Cr(III) as well as other constituents removed by coagulation/filtration process. The solids
from the backwash water can be collected and processed onsite as shown in Figure 4.19. RCF
process can treat difficult waters, i.e., waters with high sulfate concentrations, high alkalinities and
94

radionuclides concentrations. RCF process is fairly complex to operate and maintain. It also has
a larger footprint compared to WBA and SBA exchange processes. Bench/pilot testing is
recommended prior to full-scale consideration of RCF process to develop site -specific design
criteria and costing information.
c r+ru c
T static Mixer
Reduction Tank w/ Mixer Aeration Tank
Groundwater
FE
mkwash Water
Storage Tan k
Dual
Media
Fiber
L L3 H
Firishi=d
n p Water
Product Water to Backwash Water Storage Tank
Spent Backwash
Holding Tank
M �y GraYlty
53udge
Thickened
Supernatant
� � n•o �a
T Hauled Oft -Site/
Belt Fifter Press Disposed to sewer
.__—------------------- — ------ — ------- /
--------------------------- �L, 1 Dewatered Solids > -+
*n
Ferrous sulfate Storage
& Handling System
Polymer Storage&
Handling System
— ------------------------------------ '
solids
Processing
o a
Hauled Off -Site/
Disposed to Sewer
Notes
P, Red lines denote backwash and waste streams
Figure 4.19 Reduction Coagulation Filtration (RCF) system process flow diagram
Advantages and Disadvantages
The key strengths and weaknesses of the RCF process are summarized in Table 4.25.
95

Strengths
Table 4.25
Strengths and weaknesses of RCF process
Weaknesses
RCF process is minimally affected by feed RCF process has multiple treatment steps
water quality. RCF is a robust process that which can result in a larger footprint.
can handle waters with elevated
concentrations of sulfate (unlike SBA
exchange process), co-occurring contaminants
and salts (TDS).
RCF process does not have chromatographic RCF process is fairly complex to operate and
peaking issues. maintain for a small system. Needs higher
skilled operators and significant operator
attention
RCF process has been extensively studied and RCF process requires handling of chemicals
applied for hexavalent chromium treatment by and residuals.
of Glendale, CA and other cities.
Residuals Disposal Considerations
The RCF process generates liquid and solid waste streams. The granular media or
membrane filters would require periodic backwashing. The backwash water will contain elevated
levels of iron, hexavalent chromium and other constituents. The solids from the backwash water
can be dewatered onsite using belt presses or centrifuges. Spent solids have to be characterized
using TCLP or California VVET prior to disposal.
96

CHAPTER 5
HEXAVALENT CHROMIUM TREATMENT DESIGN AND COSTING
TOOL
The Cr(VI) Treatment Design and Costing Tool was developed and included as a
deliverable of this project. This tool, along with the report, can serve as an initial step for a utility
in planning a hexavalent chromium removal project. By using the tool with project specific flow
rates and water quality parameters, utilities can assess basic design options and costs associated
with the various wellhead hexavalent chromium treatment options. Even though the tool is tailored
for specific water qualities, the findings and results of the tool should be verified by bench and/or
pilot testing prior to full-scale consideration. The tool was programmed as a series of Microsoft
Excel spreadsheets to prompt the user for input and conduct calculations. In order to successfully
use the tool, the user must interact with the input and output forms. The user will have to enter
information on the input form and then the tool will calculate design and cost parameters and
display the results on the output form. The tool specifically focuses on treatment technologies that
small water utilities can consider and implement, i.e., WBA and SBA exchange processes.
Input Parameters
To begin using the tool, the user must enter project specific parameters on the input form,
choosing values written within parenthesis. Input parameters are shown in Figure 5.1.
Once the input form is completed, user must open the output form and review the results.
Tool output consists of narration of application treatment technologies, budgetary cost opinions,
conceptual treatment plant footprint and residuals estimates, co-occurring contaminant water
quality warnings and residuals disposal warnings.
97

Flows
• Design Flow
• Average Flow
L-----------------
Input Parameters
Raw Water Qua Iity
• Hexavalent Chromium
• Sulfate
• Nitrate
• Arsenic
• Alkalinity
• Hardness
• pH
• Radionuclides
------------------------
Notes:
1. CC denotes Construction Cost Index
2. SLI denotes Skilled Labor Index
Financial Parameters
•
ENR CCI1 ;
+
ENR SLI2
+
Interest Rate
+
Payback Period ;
Figure 5.1 Cr(VI) treatment design and costing tool input form
Process Selection
Based on the inputs entered, the Cr(VI) Treatment Design and Costing Tool will
identify the feasible treatment options. The decision logic that the tool uses to identify the
appropriate treatment options is shown in Figure 5.2. The WBA exchange process is applicable
for a wide range of influent water sulfate concentrations. The SBA exchange processes are only
applicable for well waters with sulfate concentrations of less than 150 mg/L. The GIM process is
innovative and complex to implement for small systems. The RCF process is fairly robust and
may be applicable for well waters with high sulfate concentrations (> 150 mg/L) and other co-
occurring constituents (arsenic, nitrate, radionuclides, TDS). The RO process is energy intensive
and generates a reject stream. However, the RO process can be applicable for meeting multiple
water quality objectives, i.e., softening, removal of other constituents including desalination.
98

Raw Water Sulfate Concentration, mg/L
WBA Resin Exchange
Process —Single Use,
Series Operation
SBA Resin Exchange
Process — Single Use,
Series Operation
(Option 1)
WBA Resin Exchange
Process —Single Use,
Series Operation
SBA Resin Exchange
Process —Series
Operation with Onsite
Regeneration (Option 2)
150 -4 0- 300
WBA Resin Exchange
Process —Single Use,
Series Operation
SBA Resin Exchange SBA Resin Exchange
Process —Series Process —Parallel
Operation with Onsite Operation with Onsite
Regeneration (Option 2) Regeneration (Option 3)
SBA Resin Exchange
Process — Para I lei
Operation with Onsite
Regeneration (Option 3)
-------------------------------------- L ---------------------------------------- j -------------------------------------------
Granular iron Media • INNOVATIVE BUTCOMPLEX PROCESS
(GIM)
Reduction Coagulation • ROBUST BUT COMPLEX PROCESS- APPLICABLE FOR WATERS WITH
Filtration (RCF) MULTIPLE CONTAMINANTS OF CONCERN
# ENERGY INTENSIVE AND GENERATES BRINE WASTE - APPLICABLE
Reverse Osmosis (RO) FOR WATERS WITH MULTIPLE CONTAMINANTS OF CONCERN
Figure 5.2 Cr(VI) treatment process selection flowchart
99

Description of Calculations
The Cr(VI) Treatment Design and Costing Tool generates capital and operations and
maintenance (O&M) cost opinions for the feasible WBA and SBA exchange treatment options.
Flowchart illustrating the cost calculations within the tool is shown in Figure 5.3. Capital costs
are calculated based on cost equations that account for flow, ion exchange vessel sizes, number of
vessels, media transfer system, concrete pads, valves, pipes, electrical and instrumentation, media
staging area, media for first fill, media replacement and as -needed chemical adjustments. The cost
equations are applicable for the flow range of 200-1,600 gpm. The capital costs are adjusted to
March 2016 dollars based on the Engineering News Record (ENR) 20-Cities Average
Construction Cost Index (CCI) of 10,242.09.
The O&M costs are calculated using equations for resin utilization, process energy, labor,
and analytical costs. The O&M costs account for resin regeneration or replacement (whichever is
applicable for the option) and the frequency of regeneration or replacement is determined based
on the water quality inputs. O&M cost opinions are expressed in March 2016 dollars,
corresponding with an ENR 20-Cities Average Skilled Labor Index (SLI) of 9771.84.
The total costs are presented in several formats including the total present worth cost, total
annual cost, and cost per 1,000 gallons treated for comparison of the various treatment alternatives.
Consider Design
and Average
Flows Inputted
Capital Cost = f (Design Flow)
_ [a (Design Flow)+b] (ENRcc1/ENRcc1-bare)
O&M Cost = f (Average Flow)
[a (Average Flow)+ b] (ENRsL,JENRsu•base)
Cost per 1,000 gals Treated Present Worth Total Cost
= (Amortized Capital Cost + = Capital Cost + Present
O&M Cost) /Average Flow Worth O&M Cost
Figure 5.3 Capital, O&M, and total cost computations flowchart
The conceptual cost opinions generated by the Cr(VI) Treatment Design and Costing Tool
are considered to fall within the range of Class 5 estimates as defined by the Association for the
Advancement of Cost Engineering (RACE) International. These levels of engineering cost
estimating are generally conducted on the basis of limited preliminary information and without
detailed information such as process and instrumentation diagrams, engineering layouts, and
equipment schedules. This level of cost estimating is appropriate for budgetary planning purposes,
100

assessment of initial viability, evaluation of alternative plans and project feasibility screening.
Typical accuracy ranges recognized for Class 5 estimates are -30% to +50%.
Capital cost opinions are expressed in March 2016 dollars, corresponding with an
Engineering News Record (ENR) 20-Cities Average Construction Cost Index (CCI) of 10,242.09.
O&M cost opinions are expressed in March 2016 dollars, corresponding with an Engineering
News Record (ENR) 20-Cities Average Skilled Labor Index (SLI) of 9771.84. The user can adjust
capital and O&M cost opinions to another time period by entering different input values for the
ENR CCI and SLI.
The flowchart illustrating the residuals and plant footprint computations is shown in Figure
5.4. To calculate the volume of brine waste and rinse water, the tool uses design parameters of
suggested bed volumes, regeneration frequencies calculated based on input parameters, suggested
loading rates and suggested backwash times for each treatment option to determine the overall
volume of brine waste water and rinse water. Spent resin waste was calculated based on design
resin quantity per vessel and number of resin replacements per year, which depend on raw water
quality and onsite regeneration information. The plant footprint is estimates based on the space
required for ion exchange resin vessels, waste tanks, spent media storage, pH adjustment system
tanks and brine storage tanks.
101

is Resin Regenerated Onsite ?
Brine Waste Volume (gal/Regeneration) =
Number of Bed Volume for Regeneration x
Volume of Media per Vessel (gal)
Rinse Volume (gal) = Bed Volume (gal) x Rinse Time
where, Bed Volume (gal) = EBCT (min) x Design Flow (gpm)
No Brine Waste
Resin Waste (Ibs/year) = Resin Quantity per Vessel (Ibs) x
Number of Resin Replacement per Year
where, Number of Resin Replacement = f(Water Quality, Onsite Regeneration)
• Waste tank vessel design need to consider bigger residual volume between backwash
and ri nse vol u mes.
Is pH Adjustment or Resin
Regeneration necessary
Plant Footprint = Footprint of Vessels +
Backwash Tank+ Spent Media Storage + pH
Adjustment System + Brine Waste Storage
Plant Footprint = f(Design Flow)
= a (Design Flow)+ b
Plant Footprint = Footprint of Vessels +
Backwash Tank+ Spent Media Storage
Plant Footprint = f(Design Flow)
= a (Design Flow)+ b
Figure 5.4 Residuals and plant footprint flowchart
102

CHAPTER 6
SUMMARY AND CONCLUSIONS
SUMMARY
A bench -scale study on the removal of hexavalent chromium from drinking water was
conducted with the primary focus on affordable treatment technologies for water utilities needing
to treat 2 MGD or less. Four ion exchange media, including two SBA media, two WBA media,
and two iron -based media were evaluated. The performance of each media type was assessed in
water supplied by five participating utilities that represented a range of water quality parameters.
The media performance was also evaluated when competing solutes were present. These included
sulfate, nitrate, chloride, silicon, alkalinity, and natural organic matter.
After careful evaluation of all bench -scale results, three media were selected for further
testing in small-scale columns. These media included the two SBA media (ResinTech SBG1 and
Purolite A600E/9149) and the Purolite S 106 WBA media. Synthetically prepared water was
pumped into the top of each column in a down -flow configuration. A column diameter of %2" (1.3
cm) and eight inches (20 cm) of media height were used. A 2-minute empty bed contact time
(EBCT) was used for all tests. Each column test was run until breakthrough of Cr(VI) (set at 8
µg/L- 80% of the CA MCL) occurred or until the pressure head became too great to maintain the
flow. The tests included various levels of sulfate (20, 60, and 150 mg/L) with or without additional
arsenic and nitrate. Arsenic and nitrate were added to some tests to evaluate whether a
phenomenon called `chromatographic peaking' occurred and whether it could be a concern to
utilities. Chromatographic peaking occurs when one ion at high concentration displaces another
ion that is also removed by the ion exchange media, resulting in a concentration spike of even
greater concentration than the influent.
TCLP and California WET tests were conducted on the spent media from these tests to
give further information on what to expect during media disposal.
Results from the bench -scale testing and the small-scale column testing were used to
develop practical guidance for selecting a treatment technology for smaller utilities. A Microsoft
Excel spreadsheet tool was created, as well as conceptual treatment footprints and budgetary -level
cost opinions.
CONCLUSIONS
All media tested were able to remove Cr(VI) to levels well below the California MCL;
however, other water quality parameters played an important role in determining the most
appropriate treatment.
The iron -based media removed Cr(VI) to extremely low levels in almost all water
chemistries tested including when competing ions were present, but the release of iron from the
media would likely require an additional iron removal treatment process. For this reason, these
media were not evaluated during the column testing portion of this study. However, in situations
where waste disposal might be an issue the Cleanit®-LC media should be considered.
SBA media life was highly dependent on influent sulfate concentration, although other
water quality parameters are critical when evaluating whether SBA is suitable. WBA is a more
robust treatment technology, as sulfate concentration has little effect on performance, but this
technology is more complex to operate (due primarily to the pH adjustment required).
103

Both SBA and WBA removed sulfate from influent water while releasing chloride,
although these levels of chloride will not materially impact the potable water quality.
• SBA removed nitrate from influent water more efficiently than WBA.
• Both SBA and WBA removed uranium and arsenic, but had no effect on silicon
concentration.
• Freundlich isotherms proved to be excellent models for Cr(VI) removal from utility -
supplied waters for both SBA and WBA resins.
• Cr(VI) removal decreased as sulfate concentration was increased for both SBA and
WBA media.
• Cr(VI) removal decreased as silicon concentration was increased for SBA media but
there was no effect while using WBA.
• Nitrate concentration had no effect on Cr(VI) removal using SBA until a concentration
of 5 mg/L as N was reached, at which point Cr(VI) decreased. Elevating nitrate
concentration adversely affected Cr(VI) while using WBA.
• No consistent trends were observed in Cr(VI) removal when chloride, alkalinity, or
NOM concentrations were varied.
During the small-scale column tests, sulfate concentration greatly affected the time before
breakthrough.
• With 20 mg/L sulfate, no breakthrough of Cr(VI) was observed during the test (5000
BV) for any of the media tested, and if fact Cr(VI) never increased above 1 µg/L in the
column effluent.
• With 60 mg/L sulfate, breakthrough (8 µg/L) of Cr(VI) for SBA occurred around 6000
BVs. Cr(VI) had increased to 7 µg/L at 7000 BVs for WBA.
• With 150 mg/L sulfate, breakthrough of Cr(VI) for SBA occurred around 2500 BVs.
Cr(VI) had increased to 6 µg/L at 7000 BVs for WBA, although a brief period between
1600-2200 BVs saw an increase in Cr(VI) above 8 µg/L.
Higher sulfate concentrations can cause chromatographic peaking of nitrate or arsenic
above their respective MCLs if those elements are present in high enough concentrations in the
influent water.
• Huge arsenic peaks (3.6 — 4.6x influent) can occur at high levels of sulfate (150 mg/L)
using SBA at extremely low run-times (400-650 BVs).
• When sulfate is moderate (60 mg/L), arsenic peaks are about 3x influent for SBA and
occur between 850-1400 BVs.
• At low sulfate (20 mg/L), arsenic peaks are about 1.3-1.4x influent for SBA and occur
between 1300-3400 BVs (i.e., a longer duration but less intense peak).
• No nitrate peaking was observed with WBA.
• Nitrate peaks with SBA occurred nearly concurrently with arsenic peaks but with less
intense peaks (1.2x influent at 20 mg/L sulfate; 1.9x influent at 60 mg/L sulfate; 2x
influent at 150 mg/L sulfate).
High influent alkalinity can result in high O&M costs for WBA due to the pH adjustment
required.
104

ResinTech SBG1 SBA media released less chromium during the TCLP testing than did the
Purolite A600E/9149 SBA media. Very little chromium was released from the Purolite S 106
WBA media during TCLP testing.
105

CHAPTER 7
RECOMMENDATIONS
RECOMMENDATIONS FOR FUTURE WORK
SBA and WBA and iron media have been studied in detail in this project and several
previous projects. This report synthesizes the cumulative results of this body of work into practical
guidance to help utilities anticipating or requiring treatment for Cr(VI) comply efficiently.
Additional research may assist with the optimization of existing California BATs, such as:
• Further developing the understanding of the secondary Cr(VI) removal mechanisms of
WBA will help to refine performance (and therefore cost) estimates.
• Determining the effect of SBA media on the aggressiveness of product water (through
TDS and alkalinity removal) will help understand potential long-term impacts on the
distribution system.
• More in-depth study of the chromatographic peaking phenomenon as a function of
sulfate concentration so that utilities can be better informed of the risks.
• Determining if increased hardness results in media scaling and how that can affect
Cr(VI) removal.
Newly developed media should also be evaluated for Cr(VI) removal in a manner similar
to this study. GIM should be reevaluated if changes are made to the media to control iron release.
RECOMMENDATIONS FOR UTILITIES
Smaller utilities with water requirements of 2 MGD or less can benefit from the Microsoft
Excel spreadsheet tool developed as part of this study. This tool incorporates most of the findings
of this study such that an informed choice can be made between SBA and WBA, which have been
identified as probable candidates.
Sulfate concentration and alkalinity are the major drivers when deciding between SBA and
WBA. Increased sulfate concentrations (greater than 50 mg/L) adversely affect SBA media
runtimes and can cause chromatographic peaking of nitrate and arsenic while waters with high
alkalinity make WBA costly to operate. Operation of lead/lag vessels or parallel treatment may
be required with SBA to counter the peaking of nitrate or arsenic if their influent concentrations
are great enough. The long runtimes capable with WBA can also lead to accumulation of uranium
in residuals, making disposal costlier.
Other California BATS not included in this study should be considered before a final
decision is made. While cost opinions and treatment footprints described in this study can be used
for planning purposes, specific utility circumstances should be fully evaluated taking into account
site specific needs.
107

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110

ABBREVIATIONS
AACE
Association for the Advancement of Cost Engineering
ANSI
American National Standards Institute
APHA
American Public Health Association
As (III)
trivalent arsenic
As (V)
pentavalent arsenic
ASTM
American Society for Testing and Materials
AWWA
American Water Works Association
BAT
best available technology
BV
bed volume
C/Co
normalized concentration (concentration divided by initial concentration)
cm
centimeter
Cr(III)
trivalent chromium
Cr(VI)
hexavalent chromium
CVWD
Coachella Valley Water District
EPA U. S. Environmental Protection Agency
FE flow element (flow meter)
fps feet per second
ft feet
g gram
GAM granular adsorption media
gpm/sf gallons per minute per square feet
HDPE
hr
high density polyethylene
hour
ICP-MS
inductively coupled plasma mass spectrometer
ID
inner diameter
IXTP
ion exchange treatment plant
kg
kilogram
kWh
kilowatt hour
lb pound
LLRW Low Level Radioactive Waste
MCL maximum contaminant level
MCLG maximum contaminant level goal
MGD million gallons per day
mg/kg milligrams per kilogram
111

mg/l milligrams per liter
mm millimeter
mps meters per second
µg/L micrograms per liter
n/a
not applicable
n/m
not measured
NRC
Nuclear Regulatory Commission
O&M
Operation and Maintenance
OD
outer diameter
POTW Publicly Owned Treatment Works
ppb parts per billion
ppm parts per million
QTY quantity
RCF
Reduction Coagulation Filtration
RO
Reverse Osmosis
RPM
revolutions per minute
RSD
relative standard deviation
SBA
Strong Base Anion
STLC
Soluble Threshold Limit Concentration
SU
Standard Units
TCLP Toxicity Characteristic Leaching Pressure
TENORM Technologically Enhanced Naturally Occurring Radioactive Material
TOC total organic carbon
TTLC Total Threshold Limit Concentration
WBA Weak Base Anion
WET Waste Extraction Test
112