Drinking Water Treatment for Nitrate

Drinking Water Treatment for Nitrate
Addressing Nitrate in California’s Drinking Water
TECHNICAL REPORT 6:
Drinking Water Treatment for Nitrate
With a Focus on Tulare Lake Basin and Salinas Valley Groundwater
Report for the State Water Resources Control Board Report to the Legislature
California Nitrate Project,
Implementation of Senate Bill X2 1
Center for Watershed Sciences
University of California, Davis
http://groundwaternitrate.ucdavis.edu
Prepared for the California State Water Resources Control Board
Drinking Water Treatment for Nitrate
Technical Report 6
Addressing Nitrate in California’s Drinking Water
With a Focus on Tulare Lake Basin and Salinas Valley Groundwater
Report for the State Water Resources Control Board Report to the Legislature
Prepared by:
Vivian B. Jensen and Jeannie L. Darby1 of UC Davis
Chad Seidel and Craig Gorman of Jacobs Engineering Group, Inc.2
Center for Watershed Sciences
University of California, Davis
California Nitrate Project, Implementation of Senate Bill X2 1
Prepared for:
California State Water Resources Control Board
July 2012
1
Corresponding author: [email protected]
The first portion of this document (through the end of Section 3) was developed concurrently for the American Water Works
Association (AWWA) as the report titled An Assessment of the State of Nitrate Treatment Alternatives (2011) through
collaboration with Chad Seidel, Ph.D., P.E. and Craig Gorman, M.S., P.E. of Jacobs Engineering Group, Inc.
2
Suggested Citation:
Jensen, V.B., Darby, J.L., Seidel, C. & Gorman, C. (2012) Drinking Water Treatment for Nitrate. Technical Report 6
in: Addressing Nitrate in California’s Drinking Water with a Focus on Tulare Lake Basin and Salinas Valley
Groundwater. Report for the State Water Resources Control Board Report to the Legislature. Center for Watershed
Sciences, University of California, Davis.
An electronic copy of this Final Report is available from the following website:
http://groundwaternitrate.ucdavis.edu
Copyright ©2012 The Regents of the University of California
All rights Reserved
The University of California prohibits discrimination or harassment of any person on the basis of race, color,
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against any person in any of its programs or activities for making a complaint of discrimination or sexual
harassment or for using or participating in the investigation or resolution process of any such complaint. University
policy is intended to be consistent with the provisions of applicable State and Federal laws.
Disclaimer: This document is intended as a guide of nitrate treatment technologies and should be used as an
informational tool only. The contents of this document are solely the responsibility of the authors and do not
necessarily represent the official views of supporting agencies. The selection and design of the most appropriate
nitrate treatment alternative for a particular water system depend on a variety of factors and require the expertise
of experienced professional engineers. Discussion of proprietary technologies is intended to provide information
about treatment alternatives and does not imply endorsement.
For further inquiries, please contact
Thomas Harter, Ph.D.
[email protected]
125 Veihmeyer Hall
University of California
Davis, CA 95616-8628
Phone: 530-752-2709
Acknowledgments
This document is largely based on the report titled An Assessment of the State of Nitrate Treatment
Alternatives (2011) prepared for the American Water Works Association (AWWA) through collaboration
with Chad Seidel, Ph.D., P.E. and Craig Gorman, M.S., P.E. of Jacobs Engineering Group, Inc.3
Special thanks to the members of the AWWA Inorganic Contaminants Research and Inorganic Water
Quality Project Subcommittee:
Name
Affiliation
Michelle De Haan, Chair
Water Works Engineers
Jennifer Baldwin, Chair
CH2M HILL
Jess Brown
Carollo Engineers
Susan Brownstein
California Department of Public Health
Dennis Clifford
University of Houston
Elise Harrington
AWWA
Tarrah Henrie
California Water Service Company
France Lemieux
Health Canada
Jerry Lowry
Lowry Systems, Inc.
Support for this research was provided from the following sources:

American Water Works Association Technical & Education Council

California Department of Public Health Safe Drinking Water Revolving Fund Contract No. 0655254

California State Water Resources Control Board, Contract No. 09-122-250
3
The first portion of this document (through the end of Section 3) was developed concurrently for the American Water Works
Association (AWWA) as the report titled An Assessment of the State of Nitrate Treatment Alternatives (2011) through
collaboration with Chad Seidel, Ph.D., P.E. and Craig Gorman, M.S., P.E. of Jacobs Engineering Group, Inc.
Technical Report 6: Drinking Water Treatment for Nitrate
The authors would like to thank the following for their contributions to the project:
Carolina
Paul
Holly
Paul
Rob
Marc
Jesse
Laurel
Wayne
Anna
Charles
Kristin
Chris
Sally
Aaron
Betsy
Karl
Elena
Eli
Sam
Joe
Jim
Cheryl
Balazs
Boyer
Canada
Collins
Coman
Commandatore
Dhaliwal
Firestone
Fox
Fryjoff-Hung
Hemans
Honeycutt
Johnson
Keldgord
King
Lichti
Longley
Lopez
Moore
Perry
Prado
Quinn
Sandoval
Andrew
Leah
Emily
Tran
Walker
Wallace
University of California, Berkeley
Self-Help Enterprises
UCD – Center for Watershed Sciences
CDPH Division of Drinking Water and Environmental Management
UCD – Information Center for the Environment
CDPH Division of Drinking Water and Environmental Management
CDPH – Southern California Drinking Water Field Operations Branch
Community Water Center
Fresno County Environmental Health
UCD – Center for Watershed Sciences
Tulare County Department of Environmental Health – Water Program
UCD – Center for Watershed Sciences
Aegis Groundwater Consulting, LLC
Kern County Environmental Health
UCD – Center for Watershed Sciences
CDPH – Fresno District Engineer
CSU Fresno
UCD – Center for Watershed Sciences
Pacific Institute
Washington State Department of Health Engineer
Fresno County
UCD – Information Center for the Environment
Monterey County Health Department – Drinking Water Protection
Services
UCD – Graduate Student Researcher
CDPH – Division of Drinking Water and Environmental Management
UCD – Undergraduate Student Assistant
Additionally, the authors would like to thank the drinking water utilities that participated in the survey
and the treatment technology vendors for their contributions to the project.
Technical Report 6: Drinking Water Treatment for Nitrate
Contents
Tables ............................................................................................................................................................ v
Figures ......................................................................................................................................................... vii
Acronyms and Abbreviations ....................................................................................................................... ix
Unit Conversions .......................................................................................................................................... xi
Summary ....................................................................................................................................................... 1
Objective ................................................................................................................................................... 1
Background ............................................................................................................................................... 1
Approach ................................................................................................................................................... 2
Findings ..................................................................................................................................................... 5
Non-Treatment Options ........................................................................................................................ 5
Treatment Options ................................................................................................................................ 5
Conclusions ............................................................................................................................................... 9
1 Introduction ............................................................................................................................................. 12
1.1 Management Options for Nitrate in Potable Water ......................................................................... 12
2 Non-Treatment Options for Nitrate Contaminated Potable Water ........................................................ 14
2.1 Well Abandonment, Inactivation, and Destruction .......................................................................... 14
2.2 Wellhead Protection and Land Use Management ............................................................................ 14
2.3 Development of Alternative Sources and Source Modification ....................................................... 14
2.4 Blending ............................................................................................................................................ 16
3 Treatment Options for Nitrate Contaminated Potable Water ................................................................ 18
3.1 Ion Exchange (IX) ............................................................................................................................... 21
3.1.1 Conventional Ion Exchange ........................................................................................................ 21
3.1.2 Ion Exchange - Design Considerations ....................................................................................... 23
3.1.3 Ion Exchange - Cost Considerations ........................................................................................... 28
Technical Report 6: Drinking Water Treatment for Nitrate
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3.1.4 Ion Exchange - Selected Research.............................................................................................. 29
3.1.5 Ion Exchange - Summary of Advantages and Disadvantages .................................................... 29
3.1.6 Modifications to Conventional Ion Exchange ............................................................................ 29
3.1.7 Ion Exchange - Case Studies ....................................................................................................... 35
3.2 Reverse Osmosis (RO) ....................................................................................................................... 48
3.2.1 Reverse Osmosis - Design Considerations ................................................................................. 48
3.2.2 Reverse Osmosis - Cost Considerations ..................................................................................... 53
3.2.3 Reverse Osmosis - Selected Research ........................................................................................ 54
3.2.4 Reverse Osmosis - Summary of Advantages and Disadvantages............................................... 54
3.2.5 Reverse Osmosis - Improvements and Modifications ............................................................... 55
3.2.6 Reverse Osmosis - Case Studies ................................................................................................. 57
3.3 Electrodialysis (ED/EDR/SED) ............................................................................................................ 73
3.3.1 Electrodialysis - Design Considerations ..................................................................................... 75
3.3.2 Electrodialysis - Cost Considerations ......................................................................................... 77
3.3.3 Electrodialysis - Selected Research ............................................................................................ 78
3.3.4 Electrodialysis - Summary of Advantages and Disadvantages ................................................... 78
3.3.5 Modifications to Electrodialysis ................................................................................................. 79
3.3.6 Electrodialysis - Case Studies ..................................................................................................... 80
3.4 Biological Denitrification (BD) ........................................................................................................... 88
3.4.1 Biological Denitrification - Design Considerations ..................................................................... 90
3.4.2 Biological Denitrification - Cost Considerations......................................................................... 95
3.4.3 Biological Denitrification - Selected Research ........................................................................... 96
3.4.4 Biological Denitrification - Summary of Advantages and Disadvantages .................................. 96
3.4.5 Biological Denitrification - Case Studies..................................................................................... 97
3.5 Chemical Denitrification (CD).......................................................................................................... 106
Technical Report 6: Drinking Water Treatment for Nitrate
ii
3.5.1 Zero Valent Iron (ZVI) ............................................................................................................... 106
3.5.2 Catalytic Denitrification ........................................................................................................... 108
3.5.3 Chemical Denitrification - Design Considerations.................................................................... 108
3.5.4 Chemical Denitrification - Emerging Technologies .................................................................. 110
3.5.5 Chemical Denitrification - Cost Considerations ....................................................................... 113
3.5.6 Chemical Denitrification - Selected Research .......................................................................... 114
3.5.7 Chemical Denitrification - Summary of Advantages and Disadvantages ................................. 114
3.6 Brine Treatment Alternatives and Hybrid Treatment Systems....................................................... 114
3.6.1 Electrochemical Destruction of Nitrate in Waste Brine ........................................................... 115
3.6.2 Catalytic Treatment of Waste Brine......................................................................................... 116
3.7 Residential Treatment (Point-of-Use, Point-of-Entry) .................................................................... 117
4 Tulare Lake Basin and Salinas Valley - Water Quality Analysis .............................................................. 120
4.1 Water Quality - Treatment Interference......................................................................................... 121
4.2 Water Quality - Co-contaminants ................................................................................................... 121
4.3 Water Quality and Treatment Selection ......................................................................................... 128
5 Addressing Nitrate Impacted Potable Water Sources in California ....................................................... 130
5.1 Well Abandonment, Destruction and Inactivation ......................................................................... 130
5.2 Survey of Blending and Treating Systems ....................................................................................... 133
6 Treatment Cost Analysis ........................................................................................................................ 139
6.1 Costs by Treatment Type ................................................................................................................ 141
6.2 Costs by System Size ....................................................................................................................... 144
6.3 Costs by Water Quality Parameters ................................................................................................ 147
6.4 Disposal Costs ................................................................................................................................. 149
7 Guidance for Addressing Nitrate Impacted Drinking Water .................................................................. 152
7.1 Checklist for the Selection of Mitigation Strategy .......................................................................... 152
Technical Report 6: Drinking Water Treatment for Nitrate
iii
7.2 Decision Trees ................................................................................................................................. 153
8 Summary and Conclusions ..................................................................................................................... 155
9 Literature Cited ...................................................................................................................................... 157
10 Appendix .............................................................................................................................................. 175
10.1 Tables of Selected Research ......................................................................................................... 175
Technical Report 6: Drinking Water Treatment for Nitrate
iv
Tables
Table S.1. Utilities included in the case studies. .......................................................................................... 4
Table S.2. Potable water treatment options for nitrate management ........................................................ 6
Table S.3. Comparison of major treatment types. ..................................................................................... 11
Table 1. Utilities included in the case studies. ........................................................................................... 19
Table 2. Potable water treatment options for nitrate management......................................................... 20
Table 3. Selection of full-scale ion exchange installations for nitrate removal. ........................................ 21
Table 4. Summary of design considerations for conventional IX. .............................................................. 24
Table 5. Selected published costs of ion exchange systems for nitrate removal. ..................................... 29
Table 6. Summary of design considerations for reverse osmosis. ............................................................. 49
Table 7. Selected costs of reverse osmosis systems for nitrate removal. ................................................. 54
Table 8. Summary of design considerations for electrodialysis/electrodialysis reversal. ......................... 75
Table 9. Sample EDR O&M costs. ............................................................................................................... 78
Table 10. Full-scale biological denitrification systems for potable water treatment. ............................... 89
Table 11. Summary of design considerations for biological denitrification for nitrate removal. .............. 90
Table 12. Membrane biological reactor configurations............................................................................. 94
Table 13. Cost information for biological denitrification of potable water. .............................................. 96
Table 14. Summary of design considerations for chemical denitrification.............................................. 109
Table 15. Selected research on brine treatment alternatives and hybrid systems ................................. 115
Table 16. Costs of POU treatment for nitrate removal. ........................................................................... 119
Table 17. Summary of water quality data of high nitrate wells in Tulare Lake Basin and Salinas Valley.120
Table 18. Comparison of major treatment types. .................................................................................... 129
Table 19. Influence of nitrate concentration on treatment selection. .................................................... 129
Table 20. Incidence of abandonment, destruction, and inactivation of nitrate impacted wells............. 131
Table 21. Population and nitrate levels of systems in the study area treating or blending for nitrate... 137
Technical Report 6: Drinking Water Treatment for Nitrate
v
Table 22. Nitrate level, well depth and well capacity for a Tulare County blending system. .................. 138
Table 23. Cost estimation using U.S. EPA cost curves of IX for arsenic removal. .................................... 140
Table 24. Summary of anion exchange and reverse osmosis cost information by system size. ............. 146
Table 25. An exercise in the estimation of treatment costs based on nitrate levels. ............................. 148
Table 26. Brine disposal costs. ................................................................................................................. 150
Table A.1. Selected research on the use of ion exchange for nitrate removal. ....................................... 175
Table A.2. Selected research on the use of reverse osmosis for nitrate removal. .................................. 176
Table A.3. Selected research on the use of electrodialysis for nitrate removal. ..................................... 177
Table A.4. Selected research on the use of biological denitrification for nitrate removal. ..................... 178
Table A.5. Selected research on the use of chemical denitrification for nitrate removal. ...................... 181
Table A.6. Advantages and disadvantages of the five major treatment options for nitrate removal. .... 182
Technical Report 6: Drinking Water Treatment for Nitrate
vi
Figures
Figure S.1. Summary of nitrate management options. ................................................................................ 2
Figure 1. Selective well screening using a packer/plug.............................................................................. 16
Figure 2. Conventional ion exchange schematic........................................................................................ 22
Figure 3. Process flow diagram for counter current MIEX® process. ........................................................ 30
Figure 4. Vessel rotation in Calgon Carbon countercurrent ISEP® system. ............................................... 32
Figure 5. Example of flow through the ISEP® system. ............................................................................... 32
Figure 6. Example of an Envirogen multiple bed proprietary anion exchange system. ............................ 33
Figure 7. Process schematic of weak base ion exchange for nitrate ("WIN" process). ............................. 35
Figure 8. Reverse osmosis schematic......................................................................................................... 48
Figure 9. Flow chart of the HERO™ process. .............................................................................................. 56
Figure 10. Electrodialysis reversal schematic. ........................................................................................... 73
Figure 11. Illustration of electrodialysis membrane stack. ........................................................................ 74
Figure 12. Biological denitrification schematic. ......................................................................................... 88
Figure 13. FBR configuration. ..................................................................................................................... 98
Figure 14. FBR treatment system schematic. .......................................................................................... 100
Figure 15. Surface chemistry of ZVI particles ........................................................................................... 107
Figure 16. Process schematic for denitrification using SMI-III®. .............................................................. 111
Figure 17. Schematic of the brine treatment system developed by Ionex SG Limited. .......................... 116
Figure 18. Schematic of an ion exchange system with brine regeneration coupled with catalytic
treatment of brine for reuse. ............................................................................................................ 116
Figure 19. Raw water nitrate levels exceeding the MCL .......................................................................... 122
Figure 20. Raw water high nitrate wells with high arsenic levels. ........................................................... 123
Figure 21. Raw water high nitrate wells with high perchlorate levels..................................................... 124
Figure 22. Raw water high nitrate wells with pesticides detected. ......................................................... 125
Technical Report 6: Drinking Water Treatment for Nitrate
vii
Figure 23. Salinas Valley [As] versus total well depth (deepest water) and [NO3-] versus depth to top of
screen (shallowest water). ................................................................................................................ 127
Figure 24. Tulare Lake Basin [As] versus total well depth (deepest water) and [NO3-] versus depth to top
of screen (shallowest water). ............................................................................................................ 127
Figure 25. Tulare Lake Basin: Incidence of nitrate and arsenic MCL exceedance with well depth. ........ 128
Figure 26. Location of nitrate impacted abandoned, destroyed, and inactivated wells. ........................ 132
Figure 27. Digital survey distributed to drinking water systems treating and/or blending to address high
nitrate levels. .................................................................................................................................... 134
Figure 28. California drinking water systems treating and/or blending for nitrate................................. 135
Figure 29. Drinking water systems treating or blending for nitrate in the Tulare Lake Basin and Salinas
Valley. ................................................................................................................................................ 136
Figure 30. Wells of a blending system in Tulare County. ......................................................................... 138
Figure 31. Average cost comparison of nitrate treatment technologies. ................................................ 142
Figure 32. Costs of anion exchange for nitrate treatment. ..................................................................... 143
Figure 33. Costs of reverse osmosis for nitrate treatment. ..................................................................... 143
Figure 34. Costs of biological denitrification in drinking water treatment. ............................................. 144
Figure 35. Cost curve of IX (blue) and RO (red) for nitrate removal. ....................................................... 145
Figure 36. Decision Tree 1 - Options to address nitrate impacted drinking water sources .................... 153
Figure 37. Decision Tree 2 - Anion exchange. .......................................................................................... 154
Technical Report 6: Drinking Water Treatment for Nitrate
viii
Acronyms and Abbreviations
AF
AFY
AWWA
BMP
BD
BV
CD
CIP
DBP
DL
DO
EBCT
ED
EDR
FBR
FXB
GAC
GHG
GPM
GWUDI
HERO™
HLR
ISEP®
IX
LSI
MBfR
MBR
MCL
MGD
MIEX®
NDMA
O&M
PICME
POE
POU
PRB
RO
SBA IX
SBR
Acre Feet
Acre Feet per Year
American Water Works Association
Best Management Practice
Biological Denitrification
Bed Volume
Chemical Denitrification
Clean-In-Place
Disinfection Byproduct
Detection Limit
Dissolved Oxygen
Empty Bed Contact Time
Electrodialysis
Electrodialysis Reversal
Fluidized Bed Reactor
Fixed Bed Reactor
Granular Activated Carbon
Greenhouse Gas
Gallons per Minute
Groundwater Under Direct Influence (of Surface Water)
High Efficiency Reverse Osmosis
Hydraulic Loading Rate
Ion Exchange Separation System
Ion Exchange
Langelier Saturation Index
Membrane Biofilm Reactor
Membrane Bioreactor
Maximum Contaminant Level
Million Gallons per Day
Magnetic Ion Exchange
N-nitrosodimethylamine
Operations and Maintenance
Permits Inspection Compliance Monitoring and Enforcement
Point-of-Entry
Point-of-Use
Permeable Reactive Barrier
Reverse Osmosis
Strong Base Anion Exchange
Sequencing Batch Reactor
Technical Report 6: Drinking Water Treatment for Nitrate
ix
SDI
SDWA
SED
SMI
TDS
TSS
ULPRO
USBR
U.S. EPA
VSEP
WAC
WBA IX
WQM
ZVI
Silt Density Index
Safe Drinking Water Act
Selective Electrodialysis
Sulfur Modified Iron
Total Dissolved Solids
Total Suspended Solids
Ultra-Low Pressure Reverse Osmosis
Up-flow Sludge Blanket Reactor
United States Environmental Protection Agency
Vibratory Shear Enhanced Process
Weak Acid Cation Exchange
Weak Base Anion Exchange
Water Quality Monitoring
Zero Valent Iron
Technical Report 6: Drinking Water Treatment for Nitrate
x
Unit Conversions
Metric to US
US to Metric
Mass
Mass
1 gram (g)
0.04 ounces (oz)
1 ounce
28.35 grams
1 kilogram (kg)
2.2 pounds (lb)
1 pound
0.45 kilograms
1 megagram (Mg) (1 tonne)
1.1 short tons
1 short ton (2000 lb)
0.91 megagrams
1 gigagram (Gg) (1000 tonnes)
1102 short tons
1000 short tons
0.91 gigagrams
Distance
Distance
1 centimeter (cm)
0.39 inches (in)
1 inch
2.54 centimeters
1 meter (m)
3.3 feet (ft)
1 foot
0.30 meters
1 meter (m)
1.09 yards (yd)
1 yard
0.91 meters
1 kilometer (km)
0.62 miles (mi)
1 mile
1.61 kilometers
Area
2
Area
2
1 square meter (m )
10.8 square feet (ft )
2
2
1 square foot
0.093 square meters
1 square kilometer (km )
0.39 square miles (mi )
1 square mile
2.59 square kilometers
1 hectare (ha)
2.8 acres (ac)
1 acre
0.40 hectares
Volume
1 liter (L)
Volume
0.26 gallons (gal)
3
1 cubic meter (m ) (1000 L)
3
1 cubic kilometer (km )
1 gallon
3.79 liters
35 cubic feet (ft )
1 cubic foot
0.03 cubic meters
0.81 million acre-feet
(MAF, million ac-ft)
1 million acre-feet
1.23 cubic kilometers
3
Farm Products
Farm Products
1 kilogram per hectare (kg/ha)
0.89 pounds per acre
(lb/ac)
1 pound per acre
1.12 kilograms per
hectare
1 tonne per hectare
0.45 short tons per acre
1 short ton per acre
2.24 tonnes per hectare
Flow Rate
Flow Rate
1 cubic meter per day
3
(m /day)
0.296 acre-feet per year
(ac-ft/yr)
1 acre-foot per year
3.38 cubic meters per
day
1 million cubic meters per day
3
(million m /day)
264 mega gallons per day
(mgd)
1 mega gallon per day
(694 gal/min)
0.0038 million cubic
meters/day
Nitrate Units
-
*Unless otherwise noted, nitrate concentration is reported as milligrams/liter as nitrate (mg/L as NO3 ).
To convert from:
Nitrate-N (NO3-N)

Nitrate (NO3 )
multiply by 4.43
Nitrate (NO3 )

Nitrate-N (NO3-N)
multiply by 0.226
Technical Report 6: Drinking Water Treatment for Nitrate
xi
Summary
Objective
The purpose of the first three sections of this document is to provide a detailed guide to the current
state of nitrate treatment alternatives that can be used as a reference tool for the drinking water
community. The remainder of this document focuses on nitrate treatment of drinking water in
California and specifically in the Tulare Lake Basin and the Salinas Valley.
Background
Nitrate contamination of potable water sources is becoming one of the most important water quality
concerns in California and across the United States. The maximum contaminant level (MCL) for nitrate is
45 mg/L as nitrate (NO3-), which is approximately equivalent to 10 mg/L as nitrogen (N). The major
health concern of nitrate exposure through drinking water is the risk of methemoglobinemia, or “blue
baby syndrome,” especially in infants and pregnant women. Due to the nature of the infant digestive
system, nitrate is reduced to nitrite which can render hemoglobin unable to carry oxygen (SWRCB 2010).
Nitrate is naturally occurring at low levels in most waters, but it is particularly prevalent in groundwater
that has been impacted by certain agricultural, commercial, or industrial activities. Of specific concern
are crop fertilization activities and discharges from animal operations, wastewater treatment facilities,
and septic systems. Small rural communities are particularly impacted by nitrate (Pacific Institute 2011).
Nitrate presents unique water treatment challenges. The United States Environmental Protection
Agency (U.S. EPA) lists only anion exchange (IX), reverse osmosis (RO), and electrodialysis reversal (EDR)
as accepted potable water treatment methods for nitrate removal (U.S. EPA 2010). Due to the
production of high-strength brine residuals, sustainable application of these three technologies is often
limited by a lack of local residual disposal options and the challenge of increasing salt loads. The lack of
affordable and feasible nitrate treatment alternatives can force impacted utilities to remove nitratecontaminated sources from their available water supply. In many instances, this action can severely
compromise a water utility’s ability to provide an adequate supply of safe and affordable potable water.
The need for additional nitrate treatment technologies has driven the drinking water community to
begin developing alternative options to effectively remove nitrate while limiting cost and brine
production challenges. Promising treatment options include weak base anion (WBA) exchange and
improvements in strong base anion (SBA) exchange such as low brine residual technologies; biological
treatment using fluidized bed, fixed bed, and membrane biofilm (MBfR) reactors; and chemical
reduction using media such as zero valent iron (ZVI) and sulfur modified iron (SMI). A summary of the
options to address nitrate contamination of drinking water is presented in Figure S.1. In this diagram
treatment options are classified in terms of their ability to either remove nitrate to a residual waste
stream or transform nitrate to other nitrogen species through reduction.
Technical Report 6: Drinking Water Treatment for Nitrate
1
4
Figure S.1. Summary of nitrate management options.
Approach
This report includes a comprehensive literature review and case studies of specific systems across the
range of nitrate treatment alternatives. The literature review is intended to provide background
information about current and emerging potable water treatment alternatives to address nitrate
contamination. In addition to peer-reviewed literature, information found in the “grey papers” of
conference proceedings has been included to assure capture of the most recent technology
developments. For each of the major treatment technologies, subsections of the literature review detail
the following:




Design considerations including water quality, system layout, and site considerations; residuals
management and disposal; and maintenance, monitoring, and operational complexity,
cost considerations,
selected research, and
a summary of advantages and disadvantages.
4
For the purposes of this discussion, blending has been categorized as a “non-treatment” option; however, in practice,
blending is sometimes referred to as “treatment.” Treatment options throughout this report refer to treatment technologies
available for the removal or reduction of nitrate in drinking water. Blending can sometimes be used to cost-effectively address
the nitrate problem through dilution, but has been categorized separately from treatment options for simplicity.
Technical Report 6: Drinking Water Treatment for Nitrate
2
Information is summarized in tables whenever appropriate, including a summary table of selected
research studies for each of the major treatment technologies (Appendix).
A survey was conducted to collect detailed information about the application of nitrate treatment. A
subset of utilities, currently treating for nitrate and/or in design for future treatment, was included in
the survey. The survey was developed to gather information with respect to the benefits and limitations
of the various nitrate treatment technologies and was conducted via phone and in-person when
applicable. The list of utilities included in the survey was developed with the intention of covering a
range of utilities with respect to geographic location, treatment type, population size and residual
handling techniques (Table S.1). Detailed case studies have been compiled for each of the treatment
technologies where full-scale facilities have been in operation or are moving ahead with design. This
survey was conducted through collaboration with Jacobs Engineering in the completion of the
associated assessment of nitrate treatment alternatives for the American Water Works Association
(AWWA) and is complemented by a parallel survey of nitrate treatment systems in California. Details
from the initial survey are included as examples following a discussion of each of the treatment
technologies. Details of the complementary survey of California systems are included in the second half
of this report.
Technical Report 6: Drinking Water Treatment for Nitrate
3
Table S.1. Utilities included in the case studies.
Case #
Treatment Type
Location
Capacity (gpm)
Avg. Influent Nitrate
mg/L as NO3 (mg/L as N)
Ion Exchange
1
Conventional ion exchange with blending
California
400
31 – 53 (7 – 12)
2
Conventional ion exchange with blending
California
400
~45 (~10)
3
Counter Current Ion Exchange (MIEX )
Indian Hills, CO
50
53 – 71 (12 – 16)
4
Multiple vessel ion exchange
California
500 – 900
35 – 89 (8 – 20)
5
Multiple vessel ion exchange
Chino, CA
5000
40 – 200 (9 – 45)
Bakersfield, CA
120
75 – 84 (17 – 19)
Brighton, CO
4600
49 – 89 (11 – 20)
Arlington Desalter, Riverside, CA
4583
44 – 89 (10 – 20)
®
Reverse Osmosis
6
Reverse osmosis and blending
7
Reverse osmosis, exploring biological
reduction
8
Reverse osmosis and blending
Combined Reverse Osmosis and Ion Exchange
9
Reverse osmosis, ion exchange and blending
Chino Desalter I, Chino, CA
4940 (RO), 3400 (IX)
148 – 303 (33 – 68)
10
Reverse osmosis, ion exchange and blending
Chino Desalter II, Mira Loma, CA
4167 (RO), 2778 (IX)
70 – 224 (16 – 51)
Electrodialysis/Electrodialysis Reversal/Selective Electrodialysis
11
Electrodialysis Reversal (EDR)
Spain
3,260 (each, 2 systems)
~80 (~18)
12
Selective Electrodialysis (SED)
Israel
310
84 – 89 (19 – 20)
Rialto, CA
2000 – 4000
17 – 19 (~4 – 5)
Riverside, CA
1670
44 – 89 (10 – 20)
Biological Denitrification
13
Implementing fluidized bed biological
reduction
14
Implementing fixed bed biological reduction
Technical Report 6: Drinking Water Treatment for Nitrate
4
Findings
Non-Treatment Options
The focus of this assessment is the current state of nitrate treatment alternatives. However, in practice,
non-treatment options are generally considered first as they can often be more sustainable and less
costly. Non-treatment options include wellhead protection, land use management, well inactivation,
source modification, development of alternative sources (including consolidation/connection to a
nearby system), and blending. Blending was found to be the most common method to address nitrate
contamination. When a low nitrate water supply source is available, dilution of high nitrate sources to
produce water with nitrate levels below the MCL is typically more cost-effective than installing
treatment.
Treatment Options
Nitrate treatment technologies were categorized into five major types. Ion exchange (IX), reverse
osmosis (RO), and electrodialysis/electrodialysis reversal (ED/EDR) remove nitrate to a concentrated
waste stream, while biological denitrification (BD) and chemical denitrification (CD) transform nitrate to
other nitrogen species through reduction. Common concerns in the application of the removal
technologies include waste management costs and treatment interference from other water quality
parameters (e.g., hardness and sulfate). Pretreatment is often required to avoid fouling or scaling of the
resin for IX and the membranes for RO and ED/EDR. Due to the destruction of nitrate, both biological
and chemical denitrification have the potential for more sustainable treatment without brine residuals,
but also have limitations to consider. Full-scale application of these nitrate treatment options is
currently limited.
The selection of the most appropriate treatment option depends on various key factors specific to the
needs and priorities of individual water systems. A brief comparison of fundamental design
considerations, and advantages and disadvantages of these treatment options is listed in Table S.2. It is
important to note that the contents of Table S.2 are not intended to provide a comprehensive set of
criteria for treatment options. Other important criteria in determining the best treatment option, which
are site specific and cannot be broadly generalized, include capital and operations and maintenance
(O&M) costs, system size (capacity), and system footprint. Overall, there is no single treatment option
that can be considered the best method for nitrate removal across all water quality characteristics and
for all systems.
Technical Report 6: Drinking Water Treatment for Nitrate
5
Table S.2. Potable water treatment options for nitrate management (adapted from WA DOH 2005).
Full-scale Systems
Treatment Type
Common Water
Quality Design
Considerations
Pretreatment
Needs
Post-treatment
Needs
Waste/Residuals
Management
Start-up Time
Water Recovery
Ion Exchange
Reverse Osmosis
Electrodialysis
Biological Denitrification
Chemical Denitrification
Yes
Yes
Yes
Yes
No
Removal to waste stream
Sulfate, iron, manganese, total
suspended solids (TSS), metals
(e.g., arsenic), hardness,
organic matter
Removal to waste stream
Turbidity, iron, manganese,
SDI, particle size, TSS,
hardness, organic matter,
metals (e.g., arsenic)
Removal to waste stream
Turbidity, iron, manganese,
TSS, hydrogen sulfide,
hardness, metals (e.g.,
arsenic)
Biological reduction
Chemical reduction
Temperature and pH, anoxic
conditions
Temperature and pH
Pre-filter, address hardness
Pre-filter, address hardness
Pre-filter, address hardness
pH adjustment, nutrient and
substrate addition, need for
anoxic conditions
pH adjustment
pH adjustment
pH adjustment
Remineralization
pH adjustment
Remineralization
Filtration, disinfection, possible
substrate adsorption
pH adjustment, iron
removal, potential ammonia
control
Waste brine
Concentrate
Concentrate
Sludge/biosolids
Waste media, Iron sludge
Minutes
Minutes
Minutes
Minutes
Initial plant startup:
Days to weeks
After reaching steady state:
Minutes
Conventional (97%)
Low brine (Up to 99.9%)
Up to 85%
Up to 95%
Nearly 100%
Not demonstrated full-scale
No waste brine or concentrate,
nitrate reduction rather than
transfer to a waste stream, high
water recovery, and potential
for multiple contaminant
removal
Substrate addition, potentially
more complex, high monitoring
needs, possible sensitivity to
environmental conditions, risk of
nitrite formation (potential
incomplete denitrification),
post-treatment to address
turbidity standards and 4-log
virus removal (state dependent)
No waste brine or
concentrate, nitrate
reduction rather than
transfer to a waste stream,
and potential for multiple
contaminant removal
Inconsistency of nitrate
reduction, risk of nitrite
formation (potential
incomplete denitrification),
reduction to ammonia, lack
of full-scale systems, pH and
temperature dependence,
possible need for iron
removal
Advantages
Nitrate selective resins,
common application,
multiple contaminant removal
Multiple contaminant
removal, desalination (TDS
removal)
Multiple contaminant
removal, higher water
recovery
(less waste), desalination,
unaffected by silica
Disadvantages
Potential for nitrate peaking,
high chemical use (salt), brine
waste disposal, potential for
disinfection byproduct (DBP)
formation (e.g., NDMA)
Membrane fouling and
scaling, lower water recovery,
operational complexity,
energy demands, waste
disposal
Energy demands,
operational complexity,
waste disposal
Technical Report 6: Drinking Water Treatment for Nitrate
6
Ion Exchange (IX)
The most commonly used nitrate treatment method is IX. Anion exchange for nitrate removal is similar
to a water softener, with nitrate ions removed rather than hardness ions. Nitrate is removed from the
treatment stream by displacing chloride on an anion exchange resin. Subsequently, regeneration of the
resin is necessary to remove the nitrate from the resin. Regeneration is accomplished by using a highly
concentrated salt solution resulting in the displacement of nitrate by chloride. The result is a
concentrated waste brine solution high in nitrate that requires disposal. The most significant drawback
of this treatment option is the cost for disposal of waste brine, especially for inland communities. The
brine volume is largely dependent on the raw water quality and the configuration of the system.
Key factors in the consideration of IX include the pretreatment requirements to avoid resin fouling, the
potential need for nitrate selective resin, the frequency of resin replacement, the possible posttreatment requirements to address corrosion or other product water quality concerns (e.g., the
potential for NDMA formation), and the management of waste brine. If waste brine disposal options are
not limiting, IX can be the best option for low to moderate nitrate contamination and removal of
multiple contaminants (including arsenic, perchlorate, and chromium). Application of IX may not be
feasible for extremely high nitrate levels due to salt use and waste volume. Current research on brine
treatment alternatives may lead to the development of technologies capable of effectively addressing
the disposal concern; however, the costs for full-scale implementation of this are unknown at this point.
Modifications to conventional IX have emerged in recent years offering low brine alternatives with
improved efficiency. The efficiency of IX systems is dependent on the raw water characteristics. It is
important to note that there can be cases where conventional IX systems yield greater water efficiency
than a modified system that is implemented at a location with lesser water quality.
Another promising alternative to consider for the future is weak base ion exchange (WBA IX). This
emerging technology is more operationally complex than conventional IX, but may offer the advantage
of recycling waste as fertilizer.
Reverse Osmosis (RO)
As the second most common nitrate treatment alternative, RO can be feasible for both municipal and
Point-of-Use applications and can be used simultaneously for desalination and removal of nitrate and
many co-contaminants. Following pretreatment to prevent membrane fouling and scaling, water is
forced through a semi-permeable membrane under pressure such that the water passes through, while
contaminants are impeded by the membrane.
Key factors in the consideration of RO are the pretreatment requirements, the trade-off between water
recovery and power consumption, the management of waste concentrate, and the typically higher costs
relative to IX. One deciding factor favoring the selection of RO over IX for nitrate removal would be the
need to address salinity.
Technical Report 6: Drinking Water Treatment for Nitrate
7
Recent advancements in membrane technology and optimization of pre- and post-treatment have led to
increases in the efficiency of RO treatment systems. For example, the use of Ultra-Low Pressure Reverse
Osmosis (ULPRO) membranes enables lower power consumption.
Electrodialysis (ED, EDR, SED)
The use of ED in potable water treatment has increased in recent years, offering the potential for lower
residual volumes through improved water recovery, the ability to selectively remove nitrate ions, and
the minimization of chemical and energy requirements. ED works by passing an electric current through
a series of anion and cation exchange membranes that trap nitrate and other ions in a concentrated
waste stream. To minimize fouling and thus the need for chemical addition, the polarity of the system
can be reversed with electrodialysis reversal (EDR). By reversing the polarity (and the solution flow
direction) several times per hour, ions move in the opposite direction through the membranes,
minimizing buildup.
Key factors in the consideration of EDR are the pretreatment requirements, the operational complexity
of the system, the limited number of system manufacturers, the management of waste concentrate, and
the lack of full-scale installations for nitrate removal from potable water in the United States. Like RO,
EDR is commonly used for desalination and can be an alternative for nitrate treatment of high TDS
waters. In contrast to conventional RO, EDR is unaffected by silica. EDR costs are similar to RO and
evidence suggests that EDR can be the preferable option as the Silt Density Index (SDI) increases. For
very small particle sizes, robust pretreatment can be necessary for RO. It is important to note that the
EDR process does not directly filter the treatment stream through the membranes; contaminants are
transferred out of the treatment stream and trapped by the membranes. This generally minimizes
membrane fouling, decreasing pretreatment requirements in comparison to RO.
Biological Denitrification (BD)
Biological denitrification in potable water treatment is more common in Europe with recent full-scale
systems in France, Germany, Austria, Poland, Italy, and Great Britain. To date, full-scale drinking water
applications in the United States are limited to a single plant in Coyle, OK (no longer online). However,
two full-scale systems are anticipated in California in the next couple of years. Biological denitrification
relies on bacteria to transform nitrate to nitrogen gas through reduction. Substrate and nutrient
addition is necessary and post-treatment can be more intensive than for the removal processes.
Biological denitrification offers the ability to address multiple contaminants and the avoidance of costly
waste brine disposal.
Key factors in the consideration of biological denitrification are the chemical requirements, the need for
anoxic conditions, the level of operator training, the robustness of the system, and the post-treatment
requirements. State regulations are expected to vary and, until more experience with the application of
biological denitrification for potable water treatment is obtained in the United States, pilot and
demonstration requirements may be intensive. Typically, biological treatment is thought to have a
larger footprint; however, with the latest design configurations, the system footprint may be
comparable to that of RO or EDR systems.
Technical Report 6: Drinking Water Treatment for Nitrate
8
With reduction of nitrate to nitrogen gas, the lack of a problematic brine waste stream is a clear
advantage of biological treatment over the removal processes. Biological treatment has the potential to
provide a sustainable nitrate treatment option for the long term. More will be known with the
completion of the anticipated full-scale systems in California; cost estimation suggests that biological
treatment can be economically competitive with IX.
Chemical Denitrification (CD)
Chemical denitrification uses metals to transform nitrate to other nitrogen species. As an emerging
technology, no full-scale chemical denitrification systems have been installed in the United States for
nitrate treatment of potable water, and application for nitrate treatment has been strictly limited to
bench- and pilot-scale studies. A significant body of research has explored the use of zero valent iron
(ZVI) in denitrification. Several patented granular media options have also been developed including
sulfur modified iron (SMI) media, granular clay media, and powdered metal media.
Key factors in the consideration of chemical denitrification are the reliability and consistency of nitrate
reduction, the lack of full-scale installations, the type of media, and the dependence on temperature
and pH. Chemical denitrification has the potential to become a feasible full-scale nitrate treatment
alternative, with the advantage of reducing nitrate to other nitrogen species and avoiding the need to
dispose of a concentrated waste stream. However, currently this option is an emerging technology in
need of additional pilot- and full-scale testing. Due to the potential benefits, further research and
optimization of chemical denitrification systems will likely make this a competitive option in the future,
especially for multiple contaminants (e.g., arsenic and chromium).
Conclusions

Current full-scale nitrate treatment installations in the United States consist predominantly of IX
and RO. While EDR is a feasible option for nitrate removal from potable water, the application
of EDR is generally limited to waters that have high TDS or silica. The use of biological
denitrification to address nitrate contamination of drinking water is more common in Europe
than in the U.S. However, this option is emerging in the U.S. and two full-scale systems are
expected in a few years. Chemical denitrification may become a feasible nitrate treatment
option in the future; however, the lack of current full-scale implementation suggests the need
for further research, development and testing.

Brine reuse and treatment are vital to the continued reliance on IX for nitrate treatment of
potable water. The low brine technologies offer a minimal waste approach and current research
and development of brine treatment alternatives seem to be lighting the path toward future
progress.

In regions with declining water quality and insufficient water quantity, the need to address
multiple contaminants will increase in the future, suggesting the future dominance of
technologies capable of multiple contaminant removal. In this context, for any individual water
source or system, the most appropriate technology will vary with the contaminants requiring
Technical Report 6: Drinking Water Treatment for Nitrate
9
mitigation. Although complex, analysis of the optimal treatment option for pairs and groups of
contaminants will assist in the treatment design and selection. In such scenarios, the best
treatment option for nitrate may not be the most viable overall.

Currently and into the future, selection of the optimal and most cost-effective potable water
treatment options will depend not only on the specific water quality of a given water source, but
also on the priorities of a given water system. If land is limited, the typical configuration
required for biological treatment may not be feasible. If brine waste disposal options are costly
or limited, implementation of denitrification treatment or development of brine recycling and
treatment may be the most suitable option.

When deciding on nitrate treatment, the characteristics of the water system must be taken into
account as well. With consideration of economies of scale, many rural small water systems
cannot afford to install treatment. Even with financial assistance to cover capital costs, the long
term viability of a treatment system can be undermined by O&M costs that are simply not
sustainable. For such systems, treatment can become more affordable through consolidation of
multiple small water systems into larger combined water systems that can afford treatment as a
conglomerate. With a continued decline in water quality, non-treatment options alone, like
blending groundwater sources or drilling a new well, may become insufficient measures for a
water system to provide an adequate supply of safe and affordable potable water. Especially in
rural small communities, perhaps the most promising approach will be consolidation of multiple
nearby water systems and the installation of a single centralized treatment plant. Alternatively,
separate small treatment facilities can be consolidated under a single agency. For additional
discussion on the comparison of alternative water supply options and associated costs see
Technical Report 7 (Honeycutt et al. 2012).

While current cost considerations are commonly the driving force in selecting nitrate treatment,
it is essential to consider the long term implications of current industry decisions. For example,
it may be cost-effective for a particular system to utilize conventional IX currently, but future
water quality changes (e.g., increasing nitrate levels, co-contamination, high salt loading),
discharge regulations, or disposal fees may lead to an unmanageable increase in costs.
Environmental sustainability in drinking water treatment is being addressed with brine
treatment alternatives and denitrification options. It is important to approach the future of
drinking water treatment with the mindset that environmental sustainability and economic
sustainability are tightly interwoven.

Centralized treatment may not be feasible for widespread rural communities; another approach
to consider is centralized management (e.g., design, purchasing, and maintenance) to minimize
costs.

Point-of-Use (POU) and Point-of-Entry (POE) treatment equipment is an important option to
consider, especially for the provision of safe drinking water from private wells. Unless
connecting to a nearby public water system becomes an option, users relying on domestic wells
Technical Report 6: Drinking Water Treatment for Nitrate
10
have two main alternatives: drilling a new well to attain safe drinking water or installing a POU
or POE device for the treatment of contaminated water. The use of POU and POE treatment
equipment by small public water systems is currently only a temporary option in California and
reliance on these devices for the long-term would require regulation changes. While POU and
POE treatment equipment has been shown to effectively address nitrate and other
contaminants, it is important to properly maintain these devices to ensure the supply of
consistently safe drinking water.

Within the drinking water community, the options typically considered to address nitrate
contamination are IX and RO. Alternative technologies are available or emerging (EDR, BD, CD)
because, under some circumstances, they offer advantages over IX and RO. New technologies
will continue to be investigated and developed because no single option is ideal for all
situations. There is not a nitrate treatment option currently available that can affordably
address all possible scenarios. The following diagram is a rough guide for treatment technology
selection based on water quality concerns and possible priorities for a given water source or
system (Table S.3). This diagram includes generalizations and is not intended to be definitive. In
the selection of nitrate treatment technologies the unique needs of an individual water system
must be assessed by professional engineers to optimize treatment selection and design.
1
Table S.3. Comparison of major treatment types.
Concerns
IX
RO
EDR
BD
CD
Priorities
High Nitrate
Removal
High Hardness Not
a Major Concern
High TDS
Removal
Reliability
Arsenic
Removal
Training/ Ease of
operation
Radium and
Uranium
Removal
Minimize Capital
Cost
Chromium
Removal
Minimize Ongoing
O&M Cost
Perchlorate
Removal
Minimize
Footprint
IX
RO
EDR
BD
CD
Industry
Experience
Good
1

Poor
Unknown
(blank)
Ease of Waste
Management
Ion Exchange (IX), Reverse Osmosis (RO), Electrodialysis Reversal (EDR), Biological Denitrification (BD), Chemical
Denitrification (CD). This table offers a generalized comparison and is not intended to be definitive. There are
notable exceptions to the above classifications.
Technical Report 6: Drinking Water Treatment for Nitrate
11
1 Introduction
Nitrate contamination of potable water sources is becoming one of the most important water quality
concerns in California and across the United States. The maximum contaminant level (MCL), 45 mg/L as
nitrate (NO3-) (10 mg/L as nitrogen (N)), is currently being approached or exceeded in potable water
supply sources at locations throughout the United States (Nolan et al. 2002; Chen et al. 2009; U.S. EPA
N.D.). A major source of nitrate contamination is fertilizer. Application of fertilizer in excess of the
amount taken up by crops leads to leaching into the groundwater. Leakage from livestock feedlots and
waste storage also contributes to the nitrate problem (LLNL 2002). Additional sources include
wastewater treatment discharge, faulty septic systems, and various industrial applications. Due to the
typical sources, nitrate contamination is more common in rural agricultural areas. The major health
concern of nitrate exposure through drinking water is the risk of methemoglobinemia, especially in
infants and pregnant women. Due to the nature of the infant digestive system, nitrate is reduced to
nitrite which can render hemoglobin unable to carry oxygen (SWRCB 2010).
1.1 Management Options for Nitrate in Potable Water
To meet the nitrate MCL in the provision of potable water, both non-treatment and treatment options
are considered. Source management with non-treatment can sometimes provide less costly solutions
through wellhead protection, land use management, well abandonment, source modification,
development of alternative sources (including consolidation or connection to a nearby system), or
blending.5 The feasibility of non-treatment options can be limited by various factors including location,
budget, source availability, and variability of water quality (i.e., fluctuations in nitrate levels), resulting in
the need for treatment to remove or reduce nitrate.
Current treatment methods include ion exchange (IX), reverse osmosis (RO), electrodialysis/
electrodialysis reversal (ED/EDR), biological denitrification (BD), and chemical denitrification (CD). These
nitrate management options are examined in detail to assess research findings, capital and O&M costs,
typical limitations, and the latest improvements. Design and cost considerations will be addressed with
the development of guidelines for determining the most appropriate treatment option based on source
water quality and other water system characteristics.
Point-of-Entry (POE) and Point-of-Use (POU) treatment equipment should also be considered as part of
a comprehensive examination of nitrate treatment. The Safe Drinking Water Act (SDWA) [Section
1412(b)(4)(E)(ii)] (U.S. EPA 1998) identifies both POE and POU treatment units as options for compliance
technologies for small systems; California regulations governing the use of POU and POE devices for
water system compliance currently restrict their use to a temporary basis and only for systems having
particular characteristics (Section 3.7).
5
For the purposes of this discussion, blending has been categorized as a “non-treatment” option; however, in practice,
blending is sometimes referred to as “treatment.” Treatment options throughout this report refer to treatment technologies
available for the removal or reduction of nitrate in drinking water. Blending can sometimes be used to cost-effectively address
the nitrate problem through dilution, but has been categorized separately from treatment options for simplicity.
Technical Report 6: Drinking Water Treatment for Nitrate
12
Lastly, hybrid systems are explored. The combination of multiple treatment technologies, including
several developing brine treatment alternatives, can maximize the advantages of each option. The goal
of this investigation is to provide an overview of management strategies and treatment options,
highlighting the most recent advances and elucidating costs and common problems in application.
Technical Report 6: Drinking Water Treatment for Nitrate
13
2 Non-Treatment Options for Nitrate Contaminated Potable
Water
2.1 Well Abandonment, Inactivation, and Destruction
With adequate capacity from other sources, the simplest option for management of nitrate
contaminated potable water sources is well abandonment and proper destruction. However, the lack of
sufficient alternative water supplies often rules out well abandonment as an option. Based on a recent
survey conducted by the American Water Works Association (AWWA), 30.4% (17/56) of survey
participants with wells impacted by nitrate selected well abandonment as the implemented option for
addressing nitrate contamination (Weir & Roberson 2010; Weir & Roberson 2011). It is important to
determine the local requirements for safely removing a well from service. For proper abandonment,
local requirements can include covering, sealing, and plugging of the well to prevent contamination and
to avoid hazardous conditions. Inactivation or abandonment of a well differs from well destruction.
Through inactivation or temporary abandonment, the well can be brought back online in the future
(e.g., when treatment is installed). In contrast, well destruction involves the filling of a well, making it no
longer viable. The costs for proper well abandonment and destruction can be substantial and vary with
well depth, diameter, location, and local standards for well destruction. Analysis of public supply well
abandonment and destruction in the Tulare Lake Basin and Salinas Valley, as well as across California, is
included below in the Section 5.1 Well Abandonment, Destruction, and Inactivation. Additional
information on private well abandonment and destruction is provided in Technical Report 2, Section 9
(Viers et al. 2012).
2.2 Wellhead Protection and Land Use Management
While limiting current nitrate contamination of groundwater will not immediately remove the need for
treatment, over time, load reduction will minimize source water nitrate levels. Agricultural practices,
management of dairies, control of wastewater treatment plant discharge, and monitoring and
remediation of septic tank discharges can be improved to minimize nitrogen loading (for a full discussion
of source load reduction see Technical Report 3, Dzurella et al. 2012). For example, a project addressing
well head protection and land use management performed by the University of Waterloo (Rudolph
2010) successfully decreased groundwater nitrate levels within a two year travel time from 17 to 7 mg/L
total stored nitrogen. Reduced nitrogen loading was accomplished by purchasing agricultural land and
implementing Best Management Practices (BMPs).
2.3 Development of Alternative Sources and Source Modification
With adequate information about the nitrate distribution and movement in the subsurface, a new well
can potentially be developed to access higher quality source water. Due to the anthropogenic nature of
the contamination, nitrate concentration typically decreases with depth (Nolan et al. 2002). If suitable
Technical Report 6: Drinking Water Treatment for Nitrate
14
water quality exists, drilling a deeper well can remove the need for nitrate treatment. However, the
quality improvements must be balanced by a potential decrease in source capacity. Due to drilling and
pumping requirements, capital and operational costs increase with the depth to uncontaminated water.
When considering the installation of a deeper well to avoid nitrate contamination, it is important to be
aware of the risk of encountering other water quality concerns at greater depths (e.g., arsenic) (see
Section 4.2 Water Quality - Co-contaminants).
Connecting to a nearby water system that is not impacted by nitrate or to a larger system that can
afford nitrate treatment is often the best option for smaller systems. For example, since 1995, the City
of Modesto, CA, has been in charge of providing compliant water to the residents of Grayson, using an
ion exchange plant for nitrate removal (Scott 2010). Similarly, consolidation of multiple nearby small
systems can decrease the cost of treatment per customer to more reasonable levels. Additional
alternative source options include purchasing water rights, trucking in potable water, or temporarily
relying on bottled water. Reliance on hauled and/or bottled water is only an interim solution for use in
emergencies or while an effective compliance option can be implemented. Technical Report 7 provides
a comprehensive discussion of alternative water supply options and associated costs (Honeycutt et al.
2012).
Modification of impacted source wells can allow for withdrawal of water with lower nitrate levels by
limiting screened intervals to regions of better water quality. Down hole remediation requires
characterization of the water quality profile to determine the screening depth range of the higher water
quality. Specialized monitoring equipment and techniques are available that can be used without
removing pumps (BESST Inc. 2008). With water profile characterization, existing wells can be selectively
screened using a packer/plug to limit withdrawal from unwanted regions (Figure 1). The effective
application of such well modification techniques is dependent on the subsurface characteristics in the
vicinity of the well. Vertical migration of nitrate through the surrounding porous media can lead to
increasing nitrate levels in the water withdrawn from the well.
Technical Report 6: Drinking Water Treatment for Nitrate
15
Figure 1. Selective well screening using a packer/plug.
The City of Ceres, CA, is in the process of drilling new wells, in part to avoid the need for nitrate
treatment; well modification has also been implemented to avoid water with high nitrate levels
(Cannella 2009).
2.4 Blending
The dilution of a nitrate impacted source with an alternate low nitrate source can be a cost-effective
option to produce compliant water; this is known as blending and can be applied independently or with
treatment.6 Blending is a common practice for the production of compliant water, but relies on the
availability of a low nitrate source and the consistency of nitrate levels to avoid exceedances. High
nitrate groundwater can also be blended with surface water when a surface water source is available;
however, surface water treatment requirements would increase costs. One drawback of implementing
blending to address nitrate contamination is that reliance on blending can limit operational flexibility. If
the source used for dilution were compromised, then production would need to be stopped from both
wells. Water can also be trucked in for blending purposes when a low nitrate source is unavailable
locally; however, hauling water for blending purposes is a temporary solution. Based on the recent
AWWA survey, 51.8% (29/56) of respondents with nitrate impacted sources selected blending as the
option to address nitrate contamination (Weir & Roberson 2010; Weir & Roberson 2011). Likewise,
6
For the purposes of this discussion, blending has been categorized as a “non-treatment” option; however, in practice,
blending is sometimes referred to as “treatment.” Treatment options throughout this report refer to treatment technologies
available for the removal or reduction of nitrate in drinking water. Blending can sometimes be used to cost-effectively address
the nitrate problem through dilution, but has been categorized separately from treatment options for simplicity.
Technical Report 6: Drinking Water Treatment for Nitrate
16
nitrate contamination of drinking water in Germany is often addressed by blending, avoiding the costs of
treatment (Dördelmann 2009). When feasible, blending is a simple alternative to treatment that avoids
disposal concerns and the certification requirements of treatment (WA DOH 2005). However,
disadvantages include the capital investment for accessing an alternative source and monitoring
requirements to ensure consistent supply of compliant water (WA DOH 2005). Analysis of water
systems utilizing blending to address nitrate contamination in the Tulare Lake Basin and Salinas Valley,
as well as across California, is included below in the Section 5.2 Survey of Blending and Treating Systems.
Technical Report 6: Drinking Water Treatment for Nitrate
17
3 Treatment Options for Nitrate Contaminated Potable Water
IX, RO, and ED/EDR transfer nitrate ions from water to a concentrated waste stream that requires
disposal. The United States Environmental Protection Agency (U.S. EPA) lists these three processes as
accepted potable water treatment methods for nitrate removal (U.S. EPA 2010). In contrast, through
biological and chemical denitrification, nitrate is converted to reduced nitrogen species, rather than
displaced to a concentrated waste stream that requires disposal.
A survey of nitrate treatment systems was conducted to assess the current state of nitrate treatment.
The list of surveyed utilities was developed with the intention of covering a range of utilities with
respect to geographic location, treatment type, population size, and residual handling techniques (Table
1). Detailed case studies have been compiled for each of the treatment technologies where full-scale
facilities have been in operation or are moving ahead with design. This survey was conducted through
collaboration with Jacobs Engineering in the completion of the associated assessment of nitrate
treatment alternatives for AWWA and is complemented by a parallel survey of nitrate treatment
systems in California. Details from the initial survey are included as examples following a discussion of
each of the treatment technologies. Details of the complementary survey of California systems are
included in the second half of this report.
A brief comparison of fundamental design considerations, and advantages and disadvantages of the
treatment options examined herein is listed in Table 2. It is important to note that the contents of Table
2 are not intended to provide a comprehensive set of criteria for treatment options. Other important
criteria in determining the best treatment option, which are site specific and cannot be broadly
generalized, include capital and O&M costs, system size (capacity), and system footprint.
IX is the most commonly used nitrate treatment method, with full-scale systems in use throughout the
United States. Full-scale application of biological denitrification in potable water treatment is mainly
limited to Europe and chemical denitrification methods have been investigated only at the pilot-scale.
Others have provided thorough reviews of available nitrate treatment technologies (Kapoor &
Viraraghavan 1997; Soares 2000; Shrimali & Singh 2001); however, a recent comprehensive review of
the state of nitrate treatment is absent from the literature.
Technical Report 6: Drinking Water Treatment for Nitrate
18
Table 1. Utilities included in the case studies.
Case #
Treatment Type
Location
Capacity (gpm)
Avg. Influent Nitrate
mg/L as NO3 (mg/L as N)
Ion Exchange
1
Conventional ion exchange with blending
California
400
31 – 53 (7 – 12)
2
Conventional ion exchange with blending
California
400
~45 (~10)
3
Counter Current Ion Exchange (MIEX )
Indian Hills, CO
50
53 – 71 (12 – 16)
4
Multiple vessel ion exchange
California
500 – 900
35 – 89 (8 – 20)
5
Multiple vessel ion exchange
Chino, CA
5000
40 – 200 (9 – 45)
Bakersfield, CA
120
75 – 84 (17 – 19)
Brighton, CO
4600
49 – 89 (11 – 20)
Arlington Desalter, Riverside, CA
4583
44 – 89 (10 – 20)
®
Reverse Osmosis
6
Reverse osmosis and blending
7
Reverse osmosis, exploring biological
reduction
8
Reverse osmosis and blending
Combined Reverse Osmosis and Ion Exchange
9
Reverse osmosis, ion exchange and blending
Chino Desalter I, Chino, CA
4940 (RO), 3400 (IX)
148 – 303 (33 – 68)
10
Reverse osmosis, ion exchange and blending
Chino Desalter II, Mira Loma, CA
4167 (RO), 2778 (IX)
70 – 224 (16 – 51)
Electrodialysis/Electrodialysis Reversal/Selective Electrodialysis
11
Electrodialysis Reversal (EDR)
Spain
3,260 (each, 2 systems)
~80 (~18)
12
Selective Electrodialysis (SED)
Israel
310
84 – 89 (19 – 20)
Rialto, CA
2000 – 4000
17 – 19 (~4 – 5)
Riverside, CA
1670
44 – 89 (10 – 20)
Biological Denitrification
13
Implementing fluidized bed biological
reduction
14
Implementing fixed bed biological reduction
Technical Report 6: Drinking Water Treatment for Nitrate
19
Table 2. Potable water treatment options for nitrate management (adapted from WA DOH 2005).
Full-scale Systems
Treatment Type
Common Water
Quality Design
Considerations
Pretreatment
Needs
Post-treatment
Needs
Waste/Residuals
Management
Start-up Time
Water Recovery
Ion Exchange
Reverse Osmosis
Electrodialysis
Biological Denitrification
Chemical Denitrification
Yes
Yes
Yes
Yes
No
Removal to waste stream
Sulfate, iron, manganese, total
suspended solids (TSS), metals
(e.g., arsenic), hardness,
organic matter
Removal to waste stream
Turbidity, iron, manganese,
SDI, particle size, TSS,
hardness, organic matter,
metals (e.g., arsenic)
Removal to waste stream
Turbidity, iron, manganese,
TSS, hydrogen sulfide,
hardness, metals (e.g.,
arsenic)
Biological reduction
Chemical reduction
Temperature and pH, anoxic
conditions
Temperature and pH
Pre-filter, address hardness
Pre-filter, address hardness
Pre-filter, address hardness
pH adjustment, nutrient and
substrate addition, need for
anoxic conditions
pH adjustment
pH adjustment
pH adjustment
Remineralization
pH adjustment
Remineralization
Filtration, disinfection, possible
substrate adsorption
pH adjustment, iron
removal, potential ammonia
control
Waste brine
Concentrate
Concentrate
Sludge/biosolids
Waste media, Iron sludge
Minutes
Minutes
Minutes
Minutes
Initial plant startup:
Days to weeks
After reaching steady state:
Minutes
Conventional (97%)
Low brine (Up to 99.9%)
Up to 85%
Up to 95%
Nearly 100%
Not demonstrated full-scale
No waste brine or concentrate,
nitrate reduction rather than
transfer to a waste stream, high
water recovery, and potential
for multiple contaminant
removal
Substrate addition, potentially
more complex, high monitoring
needs, possible sensitivity to
environmental conditions, risk of
nitrite formation (potential
incomplete denitrification),
post-treatment to address
turbidity standards and 4-log
virus removal (state dependent)
No waste brine or
concentrate, nitrate
reduction rather than
transfer to a waste stream,
and potential for multiple
contaminant removal
Inconsistency of nitrate
reduction, risk of nitrite
formation (potential
incomplete denitrification),
reduction to ammonia, lack
of full-scale systems, pH and
temperature dependence,
possible need for iron
removal
Advantages
Nitrate selective resins,
common application,
multiple contaminant removal
Multiple contaminant
removal, desalination (TDS
removal)
Multiple contaminant
removal, higher water
recovery
(less waste), desalination,
unaffected by silica
Disadvantages
Potential for nitrate peaking,
high chemical use (salt), brine
waste disposal, potential for
disinfection byproduct (DBP)
formation (e.g., NDMA)
Membrane fouling and
scaling, lower water recovery,
operational complexity,
energy demands, waste
disposal
Energy demands,
operational complexity,
waste disposal
Technical Report 6: Drinking Water Treatment for Nitrate
20
3.1 Ion Exchange (IX)
As the most commonly used method for the removal of nitrate in potable water treatment, IX has been
widely researched, with numerous full-scale installations in operation. With the potential for multiple
contaminant removal, IX can also be used to address other water quality concerns including arsenic,
perchlorate, selenium, chromium (total and chromium-6), and uranium (AWWA 1990; Boodoo 2004).
Selected IX installations used for nitrate treatment in the United States are listed in Table 3.
Table 3. Selection of full-scale ion exchange installations for nitrate removal.
Year
Installed
Influent nitrate
(mg/L as NO3 )
Capacity
(MGD)
Reference
Ellsworth, MN
1994
-
0.047
MN Dept. of Ag. (N.D.)
Clear Lake, MN
Adrian, MN
1995
1998
-
0.047
0.129
MN Dept. of Ag. (N.D.)
MN Dept. of Ag. (N.D.)
Edgerton, MN
2002
-
0.137
MN Dept. of Ag. (N.D.)
McCook, NE
2006
Up to 125
6.8
Contaminant Removal News (2007)
1983
60
1
Guter (1995), See also Guter (1982)
1987
64
1
Guter (1995), See also Guter (1982)
1987
70 – 100
2.7
Guter (1995)
-
80 – 130
2.3
Guter (1995)
1992
Up to 55
10
2010
Spiked up to 177
10
2009
53 – 71
0.072 (design)
Des Moines Water Works, Rash (1992)
Meyer et al. (2010), See also Clifford et
al. (1987)
See Case Study
Locations
McFarland, CA,
Well 2
McFarland, CA,
Well 4
La Crescenta, CA
Grover City, CA,
3 wells
Des Moines, IA
Glendale, AZ: fullscale pilot
Indian Hills, CO
Due to its common application, the investigation of IX for the removal of nitrate is prevalent in the
literature (Yoon et al. 2001; Chabani et al. 2006; Samatya et al. 2006; Clifford 2007; Meyer et al. 2010;
Clifford et al. 2010). Kapoor & Viraraghavan (1997) provide an extensive review of IX research up to
1997. Modifications of conventional IX have led to the emergence of more efficient IX processes
including multiple vessel configurations, counter current configurations, the use of specialized resins,
improved hydraulics, and weak base anion exchange (WBA IX).
3.1.1 Conventional Ion Exchange
Conventional IX utilizes a strong base anion (SBA) exchange resin. In accordance with Figure 2, raw
water passes through pretreatment to remove suspended solids and to address other constituents
capable of fouling the resin. The nitrate laden treatment stream then enters the ion exchange vessel.
Upon contacting the resin, nitrate displaces chloride at surface sites, removing nitrate from the water.
Technical Report 6: Drinking Water Treatment for Nitrate
21
Figure 2. Conventional ion exchange schematic.
This technique is similar to a water softener, which replaces the divalent cations of hard water (Mg2+ and
Ca2+) with a monovalent cation (Na+). Eqn. 1 depicts the transfer of ions, with R as the resin surface site.
Leaving nitrate behind, treated water exits the ion exchange vessel and passes on to post-treatment for
stabilization and disinfection.
R-Cl + NO3-  R-NO3 + Cl-
(Eqn. 1)
To prevent nitrate breakthrough, regeneration is necessary when the resin is exhausted of chloride ions
(chloride has been displaced at the majority of surface sites). The media is backwashed with a high salt
solution (0.5 – 3 M, Clifford 2007) to reverse the process, resulting in a brine waste stream high in
nitrate and other concentrated ions (Eqn. 2).
R-NO3 + Cl-  R-Cl + NO3-
(Eqn. 2)
The relative affinity of common anions for conventional anion exchange resin is SO42- > NO3- > Cl- > HCO3(Bae et al. 2002; Clifford et al. 2010). If generic resins are not regenerated soon enough, sulfate
displacement of nitrate in the resin can lead to nitrate release from the resin to the treatment stream
(Eqn. 3). This is known as nitrate dumping, nitrate peaking, or chromatographic peaking and is further
discussed below.
2R- NO3 + SO4-2  R2-SO4 + 2NO3-
Technical Report 6: Drinking Water Treatment for Nitrate
(Eqn. 3)
22
Due to the stronger affinity of the sulfate ion for generic anion exchange resins, nitrate selective resins
have been developed for which the order of affinity is NO3- > SO42- > Cl- > HCO3- (Guter 1982; Guter
1995). Important factors in resin selection are the exchange capacity7 and selectivity coefficient8 of the
resin and the rate of ion transfer (kinetics9).
Detailed case studies of conventional IX plants are included in Section 3.1.7 Ion Exchange - Case Studies.
3.1.2 Ion Exchange - Design Considerations
Various tools are available to assist with IX system design including Dow’s CADIX (Computer Assisted
Design for Ion Exchange) (Dow 2010b) and Lenntech’s Ion Exchange calculator (Lenntech 2009b.) Table
4 summarizes key design considerations in the application of conventional IX to nitrate removal from
potable water.
7
Exchange capacity: The exchange capacity is a measure of how many ions the resin can capture per unit volume.
8
Selectivity coefficient: The selectivity coefficient of a resin refers to the relative affinity of resin surface sites for a particular
ion, in this case nitrate.
9
Kinetics: The term kinetics refers to the rate of a reaction. The rate that nitrate displaces chloride on the resin is important for
efficient treatment and can be affected by competing ions.
Technical Report 6: Drinking Water Treatment for Nitrate
23
Table 4. Summary of design considerations for conventional IX.

Resin Selection


Pretreatment
Post-Treatment
Chemical Usage
O&M
System
Components
Waste
Management
and Disposal




















Limitations



Generic SBA resins for maximum exchange capacity (for low sulfate)
o Less expensive than nitrate selective resins
o Less frequent regeneration due to higher capacity (in the absence of cocontaminants)
o Nitrate dumping potential
Nitrate selective resins to avoid nitrate dumping (for high sulfate)
o More expensive than generic resins
o Longer bed life
o More nitrate removed per unit of waste brine
Filtration to remove iron, manganese, TSS, and organic matter to prevent resin
fouling
Water softening (anti-scalant, acid, or water softener) to prevent scaling
10
Dechlorination to prevent resin oxidation
11
Chloride : alkalinity ratio and dezincification
12
Chloride : sulfate ratio and galvanic corrosion
Potential pH adjustment and restoration of buffering capacity to avoid corrosion
pH adjustment (caustic soda or soda ash)
Regenerant brine, salt consumption
Frequency of regeneration depends on water quality and resin type
Fresh brine preparation and waste disposal
Resin loss and replacement: 3 – 8 year lifetime (WA DOH 2005; Dow 2010c)
Continuous or frequent monitoring of nitrate levels
Backwashing to dislodge solids
Fixed bed versus continuous regeneration
Key system configuration parameters are system flow rate, bed swelling, bed depth,
backwash flow rate, and rinse requirements
o Vessels in parallel or in-series
o Co-current or counter-current regeneration
Significant cost of waste brine disposal is of greatest concern for inland systems
Close proximity to coastal waters is beneficial for brine disposal
Management options can include sewer or septic system, drying beds, trucking offsite, coastal pipeline, deep well injection, and advanced treatment
Disposal options can be limited by waste brine water quality (e.g., volume, salinity,
metals, and radionuclides)
Optimization of recycling and treatment of waste brine is desirable
Need to manage resin fouling
o Hardness, iron, manganese, suspended solids, organic matter, and chlorine
Competing ions (especially sulfate)
Disposal of waste brine
Possible role of resin residuals in DBP formation
10
The resin can be degraded by oxidation; the functional amine groups on the resin surface are susceptible to oxidation which
can lead to diminished capacity (Dow 2010d).
11
As nitrate and other anions displace chloride on the resin, chloride is released to the product water, leading to the potential
for taste issues and dezincification (Kapoor & Viraraghavan 1997). Dezincification refers to the ability of product water to
dissolve zinc from brass and is dependent on the ratio of chloride to alkalinity (> 0.5 can be problematic). By restoring
alkalinity, the dezincification potential can be minimized.
12
Galvanic corrosion can result in the release of lead from brass and galvanized solder-copper connections and is associated
with a high ratio of chloride to sulfate (> 0.58 can be problematic) (Edwards et al. 1999; Edwards & Triantafyllidou 2007).
Technical Report 6: Drinking Water Treatment for Nitrate
24
Water Quality
Raw water quality is a key factor in the efficiency of an IX system, impacting resin selection,
pretreatment and post-treatment needs, regeneration efficiency, chemical usage, and waste disposal.
Important water quality parameters include alkalinity, hardness, iron, manganese, and potential
competing ions (predominantly sulfate).
Selection of the appropriate resin for a given system depends directly on source water quality. In the
presence of high levels of co-contaminants, nitrate selective resins may be necessary rather than generic
resins. Both strong base anion exchange (SBA) resin and weak base anion exchange (WBA) resin can be
suitable for nitrate removal from potable water. The latter will be addressed separately. The two
standard types of SBA resins deviate in their functional groups. Anion exchange is dependent on the
trimethylamine groups of the SBA Type I resin and the dimethylethanolamine groups of the SBA Type II
resin (Helfferich 1995).
Nitrate selective resin was invented in the early 1980’s by Gerald Guter (Guter 1982, see related patent:
Guter 1983). Clifford & Weber (1978 and 1983) contributed to the development and characterization of
these resins with their research on resin selectivity (Clifford et al. 2010). Nitrate selective resins rely on
different functional groups than Type I and Type II SBA resins. Nitrate selectivity is attributed to the
increased hydrophobicity and site spacing of exchange sites due to the triethyl, tripropyl, and tributyl
functional groups of nitrate selective resin (Clifford & Weber 1978; Guter 1982; Clifford et al. 2010). The
use of nitrate selective resin avoids the problem of nitrate peaking (i.e., nitrate dumping or
chromatographic peaking), typically caused by the greater affinity of generic resins for sulfate.
It is important to note the distinction between nitrate peaking and nitrate breakthrough. As nitrate
displaces chloride on the resin, the nitrate capacity of the resin is gradually exhausted leading to
increasing effluent nitrate levels until influent levels are reached. This is known as breakthrough and
can occur regardless of resin type. Nitrate peaking can also occur upon exhaustion of the resin capacity
for nitrate. However, with nitrate peaking, the nitrate on the resin is displaced by sulfate, thereby
increasing the effluent nitrate concentration to levels above that of the raw water (Clifford et al. 2010).
The peak in nitrate concentration is due to the combination of the influent nitrate ions and the nitrate
ions that are coming off of the resin via sulfate displacement.
Under low sulfate conditions, the use of generic SBA resins is preferred, due to their larger exchange
capacity. As the ratio of sulfate to nitrate increases, the use of nitrate selective resins avoids possible
nitrate peaking, minimizing the risk of MCL exceedance and the need for more frequent regeneration.
However, with the highest nitrate selectivity, regeneration efficiency can decrease, increasing chemical
use. With a stronger affinity for nitrate, the removal of nitrate from the resin in regeneration is more
difficult because nitrate is more strongly bound (Dow 2010c). Nitrate selective resins are more costly
than the generic option (Water Quality Products 2003), but under appropriate conditions the use of
regenerant can be minimized and bed life can be increased significantly with their use. Different system
configurations have been implemented as an alternative to the use of nitrate selective resins to address
the problem of co-contaminants and the risk of nitrate peaking (Clifford et al. 2010), for more
Technical Report 6: Drinking Water Treatment for Nitrate
25
information, see System Layout and Site Considerations, below. In the consideration of IX for multiple
contaminant removal, the selection of the most appropriate resin depends in part on the type and
concentration of co-contaminants. Modeling and column or pilot testing is important to determine
appropriate design parameters and to design treatment based on a full life cycle analysis of costs.
Upstream of the IX vessels, pretreatment of the source water may be necessary to avoid resin fouling
(Water Quality Products 2003; WA DOH 2005). Potential constituents of concern include organic
matter, turbidity, total suspended solids (TSS), sand and metals, primarily iron and manganese (Kapoor
& Viraraghavan 1997; Water Quality Products 2003; WA DOH 2005). Pre-filtration is typically used to
remove these constituents; however, additional pretreatment methods may be used. For example,
coagulation/flocculation and filtration may be necessary for surface waters. Pretreatment may be
needed for waters with a total concentration of metals (e.g., iron and manganese) above 0.1 mg/L (Ten
States Standards 2007). Hard, alkaline water can lead to resin scaling, due to calcium and magnesium
accumulation; pH adjustment or water softening can be used to prevent resin scaling (Water Quality
Products 2003). Created by Wolfgang Holl, the carbon dioxide regeneration of ion exchange (CARIX)
process combines anion and cation exchange (Holl 1995). The CARIX process enables simultaneous
removal of cations (for hardness reduction) and anions through the combination of a weak acid cation
exchanger and a strong base anion exchanger.
Resin exposure to disinfectants (chlorine and chloramines) should be avoided to prevent resin oxidation
and the possible release of disinfection byproducts, specifically nitrosamines (Kemper et al. 2009).
Disinfection byproducts (DBPs) are potentially cancer-causing compounds that can be formed through a
reaction of disinfection chemicals like chlorine and chloramines with organic matter. Due to the amine
functional groups of anion exchange resins, “these resins may serve as precursors for nitrogenous
disinfection byproducts, such as nitrosamines, nitramines, and halonitromethanes” (Kemper et al. 2009,
p. 466). Recent research suggests that the risk of DBP formation is higher with the use of new resin;
however, precursors can be a problem with downstream chloramine use or with upstream disinfection
(see Kemper et al. 2009 in Table A.1 of the Appendix). Magnetic ion exchange resin is an exception as its
primary purpose is to remove organic carbon and limit DBP formation (Boyer & Singer 2006) (see the
MIEX® process in Section 3.1.7 Ion Exchange - Case Studies).
IX can reduce alkalinity and pH due to removal of bicarbonate. To prevent corrosion in downstream
pipes, the product water pH and buffering capacity may need to be increased.13 Soda ash can be added
to the regenerant brine to load a portion of the resin sites with bicarbonate rather than chloride. This
can restore some alkalinity to the water as bicarbonate is released from the resin when displaced by
nitrate and other anions in the treatment stream (Water Quality Products 2003). To minimize the need
for caustic addition in post-treatment, an upstream atmospheric degasifier for carbon dioxide removal
can be added during pretreatment (Dow 2010).
13
It is important to note the relationship between alkalinity and pH. Alkalinity is a measure of buffering capacity or the
resistance to changes in pH. Demineralized water or water with a low buffering capacity will be susceptible to more dramatic
pH changes and is considered unstable. The pH of acidic product water should be adjusted and the buffering capacity of
demineralized product water should be restored to avoid corrosion downstream and the potential for lead and copper
challenges.
Technical Report 6: Drinking Water Treatment for Nitrate
26
As nitrate and other anions displace chloride on the resin, chloride is released to the product water,
leading to the potential for taste issues, dezincification, and galvanic corrosion. Dezincification refers to
the ability of product water to dissolve zinc from brass and is dependent on the ratio of chloride to
alkalinity (as CaCO3)(> 0.5 can be problematic, according to Kapoor & Viraraghavan (1997)). By restoring
alkalinity, the dezincification potential can be minimized. Galvanic corrosion can result in the release of
lead from brass and galvanized solder-copper connections and is associated with a high ratio of chloride
to sulfate (> 0.58 can be problematic) (Edwards et al. 1999; Edwards & Triantafyllidou 2007). It is
important to consider the potential downstream impact of subtle water quality changes caused by
treatment.
System Layout and Site Considerations
The IX system can be operated using a fixed bed or as a continuous system. Details of modifications to
conventional fixed bed systems are provided below. Key parameters in vessel sizing and system
configuration are system flow rate, bed swelling, bed depth, backwash flow rate, and rinse requirements
(Dow 2010). Regeneration can be designed in a co-current or counter-current configuration. Vessels
can be operated in parallel or in-series for redundancy, to maximize removal efficiency per regeneration
cycle, to address nitrate peaking and to consistently produce water with limited variation in water
quality parameters (Clifford et al. 2010).
Residuals Management and Disposal
Management of waste brine can be costly. Options include discharge to a sewer or septic system, waste
volume reduction using drying beds, trucking to an off-site approved disposal location, ocean discharge
through a coastal pipeline, deep well injection, and advanced treatment. Water quality characteristics
of the waste brine (e.g., volume, salinity, metals, and radionuclides) can affect the feasibility and costs of
disposal options. Proximity and access to coastal waters can be a significant factor in determining the
burden of brine disposal. Generally, disposal is of greatest concern to inland communities. Although
other removal technologies (RO and ED) also require concentrate disposal, this is an issue of particular
concern with IX. Because IX requires the addition of salt for resin regeneration, the waste stream
consists of not only the nitrate and other ions that have been removed from the water, but also the
spent brine solution used in regeneration. The high cost of nitrate laden brine disposal has led to
research into optimization of recycling and treatment of this waste stream. Partial regeneration and
reuse of treated brine for multiple regeneration cycles can minimize the volume of waste while
maximizing regeneration efficiency (Clifford 2007; Clifford et al. 2010). Application of IX systems
coupled with biological, chemical, or catalytic denitrification enables removal of nitrate from waste
brine, with reduction to nitrogen gas. The electrochemical destruction of nitrate in waste brine is also
being explored. Several combined configurations of interest are discussed below in Section 3.6 Brine
Treatment Alternatives and Hybrid Treatment Systems.
Technical Report 6: Drinking Water Treatment for Nitrate
27
Maintenance, Monitoring, and Operational Complexity
Regeneration frequency will depend on pretreatment measures, water quality, and the type of resin
used (WA DOH 2005). The typical amount of brine waste compared to water produced can range from
~3.0% for conventional systems (Clifford 2007) to ~0.5% for low brine systems (Calgon Carbon
Corporation 2007, discussed below). A constant supply of brine must be available for resin regeneration
and waste brine requires appropriate storage and disposal. Resin loss can be controlled by adjusting the
backwash flow rate and adding screens (Keller 2000). Resin life will also depend on water quality and
pretreatment measures; resin replacement may be required after 3 – 8 years (WA DOH 2005; Dow
2010c). To ensure the production of compliant water, continuous or frequent monitoring of nitrate
levels is necessary. In addition to resin regeneration, backwashing is used to dislodge solids and “resin
fines” (Dow 2010). In comparison with alternative treatment options, IX requires limited O&M with high
feasibility of automation and low operational complexity.
3.1.3 Ion Exchange - Cost Considerations
For optimal operation of an IX system, the fundamental objective is to maximize regeneration efficiency,
while meeting necessary potable water guidelines. Factors affecting system cost include facility size
(flow rate), source water quality (including nitrate concentration), environmental factors (temperature),
and target effluent nitrate concentration. Disposal of waste brine is commonly a significant portion of
O&M costs.
Capital costs for IX include land, housing, piping, storage tanks, O&M equipment, vessels, resin,
preliminary testing (pilot studies), permits, and training. O&M costs include resin replacement (due to
loss or degradation), resin disposal, brine disposal or treatment, chemical use (salt, anti-scalant, pH
adjustment), repair and maintenance, power, and labor.
Published cost information from existing IX installations is listed in Table 5. Costs have been adjusted to
2010 dollars, unless indicated otherwise. Costs can be difficult to assess due to inconsistencies in how
cost information is reported. Comparison of IX costs is not always valid due to differences in influent
water quality parameters, system size, waste management options, and system configuration.
Published costs do not always include comparable information. It would be inappropriate to compare
the O&M costs of a facility that excludes disposal costs with others that include this information. The
listed cost information is provided as an approximate range of costs for specific facilities. Costs for
implementing IX may be very different from those listed here. A thorough cost analysis of design
parameters for specific locations would be required for accurate cost estimation. The information
gathered through the questionnaire includes detailed costs associated with the unique case studies
included in this analysis. A detailed discussion of treatment costs is included below in Section 6
Treatment Cost Analysis.
Technical Report 6: Drinking Water Treatment for Nitrate
28
Table 5. Selected published costs* of ion exchange systems for nitrate removal.
System Flow**
< 0.5 MGD
0.5 – 5 MGD
5+ MGD
Annualized Capital Cost ($/1000 gal)
0.37 – 1.21 [1]
0.28 – 0.94 [2, 3]
0.28 – 0.61 [3, 4, 5]
O&M Cost ($/1000 gal)
0.60 – 4.65 [1]
0.46 – 1.25 [2, 3]
0.37 – 0.87 [3, 4, 5]
Total Annualized Cost ($/1000 gal)
0.97 – 5.71 [1]
0.74 – 2.19 [2, 3]
0.65 – 1.44 [3, 4, 5]
*Costs have been adjusted to 2010 dollars with 7% interest over 20 years, unless indicated otherwise (below).
**When available, costs are based on actual system flow rather than design capacity.
[1] Minnesota Department of Agriculture (N.D.), not adjusted to 2010 dollars, 20 year amortization without
interest. [2] Guter (1995). [3] Conlon et al. (1995). [4] Meyer et al. (2010). [5] Drewry (2010).
3.1.4 Ion Exchange - Selected Research
A large body of research has focused on IX. Table A.1 of the Appendix is a list of recent studies relevant
to nitrate removal from potable water. Given the many years of successful full-scale operating
experience with IX, current applied research is focused on brine recycling efficiency, the optimization of
waste management, and improvements in resin capacity and selectivity, to improve efficiency and
reduce costs.
3.1.5 Ion Exchange - Summary of Advantages and Disadvantages
A summary of advantages and disadvantages of IX in comparison with other treatment options is listed
in Table A.6 of the Appendix. Significant advantages of IX include years of industry experience, multiple
contaminant removal, selective nitrate removal, financial feasibility, use in small and large systems, and
the ability to automate. Disadvantages include the costly disposal of waste brine, the potential for
nitrate dumping and resin fouling, the possible need for pH adjustment, the potential for hazardous
waste generation (i.e., brine with traces of co-contaminants like arsenic and chromium), and the
possible role of resin residuals in DBP formation (Kemper et al. 2009).
3.1.6 Modifications to Conventional Ion Exchange
Modifications of conventional IX have led to the emergence of low-brine IX processes including
magnetic ion exchange (MIEX®), ion exchange separation (ISEP®), Envirogen (formerly Basin Water)
systems, and weak base ion exchange (WBA IX). Despite their potential advantages, it is important to
note that proprietary technologies may have inherent disadvantages, such as a lack of flexibility to use
better technology when it becomes available, vulnerability if the manufacturer goes out of business or
discontinues supporting the product, and a lack of competition to keep O&M costs down.
Counter Current Flow with Specialized Resin
Magnetic ion exchange technology (MIEX®), developed by Orica Watercare, offers a low brine alternative
to conventional IX, using a unique SBA Type I resin. The MIEX® process (Figure 3) differs from
Technical Report 6: Drinking Water Treatment for Nitrate
29
conventional IX in that the resin is fluidized in a contactor with spent resin removed from the contactor
for regeneration outside of the process water stream and then returned to the contactor. This is in
contrast to conventional IX, where the resin is stationary. Unlike conventional IX, the MIEX® fluidized
bed process is tolerant of suspended solids and low levels of oxidants.
Figure 3. Process flow diagram for counter current MIEX® process. (Source: reprinted with permission, Orica
Watercare 2008b.)
The minimization of waste brine is accomplished through frequent batch regeneration. The magnetized
resin encourages agglomeration of loaded resin particles, resulting in faster settling. Loaded resin is
removed from the bottom of the IX vessel and is passed to regeneration, while regenerated resin is
added at the top of the IX vessel. This configuration removes the risk of nitrate peaking because clean
resin, added at the end point of the system, captures any displaced nitrate, while competing ions, such
as sulfate can be removed early on in the resin vessel. The MIEX® process has been proven to effectively
address various water quality concerns including nitrate, organic carbon, arsenic, chromium-6 and
perchlorate (Seidel et al. 2004; Humbert et al. 2005; Boyer & Singer 2006; and Watercare 2008).
A detailed case study of a MIEX® treatment plant in Indian Hills, CO is included in Section 3.1.7 Ion
Exchange - Case Studies.
Technical Report 6: Drinking Water Treatment for Nitrate
30
Improved Hydraulics and Nitrate Selective Resins
The Layne Christensen Company and Rohm and Haas offer their Advanced Amberpack® system which
utilizes nitrate selective resins and their patented Fractal Distribution Technology to increase the treated
water volume and decrease the waste brine. Nitrate selective resins have a greater affinity for nitrate
than non-selective resins, resulting in an improvement in removal efficiency, especially in waters where
the sulfate to nitrate ratio is greater than one.
The distributor system is designed to provide uniform flow through the ion exchange vessels in both
treatment and regeneration modes. As a result of the uniform flow, the exchange capacity of the resin
can be maximized while the brine and rinse values can be minimized, thus increasing the water
efficiency of the system (Rohm and Haas Company 2007).
Multiple Vessel Carousel Configuration
Calgon Carbon’s Continuous Ion Exchange Separation System (ISEP® System) utilizes a carousel
configuration. This configuration has the potential to avoid downtime for regeneration, minimize the
amount of resin needed, and maximize regeneration efficiency. Illustrated in Figure 4, multiple resin
vessels are rotated from active treatment to resin regeneration and rinsing and back to active
treatment. The vessels rotate in the opposite direction of the water movement (Figure 5). The countercurrent and counter-flow system can provide consistent product water, operating uninterrupted with
up-flow regeneration and down-flow treatment. This configuration results in four zones within the
system (Calgon Carbon Corporation ISEP® for Nitrate Removal Brochure 2003). In the Adsorption Zone,
the feed stream is passed through 14 ports in parallel for single pass flow. Nitrate and other anions are
removed from the feed water as they transfer to the resin. In the Displacement Zone, softened water is
used to displace the hard feed water to prevent scale build-up in the regeneration zone. In the
Regeneration Zone, a combination of brine and rinse is directed through the beds for a true countercurrent regeneration to maximize the regeneration efficiency. In the Rinse Zone, a small amount of
softened feed water is used to prevent any of the salt from the regeneration zone from reaching the
product water.
A detailed case study of an ISEP® treatment plant in Chino, CA is included in Section 3.1.7 Ion Exchange Case Studies
.
Technical Report 6: Drinking Water Treatment for Nitrate
31
Figure 4. Vessel rotation in Calgon Carbon countercurrent ISEP® system. (Source: Calgon Carbon Corporation 2003.)
Figure 5. Example of flow through the ISEP® system. (Source: Calgon Carbon Corporation 2003.)
Technical Report 6: Drinking Water Treatment for Nitrate
32
Multiple Vessel Staggered Configuration
Envirogen Technologies, Inc. offers proprietary ion exchange (IX) systems using multiple beds operated
in a staggered design (Figure 6). Such a configuration has the potential to maximize resin capacity and
minimize waste and chemical use.
Figure 6. Example of an Envirogen multiple bed proprietary anion exchange system. (Source: reprinted with
permission, Envirogen 2009.)
Envirogen’s low brine IX system has been successfully implemented for nitrate and uranium removal in
San Bernardino County, CA (Envirogen 2010). Delivering 2 MGD with nitrate levels reduced from 50 – 60
mg/L as nitrate (11 – 14 mg/L as N) to 35 mg/L as nitrate (8 mg/L as N) and a system footprint of 50’ X
50’, the installation resulted in recovery of a well that had been previously decommissioned. Envirogen
is contracted to handle all operation and maintenance, including waste disposal.
In Yucca Valley, CA, nitrate treatment was required due to over pumping and the resulting intrusion of
septic system contaminated waters. An Envirogen IX system was installed to provide 2.8 MGD. With
treatment, nitrate concentrations are decreased from 58 mg/L as nitrate (13 mg/L as N) to 20 mg/L as
nitrate (4.5 mg/L as N) with 50% blending and a 0.3% waste rate (0.15% net) (Envirogen 2002).
A detailed case study of an Envirogen low-brine IX treatment plant in California is included in Section
3.1.7 Ion Exchange - Case Studies.
Technical Report 6: Drinking Water Treatment for Nitrate
33
Weak Base Anion Exchange (WBA IX)
Weak base anion exchange (WBA IX), an emerging technology, can be an effective option for nitrate
removal from potable water. Highly pH dependent, nitrate removal using WBA IX is governed by Eqn. 5
(Applied Research Associates N.D.). While SBA IX resin can remove nitrate by splitting nitrate salts, WBA
IX resin removes strong acids (Remco Engineering N.D.). First, acid addition protonates the WBA resin
(Eqn. 4). Next, the positively charged resin sites remove anions, like nitrate, from the treatment stream
(Eqn. 5).
R-NH2 + H+  R-NH3+
(Eqn. 4)
R-NH3+ + NO3-  R-NH3-NO3
(Eqn. 5)
Resin regeneration occurs by neutralizing the resin, in accordance with Eqn. 6. Rather than the high salt
solution used to regenerate SBA resins, weak bases are used to neutralize the WBA resin.
R-NH3-NO3 + Na+OH-  R-NH2 + HOH + Na+NO3-
(Eqn. 6)
As discussed in previous sections, the use of SBA IX resin results in a high-nitrate brine waste stream.
Due to the high salt content, the nitrate in the waste stream generally cannot be beneficially reused.
However, with the use of alternative weak bases for regeneration (Eqns. 7 and 8), the waste stream
does not have a high salt content and could potentially be recycled as fertilizer (NH4NO3 and Ca(NO3)2)
(Clifford 2007).
R3N-HNO3 + NH4OH  R3N-HOH + NH4NO3
(Eqn. 7)
2 R3N-HNO3 + Ca(OH)2  2R3N-HOH + Ca(NO3)2
(Eqn. 8)
The use of WBA resins is more operationally complex than the use of SBA resins. Chemical use includes
acids and bases, the system is susceptible to corrosion, and pH adjustments are more significant.
Adjustment of influent pH to between 3 and 6 is necessary, with subsequent product water pH
adjustment as well (Clifford 2007). WBA resins can also be more sensitive to temperature, with one
resin having a maximum operating level of 95oC (Dow 2010), but this should not impact their use with
municipal drinking water treatment. Regeneration of WBA resin is more efficient than that of the SBA
resin of conventional IX; regenerant waste volumes are minimized and waste products can sometimes
be recycled as fertilizer (Clifford 2007 and ARA & Purolite N.D.a).
Weak Base Ion Exchange for Nitrate, or the “WIN” Process, was developed by Applied Research
Associates, Inc. (ARA) and The Purolite Company (ARA & Purolite N.D.b) as a treatment option that can
be less costly and more efficient, with significantly lower waste volumes, than conventional SBA IX
(Figure 7).
Technical Report 6: Drinking Water Treatment for Nitrate
34
Figure 7. Process schematic of weak base ion exchange for nitrate ("WIN" process). (Source: reprinted with
permission, ARA & Purolite N.D.b.)
As an emerging technology, available information is limited to that provided by the manufacturers. The
process consists of a pretreatment step to decrease pH, followed by ion exchange vessels in series, and
post-treatment to increase pH. The manufacturer states, “The volume of nitrate-containing effluent
from the WIN process is typically less than 0.2% of the treated water and, in some cases, may be land
applied as fertilizer” (ARA & Purolite N.D.b). As discussed above, the use of SBA IX resin results in a highnitrate brine waste stream. Due to the high salt content, the nitrate in the waste stream generally
cannot be beneficially reused. However, with the use of alternative weak bases for regeneration, the
waste stream does not have a high salt content and could potentially be recycled as fertilizer.
3.1.7 Ion Exchange - Case Studies
Conventional Ion Exchange - Case Studies
The following case studies provide detailed information on the design and operation of full-scale
conventional IX treatment plants for nitrate removal. Conventional IX is also used by the Chino Basin
Desalter Authority in combination with RO. Detailed case studies for the Chino Desalter are listed
separately in the RO case study section.
Technical Report 6: Drinking Water Treatment for Nitrate
35
System Location: California
System Type: Community Water System
CASE #1
Treatment Type: Conventional Ion Exchange
Startup Date: 2007
System Description
Treatment Type
System Capacity
Raw Water Nitrate
Ion Exchange and Blending
400 gpm
31 – 53 mg/L as nitrate
7 – 12 mg/L as N
A California utility is responsible for a system that
has two groundwater supplies, one of which has
nitrate at levels that exceed the MCL. The
impacted well has a production capacity of 400
gpm and historical nitrate concentrations ranging from 31 mg/L to 53 mg/L of nitrate as NO 3 (7 – 12 mg/L as N).
The utility has implemented a blending program and installed a conventional IX treatment system in 2007 for
nitrate control and treatment.
The nitrate impacted sources also have arsenic levels above the MCL of 10 ug/L, which influenced the decision to
install IX. IX can simultaneously remove nitrate and arsenic. The treatment system is comprised of three pressure
vessels. Two vessels contain Purolite A300E for arsenic removal and the third vessel contains the nitrate selective
Purolite A520E resin. The system was originally installed in 2007 and was further modified in 2009. The system is
designed to decrease nitrate levels to less than 22 mg/L as nitrate (5 mg/L as N) prior to blending. The maximum
distribution system water goal for nitrate is 35 mg/L as nitrate (8 mg/L as N). To assure the system maintains the
treatment goals, online nitrate analyzers have been installed at two locations, after the IX system and after
blending.
Source Water Quality

-
Nitrate - mg/L as NO3 (mg/L as N)
o Average – 35 (8)
o Minimum – 31 (7)
o Maximum – 53 (12)

Co-contaminants
o Arsenic (15 ug/L)
o Sulfate (66 mg/L)
Treatment Technology Selection
The conventional IX system was selected to treat both nitrate and arsenic. The decision was further influenced by
the ability to discharge the waste brine to a municipal sewer, a cost-effective disposal option. Often technology
selection is limited by the costs of brine management. If a utility has the option to dispose of the waste brine to a
municipal sewer it can significantly decrease the operations and maintenance cost of the system. No other
technologies were pilot tested prior to installation of the IX system.
Operational Notes
Since nitrate is an acute contaminant, the reliability of the treatment system is an utmost concern. The system is
equipped with online nitrate analyzers which causes a shutdown of the treatment system when nitrate is at or
above 35 mg/L as nitrate (8 mg/L as N). Additionally, the treatment system has experienced arsenic breakthrough
resulting in concentrations above the MCL. The treatment system has also experienced premature nitrate
breakthrough as a result of faulty distributors in the ion exchange vessels which have since been replaced.
Technical Report 6: Drinking Water Treatment for Nitrate
36
Treatment System Parameters





Design Capacity
o 400 gpm maximum capacity
Pretreatment
o None
Treatment system footprint
o Treatment system: 30’ x 35’
o Building footprint: None
Ion exchange pressure vessels
o Number of vessels: 3
o Diameter of vessels: 6’
o Height of vessels: 6’
Design Loading Rate
2
o 5.2 gpm/ft






Bed volumes prior to regeneration
o 345 – 470 (approximately
220,000 – 300,000 gallons
treated)
Resin Type: Purolite A200E and Purolite
A520E nitrate selective
Previous resins used: None
Salt Consumption: 1,700 lb/week (May –
Sept) and 600 lb/week (Oct – April)
Volume of brine generated
o 800 gal/vessel/backwash
o 99.7% water efficiency
Monitoring:
o Online nitrate analyzer
o Laboratory samples
Residuals Management
The waste brine is discharged to the sewer and sent to a municipal wastewater treatment facility, with an annual
cost of $12,000. There have not been any unexpected residuals that have impacted the disposal option.
Technology Benefits and Drawbacks
Benefits
 Ease of regeneration
 Direct-to-sewer brine disposal
 Simple, manually operated system
Drawbacks
 System has potential for breakthrough of
nitrate or arsenic
 Time intensive operations
 Required increase in operator certification
(California T-3)
Treatment Technology Costs
Capital Costs (Total with explanation or component costs)
Total:
$350,000
Annual O&M Costs (Total with explanation or component costs)
Total:
$66,500
Resin:
$13,000
Brine Disposal or
$12,000
Treatment:
Chemicals:
$5,500
Repair/Maintenance (not
$4,500
including Labor):
Power:
$2,500
Labor ($):
$28,000
Technical Report 6: Drinking Water Treatment for Nitrate
37
System Location: California
System Type: Community Water System
CASE #2
Treatment Type: Conventional Ion Exchange
Startup Date: 2006
System Description
Treatment Type
System Capacity
Raw Water Nitrate
Ion Exchange
400 gpm
44 mg/L as nitrate
10 mg/L as N
A California water utility operates a
system that has three groundwater
supplies with varying amounts of
nitrate contamination. Two of the
wells require treatment as the nitrate concentration is at or above the 45 mg/L as nitrate (10 mg/L as N) MCL. The
third well has nitrate ranging from 22 mg/L as nitrate (5 mg/L) as N to 31 mg/L as nitrate (7 mg/L as N) and does
not require treatment, but is blended with the IX treated water prior to distribution.
In 2006, a conventional IX system was installed. The treatment system is comprised of three pressure vessels that
contain the Rohm and Haas HP 555 ion exchange resin. Since the nitrate concentration in the impacted wells is
typically at the MCL, but above the established water quality goal of 35 mg/L as nitrate (8 mg/L as N), a sidestream
treatment approach is utilized. In sidestream treatment a portion of the flow is passed through the treatment
system while the remainder is bypassed. The IX treatment results in very low nitrate concentration and allows the
two streams to be combined to achieve the water quality goal. Sidestream treatment offers capital and
operational costs savings.
Source Water Quality

Nitrate – mg/L as nitrate (mg/L N)
o Average – 44 (10)

Co-contaminants
o Sulfate
Treatment Technology Selection
IX was selected for this system because the utility was familiar with the technology from other installations. No
technologies were pilot tested prior to the installation of the IX system.
Treatment System Parameters





Design Capacity
o 400 gpm maximum capacity
Pretreatment
o 100 mesh strainer
o 10 micron screen
Treatment system footprint
o Treatment system: 20’ x 100’
o Residual handling : 40’ x 100’
o Total footprint: 60’ x 100’
Ion exchange pressure vessels
o Number of vessels: 3
o Diameter of vessels: 4’
o Height of vessels: 6’
Design Loading Rate
2
o 10 gpm/ft
Technical Report 6: Drinking Water Treatment for Nitrate






Bed volumes prior to regeneration
o 309 BV
o Regeneration occurs every 12.4
hours
Resin Type: Rohm and Haas HP 555
Previous resins used: None
Salt Consumption: Estimated to be 32,000
lbs of salt per month
Volume of brine generated
o 1,000 gal/vessel/backwash
o 99.2% water efficiency
Monitoring:
o Online nitrate analyzer
o Laboratory samples
38
Residuals Management
The spent brine is held in a storage tank and ultimately disposed off site. Brine volumes are minimized by using a
partial flow treatment strategy where only 400 gpm is treated by the IX system while the remaining 500 gpm
bypasses the system. The untreated flow is recombined with the treated water prior to entering the distribution
system.
Technology Benefits and Drawbacks
Benefits
 Familiarity with technology
 Simple, manually operated system
Drawbacks
 No onsite brine disposal
 Design flaws
 Inconsistent operations
 Potential for nitrate breakthrough
Treatment Technology Costs
Cost information was not included with the survey response.
Operational Notes
This particular IX system has had a series of operational challenges, many of which can be attributed to faulty
engineering. Sections of exposed Schedule 80 PVC failed due to freezing, while other sections of pipe failed due to
prolonged UV exposure. The brine reclaim tank experienced algal growth and was ultimately replaced with an
opaque, UV-resistant tank.
The plant has experienced shutdowns due to an exceedance of the nitrate MCL. Routine sampling showed
distribution system nitrate concentrations above the MCL. The system utilizes an online nitrate analyzer to
prevent MCL violation; however, a calibration error prevented the system from shutting down as programmed. It
is believed a second failure occurred as a result of the brine saturator having a low salt concentration resulting in
incomplete regeneration of the resin.
It should be noted that, due to concerns of nitrosamine release (which can be common for IX systems), the
effluent of each vessel and the entry point to the distribution system are tested before the system is placed in
service.
Technical Report 6: Drinking Water Treatment for Nitrate
39
Modifications to Conventional Ion Exchange - Case Studies
The following case studies provide detailed information on the design and operation of full-scale lowbrine IX systems including MIEX®, ISEP®, and Envirogen (formerly Basin Water) systems.
System Name: Indian Hills
System Location: Indian Hills, CO
PWSID: CO 0130065
System Type: Community Water System
CASE #3
Treatment Type: Counter Current Magnetic Ion Exchange
Questionnaire completed by: Operations staff and Orica Water Care Representatives
Startup Date: 2009
System Description
Treatment Type
System Capacity
Raw Water Nitrate
Counter Current Ion Exchange
50 gpm
53 – 71 mg/L as nitrate
12 – 16 mg/L as N
The Indian Hills Water District
(District) utilizes a groundwater well
with a production capacity of
approximately 50 gpm. The well has
historical nitrate concentrations ranging from 12 mg/L to 16 mg/L of nitrate as N. The District has implemented
the counter-current ion exchange process developed by Orica Water Care. Unlike traditional packed bed IX, the
®
Orica process uses a Magnetic Ion Exchange (MIEX ) resin in a series of fluidized beds which allows for a reduction
in brine generation.
The minimization of waste brine is accomplished through frequent batch resin regeneration. The magnetized resin
encourages agglomeration of loaded resin particles, resulting in faster settling. Loaded resin is removed from the
bottom of the IX vessel and is passed to regeneration, while regenerated resin is continuously added at the top of
the IX vessel. This configuration reduces the risk of nitrate spiking/chromatographic peaking because clean resin,
added at the end point of the system, captures any displaced nitrate, while competing ions, such as sulfate, can be
removed early on in the resin vessel.
Regeneration is performed continuously in small batches. Loaded resin is passed to regeneration tanks through
the bottom of the IX vessel. The loaded resin is regenerated and then returned to the contactor vessel, thus
maintaining a consistent ion exchange capacity in the contactor vessel. Numerous regenerations are performed on
a daily basis, with the actual number of regenerations depending on the system’s flow rate.
Source Water Quality


Nitrate – mg/L as nitrate (mg/L N)
o Average – 62 (14)
o Minimum – 53 (12)
o Maximum – 71 (16)
Co-contaminants
o None noted in survey
Technical Report 6: Drinking Water Treatment for Nitrate
40
Treatment Technology Selection
The counter-current magnetic ion exchange system was selected based on the expected low levels of brine when
®
compared to conventional packed bed IX. Prior to full-scale implementation, the MIEX process was pilot tested at
Indian Hills. Indian Hills did not pilot test any other technology prior to implementation.
Treatment System Parameters




Design Capacity
o 50 gpm maximum capacity
o 25 gpm typical
o 11 – 14 gpm actual
Pretreatment/Post-treatment
o 1 micron bag filters
o Chlorination
Treatment system footprint
o Treatment system: 9.75’ x 5.5’
o Regeneration system: 13.3’ x 6.5’
o Residuals handling system:
 2,000 gal storage tank
o Total system footprint: 20.5’ x 9.75’
o Building footprint: 30’ x 50’
Number of contactors
o (2) – 3’ diameter; 6.75’ height







Design Loading Rate
2
o 7.27 gpm/ft at design flow
Bed volumes prior to regeneration
o 125 BV
Resin Type: MIEX DW 1401- Strong base
anion exchange resin in chloride form
Previous resins used: None
Salt Consumption: 3,500 lbs/MG treated
water
Volume of brine generated
o 2,800 gal brine/MG treated water
o 99.7% water efficiency
Monitoring:
o Online nitrate analyzer
o Laboratory samples
o Field colorimeter
Residuals Management
The waste brine is sent to a 2,000 gallon underground
storage tank. The brine is periodically pumped from the
storage tank and ultimately land applied. Indian Hills is
investigating deep well injection as an alternative disposal
mechanism. The waste brine was analyzed in the pilot
portion of the project and no unforeseen residuals were
identified that would further limit the brine disposal options.
While not specifically analyzed at this site, waste brine
®
from other MIEX installations has not had detectable
nitrosamine concentrations.
®
For the MIEX System, Bed Volumes are defined as the volume of
water treated per volume of resin regenerated. BV = gal water
treated/gal resin regenerated. For example, if 5 gal of resin were
regenerated for every 1000 gal of water treated, the regeneration
rate would be: BV = 1000gal/5gal = 200BV.
®
The design regeneration rate for the MIEX System is 125 BV, meaning that 8.0 gal of resin are regenerated per
1000 gal of water treated. The system regeneration rate can be adjusted through the control system. There is
approximately 1 – 2 gallons of resin attrition per 1 MG of treatment. Small amounts of resin are periodically added
to the regeneration system manually.
Technical Report 6: Drinking Water Treatment for Nitrate
41
Technology Benefits and Drawbacks
Benefits
 Consistent treatment performance
 Relatively low volumes of waste brine
 No nitrate dumping
Drawbacks
 Generation of waste brine
 Resin lost in the treatment must be
removed prior to distribution
Treatment Technology Costs
Capital Costs (Total with explanation or component costs)
Operating and Monitoring
Approximately $150,000
Equipment:
(IX treatment system, including initial resin fill)
O&M Costs (Total with explanation or component costs)
Resin:
$0.08 – $0.15/1000 gallons treated
Resin Disposal:
N/A
Brine Disposal or
N/A
Treatment:
Chemicals:
Salt (based on an estimated salt cost of $100/ton):
$0.15 – $0.20/1000 gallons treated
Sources*
Vaughan, F., Orica Watercare. (2010) Personal Communication. August, 2010.
Martin, B. (2010) Completed questionnaire. September, 2010.
*Unpublished sources used in the development of the case studies are not reflected in the References section of this
report.
Technical Report 6: Drinking Water Treatment for Nitrate
42
System Location: California
CASE #4
System Type: Community Water System
Treatment Type: Ion Exchange, Well Modification (proposed), Well Abandonment
Startup Date: 2003 – 2009
System Description
Treatment Type
Ion Exchange and Blending
A California district operates 27
System Capacity
500 – 900 gpm
groundwater sources, 15 of which
Raw
Water
Max
35 – 89 mg/L as nitrate
contain nitrate at or near the MCL.
Nitrate
8 – 20 mg/L as N
The district has considered and
implemented a variety of solutions
including IX, well modifications, and well destruction. The nitrate impacted wells range in capacity from 500 gpm
to 1000 gpm with nitrate ranging from 35 – 89 mg/L as nitrate (8 – 20 mg/L as N). It should be noted that a water
quality goal of 35 mg/L of nitrate as NO3 (< 8 mg/L of nitrate as N) has been implemented in the district, and all
sources are treated to below this level.
The district began actively treating the nitrate contaminated sources in 2003 and the most recent system was
installed in 2009. The district currently has 6 wells with active IX systems, 7 wells have been destructed or made
inactive, 2 wells are being considered for well modifications, and one well has an enhanced control system where
there will be an automatic shut down if the nitrate levels exceed a predetermined level. The range of historical
nitrate concentrations of the wells is shown below.
Source Water Quality

Nitrate – mg/L as nitrate (mg/L N)
o Well A- 7 to 58 (1.5 to 13.1)
o Well B- 15 to 48 (3.4 to 10.8)
o Well C- 4 to 47 (0.9 to 10.6)
o Well D- 13 to 88.4 (2.9 to 20.0)
o Well E- ND to 40.7 (ND to 9.2)
o Well F- 11 to 53.8 (2.5 to 12.1)
o Well G- 2 to 52 (0.5 to 11.7)
o Well H- 8.5 – 72.4 (1.9 to 16.3)
o
o
o
o
o
o
o
Well I- 15.0 to 40.4 (3.4 to 9.1)
Well J- 6 to 33.1 (1.4 to 7.5)
Well K- 51 (11.5)
Well L- 87 (19.6)
Well M- 37 (8.4)
Well N- 37.4 (8.4)
Well O- 64 (14.5)
Treatment Technology Selection
The first nitrate treatment system the district installed was in 2003. At the time of installation IX was deemed the
best available technology as it was the most economical with respect to the well’s nitrate concentrations and flow
rates. When possible, the district elected to install similar systems on the wells that required treatment in an
effort to establish operational parallels between their systems. When the footprint of the system or excessive
nitrate concentrations made IX treatment infeasible, the district has elected for well destruction. In recent cases
where treatment is necessary, the district has evaluated well modifications to determine if it is feasible to reduce
the nitrate concentrations without the need for active treatment.
Technical Report 6: Drinking Water Treatment for Nitrate
43
The following section shows the typical parameters of the district’s individual IX systems with the exception of the
salt consumption which represents the total salt use for the entire district.
Treatment System Parameters






Design Capacity
o 500 – 900 gpm
Pretreatment
o None
Treatment system footprint
o Two 35’ x 20’ cement slabs
o Treatment system: 35’ x 10’
o Housed in a cargo container
Residuals handling system
o Three 12’ x 12’ dia. tanks
Ion exchange pressure vessels
o Number of vessels: 16
o Diameter of vessels: 3’
o Height of vessels: 6’
Design Loading Rate
2
o 12 gpm/ft







Bed volumes prior to regeneration
o 300 BV
Treatment System Manufacturer
o Envirogen Technologies
Resin Type: Conventional type 1 ion
exchange resin
Previous resins used: None
Salt Consumption: 25 tons/ week
combined for all systems
Volume of brine generated
o 1.3 bed volumes per vessel
regenerated
o Approximately 99.6% water
efficiency
Monitoring
o Online nitrate analyzer
o Laboratory samples
Residuals Management
The waste brine is disposed of at an offsite facility. This decision has been impacted by elevated selenium and
NDMA in the waste brine.
Technology Benefits and Drawbacks
Benefits
 Allows wells that would normally be
offline due to nitrate contamination to be
used for potable purposes
 The treatment system vendor provides onsite technical support and operations
Technical Report 6: Drinking Water Treatment for Nitrate
Drawbacks
 Treatment system failure poses an acute
health risk to the potable water system
 Time intensive operations if there is a
treatment disruption
 The systems have numerous valves and
moving parts. If there is a mechanical
failure it can be difficult to identify the
source
 High operating and brine disposal costs
 The district pays the system vendor for
stand-by fees and service charges if the
system is in stand-by mode during times of
low water use
44
Treatment Technology Costs
Capital Costs (Total with explanation or component costs)
Total:
$360,000 per unit – Electrical, Piping, Setup, and Sampling/testing
(construction costs)
The district does not own the treatment plants, tanks, resins, etc.
O&M Costs (Total with explanation or component costs)
$59,239.41 per month, per unit
$34,016.75 per month, per unit
Total:
Brine Disposal or
Treatment:
Repair/Maintenance (not
including Labor):
Salt:
Other:
$3,525.00 (service fee) per month, per unit
$13,541.41 (salt) per month, per unit
$7,500.00 (stand by fee) per month, per unit
$656.25 (tax) per month, per unit
Technical Report 6: Drinking Water Treatment for Nitrate
45
System Name: City of Chino
System Location: Chino, CA
PWSID: CA3610012
System Type: Community Water System
CASE #5
Treatment Type: Ion Exchange (IX)
Questionnaire completed by: Gilbert Aldaco, Water Utilities Supervisor, City of Chino Public Works
Startup Date: 2006
System Description
Treatment Type
Ion Exchange and Blending
The City of Chino, CA, operates 13 groundwater
System Capacity
5000 gpm
sources and 3 GWUDI (groundwater under
direct influence of surface water) sources. All of
the GWUDI and 8 of the groundwater sources
Raw Water Nitrate
~40 – 200 mg/L as nitrate
are impacted by nitrate contamination. IX and
~9 – 45 mg/L as N
blending are used to address high nitrate and
®
perchlorate levels. One of the wells is inoperable due to perchlorate contamination. IX using the ISEP system is
th
used for the treatment of 3 wells ranging in capacity from 1100 to 2300 gpm and is being considered for a 4 well.
Additionally, an Envirogen (formerly Basin Water) IX system is used for the treatment of an 800 gpm well. Treated
surface water from the Metropolitan Water District of Southern California (MWDSC) and treated groundwater
®
from the Chino Basin Desalter Authority is used for blending. The blend ratio is 3:1. The ISEP system was built in
2005, with a capacity of 5000 gpm (7.2 MGD), and approved for operation in 2006.
Source Water Quality

Nitrate – mg/L as nitrate (mg/L N)
o 40 to 100 (9 to 45)

Co-contaminants
o Perchlorate
Treatment Technology Selection
The costs and feasibility of several alternatives for nitrate treatment, including reverse osmosis, biological
processes, and conventional (fixed bed) IX were investigated. Biological treatment and fixed bed IX were pilot
®
tested prior to installation of the current system. The ISEP system was selected based in part on the potential to
simultaneously address perchlorate contamination and due to the efficiency of operation.
Additional Information
 Operators were not required to increase their level of certification to operate the treatment plant.
 When asked about the areas in which the nitrate treatment technology has exceeded expectations, the
response was, “Reliability and ability to effectively remove contaminants at varied flow rates (i.e., 1500
gpm to 5000 gpm).”
 There has been no incidence of a plant shutdown due to an alarm or exceedance of an MCL; however, the
plant was shut down for approximately 1 month due to theft of computer control equipment.
Technical Report 6: Drinking Water Treatment for Nitrate
46
Treatment System Parameters
 Design Capacity
o 5000 gpm
 Pretreatment: Filtration
 Footprint
o Treatment system: 4400 sq.ft.
o Residuals handling: 2300 sq.ft.
o Total system: 6700 sq.ft.
 Ion exchange vessels
o Number of vessels: 30
o Diameter of vessels: 3’
o Height of vessels: 6’
 Max. nitrate concentration goal for
delivered water
o ~36.3 mg/L NO3 (~8.2 mg/L N)
 Nitrate concentration goal for the
treatment system (before blending)
o ~19.0 mg/L NO3 (~4.3 mg/L N)
 Manufacturer: Calgon Carbon Corporation
 Resin Type: Purolite SBA






Previous resins used: None
Bed volumes prior to regeneration
o Continuous regeneration
Salt Consumption (@ 2400 gpm)
o Nitrate mode – 4.9 tons/day
o Perchlorate mode – 18.6
tons/day
Volume of brine generated (@ 2400 gpm)
o Nitrate mode: 12.7 gpm
 99.5% water efficiency
o Perchlorate mode: 31 gpm
 98.7% water efficiency
Monitoring
o Weekly effluent testing for
nitrate and perchlorate
o Monthly effluent testing for
nitrite, sulfate, and total Coliform
o Monthly raw water testing for
nitrate, perchlorate, nitrite,
sulfate, total Coliform, HPC
Grab Samples for resin byproduct testing
were negative for nitrosamines
Residuals Management
Waste brine is discharged to a non-reclaimable waste pipeline leading to the LA County Sanitation District, with a
total disposal cost of ~$50,000/yr.
Technology Benefits and Drawbacks
Benefits
 Flexibility of operation and High efficiency
 Reliability and Ease of O & M
Drawbacks
 None listed
Treatment Technology Costs
Capital Costs (Total with explanation or component costs)
Total:
Housing:
Piping:
Resin:
Testing:
Other:
~ $4.6 million
~ $492 K
~ $1.1 million
~ $350 K
~ $20 K
~ $2.4 million for ISEP Equipment and Engineering; ~ $350 K for
electrical upgrade; ~ $200 K for pumps and associated
equipment.
Annual O&M Costs (Total with explanation or component costs)
Total:
Not reported
Brine Disposal or Treatment:
~ $50 K
Chemicals:
~ $364 K for salt, ~ $50 K for hydrochloric acid
Technical Report 6: Drinking Water Treatment for Nitrate
47
3.2 Reverse Osmosis (RO)
Reverse osmosis can be a feasible option for nitrate removal in both municipal and Point-of-Use
applications (Cevaal et al. 1995; Black 2003; Howe 2004). The first commercial application of RO for
potable water treatment was in Coalinga, CA, in 1965 (National Academy of Engineering 2008). RO can
be used to address multiple contaminants simultaneously including ionic (e.g., nitrate, arsenic, sodium,
chloride, and fluoride), particulate (e.g., asbestos and Protozoan cysts), and organic constituents (e.g.,
some pesticides) (Dvorak & Skipton 2008). Water is forced through a semi-permeable membrane under
pressure such that the water passes through, while contaminants are impeded by the membrane. A
typical process schematic of RO for nitrate removal from potable water is illustrated in Figure 8.
Figure 8. Reverse osmosis schematic.
The required pressure will be dependent on the concentration of solute in the feed water. The collected
concentrate is high in nitrate and other rejected constituents (salts) and requires appropriate disposal.
The extent to which the RO membrane removes constituents from the water is called the rejection rate.
Rejection rates for sodium chloride and sodium nitrate can be as high as 98% and 93%, respectively
(Elyanow & Persechino 2005). The water recovery rate of an RO system refers to the “maximum
percentage of permeate produced from a given feed flow,” and the flow/flux rate is “the maximum flow
of permeate through a sq. ft. of the membrane” (Cevaal et al. 1995, p. 107). Modifications and
improvements to standard RO have led to the emergence of more efficient RO processes including High
Efficiency Reverse Osmosis (HERO™) and Ultra-low Pressure Reverse Osmosis (ULPRO) systems.
3.2.1 Reverse Osmosis - Design Considerations
Table 6 summarizes key design considerations in the application of RO to nitrate removal from potable
water.
Technical Report 6: Drinking Water Treatment for Nitrate
48
Table 6. Summary of design considerations for reverse osmosis.

RO Membranes
Pretreatment










Post-Treatment

Chemical Usage





O&M







System
Components

Thin film membranes - Higher rejection rates, lower pressures than CTA
membranes
Cellulose triacetate membranes (CTA) - Tolerant of low chlorine levels
Hollow fiber membranes - Compact configuration
Ultra-low pressure RO membranes (ULPRO)
Consider rejection rate, water recovery, and frequency of cleaning
Multiple contaminant removal
Prevent membrane damage, scaling and biological, colloidal, and organic fouling
Scaling
o Acid (e.g., sulfuric acid) and/or anti-scaling agents (e.g., poly-acrylic
acid)
o Water softening
Biological fouling
o Upstream disinfection, but dechlorination to prevent membrane
damage
 Reducing agent (e.g., sodium bisulfate) or activated carbon
Colloidal fouling
o Pre-filtration to remove suspended solids
o Chemical treatment to keep suspended solids in solution
Avoid corrosion
o Adjust pH, restore alkalinity for buffering capacity (see
remineralization) and/or add corrosion inhibitor (e.g., polyorthophosphate blend)
Remineralization
o Blending, pH adjustment, addition of caustic soda, bicarbonate, sodium
carbonate, phosphates, and/or silicates
Blending, disinfection, and storage
pH adjustment, up and down (acids and bases)
Anti-scalants
Cleaning chemicals (acids and bases)
Frequency of membrane cleaning depends on water quality and membrane
used
o Typically once a month for 1 hour
Management of chemicals and pre-filtration system
Waste storage and disposal
Membrane replacement/membrane life
o Up to 20 years or more with appropriate pretreatment and
maintenance
Monitoring of nitrate levels and membrane flux rate
Automation can be feasible
Low operational complexity (though higher than IX depending on pretreatment
needs)
Maximize water recovery while minimizing energy use
o Pressure range of 100 to 200 psi
o Based on system size and feed water quality
Key system configuration parameters are system flow rate, number of
membranes/stages, system footprint, flux rate, water recovery rate, pump
selection and sizing, pressure requirement, cleaning frequency
Technical Report 6: Drinking Water Treatment for Nitrate
49


Waste
Management and
Disposal




Limitations



Significant cost of waste brine/concentrate disposal of greatest concern for
inland systems
Management options include sewer or septic system, drying beds, trucking offsite, coastal pipeline, deep well injection, and advanced treatment
Disposal options can be limited by waste brine/concentrate water quality (e.g.,
volume, salinity, metals, and radionuclides)
Optimization of recycling and treatment of waste brine/concentrate
Higher water recovery (more costly) to minimize waste volume (tradeoff
between energy costs and disposal costs)
Need to prevent membrane scaling, fouling, and damage
o Hardness, iron, manganese, suspended solids, silica, and chlorine
High energy demands
Disposal of waste concentrate
Complete demineralization (no control over target constituents)
Water Quality
While regulated by operational pressure, the water recovery rate depends largely on feed composition.
Problematic constituents include sulfate, calcite, calcium sulfate dehydrate (gypsum), silica, colloids, and
microorganisms (Cevaal et al. 1995; Elyanow & Persechino 2005; Tarabara 2007). Filtration upstream of
the RO membranes is required to remove suspended solids. The life of the RO membranes and
prefilters, and the frequency of membrane cleaning are also directly dependent on water quality and
the efficiency of pretreatment measures.
Treatment efficiency can be compromised by membrane fouling. Anything that decreases available
membrane surface area can limit the passage of water through the membrane and decrease water
recovery. The four main types of membrane fouling are scaling, colloidal fouling, biological fouling, and
organic fouling. When the salt concentration in the feed water exceeds the saturation point at the
membrane surface, precipitation of solids on the membrane can diminish the removal efficiency
(Elyanow & Persechino 2005). Scale forming constituents,14 such as precipitates of silica, calcium,
barium, and strontium salts pose a significant threat to RO by limiting the membrane surface area
14
Pretreatment options to prevent scaling include the addition of acid and/or anti-scaling agents and water softening. By
decreasing the pH, the prevalent form of the carbonate cycle is bicarbonate rather than the carbonate ion. The precipitation of
calcium carbonate will therefore be limited by the concentration of the carbonate ion. Note: the addition of acid helps only if
the scale forming constituent is calcite, due to the speciation of carbonate (Lenntech, 2009c). Anti-scaling chemicals can
function in three ways: threshold inhibition, crystal modification, and dispersion (Lenntech, 2009c). Threshold inhibition occurs
when the anti-scalant increases the solubility of a potential scalant to super saturation, allowing for a greater concentration to
remain in solution. Crystal modification refers to the interference of negatively charged functional groups on the anti-scalant
with salt crystal formation and membrane attachment. Anti-scaling chemicals can also promote dispersion of crystals by
attaching to them and increasing their negative charge. The most economical means of membrane scale control will depend on
the system, but typically the use of anti-scaling agents alone or in combination with acid addition is the most financially prudent
option. The third alternative to prevent membrane scaling is to remove the problematic constituents from the water entirely.
Water softening can be used to replace calcium and magnesium cations with sodium ions. Generally the most expensive
option, this requires the addition of a water softener upstream of the membranes and will result in an additional brine waste
stream.
Technical Report 6: Drinking Water Treatment for Nitrate
50
through which water can pass.15 Development of biomass on the membrane surface can have a similar
negative effect on performance.16 Additionally, RO membranes have limited to zero tolerance for
organic species, like grease and oil; organic fouling inhibits membrane performance (Lenntech 2009e).
Lastly, suspended solids not removed by pretreatment filtration can inhibit membrane performance
through colloidal fouling.17 Silica can be a particularly problematic constituent for RO membranes due
to the potential for colloidal silica fouling and silica scale formation, which can be very difficult to
remove. Modifications to conventional RO have emerged to manage high silica source waters (Section
3.2.5 Reverse Osmosis - Improvements and Modifications, below). Common pretreatment measures
used to address membrane fouling are included in Table 6.
With acid addition in pretreatment, the permeate will need to be neutralized in post-treatment to avoid
corrosion in the distribution system. Alternatively a corrosion inhibitor, such as a poly-orthophosphate
blend, can be used (U.S. EPA 2003). Additionally, because RO is not selective in the removal of ions,
treated water is demineralized. Thus, alkalinity may need to be added to restore minerals and buffering
capacity to avoid corrosion in the distribution system18 (WHO 2004; Lenntech 2009f). In post-treatment,
blending (if used) follows the RO modules, after which water is disinfected and stored (Cevaal et al.
1995).
System Components and Site Considerations
RO systems are operated in stages. Following pretreatment, water is pumped through the membranes
with booster pumps (Cevaal et al. 1995). Water recovery can be improved by passing the concentrate
through the membranes more than once, but higher water recovery comes at the expense of increased
scaling potential. As the water becomes more concentrated, saturation can lead to precipitation on the
membrane (Elyanow & Persechino 2005). The membrane flux rate can be decreased to limit scaling and
increase membrane life (Cevaal et al. 1995). Key aspects of the system are pressure pumps, membrane
configuration, membrane flux rate, number of stages/number of membranes, flow rate, and cleaning
and anti-scalant requirements. Pump sizing is based on system size and pressure requirements. The
water recovery rate can be regulated by the operational pressure. The necessary pressure is dependent
on the concentration of solute in the feed water. For example, with a conductivity of 1550 μS/cm,
15
The Langelier Saturation Index (LSI) and other corrosion indices are used to characterize the scaling potential of calcium
carbonate (calcite), a commonly problematic constituent.
16
Upstream disinfection can limit membrane biofouling; however, additional measures must be taken to avoid membrane
exposure to chlorine “by dosing with a reducing agent (such as sodium bisulfate) or by contacting with activated carbon”
(Elyanow & Persechino 2005, p. 6).
17
The potential for colloidal fouling is typically characterized by the silt density index (SDI). An SDI greater than 3 can indicate
the need for further pretreatment to minimize cleaning frequency and membrane damage (Lenntech 2009e; Elyanow &
Persechino 2005). Chemical treatment can keep suspended solids in solution. Alternatively, a prefilter can be used to remove
solids from the feed water (Remco Engineering N.D.).
18
It is important to note the relationship between alkalinity and pH. Alkalinity is a measure of buffering capacity or the
resistance to changes in pH. Demineralized water or water with a low buffering capacity will be susceptible to more dramatic
pH changes and is considered unstable. The pH of acidic product water should be adjusted and the buffering capacity of
demineralized product water should be restored to avoid corrosion downstream. Options for the stabilization and
remineralization of demineralized water include blending, pH adjustment, and addition of caustic soda, bicarbonate, sodium
carbonate, phosphates, and/or silicates (WHO 2004; Lenntech 2009f). Corrosion indices and models can be used to determine
appropriate solutions for specific scenarios.
Technical Report 6: Drinking Water Treatment for Nitrate
51
Panglisch et al. (2005) determined the suitable pressure to be 145 – 174 psi. Similarly, at start-up, the
operational pressure at an RO facility in Brighton, CO, used for nitrate removal was 170 psi (Cevaal et al.
1995).
Two types of spiral wound RO membranes are commonly used: polyamide thin film composite
membranes (TF) and cellulose triacetate membranes (CTA) (Cevaal et al. 1995 and Remco Engineering
N.D.). While TF membranes are capable of slightly higher rejection rates and can be operated at lower
pressures, CTA membranes are tolerant of low chlorine levels (AWWA 2011). Hollow fiber RO
membranes are also available, which can minimize system footprint, but can be more susceptible to
fouling from suspended solids (Hydranautics 2001). Using recently developed ultra-low pressure RO
(ULPRO) membranes, operational pressures can be reduced, decreasing power costs (Drewes et al.
2008). For additional information see Section 3.2.5 Reverse Osmosis - Improvements and Modifications.
Residuals Management and Disposal
The volume of the waste stream can be considerable, ranging from 15% to 50% of the starting volume
depending on the operational parameters (Howe 2004). The waste stream, or concentrate, can be
discharged to a wastewater treatment plant or a septic system (Bilidt 1985; Howe 2004), as long as the
system can accommodate an increased salt concentration. Additional disposal options include drying
beds, infiltration basins, trucking off-site, a coastal pipeline, deep well injection, advanced treatment,
and most commonly, discharge to nearby surface salt-waters (i.e., oceans), when available (Howe 2004).
Important water quality characteristics of the waste brine (e.g., volume, salinity, metals, and
radionuclides) can affect the feasibility and costs of disposal. Options for inland communities are more
limited and costly. Proximity to coastal power plants can be advantageous. Power plants using ocean
water for cooling can provide a pre-existing infrastructure for disposal to ocean waters (Black 2003).
The high cost of nitrate laden concentrate disposal has led to research into optimization of recycling and
treatment of this waste stream. Coupling of RO systems with biological, chemical, or catalytic
denitrification enables removal of nitrate from the waste concentrate, with reduction to nitrogen gas.
Additionally, the Vibratory Shear Enhanced Process (VSEP), from New Logic Research, has been explored
in the context of treatment of RO concentrate from wastewater treatment. By applying a shear force
across the membrane, pore clogging by colloidal particles is minimized, leading to the potential for
improved water recovery (Lozier et al. N.D.). Several combined configurations of interest are discussed
below in Section 3.6 Brine Treatment Alternatives and Hybrid Treatment Systems.
Maintenance, Monitoring, and Operational Complexity
RO systems are typically highly automated, accommodating the greater operational complexity of RO
operation, in comparison with IX. Several operational decisions will be dictated by operator availability
and training. For instance, chemical addition in pretreatment can be quite effective, but will require
more intensive maintenance. In contrast, opting for the more expensive choice, installing a water
softener, will require less operator time. Membrane cleaning frequency varies widely and depends on
the efficiency of pretreatment measures and water quality. Interruption of operation is not always
Technical Report 6: Drinking Water Treatment for Nitrate
52
necessary as the membranes can be isolated and cleaned in place (CIP) in stages. Membranes are
typically cleaned with acid or caustic solutions (WA DOH 2005). Cleaning agents are selected based on
the cause of membrane fouling. Cleaning and rinsing can take an hour and with effective pretreatment,
monthly membrane cleaning should be sufficient (Remco Engineering N.D.; Bates N.D.). With effective
pretreatment, cleaning frequency can be significantly minimized. An RO plant in Milan, Italy, using antiscalants, requires cleaning only once every 18 months (Elyanow & Persechino 2005). Filters should be
checked weekly and, if used, the water softener should be maintained with sufficient salt every day.
Effluent nitrate concentrations require monitoring to ensure compliance and to assess membrane
performance. Over time, membrane degradation will lead to a gradual decrease in removal efficiency.
Membrane life varies and can range from 5 to 20 years or more (Remco Engineering N.D.). Waste
concentrate management consists of appropriate storage and disposal. More operationally complex
than IX, operators of RO systems will typically require more training and system maintenance will
demand more time and chemicals. However, with the implementation of appropriate pretreatment
measures and the ability for system automation, operational complexity can be minimized.
3.2.2 Reverse Osmosis - Cost Considerations
For the efficient operation of an RO system, the fundamental objective is to maximize water recovery
with the minimum amount of energy and chemical usage, while meeting necessary potable water
guidelines. Factors affecting system cost include facility size (how much water), source water quality
(including nitrate concentration), environmental factors (temperature and pH), and target effluent
nitrate concentration (Bilidt 1985). Lower operating pressures are less costly, but result in decreased
water recovery. High operating pressures maximize water recovery (decreasing disposal costs), but
increase energy demands and the need for “specialized pumps” (WA DOH 2005). Thus, there is a tradeoff between the costs of increasing water recovery (increased pretreatment and operational pressure)
and the costs of disposal (pumping, storage, and disposal expenses). In pretreatment, the use of antiscalants rather than acid or a water softener is generally the least expensive. The use of a water
softener is the least cost competitive option (Lenntech 2009c). Regarding small water systems, “reverse
osmosis is one of the most expensive forms of centralized treatment and will likely not be cost effective
unless there are multiple contaminants needing removal” (WA DOH 2005, p. 27).
Capital costs for RO include land, housing, piping, storage tanks, O&M equipment, membranes,
preliminary testing (pilot studies), permits, and training. O&M costs include membrane and filter
replacement, membrane and filter disposal, concentrate disposal or treatment, chemical use (antiscalant, pH adjustment, disinfection, etc.), repair, maintenance, power, and labor.
Published cost information, from existing RO installations used for nitrate treatment, is listed in Table 7.
Costs have been adjusted to 2010 dollars, unless indicated otherwise. Costs can be difficult to assess
due to inconsistencies in how cost information is reported. Comparison of treatment costs is not always
valid due to differences in influent water quality parameters, system size, waste management options,
and system configuration. Published costs do not always include comparable information. It would be
inappropriate to compare the O&M costs of a facility that excludes disposal costs with others that
include this information. The listed cost information is provided as an approximate range of costs for
Technical Report 6: Drinking Water Treatment for Nitrate
53
specific facilities. Costs for implementing RO may be very different from those listed here. A thorough
cost analysis of design parameters for specific locations would be required for accurate cost estimation.
The information gathered through the questionnaire includes detailed costs associated with the unique
case studies included in this analysis. A detailed discussion of treatment costs is included below in
Section 6 Treatment Cost Analysis.
Table 7. Selected costs* of reverse osmosis systems for nitrate removal.
System Flow**
< 0.5 MGD
0.5 – 5 MGD
5+ MGD
3.51 – 5.17 [1, 2]
1.00 – 1.30 [3, 4]
0.95 [3]
O&M Cost ($/1000 gal)
1.46 – 16.16 [1, 2]
1.22 – 2.01 [3, 4]
1.63 [3]
Total Annualized Cost ($/1000 gal)
5.73 – 19.70 [1, 2]
2.52 – 3.21 [3, 4]
2.58 [3]
Annualized Capital Cost ($/1000 gal)
*Costs have been adjusted to 2010 dollars with 7% interest over 20 years, unless indicated otherwise.
**When available, costs are based on actual system flow rather than design capacity.
[1] Walker (N.D.), costs not adjusted to 2010 dollars. [2] Personal communication with representatives of two
small water systems (2010). [3] Conlon et al. (1995). [4] Cevaal et al. (1995).
3.2.3 Reverse Osmosis - Selected Research
Much research has focused on RO; Table A.2 of the Appendix is a list of recent studies relevant to nitrate
removal from potable water and several examples of RO application. Current RO research focuses on
improvements of membranes and waste management, and decreasing energy use.
3.2.4 Reverse Osmosis - Summary of Advantages and Disadvantages
A summary of advantages and disadvantages of RO in comparison with other treatment options is listed
in Table A.6 of the Appendix. Advantages of RO include high quality product water, multiple
contaminant removal, desalination (TDS removal), feasible automation, and application for POU
applications. According to Elyanow & Persechino (2005), in their comparison of RO and EDR, “…the best
economical choice for small capacity systems (<110 gpm or <25 m3/hr) are simple RO plants, which have
less electrical and hydraulic complexity than EDR and other technologies” (p. 7). In waters where
salinity is a problem, RO can be better suited than IX due to the ability to remove multiple contaminants
(including trihalomethane formation potential precursors (THMFPs)) (Cevaal et al. 1995).
Disadvantages of RO include high capital and O&M costs, membrane fouling susceptibility, high
pretreatment and energy demands, and potentially large waste volume (lower water recovery) requiring
disposal. The high cost of disposal from inland locations can result in RO treatment becoming cost
prohibitive. Howe (2004) presents several alternatives to conventional disposal measures of RO waste
brine, including reuse for industrial processes, processing (e.g., for salt production), or use in energy
generation (“solar brine pond”).
Technical Report 6: Drinking Water Treatment for Nitrate
54
3.2.5 Reverse Osmosis - Improvements and Modifications
Process Modification
High Efficiency Reverse Osmosis (HERO™) is a patented multi-step process enabling increased water
recovery (greater than 90%) and minimizing cleaning requirements. This process limits scaling by
incorporating hardness reduction, CO2 stripping, and pH adjustment (GE 2010b). Raw water is subjected
to intensive pretreatment before passing through the RO membranes as follows (Engle 2007):

Weak acid cation exchange (WAC) is used to remove hardness ions,

CO2 stripping is used to remove carbonate and increase pH, and

Base addition is used to increase the pH to a level of 10.5.
An example flow diagram is illustrated in Figure 9.
With such pretreatment, water fed to the RO membranes is softened and pH is adjusted high enough to
significantly increase the solubility of silica. The high chemical usage and multiple steps result in a more
complicated process than conventional RO. However, benefits include increased water recovery,
decreased waste volume, and the ability to treat severely impaired and poor quality source water
containing multiple contaminants (Engle 2007).
The HERO™ process was initially designed to produce ultra-pure water for use in electronics applications
and was patented by Debasish Mukhopadhyay with licensing rights for different applications (Engle
2007). The HERO™ process has been implemented for drinking water treatment in the small community
of Yalgoo, Australia, to produce high quality drinking water from brackish groundwater high in silica and
nitrate (Water Corporation 2007; Water Corporation 2009; Thomson et al. 2009). Higher removal rates
result in decreased waste volume. Using the HERO™ process in Yalgoo, waste volumes are as low as
“one-tenth of a conventional plant’s concentrated brine residue for disposal, eliminating the need for
big evaporation ponds” (Water Corporation 2007, p. 8).
Technical Report 6: Drinking Water Treatment for Nitrate
55
Figure 9. Flow chart of the HERO™ process. (Source: reproduced with permission, Central Arizona Salinity Study
2006.)
Membrane Modification – Low Pressure Membranes
Research and development in membrane technology has resulted in the emergence of Ultra-Low
Pressure Reverse Osmosis (ULPRO). In contrast to the high pressures required for conventional RO, use
of ULPRO membranes allows for lower operating pressures and improved flux rates. Energy demands
can be reduced due to lower operating pressures; however, pretreatment practices to prevent
membrane scaling and fouling are similar to those necessary for conventional RO membranes (Drewes
et al. 2008). ULPRO membranes are available from several manufacturers. Operating pressures are in
the range of 50 to 125 psi, while the pressures required for conventional RO membranes can be over
200 psi (Excel Water 2007; Drewes et al. 2008; Koch Membrane Systems 2008). Drewes et al. (2008)
compared the performance of ULPRO membranes and conventional RO membranes, wherein
pretreatment included nano-filtration for both RO options. Findings indicate that the ULPRO
membranes included in the study were capable of successfully removing nitrate and multiple additional
contaminants to potable water standards. “With regard to operating costs, operating pressure is the
only TMG [ULPRO membrane] operating parameter considered to deviate from the benchmark ESPA2
[conventional RO membrane] membrane. Pretreatment requirements and recovery rate were the
same. Electrical consumption will be directly proportional to the required operating pressure” (Drewes
et al. 2008, p. 93). However, in the cost comparison between the two membranes, the benefits of lower
operating pressures were overshadowed by the poor recovery of the ULPRO membranes after cleaning.
Technical Report 6: Drinking Water Treatment for Nitrate
56
The authors suggest that the cleaning of the ULPRO membranes would need to be optimized for an
improved cost comparison.
3.2.6 Reverse Osmosis - Case Studies
The following case studies provide detailed information on the design and operation of full-scale RO
treatment plants used for nitrate removal. Chino I Desalter and Chino II Desalter are combination
systems using both RO and conventional IX.
Technical Report 6: Drinking Water Treatment for Nitrate
57
System Location: California
System Type: Community Water System
CASE #6
Treatment Type: Reverse Osmosis (RO)
Startup Date: 2002
System Description
Treatment Type
System Capacity
Raw Water Nitrate
Reverse Osmosis and Blending
120 gpm
75 – 84 mg/L as nitrate
17 – 19 mg/L as N
A California water utility operates a
system that has three groundwater
supplies, one of which has nitrate at
levels that exceed the MCL. The
impacted well has nitrate concentrations that range from 75 to 84 mg/L as nitrate (17 to 19 mg/L as N) and has a
typical production capacity of 100 gpm. In 2002, the utility implemented a blending program and installed an RO
system for nitrate control and treatment.
In RO, raw water is forced through a semi-permeable membrane under pressure such that the water passes
through, while contaminants are impeded by the membrane. The required pressure will be dependent on the
concentration of solute in the feed water. The collected concentrate is high in nitrate and other rejected
constituents (salts) and requires appropriate disposal. The extent to which the RO membrane removes
constituents from the water is called the rejection rate. Rejection rates for sodium chloride and sodium nitrate can
be as high as 98% and 93%, respectively (Elyanow & Persechino 2005).
The high nitrate supply is blended with one of the other two groundwater sources prior to RO treatment. The RO
system reliably removes nitrate to below 35.4 mg/L as nitrate (8 mg/L as N) and the water delivered to consumers
typically has nitrate levels below 13.3 mg/L as nitrate (3 mg/L as N). This system utilizes a leach field type system
to land apply the RO concentrate.
Source Water Quality

Nitrate - mg/L as nitrate (mg/L N)
o Average - 75 (17)
o Minimum - 80 (18)
o Maximum - 84 (19)

Co-contaminants
o Fluoride - 3.3 mg/L
o Arsenic
o Radium
Treatment Technology Selection
RO was selected as the most appropriate treatment system as the technology can reliably remove nitrate in
addition to the co-occurring contaminants that are present, specifically fluoride, arsenic, and radium.
Technical Report 6: Drinking Water Treatment for Nitrate
58
Treatment System Parameters




Design Capacity
o 120 gpm maximum capacity
Pretreatment
o Anti-scalant (Hyposperse MCD
150)
Treatment system footprint
o Treatment system: 15’ x 30’
o Total system footprint: 40’ x 100’
RO System
o System manufacturer: Aria™
o Membrane manufacturer:
Osmonics
o Number of stages: 4
o Number of RO elements per
stage: 4




Clean-in-place (CIP)
o CIP frequency: Quarterly
(4x/year)
o Initiated when there is a 15%
decrease in permeate flow or salt
rejection or a 15% increase in
trans-membrane pressure
o CIP chemicals: Dilute phosphoric
acid
Water efficiency: 80%
Monitoring
o Laboratory samples
Service life of membranes
o Approximately 8 years
Residuals Management
The concentrate is disposed to an on-site leach field.
Technology Benefits and Drawbacks
Benefits
 Effectively removes nitrate and other cocontaminants
 On-site concentrate disposal
 Consistent operations
Drawbacks
 Energy intensive
 Relatively low water efficiency (80%)
Treatment Technology Costs
Treatment technology costs are not available for this system.
Operational Notes
The RO system has never had any extended unplanned shut downs or been shut down as the result of an alarm.
There has been an exceedance of the fluoride MCL that occurred near the end of the useful life of the membranes.
The membranes have since been replaced, resolving this operational issue.
References
Elyanow, D. and Persechino, J. (2005) Advances in Nitrate Removal. GE – General Electric Company, Water &
Process Technologies. Accessed June 11, 2010 via <
http://www.gewater.com/pdf/Technical%20Papers_Cust/Americas/English/TP1033EN.pdf>.
Technical Report 6: Drinking Water Treatment for Nitrate
59
System Name: City of Brighton
System Location: Brighton, CO
PWSID: CO 0101025
System Type: Community Water System
CASE #7
Treatment Type: Reverse Osmosis (RO)
Questionnaire completed by: Dave Anderson, City of Brighton RO Chief Plant Operator
Startup Date: 1993
System Description
Treatment Type
Reverse Osmosis
The City of Brighton (City) utilizes six
System Capacity
6.65 MGD (4,600 gpm)
groundwater wells with production
Raw Water Nitrate
49 – 89 mg/L as nitrate
capacities ranging from 900 to 1500
11 – 20 mg/L as N
gpm and one groundwater source
which has been designated as
groundwater under direct influence of surface water (GWUDI), as an emergency well, with a production capacity of
700 gpm. These seven sources are impacted by nitrate with average concentrations ranging from 49 to 89 mg/L of
nitrate as nitrate (11 to 20 mg/L of nitrate as N). The City has implemented RO with blending. The design capacity
of the RO system is 6.65 MGD of permeate at 80% recovery (1150 gpm/train). Green sand and cartridge filters
(Graver) are used to treat the GWUDI source, primarily for the removal of manganese. (Additional sources
operated by the City that are not impacted by nitrate are purchased treated surface water and additional GWUDI
wells.)
Raw water enters the system with 40% of feed water bypassing the RO system and 60% of feed water passing to
pretreatment. After anti-scalant addition, pretreated water is pressurized with boost pumps and passed to the RO
skids. Waste concentrate exits the system for disposal and post-treatment of the permeate includes CO2 stripping
and the addition of chlorine and caustic. Post-treated water is blended with bypassed water and sent to storage
and ultimately distribution.
Source Water Quality


Nitrate - mg/L as nitrate (mg/L N)
o Average - 46.9 to 90.3 (10.6 to 20.4)
o Minimum - 20.02 to 69.97 (4.52 to
15.8)
o Maximum - 78.8 to 112.9 (17.8 to
25.5)
Co-contaminants
o TDS: 580 to 1000 mg/L, RO TDS ~34
mg/L, Finished TDS ~280 mg/L
o Fluoride: 1.3 mg/L
o TOC: < 2 mg/L
o Hardness: 370 – 480 mg/L as CaCO3
(historically, Cevaal et al. 1995)
Technical Report 6: Drinking Water Treatment for Nitrate
60
Treatment Technology Selection
IX and EDR were also considered and pilot tested prior to installation of the RO system. RO was selected due to
nitrate levels and hardness. IX could have been less costly; however, the lower salt levels in RO concentrate make
it possible to discharge waste to the South Platte River. “By selecting RO, the City hoped to actually reduce the salt
load on the river with RO since many Brighton residents currently using home ion-exchange softening units would
no longer use them” (Cevaal et al. 1995, p. 102). Biological treatment is also being explored for the treatment of
nitrate in the waste brine.
Residuals Management
The waste concentrate is continuously discharged via a brine line to the South Platte River. Biological treatment is
being explored for the treatment of the waste concentrate. The biological system would be located on the West
side of the RO treatment system and would allow for reduction of nitrate in the waste stream. As mentioned
above, the use of RO rather than ion exchange was an effort to decrease salt loading to the South Platte River.
Historically, Brighton residents used in-home ion exchange units to soften water.
Technology Benefits and Drawbacks
Benefits
 Consistent treatment performance
 Ease of operation
Technical Report 6: Drinking Water Treatment for Nitrate
Drawbacks
 Constant generation of waste stream
 High power consumption
61
Treatment System Parameters
 Design Capacity
o 6.65 MGD of permeate at 80%
recovery (1150 gpm/train)
 Pretreatment/Post-treatment
o Anti-scalant:
King Lee Technologies
Pre Treat Plus 0100 phosphonate
o 5 micron cartridge filters
 2.5 inch diameter
 90 day replacement
o pH adjustment
 caustic soda (NaOH)
 Air stripping (CO2 removal)
 Treatment system footprint
o Treatment system:
11,000 sq. ft. at installation
(Cevaal et al. 1995)
 Number of contactors
o 2 stages, 5 trains
o RO elements/stage
 36 x 18 array
 6 membranes/vessel
 324 total
 Max. Concentration goal for delivered water
o 35.4 mg/L as nitrate (8 mg/L as N),
(always produce lower)
 Rejection Rate
o 95 – 98% rejection
o Nitrate goal (before blending):
~4.4 mg/L as nitrate (~1 mg/L as N)







Flux rate of the RO membranes
o 13 gpd/sf
System Manufacturer
o Hydranautics and Hydrocode
Membrane Type
o CPA2 (no others used in past)
Membrane Life
o Unknown, none have required
replacement (5 yrs. ago, the
manufacturer said the
membranes should last 3 more
yrs.).
Membrane Cleaning
o Clean in Place initiated by time
rather than decrease in flux.
Every ~157 million gals treated
(~2x/yr)
o Chemicals:
Nalco Product and Citric acid
Waste
o Discharge via Brine line to South
Platte River
o Recovery Rate: 80%
Monitoring
o Ion chromatography
 At Source
 At Point-of-Exit
o Grab ISE (HACH)
 At Blending Point
 At Point-of-Exit
o Testing once per year is required
for compliance
Treatment Technology Costs
Capital Costs (Total with explanation or component costs)
Operating and Monitoring
$8,253,000 (1993) 4MGD RO facility
Equipment:
Annual O & M Costs (Total with explanation or component costs)
Total:
$2,873,293.00
Membrane:
0
Membrane Disposal:
0
Brine Disposal or Treatment:
0
Chemicals:
Approx. $100,000 year
Power:
Approx. $210,000 year for RO
Labor (Hours per Year):
10 hr/day, 7 day/wk
2 MGD Thornton treated:
$3.60/1000 gallons
COMPLETE Cost (including
treatment, distribution,
$3.16/1000 gallons
everything):
Technical Report 6: Drinking Water Treatment for Nitrate
62
Additional Information






The level of certification required for plant operators is Colorado A treatment.
During a power outage, there is a pause before the generators start. This requires a manual restart of the
system.
This system has never produced water exceeding the nitrate MCL and has never had an unplanned
shutdown exceeding one week.
The major benefit of the RO system is the rejection rate allowing for removal of regulated contaminants.
The most significant disadvantages are the high power consumption and the continuous brine discharge.
The operator also noted that there has been a decreasing trend in nitrate levels in their sources.
References
Cevaal, J.N., Suratt, W.B., and Burke, J.E. (1995) Nitrate removal and water quality improvements with reverse
osmosis for Brighton, Colorado. Desalination, 103, 101 – 111.
Anderson, D. (2010) In-person interview and tour of the facility. July 19, 2010.
Anderson, D. (2010) Completed questionnaire. September 15, 2010.
Technical Report 6: Drinking Water Treatment for Nitrate
63
System Name: Western Municipal Water District - Arlington Desalter
System Location: Riverside, CA
PWSID: CA3310049
CASE #8
System Type: Community Water System
Treatment Type: Reverse Osmosis (RO) and Blending
Questionnaire completed by: Joseph Bernosky, Director of Engineering
Startup Date: 1990 strictly for desalting, Upgraded to drinking water treatment in 2002
System Description
The Western Municipal Water
Treatment Type
Reverse Osmosis and Blending
District (District) operates a system
System Capacity
6.6 MGD (4,600 gpm)
comprised of seven wells, five of
Raw Water Nitrate
44 – 89 mg/L as nitrate
which contain nitrate above the
10 – 20 mg/L as N
MCL. Three of the nitrate impacted
wells are treated by a 6.6 MGD RO
facility. The permeate, or treated water, from the RO system is blended with the remaining two wells prior to
distribution. The RO and blending facilities are collectively referred to as the Arlington Desalter. Approximately
60% of the total flow is treated by the RO system and the remaining 40% is blended with the treated water. The
District targets a nitrate concentration of 22 mg/L as nitrate (5 mg/L as N) in the distribution system.
The Arlington Desalter facilities were originally installed in 1990 to address the salt imbalance in the Upper Santa
Ana Watershed. High salinity waters withdrawn from the South Arlington Basin were treated by the Arlington
Desalter and subsequently discharged to the Santa Ana River for downstream use (and downstream drinking water
treatment). The system was upgraded to a drinking water treatment facility in 2002 with the addition of
disinfection, a clear well and a pump station used to pump drinking water into the distribution system for the city
of Norco, CA.
Source Water Quality

Nitrate - mg/L as nitrate (mg/L N)
o Average - 75 (17)
o Minimum - 44 (10)
o Maximum - 89 (20)

Co-contaminants
o TDS - 1200 mg/L
Treatment Technology Selection
Due to the original intent of the system and the 2002 conversion for drinking water production, no other
technologies were pilot tested prior to the installation of the RO and blending facilities. However, biological
treatment of RO bypass water was recently pilot tested with full-scale implementation anticipated. A case study
about this fixed bed biological pilot study is listed separately.
Technical Report 6: Drinking Water Treatment for Nitrate
64
Treatment System Parameters






Design Capacity: 6.6 MGD
Pretreatment/Post-treatment
o Anti-scalant: Y2K Anti-scalant
Treatment system footprint
o Treatment system:
2
Approximately 7,500 ft excluding
clear well and pump station
Number of Stages
o Stage 1: 36 vessels each with 6
units
o Stage 2: 12 vessels each with 6
units
Max. Concentration goal for delivered
water
o 22 mg/L as nitrate (5 mg/L as N)
Water Recovery
o Original design: 75 – 76%
o Current: 80%







Flux rate of the RO membranes
2
o 16 gpd/ft
System Manufacturer
o Hydranautics
Membrane Type
o Koch HR400
Membrane Life
o > 10 years
Membrane Cleaning
o Occurs 2 times per year
o Chemicals: Low pH solution,
hydrofluorosilic acid, high pH
solution
Waste: The RO concentrate is disposed of
offshore via the Santa Ana Regional
Interceptor (SARI) brine line
Monitoring
o Ion chromatography
o Online nitrate analyzers
Residuals Management
Waste is discharged to the Santa Ana Regional Interceptor (SARI) (Brine Line). The SARI line prevents degradation
of natural waters caused by increased salinity. Managed by the Santa Ana Watershed Project Authority (SAWPA),
the SARI line is a dedicated interceptor line built to help users meet discharge requirements. In addition to the
Arlington Desalter, the SARI line is used by other dischargers including industrial and domestic sources. The
District’s contribution to the total flow of the SARI line is approximately 5%. The SARI line carries water to the
Orange County Sanitary District for wastewater treatment with ultimate offshore discharge.
Having access to the SARI line for brine disposal is a benefit of this system; however, there have been
complications with the SARI line. Tremendous scaling problems in Arlington Desalter’s reach of the SARI line have
resulted in the need to address calcium carbonate buildup and to consider additional cleanout points. Due to
multiple discharge sources, the SARI line combines waters having very different water quality characteristics.
Reactions within the mixed water can vary based on water chemistry. Several cleaning and maintenance options
are being considered.
Technology Benefits and Drawbacks
Benefits
 Reliable
 Access to SARI line for disposal
 The treatment potential of the pre-existing
RO system has been maximized through
conversion for drinking water treatment
Technical Report 6: Drinking Water Treatment for Nitrate
Drawbacks
 Costly brine disposal
 Complications with SARI line (scaling, etc.)
65
Treatment Technology Costs
Capital Costs (Total with explanation or component costs)
Total Capital Costs:
Unavailable for initial installation in 1990
Annual O&M Costs (Total with explanation or component costs) (2009/2010)
Total:
$2,931,228
Labor and Overhead:
$836,530
Outside Services:
$200,000
Emergency Repairs:
$25,000
General & Administrative:
$85,000
Vehicle and Equipment:
$9,000
SARI Fixed Cost:
$151,800
Materials and Supplies:
$5,500
Permits and Fees:
$27,000
SARI Variable Cost:
$470,000
Chemicals:
$150,000
Energy:
$971,398
Additional Information
Regarding water recovery, the original design recovery rate was 75 – 76%. With modifications to anti-scalant use,
the recovery rate increased to 78% and then to the current operational water recovery rate of 80%. To further
improve the water recovery rate, additional testing is anticipated which will require engineering work and a costbenefit analysis.
Currently used membranes are 10 years old and are still performing adequately with respect to operational
parameters (flux rate, rejection rate, etc.). The District has budgeted for membrane replacement in this fiscal year;
however, due to adequate performance, the current membranes may be used for an additional year. Membranes
are actually attaining better water recovery than manufacturer specifications. Membrane life is also exceeding
initial expectations.
Sources*
Bernosky, J. (2010) Personal communication. November 5, 2010.
Bernosky, J. (2010) Completed questionnaire. October, 2010.
*Unpublished sources used in the development of the case studies are not reflected in the References section of this
report.
Technical Report 6: Drinking Water Treatment for Nitrate
66
System Name: Chino Basin Desalter Authority (CDA) – Chino I Desalter
System Location: Chino, CA
PWSID: CA31610075
CASE #9
System Type: Community Water System
Treatment Type: Reverse Osmosis (RO) and Ion Exchange (IX)
Questionnaire completed by: Timothy Mim Mack, CDA Coordinator, City of Ontario
René Cruz, Engineering Project Manager, Project Partners Inc., serving the (CDA).
Startup Date: RO in 2000, IX added in 2005
System Description
Treatment Type
Reverse Osmosis,
Ion Exchange
And Blending
RO: 4940 gpm
IX: 3400 gpm
147 – 303 mg/L as nitrate
33 – 68 mg/L as N
The Chino Basin Desalter Authority (CDA) in
southern California is a conglomerate of the
System Capacity
following agencies: Inland Empire Utilities
Agency (IEUA), Jurupa Community Services
District (JCSD), City of Chino, City of Chino Hills,
Raw Water Nitrate
City of Ontario, City of Norco, Santa Ana River
Water Company (SARWC), and Western
Municipal Water District (WMWD). The CDA drinking water treatment facilities include two desalters: Chino I
Desalter (discussed here) and the Chino II Desalter (discussed in the next case study) to address high TDS levels as
well as nitrate contamination. The Chino I Desalter operates 14 source wells, 11 of which have raw nitrate levels
well above the MCL. Treatment consists of a combination of RO, conventional anion exchange and blending. Sixty
percent of total flow is treated with RO, 27% with IX and 13% passes only through VOC/Air-stripping prior to
blending. The RO system was installed in 2000 and the IX system was added in 2005.
Source Water Quality

Nitrate - mg/L as nitrate (mg/L N) (of
nitrate impacted wells)
o Average: ~147 – 303 (~33 – 68)
o Minimum: ~114 – 289 (~26 – 65)
o Maximum: ~161 – 351 (~36 – 79)

Co-contaminants
o TDS: 1100 mg/L
Treatment Technology Selection
RO and IX were selected because, combined, they were determined to be the best mode of technology to
adequately treat the high-TDS, high-nitrate source water. No other technologies were pilot tested or considered
prior to the installation of the system.
Technical Report 6: Drinking Water Treatment for Nitrate
67
Treatment System Parameters











Design Capacity
o RO: 4940 gpm
o IX: 3400 gpm
Pretreatment
o Anti-scalant: threshold inhibitor
o Filtration: 1 micron pre-filters
o pH adjustment: sulfuric acid
Post-treatment
o pH adjustment: sodium hydroxide
Treatment system footprint
o RO system: 143’ X 80’
o IX system: 190’ X 60’
Number of contactors
o 4 trains, 2 stages/train
o RO elements/stage
 stage 1: 196 elements
 stage 2: 98 elements
Ion exchange pressure vessels
o Number of vessels: 4
o Diameter of vessels: 12’
o Height of vessels: 11’
2
Design Loading Rate: 1.66 gpm/ft
Max. nitrate concentration goal for
delivered water: 36 mg/L as nitrate (8.13
mg/L as N)
Nitrate concentration goal for the
treatment system (before blending): 10
mg/L as nitrate (2.25 mg/L as N)
RO recovery rate: 80%
RO membrane flux rate: 0.9 gfd/psi










System Manufacturer
o RO: Code-line
o IX: Hungerford and Terry
Membrane Type: Dow 400 BW-30
Membrane Life: 5 years
Membrane Cleaning
o Flux decrease initiates CIP
o Every 6 month
o Chemicals: for pH adjustment
based on manufacturer
recommendation
Resin Type: Rohm and Hass Amberjet
4400 CL SBA
Volume treated prior to regeneration
o 700,000 gallons
o Regeneration once every 12 hrs
Salt consumption: 75 tons per week
Volume of brine/backwash
o 53,000 gallons
o 92.4% water efficiency
Resin life: Has not been replaced (online
for 5 years)
Monitoring
o Online nitrate analyzers
 Treatment train
 Blending point
 POE
o Laboratory samples
o Quarterly testing for NDMA
Residuals Management
Concentrate/brine is discharged into a regional brine line called the Inland Empire Brine Line (IEBL) and formerly
known as the Santa Ana Regional Interceptor (SARI).
Technology Benefits and Drawbacks
Benefits
 RO provides better removal
 IX is inexpensive
 IX has very low energy demands
Technical Report 6: Drinking Water Treatment for Nitrate
Drawbacks
 RO is expensive
 High waste rate of RO
 IX does not address TDS
 Resin replacement will be costly
68
Treatment Technology Costs
Capital Costs (Based on projected costs in 2004)
Treatment Plant Expansion Total (5000
afy expansion):
Ion Exchange Treatment (4.9 MGD):
Onsite Modifications:
SARI Discharge Upgrades & Storm Drain:
Additional SARI Capacity Purchase (not
included in above total):
$6,379,530
$4,031,900
$1,735,000
$612,630
$4,140,000
O & M Costs
(Based on CDA 2010/11 Budget, for complete plant operation, not just the treatment system)
Total:
$7,496,315
Chemicals:
$662,257
Electricity, Plant Total:
$2,843,000
Operating Fees:
$1,353,439 (includes SARI fees, permits and other fees)
Labor ($):
$1,370,698
Additional Information



The RO treatment system is described as falling short of expectations with respect to the high waste rate.
15% of all incoming water is sent to the brine line and delivered to a treatment plant outside of the local
watershed at the Orange County Sanitation District.
Plant shutdown has been required in the past due to high or low pressure, high nitrate, and high TDS.
In the event of insufficient treatment and the production of water in exceedance of an MCL, the plant has
an MOV that closes automatically, sending water to a storm drain.
Sources*
Listed costs are based on:
Chino Basin Desalter Authority. (2005) Presentation: Chino I Desalter Expansion & Chino II Desalter Project
Update.
Chino Basin Desalter Authority. (2010) Fiscal Year 2010/11 Budget Adoption.
*Unpublished sources used in the development of the case studies are not reflected in the References section of this
report.
Technical Report 6: Drinking Water Treatment for Nitrate
69
System Name: Chino Basin Desalter Authority (CDA) – Chino II Desalter
System Location: Mira Loma, CA
PWSID: CA3310083
CASE #10
System Type: Community Water System
Treatment Type: Reverse Osmosis (RO) and Ion Exchange (IX)
Questionnaire completed by: Timothy Mim Mack, CDA Coordinator, City of Ontario
René Cruz, Engineering Project Manager, Project Partners Inc., serving the (CDA).
Startup Date: 2006
System Description
Treatment Type
Reverse Osmosis,
The Chino Basin Desalter Authority (CDA) in
Ion Exchange
southern California is a conglomerate of the
And Blending
following agencies: Inland Empire Utilities
System Capacity
RO: 4167 gpm
Agency (IEUA), Jurupa Community Services
District (JCSD), City of Chino, City of Chino Hills,
IX: 2778 gpm
City of Ontario, City of Norco, Santa Ana River
Raw Water Nitrate
70 – 224 mg/L as nitrate
Water Company (SARWC), and Western
16 – 51 mg/L as N
Municipal Water District (WMWD). The CDA
drinking water treatment facilities include two desalters: Chino I Desalter (discussed above) and the Chino II
Desalter (discussed here) to address high TDS levels as well as nitrate contamination. The Chino II Desalter
operates 8 source wells, all of which have raw nitrate levels well above the MCL. Treatment consists of a
combination of RO, conventional anion exchange, and blending. The combined RO/IX system was installed in
2006.
Source Water Quality

Nitrate - mg/L as nitrate (mg/L N) (of
nitrate impacted wells)
o Average: ~70 – 224 (~16 – 51)
o Minimum: ~53 – 190 (~12 – 43)
o Maximum: ~81 – 260 (~18 – 59)

Co-contaminants
o TDS
Treatment Technology Selection
RO and IX were selected because, combined, they were determined to be the best mode of technology to
adequately treat the high-TDS, high-nitrate source water. No other technologies were pilot tested or considered
prior to the installation of the system.
Technical Report 6: Drinking Water Treatment for Nitrate
70
Treatment System Parameters










Design Capacity
o RO: 4167 gpm
o IX: 2778 gpm
Pretreatment
o Anti-scalant: threshold inhibitor
o Filtration: 1 micron pre-filters
o pH adjustment: sulfuric acid
Post-treatment
o pH adjustment: sodium hydroxide
Treatment system footprint
o RO system: 30’X 188’
o IX system: 30’ X 188’
o Total system: 60’ X 300’
Number of contactors
o 3 trains
o 48 vessels/train
o RO elements/stage:
 7 elements per stage
Ion exchange pressure vessels
o Number of vessels: 4
2
Design Loading Rate: 10.1 gpm/ft
Max. nitrate concentration goal for
delivered water: 25 mg/L as nitrate (5.7
mg/L as N) (goal), 35 mg/L as nitrate (7.9
mg/L as N) (max.)
Nitrate concentration goal for the
treatment system (before blending): 4 mg/L
as nitrate (0.9 mg/L as N)
RO membrane flux rate: 0.30 – 1.70 gfd/psi










System Manufacturer
o RO: PROTEC Bekaert
o IX: Hungerford and Terry
Membrane Type: Dow/Filmtec Model
BW30-400
Membrane Life: ~5 years
Membrane Cleaning
o Flux decrease initiates CIP
o Every 6 months to 1X per year
o Chemicals: King Lee (antiscalant), high/low pH, Silica
Cleaner
Resin Type: Rohm and Hass Amberjet
4400 CL SBA
Volume treated prior to regeneration
o 0.8 – 1.4 MGD
o Regeneration is based on nitrate
levels
Salt consumption: 50 tons per week
Volume of brine/backwash
o NA
Resin life: NA
Monitoring
o Online nitrate analyzers
 At source
 Blending point
 POE
o Laboratory samples
Residuals Management
Concentrate/brine is discharged to an industrial sewer that drains to the Inland Empire Brine Line (IEBL). Waste is
transported 45 miles to the Orange County Sanitation District.
Technology Benefits and Drawbacks
Benefits
 RO works well for nitrate removal
 IX is less expensive
Technical Report 6: Drinking Water Treatment for Nitrate
Drawbacks
 RO is expensive
 IX does not accomplish contaminant
removal as well as RO
71
Treatment Technology Costs
Capital Costs (Based on projected costs in 2004)
Treatment Plant Total (10,400 AFY):
Ion Exchange Treatment:
Chino II Desalter:
RO Membranes:
Ion Exchange Land (not included in
above total):
Ion Exchange SARI Fee (not included in
above total):
$19,171,837
$4,346,900
$14,284,500
$540,437
$1,730,138
$10,105,000
O & M Costs
(Based on CDA 2010/11 Budget, for complete plant operation, not just the treatment system)
Total:
$6,111,799
Chemicals:
$615,000
Electricity – Plant Total:
$2,331,000
Operating Fees:
$706,154 (includes SARI fees, permits and other fees)
Labor ($):
$1,133,615
Additional Information
 Operator certification levels range from T-3 to T-5.
 Plant shutdown has been required in the past due to chemical pump failure and a high clearwell.
 Overall the combined system is described as working well but at a high price.
Sources*
Listed costs are based on:
Chino Basin Desalter Authority. (2005) Presentation: Chino I Desalter Expansion & Chino II Desalter Project
Update.
Chino Basin Desalter Authority. (2010) Fiscal Year 2010/11 Budget Adoption.
*Unpublished sources used in the development of the case studies are not reflected in the References section of this
report.
Technical Report 6: Drinking Water Treatment for Nitrate
72
3.3 Electrodialysis (ED/EDR/SED)
The use of electrodialysis (ED), including electrodialysis reversal (EDR) and selective electrodialysis (SED),
in potable water treatment (Figure 10) has increased in recent years, offering the potential for improved
water recovery, the ability to selectively remove nitrate ions, and the minimization of chemical and
energy requirements (Kneifel & Luhrs 1988; Kapoor & Viraraghavan 1997; Hell et al. 1998; Koparal &
Ogutveren 2002; Midaoui et al. 2002; Sahli et al. 2008; Banasiak & Schafer 2009).
Figure 10. Electrodialysis reversal schematic.
Nitrate removal is accomplished by passing an electrical current through a series or stack of anion and
cation exchange membranes, resulting in the movement of ions from the feed solution to a
concentrated waste stream. Illustrated in Figure 11, nitrate ions (and other anions) move through the
anion exchange membrane toward the anode. Continuing toward the anode, nitrate is rejected by the
anion-impermeable cation exchange membrane and trapped in the recycled waste stream. Cations can
be removed in a similar manner, migrating toward the cathode through the cation exchange membrane
and rejected by the cation-impermeable anion exchange membrane. Nitrate selective membranes allow
for treatment without significantly altering the balance of other ions in the water.
The electrical current is passed through the system with the migration of ions across the membranes.
For every anion that leaves a compartment, a cation of equivalent charge also leaves, maintaining the
charge balance in each compartment. Across the system, the flow of electrons, moving from the
cathode to the anode (negative to positive), is governed by the movement of ions through the
membrane stack and by the reactions in the electrode compartment. Small levels of gaseous
byproducts must be removed. Electrolysis of water generates oxygen at the anode and hydrogen gas at
the cathode and chloride can be reduced at the anode, producing chlorine gas (AWWA 1995). The
electrode compartment is rinsed to restore ions for current transfer and to remove unwanted reaction
products.
Technical Report 6: Drinking Water Treatment for Nitrate
73
Figure 11. Illustration of electrodialysis membrane stack.
Requiring constant electrical current and low-pressure water, ED has inherent energy demands.
However, voltage adjustment enables selective demineralization. “Plants can be designed to remove
from 50 to 99 percent of source water contaminants or dissolved solids. Source water salinities of less
than 100 mg/L up to 12,000 mg/L TDS can be successfully treated to produce finished water of less than
10 mg/L” (AWWA 1995, p. 7).
A detailed case study of an EDR plant in Spain is included in section 3.3.6 Electrodialysis - Case Studies.
Technical Report 6: Drinking Water Treatment for Nitrate
74
3.3.1 Electrodialysis - Design Considerations
Table 8 summarizes key design considerations in the use of ED for nitrate removal from potable water.
Table 8. Summary of design considerations for electrodialysis/electrodialysis reversal.
Membranes
Pretreatment






Chemical Usage







O&M

Post-Treatment





System
Components

Waste
Management and
Disposal




Limitations


Use of anion and cation exchange membranes
Selective membranes
o Monovalent versus multivalent
Consider water recovery and frequency of cleaning
Lower pretreatment requirements because this is not direct filtration
EDR systems can avoid or limit chemical use
Prevention of scaling and fouling
o Filtration to remove suspended solids
o Treatment for iron and manganese removal
o Water softening or use of anti-scalants or acid to prevent scaling
pH adjustment to avoid corrosion (if acid used to prevent scaling)
Disinfection
Possible pH adjustment (acids and bases)
Possible anti-scalants
Possible cleaning chemicals
Highly automated
Frequency of membrane cleaning depends on water quality and membrane used
o Polarity reversal (electrodialysis reversal) multiple times per hour
minimizes fouling
o ED systems can require weekly cleaning
Management of chemicals and pre-filtration system
o Including electrode compartment rinse solution
Waste storage and disposal
High monitoring demands
Potentially higher operator demand than IX and RO, due to system complexity
Maximize water recovery while minimizing energy use
Key aspects of the system are pretreatment requirements, number and
configuration of electrodialysis stacks and stages, membrane selection and
configuration, operating voltage and pressure, reversal frequency (for EDR), gas
venting of anode and cathode compartments, disinfection, “brine loop, electrode
rinse loop, concentrate discharge, and dosing station” (Hell et al. 1998, p. 178).
Concentrate disposal of greatest concern for inland systems
o Close proximity to coastal waters is beneficial for brine/concentrate
disposal
Management options include sewer or septic system, reuse for irrigation, drying
beds, trucking off-site, coastal pipeline, deep well injection and advanced
treatment
Disposal options can be limited by waste brine/concentrate water quality (e.g.,
volume, salinity, metals, and radionuclides)
Optimization of recycling and treatment of waste concentrate
Need to prevent membrane scaling and fouling
o Hardness, iron, manganese, and suspended solids
Disposal of waste concentrate
High system complexity
Technical Report 6: Drinking Water Treatment for Nitrate
75
Water Quality
Membrane life, cleaning frequency, and pretreatment needs are dependent on feed water quality.
Pretreatment may be needed for iron levels above 0.3 mg/L, manganese levels above 0.1 mg/L, and
hydrogen sulfide levels exceeding 0.3 mg/L (WA DOH 2005). Specifications for an example EDR system
from GE indicate feed water turbidity levels should be < 0.5 nephelometric turbidity units (NTU) with
typical TDS levels between 100 and 3,000 mg/L (maximum 12,000 mg/L) (GE 2008). SDI limits are
generally higher for EDR than for RO, with typical limits of 12 and 4 – 5, respectively (Elyanow &
Pereschino 2005). Softening may be necessary to reduce hardness, while pre-filtration diminishes
suspended solids. The potential for scaling increases with increasing TDS and is exacerbated by
increased solids precipitation with higher water recovery goals. To minimize fouling/scaling,
membranes can be treated with anti-scaling chemicals and cleaned with acid (AWWA 1995). However,
in comparison with other membrane processes, fouling is minimal because the membrane is subjected
to the transfer of ions (directed by the electrical current), rather than the transfer of the entire feed
stream. Unfortunately, because ED does not serve as a filter (the water does not pass through the
membrane), ED fails to remove microbial contamination (AWWA 1995). Pre-filtration in pretreatment
and disinfection in post-treatment address these concerns.
To further minimize fouling and thus the need for chemical addition, the polarity of the system can be
reversed with electrodialysis reversal (EDR). By reversing the polarity (and the solution flow direction)
several times per hour, ions move in the opposite direction through the membranes, minimizing buildup
and the need for chemical addition to control scaling. Biological fouling concerns are lower than other
separation processes due to development of membranes that are “more organic resistant and chlorine
tolerant” (Elyanow & Persechino 2005, p. 8). ED depends on the transfer of an electrical current and is
therefore more efficient when used for brackish waters. In low conductivity feed waters, the ion
removal efficiency declines. In contrast to conventional RO, EDR is unaffected by silica.
System Components and Site Considerations
ED and EDR systems are operated in stages. Water recovery can be improved with stages operated in
series while capacity can be increased with stages operated in parallel. Key aspects of the system are
pretreatment requirements, the number and configuration of electrodialysis stacks and stages,
membrane selection and configuration, operating voltage (based on desired removal), reversal
frequency (for EDR), gas venting of the anode and cathode compartments, disinfection, “brine loop,
electrode rinse loop, concentrate discharge, and dosing station” (Hell et al. 1998, p. 178).
The membranes used in ED/EDR are anion and cation exchange membranes. Membranes have been
designed for selective removal based on valency (monovalent versus multivalent) to screen for
particular constituents (AWWA 1995). Alternating different selective membranes in the membrane
stages can avoid precipitation in the concentrate stream. For example, one stage can remove calcium
and a second stage can remove sulfate (to an alternate concentrate stream), this prevents calcium
sulfate precipitation (AWWA 1995).
Technical Report 6: Drinking Water Treatment for Nitrate
76
Residuals Management and Disposal
Waste management requirements are similar to RO and IX; however, the burden of disposal in ED/EDR
systems is not as significant due to higher water recovery, selective removal, and the lack of direct
filtration (Reahl 2006). Disposal options include sewers, septic systems, drying beds, off-site trucking,
coastal pipeline, deep well injection, reuse for irrigation, and advanced treatment. Important water
quality characteristics of the concentrate (e.g., volume, salinity, metals, and radionuclides) can affect the
feasibility and costs of disposal options. Several combined configurations of interest are discussed in
Section 3.6 Brine Treatment Alternatives and Hybrid Treatment Systems.
Maintenance, Monitoring, and Operational Complexity
Although ED/EDR systems are amenable to automation, operator demands can be higher than other
separation processes (AWWA 1995). While ED systems have greater pretreatment demands and can
require membrane cleaning once a week, EDR systems minimize pretreatment demands and scaling
issues, but can still have higher maintenance demands than RO, due to the complexity of the system
(Kapoor & Viraraghavan 1997). Appropriate gas venting is important to avoid hazardous conditions
(AWWA 1995). Membrane life will depend on water quality and pretreatment measures. However, due
to the lack of direct filtration and operation under low pressure, membranes are long lasting, and do not
require frequent replacement.
3.3.2 Electrodialysis - Cost Considerations
For the efficient operation of an ED system, the fundamental objective is to maximize water recovery
with the minimum amount of energy and chemical usage, while meeting necessary potable water
guidelines. Factors affecting system cost include facility size (how much water), source water quality
(including nitrate concentration and other contaminants), target effluent nitrate concentration, and
disposal options.
Capital costs for ED/EDR systems include land, housing, piping, storage tanks, O&M equipment, cation
and anion exchange membranes, preliminary testing (pilot studies), permits, and training. O&M costs
include membrane replacement, membrane disposal, concentrate disposal or treatment, chemical use
(limited: anti-scalant, etc.), repair, maintenance, power, and labor.
Very little published cost information from existing ED systems used for nitrate removal is available in
the literature, due to the limited number of full-scale systems. Costs of ED systems are most
comparable to RO. However, in some instances, ED can be the less costly choice due to the greater
pretreatment and post-treatment demands (higher chemical use and post-treatment pH adjustment) of
RO (Reahl 2006). EDR can be chosen over RO when high water recovery is a priority, especially if land
must be purchased for concentrate ponds. “New technology has also reduced the capital and operating
cost of EDR nitrate removal by increasing the hydraulic efficiency of the EDR stacks and pumping
system” (Elyanow & Persechino 2005, p. 8). Costs listed here have been adjusted to 2010 dollars, unless
indicated otherwise. In a technical paper from GE Water & Process Technologies (the primary supplier
Technical Report 6: Drinking Water Treatment for Nitrate
77
of EDR systems in the U.S.), Werner & Gottberg (2005) present O&M costs of an electrodialysis plant in
Suffolk, VA (not specifically for nitrate treatment) (Table 9). It is unclear how disposal costs were
included in this study. High water recovery in comparison with other removal processes and disposal of
waste concentrate to a nearby estuarine tributary would maintain low disposal costs (Werner &
Gottberg 2005). According to Ameridia, the American division of Eurodia Industrie (a manufacturer of
EDR systems), the capital investment for a nitrate treatment EDR unit for a ~0.5 MGD system (in 2005)
was $475,000 or $0.94 per gallon of daily capacity ($559,653 or $1.11 in 2010 dollars, respectively)
(Ameridia). However, additional capital costs are likely not included in this figure. A detailed discussion
of treatment costs is included in Section 6 Treatment Cost Analysis.
Table 9. Sample EDR O&M costs (from Werner & Gottberg 2005).
O&M Category
Fixed
Professional Services
Chemicals
Utilities
Maintenance
Membrane Replacement
Production (1997)
Total O&M Cost
1
EDR (/1000 gallons)1
$0.72 ($1.07 adjusted)
$0.06 ($0.09 adjusted)
$0.02 ($0.03 adjusted)
$0.21 ($0.31 adjusted)
$0.17 ($0.25 adjusted)
$0.23 ($0.34 adjusted)
827,339,440 gallons
$1.41 ($2.09 adjusted)
Costs adjusted from 1998 dollars to 2010 dollars.
The listed cost information is provided as an approximate range of costs for specific facilities. Costs for
implementing ED may be very different from those listed here. A thorough cost analysis of design
parameters for specific locations would be required for accurate cost estimation.
3.3.3 Electrodialysis - Selected Research
Much research on ED has focused on desalination applications. Table A.3 of the Appendix lists recent
studies relevant to nitrate removal from potable water and several examples of ED application.
Research is focused on the influence of co-contaminants on system performance and improvements in
exchange membranes, including nitrate selectivity.
3.3.4 Electrodialysis - Summary of Advantages and Disadvantages
A summary of advantages and disadvantages of ED in comparison with other treatment options is listed
in Table A.6 of the Appendix. Advantages of ED/EDR systems include low chemical usage, long lasting
membranes, selective removal of target species, flexibility in removal rate (through voltage control),
good water recovery rate, feasible automation, and multiple contaminant removal (Prato & Parent
1993; AWWA 1995; Hell et al. 1998; WA DOH 2005). With the ability to selectively remove multiple
contaminants, ED/EDR systems can be used to address the following constituents: TDS, total chromium,
chromium-6, arsenic, perchlorate, sodium, mercury, chloride, copper, sulfate, uranium, fluoride,
Technical Report 6: Drinking Water Treatment for Nitrate
78
nitrate/nitrite, iron, selenium, hardness, barium, bicarbonate, cadmium, and strontium (AWWA 1995
and GE 2010). Using current reversal, EDR offers additional advantages, improving system performance
by “detaching polarization films, breaking up freshly precipitated scale or seeds of scale before they can
cause damage, reducing slime formations on membrane surfaces, reducing problems associated with
the use of chemicals, and cleaning electrodes with acid automatically during anodic operation” (AWWA
1995, p. 9, 10). Additionally, in comparison with RO systems, EDR can treat waters with higher SDI,
silica, and chlorine levels (Elyanow & Persechino 2005).
Disadvantages of ED/EDR systems include the possible need for pretreatment to prevent membrane
scaling and fouling, waste disposal, high maintenance demands, costs (comparable to RO systems), the
need to vent gaseous byproducts, the potential for precipitation (especially for high water recovery),
high system complexity, and limited manufacturers with U.S. experience (e.g., GE is the primary source
of EDR systems for drinking water in the U.S.). Additionally, unlike RO, ED does not remove uncharged
constituents in the water.
3.3.5 Modifications to Electrodialysis
Selective Electrodialysis (SED)
Since 1997, selective electrodialysis (SED), developed by Shikun & Binui, formerly Nitron, Ltd., has been
successfully implemented throughout Israel, reducing national water costs by 55%. The manufacturer
indicates that SED offers high water recovery (up to 95%), thereby minimizing waste volume (Nitron
2010). The SED system is accepted by the U.S. EPA as a nitrate treatment option for large plants (Nitron
2009). While similar to traditional ED processes, SED utilizes nitrate selective membranes which have
been shown to increase operational performance when used for nitrate treatment.
The nitrate selective membranes used in the SED process have been shown to remove up to 70% of
nitrate from solution. At the same time, sulfate ions and carbonate ions, which have a tendency to
cause scaling issues in the concentrate stream of traditional ED/EDR and RO technologies, are more
readily rejected by the nitrate selective membranes used in the SED process. As a result, the scaling
potential is reduced in the concentrate stream. Since scaling problems are minimized, membrane
cleaning frequency, maintenance costs, and down time are reduced compared to traditional EDR
installations. Another important aspect of membrane selectivity is the energy efficiency of the process.
Energy efficiency is related to the extent of ion transfer in ED/EDR and SED technologies. In traditional
ED/EDR, energy use is less focused, resulting in the removal of many ions, including ions that do not
need to be addressed. SED specifically targets nitrate ions, avoiding energy use for the removal of nontarget ions and improving energy efficiency.
Pretreatment can be limited to filtration, energy efficiency is maximized due to low pressure operation
(2 – 4 bars, ~30 – ~60 psi), chemical use is limited to concentrate treatment, and low maintenance
demands are possible due to automation, remote monitoring and control, and infrequent cleaning. In
the SED process there is no change in the pH of the product water. This avoids the need for pH
adjustment or remineralization in post-treatment (Nitron 2009; Nitron 2010). Membranes are cleaned
Technical Report 6: Drinking Water Treatment for Nitrate
79
in place (CIP) for 1 hour every 4 – 6 months and membrane life is typically 7 – 10 years (Nitron 2010).
Additional advantages of SED include constant membrane performance, no chemical contact with
potable water, the simplicity of the system consisting of pre-filtration and membrane stacks (UV can be
added for disinfection), and a small footprint (Nitron 2009b). Potential drawbacks of SED include the
lack of full-scale application in the U.S. for nitrate removal from drinking water and, unlike RO, ED does
not remove uncharged constituents in the water.
A detailed case study of the use of SED for nitrate removal at locations in Israel is included in the
following section.
3.3.6 Electrodialysis - Case Studies
The following case studies provide detailed information on the design and operation of full-scale EDR
and SED treatment plants used for nitrate removal.
Technical Report 6: Drinking Water Treatment for Nitrate
80
CASE #11
Treatment Type: Electrodialysis Reversal (EDR)
Questionnaire completed by: GE Water & Process Technologies
Startup Date: 2007
System Description
Treatment Type
System Capacity
Raw Water Nitrate
System Name: Gandia EDR
System Location: Valencia, Spain
System Type: NA
Electrodialysis Reversal
2 systems at 4.7 MGD each
80 mg/L as nitrate
18 mg/L as N
Gandia is a tourist area on the
Mediterranean coast of Spain. The
area sees peak demand during the
summer months when the
population almost triples. The Spanish Legislature released royal Decree 140/2003 which changed the nitrate limit
to 50 mg/L as nitrate (11.3 mg/L as N). This new law required treatment of the existing system to achieve the new
nitrate limits. Additionally, the existing
well systems had deteriorated over
time, forcing the municipality to find
alternate wells to feed the community.
Upon analysis of the wells (old and
new), it was determined that the
nitrate levels were too high to meet the
drinking water standard. The well
samples had up to 80 mg/L as nitrate
(18.1 mg/L as N). Treatment was
necessary to produce acceptable levels
of nitrate in the product water. An
evaluation was conducted and EDR was
selected as the technology of choice for
the Gandia treatment plants. EDR
offered high recovery while effectively reducing the nitrate levels below 25 mg/L as nitrate (5.6 mg/L as N).
EDR was piloted on the wells to verify the nitrate removals and operating cost estimates for power requirements
and chemical consumption. The pilot study was successful, and the final systems were designed around 90% water
recovery with the overall nitrate removal of 73%.
Source Water Quality

Nitrate (mg/L N)
o < 80 mg/L as NO3
Treatment Technology Selection
EDR, Selective ED, and Reverse Osmosis were considered for treating the Gandia Wells. EDR was eventually
selected for the high recovery and reduced operating costs compared to RO. SED was ruled out based on the high
capital costs of the system.
Technical Report 6: Drinking Water Treatment for Nitrate
81
Treatment System Parameters



Design Capacity
o 3,260 gpm
EDR System
o No. of modules: 4
o Lines per module: 5
o Stages per line: 2
Water recovery rate
o 94.3%
Water Quality Results
The table below summarizes the water quality of the raw water, finished water, concentrate stream, and the total
waste from the Gandia EDR facility. Total waste includes concentrate blowdown, electrode waste, and off-spec
product from the system.
Ion
Raw
Water
Treated
Water
Percent
Removal
Concentrate
Stream
Total
Waste
Ca
Mg
Na
K
HCO3
SO4
Cl
NO3
TDS
pH
82
24
23
1.0
250
58
29
60
527
7.5
24.9
8.3
10
0.3
99.1
12.7
7.5
16.6
179.3
7.1
70%
65%
57%
70%
60%
78%
74%
72%
66%
772.6
213.7
180
9.2
2074.1
605.2
289.3
584.4
4728.6
8.3
544.3
151.0
128.1
6.5
1471.2
424.4
203.3
411.1
3339.8
8.1
Technology Benefits and Drawbacks
Benefits
 EDR membranes are chlorine tolerant,
providing means to control biological
growth.
 Relatively low operational expenditures:
o Membrane life expectancy is 15
years.
o Low chemical consumption
compared to other technologies.
o Lower energy consumption
compared to RO.
 High water recovery, small concentrate
stream for disposal compared to other
technologies.
Technical Report 6: Drinking Water Treatment for Nitrate
Drawbacks
 Higher capital cost than RO.
 System footprint larger than competitive
technologies.
82
Operating Costs
Capital costs for the EDR system were not provided.
O & M Costs (Total with explanation or component costs)
Unit
Cost
Labor:
$/1,000 gal
0.17
Energy:
$/1,000 gal
0.15
Maintenance:
$/1,000 gal
0.03
Chemicals:
$/1,000 gal
0.10
Consumables:
$/1,000 gal
0.19
Overhead:
Total:
$/1,000 gal
$/1,000 gal
0.04
0.67
Operational Notes
Operating costs were based on estimates prior to plant start-up. After four years of operating, the plant has not
replaced any membranes. In 2010, another facility (L’Eliana) was commissioned in the Valencia area for 2.9 MGD
production rate for nitrate removal using the EDR technology.
Sources*
Cháfer , V.S., Carbonell, J.S., and de Armas Torrent, J.C. Nitrate and Hardness Removal with Electrodialysis Reversal
(EDR) in Gandia, (Valencia, Spain).
*Unpublished sources used in the development of the case studies are not reflected in the References section of this
report.
Technical Report 6: Drinking Water Treatment for Nitrate
83
CASE #12
Treatment Type: Selective Electrodialysis (SED)
Questionnaire completed by: Shikun & Binui Environmental Group
Startup Date: 2008
System Description
Treatment Type
System Capacity
Raw Water Nitrate
System Name: Weizmann Institute
System Location: Rechovot, Israel
System Type: NA
Selective Electrodialysis
310 gpm
84 – 89 mg/L as nitrate
19 – 20 mg/L as N
The Weizmann Institute of Science
(Institute), located in Rechovot,
Israel, is one of the top-ranking
multidisciplinary research
institutions in the world. In 2007, the nitrate MCL in the Israeli National drinking water regulations changed from
90 mg/L (20.3 mg/L as N) to 70 mg/L (15.8 mg/L as N). Because of this change, two of the Institute's wells were
removed from the drinking water supply and the Institute had to rely on external water suppliers. Over time,
municipal and national water costs increased. The Institute’s management looked for solutions to solve nitrate
problems and enable them to reopen the Institute's wells.
Prior to treatment, the wells were used for potable purposes and the Institute’s irrigation needs. Selective
Electrodialysis (SED) was identified as the Institute’s most appropriate treatment technology. An SED system was
implemented for the 310 gpm well. The Institute opted for treatment of one well and uses the second well as a
dedicated irrigation supply source. The nitrate enriched concentrate from the SED process is fed into the nonpotable irrigation system where the nitrate enhances plant growth.
SED has been successfully implemented throughout Israel since 2007. Developed by Nitron, Ltd., SED offers high
water recovery (up to 95%), thereby minimizing waste volume. Pretreatment can generally be limited to filtration,
energy efficiency is maximized due to low pressure operation (30 – 60 psi), chemical use is limited to concentrate
treatment (no need for chemical addition to feed or product water), and low maintenance demands are possible
due to automation, remote monitoring and control and infrequent cleaning. Membranes are cleaned in place (CIP)
for 1 hour every 4 – 6 months and membrane life is typically 7 – 10 years.
Source Water Quality

Nitrate – mg/L as nitrate
(mg/L N)
o Average – 84 (19)
o Minimum – 84 (19)
o Maximum – 89 (20)
Treatment Technology Selection
SED and RO were considered for
treating the Weizmann Institute well.
A 10 year life cycle cost analysis that
included capital and operations costs
identified SED as the more costeffective solution.
Technical Report 6: Drinking Water Treatment for Nitrate
84
Treatment System Parameters




Design Capacity
o 310 gpm
Pretreatment
o Cartridge filtration
Post-treatment
o Chlorination
o Acid addition (pH 4.5 – 5) to
concentrate to prevent the
precipitation of calcium
carbonate and calcium sulfate in
the concentrate cells
Treatment system footprint
o Treatment system: 8’ x 5’
o Building footprint: Butler building
- 50’ x 13’ as per client request



Water recovery rate
o 94.3%
SED unit information:
o Number of SED units: 1
o Membrane pairs: 240
o 59% Nitrate reduction
o 30% TDS reduction
o Energy consumption: 2.3
KWh/1,000 gal
Monitoring:
o Online nitrate analyzer
o Laboratory nitrate samples
o Online pH meters
o Online turbidity
o Online conductivity meters
Water Quality Results
The table below summarizes the water quality of the raw water, finished water, and concentrate stream from the
Weizmann Institute.
Ion
Raw
Water
Treated
Water
Percent
Removal
Concentrate
Stream
Cl
SO4
HCO3
NO3
Na
Ca
Mg
K
Ba
Sr
TDS
pH
194
95
232
92
109
118
24
3.6
0.149
0.84
869
7.8
105
92
165
44
76
73
15
2.5
0.093
0.52
574
7.8
45.9%
3.0%
28.7%
52.2%
30.4%
37.8%
36.6%
30.6%
37.8%
37.8%
33.9%
2051
140
442
835
627
808
160
20.5
1.020
5.75
5090
6.5
Residuals Management
The concentrate from the SED process is fed into the Weizmann Institutes non-potable system which is used for
irrigation purposes. Since the SED process selectively removes nitrate, the Total Dissolved Solids (TDS) of the
concentrate is less than an RO system would be if it were treating the same water, which allows the concentrate to
be used for irrigation without the salinity adversely affecting plant growth. This management approach is also
beneficial since the concentrated nitrate solution has limited the amount of fertilizer applied by the Weizmann
Institute.
Technical Report 6: Drinking Water Treatment for Nitrate
85
Technology Benefits and Drawbacks
Benefits
 Ease of regeneration
 Fewer chemicals than comparable
technologies
 Membranes 7 – 10 year life span
 Energy consumption less than that of RO
 High water recovery
 Concentrate solution has relatively low
TDS which may increase disposal options
Drawbacks
 Capital intensive technology
 Requires specific operator training
Treatment Technology Costs
Capital Costs (Total with explanation or component costs)
$
650,000
Total:
Housing:
Piping:
50,000
Storage Tanks (include
description of uses):
Operating and Monitoring
Equipment:
Membranes Modules:
Permits:
90,000
Other:
210,000
Comments
Light building 50X13 feet. According to customer demands.
Pipes, electric valves, storage tanks (the largest would be with a
volume of about 180 cu. ft. for product water).
See above.
300,000
Control system, remote assistance for the control system, on line
nitrate measurement, conductivity, pH, turbidity.
Complete SED membrane stack.
According to local regulations.
Design; Electricity boards – design, manufacturing & installation;
Pumps and blowers.
O & M Costs (Total with explanation or component costs)
Unit
Membrane:
Concentrate Disposal or Treatment:
Chemicals:
Comments
%/year
10% per year is the replacement rate.
Gallons/year
Site specific; 4 – 5% of the SED system
capacity.
Total, [lb/1000 gallon]
0.77
Specific acid consumption
[lb/1000 gallon]
0.72
Specific chlorine consumption
[lb/1000 gallon]
0.04
Specific caustic soda consumption
[lb/1000 gallon]
0.01
$/year
7,000
Repair/Maintenance (not including
Labor):
Specific power consumption
[kWh/1000 gallon]
Labor ($):
Labor (Hours per Year):
Technical Report 6: Drinking Water Treatment for Nitrate
$
hours
1.4
16,000 (40$ per hour basis)
400
86
Operational Notes
The SED system is highly instrumented and the PLC has over 200 monitored inputs. As a result there have not
been any failures that have resulted in MCL violation. While there have been failures resulting in alarms and
shutdowns, the control system has been robust enough to shut down the system and prevent water with high
nitrate entering the distribution system. Typical shutdowns can be rectified in a matter of hours and normal
operation is resumed.
Sources*
Merhav, Neta. (2010) Completed questionnaire. October, 2010.
*Unpublished sources used in the development of the case studies are not reflected in the References section of this
report.
Technical Report 6: Drinking Water Treatment for Nitrate
87
3.4 Biological Denitrification (BD)
Commonly used in wastewater treatment, biological reactors are emerging as a method for
denitrification of potable water with the potential to address multiple contaminants including nitrate,
chromate, perchlorate, and trace organic chemicals (Brown 2008). Biological denitrification (BD) in
potable water treatment has been implemented in Europe since 1804 (Lenntech 2009), with recent fullscale systems in France, Germany, Austria, Poland, Italy, and Great Britain (Meyer 2009; Dördelmann
2009). To date, full-scale drinking water applications in the United Sates have been limited to a single
plant in Coyle, OK (no longer online). However, two full-scale biological denitrification systems are
anticipated in California within the next couple of years.
Denitrification occurs naturally in the environment as part of nitrogen cycling. Application of biological
denitrification to potable water treatment (Figure 12) utilizes denitrifying bacteria to reduce nitrate to
innocuous nitrogen gas in the absence of oxygen (anoxic conditions).
Figure 12. Biological denitrification schematic.
The reduction of nitrate proceeds stepwise in accordance with Eqn. 9. In contrast with the separation
processes of IX, RO, and ED/EDR, nitrate is reduced and thereby removed from the system rather than
simply being displaced to a concentrated waste stream.
NO3-  NO2-  NO  N2O  N2
(Eqn. 9)
Denitrifying bacteria require an electron donor (substrate) for the reduction of nitrate to nitrogen gas.
In conventional wastewater treatment, substrate addition is not typically needed, because the
wastewater contains sufficient carbon for denitrification to occur. However, depending on the source,
substrate addition is often required for the biological denitrification of potable water. The addition of a
carbon substrate in potable water treatment is somewhat counter intuitive. In fact, one principal
objective of potable water treatment is to minimize dissolved carbon in the water to minimize growth of
microbes (e.g., biofilms) and production of disinfectant byproducts (e.g., THMs). Feed water
composition may need to be further augmented with the addition of nutrients required for cell growth
(phosphorus for example). Autotrophic bacteria utilize sulfur or hydrogen as an electron donor and
inorganic carbon (typically carbon dioxide) as a carbon source for cell growth (Eqns. 10 and 11), while
heterotrophic bacteria consume an organic carbon substrate, like methanol, ethanol, or acetate (Eqn.
12) (Mateju et al. 1992; Kapoor & Viraraghavan 1997).
Technical Report 6: Drinking Water Treatment for Nitrate
88
Eqns. 10 through 12 illustrate the overall denitrification reaction defining the stoichiometric relationship
between electron donor, carbon source, and nitrate in the production of cells and the conversion of
nitrate to nitrogen gas. Not all nitrogen is converted to nitrogen gas. Some nitrogen is required for cell
growth. The governing stoichiometric equation indicates the necessary dose and varies with the
substrate used. For example, the stoichiometric factor for acetic acid is 0.82 moles of acetic acid per
mole of nitrate (Dördelmann et al. 2006).
11 S0 + 0.5 CO2 + 10 NO3- + 2.54 H2O + 1.71 NH4+
 0.92 C5H7O2N + 11 SO42-+ 5.4 N2 + 9.62 H+
(Eqn. 10)
H2 + 0.35 NO3- + 0.35 H+ + 0.052 CO2  0.010 C5H7O2N + 0.17 N2 + 1.1 H2O
(Eqn. 11)
1.08 CH3OH + NO3- + H+  0.065 C5H7O2N + 0.467 N2 + 0.76 CO2 + 2.44 H2O
(Eqn. 12)
Various species of bacteria are responsible for denitrification including Thiobacillis denitrificans,
Micrococcus denitrificans, Pseudomonas maltophilia and Pseudomonas putrefaciens (Kapoor &
Viraraghavan 1997). Due to slower bacterial growth rates, autotrophic denitrification offers the
advantage of minimizing biomass accumulation; however, autotrophic denitrification requires alkalinity
to supply the inorganic carbon source (carbon dioxide) for cell growth (Della Rocca et al. 2006).
BIODEN® and DENICARB® are heterotrophic biological denitrification processes, while DENITROPUR® is
an autotrophic option. Selected full-scale biological denitrification systems are listed in Table 10
(Dördelmann 2009).
Table 10. Full-scale biological denitrification systems for potable water treatment.
Location
Germany
Neuss
Frankfurt Airport
Aschaffenburg
Föhr Island
Austria
Obersiebenbrunn
Poland
Czestochowa
1
Dördelmann 2009.
1
Reactor Configuration
Substrate, Denitrification type
Flow rate
3
m /h (MGD)
Fixed bed, down-flow
Fluidized bed, up-flow, DENICARB®
Acetic acid, Heterotrophic
Ethanol, Heterotrophic
Hydrogen and CO2,
Autotrophic
150 (0.95)
320 (2.03)
1600 (10.14)
90 (0.57)
Fixed bed, down-flow, BIODEN®
Ethanol, Heterotrophic
180 (1.14)
Fixed bed, down-flow, BIODEN®
Ethanol, Heterotrophic
500 (3.17)
Fixed bed, up-flow, DENITROPUR®
In their review of potable water treatment methods for the removal of nitrate, Mateju et al. (1992),
Kapoor & Viraraghavan (1997), Soares (2000), and Shrimali & Singh (2001) discuss previous research and
applications of biological denitrification. Problems associated with the application of conventional
biological denitrification to potable water treatment include additional post-treatment for removal of
biomass and dissolved organics, the potential for incomplete denitrification, increased capital costs, and
sensitivity to environmental conditions (Kapoor & Viraraghavan 1997). To address these concerns,
several treatment configurations using biological denitrification have been developed.
Technical Report 6: Drinking Water Treatment for Nitrate
89
3.4.1 Biological Denitrification - Design Considerations
Table 11 summarizes key design considerations in the application of biological denitrification.
Table 11. Summary of design considerations for biological denitrification for nitrate removal in potable water.
Pretreatment
Post-Treatment
Chemical Usage
O&M
System
Components
Waste
Management and
Disposal
Limitations



Substrate and nutrient dosing
pH adjustment
Carbon adsorption for organic carbon removal
o Carbon adsorption is not always required
o Residual substrate removal can be accomplished via biological filtration
 Aeration
 Filtration
 Disinfection
 Possible pH adjustment
 Substrate and nutrient addition
 Coagulant/polymer use to meet turbidity standards
 Disinfection
 Historically operator intensive
o Operator demands can be minimized with latest design configurations
 Constant monitoring required to assure efficient removal, microbe health, etc.
 Monitoring of nitrite and ammonia will also be necessary due to the potential for
incomplete denitrification
 Management of chemicals
 Waste sludge storage and disposal
 New plants can be highly automated
 Historically viewed as operationally complex
o More unit processes than IX
o New design configurations can minimize complexity (e.g., fixed bed)
Important process considerations include (Dördelmann 2009):
 Dosage requirements of substrate and nutrients
 Reactor configuration and governing equation of the biological process
 Aeration to remove nitrogen gas and provide oxygen
 Filtration to remove particulate matter
 Activated carbon may be used to remove substrate residual and avoid DBP
formation (for heterotrophic systems)
 Disinfection


Sludge disposal – Biological solids and residual organic matter
No waste brine or concentrate as in separation processes






Requires anoxic conditions
Chemical management
Few examples for nitrate removal in the U.S.
Post-treatment requirements
Operator training
Intermittent use of wells may be challenging due to the need for acclimation of
microorganisms
Technical Report 6: Drinking Water Treatment for Nitrate
90
Water Quality
Anoxic conditions are required for denitrification to occur. In the presence of oxygen (> 0.1 mg/L)
bacteria preferentially reduce oxygen rather than nitrate, diminishing the efficiency of the process. For
all configurations, the optimal growth of microbes must be considered. Control and monitoring of water
quality characteristics including temperature, pH, salinity, and oxidation reduction potential (ORP) can
be fundamental to the stability and efficiency of the biological denitrification system (WA DOH 2005).
For biological denitrification, near neutral pH is preferred (7 – 8) and temperatures below 5oC/41oF can
inhibit denitrification (WA DOH 2005).
Pretreatment will include addition of substrate and nutrients in the appropriate dose while posttreatment requirements can include coagulant addition, filtration, gas exchange, and disinfection for the
removal of biomass, particulates, and substrate residuals (Panglisch et al. 2005; Dördelmann et al.
2006).
System Components and Site Considerations
Important process considerations in the design and operation of BD systems include (Dördelmann
2009):

Dosage requirements of substrate and nutrients

Reactor configuration and governing equation of the biological process

Aeration to remove nitrogen gas and provide oxygen

Filtration to remove particulate matter

Activated carbon to remove substrate residual and avoid DBP formation (for heterotrophic)

Disinfection
Conditions should be optimized to ensure complete denitrification. In addition to nitrate reduction to
meet the nitrate MCL (45 mg/L as NO3-, 10 mg/L as N), effluent nitrite levels must not exceed the nitrite
MCL of 1 mg/L as N. Incomplete denitrification, which can be associated with higher dissolved oxygen
(DO) levels, can result in the production of greenhouse gases (GHG) such as NO and N2O. Dissolved
oxygen levels can be decreased using reducing agents or through the provision of sufficient electron
donor to enable depletion of DO (Meyer et al. 2010).
System configurations of biological denitrification include: fluidized bed reactor, fixed bed reactor,
membrane biofilm reactor, and bio-electrochemical reactors. In situ options (including bank filtration)
have also been explored in the research.
Fixed Bed
Fixed bed biological reactors can be in up-flow or down-flow systems in a pressurized or open flow
configuration (Brown 2008). Typical options for growth support media include sand, plastic, and
Technical Report 6: Drinking Water Treatment for Nitrate
91
granular activated carbon (Brown 2008). Accumulation of biomass in the media leads to head loss
requiring periodic backwashing. Post-treatment requirements can include filtration, gas exchange, and
disinfection for the removal of biomass, particulates, and substrate residuals (Panglisch et al. 2005;
Dördelmann et al. 2006). The fixed bed configuration “is often coupled with pre-ozonation to improve
the removal of organic material, which reduces regrowth potential and DBP formation in distribution
systems” (Brown 2008, p. 137). (See Soares (2002), Panglisch et al. (2005), Aslan (2005), Dördelmann et
al. (2006), Carollo Engineers (2008), Upadhyaya (2010), Meyer et al. (2010), and City of Thornton (2010),
in Table A.4 for research examples of the fixed bed configuration.)
A detailed case study of the Fixed Bed configuration of biological denitrification in Riverside, CA, is
included in Section 3.4.5 Biological Denitrification - Case Studies.
Fluidized Bed
The fluidized bed reactor operates in an up-flow mode, resulting in granular growth support media
expansion. Fluidizing the granular media offers several advantages over the fixed bed configuration.
Flow resistance is minimized and the system does not need to be taken off line for backwashing because
accumulated biomass is removed by the fast flowing feed water and/or “in-line mechanical shearing
devices” (Brown 2008, p. 139). “The biofilm is detached from the support material only upon strong
mechanical effect, thus the excess biomass can be intermittently removed from the reactor,
independently of the purified water” (Holló & Czakó 1987, p. 418).
Maintenance of the sufficient up-flow velocity can be achieved through recycled flow and reactor
volumes are designed for a typical bed expansion of 25 to 30% (Brown 2008). (See Kurt et al. (1987),
Holló & Czakó (1987), and Webster & Togna (2009), in Table A.4 for research examples of the fluidized
bed configuration.)
A detailed case study of the Fluidized Bed configuration of biological denitrification in Rialto, CA is
included in Section 3.4.5 Biological Denitrification - Case Studies.
Membrane Biological Reactor (MBR)/Membrane Biofilm Reactor (MBfR)
With the addition of membrane technology to conventional biological denitrification, common concerns
of biological treatment can be minimized through physical separation of biomass and substrate from the
treated water. In a comprehensive review of membrane bioreactors, McAdam & Judd (2006) present
the pros and cons of a variety of MBR configurations (Table 12). MBRs can be designed for autotrophic
or heterotrophic denitrification. Pressurized systems have been explored using submerged
ultrafiltration membranes or external (sidestream) MBRs, while pressure neutral diffusion systems have
been implemented with ion exchange membranes and microporous membranes (McAdam & Judd 2006;
Brown 2008). Membrane types include hollow fiber, ion exchange, microporous, and flat sheet. (See
Mansell & Schroeder (2002), Ergas & Rheinheimer (2004), Nerenberg & Rittman (2004), Chung et al.
(2007), Meyer et al. (2010), and City of Thornton (2010) in Table A.4 for research examples of MBR
configurations.)
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92
Applied Process Technology, Inc. (APT) has developed an autotrophic membrane biofilm reactor (MBfR)
(Gormly & Borg N.D.) using hydrogen gas as the electron donor rather than a carbon substrate. Early
pilot and bench-scale studies of the APT MBfR raised several key challenges requiring optimization of
the system, including the need to avoid build-up of excess biomass (Rittmann 2007). As part of a long
term pilot-scale study19 in Glendale, AZ, APT’s MBfR was examined to address high nitrate levels in
groundwater. This autotrophic biological denitrification system successfully reduced nitrate levels to
below the MCL. Three types of hollow fiber membranes were examined for substrate delivery.
Operational concerns highlighted by this study include (Meyer et al. 2010):

Problems with leaking fibers,

hydrogen sulfide formation due to excessive hydrogen gas pressure,

ammonium generation from biomass decay due to operational interruption and insufficient
electron donor, and

nitrite levels above the 1 mg/L nitrite as N limit (incomplete denitrification).
To address these concerns, the authors suggest:

The use of the latest optimized membranes,

consistent and adequate nutrient and electron donor supply,

oxidation of nitrite in post-treatment if necessary,

stable loading and continuous operation to avoid system upset, and

parallel reactors to allow for maintenance and repair.
The MBfR pilot was one of three biological configurations examined in Glendale. Two up-flow
heterotrophic fixed bed bioreactors were also examined, each with a different media type. Posttreatment included filtration using biologically active carbon and ozonation. The two most promising
biological treatment options, the MBfR and the up-flow fixed bed bioreactor with plastic media, were
compared with each other and also with an IX system. Overall, using a multi-criteria analysis with
consideration of sustainability, the MBfR scored the most favorably regarding benefits, but the least
favorably regarding life cycle costs. The life cycle costs of both the IX and the fixed bed bioreactor
options were lower than that of the MBfR. The Glendale study highlights several key areas of future
research including “a shut-down test where biological treatment processes sit dry for a period of time
and then re-start at optimal hydraulic loading rates [and] a re-acclimation test where systems are reinitiated after losing all viable biomass” (Meyer et al. 2010, p. 164).
As a promising technology, with further research and design optimization to reduce costs, the MBfR may
become a more feasible treatment option. As of 2008, a demonstration project of the MBfR for nitrate
and dibromochloropropane (DBCP) removal was under consideration for the City of Fresno, CA, to test
performance of the MBfR as an alternative treatment option (City of Fresno 2008).
19
Project partners and participants: City of Glendale, Arizona, Water Research Foundation, Arizona State University, CH2M
HILL, Applied Process Technology, Inc., Intuitech, Inc., KIWA Water Research, and Layne-Christensen.
Technical Report 6: Drinking Water Treatment for Nitrate
93
Table 12. Membrane biological reactor configurations.
Diffusive Extraction
Microporous Membranes
Diffusive Extraction
Ion Exchange Membranes
Gaseous Substrate Delivery
Hollow Fiber Membranes
Pressure Driven
Direct Filtration MBRs
Relying on diffusion for nitrate transfer through the membrane, extractive
MBRs (i.e., Fixed MBRs) do not directly filter the treatment stream, but they do
provide separation of the denitrification chamber (substrate, biomass, and
associated residuals) and the treatment stream. Key issues are the transfer of
biomass or substrate across membrane, the potential for fouling/scaling, and
the need for a high transfer rate of nitrate to the denitrification compartment.
With the use of an ion exchange membrane rather than a microporous
membrane, selectivity for nitrate and decreased mass transfer from the
denitrification compartment are facilitated; however, capital and maintenance
costs of ion exchange membranes can be significant and the need to manage
membrane fouling persists (McAdam & Judd 2006).
In autotrophic systems, membranes can be used for gaseous substrate
delivery, (i.e., hydrogen gas) (McAdam & Judd 2006). Previous problems with
limited hydrogen gas transfer have been addressed with the use of hollow
fiber membranes for delivery. Substrate passes through the membrane to the
biofilm on the outer membrane surface. The membrane does not separate the
biomass from the treatment stream and does not directly filter the treatment
stream (McAdam & Judd 2006); the presence of “sloughed biomass” and
biological residuals in the treatment stream requires further treatment
downstream.
Pressurized MBRs provide the advantage of direct filtration. Pressure is used
to draw the denitrified water through the submerged membrane, leaving
behind biomass and other undesirable constituents. However, the use of this
configuration for denitrification is complicated by the fact that aeration is
typically used for mixing and to minimize fouling of the external membrane
surface (Brown 2008).
In Situ Denitrification
Bank filtration refers to the withdrawal of surface water through an embankment. The porous media
(soil) of the bank serves as a biological reactor providing treatment through “filtration, dilution,
sorption, and biodegradation processes” (Brown 2008, p. 140). Bank filtration was employed in water
treatment as early as 1870 along the Rhine River in Germany (Brown 2008). As a recent example, a fullscale study in Aurora, CO, demonstrated effective nitrate removal with bank filtration of surface water
from the South Platte River (Waskom, Carlson & Brauer N.D.). Bank filtration has also been
implemented to address nitrate impacted waters in Saxony, Germany, and Des Moines, IA (Jones et al.
2007; Grischek et al. 2010).
Biological denitrification for in situ removal of nitrate from groundwater was explored by Hunter (2001),
Haugen et al. (2002), Schnobrich et al. (2007), and many others. Through in situ denitrification, the
subsurface acts as the porous media through which water is filtered. Residual organics and biomass
from denitrifiers can thus be removed naturally. (See Hunter (2001), Haugen et al. (2002), and
Schnobrich et al. (2007) in Table A.4 for research examples of in situ application.) See Technical Report
5, Section 2 for a discussion of in situ denitrification, permeable reactive barriers, phytoremediation, and
other remediation methods (King et al. 2012).
Technical Report 6: Drinking Water Treatment for Nitrate
94
Post-Treatment Requirements - Filtration/Taste & Odor/Disinfection
With the use of microorganisms and the addition of a carbon substrate, post-treatment is essential to
meet turbidity standards, to remove biomass and residual organic matter, and to address taste and odor
concerns. Post-treatment must include disinfection to address biological contamination and can also
include dual media filtration and/or activated carbon filtration and aeration (individual state regulations
will need to address local requirements).
Residuals Management and Disposal
In contrast to the concentrated waste stream from removal processes, biological denitrification has
limited waste demands due to the conversion of nitrate to nitrogen gas. Waste sludge, consisting of
biological solids and residual organic matter, requires appropriate disposal; however, with nearly 100%
water recovery, the low waste volumes are not a significant burden (Kapoor & Viraraghavan 1997).
Maintenance, Monitoring, and Operational Complexity
Because biological denitrification is microbially mediated, to maximize performance, systems should be
run continuously, with a consistent supply of substrate and nutrients at the appropriate dosage
(Dördelmann 2009). An initial startup period may be necessary for development and acclimation of the
microorganisms (Holló & Czakó 1987; Aslan 2005). This may be problematic for intermittent use of wells
and wasting may be required for acclimation to occur. Backwashing, consistent maintenance, and
regular monitoring of product water quality are also essential. Constituents that should be monitored
frequently are nitrate, nitrite, pH, oxygen, turbidity, conductivity, dissolved organic carbon, and bacterial
count (Dördelmann 2009). Operation and maintenance demands of biological denitrification systems
typically exceed those of alternative treatment technologies. However, these systems are more
sustainable because nitrate is reduced to innocuous nitrogen gas rather than concentrated in a waste
stream that requires costly disposal (Dördelmann 2009).
3.4.2 Biological Denitrification - Cost Considerations
For efficient operation of a biological denitrification system, maintaining optimal conditions for the
bacteria is essential, as is balancing the appropriate substrate and nutrient dose and managing pre and
post-treatment while meeting necessary potable water guidelines. Factors affecting system cost include
facility size (flow rate), source water quality (including nitrate concentration), environmental factors
(temperature and pH), target effluent nitrate concentration, and possible wasting due to intermittent
use of wells and associated acclimation of microorganisms.
Capital costs for biological denitrification include land, housing, piping, storage tanks, O&M equipment,
preliminary testing (through extensive pilot studies), permits, and significant operator training. O&M
costs include post-treatment, sludge disposal, chemical use (pH adjustment, substrate and nutrient
dosing), repair, extensive monitoring and maintenance, power, and labor. Costs can be higher in certain
states, depending on post-treatment requirements.
Technical Report 6: Drinking Water Treatment for Nitrate
95
Very little published cost information from existing biological denitrification systems for drinking water
is available in the literature, due to the limited number of full-scale systems (Table 13). Costs have been
adjusted to 2010 dollars, unless indicated otherwise. The listed cost information is provided as an
approximate range of costs for specific facilities. Costs for implementing biological denitrification may
be very different from those listed here. A thorough cost analysis of design parameters for specific
locations would be required for accurate cost estimation. The information gathered through the
questionnaire includes detailed costs associated with the individual case studies included in this analysis.
A detailed discussion of treatment costs is included in Section 6 Treatment Cost Analysis.
Table 13. Cost information* for biological denitrification of potable water.
System Flow**
< 0.5 MGD
0.5 – 5 MGD
5+ MGD
***
0.51 – 0.62 [4]
0.33 – 0.46 [2, 3]
***
0.74 – 0.94 [4]
1.03 – 1.13 [2, 3]
***
1.25 – 1.56 [4]
Annualized Capital Cost ($/1000 gal)
0.83 [1]
0.61 – 0.80 [2, 3]
O&M Cost ($/1000 gal)
0.30 [1]
Total Annualized Cost ($/1000 gal)
1.13 [1]
*
Costs have been adjusted to 2010 dollars with 7% interest over 20 years, unless indicated otherwise.
When available, costs are based on actual system flow rather than design capacity.
***
Listed costs are based on biological treatment for perchlorate and should be considered only as a rough
estimate of similar systems for nitrate treatment.
[1] Silverstein (2010), not adjusted to 2010 dollars. [2] Webster & Togna (2009). [3] Carollo Engineers (2008).
[4] Meyer et al. (2010).
**
3.4.3 Biological Denitrification - Selected Research
Table A.4 of the Appendix lists recent research studies relevant to the use of biological denitrification in
potable water treatment.
3.4.4 Biological Denitrification - Summary of Advantages and Disadvantages
A summary of advantages and disadvantages of biological denitrification in comparison with other
treatment options is listed in Table A.6 of the Appendix. Advantages of the use of biological
denitrification for nitrate removal from potable water include high water recovery, no brine or
concentrate waste stream (reduction of nitrate rather than removal to a concentrated waste stream),
low sludge waste, less expensive operation, limited chemical input, multiple contaminant removal, and
increased sustainability (WA DOH 2005; Brown 2008; Upadhyaya 2010).
Disadvantages of nitrate removal using biological denitrification are post-treatment requirements for
the removal of biomass and dissolved organics, high capital costs, potential sensitivity to environmental
conditions (although recent pilot tests indicate robust newer designs), system footprint larger than
typical IX systems, high system complexity (may be simplified with new configurations), lack of full-scale
systems in the U.S., potential for incomplete denitrification and GHG production, pilot study
requirements, and slow start-up (Kapoor & Viraraghavan 1997; WA DOH 2005).
Technical Report 6: Drinking Water Treatment for Nitrate
96
3.4.5 Biological Denitrification - Case Studies
The following case studies provide detailed information on the design and operation of a pilot-scale and
planned full-scale biological treatment systems that can be used for nitrate removal.
System Name: West Valley Water District
System Location: Rialto, CA
PWSID: CA 3610004
CASE #13
System Type: Demonstration System, Full-scale Installation is under construction
Treatment Type: Biological Denitrification, Fluidized Bed Bioreactor (FBR)
Questionnaire completed by: Todd Webster from Envirogen Technologies, Inc., Director of Sales &
Bioreactor Applications.
Tom Crowley from the West Valley Water District.
Demonstration Dates of Operation: 2007 – 2008, Full-scale Installation Proposed Startup Date: 2012
System Description
Treatment Type
Fluidized Bed Bioreactor
The West Valley Water District
2,000 – 4,000 gpm
System Capacity
(District) utilizes 2 surface water
(for
proposed
full-scale treatment)
sources and 5 groundwater wells.
Raw Water Nitrate
Of these supplies, one
(abandoned well)
17 – 19 mg/L as nitrate
groundwater well is impacted by
nitrate contamination above the
~4 – 5 mg/L as N
MCL, with an average nitrate
(pilot)
27.5 – 27.9 mg/L as nitrate
concentration of 18 mg/L of
6.2 – 6.3 mg/L as N
nitrate as nitrate (~4 mg/L of
Raw Water Perchlorate
nitrate as N). The well source is
(pilot)
50+ ug/L
the Chino Basin which has an
estimated capacity of 300 – 400K
ac. ft. For the immediate future this well has been abandoned due to nitrate contamination, while feasible
treatment options are being explored. The primary water quality concern in the District is perchlorate
contamination. Biological denitrification has been explored principally to address perchlorate levels typically in the
range of 50 – 53 μg/L. However, simultaneous nitrate reduction in the biological denitrification process makes this
system an appropriate example as a nitrate treatment alternative.
Unlike the removal processes of IX, RO, and EDR, biological denitrification allows for the destruction of nitrate
through reduction to innocuous nitrogen gas. The fluidized bed configuration maximizes media surface area for
the growth of denitrifying bacteria. After a successful 1-year demonstration study on well Rialto #2, a full-scale
Fluidized Bed Bioreactor (FBR) is expected to be online in early 2012.
Technical Report 6: Drinking Water Treatment for Nitrate
97
Figure 13. FBR configuration. (Source: reprinted with permission, Webster & Togna 2009.)
“The system is the fluidized bed bioreactor (FBR). The contaminated feed water is pumped from the wellhead and
fed directly into a recycle line of the reactor. The feed and recycle water enters the vessel through an inlet header
at the bottom of the reactor and is distributed through lateral piping and nozzles (Figure 13). The fluid passes
upward through the media, causing the media to hydraulically expand approximately 28% of the settled bed
height. Through a self-inoculating process from the contaminated feed water, microorganisms attach on to the
fluidized media. Adequate quantities of electron donor (i.e., acetic acid) and nutrients are added to the reactor.
Utilizing this electron donor and the nutrients, the attached microorganisms perform an oxidation/reduction
reaction in consuming all of the dissolved oxygen, nitrate, and perchlorate. As the microorganisms grow, the
amount of attached microbes per media particle also increases. Since the microbes primarily consist of water, the
volume of the microbe/media particle increases, but the specific density decreases. This allows the media bed to
expand and fluidize further such that longer hydraulic retention times can be achieved for contaminant removal.
The treated fluid flows into a submerged recycle collection header pipe and the effluent collection header pipe at
the top of the reactor. A portion of the fluid exits the FBR system to a post-aerator while the balance is recycled
back to the suction of the influent pump. An in-bed biomass separation device controls bed height growth by
physically separating biomass from the media particles. Typically, a bed expansion of 40 – 60% of the settled bed
height is targeted. Any excess biomass that is separated from the media exits the system through the effluent
collection system” (Webster & Togna 2009, p. 6).
Source Water Quality
 Nitrate – mg/L as nitrate (mg/L as N)
o Demonstration well: 27.5 – 27.9 (6.2 – 6.3)
o Abandoned nitrate impacted well
 Average: 18 (~4)
 Co-contaminants: Perchlorate
o Demonstration well: 50 – 53 μg/L, spiked to
1000 μg/L (with appropriate substrate and
nutrient adjustments)
o Abandoned nitrate impacted well: a few ppb
Treatment Technology Selection
The fluidized bed bioreactor was selected for perchlorate removal; however, nitrate reduction is also
accomplished. Due to the levels of nitrate and perchlorate, biological denitrification was deemed to be more costeffective than alternative physico-chemical technologies. Generally, with nitrate levels well above the MCL (e.g.,
100 mg/L as nitrate), removal processes can become more costly. Biological denitrification can be the more
feasible option for source water containing co-contaminants and/or high levels of nitrate.
For the Rialto #6 and West Valley Water District #11 wells, the fluidized bed reactor and IX were considered. Two
additional pilot studies were performed to assess nitrate and perchlorate treatment using a packed bed bioreactor
and zero valent iron.
Technical Report 6: Drinking Water Treatment for Nitrate
98
Demonstration System Parameters



Design Capacity
o 50 gpm capacity
Pretreatment
o Substrate and nutrient addition
 Acetic Acid:
16.2 mg/L as C (+20 – 25%)
15 mL/min, 50% acetic acid
o Nutrient addition
 Phosphoric Acid:
0.3 mg/L as P
10.5 mL/min
Post-treatment
o Aeration tank
 Increase dissolved oxygen
o Clarifier/multimedia filter
o GAC filtration
o UV disinfection versus chlorination






Water Recovery: > 99%
Bed Expansion
o 28% of settled bed height
o Max: 40 – 60%
Media: Sand or GAC
Cleaning requirements
o Biomass separator
o In-bed cleaning eductor
Manufacturer:
Envirogen Technologies, Inc.
Monitoring: Throughout the demonstration
using online nitrate and perchlorate
analyzers
Demonstration System Cost Estimation - Scaling up from 50 gpm to 1000 gpm
Capital Costs (2008 dollars) (1000 gpm)
Total Equipment Costs:
$1,966,000
Total Contractor Costs:
$570,140
Total Home Office Costs:
$664,000
Total Installed Capital Costs (1000 gpm):
$3,200,140
Amortized Capital Cost ($/AF):
$128 (30 years, 4.9% bonding rate)
O & M Costs (2008 dollars) (1000 gpm)
Electricity ($/yr):
$87,600
Chemicals ($/yr):
$133,187
Maintenance ($/yr):
$20,000
Total Operating Costs ($/yr):
$240,787
Operating Costs ($/AF):
$149
Total Cost (2008 dollars) (1000 gpm)
Total Annualized Cost ($/AF):
$277
Technical Report 6: Drinking Water Treatment for Nitrate
99
Proposed Full-scale System Parameters - See Figure 14




Design Capacity
o 2000 gpm capacity
o Expandable to 4000 gpm
Pretreatment
o Substrate and nutrient addition
 Acetic Acid: 10 – 15 mg/L as C
Post-treatment
o Aeration tank
 Increase dissolved oxygen
o Clarifier/multimedia filter
o Chlorine disinfection
Treatment system footprint
o Treatment system: 2 FBRs
 14’ diameter x 24’ height
o Residuals handling system
 DAF for solids removal
o Total system footprint
 For 4000 gpm
 180’ x 130’
 For 2000 gpm
 25% less than above







Water Recovery: > 99% expected
Bed Expansion
o 28% of settled bed height
o Max: 40 – 60%
Media: Sand or GAC
Cleaning requirements
o Biomass separator
o In-bed cleaning eductor
Manufacturer:
Envirogen Technologies, Inc.
Monitoring: N/A
Waste Volume:
0.3 gpm waste per 2000 gpm treated
Figure 14. FBR treatment system schematic. (Source: Webster et al. 2009, reprinted from Journal AWWA (May
2009) by permission. Copyright © 2009 by the American Water Works Association.)
Technical Report 6: Drinking Water Treatment for Nitrate
100
Proposed Full-scale System Cost Estimation
Capital Costs (Total with explanation or component costs)
Treatment and Monitoring
Equipment:
$1.8 million for the 2 FBR vessels, the 2 post-aeration vessels, nitrate
and perchlorate monitoring, 1 DAF, chemical feed systems, pumps,
valves, additional components
Filtration System:
$800,000 for the 2 clarifier and multimedia filters
O & M Costs (Total with explanation or component costs)
Unavailable because system is not yet operating.
Please see above for estimated O & M costs from the full-scale demonstration study.
Residuals Management
Unlike removal technologies, the use of the FBR results in destruction of nitrate and perchlorate, rather than the
transfer of these constituents to a concentrated waste stream requiring disposal.
Technology Benefits and Drawbacks
Benefits
 Capable of perchlorate removal and
handling high nitrate levels
 Reduction of nitrate rather than just
removal
 High water recovery and limited waste
 Lower operating costs than removal
technologies
Drawbacks
 Limited application in the U.S.
 Large system footprint
 More complicated permitting
 Extensive pilot study necessary
 Start-up time (up to a month)
 Increased operator attention
 Sensitivity to system interruption
Additional Information
The full-scale system is being planned specifically to address perchlorate contamination, but will reduce nitrate as
well. Construction is currently underway and the system should be fully operational with discharge to
groundwater by Mid-2012. With approval from the California Department of Public Health (CDPH) it is expected
that distribution of treated drinking water will begin in Early-2013. Regarding operator training, for this system,
the operators already held the required certification due to operation of a surface water treatment plant;
however, for other utilities lacking this pre-existing experience, additional training would likely be needed.
Regarding permitting, the 97-005 process from the CDPH Policy Memo 97-005, (“Guidance for the Direct Domestic
Use of Extremely Impaired Sources”) was followed as guidance for the FBR installation. The 97-005 process is
strenuous and involved, requiring analysis of failure and worst-case scenarios and a 6 month demonstration of
proper operation of the treatment plant. The system sizes for which an FBR would be appropriate vary with the
concentration of contaminants. Feasible application of an FBR can be more dependent on load than on flow
capacity. The FBR has been implemented or tested for systems as small as 7 to 12 gpm and across perchlorate
concentrations from 12 to 13000 ppb. Typical flow rates are 250 to 5000 gpm, but with high loads FBRs can
become more feasible for lower flow rates.
Technical Report 6: Drinking Water Treatment for Nitrate
101
Source*
Webster, T.S., Guarini. W.J. and Wong, H.S. (2009) Fluidized bed bioreactor treatment of perchlorate-laden
groundwater to potable standards. Journal of the American Water Works Association, 101 (5).
Webster, T.S. and Togna, P. (2009) Final Report: Demonstration of a Full-Scale Fluidized Bed Bioreactor for the
Treatment of Perchlorate at Low Concentrations in Groundwater. ESTCP Project ER-0543.
Webster, T.S. and Crowley, T. (2010) Completed questionnaire and personal communication.
*Unpublished sources used in the development of the case studies are not reflected in the References section of this
report.
Technical Report 6: Drinking Water Treatment for Nitrate
102
System Name: Western Municipal Water District (WMWD) - Arlington Desalter
System Location: Riverside, CA
PWSID: CA3310049
CASE #14
System Type: Pilot Study, Full-scale System is currently in the Design Phase
Treatment Type: Fixed Bed Bioreactor (FXB)
Questionnaire completed by: Joseph Bernosky, WMWD, Director of Engineering
Jess Brown, Carollo Engineers, Carollo Research Group Manager
Startup Date: Proposed 2013
System Description
Treatment Type
System Capacity
Raw Water Nitrate
Fixed Bed Bioreactor
2.4 MGD (1670 gpm)
44 – 89 mg/L as nitrate
10 – 20 mg/L as N
The Western Municipal Water District
(Western) operates the Arlington Desalter as
a drinking water supply facility. The original
RO water treatment facility was constructed
in the late-1980s for salt management in the Arlington groundwater basin. In 2002 the facility was upgraded and
subsequently approved as a potable water supply by the California Department of Public Health (CDPH). Three
wells supply raw water to the RO process and two additional wells supply bypass water for blending with the RO
permeate to produce the finished water (product water).
The current capacity of the Arlington Desalter is 5 million gallons per day (MGD) of RO permeate and
approximately 1.3 MGD of untreated bypass for a total product water capacity of 6.3 MGD. Western’s water
supply reliability program, developed through the Integrated Regional Water Management Plan (IRWMP), includes
plans for expansion of the Arlington Desalter to 10 MGD capacity.
A pilot study was conducted at the Arlington Desalter from April through November 2007 that demonstrated the
feasibility of nitrate removal using fixed bed biological treatment (biodenitrification) of the RO bypass stream.
After completion of the initial pilot study, CDPH proposed a turbidity standard for the biodenitrification process.
Supplemental pilot testing conducted between May and September 2008 demonstrated compliance with the new
turbidity standard by adding a nitrogen degasification step followed by coagulation and polishing filters.
The FXB biological process utilizes a stationary bed of granular activated carbon (GAC) on which biofilms containing
nitrate-reducing bacteria develop. Raw water is drawn from a well amended with an electron donor such as acetic
acid. The water is then pumped through the GAC bed. Bacteria in the bed convert the nitrate to nitrogen gas and
water. A one-time acclimation period is required to develop the nitrate-reducing biological activity, which is done
by contacting virgin GAC with raw water and acetic acid for two to three weeks. The denitrifying bacteria used in
the system are indigenous to the natural groundwater, meaning the system is naturally seeded with bacteria
present in the groundwater.
During the pilot, a clone library analysis was performed on the bacteria within the biofilter to classify the various
types of denitrifying bacteria present. The analysis revealed a diverse community of bacteria. At least 10 different
denitrifying genera were identified, including Acidovorax, which comprised approximately 37 percent of the total
bacteria in the FXB biofilters. The bacteria identified were gram negative, suggesting that they would be
particularly sensitive to chemical disinfection, as gram-negative bacteria tend to have thin cell walls.
Technical Report 6: Drinking Water Treatment for Nitrate
103
Source Water Quality

Nitrate – mg/L as nitrate (mg/L N)
o Average – 75 (17)
o Minimum – 44 (10)
o Maximum – 89 (20)

Co-contaminants
o Perchlorate: 6 g/L
o DBCP: 0.025 µg/L
Treatment Technology Selection
The FXB process has been used successfully for removal of nitrate from drinking water supplies in Europe for
decades, but has not yet been used full-scale in the United States. Reasons for using the FXB process at the
Arlington Desalter include the following:
•
Nitrate is not concentrated in a waste stream, as in RO or IX treatment, but is converted to nitrogen gas,
which is released to the atmosphere—a harmless emission because the atmosphere is 78 percent
nitrogen.
•
Nitrate removal efficiencies are high. Typically, greater than 90 percent removal was achieved during the
Arlington pilot studies and removal to non-detect levels was possible.
•
The biodenitrification process results in simultaneous destruction of some anthropogenic contaminants.
For example, perchlorate, found in the Arlington Desalter supply, was reduced to non-detect levels in the
pilot study.
Historically, IX treatment has been the process of choice for nitrate removal in this country; however, it results in
the replacement of nitrate with chloride in the drinking water supply. It is estimated that the equivalent IX system
installed at the Arlington Desalter would add approximately 3 million pounds of salt to the basin annually. The
removal of salt was the purpose for construction of the Arlington Desalter in the first place.
Treatment System Parameters



Design Capacity
o 1,670 gpm capacity
Pretreatment
o Substrate and nutrient addition
Post-treatment
o Degasification of N2
o Filtration for compliance with SWTR



Water Recovery: expected 95%
Media: GAC
Treatment system footprint: TBD
Residuals Management
The residuals from this process, primarily biological growth, are accumulated in the filtration process. Once a
predetermined pressure loss is experienced in filtration, the filters are backwashed to remove the accumulated
solids. The solid laden backwash is then sent to the Santa Ana Regional Interceptor (SARI) line and ultimately
disposed of off shore.
Technology Benefits and Drawbacks
Benefits




Less expensive than other technologies
No disposal of waste brine
High water recovery rate: > 95%
Can remove co-contaminants
Technical Report 6: Drinking Water Treatment for Nitrate
Drawbacks
 No full-scale applications in operation
 More complicated permitting
104
Treatment Technology Costs
Detailed cost estimates are being developed. Detailed design of this system may occur in 2012, and full-scale
construction of this system may be in 2013.
As an approximation, the below costs are based on a fixed-bed demonstration system for the removal of
perchlorate with a similar empty bed contact time (EBCT) (Carollo Engineers 2008).
Capital Costs (2008 dollars)
Flow Rate:
Total:
Direct Installed Costs:
1000 gpm
2000 gpm
$4,193,000
$7,395,000
$2,373,000
$4,200,000
O & M Costs (2008 dollars)
Total Estimated Annual O&M Costs:
$175,000
$348,000
Chemicals ($/yr):
$161,000
$323,000
Other (GAC and Filter Sand) ($/yr):
$9,000
$17,000
Power ($/yr):
$5,000
$8,000
Total Costs (2008 dollars, 2.8% discount rate, 30-year lifecycle)
Amortized Project Costs:
$209,000
$368,000
Estimated Annual Budget:
$384,000
$716,000
Total Treatment Costs ($/1000 gal):
$0.73
$0.68
Total Treatment Costs ($/AF):
$238
$222
Source*
Bernosky, J. (2010) Personal communication.
Brown, J. (2010) Personal communication.
Carollo Engineers. Final Report: Fixed-Bed Biological Nitrate Removal Pilot Testing at the Arlington Desalter Facility.
Carollo Engineers. (2008) Final Report: Direct Fixed-Bed Biological Perchlorate Destruction Demonstration. ESTCP
Project ER-0544.
*Unpublished sources used in the development of the case studies are not reflected in the References section of this
report.
Technical Report 6: Drinking Water Treatment for Nitrate
105
3.5 Chemical Denitrification (CD)
Chemical denitrification can be accomplished with reduction of nitrate by metals. Various metals have
been investigated for use in nitrate reduction including aluminum and iron (both Feo and Fe2+), while
copper, palladium, and rhodium can be used as catalysts in nitrate reduction (Shrimali & Singh 2001).
The advantage of chemical denitrification over the removal technologies is that nitrate is converted to
other nitrogen species rather than simply displaced to a concentrated waste stream that requires
disposal. Problems with chemical denitrification of potable water are the reduction of nitrate beyond
nitrogen gas to ammonia, partial denitrification, and insufficient nitrate removal (nitrite can be
converted to nitrate with the use of chlorine in disinfection). No full-scale chemical denitrification
systems have been installed in the United States for the removal of nitrate in potable water treatment.
A significant body of research has explored the use of zero valent iron (ZVI) in denitrification. Several
patented granular media options are also emerging, including SMI-III® (Sulfur Modified Iron),
MicroNose™ Technology, and Cleanit®-LC.
Based on lab and pilot-scale studies, there is much variation in the configuration of chemical
denitrification systems for nitrate removal from potable water. The generic mechanism of
denitrification involves the transfer of electrons from an electron donating metal to nitrate. As in
biological denitrification, nitrate is reduced in accordance with Eqn. 9. However, in contrast with
biological denitrification, using chemical denitrification, the nitrogen in nitrate is often reduced to the
least oxidized form, ammonium (Eqn. 9a) (Huang et al. 1998; Hao et al. 2005).
NO3-  NO2-  NO  N2O  N2
(Eqn. 9)
NO3-  NO2-  NH4+
(Eqn. 9a)
Nitrate is exposed to an electron donating metal by passing the treatment stream through granular
media. Particle size, surface area, and surface chemistry are important media characteristics related to
the efficiency of nitrate removal.
3.5.1 Zero Valent Iron (ZVI)
Due to the extensive research focused on the use of zero valent iron (ZVI), ZVI will serve as a preliminary
example. There is some variation in the use of ZVI. Forms of application include powdered iron,
stabilized iron as nanoparticles, iron filings, and permeable reactive barriers (PRBs). Relevant reactions
are listed in Eqns. 13 to 18 (Huang et al. 1998; Hao et al. 2005; Xiong et al. 2009). Nitrate can be
reduced to nitrite (Eqn. 13), ammonia (Eqn. 14), or nitrogen gas (Eqn. 15) by ZVI. Following nitrate
reduction to nitrite, nitrite can then be reduced to ammonia (Eqn. 16). Nitrate can also be reduced by
the hydrogen gas that is produced from corrosion reactions (Eqn. 17) to ammonia (Eqn. 18).
Feo + NO3- + 2H+  Fe2+ + NO2- + H2O
Technical Report 6: Drinking Water Treatment for Nitrate
(Eqn. 13)
106
4Feo + NO3- + 10H+  NH4+ + 4Fe2+ + 3H2O
(Eqn. 14)
5Feo + 2NO3- + 6H2O  N2(g) + 5Fe2+ + 12OH-
(Eqn. 15)
3Feo + NO2- + 8H+  3Fe2+ + NH4+ + 2H2O
(Eqn. 16)
Feo + 2H+  H2(g) + Fe2+
(Eqn. 17)
NO3- + 4H2 + 2H+  NH4+ + 3H2O
(Eqn. 18)
The reduction of nitrate by iron is characterized by an increase in pH and consumption of hydrogen ions.
pH is a significant controlling factor for this treatment method (Hao et al. 2005). The kinetics of nitrate
reduction by ZVI have been thoroughly covered in the literature to determine the reaction rate under
various conditions. For example, Alowitz & Scherer (2002) examined the nitrate reduction rates of three
types of iron. Findings indicate that reduction rate increases with decreasing pH. Huang et al. (1998)
investigated the use of powdered ZVI for the reduction of nitrate to ammonia. Highly pH dependent,
nitrate reduction was kinetically favorable only at a pH below 4. The minimum ratio of iron to nitrate
was 120 m2/mol NO3- for complete reduction within 1 hour. Nitrate reduction by ZVI can be optimized
through pretreatment of iron particles. High temperature exposure to hydrogen gas and deposition of
copper were explored separately as options for pretreatment of the iron surface (Liou et al. 2005). Both
methods resulted in improvement of nitrate reduction in almost neutral solutions. The mechanism of
improvement is due to the surface chemistry of iron. With a buildup of a surface oxide layer, the
availability of sites for nitrate reduction decreases. Hydrogen gas pretreatment reduces the oxide layer,
while deposited copper serves as a catalyst for the transfer of electrons. In their investigation of
stabilized ZVI nanoparticles, Xiong et al. (2009) found that the end product of denitrification (nitrogen
gas versus ammonium) could be controlled by the iron to nitrate ratio and the use of catalysts.
Figure 15. Surface chemistry of ZVI particles. (Source: reprinted with permission, Chiu 2009.)
Examination of the surface chemistry of ZVI particles is of the utmost importance to model and
understand its use in the reduction of nitrate. Illustrated in Figure 15, relevant factors include corrosion
of ZVI, complexation with water, surface complexation, reduction, precipitation, and adsorption. In the
corrosion of ZVI, the formation of “green rusts” and “suspended green particles” is associated with
Technical Report 6: Drinking Water Treatment for Nitrate
107
stabilization of pH and steady decrease in nitrate (Choe et al. 2004). For nitrate reduction to occur,
contact with the reducing agent is required. Reduction of nitrate by ZVI or by any surface bound species
requires access to surface sites. Competition for surface sites can impede nitrate reduction; Moore &
Young (2005) examined chloride as a potential competitor. Results indicate a minimal impact on nitrate
removal; however, other competing ions could be important regarding both competition for adsorption
sites and reduction.
3.5.2 Catalytic Denitrification
An extension of chemical denitrification, catalytic denitrification involves metal reduction of nitrate in
the presence of a catalyst. Extensive research has investigated catalytic denitrification which may
become more readily applicable to potable water treatment with further advances (Reddy & Lin 2000;
Pintar et al. 2001; Gavagnin et al. 2002; Lemaignen et al. 2002; Pirkanniemi & Sillanpaa 2002; Chen et al.
2003; Palomares et al. 2003; Pintar 2003; Constantinou et al. 2007; Sun et al. 2010.)
3.5.3 Chemical Denitrification - Design Considerations
Table 14 summarizes key design considerations in the application of chemical denitrification for nitrate
removal from potable water.
Technical Report 6: Drinking Water Treatment for Nitrate
108
Table 14. Summary of design considerations for chemical denitrification.
Pretreatment
Post-Treatment
Chemical Usage









O&M

System
Components/Design
Parameters
Waste Management
and Disposal














Limitations

pH adjustment
Filtration for iron removal
pH adjustment
Chlorine addition for disinfection and oxidation of iron
Gas stripping or breakpoint chlorination (for ammonia)
pH adjustment (acids and bases)
Disinfection and oxidation of iron (chlorine)
Constant monitoring required to ensure efficient nitrate reduction
o Nitrate levels
o Oxidation reduction potential (ORP)
Monitoring of nitrite and ammonia will also be necessary due to the potential
for incomplete denitrification
Management of chemicals
o pH adjustment
o Disinfection
Waste media and backwash water storage and disposal
Ratio of electron donor to nitrate for desired removal
Hydraulic Loading Rate (HLR), Empty Bed Contact Time (EBCT)
Reactor configuration (up-flow, down-flow, in series, in parallel)
Gas stripping or breakpoint chlorination to remove ammonia (if ammonia is
the end-product)
Monitoring equipment
Filtration to remove iron
pH adjustment (decreased in pretreatment and increased before distribution)
Disinfection
Spent media disposal
Iron sludge management
Backwash water
No waste brine or concentrate as in removal processes
No examples of full-scale application for nitrate treatment
o Unknown reliability for full-scale treatment
o Unknown costs and operational complications
Potential for incomplete denitrification
Water Quality
The performance of chemical denitrification systems can be affected by pH, temperature, potential
interference by co-contaminants, and the availability of surface sites. The reduction of nitrate by iron is
characterized by an increase in pH and consumption of hydrogen ions. Thus, pH is a significant
controlling factor for this treatment method (Hao et al. 2005). Alowitz & Scherer (2002) examined the
nitrate reduction rates of three types of iron. Findings indicate that reduction rate increases with
decreasing pH. If nitrate in the water does not come in contact with the electron donor, then reduction
will not be possible. The build-up of precipitates can negatively impact nitrate reduction. The
appropriate iron to nitrate ratio will be based on influent and target nitrate concentrations. Product
water quality will require monitoring for nitrate, nitrite, and ammonia.
Technical Report 6: Drinking Water Treatment for Nitrate
109
System Components and Site Considerations
Major system components include chemical storage (for pH adjustment and disinfection), the column
containing the media, and post-treatment disinfection. With reduction to ammonia, post-treatment
ammonia stripping may also be necessary. Design constraints include optimal temperature, sufficient
EBCT length, avoidance of incomplete denitrification, monitoring requirements (nitrate, nitrite, and
ammonia), appropriate iron to nitrate ratio, and adequate chlorine dosing for disinfection and iron
oxidation (DSWA 2010). Incomplete denitrification, which can be associated with higher dissolved
oxygen (DO) levels, can result in the production of greenhouse gases (GHG) such as NO and N2O.
Dissolved oxygen levels can be decreased using reducing agents or through the provision of sufficient
electron donor to enable depletion of DO (Meyer et al. 2010, regarding biological denitrification).
Residuals Management and Disposal
In contrast to IX and the membrane technologies, the burdens of brine and concentrate disposal are
minimized because nitrate is reduced through chemical denitrification. There is no concentrated brine
solution requiring costly disposal. However, disposal of backwash water, spent media, and iron sludge is
necessary.
Maintenance, Monitoring, and Operational Complexity
With the possibility of incomplete denitrification, monitoring is required to ensure that product water
does not contain high levels of ammonia or nitrite. Exposure of these nitrogen species to chlorine in
disinfection or oxygen downstream can lead to nitrification (oxidation back to nitrate) in the
distribution system, unless controlled. Additional O&M demands include management of chemicals
(e.g., acids, bases, and chlorine), backwashing the column to maintain flow and performance, and waste
management. Despite having no full-scale installation for comparison, overall, chemical denitrification
may potentially be less operationally complex than biological denitrification.
3.5.4 Chemical Denitrification - Emerging Technologies
Sulfur-Modified Iron (SMI) Media
Chemical reduction of nitrate has been demonstrated for potable water treatment using sulfur-modified
iron granular media (DSWA 2010). Certified to the NSF/ANSI Standard 61 for use in drinking water
treatment, SMI-III® is a patented media that is recyclable and offers the advantage of multiple
contaminant removal (SMI-PS 2009). Arsenic and metals can be removed via adsorption (hexavalent
chromium can also be reduced and precipitated), while nitrate is reduced to ammonia (Prima
Environmental N.D.) or nitrogen gas (DSWA 2010). “The SMI-III® manufacturer believes sulfur
modification regulates the environment of reactions to achieve greater and a consistent nitrate
reduction” (DSWA 2010, p. 9). Nitrate reduction is governed by the following reactions (SMI-PS 2009):
4Fe0 + NO3- + 10H+4Fe2+ + NH4+ + 3H2O
Technical Report 6: Drinking Water Treatment for Nitrate
(Eqn. 19)
110
5Fe0 + 2NO3- + 12H+  5Fe2+ + N2 + 6H2O
(Eqn. 20)
Key advantages of SMI-III® are the ability to remove multiple contaminants simultaneously and the
limited waste disposal costs relative to other nitrate removal options (no brine waste stream is
produced) (DSWA 2010). Some previous research indicates inconsistent and insufficient nitrate removal
to meet potable water regulations (DSWA 2010).
Damon S. Williams Associates (DSWA) and the City of Ripon, CA, conducted a pilot study investigating
the use of SMI-III® in potable water treatment. Findings suggest that this treatment option may be
suitable for source nitrate concentrations slightly above the MCL (up to 70 mg/L as nitrate (16 mg/L as
N)). Phase A of the pilot study was operated with the SMI-III® media in an up-flow fluidized bed across a
pH range of 6.0 – 6.8 and with an EBCT of 15 to 30 minutes. Phase B tested improved media
performance across the same pH range and with an EBCT of 30 minutes. Figure 16 displays a process
schematic of the SMI-III® process.
To Waste
Fluff
Chlorine
Coagulant
Static
Mixer
pH Adjust
(Acid)
SMI-III®
Reactor
Pressure
Filter
Chlorine
pH Adjust
(Caustic)
Static
Mixer
Distribution
System
Backwash
Wellhead
Figure 16. Process schematic for denitrification using SMI-III®. (Source: DSWA 2010.)
The media was fluffed (backwashed in up-flow mode) daily to remove oxidized iron and to avoid media
agglomeration. The SMI-III® reactor was followed by coagulation and filtration for the removal of iron,
arsenic, and other constituents. In phase A, the greatest nitrate removal (18 mg/L as nitrate, 4 mg/L as
N) was insufficient to meet the 20% safety margin of the project (a goal of 36 mg/L as nitrate, 8 mg/L as
N), with a starting nitrate concentration of 60 mg/L as nitrate (13.5 mg/L as N). Problems in phase B
resulted in operation interruption; however, a maximum nitrate removal of 24 mg/L as nitrate (5.4 mg/L
as N) was achieved. When the pH was reduced to 6, the system did produce water with nitrate below
the MCL and the project goal nitrate level, on two occasions. Temperature was found to have the most
Technical Report 6: Drinking Water Treatment for Nitrate
111
significant impact on removal efficiency. Nitrate reduction improved with increasing source water
temperatures.
Design constraints include temperature, EBCT, avoidance of incomplete denitrification, determination of
the appropriate iron to nitrate ratio, chlorine requirements for released iron oxidation, clogging from
precipitates, and pH. Nitrate reduction typically increases with decreasing pH, increasing EBCT, and
increasing temperature (DSWA 2010).
SMI - Cost Considerations
Cost analysis in the City of Ripon report included acid, caustic soda, and media and excluded labor and
waste management. In both phases, minimal variation in nitrate reduction was found with operation at
a pH of 6 versus a pH of 6.8. Operation at the higher pH minimizes costs due to prolonging media life
and decreasing chemical input. The production costs for operation at a pH of 6 and 6.8 were estimated
to be $2.24/1000 gal. ($729/AF) and $0.88/1000 gal. ($287/AF), respectively (DSWA 2010). Due to
dissolution of the media over time, media disposal is not expected to be necessary. Dissolved iron is
oxidized and then removed through filtration. In the Ripon pilot study, backwash water was discharged
to the sewer; however, when “…direct sewer disposal is not feasible, the backwash water must undergo
solid/liquid separation with the decant liquids recycled to the head of the treatment system and the
dewatered solids sent to an appropriate landfill for disposal” (DSWA 2010, p. 82). If the waste is
deemed hazardous, disposal can be a major cost consideration.
Granular Clay Media
Certified to the NSF/ANSI Standard 61 for use in drinking water treatment, MicroNose™ Technology
media is currently being examined in Manteca, California, for nitrate removal in potable water
treatment (MicroNose™ 2010). The media consists of “absorbent and permeable pottery granules
which function similar to the mucous membrane in the human nose” (University of Hawaii 2006).
Limited information is available on this emerging technology. The company states, “MicroNose™
Technology media removes heavy metals, such as arsenic, manganese, and lead as well as nitrates
through non-chemical processes” (MicroNose™ 2010). MicroNose™ offers removal of multiple
contaminants concomitantly and claims to be cost-effective, suitable for nitrate removal, and a green
technology. Additional information is needed to assess the design considerations, costs, and
applications of MicroNose™ for nitrate removal from potable water.
Powdered Metal Media
As an emerging technology, Cleanit®-LC (from North American Höganäs) is a metal powder with the
potential to achieve 60 – 90% nitrate removal (Lavis 2010). Certified to the NSF/ANSI Standard 61 for
use in drinking water treatment, this proprietary iron-based powder could be used for removal of cocontaminants in addition to nitrate, including “arsenic, heavy metals, phosphates and pathogens” (Lavis
2010), and potentially hexavalent chromium. Cleanit®-LC media is characterized by the following: a
Technical Report 6: Drinking Water Treatment for Nitrate
112
density of 1800 – 2100 kg/m3, a particle size of 150 – 850 microns, and a porosity of 60%. The powder
can be used to adsorb arsenic in less than 10 minutes, with an arsenic capacity of 4 – 8 mg/g powder.
With an up-flow configuration, the treatment stream is pumped through a column containing the media,
maximizing surface contact. The most significant consideration is the EBCT. At the particle surface,
nitrate is reduced to nitrogen gas with EBCTs of 10 – 30 minutes. Additional key design factors are pH
and temperature. In contrast to membrane technologies, the burdens of disposal are minimized
because nitrate is reduced rather than removed. There is no concentrated brine solution requiring
costly disposal. Preliminary third party results indicate nitrate removal over 7 months to below the MCL
(North American Höganäs, data). However, as a new product on the market, further research is
required to assess Cleanit®-LC for the removal of nitrate and other constituents in potable water
treatment.
3.5.5 Chemical Denitrification - Cost Considerations
For efficient operation of a chemical denitrification system, maintaining efficient nitrate reduction is
essential. Optimal performance includes managing pre and post-treatment to provide appropriate
environmental conditions, while meeting necessary potable water guidelines. Factors affecting system
cost can include facility size (flow rate), source water quality (including nitrate concentration and cocontaminants), environmental factors (temperature and pH), and target effluent nitrate concentration.
Capital costs for chemical denitrification include land, housing, piping, media, storage tanks, O&M
equipment, preliminary testing (through pilot studies), permits, and operator training. O&M costs
include pre and post-treatment, media replenishment and disposal, backwashing, chemical use (e.g., pH
adjustment, chlorine), repair, monitoring, maintenance, power, and labor.
The availability of published cost information for chemical denitrification is strictly limited to pilot-scale
studies, due to the lack of full-scale systems. Cost analysis in the City of Ripon report included acid,
caustic soda, and media and excluded labor and waste management. In both phases, minimal variation
in nitrate reduction was found with operation at a pH of 6 versus a pH of 6.8. Operation at the higher
pH minimizes costs due to prolonging media life and decreasing chemical input. The production costs
for operation at a pH of 6 and 6.8 were estimated to be $2.24/1000 gal. ($729/AF) and $0.88/1000 gal.
($287/AF), respectively (DSWA 2010). Due to dissolution of the media over time, media disposal is not
expected to be necessary. Dissolved iron is oxidized and then removed through filtration. In the Ripon
pilot study backwash water was discharged to the sewer. However, when “…direct sewer disposal is not
feasible, the backwash water must undergo solid/liquid separation with the decant liquids recycled to
the head of the treatment system and the dewatered solids sent to an appropriate landfill for disposal”
(DSWA 2010, p. 82). If the waste is deemed hazardous, disposal can be a major cost consideration. A
detailed discussion of treatment costs is included in Section 6 Treatment Cost Analysis.
Technical Report 6: Drinking Water Treatment for Nitrate
113
3.5.6 Chemical Denitrification - Selected Research
Table A.5 of the Appendix lists recent research studies relevant to the use of chemical denitrification in
potable water treatment.
3.5.7 Chemical Denitrification - Summary of Advantages and Disadvantages
A summary of advantages and disadvantages of chemical denitrification in comparison with other
treatment options is listed in Table A.6 of the Appendix. Advantages of chemical denitrification for
nitrate removal from potable water include the conversion of nitrate to other nitrogen species (no brine
or concentrate waste stream), the potential for more sustainable treatment, and the ability to remove
multiple contaminants.
Problems with chemical denitrification of potable water are the potential reduction of nitrate beyond
nitrogen gas to ammonia, the possibility of partial denitrification, and the associated production of
GHGs, and the lack of full-scale chemical denitrification systems.
3.6 Brine Treatment Alternatives and Hybrid Treatment Systems
Brine or concentrate disposal can be a great concern with the use of the removal processes, IX, RO, and
ED/EDR, especially for inland communities. Brine treatment and recycling alternatives have the
potential to address disposal concerns, improving sustainability and decreasing operating costs. Hybrid
systems, combining different nitrate treatment technologies, have been explored to include the
advantages of multiple treatment options, while avoiding their respective disadvantages (Pintar et al.
2001; Wisniewski et al. 2001; Matos et al. 2006; Kabay et al. 2007; Van Ginkel et al. 2008). Table 15 lists
a selection of additional research related to brine treatment alternatives and the use of hybrid systems
to improve nitrate treatment performance.
The combination of denitrification methods with removal technologies enables resolution of common
problems with each option. The brine waste stream from IX, for example can be treated using biological
denitrification to reduce nitrate to nitrogen gas. Biological denitrification of IX waste brine using an upflow sludge blanket reactor (USBR) was demonstrated at the lab-scale by van der Hoek & Klapwijk
(1987). Clifford & Liu (1993) implemented a lab-scale sequencing batch reactor (SBR) for the
denitrification of waste brine resulting in the ability to recycle the treated waste brine for 15
regeneration cycles. The SBR process was pilot tested in McFarland, CA (Liu & Clifford 1996). With
denitrification of spent brine followed by reuse, a 95% decrease was achieved in salt waste. Use of a
membrane bio-reactor in this context has also been explored (Bae et al. 2002; Chung et al. 2007; Van
Ginkel et al. 2008). Through the reduction or destruction of nitrate in spent IX brine, disposal needs may
be significantly reduced as treated brine can be repeatedly recycled back for use in resin regeneration.
Additionally, through treatment of RO or ED/EDR waste concentrate, removal of nitrate from the waste
stream may improve disposal options.
Technical Report 6: Drinking Water Treatment for Nitrate
114
Table 15. Selected research on brine treatment alternatives and hybrid systems for nitrate treatment of potable
water.
IX and Catalytic Reduction
Pintar et al. (2001)
RO and EDR
EET Corporation (2008)
IX and EDR
ED and MBR
IX and Biological
Denitrification
RO and VSEP
Electrochemical destruction of
nitrate (in IX brine)
Kabay et al. (2007)
Wisniewski et al. (2001)
Van der Hoek & Klapwijk (1987), Clifford & Liu (1993), Bae et al. (2002),
and Van Ginkel et al. (2008)
Lozier et al. (N.D.)
Yu & Kupferle (2008), Dortsiou et al. (2009), Goltz & Parker, 2010/2011,
and Ionex SG Limited (2011)
3.6.1 Electrochemical Destruction of Nitrate in Waste Brine
Research by two different groups is focused on electrochemical destruction of nitrate for the treatment
of waste brine.
First, two major companies are collaborating on the development of a system which incorporates IX
with electrochemical destruction of nitrate. With the removal of nitrate from spent brine, the brine can
be recycled for reuse in regeneration (Goltz 2010; Goltz & Parker 2010/2011). Spent brine is treated
following IX treatment. With electricity distributed over a high surface area electrode, upon contacting
the electrode surface, nitrate in the brine waste is reduced to nitrogen gas. In the overall reaction,
nitrate is reduced and water is oxidized producing nitrogen gas and oxygen. Possible reduction to
ammonia/ammonium is accounted for in the process. Laboratory tests have been successful and
planning of site tests is underway to examine system performance across a variety of raw water
characteristics. The potential benefits of this brine treatment alternative are in the increased
sustainability and the decreased disposal costs. The objective is to optimize the process such that the
savings on disposal costs, especially for inland communities, outweigh the increased electricity costs of
the process.
Second, a company based in the United Kingdom, Ionex SG Limited, has developed and is currently
testing a patented brine treatment system utilizing an electrochemical cell for the destruction of nitrate
(Ionex SG Limited 2011). Following resin regeneration, spent brine is passed through the cell and nitrate
is converted to nitrogen and oxygen gases through interaction with a rhodium catalyst (Figure 17).
Treated brine can be subsequently reused for regeneration, minimizing waste brine volume as well as
the overall salt consumption of the ion exchange system. The lifespan of the cell has been laboratory
tested and is estimated to operate efficiently for at least 15 years through a mechanism of automatic
maintenance of the reactive surface (Tucker et al. 2004; Ionex SG Limited 2011). The brine treatment
system is currently being pilot tested at a location in California through collaboration with UC Davis. A
cost benefit analysis by Ionex indicates that brine disposal costs would be significantly reduced; chemical
and power costs of the brine treatment system balance with existing chemical costs for typical ion
exchange systems.
Technical Report 6: Drinking Water Treatment for Nitrate
115
Figure 17. Schematic of the brine treatment system developed by Ionex SG Limited. (Source: Ionex SG Limited
2011.)
3.6.2 Catalytic Treatment of Waste Brine
Calgon Carbon is working with the University of Illinois to develop a brine recovery system with the goal
of up to 90% brine recovery for reuse using Pd-based catalytic treatment (Drewry 2010). The following
information was provided by Dr. Charles Werth (2010) from the University of Illinois.
As illustrated in Figure 18, “The spent brine solution is equilibrated with hydrogen in a gas-liquid
membrane, and subsequently treated to remove nitrate in the packed bed catalyst system containing
Pd-In on granular activated carbon (GAC). The treated brine is then put back into a holding tank and
reused when ion exchange breakthrough occurs again” (Werth 2010).
Figure 18. Schematic of an ion exchange system with brine regeneration coupled with catalytic treatment of
brine for reuse. (Source: Werth 2010.)
Technical Report 6: Drinking Water Treatment for Nitrate
116
Advantages of this brine treatment alternative include conversion of nitrate mainly to nitrogen gas,
avoidance of the need for brine waste disposal, and rapid reduction of nitrate with the Pd-based
catalyst. Disadvantages include the use of flammable hydrogen gas, some conversion of nitrate to
ammonia, “the cost of Pd and potential fouling of the catalyst which requires regeneration using a
strong oxidant like hypochlorite (Chaplin et al. 2007)” (Werth 2010). Catalytic removal of nitrate has not
yet been implemented at the full-scale, but “catalytic systems have been used to remove chlorinated
solvents at contaminated groundwater field sites, and they appear to be economically competitive
(Davie et al. 2008)” (Werth 2010). Dr. Werth stated, “Catalytic systems show great promise for
removing nitrate from IX brines, but pilot-scale studies are needed to evaluate the economic viability.”
3.7 Residential Treatment (Point-of-Use, Point-of-Entry)
Point-of-Use (POU) and Point-of-Entry (POE) water treatment devices can be used to address high
nitrate levels and other constituents of concern at the residential scale. A POU treatment device is
installed for the purpose of reducing contaminants in drinking water at a single tap, typically the kitchen
tap. A POE treatment device is installed for the purpose of reducing contaminants in drinking water
entering a house or building.
Treatment technologies for POU and POE systems, used to address nitrate contamination, include IX,
RO, and distillation (Mahler et al. 2007). IX is generally considered more for POE than for POU and
requires disposal of concentrated waste brine. RO systems require more maintenance and have lower
water recovery, resulting in a larger waste volume (Mahler et al. 2007). However, according to the New
Hampshire Department of Environmental Services (2006), RO “is the most cost-effective method for
producing only a few gallons of treated water per day” (NHDES 2006). While distillation can require
lower maintenance, energy demands are higher than the other options. Distillation systems are
generally intended as POU devices as they remove all minerals and produce water that is aggressive
towards plumbing materials.
POU units are installed either under the counter or on the counter top, preferably by a licensed
professional. The treatment units generally consist of several stages; for example, a POU RO system can
consist of a pre-treatment filter, an RO stage, and a post-treatment filter. The system can also include a
storage tank to hold treated water and a conductivity meter to indicate when maintenance is required.
POE units, for the treatment of all water entering a building, are larger and require more piping.
Certification to the relevant ANSI/NSF standards by an ANSI accredited third party certifier ensures the
safety and performance of the residential treatment systems. In the U.S., the following certifiers have
been accredited by ANSI to certify drinking water treatment systems:

Canadian Standards Association International (www.csa-international.org);

International Association of Plumbing & Mechanical Officials (www.iapmo.org);

NSF International (www.nsf.org);

Underwriters Laboratories Inc. (www.ul.com); and
Technical Report 6: Drinking Water Treatment for Nitrate
117

Water Quality Association (www.wqa.org).
Numerous RO devices for nitrate removal are certified to the ANSI/NSF standard specific to RO POU
devices: NSF Standard 58 - Reverse osmosis drinking water treatment systems (NSF 2009). Additionally,
the Water Quality Association, an accredited certifier, lists two POU ion exchange devices for nitrate
removal that are certified to NSF Standard 53: Drinking Water Treatment Units – Health Effects (Water
Quality Association 2011). All the technologies listed above are capable of reducing nitrate levels;
however, proper maintenance of the treatment equipment is fundamental to ensure the provision of
safe drinking water. Additionally, it is important to conduct periodic testing (annually or as
recommended by the manufacturer) using an accredited laboratory on both the influent water and the
water produced by the treatment system to verify that it is working effectively.
CDPH provides a list of approved POU devices for nitrate treatment consisting predominantly of RO
devices (CDPH 2011). Published cost information for POU systems is listed in Table 16. Based on a
survey in Minnesota, “the average cost of nitrate removal systems was $800 to install and $100 per year
to maintain” (Lewandowski 2008, p. 92A). Providing a more detailed cost analysis, the U.S. EPA has
developed a cost estimating tool for the use of POU and POE devices (U.S. EPA 2007; U.S. EPA 2011).
It is important to note that water systems are responsible for meeting federal, state, and local
requirements and the allowable uses of POU/POE devices vary by state. Current California regulations
enable small public water systems to use POU devices to meet the nitrate MCL for up to three years,
with certain restrictions, including the following (California Code of Regulations 2011, p. 2):
“…a public water system may be permitted to use point-of-use treatment devices (POUs) in lieu of
centralized treatment for compliance with one or more maximum contaminant levels… if;
(1) the water system serves fewer than 200 service connections,
(2) the water system meets the requirements of this Article,
(3) the water system has demonstrated to the Department that centralized treatment, for the
contaminants of concern, is not economically feasible within three years of the water system’s submittal
of its application for a permit amendment to use POUs,
… no longer than three years or until funding for the total cost of constructing a project for
centralized treatment or access to an alternative source of water is available, whichever occurs first….”
Technical Report 6: Drinking Water Treatment for Nitrate
118
1
Table 16. Costs of POU treatment for nitrate removal.
Upfront Investment
Annual Costs
Comments
Ion Exchange
$660 – $2425
Salt costs ($3.30 – $4.40/bag)
Distillation
4-10 gal/d
$275 – $1650
$440 – $550/yr + electricity
Requires scale removal, higher
energy use
Reverse Osmosis
2-10 gal/d
$330 – $1430
$110 – $330/yr + electricity
Requires filter replacement, high
maintenance, lower water
recovery
Requires disposal of brine waste
Costs have been adjusted to 2010 dollars, unless indicated otherwise.
1
Mahler et al. (2007).
Technical Report 6: Drinking Water Treatment for Nitrate
119
4 Tulare Lake Basin and Salinas Valley - Water Quality Analysis
As mentioned above in the discussion of treatment technologies, water quality is a key variable in both
treatment selection and cost. Table 17 is a summary of water quality data of high nitrate wells across
both the Tulare Lake Basin and the Salinas Valley. Constituents that interfere with treatment (e.g.,
sulfate) or affect treatment technology selection (e.g., TDS) are included as well as co-contaminants.
Table 17 lists water quality data for all wells with raw water monitoring data in the CDPH water quality
database from 2006 – 2010 having nitrate levels above the MCL, including both abandoned and inactive
wells, to enable consideration of the complete range of scenarios. This water quality summary
highlights the wide range of water quality characteristics encountered in the region of interest. The
GAMA Priority Basin Projects provide additional water quality information including the basins within
the study area (USGS 2011).
Table 17. Summary of water quality data of high nitrate wells in the Tulare Lake Basin and Salinas Valley.
(Source: CDPH PICME and WQM databases.)
Constituent
Average
Min
Max
# Samples
# PWS
# Sources
Units
64.69
45.1
402
1705
159
209
mg/L (as NO3)
1
-
-
2
1
1
mg/L (NH3-N)
Sulfate
116.43
3.7
2300
1594
78
111
mg/L
pH (Lab)
7.91
6.38
9.6
1582
87
120
pH (Field)
7.12
6.52
7.85
1186
3
7
Temperature
19.71
3
24.4
780
5
10
Hardness
344.7
6.7
5000
1562
88
121
mg/L as CaCO3
Iron
126.34
0
5700
1586
84
117
ug/L
Manganese
11.86
0
400
1559
83
116
ug/L
Chloride
100.04
3.5
16000
2502
78
111
mg/L
Silica
1693.31
28
21000
71
4
5
mg/L
TDS (Conductance)
856.65
23
43600
4176
101
136
TDS (TDS)
780.04
120
28700
2143
78
111
mg/L
Alkalinity (Total)
203.85
32
340
1572
79
112
mg/L as CaCO3
Arsenic
3.24
0
53
2228
99
137
ug/L
Chromium (Total)
2.9
0
45
1785
96
132
ug/L
Chromium (Hex)
1.19
0.2
3.5
20
2
2
ug/L
Perchlorate
3.09
0
2000
2637
107
138
ug/L
Uranium
15.64
8.4
58
532
3
5
ug/L
TOC
3.61
1.2
6.6
85
1
1
mg/L
Turbidity (Lab)
0.55
0
8.9
1494
74
108
NTU
Nitrate as NO3
Ammonia
Technical Report 6: Drinking Water Treatment for Nitrate
o
C
120
4.1 Water Quality - Treatment Interference
The most commonly employed nitrate treatment method, ion exchange (IX), is highly sensitive to
competing anions in the treatment stream. With the use of generic anion exchange resin for nitrate
treatment, sulfate will out-compete nitrate for resin sites and, as sulfate levels in source water increase,
the resin capacity for nitrate will decrease. Under such circumstances, the cost of more frequent
regeneration, associated chemicals and disposal may make ion exchange less feasible. Nitrate dumping
can also be a problem, resulting in effluent nitrate levels higher than influent levels due to sulfate
displacing nitrate on the resin. To address these concerns, nitrate selective resin can be used, which is
more expensive, but can maintain a higher capacity for nitrate. At the highest levels in the above listed
sulfate range, alternative treatment options would likely become more cost-effective.
High hardness, silica, TSS, turbidity, manganese, and iron can impact most nitrate treatment options
requiring additional steps for pretreatment such as filtration and anti-scalant addition to avoid resin (IX)
or membrane fouling (RO and EDR). Cleaning and post-treatment requirements can also be affected,
thus increasing system complexity and overall costs.
4.2 Water Quality - Co-contaminants
The need for multiple contaminant removal is a key factor in the selection of the most appropriate
treatment option. While IX can effectively remove several co-contaminants, this technology cannot
address all constituents of concern and alternative options should be considered with particularly poor
quality waters. IX has been used for simultaneous removal of perchlorate and nitrate, and arsenic and
nitrate; however, specific resins may be required to optimize multiple contaminant removal, resulting in
higher costs than IX for nitrate removal alone. Figures 19 – 22 highlight the co-occurrence of nitrate
with other constituents of interest in the Tulare Lake Basin and Salinas Valley.
Figure 19 maps raw water nitrate levels above the MCL (45 mg/L as nitrate) including both active and
inactive well data from 2006 – 2010. Figure 20 maps high nitrate wells with high arsenic levels for which
IX may still be considered or for which RO may be a more suitable treatment option, depending on the
priorities of a given system. Figure 21 maps high nitrate wells with high perchlorate levels; again IX may
be considered under such circumstances. Alternatively, biological denitrification may be implemented
to simultaneously remove both constituents while avoiding the brine disposal problem. Last, Figure 22
maps high nitrate wells in which at least 1 of 4 major pesticides has been detected (bromacil, simazine,
atrazine, and DBCP). The co-occurrence of nitrate and pesticides is important on two fronts. With
pesticide levels above the MCL, treatment requirements will change. RO may be implemented to
address the multiple contaminants or IX could be used for nitrate and activated carbon for pesticides.
Regardless of the selected option, treatment for nitrate and pesticides will be more expensive than
treatment for only nitrate. Additionally, the co-occurrence may be indicative of the source of nitrate
contamination.
Technical Report 6: Drinking Water Treatment for Nitrate
121
Figure 19. Raw water nitrate levels exceeding the MCL (45 mg/L as nitrate). (Source: CDPH PICME and WQM Databases.)
Technical Report 6: Drinking Water Treatment for Nitrate
122
Figure 20. Raw water high nitrate wells with high arsenic levels. (Source: CDPH PICME and WQM Databases.)
Technical Report 6: Drinking Water Treatment for Nitrate
123
Figure 21. Raw water high nitrate wells with high perchlorate levels. (Source: CDPH PICME and WQM Databases.)
Technical Report 6: Drinking Water Treatment for Nitrate
124
Figure 22. Raw water high nitrate wells with pesticides detected. (Source: CDPH PICME and WQM Databases.)
Technical Report 6: Drinking Water Treatment for Nitrate
125
Through the investigation of local water quality data, the relationship between well depth and the
incidence of nitrate and arsenic emerged as a potential concern for water systems drilling deeper wells
to reach groundwater with lower nitrate levels. The incidence of nitrate impacted groundwater was
suspected to decrease with well depth while the incidence of arsenic impacted groundwater was
suspected to increase with well depth. Further analysis of this option requires that well screen depth is
known in addition to well water quality. Unfortunately, for most wells with water quality information,
depth information is not available (See Technical Report 4 (Boyle et al. 2012) for additional information
on wells data). All wells having depth information and arsenic testing data were included, as were all
wells having depth information and nitrate testing data (CDPH PICME [Permits Inspection Compliance
Monitoring and Enforcement] and WQM [Water Quality Monitoring] databases). The available dataset
leads to a potential bias as it excludes wells with testing data for which depth information was
unavailable. For the examination of nitrate and depth, the depth to the top of the screened interval was
used; depth categories are based on the minimum screened depth of the well. For the examination of
arsenic and depth, well depth was calculated as the sum of the depth to the top of the screen and the
length of the screen; depth categories are based on the maximum screened depth of the well. Nitrate
and arsenic levels were averaged for each well across all available tests from 2006 – 2010 to avoid bias
caused by having many samples for some wells and only few samples for others. Constituent
concentrations were subsequently averaged across all wells in each depth category.
No relationship was found in the Salinas Valley (Figure 23); however this may be due, in part, to the
more limited sample size of Salinas Valley wells (192 wells for nitrate analysis, 142 wells for arsenic
analysis) in comparison with the sample size of Tulare Lake Basin wells (826 wells for nitrate analysis,
741 wells for arsenic analysis). In the Tulare Lake Basin, the variation between individual wells within
each depth category and across depth categories leads to inconclusive results lacking statistical
significance, despite the suggestion of the expected trend (Figure 24). However, in the context of the
nitrate and arsenic MCLs, results in the Tulare Lake Basin suggest an increase in the incidence of arsenic
MCL exceedance with well depth and a decrease in the incidence of nitrate MCL exceedance with well
depth (Figure 25). Additional data are necessary for definitive confirmation of this trend and local
conditions can vary significantly as water quality varies substantially with well location, well design, and
subsurface geology.
Technical Report 6: Drinking Water Treatment for Nitrate
126
-
Figure 23. Salinas Valley [As] versus total well depth (deepest water) and [NO3 ] versus depth to top of screen
(shallowest water). [1 ft=0.30 meters]
-
Figure 24. Tulare Lake Basin [As] versus total well depth (deepest water) and [NO3 ] versus depth to top of
screen (shallowest water). [1 ft=0.30 meters]
Technical Report 6: Drinking Water Treatment for Nitrate
127
Figure 25. Tulare Lake Basin: Incidence of nitrate and arsenic MCL exceedance with well depth. [1 ft=0.30
meters]
4.3 Water Quality and Treatment Selection
Within the drinking water community, the treatment options typically considered to address nitrate
contamination are IX and RO. Other technologies are available or emerging (EDR, BD, CD) because,
under some circumstances, the alternatives offer advantages that IX and RO cannot. New technologies
will continue to be investigated and developed because no single option is ideal for all situations. There
is not a nitrate treatment option currently available that can address all possible scenarios at a lower
cost than all other options. The following diagram is a rough guide for treatment technology selection
based on water quality concerns and possible priorities for a given water source or system (Table 18).
This diagram includes generalizations and is not intended to be definitive. In the selection of nitrate
treatment technologies the unique needs of an individual water system must be assessed by
professional engineers to optimize treatment selection and design.
As Table 18 shows, the most appropriate method to address nitrate contamination can be influenced by
influent nitrate concentrations as well as other water quality parameters. Nitrate levels well above the
Technical Report 6: Drinking Water Treatment for Nitrate
128
MCL may lead to the selection of one treatment option while nitrate levels just above the MCL may be
more cost-effectively addressed with a different treatment option. Table 19 lists several scenarios as an
example of appropriate options based on influent nitrate level and water system characteristics.
1
Table 18. Comparison of major treatment types.
Concerns
IX
RO
EDR
BD
CD
Priorities
IX
High Nitrate
Removal
High Hardness Not
a Major Concern
High TDS
Removal
Reliability
Arsenic
Removal
Training/ Ease of
operation
Radium and
Uranium
Removal
Minimize Capital
Cost
Chromium
Removal
Minimize Ongoing
O&M Cost
Perchlorate
Removal
Minimize
Footprint
RO
EDR
BD
CD
Industry
Experience
Good
1

Poor
Unknown
(blank)
Ease of Waste
Management
Ion Exchange (IX), Reverse Osmosis (RO), Electrodialysis Reversal (EDR), Biological Denitrification (BD), Chemical
Denitrification (CD). This table offers a generalized comparison and is not intended to be definitive. There are
notable exceptions to the above classifications.
1
Table 19. Influence of nitrate concentration on treatment selection.
Option
Practical Nitrate Range
Blend
10 – 30% above MCL
Considerations
Dependent on capacity and nitrate level of blending sources.
Dependent on regeneration efficiency, costs of disposal, and salt usage.
Brine treatment, reuse, and recycle can improve feasibility at even higher
nitrate levels.
Dependent on availability of waste discharge options, energy use for
RO
Up to many X the MCL
pumping, and number of stages. May be more cost-effective than IX for
addressing very high nitrate levels.
Dependent on the supply of electron donor and optimal conditions for
denitrifiers. Ability to operate in a start-stop mode has not yet been
BD
Up to many X the MCL
demonstrated in full-scale application; difficult to implement for single
well systems. May be more cost-effective than IX for addressing high
nitrate levels.
1
Based on contact with vendors and environmental engineering consultants.
IX
Up to 2X MCL
Technical Report 6: Drinking Water Treatment for Nitrate
129
5 Addressing Nitrate Impacted Potable Water Sources in
California
In the Tulare Lake Basin and Salinas Valley, current and historical methods to address nitrate
contamination of potable water supplies include well abandonment, destruction, and inactivation;
blending; and treatment. The incidence of well abandonment, destruction, or inactivation in California
was explored through analysis of the CDPH PICME and WQM databases. Through collaboration with
CDPH, systems treating or blending to address nitrate contamination were identified and a survey was
conducted to collect additional information, including the costs of treatment.
5.1 Well Abandonment, Destruction, and Inactivation
If alternative source wells are available, costly treatment is often avoided through abandonment or
inactivation of wells. However, wells must be properly destroyed or abandoned, in accordance with
local requirements, to avoid hazardous conditions and the potential for groundwater contamination.
The cost of proper well destruction and abandonment varies with numerous factors including depth,
subsurface conditions, well type, and well construction. The minimum cost to properly destroy a 300 –
400 ft well is ~$15,000; use of best practices would increase cost (Aegis Groundwater Consulting
2011).20
To assess the incidence of well abandonment and inactivation due to nitrate contamination, an analysis
of the CDPH PICME and WQM databases was performed. Nitrate records from 2006 – 2010 for wells
labeled as abandoned, destroyed, or inactive were examined. Wells with at least one nitrate test above
the MCL and wells including “NO3” or “Nitrate” in the well description were flagged. Table 20 lists the
resulting number of nitrate impacted wells abandoned, destroyed, or inactive in the study area and also
across California; locations are mapped in Figure 26. There is evidence of mislabeling in the
PICME/WQM database. Wells missing from this analysis which may have been abandoned, destroyed,
or inactivated due to nitrate may have records that are not up to date or may be mislabeled. This
analysis utilizes exceedance of the nitrate MCL as an indicator of the reason for well status change;
however, a portion of these wells may have been abandoned, destroyed, or inactivated for reasons
other than nitrate contamination. The purpose of this analysis was to assess the incidence of well
abandonment, destruction, and inactivation due to nitrate contamination. However, the small number
of wells identified as abandoned, destroyed, or inactivated due to nitrate, relative to the total number of
wells in these categories (which were abandoned, destroyed, or inactivated for any number of reasons)
leads to two possible conclusions: the reason for well status change is not consistently identified in the
CDPH database or there are simply very few wells in these categories. However, comparison of the
frequency of abandonment, destruction, and inactivation of wells due to nitrate within the study area
20
Using best practices to properly destroy wells, “all wells would be perforated top to bottom, a high-grade cement-sand
concrete would be used, and the concrete would be pressure grouted into the formation and then allowed to fill the well”
(Aegis Groundwater Consulting 2011). Use of best practices for well destruction would increase the cost above the $15,000
minimum.
Technical Report 6: Drinking Water Treatment for Nitrate
130
with those across California indicates that the study area accounts for ~22% of such wells across the
state; a disproportionate number as the total number of wells in these categories accounts for only
~13% of the CA total. Analysis of the frequency of abandoned and destroyed wells and their relevance
to nitrogen loading is discussed in Technical Report 2, Section 9, including agricultural wells (Viers et al.
2012).
Table 20. Incidence of abandonment, destruction, and inactivation of nitrate impacted drinking water wells.
1
Nitrate Impacted Wells
Total Wells
SV
Study Area Total
CA
Study Area Total
CA
Destroyed
0
1
9
217
2,315
Abandoned
1
3
28
494
2,584
Inactive
2
35
138
1,001
8,253
39
1,712
Total
36
3
175
13,152
22% of CA total
13% of CA total
1
Source: CDPH PICME and WQM databases. There is evidence of mislabeling in the PICME/WQM
database. Wells missing from this analysis which may have been abandoned, destroyed, or inactivated due
to nitrate may have records that are not up to date or may be mislabeled. This analysis utilizes exceedance
of the nitrate MCL as an indicator of the reason for well status change; however, a portion of these wells
may have been abandoned, destroyed, or inactivated for reasons other than nitrate contamination.
TLB
1
2
33
Technical Report 6: Drinking Water Treatment for Nitrate
131
Figure 26. Location of nitrate impacted abandoned, destroyed, and inactivated wells. (Source: CDPH PICME and
WQM Databases.)
Technical Report 6: Drinking Water Treatment for Nitrate
132
5.2 Survey of Blending and Treating Systems
Complementing the detailed cases studies for each of the treatment types (above), a survey was
conducted to assess full-scale application of nitrate treatment in California and specifically in the Tulare
Lake Basin and Salinas Valley. The survey (Figure 27) was designed to gather detailed information on
treatment type, water quality parameters affecting treatment, details of the treatment system, and cost
information. Systems were contacted via phone and email and the survey packet was emailed
whenever possible for ease of response. The survey packet included a letter of introduction, a brief
project description, and the digital survey. Whenever possible, systems were contacted via phone and
email for clarification of submitted responses and to gather additional information.
The list of water systems treating and/or blending to address nitrate contamination was developed with
assistance from CDPH and analysis of the CDPH PICME and WQM databases. CDPH compiled a list of
systems across CA treating and/or blending for nitrate after completing an internal review to ensure the
provision of the most comprehensive list possible. Analysis of systems listed in the PICME and WQM
databases confirmed treating systems based on nitrate levels and descriptions of individual systems and
sources. County regulated systems treating and/or blending for nitrate were subsequently determined
through contact with the individual county health departments and added to the list. The survey focus
was treating systems, but several blending systems were also included.
Technical Report 6: Drinking Water Treatment for Nitrate
133
Figure 27. Digital survey distributed to drinking water systems treating and/or blending to address high nitrate
levels.
Of the 42 systems identified as treating for nitrate throughout CA, 26 systems completed the survey.
Statewide systems are mapped in Figure 28 and systems in the study area of interest are mapped in
Figure 29. Whenever possible, systems are blending to address the nitrate problem, accounting for
~56% of the statewide systems in Figure 28.
Technical Report 6: Drinking Water Treatment for Nitrate
134
Figure 28. California drinking water systems treating and/or blending for nitrate. (Source: CDPH Internal
Review of facilities and contact with facility and county representatives.)
Approximately 70% of treating systems across CA are using IX and ~20% are using RO. Several locations
have implemented both RO and IX, primarily to address salinity as well as nitrate. Biological treatment is
being implemented at two locations in CA. After successful completion of a one-year demonstration
study, a system in Rialto, CA, is installing a biological treatment system primarily to address perchlorate
contamination of drinking water. The water system also has a history of nitrate contamination and the
Technical Report 6: Drinking Water Treatment for Nitrate
135
biological treatment system provides the potential to treat their high nitrate source(s) as well.
Construction of the full-scale biological treatment system is underway. In Riverside, CA, biological
treatment has been investigated for the treatment of the RO bypass stream to increase total plant
capacity. See Section 3.4.5 Biological Denitrification - Case Studies, for detailed case studies of these
unique systems.
Focusing on the Tulare Lake Basin and the Salinas Valley (Figure 29), 23 systems were found to be
treating and/or blending to address the nitrate problem (10 blending systems, 10 IX systems, and 3 RO
systems).
Figure 29. Drinking water systems treating or blending for nitrate in the Tulare Lake Basin and Salinas Valley.
(Source: CDPH Internal Review of facilities and contact with facility and county representatives.)
Table 21 lists the population ranges and nitrate levels of blending, IX, and RO systems in the study area.
The IX systems cover the widest population range; however, it is important to note that some large
systems using IX for nitrate treatment also use blending. For each system the minimum, maximum, and
average nitrate concentration across all active wells were determined, then the average of each of those
categories across all systems for each of the treatment options was calculated to illustrate the typical
maximum, minimum, and average nitrate levels for each treatment type. Of these systems, the average
maximum nitrate level of blending systems is slightly lower than that of treating systems; with lower
Technical Report 6: Drinking Water Treatment for Nitrate
136
nitrate levels and access to a low-nitrate source, the possibility of blending can avoid the need for more
costly treatment. Sixty percent of the IX and RO systems in Figure 29 have only a single active well and
40% of the blending systems have only two active wells. Water quality changes and increasing nitrate
levels could be particularly problematic for these one- and two-well systems. Even where blending is
successfully meeting today’s needs, it may be precarious to assume or expect that water systems can
rely solely on blending for compliance into the future.
Table 21. Population and nitrate levels of systems in the study area treating and/or blending for nitrate.
Average Raw Nitrate (mg/L as nitrate)
Ion Exchange
Reverse Osmosis
Blending
Population Range (Total)
Max.
Min.
Avg.
25 – 133,750 (261,200)
71
15
40
45 – 6,585 (6,760)
75
24
41
45 – 25,500 (83,475)
64
3
32
An example of a blending system in Tulare County (Figure 30) illustrates the complexity of even a simple
blending system. This system has seven wells, two of which are high in nitrate (wells 8 and 11 in red).
Most of the year the high nitrate wells are inactive, but with high demand in summer, the system blends
a high nitrate source with other wells. Table 22 lists nitrate levels, depth, and capacity of the system’s
source wells. It is interesting to note that the high nitrate wells have the highest capacity and are
actually some of the deeper wells. Increasing nitrate levels in the low nitrate wells would be cause for
concern as the system’s blending program would be affected. This is one simple example of hundreds of
scenarios. Even with this simple blending system, there are several complicating factors including
differences in capacity, seasonal variation, and the variability of nitrate levels in wells that are very close
together. Extrapolating this concept over the entire study area, the case by case nature of addressing
the nitrate problem becomes more apparent.
Technical Report 6: Drinking Water Treatment for Nitrate
137
Figure 30. Wells of a blending system in Tulare County. (Source: Contact with facility/survey.)
Table 22. Nitrate level, well depth and well capacity for a Tulare County blending system.
Well #
Max Nitrate
(mg/L as nitrate)
Total Depth
(ft)
Depth to Top of
Screen (ft)
Capacity
(gpm)
05
10
255
163
153
06
12
328
30
174
07
7.8
296
94
161
08
78
393
250
378
09
11
398
160
150
11
81
400
340
318
12
11.8
470
180
170
Case studies of nitrate treatment systems are included above in the various treatment technology
sections.
Technical Report 6: Drinking Water Treatment for Nitrate
138
6 Treatment Cost Analysis
In the estimation of treatment costs, there are two major categories to consider: capital costs and O&M
costs. Capital costs refer to the upfront investment required for the design, implementation, and
installation of the treatment system. O&M costs refer to the annual costs for operating and maintaining
the system. Based on U.S. EPA cost estimating procedures, developed through the Technology Design
Panel, capital costs can be further categorized as follows (U.S. EPA 2000; U.S. EPA 2005):
Process Costs
Manufactured Equipment
Concrete and Steel
Electrical & Instrumentation
Pipes & Valves
Construction Costs
Sitework & Excavation
Subsurface Considerations
Standby Power
Contingencies
Interest During Construction
Engineering Costs
Contractor Overhead and Profit
Engineering Fees
Legal, Fiscal, and Administrative Fees
Indirect Costs
Housing
Permitting
Land
Training
Piloting
Public Education
The cost analysis detailed below was performed in accordance with U.S. EPA cost estimation procedures
(U.S. EPA 2000). Total capital costs were converted to annualized capital costs ($/kgal) based on Eqn.
21.
Annualized Capital Cost = [Capital Cost ($) * Amortization Factor]
/ [Flow (MGD) * 1000 kgal/mgal * 365 days/year]
(Eqn. 21)
An amortization value of 0.0802 was used which corresponds with an interest rate of 5% over 20 years
(Eqn. 22).
Amortization Factor = (1+i)N/((1+i)N – 1)/i)
(Eqn. 22)
Where i = interest rate and N = number of years
Annual O&M costs were calculated based on Eqn. 23 to convert total annual O&M costs to $/kgal.
O&M Cost ($/kgal) = [O&M Cost ($)]
/ [Flow (MGD) * 1000 kgal/mgal * 365 days/year]
(Eqn. 23)
Annualized Capital Cost ($/kgal) and O&M Cost ($/kgal) were summed to determine Total Annualized
Cost ($/kgal).
Technical Report 6: Drinking Water Treatment for Nitrate
139
In the U.S. EPA 1979 Cost Estimating Manual (U.S. EPA 1979), cost information is included for anion
exchange for nitrate removal; however, for a more recent set of cost indices, cost information reported
for anion exchange and membrane processes for arsenic treatment will be used here for comparison
with collected cost information (U.S. EPA 2000). Similarly, in a recent AWWA publication examining the
national impact of changing the nitrate MCL, cost curves of anion exchange for arsenic removal were
used in the estimation of nitrate treatment costs. “USEPA’s cost curves were chosen because they are
generally used for developing national compliance costs and because arsenic and nitrate use
comparable regenerable IX treatment” (Weir & Roberson 2011, p. 49). Based on the U.S. EPA cost
curves of IX for arsenic removal, costs by system size using regenerable IX are listed in Table 23, ranging
from $0.22/kgal for a 10 MGD system to $4.60/kgal for a 0.01 MGD system. Disposal costs were not
included in the U.S. EPA cost estimates of IX for arsenic removal.
1
Table 23. Cost estimation using U.S. EPA cost curves of IX for arsenic removal.
System Capacity
10
2
1
0.1
0.01
1
U.S. EPA 2000.
Annualized Capital Cost
($/kgal)
0.09
0.13
0.26
0.21
0.79
O&M Cost
($/kgal)
0.13
0.23
0.46
0.70
3.81
Total Annualized Cost
($/kgal)
0.22
0.36
0.72
0.91
4.60
For the cost analysis detailed herein, treatment cost information was collected from literature, vendors,
surveys, and contact with existing systems. Factors affecting system cost include facility size (flow rate),
source water quality (including nitrate concentration), environmental factors (temperature), and target
effluent nitrate concentration. Disposal of waste brine can be a significant portion of O&M costs for the
removal technologies (see Section 6.4 Disposal Costs for a more detailed discussion of disposal costs).
Capital costs for treatment can include land, housing, piping, storage tanks, O&M equipment, process
equipment (i.e., vessels, resin, membranes, media, etc.), preliminary testing (pilot studies), permits, and
training. O&M costs for treatment can include resin, media, or membrane replacement (due to loss or
degradation) and disposal; waste residuals disposal or treatment (e.g., brine disposal); chemical use
(salt, anti-scalant, pH adjustment); repair and maintenance; power; and labor. Costs can be difficult to
assess due to inconsistencies in how cost information is reported. Comparison of costs across different
systems is not always valid due to differences in influent water quality parameters, system size, waste
management options, and system configuration. Published costs do not always include comparable
information. The cost information listed in this section is provided as an approximate range of costs.
Costs for implementing treatment may be very different from those listed here. A thorough cost
analysis of design parameters for specific locations would be required for accurate cost estimation. The
information gathered through the survey includes reported costs associated with treating systems in CA.
Assumptions and sources of uncertainty in this analysis of treatment costs include the following:

For certain sources of cost information it is unclear if all components are included in capital
costs (e.g., preliminary planning, pilot testing, installation, administration fees, engineering fees,
Technical Report 6: Drinking Water Treatment for Nitrate
140
building cost, storage, etc.) and O&M costs (e.g., pumping, disposal, labor, energy, chemicals,
etc.). Whenever possible efforts have been made to ensure inclusion of all relevant costs.

Many treatment systems blend treated water with a bypass stream; whenever possible costs
were calculated on the basis of total produced water to accommodate the blending
configuration. For example, an RO system may remove nitrate to very low levels, then blend the
permeate with a bypass stream, raising nitrate levels to the distribution goal (and restoring
other ions).

Capital costs generally increase with design capacity, but some systems “over design” with a
design capacity significantly greater than the actual flow. The calculation of annualized capital
costs are based on average flow rather than design capacity whenever possible to provide
capital costs per unit of produced water.

O&M costs are based on actual average flow, rather than design capacity, whenever possible.

Costs were adjusted to 2010 dollars.

Costs of drilling a new well were excluded from the treatment cost analysis to ensure
appropriate comparison.

Costs of systems in the design phase are anticipated costs.

Several sample costs of electrodialysis and biological treatment systems designed for the
removal of other constituents were included; based on communication with water treatment
engineers and vendors, the costs for treatment for nitrate removal should be similar.

Costs were collected for systems with wide-ranging characteristics including variation in system
size, nitrate levels, co-contaminants, and other water quality constituents.

Several systems reported renting treatment equipment and/or contracting O&M services,
resulting in very different capital and O&M costs.

Given only equipment costs (e.g., from vendors), total capital costs were modeled based on U.S.
EPA scaling factors (U.S. EPA 2000).
6.1 Costs by Treatment Type
Comparison of the average total annualized cost for IX, RO, EDR, and BD across all system sizes
highlights RO as the most expensive option (Figure 31). EDR costs are for a limited number of systems
including costs for the treatment of constituents other than nitrate and may not be representative of
actual EDR costs for nitrate removal. Based on preliminary estimates, biological treatment has the
potential to be cost competitive. Costs for IX, RO, and BD are broken down into three system size
categories to illustrate the variability in cost with system size (Figure 32, Figure 33, and Figure 34,
respectively). Note the much higher cost for system sizes less than 0.5 MGD for IX (Figure 32) and RO
(Figure 33). Preliminary estimates of BD treatment costs do not illustrate the same degree of variability
with system size (Figure 34); however, BD for nitrate removal from drinking water is an emerging
Technical Report 6: Drinking Water Treatment for Nitrate
141
technology and available cost information is limited. The very high O&M costs for small systems (Figure
32 for IX and Figure 33 for RO) are representative of low flow systems making the cost per 1000 gallons
quite high. This highlights a problem faced by many small systems lacking the benefits of economies of
scale; funding may be available for the initial upfront investment, but with high O&M costs long term
treatment can become unsustainable. Additionally, due to insufficient funds for ongoing costs, small
water systems can be faced with an inability to retain qualified operators which can lead to MCL
violations and insufficient maintenance of the treatment system. (ED/EDR costs are excluded from this
comparison due to insufficient cost information.)
The variability in cost information reported here is due to many factors, including variability in water
quality parameters, site considerations, and the sources of uncertainty in the cost information, as
discussed above. For example, one very small IX system reported the disposal of waste brine to septic, a
low cost option, resulting in significantly lower O&M costs in comparison with other systems.
Figure 31. Average cost comparison of nitrate treatment technologies.
Technical Report 6: Drinking Water Treatment for Nitrate
142
Figure 32. Costs of anion exchange for nitrate treatment.
Figure 33. Costs of reverse osmosis for nitrate treatment.
Technical Report 6: Drinking Water Treatment for Nitrate
143
Figure 34. Costs of biological denitrification in drinking water treatment.
6.2 Costs by System Size
As indicated above, system size is a major factor in determining nitrate treatment costs. Larger
treatment systems will have higher total capital and O&M costs; however, the cost per unit of produced
water generally decreases as system size increases. Large treatment systems have the advantage of
economies of scale. Based on cost information collected from vendors, literature, surveys, and
treatment systems, treatment costs relative to system size are illustrated in the below cost curves for IX
and RO (Figure 35). The development of cost curves for the other technologies was not possible due to
insufficient cost information. The higher relative cost of treatment for smaller systems can be seen
moving toward the vertical axis, with decreasing system size and increasing cost as the curve sweeps
upward. Again, the total cost for RO treatment is higher than that of IX.
Technical Report 6: Drinking Water Treatment for Nitrate
144
Figure 35. Cost curve of IX (blue) and RO (red) for nitrate removal.
Table 24 includes all of the most reliable treatment cost information collected for comparison of cost
ranges across system size categories for IX and RO.
Technical Report 6: Drinking Water Treatment for Nitrate
145
Table 24. Summary of anion exchange and reverse osmosis cost information by system size.
Annualized Costs in $/1000 gallons
System Size (people)
Design Flow Range
(typical average
flow range)
Capital Cost Range (Avg.)
O&M Cost Range (Avg.)
Total Combined Cost
Range (Avg.)
$/1000 gallons
$/1000 gallons
$/1000 gallons
Ion Exchange
0.05 – 1.53 (0.75)
0.28 – 3.81 (1.22)
0.62 – 4.60 (1.97)
Reverse Osmosis
0.47 – 4.40 (2.43)
0.22 – 16.16 (4.22)
0.69 – 19.16 (6.64)
Ion Exchange
0.08 – 0.25 (0.15)
0.15 – 2.63 (0.87)
0.34 – 2.73 (1.05)
0.19 – 1.13 (0.47)
0.23 – 1.15 (0.57)
0.58 – 1.34 (0.93)
0.06 – 0.52 (0.19)
0.12 – 1.69 (0.84)
0.36 – 2.04 (1.06)
0.44 – 0.63 (0.53)
0.91 – 2.76 (1.89)
1.35 – 3.39 (2.59)
Ion Exchange
0.09 – 0.41 (0.26)
0.13 – 1.39 (0.66)
0.22 – 1.81 (0.97)
Reverse Osmosis
0.33 – 1.46 (0.97)
0.40 – 2.21 (1.48)
0.73 – 3.67 (2.38)
Treatment Type
MGD
1
Very Small
(25 – 500)
0.009 – 0.17
(0.002 – 0.052)
Small
(501 – 3,300)
0.17 – 1.09
(0.052 – 0.39)
Medium
(3,301 – 10,000)
1.09 – 3.21
(0.39 – 1.3)
Large
(10,001 – 100,000)
3.21 – 30.45
(1.3 – 15.51)
Reverse Osmosis
1
Ion Exchange
Reverse Osmosis
1
Limited data set for the indicated system size and treatment type.
Technical Report 6: Drinking Water Treatment for Nitrate
146
6.3 Costs by Water Quality Parameters
As highlighted above in the discussion of water quality (Section 4 Tulare Lake Basin and Salinas Valley Water Quality Analysis), if treatment of multiple contaminants is necessary, treatment costs will
generally increase. Similarly, the level of nitrate and water quality parameters that can interfere with
treatment can increase O&M costs. Table 25 lists costs by system size with increasing nitrate levels and
is intended as an example of nitrate treatment cost estimation based on nitrate concentration in source
water. Table 25 is strictly an example and is not intended to be definitive, but only to suggest how
treatment costs might change with increasing nitrate levels. The actual costs with increasing nitrate
level are wide ranging and vary with numerous factors. The percent increase in O&M costs was
modeled based on only two sets of vendor data in which estimates were provided based on given
nitrate levels (low and high). Available data were specifically applicable to estimation of O&M increases
as the nitrate concentration increases from ~1X the nitrate MCL to 2X the MCL. To extrapolate the
exercise further, the same percent increase was used to predict the O&M increase from 2X the MCL to
3X the MCL. It is not possible to accurately estimate or generalize how these costs would translate for
other IX systems as the two vendors provided cost estimates specifically for a system using a selective
resin and a second unique system designed for low brine. Based on the information herein, O&M costs
would be expected to increase even more using conventional IX under the given scenario of increasing
nitrate levels. It is important to note that the treatment system could also be designed differently for
higher nitrate levels (more or larger vessels, in series/in parallel, different bypass ratios, etc.); this is not
included in the table as it would be pure speculation.
Technical Report 6: Drinking Water Treatment for Nitrate
147
1
Table 25. An exercise in the estimation of treatment costs based on appropriate technology for various nitrate levels.
System Size (people)
Very Small (25 – 500)
Small (501 – 3,300)
Medium (3,301 – 10,000)
2
Raw Nitrate Level
Treatment Type
O&M Cost Range (Avg.)
$/1000 gallons
Annualized Combined Cost Range (Avg.)
$/1000 gallons
1X MCL
2X MCL
3X MCL
3X MCL
1X MCL
2X MCL
Ion Exchange
Ion Exchange
Ion Exchange
Reverse Osmosis
Ion Exchange
Ion Exchange
0.28 – 3.81 (1.22)
0.35 – 10.48 (2.13)
0.42 – 17.15 (3.05)
0.22 – 16.16 (4.22)
0.15 – 2.63 (0.87)
0.19 – 7.23 (1.52)
0.62 – 4.60 (1.97)
0.69 – 11.27 (2.88)
0.76 – 17.94 (3.80)
0.69 – 19.16 (6.64)
0.34 – 2.73 (1.05)
0.38 – 7.33 (1.70)
3X MCL
3X MCL
1X MCL
2X MCL
3X MCL
3X MCL
Ion Exchange
3
Reverse Osmosis
Ion Exchange
Ion Exchange
Ion Exchange
3
Reverse Osmosis
0.23 – 11.84 (2.18)
0.23 – 1.15 (0.57)
0.12 – 1.69 (0.84)
0.15 – 4.65 (1.47)
0.18 – 7.61 (2.10)
0.91 – 2.76 (1.89)
0.42 – 11.94 (2.36)
0.58 – 1.34 (0.93)
0.36 – 2.04 (1.06)
0.39 – 5.00 (1.60)
0.42 – 7.96 (2.32)
1.35 – 3.39 (2.59)
1X MCL
Ion Exchange
0.13 – 1.39 (0.66)
0.22 – 1.81 (0.97)
2X MCL
Ion Exchange
0.16 – 3.82 (1.16)
0.25 – 4.24 (1.46)
Large (10,001 – 100,000)
3X MCL
Ion Exchange
0.20 – 6.26 (1.65)
0.29 – 6.68 (1.96)
3X MCL
Reverse Osmosis
0.40 – 2.21 (1.48)
0.73 – 3.67 (2.38)
1
This table is strictly an example and is not intended to be definitive, but only to suggest how treatment costs might change with increasing nitrate levels. The
estimated increase in O&M costs is wide ranging, 25% – 175%, and depends on many factors including water quality parameters, disposal options, resin
capacity, resin type, and ion exchange system design. As nitrate levels increase, salt, disposal, and resin costs for IX will increase (O&M). Reverse osmosis costs
will increase with increasing TDS, but not at the same rate, this cannot currently be estimated. Depending on other water quality parameters, the costs of IX
are predicted to surpass those of RO. In the future, biological denitrification will likely be considered as an option for > 2X the nitrate MCL. Additionally,
increasing the number and/or size of resin vessels to address higher nitrate levels would increase capital costs. O&M costs would still increase; in practice the
system would be designed to optimize costs. O&M increases were considered here as an example. Actual costs with increasing nitrate levels for specific
systems may vary significantly from listed costs and should be assessed by professional engineers.
2
Increases in O&M are estimated from a limited dataset comprised of vendor cost estimates for IX costs with nitrate levels increasing from just above the MCL
to slightly more than double the MCL. All available cost information was included in the 1X MCL scenario as a starting point, including systems with nitrate
levels above 1X the MCL.
3
Limited dataset for the indicated system size and treatment type.
Technical Report 6: Drinking Water Treatment for Nitrate
148
6.4 Disposal Costs
Brine disposal costs for drinking water systems in CA using IX for nitrate treatment vary with several
factors including proximity to a coastal brine line, waste brine volume (e.g., water efficiency), and the
water quality characteristics of waste brine (e.g., salinity). The presence of contaminants other than
nitrate (e.g., arsenic, selenium, uranium, chromium, and vanadium) in the waste stream can have a
significant impact on brine disposal options and costs; disposal to a hazardous waste facility may be
required at a greater cost. Methods for disposal of waste brine or concentrate reported in the survey of
nitrate treatment systems in CA include discharge to a septic tank and leach fields, to a wastewater
treatment plant via a sewer connection, to irrigation ponds (for RO concentrate), to a brine line, and to a
wastewater treatment plant via trucking.
Disposal options are limited in the Central Valley of California due, in part, to the great distance to the
coast. Trucking of waste brine to coastal wastewater facilities, although costly, is sometimes the chosen
disposal option. Typical costs for trucking and disposal of spent IX brine at a coastal wastewater plant
from the Central Valley can be around $0.15/gallon ($150/1000 gallons of waste brine). East Bay
Municipal Utility District (EBMUD), in Oakland, CA, operates a wastewater management program for the
disposal of high salinity and high nitrate wastewater.
O&M costs for the disposal of waste brine reported in the survey of nitrate treatment systems in CA
range from $0.015 to $ 0.05/1000 gallons of treated water. Assuming a high efficiency of 99.5%, O&M
disposal costs range from $3 to $11/1000 gallons of waste brine. This is consistent with the results of a
recent research investigation comparing the life cycle costs of several nitrate treatment options. Meyer
et al. (2010) discuss the costs of multiple brine disposal options including evaporation ponds, deep well
injection, and sewer. Based on vendor estimates, results indicate total brine disposal costs (including
capital and O&M costs) ranging from approximately $7 to $27/1000 gallons of waste brine disposal to
evaporation ponds and approximately $6 to $11/1000 gallons of waste brine disposal to sewer (Table
26). (In the conversion of costs reported by Meyer et al. to the cost per 1000 gallons, an amortization
value of 0.0802 was used which corresponds with an interest rate of 5% over 20 years.) However, it is
important to note that the study by Meyer et al. (2010) was focused on the evaluation of nitrate
treatment in Arizona; location specific characteristics are an important factor affecting disposal costs.
Technical Report 6: Drinking Water Treatment for Nitrate
149
1
Table 26. Brine disposal costs.
Annualized Capital Cost
Average Cost by Waste Volume ($/1000 gallons)
Evaporation Ponds
10.23
Solar Ponds
20.48
Well Injection
12.00
Sewer
2.40
Average Cost by Treated Volume ($/1000 gallons)
Evaporation Ponds
0.046
Solar Ponds
0.063
Well Injection
0.051
Sewer
0.007
1
Based on Meyer et al. 2010.
O&M Cost
Total Annualized Cost
Total Range
5.62
18.80
18.52
5.51
15.85
39.27
30.52
7.91
7 to 27
8 to 88
13 to 111
6 to 11
0.015
0.047
0.077
0.034
0.061
0.110
0.128
0.041
0.03 to 0.14
0.07 to 0.20
0.03 to 0.33
0.02 to 0.12
Costs of resin disposal can also vary with water quality parameters other than nitrate; IX resin removes
not only nitrate, but other contaminants (e.g., arsenic) which can affect disposal options when resin
needs to be replaced. High levels of other contaminants on the resin can require disposal at hazardous
waste facilities and increase disposal costs, although the impact of co-contaminants is more significant
on brine disposal costs than on resin disposal costs. Non-hazardous resin can be land-filled. Using
regenerable resin, requiring replacement only once every 3 – 8 years (WA DOH 2005 and Dow 2010c),
the cost of land-fill disposal of non-hazardous resin is expected to be minimal compared with the
disposal of other waste residuals (waste brine/concentrate). Service contracts are available with various
companies to manage resin replacement and disposal.
In the selection of the most appropriate nitrate treatment option, disposal costs are a significant factor;
consideration of the pros and cons for the unique conditions of an individual water system is not always
straightforward and can be heavily weighted by disposal options. Although other removal technologies
(RO and ED) require concentrate disposal, because IX requires the addition of salt for resin regeneration,
the waste stream consists of not only the nitrate and other ions that have been removed from the
water, but also the spent brine solution used in regeneration. As nitrate levels in source water increase,
IX resin will need to be regenerated more frequently, increasing salt use and brine waste volume. In
contrast, although the recovery rate for RO is significantly lower than that of IX (~80% and >95%,
respectively), the nitrate level that can be addressed with RO is theoretically much higher (in accordance
with the membrane nitrate rejection rate). Recall that RO is used for desalination as well. As the nitrate
concentration in the treatment stream increases, with appropriate pressure, the RO membrane will
continue to reject nitrate, assuming membrane scaling and fouling are properly controlled. In the
comparison of IX and RO as nitrate levels increase, theoretically there is a tradeoff between the O&M
costs for each technology. With increasing nitrate levels, chemical use and waste volume will increase
for IX while power use and membrane maintenance may increase for RO. Excluding all other water
quality parameters, the nitrate level at which the cost of IX exceeds the cost of RO requires more
research.
Technical Report 6: Drinking Water Treatment for Nitrate
150
Lastly, several small water systems included in the nitrate treatment survey indicated disposal of waste
concentrate to a septic system. This highlights an important tradeoff; while small water systems do not
have the advantages of economies of scale, with a low volume waste stream (depending on chemical
composition to avoid negatively impacting septic system function or underlying groundwater), disposal
to septic can avoid other, more costly disposal options.
Technical Report 6: Drinking Water Treatment for Nitrate
151
7 Guidance for Addressing Nitrate Impacted Drinking Water
7.1 Checklist for the Selection of Mitigation Strategy
The following checklist is intended as a general guide for the selection of promising mitigation strategies
for nitrate impacted drinking water (adapted from U.S. EPA 2003b, WA DOH 2005a, and WA DOH
2005b). Questions regarding mitigation strategy development should be directed to the Department of
Public Health.21
1. Monitor nitrate concentration of distributed water and determine compliance status. Quarterly
monitoring may be necessary and public notification requirements must be met.
2. Develop long-term compliance schedule with the Department of Public Health.
3. Determine all pertinent water quality characteristics (nitrate, arsenic and other cocontaminants, pH, TDS, sulfate, etc.).
4. Assess non-treatment options (e.g., removing well from service, blending, consolidation,
development of new sources, etc.). See Decision Tree 1 (Figure 36) and Technical Report 7
(Honeycutt et al. 2012).
5. If non-treatment options are not feasible, determine evaluation criteria for treatment (e.g.,
effluent nitrate goal, operator certification, water demand, and state and local requirements)
and assess treatment options. Choose optimal approach to addressing nitrate impacted
source(s). See Decision Trees 1 and 2 (Figure 36 and Figure 37).
6. Develop preliminary or planning-level cost estimates for capital and O&M costs.
7. Assess design considerations. See Table 4 and Table 6 for details on IX and RO, respectively.
Considerations for ED/EDR and BD are listed in Table 8 and Table 11, respectively.
8. Pilot test the selected solution (engineering professional required).
9. Develop construction-level cost estimates for capital and O&M costs (engineering professional
required).
10. Examine funding options and attain funding (e.g., Drinking water state revolving fund (DWSRF)
loan). See Technical Report 8 (Canada et al. 2012).
11. Implement the selected solution. This may include the development of a pre-design report,
design, obtaining appropriate permits, construction, inspections, and start-up tasks (engineering
professional required).
12. Monitor the system to ensure safe operation and the consistent supply of compliant drinking
water (engineering professional may be required).
21
Additional information can be found at http://www.cdph.ca.gov/certlic/drinkingwater/Pages/default.aspx and
http://www.rcac.org/assets/.online%20materials/CA-DrinkingWater_Jan-June%202012.pdf.
Technical Report 6: Drinking Water Treatment for Nitrate
152
7.2 Decision Trees
Figure 36. Decision Tree 1 - Options to address nitrate impacted drinking water sources (adapted from U.S. EPA
2003b, WA DOH 2005a, and WA DOH 2005b).
Technical Report 6: Drinking Water Treatment for Nitrate
153
Figure 37. Decision Tree 2 - Anion exchange (adapted from USEPA 2003, WA DOH 2005a, and WA DOH 2005b).
Technical Report 6: Drinking Water Treatment for Nitrate
154
8 Summary and Conclusions

Current full-scale nitrate treatment installations in the United States consist predominantly of
ion exchange (IX) and reverse osmosis (RO). Other technologies are available because, under
some circumstances, the alternatives offer advantages that IX and RO cannot. While
electrodialysis (EDR) is a feasible option for nitrate removal from potable water, the application
of EDR is generally limited to high TDS and/or high silica waters. The use of biological
denitrification (BD) to address nitrate contamination of drinking water is more common in
Europe than in the U.S. However, this option is emerging in the U.S. and two full-scale systems
are expected within a few years. Chemical denitrification (CD) may become a feasible nitrate
treatment option in the future; however, the lack of current full-scale implementation suggests
the need for further research, development and testing. New technologies will continue to be
investigated and developed because no single option is ideal for all situations. A single
treatment solution will not fit every community; however, the provision of safe drinking water
for all communities can be achieved using currently existing technology.

Brine reuse and treatment are vital to the continued reliance on IX for nitrate treatment of
potable water. The low brine technologies offer a minimal waste approach and current research
and development of brine treatment alternatives seem to be lighting the path toward future
progress.

In regions with declining water quality and insufficient water quantity, the need to address
multiple contaminants will increase in the future, suggesting the future dominance of
technologies capable of multiple contaminant removal. In this context, for any individual water
source or system, the most appropriate technology will vary with the contaminants requiring
mitigation. Although complex, analysis of the optimal treatment option for pairs and groups of
contaminants will assist in the treatment design and selection. In such scenarios, the best
treatment option for nitrate may not be the most viable overall.

Currently and into the future, selection of the optimal and most cost-effective potable water
treatment options will depend not only on the specific water quality of a given water source, but
also on the priorities of a given water system. If land is limited, the typical configuration
required for biological treatment may not be feasible. If disposal options of brine waste are
costly or limited, implementation of denitrification treatment or development of brine recycling
and treatment may be the most suitable option.

When deciding on nitrate treatment, the characteristics of the water system must be taken into
account as well. With consideration of economies of scale, many rural small water systems
cannot afford to install treatment. Even with financial assistance to cover capital costs, the long
term viability of a treatment system can be undermined by O&M costs that are simply not
sustainable. For such systems, treatment can become more affordable through consolidation of
multiple small water systems into larger combined water systems that can afford treatment as a
Technical Report 6: Drinking Water Treatment for Nitrate
155
conglomerate. With a continued decline in water quality, non-treatment options alone, like
blending or drilling a new well, may become insufficient measures for a water system to provide
an adequate supply of safe and affordable potable water. Especially in rural small communities,
perhaps the most promising approach will be a combination of consolidation and treatment.
Alternatively, separate small treatment facilities can be consolidated under a single agency. For
additional discussion on the comparison of alternative water supply options and associated
costs see Technical Report 7 (Honeycutt et al. 2012).

While current cost considerations are commonly the driving force in selecting nitrate treatment,
it is essential to consider the long term implications of current industry decisions. For example,
it may be cost-effective for a particular system to utilize conventional IX currently, but future
water quality changes (e.g., increasing nitrate levels, co-contamination, high salt loading),
discharge regulations, or disposal fees may lead to an unmanageable increase in costs.
Environmental sustainability in drinking water treatment is being addressed with brine
treatment alternatives and denitrification options. It is important to approach the future of
drinking water treatment with the mindset that environmental sustainability and economic
sustainability are tightly interwoven.

Centralized treatment may not be feasible for widespread rural communities; another approach
to consider is centralized management (e.g., design, purchasing, and maintenance) to minimize
costs.

Point-of-Use (POU) and Point-of-Entry (POE) treatment equipment is an important option to
consider, especially for the provision of safe drinking water from private wells. Unless
connecting to a nearby public water system becomes an option, users relying on domestic wells
have two main alternatives: drilling a new well to attain safe drinking water or installing a POU
or POE device for the treatment of contaminated water. The use of POU and POE treatment
equipment by small public water systems is currently only a temporary option in California and
reliance on these devices for the long-term would require regulatory changes. While POU and
POE treatment equipment has been shown to effectively address nitrate and other
contaminants, it is important to properly maintain these devices to ensure the supply of
consistently safe drinking water.
Technical Report 6: Drinking Water Treatment for Nitrate
156
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Werner, T.E. & von Gottberg, A.J.M. (2005) Five Billion Gallons Later – Operating Experience at City of
Suffolk EDR. GE – General Electric Company, Water & Process Technologies,
http://www.gewater.com/pdf/technical%20papers_cust/americas/english/tp1031en.pdf
Werth, C. (2010) Personal Communication.
WHO (World Health Organization). (2004) Nutrient Minerals in Drinking-Water and the Potential Health
Consequences of Consumption of Demineralized and Remineralized and Altered Mineral
Content Drinking-Water: Consensus of the Meeting,
http://www.who.int/water_sanitation_health/ dwq/nutconsensus/en
Wisniewski, C., Persin, F., Cherif, T., Sandeaux, R., Grasmick, A. & Gavach, C. (2001) Denitrification of
drinking water by the association of an electrodialysis process and a membrane bioreactor:
Feasibility and application. Desalination, 139, 199–205.
Technical Report 6: Drinking Water Treatment for Nitrate
173
Xiong, Z, Zhao, Z. & Pan, G. (2009) Rapid and controlled transformation of nitrate in water and brine by
stabilized iron nanoparticles. Journal of Nanoparticle Research, 11, 807–819.
Yoon, T., Shon, Z.H., Lee, G., Moon, B., Noh, B. & Sung, N. (2001) Parametric studies on the performance
of anion exchange for nitrate removal. Korean Journal of Chemical Engineering, 18, 170–177.
Yu, J. & Kupferle, M.J. (2008) Two-stage sequential electrochemical treatment of nitrate brine wastes.
Water Air and Soil Pollution: Focus, 8, 379–385
Technical Report 6: Drinking Water Treatment for Nitrate
174
10 Appendix
10.1 Tables of Selected Research
Table A.1. Selected research on the use of ion exchange (IX) for nitrate removal.
IX – Nitrate selective resin
IX – Adsorption kinetics
IX – Sulfate competition
IX – Co-contaminants
Compared two different anion exchange resins and studied the influence of other ions on nitrate removal.
IX – Resin residuals and
DBPs
IX – Pilot study
See Also
Dosing and sorption kinetics of Purolite A 520E (SBA resin). Influent nitrate concentration of 22.6 mg/L as N
(100 mg NO3 /L). With no sulfate and chloride the treated bed volumes before breakthrough (BV) and resin
capacity were 451 BV and 126.4 mg NO3 /g resin, respectively. With sulfate and chloride concentrations 10x
that of nitrate, BV and resin capacity were 120 BV and 33.6 mg NO3 /g resin, respectively.
Amberlite IRA 400 resin was found to be a suitable choice for nitrate removal with influent nitrate concentration
of 0.23 – 4.07 mg/L as N (1 – 18 mg NO3 /L) and a 96% removal efficiency.
Competition between sulfate and nitrate ions was explored. For the sulfate specific resin examined, findings
indicate that sulfate selectivity increased with ionic strength.
Samatya et al.
(2006)
Chabani et al.
(2006)
Kim & Benjamin
(2004)
Yoon et al.
(2001)
Quaternary amine groups and nitrosamines carcinogenic DBPs, 3 resins examined. With no disinfectants
(chlorine and chloramine) “release 2 – 10 ng/L”, max of 20 ng/L nitrosamine. “The lack of significant
nitrosamine release in full-scale anion-exchange treatment system after multiple regeneration cycles indicates
Kemper et al.
that releases may eventually subside.” Precursors can be a problem with downstream chloramine use.
(2009)
Upstream disinfection releases of 20 – 100 ng/L (type 1) and 400 ng/L (type 2). Possible problem with IX in POU
with influent containing chlorine/chloramines.
3-year pilot examined RO, IX and biological denitrification in Mashhad, Iran. Treatment goal was a decrease in
Panglisch et al.
nitrate concentration from 26 mg/L as N (115 mg/L as nitrate) to 9 mg/L as N (40 mg/L as nitrate). Raw water
(2005)
with electrical conductivity of 1550 uS/cm, pH of 7.2. Optimal treatment options were deemed to be biological
Dördelmann et
denitrification and RO. In the IX pilot plant pre-treatment consisted of cartridge filtration. Two IX columns
al. (2006, and
containing ~200 L of nitrate selective resins were run in parallel with counter-current regeneration. System
N.D.)
characteristics:
Dördelmann
3
Column diameter: 0.4 m, Bed Volume (BV): 200 L, Bed Depth: 1.6 m, Flow Rate: 1.0 to 3.0 m /h, Specific Flow
(2009)
Rate: 5 to 15 BV/h, Resin replacement every 5 years.
Clifford & Weber (1978), Guter (1982), Clifford (1987), Rash (1992), Clifford (2007), and Johnston & Heijnen (N.D.).
Technical Report 6: Drinking Water Treatment for Nitrate
175
Table A.2. Selected research on the use of reverse osmosis (RO) for nitrate removal.
RO – Pilot Study and
Full-scale Installation
RO – HERO in
Australia
RO – Full-scale uses
methane
RO – Pilot study
comparing IX, RO
and BD
RO – Full-scale
installations
RO – Alternative
disposal options
RO – Membrane
scaling and fouling,
colloidal interaction
RO – Influence of
upstream processes
Brighton, CO: Use of RO in Brighton, CO, for potable water treatment including nitrate removal began operating in 1993 (11000 sq
ft., 4 MGD, total cost of $8,253,000) after the performance of preliminary pilot study (4 membranes were tested). Source water
nitrate concentration of 13 to 23 mg/L nitrate-N or 58 to 102 mg/L nitrate as NO3 (with TDS 800 – 1140 mg/L, hardness 370 – 480
mg/L as CaCO3). Problems with biofouling of membrane and cartridge filters (slime forming Pseudomonas) minimized with antiscalant use. Pretreatment: acid, anti-scalant and filtration. Post-treatment: CO2 stripping (degasifier), disinfection, caustic and zinc
orthophosphate (ZOP) addition. Blending ratio (untreated%:treated%) 20:80(winter) and 60:40 (summer). Waste discharge to
surface water. Additional characteristics: Flux rate < 14.2 gal/sq. ft./day (helps control fouling), 2 stages: 32 : 16 vessels, pressure
of 231 psi, each vessel with 6 8” diameter membranes. Cleaning required every 2 months.
Yalgoo, Australia: RO plant, online in 2007 using high-efficiency reverse osmosis (HERO). Water recovery rates as high as 95%.
More than 85% waste reduction (a low as 10% the waste of conventional RO.) Removes both nitrate and silica from brackish
water.
Inland Empire, CA: Cow Power in Inland Empire, CA: $80 mil. effort is powered by methane gas produced from the high population
th
of cows in that region. Online since 2002, this plant provides 1/5 of regional demand.
Mashhad, Iran: 3-year pilot examined RO, IX and BD in Mashhad, Iran. Treatment goal of 9 mg/L as N (40 mg/L as nitrate) (influent
nitrate of 26 mg/L as N, 115 mg/L as nitrate). Results indicate BR and RO were best choices. Automated RO pilot plant with a
3
“capacity [of] 3 m /h (RO permeate).” Pre-treatment: acid, anti-scalant, automated filtration (50 um), and cartridge filtration
(1um). 2 stages: in the first stage, 2 parallel membranes, second stage, concentrate from stage one to second membrane before
mixing with stage 1 permeate. Post-treatment: Blending, CO2 removal. New membranes every 5 years. RO was least expensive
3
despite having highest energy demands (0.6 kWh/m of DW), due to low cost of electricity. Lower operator demand than BD. RO
produced better quality water (lower TDS, Ca, Mg, Na, K, Cl, nitrate, sulfate and bicarbonate), but the greatest percentage of
waste.
Milan, Italy: Influent of 11 – 14 mg/L as N (50 – 60 mg/L as nitrate), target of 9 mg/L as N (40 mg/L as nitrate) with waste
3
concentrate < 30 mg/L as N (132 mg/L as nitrate) (for sewer disposal). Series of 13 1-stage RO plants (7 to 58 m /hr permeate),
with blending 77 – 88% water recovery (note the disposal limitation). Pretreatment: anti-scalant (2.0 – 3.5 mg/L). Cleaning only
every year and a half (SDI<1) and requires only 3 techs.
Alternatives to conventional disposal measures of RO waste brine, including reuse for industrial processes, processing (e.g., for salt
production), or use in energy generation (“solar brine pond”).
Analysis of complex source water, membrane fouling and ways of anticipating changes in flux and rejection rates. Relationship
between constituents and how RO treatment is affected by colloids, silica, concentration polarization (higher salt concentration
near membrane surface), back diffusion, and scaling. Typical colloidal constituents: “sulfur, silica, and ferric and aluminum
hydroxides.” Results indicate colloidal fouling may amplify other scaling/fouling factors. “By recognizing possible interferences
between rejected salts and colloids deposited on the membrane surface, the work explored the phenomenon of coupling between
colloidal fouling, concentration polarization, and scaling as main factors limiting the application of RO membranes” (Tarabara
2007).
Investigation of the interaction of upstream residuals on RO treatment (membrane and additive chemicals). Influence of coagulant
residuals on colloidal fouling, and disinfectants on membrane oxidation.
Technical Report 6: Drinking Water Treatment for Nitrate
176
Cevaal et al. (1995)
Water Corporation
(2009)
Black (2003)
Panglisch et al.
(2005)
Dördelmann et al.
(2006 and N.D.)
Dördelmann
(2009)
Elyanow &
Persechino, (2005)
Howe (2004)
Tarabara (2007)
Wang & Tarabara
(2007)
Gabelich et al.
(2004)
Table A.3. Selected research on the use of electrodialysis/electrodialysis reversal for nitrate removal.
3
ED – Pilot study and
Full-scale installation
ED – Pilot study –
Optimization
EDR – Full-scale
installation
EDR – Full-scale
installation
EDR – Full-scale
installations
ED – Multiple
contaminant
removal, role of
organic matter
ED – Pilot study
ED – Pilot study
comparison with
adsorption
Austria: 2-year pilot starting in 1990 with 1 m /h capacity. Influent nitrate concentration 18 – 23 mg/L as N (80 – 100 mg/L as
nitrate), design for 36 mg/L as N (160 mg/L as nitrate). Planning began in 1996 for full-scale installation with seasonal operation
commencing in 1997. Disposal options: sewer or irrigation reuse. “Monovalent selective anion exchange membranes.” 3 stacks in
3
parallel – 3 stages offer capacity from 48 to 144 m /h. Complete automation. Effluent nitrate of 9 mg/L as N (40 mg/L as nitrate)
(capable of product water nitrate of 5.7 mg/L as N, 25 mg/L as nitrate) and 23% hardness reduction. Nitrate selectivity: 66% nitrate
removal with 25% desalination.
Morocco: Pilot study using a nitrate selective membrane for nitrate removal from an influent level of 20 mg/L as N (90 mg/L as
nitrate) to acceptable levels, in water with a TDS concentration of 800 mg/L. Analysis of operating parameters to minimize
precipitation, scaling and associated chemical use. Variation of voltage, flow rate and temperature. Ion removal increased with
increasing temperature.
Delaware: EDR has been successfully employed for the removal of nitrate from potable water in Delaware. The nitrate
concentration in treated potable water was 1 mg/L as N (4.4 mg/L as nitrate), just 7.5% of the 13.5 mg/L as N (60 mg/L as nitrate)
influent nitrate concentration. 3 stage system, 88% demineralization (TDS reduction), 90% water recovery, and pH decrease from
6.2 to 5.4.
Barcelona, Spain: GE EDR plant with 50 MGD capacity (260,000 households), not specifically for nitrate. Limited to no anti-scalant
use. “Compared to a typical RO treatment facility producing 3.8 million gallons of water per day, GE’s EDR technology, operating at
83% efficiency, is designed to eliminate the need for over 28,000 pounds of anti-scalant, reducing operating costs by > $100,000
per year at typical 2008 chemical prices.”
*Previous EDR systems for nitrate removal were installed in Arizona, Delaware, Japan, Italy, Bermuda, and Israel.
Europe: As of ~2005, Ameridia/Eurodia full-scale EDR plants in Italy, France, Switzerland, Netherlands, and Austria. Capacity
ranging from 0.032 – 0.925 MGD and water recovery from 93 – 98%. Information on full-scale installations, pilot studies and costs.
Research investigation using synthetic waters to determine the impact of organic matter in the removal of nitrate, fluoride and
boron. Fouling led to decreased flux, although nitrate removal was the least affected, due to smaller “hydrated ionic radius.”
Removal of boron and fluoride was enhanced by the presence of organic matter, while nitrate removal was not enhanced and
simply decreased over time with the decrease in membrane flux.
Research investigation using synthetic waters to assess nitrate removal under different operating conditions. The impact of
different voltage (from 40 to 50 V) was examined across several ionic species, including nitrate. Alternating anion and cation
exchange membranes were used. Results indicate 94% nitrate removal, with a reduction in the removal rate at 50 V due to back
diffusion and fouling.
Morocco: Nitrate removal from brackish water. Comparison of ED using a monovalent membrane and adsorption on chitosan. ED
successfully removed nitrate. Adsorption can remove nitrate, but not likely feasible. Adsorption can be used to remove nitrate
from ED waste concentrate. Highlights concerns regarding waste concentrate disposal from ED.
Mashhad, Iran: Comparison of IX, RO, BD, and ED. ED pilot study was started in 2007.
Technical Report 6: Drinking Water Treatment for Nitrate
177
Hell et al. (1998)
Midaoui et al.
(2002)
Prato & Parent
(1993)
GE (2010), GE
(N.D.)
Ameridia/Eurodia
Banasiak & Schäfer
(2009)
Nataraj et al.
(2006)
Sahli et al. (2008)
Dördelmann
(2009)
Table A.4. Selected research on the use of biological denitrification for nitrate removal from potable water.
Pilot Testing - Multiple Biological Configurations
The City of Glendale, AZ, has investigated three configurations of biological treatment to address high nitrate levels in groundwater wells (Meyer et al. 2010).
An autotrophic MBfR using was compared with two heterotrophic fixed bed bioreactors each with different media (plastic versus granular activated carbon).
Hydrogen gas and ethanol were used as electron donor for the autotrophic system and the heterotrophic systems, respectively. Post-treatment included
filtration using biologically activated carbon and ozonation. The fixed bed bioreactor with plastic media and the MBfR performed well, with product water
meeting or exceeding potable water standards. Multi-criteria analysis found the MBfR to be most favorable regarding benefits, but the least favorable
regarding costs. Including comparison with IX, the fixed bed bioreactor with plastic media had the lowest life cycle cost. The MBfR costs were greatest.
An investigation of biological treatment options in the City of Thornton, CO, funded by the WaterRF, examined two packed bed bioreactors and a moving bed
™
biofilm reactor (MBBR ) (City of Thornton 2010, Project # 4202) to address nitrate impacted source water. Nitrate levels were successfully decreased by each of
the three pilot systems from an influent concentration of 10 mg/L nitrate as N to an effluent concentration of < 2 mg/L nitrate as N. Operation at high and low
temperatures was tested with examination of seeding for low temperatures. The study highlights the need for nutrient and substrate dose optimization in
biological treatment systems.
Substrates
Numerous alternative substrate options have been explored in the literature including newspapers, vegetable oil, cotton, and formate (Volokita et al. 1996;
Hunter 2001; Killingstad et al. 2002; and Della Rocca et al. 2006.)
Fixed Bed
See Riverside, CA Case Study (Carollo Engineers 2008).
A fixed bed heterotrophic denitrification pilot study was implemented in Mashhad, Iran by Dördelmann et al. (2006) using two parallel fixed beds containing
expanded clay media. Acetic acid and ferrous sulfate served as the electron donor and nutrient supply, respectively. Post treatment consisted of “aeration,
dual media and activated carbon filtration” (Dördelmann et al. 2006). Influent nitrate levels of 26 mg/L as N (115 mg/L as nitrate) were decreased to < 9 mg/L
3
3
as N (40 mg/L as nitrate) with a nitrate reduction rate of ~7 kg NO3/m d (0.43 lb NO3/ft d) (Panglisch et al. 2005 and Dördelmann et al. 2006). Used for flushing
and backwashing, 7% of influent volume was wasted. In practice, a final disinfection step would be required (Dördelmann et al. N.D).
An up-flow, fixed-bed, autotrophic, lab-scale system, using granular sulfur as both substrate and growth surface was explored by Soares (2002). Operated over
3
3
a 5 month period, a maximum denitrification rate of 0.2 kg N/m d (0.012 lb N/ft d) was achieved with a one hour hydraulic retention time and a loading rate of
3
3
0.24 kg N/m d (0.015 lb N/ft d). Sulfur based autotrophic systems would not be appropriate for the treatment of feed waters high in sulfate.
Aslan (2005) examined a lab-scale packed sand bed system, with ethanol as substrate for the simultaneous removal of nitrate and several pesticides. After 3
days for biofilm development, 93 – 98% nitrate removal was achieved requiring at least a 2 hour residence time. Pesticide removal required longer residence
times (up to 12 hours) for efficient removal.
Upadhyaya et al. (2010) investigated the use of a fixed-bed biological reactor with granular activated carbon media for the removal of nitrate and arsenic at the
same time. The media was biologically activated from use in a separate bioreactor for the removal of nitrate and perchlorate. Reactors were thus biologically
active carbon (BAC) reactors. With acetic acid as the substrate, two in series BAC reactors were used to treat synthetic groundwater. Arsenic levels were
reduced from 200 μg/L arsenic in the influent to 20 μg/L in the effluent (still above the arsenic MCL of 10 μg/L) while nitrate levels were decreased from 11
mg/L as N (50 mg/L as nitrate) in the influent to less than 0.045 mg/L as N (0.2 mg/L as nitrate) in the effluent. Used as an electron acceptor by microbes in the
oxidation of substrate, nitrate was reduced to nitrogen gas. Arsenic was removed from solution with the formation of arsenic sulfide (solids) and also with
adsorption and “surface precipitation on iron sulfides (p. 4958).”
Technical Report 6: Drinking Water Treatment for Nitrate
178
Fluidized Bed
See Rialto, CA Case Study (Webster & Togna 2009).
Kurt et al. (1987) investigated an autotrophic fluidized sand bed reactor using hydrogen gas as substrate. With an influent nitrate concentration of 25 mg/L
nitrate-nitrogen, a maximum nitrate reduction rate of 5 mg/L per hour was attained using a mixed culture. The authors propose multiple stage reactors to
address the problem of partial denitrification.
Using a mix of propionic acid and ethanol in a heterotrophic fluidized sand bed reactor, Holló & Czakó (1987) examined denitrification at the lab- and pilot-scale.
Post-treatment consisted of cartridge filtration, gas exchange, sand filtration, carbon filtration and disinfection. “Nitrate removal capacity of the reactor was 50
3
o
– 60 kg NO3 /m /day (3.1 – 3.7 lb NO3 /gal/d), which could be maintained permanently at temperatures as low as 8 – 10 C as well” (Holló & Czakó 1987).
MBR - Diffusive Extraction and Microporous Membranes (See also Pilot Testing above)
Mansell & Schroeder (2002) assessed hydrogenotrophic denitrification at the lab-scale using a membrane bioreactor (MBR) with a 0.02 micron microporous
membrane through which nitrate diffuses to the biological compartment. The membrane prevents mixing of microbes with the water being treated and no
carbon substrate was necessary because hydrogen gas was supplied as the electron donor for autotrophic denitrification. Previous issues regarding the transfer
of hydrogen gas to the water and safety concerns due to explosive nature of hydrogen gas have been addressed with the development of “membrane
dissolution systems” (Mansell & Schroeder 2002). Hydrogen gas was delivered to the biomass with silicone tubing. Results indicated reduction of nitrate levels
−
−
from a maximum of 40 mg/L NO3 -N in the feed water to 3.2 mg/L NO3 -N in the treated water, with 92 – 96% removal. Measured HPC indicated minimal
biomass transfer to the treated water compartment.
Ergas & Rheinheimer (2004) studied denitrification of potable water using a membrane bioreactor (MBR) in which feed water is passed through tubular
acrylonitrile membranes, nitrate diffuses through the membrane and denitrification occurs on the exterior membrane surface. The mean transfer to the biofilm
2
2
was 6.1 g NO3-N/m d (0.6 g NO3-N/ft ). The ultimate methanol (substrate) loading rate of 1.1 g/d resulted in a mean concentration of nitrate in the treated
potable water of 5.2 mg NO3 -N/L. A mathematical model of nitrate mass transfer was developed. A removal efficiency of 99% was achieved with a starting
concentration of 200 mg NO3 -N/L. Use of the MBR allows for denitrification with separation of the water to be treated and biological treatment, thereby
avoiding post treatment removal of biomass and dissolved organics. The effluent would require additional treatment, because 8% (30 mg/L) of the methanol
crossed the membrane; the authors suggest that further development of the biomass could minimize methanol transfer to the effluent stream.
MBR - Gaseous Substrate Delivery – Hollow Fiber Membranes
Chung et al. (2007) explored the use of autotrophic denitrification for the treatment of highly concentrated waste from nitrate removal via anion exchange.
Using a hydrogen-based, hollow fiber membrane biofilm reactor, the impact of brine concentration (up to 15%) on nitrate reduction was found to be significant
due to microbial inhibition. In the reduction of nitrate, use of hydrogen gas rather than an organic substrate offers an inexpensive alternative for potable water
treatment systems. Biomass production is decreased and there is no need to remove substrate residual, as there would be with the use of carbon substrates.
Using nitrate as the primary electron acceptor, hollow fiber MBfRs with hydrogen gas as electron donor can effectively decrease the levels of multiple
contaminants including perchlorate, chromate and arsenate (Nerenberg & Rittman 2004). Low levels of these oxidized species without a primary electron
acceptor can limit biological reduction; however, in the presence of nitrate, reduction can occur. When the concentrations of nitrate and the oxidized species of
interest were 1.1 mg/L as N (5 mg/L as nitrate) and 1 mg/L, respectively, 99% nitrate removal was achieved while removal of perchlorate, chromate and
arsenate reached 36%, >75%, and >50%, respectively.
Technical Report 6: Drinking Water Treatment for Nitrate
179
Bioelectrochemical Denitrification
Ghafari et al. (2008) provide a review of biological denitrification with a focus on bioelectrical reactors (BERs). In a BER, hydrogenotrophic denitrification occurs
as hydrogen gas is produced at the cathode and utilized as the electron donor by denitrifiers, while nitrate is reduced to nitrogen gas. Previous BER research is
discussed including autotrophic and heterotrophic examples across a range of nitrate levels and generally in synthetic waters. With additional research, BERs
may become a feasible alternative for nitrate removal from drinking water.
In situ Denitrification
Permeable reactive barriers (PRBs) can be used to directly treat nitrate contaminated groundwater. Hunter (2001) examined the use of vegetable oil as an
electron donor in biological denitrification. The use of an insoluble substrate minimized biomass blockage, a problem common with the use of soluble
substrates like ethanol, methanol and acetate. The barrier was composed of soybean oil-coated sand and effectively decreased the nitrate levels from a
starting concentration of 20 mg/L nitrate-N to below the MCL for a period of 15 weeks, with a flow rate 1100 L/week. After 15 weeks, insufficient oil remained
for denitrification. High chemical oxygen demand, TSS and turbidity in the effluent of the reactor indicate a longer sand bed was needed; however, the author
suggests that in situ application of this type of biological reactor would decrease these factors naturally. With a withdrawal point far enough from the barrier,
subsequent potable water treatment requirements would be limited to disinfection. The most significant problem encountered in this study was the
exhaustion of substrate. An effective means of substrate addition must be found (injection for example), but this was not explored. The estimated life of the
PRB was 2.5 – 12.5 years depending on several key factors including flow, nitrate concentration and dissolved oxygen concentration.
With hydrogen gas as the substrate in autotrophic denitrification, Haugen et al. (2002) examined hydrogenotrophic denitrification in a lab scale experiment
intended to imitate in situ treatment. Denitrification kinetics, the feasibility and longevity of substrate delivery via tubular membranes and post-treatment
water quality were investigated. Delivery of hydrogen gas through tubular membranes minimized the risks associated with utilization of this
flammable/explosive gas. The reactor was tested over 155 days. An initial influent nitrate concentration of 8.2 mg NO 3 -N/L was doubled to 16.4 mg NO3 -N/L.
2
After adjustment of parameters, complete nitrate removal was achieved using the tubular membrane bioreactor. A denitrification rate of 169 mg N/h/m
(membrane surface area) was attained with a hydrogen gas pressure of 1.44 atm (lower pressures resulted in incomplete reduction. The greatest hydrogen gas
-2
2
transfer across the membrane (flux) was 1.79 x 10 mg H2/m s. The simulated groundwater velocity was 0.3 m/d resulting in 14 minutes of membrane contact
time. Additional considerations for application of this treatment method include: the lower temperature of groundwater, the need for buffer in the current
study, the depth limitation, nutrient requirements, and the difference between aquarium rocks and subsurface porous media. Intermediate denitrification
products and end products (ammonia and nitrogen gas) were not measured in this study; however, the authors suggest the high nitrate to substrate ratio would
result in reduction to nitrogen gas.
Schnobrich et al. (2007) simulated in situ nitrate removal via hydrogenotrophic Denitrification. With hydrogen gas delivery through a membrane module
consisting of a fiberglass membrane wound in a spiral fashion and attached to polyethylene membranes. The study examined the influence of pH, nutrient
requirements and the feasibility of appropriate levels of hydrogen gas delivery. To simulate in situ conditions, the porous media was extracted from an aquifer
o
and the system was operated at 10 C. Two up-flow columns were operated in series, only the first of which included a membrane fed with hydrogen gas.
Including that required for the reduction of dissolved oxygen, the total concentration of hydrogen gas required for complete denitrification was 11.2 mg H 2/L.
Overall, this study demonstrated effective substrate delivery and nitrate removal under conditions more similar to what would be expected naturally.
Technical Report 6: Drinking Water Treatment for Nitrate
180
Table A.5. Selected research on the use of chemical denitrification (CD) for nitrate removal.
CD using ZVI
CD – ZVI
CD – ZVI
CD – ZVI
CD – ZVI
CD – ZVI
CD - SMI
CD – Catalytic
Denitrification
Reduction of nitrate to ammonia using ZVI powder was highly pH dependent with optimal kinetics below a pH of
Huang et al.
2
4. The minimum ratio of iron to nitrate was 120 m /mol NO3 for complete reduction within 1 hour. 50 mg NO3 /L,
(1998)
100% removal.
Found that the end product of denitrification (nitrogen gas versus ammonium) could be controlled by the iron to
Xiong et al.
nitrate ratio and the use of catalysts.
(2009)
In the corrosion of ZVI, the formation of “green rusts” and “suspended green particles” is associated with
Choe et al.
stabilization of pH and steady decrease in nitrate.
(2004)
Examined the nitrate reduction rates of three types of iron. Findings indicate that rate increases with decreasing
Alowitz &
pH.
Scherer (2002)
Nitrate reduction by ZVI can be optimized through pretreatment of iron particles. High temperature exposure to
Liou et al.
hydrogen gas and deposition of copper were explored separately as options for pretreatment of the iron surface.
(2005)
Examined chloride as a potential competitor. Results indicate a minimal impact on nitrate removal; however,
Moore & Young
other competing ions could be important regarding both competition for adsorption sites and reduction.
(2005)
“SMI-III® is a patented, iron-based granular media that has been commercially developed for the removal of
nitrate, co-contaminants including uranium, vanadium and chromium, and other compounds from water. It is
DSWA and City
foreseen that the greatest benefit of this technology is that it does not produce a costly brine stream as do the
of Ripon (2010)
currently accepted nitrate removal technologies of ion exchange and reverse osmosis.”
Reddy & Lin 2000; Pintar et al. 2001; Gavagnin et al. 2002; Lemaignen et al. 2002; Pirkanniemi & Sillanpaa 2002; Chen et al. 2003;
Palomares et al. 2003; Pintar 2003; Constantinou et al. 2007; and Sun et al. 2010.
Technical Report 6: Drinking Water Treatment for Nitrate
181
Table A.6. Advantages and disadvantages of the five major treatment options for nitrate removal.
Advantages
Ion Exchange






Reverse
Osmosis
Electrodialysis/
Electrodialysis
Reversal






High quality product water,
Multiple contaminant removal,
Desalination (TDS removal),
Feasible automation,
Small footprint, and
Application for small and POU
applications.



Limited to no chemical usage,
Long lasting membranes,
Selective removal of target
species,
Flexibility in removal rate through
voltage control,
Better water recovery (lower
waster volume),
Feasible automation, and
Multiple contaminant removal.






Biological
Denitrification
Years of industry experience,
Multiple contaminant removal,
Selective nitrate removal,
Financial feasibility,
Use in small and large systems,
and
The ability to automate.





High water recovery,
No brine or concentrate waste
stream (nitrate reduction rather
than removal to waste stream),
Low sludge waste,
Less expensive operation,
Limited chemical input,
Increased sustainability, and
Multiple contaminant removal.






























Chemical
Denitrification



Conversion of nitrate to other
nitrogen species (no brine or
concentrate waste stream),
The potential for more sustainable
treatment,
High water recovery (higher than
®
RO according to Cleanit -LC), and
Multiple contaminant removal.
Technical Report 6: Drinking Water Treatment for Nitrate




Disadvantages
The disposal of waste brine,
The potential for nitrate dumping specifically for
non-selective resin use for high sulfate waters,
The need to address resin susceptibility to
hardness, iron, manganese, suspended solids,
organic matter, and chlorine, and
The possible role of resin residuals in DBP
formation.
The disposal of waste concentrate,
Typically high capital and O&M costs,
The need to address membrane susceptibility to
hardness, iron, manganese, suspended solids,
silica, organic matter, and chlorine,
High energy demands, and
The lack of control over target constituents
(complete demineralization).
The disposal of waste concentrate,
The need to address membrane susceptibility to
hardness, iron, manganese, and suspended solids,
High maintenance demands,
Costs (comparable to RO systems),
The need to vent gaseous byproducts,
The potential for precipitation with high recovery,
High system complexity, and
Dependence on conductivity.
The need for substrate and nutrient addition,
High monitoring needs,
Significant post-treatment requirements,
High capital costs,
Sensitivity to environmental conditions
(sometimes),
Large system footprint (sometimes),
High system complexity (sometimes, can be
comparable to RO),
Lack of full-scale systems in the U.S.,
The possibility of partial denitrification,
Permitting and piloting requirements, and
Slower initial start-up, which could cause
challenges for wells with intermittent run time.
The potential reduction of nitrate beyond nitrogen
gas to ammonia,
The possibility of partial denitrification,
The possible dependence of performance on pH
and temperature,
The possible need for iron removal, and
The lack of full-scale chemical denitrification
systems resulting in:
o Unknown reliability,
o Unknown costs, and
o Unknown operational complications.
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