United States
Environmental Protection
Agency
osmosis
2017
Potable Reuse Compendium
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oEPA
United States
Environmental Protection
Agency
Office of Ground Water and Drinking Water
Office of Water
Washington, D.C. 20460
EPA/810/R-17/002
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75 State Street
Suite 701
Boston, MA 02109

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2017 Potable Reuse Compendium
Preface
Appropriate and necessary treatment and reuse of wastewater to augment existing water
resources is a rapidly expanding approach for both non-potable and potable applications. EPA
recognizes that potable reuse of water can play a critical role in helping states, tribes, and
communities meet their future drinking water needs with a diversified portfolio of water sources.
Beginning with the first pioneers in water reuse, Los Angeles County Sanitation District (1962),
Orange County Sanitation District (1976), and the Upper Occoquan Service Authority (1978), the
practice has gained substantial momentum because of drought and the need to assure
groundwater resource sustainability and a secure water supply. Long-term water scarcity is
expected to increase over time in many parts of the country as a result of drought, growing water
demand, and other stressors.
Across the U.S., there has been a notable increase in the deployment of technologies to
augment existing water supplies through reuse of wastewater that has been treated and
cleaned to be safe for the intended use. Indirect reuse usually involves passage of water through
an environmental buffer (e.g., groundwater aquifer, lake, river) before the water is again treated for
reuse. Direct reuse refers to those situations where treatment is followed by storage and use,
but without the environmental buffer. Many drinking water systems rely on water treatment
technologies to support indirect reuse of water (e.g., indirect potable reuse) and some drinking
water systems now directly reuse wastewater after treatment (e.g., direct potable reuse).
In 2012, EPA published the 2012 Guidelines for Water Reuse to serve as a reference on water
reuse practices. The document provided information related to indirect potable reuse (IPR), but
only briefly described direct potable reuse (DPR). Because of increased interest in pursuing
potable water reuse, EPA is issuing the 2017 Potable Reuse Compendium to outline key science,
technical, and policy considerations regarding this practice. This 2017 Compendium supplements
the 2012 Guidelines for Water Reuse to inform current practices and approaches in potable reuse,
including those related to direct potable water reuse. EPA recognizes the recent water reuse
publications from our stakeholders at the World Health Organization (WHO), the National
Research Council of the National Academies of Science, the Water Environment and Reuse
Foundation (WE&RF), and the Water Environment Federation (WEF). The 2017 Compendium is
a compilation of technical information on potable reuse practices to provide planners and
decision-makers with a summary of the current state of the practice. Specific knowledge and
experience are drawn from case studies on existing reuse approaches.
EPA supports water reuse as part of an integrated water resources management approach
developed at the state and local level to meet the water needs of multiple sectors including
agriculture, industry, drinking water, and ecosystem protection. An integrated approach
commonly involves a combination of water management strategies (e.g., water supply
development, water storage, water use efficiency, and water reuse) and engages multiple
stakeholders and needs, including the needs of the environment.
Although EPA encourages an integrated approach to water resources management, it does not
require or restrict practices such as water reuse. EPA acknowledges the primacy of states in the

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2017 Potable Reuse Compendium
Preface
allocation and development of water resources. EPA, State, and local governments implement
programs under the Clean Water Act and the Safe Drinking Water Act to protect the quality of
source waters to ensure that source water is treated so that water provided to the tap is safe for
people to drink (e.g., contaminant specific drinking water standards). The SDWA and the
CWA provide a foundation from which states can further develop and support potable water
reuse as they deem appropriate.
EPA will continue to engage a broad spectrum of partners and stakeholders for input on
where the Agency can provide meaningful support to states, tribes, and communities as they
implement potable water reuse projects. EPA will also work with stakeholders, the scientific
community, and the States to monitor and evaluate performance of water treatment
technologies to ensure that potable reuse projects are implemented in a manner that protects the
health of communities. This document is a collaborative effort between EPA, CDM Smith, and
other key stakeholders. EPA acknowledges the importance of potable water reuse and looks
forward to working with our stakeholders as the practice continues to be developed and
deployed as an important approach to ensure a clean, safe, and sustainable water supply
for the nation.
Peter Grevatt, PhD
Director
Office of Ground Water and Drinking Water
Office of Water
U.S. Environmental Protection Agency

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2017 Potable Reuse Compendium
Notice
This document was produced by the Environmental Protection Agency and CDM Smith Inc. (CDM Smith)
under a Cooperative Research and Development Agreement (CRADA). It supplements the 2012 Guidelines
for Water Reuse published by EPA in collaboration with the United States Agency for International
Development (USAID) and CDM Smith. This document underwent EPA review and received approval for
publication. Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.
The statutes and regulations described in this document may contain legally binding requirements. Neither
the summaries of those laws provided here nor the approaches suggested in this document substitute for
those statutes or regulations, nor is this document any kind of regulation. This document is solely
informational and does not impose legally binding requirements on EPA; other U.S. federal agencies,
states, local, or tribal governments; or members of the public. Any EPA decisions regarding a particular
water reuse project will be made based on the applicable statutes and regulations. EPA will continue to
review and update this document and the 2012 Guidelines for Water Reuse as necessary and appropriate.
iii

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2017 Potable Reuse Compendium
Development of this Document
Development of this Document
EPA and CDM Smith worked collaboratively under a Cooperative Research and Development Agreement
(CRADA) (EPA-CDM CRADA 844-15) to produce the 2017 Potable Reuse Compendium that assesses
the current status of potable reuse utilizing the established technical and policy knowledge base.
EPA's Office of Ground Water and Drinking Water co-developed and reviewed the document and
invited other EPA offices and external reviewers to provide additional comments to develop this
document in a way that it is technically robust, and broadly acceptable to EPA and members of the
regulatory community.
iv

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2017 Potable Reuse Compendium
Acknowledgements
Acknowledgments
We would like to express gratitude to the external technical review committee who reviewed this document.
The technical review committee included:
Jim Taft
Executive Director
Association of State Drinking Water
Administrators
Cindy Forbes
Deputy Director, Division of Drinking Water
State Water Resources Control Board of CA
Jing-Tying Chao
Division of Drinking Water
State Water Resources Control Board of CA
G. Tracy Mehan III
Executive Director of Government Affairs
American Water Works Association
Steve Via
Director of Federal Relations
American Water Works Association
The 2017 Potable Reuse Compendium was developed collaboratively through a CRADA between CDM
Smith and EPA. The CDM Smith project management team was led by Project Director Greg Wetterau,
and included Jennifer Osgood, Jill Vandegrift, Allegra da Silva, and Katherine Bell. Special thanks go to our
colleagues who took their time to share professional experiences and technical knowledge in potable reuse
to make this document relevant to the current state of practice of potable reuse. Please note that the listing
of these contributors does not necessarily indicate endorsement of this document or represent all of their
ideas or opinions on the subject.
Greg Wetterau
R. Bruce Chalmers
Doug Brown
CDM Smith
CDM Smith
CDM Smith
Rancho Cucamonga, CA
Irvine, CA
Denver, CO
Jillian Vandegrift
James Lavelle
Christopher Schulz
CDM Smith
CDM Smith
CDM Smith
Denver, CO
Phoenix, AZ
Denver, CO
Allegra da Silva
Jennifer Hooper
Susan Crawford
previously with CDM Smith,
CDM Smith
CDM Smith
now with Stantec
Bellevue, WA
Dallas, TX
Denver, CO
Phil Singer
Michael Stevens
Katherine Bell
CDM Smith
CDM Smith
previously with CDM Smith,
Raleigh, NC
Bellevue, WA
now with Stantec
Nashville, TN
Melissa Meeker
Executive Director
Water Environment and Reuse Foundation
Julie Minton
Program Director for Water Reuse and
Desalination
Water Environment and Reuse Foundation
Ron Falco
Safe Drinking Water Program Manager
Colorado Department of Public Health and
Environment
Joel Klumpp
Manager, Plans and Technical Review Section
Texas Commission on Environmental Quality
v

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2017 Potable Reuse Compendium
Acknowledgements
Jane Madden
CDM Smith
Boston, MA
Katherine Dowdell
CDM Smith
Walnut Creek, CA
Darren Boykin
CDM Smith
Atlanta, GA
Marcia Rinker
CDM Smith
Anna Adams
CDM Smith
Boston, MA
Alma Jansma
CDM Smith
Rancho Cucamonga, CA
Robert Angelotti
Upper Occoquan Sewage
Authority
Centreville, VA
John Albert
WRF
Denver, CO
Thomas J. Grizzardt
Virginia Tech
Mehul Patel
Orange County Water District
Fountain Valley, CA
Paul Fu
Water Replenishment District
of So. California
Lakewood, CA
Chris Stacklin
Orange County Sanitation
District
Orange County, CA
Denise Funk
Gwinnett County Department
of Water Resources
Gwinnett County, GA
Robert Harris
Gwinnett County Department
of Water Resources
Gwinnet County, GA
Mayor David Venable
Village of Cloudcroft, NM
Eddie Livingston
Livingston Associates
Alamogordo, NM
Daniel Nix
City of Wichita Falls
Wichita Falls, TX
Russell Schreiber
City of Wichita Falls
Wichita Falls, TX
Kara Nelson
University of California
Berkeley
Berkeley, CA
Shane Snyder
University of Arizona
Tucson, AZ
Channah Rock
University of Arizona
Maricopa, AZ
Troy Walker
Hazen
Phoenix, AZ
Ben Stanford
American Water
Raleigh, NC
Brian Bernados
California Division of Drinking
Water
San Diego, CA
Jeff Mosher
Water Environment and
Reuse Foundation
Alexandria, VA
VI

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2017 Potable Reuse Compendium	Acknowledgements
The following individuals also developed chapters and text, provided direction, advice, suggestions, or
review comments on behalf of EPA:
Michelle Schutz
Kenneth Rotert
Pete Ford
Project Manager
OGWDW
OGC
OGWDW
Washington, D.C.
Washington, D.C.
Washington, D.C.
Marisa Tricas
Carrie Wehling
Ryan Albert
OGWDW
OGC
OGWDW
Washington, D.C.
Washington, D.C.
Washington, D.C.
Hannah Holsinger
Robert Bastian
OWM
Christopher Impellitteri
ORD
Cincinnati, OH
OGWDW
Washington, D.C.
Washington, D.C.
Jan Pickrel
Lauren Kasparek
OWM
Thomas Speth
ORISE Participant
Washington, D.C.
ORD
OGWDW
Washington, D.C.
Ashley Harper
OST
Cincinnati, OH
Bob Brobst, PE,
Rajiv Khera
Washington, D.C.
EPA Region 8
OGWDW
Washington, D.C.
Jeff Lape
OST
Denver, CO
Jake Crosby
Mike Muse
Washington, D.C.
EPA Region 8
OGWDW
Washington, D.C.
Sharon Nappier
OST
Denver, CO
Roger Gorke
Phil Oshida
Washington, D.C.
OW/EPA Region 9
OGWDW
Washington, D.C.
Robert Goo
OWOW
Los Angeles, CA
Bruce Macler
Stig Regli
Washington, D.C.
EPA Region 9
OGWDW
Washington, D.C.
Leslie Darman
OGC
Washington, D.C.
San Francisco, CA
vii

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2017 Potable Reuse Compendium
Table of Contents
Table of Contents
Preface	i
Notice	iii
Development of this Document	iv
Acknowledgments	v
Table of Contents	viii
List of Figures	xii
List of Tables	xiii
Frequently Used Abbreviations and Acronyms	xiv
CHAPTER 1 Introduction	1-1
1.1	Terminology	1-1
1.2	Target Audience	1-1
1.3	Objectives of this Document	1-1
1.4	What is Potable Reuse?	1-4
1.5	Comparing Potable Reuse with Other Alternative Water Supplies and Approaches	1-5
1.5.1	Conservation	1-5
1.5.2	Non-Potable Reuse	1-5
1.5.3	Imported Water	1-5
1.5.4	Desalination	1-5
1.6	Expansion of Potable Reuse	1-6
1.7	Document Organization and Additional Reports	1 -6
CHAPTER 2 Potable Reuse in the United States and Abroad	2-1
2.1	Potable Reuse in the United States	2-1
2.1.1	Current State of Potable Reuse in the United States	2-1
2.1.2	Water Supply Enhancement	2-5
2.1.3	De facto Reuse in the United States	2-6
2.2	Potable Reuse Worldwide	2-6
CHAPTER 3 Safe Drinking Water Act and Clean Water Act: Opportunities for Water
Reuse	3-1
3.1	Existing Regulatory Opportunities for Potable Reuse	3-1
3.1.1	Clean Water Act (CWA)	3-2
3.1.2	Safe Drinking Water Act (SDWA)	3-5
3.1.3	Regulatory Considerations for Planned Potable Reuse	3-12
3.2	Local Regulatory Approaches	3-13
CHAPTER 4 Constituents in Potable Reuse Water Sources	4-1
4.1 Constituents in Potable Reuse Water Sources	4-1
4.1.1	Pathogenic Microorganisms in Potable Reuse Water Sources	4-1
4.1.2	Chemical Constituents in Potable Reuse Water Sources	4-2
4.1.3	Inorganic Chemicals in Potable Reuse Water Sources	4-3
4.1.4	Organic Chemicals in Potable Reuse Water Sources	4-3

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4.1.5 Trace Chemical Constituents in Potable Reuse Water Sources	4-3
4.2	Constituents after Wastewater Treatment	4-3
4.2.1	Microbials after Wastewater Treatment	4-3
4.2.2	Chemical Constituents after Wastewater Treatment	4-4
4.3	Constituents During Water Treatment	4-4
4.4	Constituents After Drinking Water Treatment	4-5
CHAPTER 5 Risk Analysis	5-1
5.1	Risk Assessment	5-1
5.1.1	Quantitative Risk Assessment	5-2
5.1.2	Alternative Risk Assessment Methods	5-3
5.2	Risk Management	5-4
5.2.1	Risk Reduction Concepts and Management	5-5
5.2.2	Risk Analysis Framework	5-9
5.3	Summary	5-9
CHAPTER 6 Treatment Technologies for Potable Reuse	6-1
6.1	Overview: Five Overall Treatment Objectives for Potable Reuse	6-1
6.2	Removal of Suspended Solids	6-2
6.2.1	Media Filtration	6-3
6.2.2	Microfiltration and Ultrafiltration	6-3
6.3	Reducing the Concentration of Dissolved Chemicals	6-5
6.3.1	Reverse Osmosis	6-5
6.3.2	Nanofiltration (NF)	6-7
6.3.3	Electrodialysis/Electrodialysis Reversal (ED/EDR)	6-7
6.3.4	Ion Exchange	6-8
6.3.5	Activated Carbon	6-8
6.3.6	Biologically Active Filtration (BAF)	6-9
6.4	Disinfection and Removal of Trace Organic Compounds	6-9
6.4.1	UV	6-9
6.4.2	Chlorine/Chloramines	6-10
6.4.3	Peracetic Acid (PAA)	6-11
6.4.4	Pasteurization	6-11
6.4.5	Chlorine Dioxide	6-12
6.4.6	Ozone	6-12
6.4.7	Advanced Oxidation Processes (AOPs)	6-13
6.5	Aesthetics	6-14
6.5.1	Taste and Odor Control	6-15
6.5.2	Color	6-15
6.6	Stabilization	6-15
6.6.1	Decarbonation	6-16
6.6.2	Sodium Hydroxide	6-16
6.6.3	Lime Stabilization	6-16
6.6.4	Calcium Chloride	6-16
6.6.5	Blending	6-16
6.7	SummaryTable ofTreatment Technologies	6-17
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6.8 Residuals Management	6-18
CHAPTER 7 Alternative Treatment Trains for Potable Reuse	7-1
7.1	Overview	7-1
7.1.1	Multiple Barrier Approach	7-2
7.1.2	Source Control	7-2
7.1.3	Optimizing Upstream Wastewater Treatment	7-3
7.2	Types of AWT Unit Processes Used in Potable Reuse Treatment Trains	7-3
7.2.1	WWTP to Surface Water Discharge	7-3
7.2.2	WWTP to Soil Aquifer Treatment (SAT)	7-3
7.2.3	Full Advanced Treatment and Related Models	7-5
7.2.4	Ozone-BAF or the Alternative Treatment Train	7-7
CHAPTER 8 Source Control	8-1
8.1	Introduction	8-1
8.2	Elements for Potable Reuse - Source Control Program	8-1
8.2.1	California's IPR Source Control Program Requirements	8-3
8.2.2	DPR Source Control Program Elements	8-3
8.3	National Pretreatment Program	8-3
8.4	Pollution Prevention	8-4
8.5	POTW Chemical Impacts on Reuse Facilities	8-4
CHAPTER 9 Environmental and Engineered Buffers	9-1
9.1	Environmental Buffers	9-1
9.1.1	Aquifer Recharge	9-1
9.1.2	Surface Water Storage	9-2
9.1.3	Wetlands	9-2
9.1.4	Fate and Transport of Pathogens in Subsurface Environmental Buffers	9-3
9.1.5	Fate and Transport of Trace Chemical Constituents in Environmental Buffers	9-3
9.2	Engineered Storage	9-4
9.3	Response Time in Buffers	9-5
9.4	Replacing the Value of the Environmental Buffer	9-5
CHAPTER 10 Training, Operating, and Monitoring	10-1
10.1	Operator Training and Licensure	10-1
10.2	Hazard Analysis and Critical Control Points (HACCP)	10-2
10.3	Start-up, Commissioning, and Initial Operation	10-3
10.4	Ongoing Operation and Maintenance	10-4
10.5	Optimization and Improvement	10-5
10.6	Process Control and Monitoring	10-5
10.7	Selecting Monitoring Locations	10-6
10.7.1 Distinguishing Critical Control Points (CCPs) from Critical Operating Points (COPs)..10-6
10.8	Phases of Monitoring: Validation and Compliance	10-7
10.8.1	Validation Monitoring	10-7
10.8.2	Compliance Monitoring	10-7
10.9	Calibration	10-7
10.10	Reporting	10-7
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Table of Contents
10.11 Indicators and Surrogates	10-8
10.11.1	Microbial Treatment Process Performance Indicators	10-9
10.11.2	Microbial Treatment Process Performance Surrogates	10-10
10.11.3	Chemical Treatment Process Performance Indicators	10-11
10.11.4	Chemical Treatment Process Performance Monitoring Surrogates	10-11
CHAPTER 11 Cost of Potable Reuse	11-1
11.1	Introduction	11-1
11.2	Cost Estimates	11-1
11.2.1	Capital Costs	11-1
11.2.2	Operations and Maintenance Costs (O&M Costs)	11-2
11.2.3	Cost of Alternative Treatment Trains	11-3
11.2.4	Cost of Water	11-3
CHAPTER 12 Epidemiological and Related Studies	12-1
12.1	Epidemiology of Water Reuse	12-1
12.2	Future Research	12-6
CHAPTER 13 Public Acceptance	13-1
13.1	Current State of Public Acceptance	13-1
13.1.1	Public Awareness and Opinion	13-1
13.1.2	Shifting Opinions with Public Outreach and Changing Conditions	13-1
13.2	Important Factors in Stakeholder Engagement for Potable Reuse	13-2
CHAPTER 14 Research	14-1
14.1 Current Highlighted Research	14-1
14.1.1	EPA	14-1
14.1.2	Water Environment & Reuse Foundation (WE&RF)	14-1
14.1.3	Water Research Foundation (WRF)	14-2
CHAPTER 15 References	15-1
Appendix A: Case Study Examples of IPR and DPR in the United States
A.1 Los Alamitos Barrier Water Replenishment District of So. CA/Leo J. Vander Lans Advanced
Water Treatment Facility (LVLAWTF) - Indirect Potable Reuse	A.1-1
A.2 Orange County Groundwater Replenishment System (GWRS) Advanced Water Treatment
Facility	A.2-1
A.3 Gwinnett F. Wayne Hill Water Resources Center, Chattahoochee River and Lake Lanier
Discharge - Indirect Potable Reuse	A.3-1
A.4 Village of Cloudcroft PURe Water Project - Direct Potable Reuse	A.4-1
A.5 Colorado River Municipal Water District Raw Water Production Facility Big Spring Plant - Direct
Potable Reuse	A.5-1
A.6 Wichita Falls River Road WWTP and Cypress WTP Permanent IPR and Emergency DPR
Project	A.6-1
A.7 Potable Water Reuse in the Occoquan Watershed	A.7-1
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2017 Potable Reuse Compendium
List of Figures
List of Figures
Figure 1-1. Planned IPR scenarios and examples (adapted from EPA, 2012a)	1-3
Figure 1-2. Planned DPR scenarios and examples (adapted from EPA, 2012a)	1-3
Figure 2-1. Planned and constructed IPR and DPR projects in the United States as of 2017	2-5
Figure 2-2. Overview of selected planned and constructed IPR and DPR projects worldwide (not
intended to be a complete survey)	2-7
Figure 5-1. Risk mitigation concepts in potable reuse schemes (adapted from WRRF, 2014a)	5-6
Figure 5-2. States with redundancy regulations or requirements (WERF, 2003)	5-8
Figure 6-1. Size ranges for various filtration processes (source: GE Osmonics, 2000)	6-2
Figure 6-2. Submerged MF membranes at OCGWR	6-5
Figure 6-3. RO system at OCGWR	6-5
Figure 6-4. Typical breakpoint chlorination curve	6-11
Figure 7-1. Overview of potable reuse treatment trains in existence as of 2015 (not intended to be a
complete survey)	7-2
Figure 7-2. Oxelia oxidation-enhanced biologically active filtration system (courtesy of Xylem Inc.)	7-8
Figure 8-1. Fundamental goals of a DPR source control program	8-1
Figure 8-2. Critical components of a source control program for potable reuse	8-2
Figure 9-1. Environmental buffers in potable reuse treatment schemes	9-1
Figure 9-2. Engineered storage buffers in potable reuse treatment schemes	9-5
Figure 11-1. Typical O&M cost breakdown of a potable reuse facility using a membrane-based
treatment train	11-3
Figure 11-2. Full advanced treatment train © Copyright 2014 WateReuse Research Foundation
(project 10-01), used with permission	11-4
Figure 11-3. Ozone-BAF treatment train © Copyright 2014 WateReuse Research Foundation
(project 10-01), used with permission	11-4
Figure 14-1. Barriers to potable reuse research (WRRF figure used with permission)	14-2
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2017 Potable Reuse Compendium
List of Tables
List of Tables
Table 1-1. Document scope	1-2
Table 1-2. Local factors that, if present, may make potable reuse desirable as part of an overall
water supply portfolio	1-2
Table 1-3. Comparison of IPR and DPR practices	1-4
Table 1-4. Document organization	1-6
Table 1-5. Reports on potable reuse (not intended to be a complete survey)	1-8
Table 2-1. Overview of selected planned IPR and DPR projects in the United States (not intended to
be a complete survey)	2-2
Table 2-2. Overview of selected planned IPR and DPR projects outside of the United States (not
intended to be a complete survey)	2-8
Table 3-1. Number of U.S. states or territories addressing potable water reuse as of 2017 (Updated
from EPA, 2012a)	3-13
Table 3-2. Select U.S. states addressing potable reuse as of 2017	3-13
Table 4-1. Median infectious dose of waterborne pathogens (Feachem et al., 1983; Messner et al.,
2014, 2016; Teunis et al., 2008)	4-1
Table 4-2. Chemical substances potentially present in wastewaters (not intended to be a complete
list)	4-2
Table 4-3. Pathogen Densities in Raw Wastewater and Log10 Reductions Across Unit Treatment
Processes (adapted from Soller et al., 2018)	4-5
Table 6-1. Overall treatment objectives and corresponding unit processes	6-1
Table 6-2. Aesthetic compounds potentially present in untreated municipal wastewaters	6-14
Table 6-3. Treatment technologies and associated treatment capabilities (adapted from CORPUD,
2014)	6-17
Table 7-1. IPR application approaches (adapted from EPA, 2012a)	7-4
Table 7-2. Comparison of pathogen and contaminant reduction in California and Western Australia
IPR approaches	7-6
Table 7-3. Reclamation facilities using the ozone-BAF process	7-9
Table 8-1. Specific content of potable reuse source control program elements (Adapted from FCM
and NRC, 2003)	8-2
Table 10-1. Microbial monitoring terms (adapted from WHO, 2001; WRF, 2008; NRC, 2012a; EPA,
2012a)	10-8
Table 10-2. Chemical monitoring terms (adapted from WRF, 2008; NRC, 2012a)	10-8
Table 10-3. Potential indicator compounds with differing physiochemical properties to demonstrate ..10-12
Table 11-1. Cost of alternative treatment trains for a 20 MGD facility (adapted from WRRF, 2014d).... 11-5
Table 11-2. Costs of RO concentrate management options for potable reuse treatment (from Table
10.3 in NWRI, 2015)1	11-6
Table 12-1. Epidemiological and related studies on health effects pertaining to reclaimed water
consumption (Rock et al., 2016. Reproduced with permission. ©Water Research
Foundation)	12-1
Table 14-1. DPR and related research projects	14-3
Table 14-2. WRF biofiltration related research projects (WRF, 2017)	14-14

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2017 Potable Reuse Compendium
Frequently Used Abbreviations and Acronyms
Frequently Used Abbreviations
and Acronyms
AGB
Alamitos Gap Barrier
AOP
advanced oxidation processes
ASR
aquifer storage and recovery
AWTF
advanced wastewater treatment facility
AWTP
advanced water treatment plant
AWWA
American Water Works Association
BAC
biological activated carbon
BAF
biologically active filtration
BGD
billion gallons per day
BOD
biochemical oxygen demand
CCL
Contaminant Candidate List
CCP
Composite Correction Program
CIP
clean-in-place
COD
chemcial oxygen demand
COP
critical operating points
CPE
Comprehensive Performance Evaluation
CRADA
Cooperative Research and Development Agreement
CRMWD
Colorado River Municipal Water District
CTA
Comprehensive Technical Assistance
CWA
Clean Water Act
CWCB
Colorado Water Conservation Board
CWS
community water system
DAF
dissolved air flotation
DBP
disinfection by-product
DBPR
Disinfection Byproducts Rule
DDW
(California) Division of Drinking Water
DOC
dissolved organic carbon
DPR
direct potable reuse
EC
electrical conductivity
EDC
endocrine disrupting compound
EDR
electrodialysis reversal
EEWTP
Estuary Experimental Water Treatment Plant
EPA
Environmental Protection Agency
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2017 Potable Reuse Compendium
Frequently Used Abbreviations and Acronyms
ESB
environmental storage buffer
FRT
failure response times
FWHWRC
F. Wayne Hill Water Reclamation Center
GAC
granular activated carbon
GWR
Ground Water Rule
GWRS
Groundwater Replenishment System
GWUDI
groundwater under the direct influence of surface water
HACCP
Hazard Analysis and Critical Control Points
IAP
Independent Advisory Panel
IESWTR
Interim Enhanced Surface Water Treatment Rule
IPR
indirect potable reuse
ISS
International Space Station
LBWRP
Long Beach Water Reclamation Plant
LPHO
low-pressure high output
LRC
log removal credit
LRV
log reduction value
LSI
Langelier Saturation Index
LVLAWTF
Leo J. Vander Lans Advanced Water Treatment Facility
MAR
managed aquifer recharge
MBR
membrane bioreactor
MCL
maximum contaminant level
MCLG
maximum contaminant level goal
MF
microfiltration
MGD
million gallons per day
NDMA
N-nitrosodimethylamine
NMED
New Mexico Environment Department
NOM
natural organic matter
NPDES
National Pollutant Discharge Elimination System
NPDWR
National Primary Drinking Water Regulation
NTNCWS
nontransient, noncommunity public water system
NTU
nephelometric turbidity unit
NWRI
National Water Research Institute
OCSD
Orange County Sanitation District
OCWD
Orange County Water District
OWMP
Occoquan Watershed Monitoring Program
PAA
peracetic acid
PAC
powdered activated carbon
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2017 Potable Reuse Compendium
Frequently Used Abbreviations and Acronyms
PCR
polymerase chain reaction
PhACs
pharmaceutical^ active compounds
POTW
publicly owned treatment works
PPCP
pharmaceuticals and personal care products
QMRA
quantitative microbial risk assessment
QRRA
quantitative relative risk assessment
RO
reverse osmosis
RTCR
Revised Total Coliform Rule
RWPF
raw water production facility
RWQC
Recreational Water Quality Criteria
SAT
soil aquifer treatment
SCADA
Supervisory Control and Data Acquisition
SCMA
South-Central Membrane Association
SDWA
Safe Drinking Water Act
SOP
standard operating procedure
SRT
solids retention time
SWMOA
Southwest Membrane Operator Association
SWTR
Surface Water Treatment Rule
TBL
triple bottom line
TCEQ
Texas Commission on Environmental Quality
TCR
Total Coliform Rule
TDS
total dissolved solids
THM
trihalomethanes
TMDL
total maximum daily load
TOC
total organic carbon
TrOC
trace organic chemicals
TSS
total suspended solids
TTHM
total trihalomethanes
TWDB
Texas Water Development Board
UCMR
Unregulated Contaminant Monitoring Rule
UF
ultrafiltration
UIC
Underground Injection Control
UOSA
Upper Occoquan Service Authority
USDW
underground source of drinking water
UV
ultraviolet radiation
UVT
UV transmittance
VDEQ
Virginia Department of Environmental Quality
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2017 Potable Reuse Compendium
Frequently Used Abbreviations and Acronyms
VDH
Virginia Department of Health
WE&RF
Water Environment & Reuse Foundation
WEF
Water Environment Federation
WERF
Water Environment Research Foundation
WHO
World Health Organization
WRC
Water Resources Center
WRD
Water Replenishment District
WRF
Water Research Foundation
WRRF
WateReuse Research Foundation
WRS
water recycling system
WTP
water treatment plant
WWTP
wastewater treatment plant
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Chapter 1 | Introduction
CHAPTER 1
Introduction
In 2012, the U.S. Environmental Protection Agency (EPA) published Guidelines for Water Reuse (2012
Guidelines) to facilitate further development of water reuse by serving as an authoritative reference on
water reuse practices. The 2012 Guidelines document met a critical need: it informed and supplemented
state regulations and guidelines by providing technical information and outlining key implementation
considerations.
1.1	Terminology
As described in the 2012 Guidelines, the terminology associated with treating and reusing municipal
wastewater varies both within the United States and globally. For instance, some states and countries use
the term "reclaimed water" and "recycled water" interchangeably. Similarly, the terms "water recycling" and
"water reuse" are often used synonymously. This document uses the terms reclaimed water and water
reuse. Definitions of terms used in this document, except their use in case studies, are provided below.
Planned potable reuse: The publicly acknowledged, intentional use of reclaimed wastewater for drinking
water supply. Commonly referred to simply as potable reuse.
De facto reuse; A situation where reuse of treated wastewater is practiced but is not officially recognized
(e.g., a drinking water supply intake located downstream from a wastewater treatment plant [WWTP]
discharge point).
Direct potable reuse (DPR): The introduction of reclaimed water (with or without retention in an engineered
storage buffer) directly into a drinking water treatment plant. This includes the treatment of reclaimed water
at an Advanced Wastewater Treatment Facility for direct distribution.
Indirect potable reuse (IPR): Deliberative augmentation of a drinking water source (surface water or
groundwater aquifer) with treated reclaimed water, which provides an environmental buffer prior to
subsequent use.
1.2	Target Audience
The target audience for this document is similar to that of the 2012 Guidelines—policy makers; legislators;
water planners; water reuse practitioners including utility staff, engineers, and consultants; and the general
public. The document is relevant across the spectrum of geographies in the United States. Specific
experiences are drawn from case studies on existing potable reuse approaches in the United States.
1.3	Objectives of this Document
With the increasing interest in potable reuse, there is a need to collect existing data on the state of the
industry to inform the decision-making process regarding potable reuse practices. This document will
supplement the 2012 Guidelines and note current practices and approaches in potable reuse, including the
existing technical and policy knowledge base. This document does not intend to provide guidance or norms
for potable reuse, but rather to present the current state of practice in the United States to assist planners
and decision-makers considering potable reuse approaches (refer to Table 1-1).
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2017 Potable Reuse Compendium
Chapter 1 | Introduction
Table 1-1. Document scope
Not included
Included - state of the industry
National recommendations or regulations for potable
reuse
Summary of federal laws impacting potable reuse and
state regulatory frameworks for potable reuse
Promotion of potable reuse
Opportunities, challenges, and trends in potable reuse
Design or treatment requirements for potable reuse
Potable reuse applications, treatment technologies,
research results, and case studies
Augmenting drinking water supplies with reclaimed water - potable reuse - may help communities meet
critical future water demands. Figure 1-1 and Figure 1-2 provide graphical representations of IPR and
DPR, respectively, including some illustrative examples both within the United States and abroad.
Potable reuse is one option in a diversified portfolio of water supply options. Water reuse can provide a
new, sustainable, and local water supply that reduces demands on limited community supplies and
improves water supply resiliency. Potable reuse may be desirable as part of a broader water resource
portfolio in a variety of circumstances (see Table 1-2).
Table 1-2. Local factors that, if present, may make potable reuse desirable as part of an overall
water supply portfolio
Factor
Description
Water supply stress
•	Drought or changes in precipitation patterns
•	Heightened withdrawals from competing demands such as population
growth, agriculture, and/or industry
•	Local supplies (or imported supplies) are limited for other reasons
Groundwater withdrawal impacts
•	Limited groundwater withdrawals
•	Challenges with seawater intrusion into coastal aquifers
Water quality challenges
associated with conventional
water sources
•	Risks from unintentional introduction of contaminants
•	Seasonal water quality disruptions (surface water)
Increasing costs or limitations on
discharges
•	Increasingly restrictive water quality requirements for discharges from
municipal WWTPs result in utilities seeking ways to recover costs by
creating a value for the treated wastewater
•	Elimination of ocean outfalls through regulatory action
Opportunities for non-potable
reuse are limited
•	High costs of installation and energy use of non-potable reuse distribution
systems (purple pipe, pump stations, and other infrastructure)
•	Water demands outpace non-potable reclaimed water supply opportunities
•	Seasonal non-potable reclaimed water demands
•	Water rights issues may arise when placing water into an environmental
buffer (in some locations this may favor DPR over IPR or non-potable reuse)
Since the publication of the 2012 Guidelines, a need has been identified for additional documentation of
potable reuse practices. The 2012 Guidelines provides guidance on IPR and describes DPR, but does not
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2017 Potable Reuse Compendium
Chapter 1 | Introduction
address current DPR practices. This document expands on the discussion of both IPR and DPR and
focuses on centralized municipal reuse; it does not cover storm water capture and use or on-site potable
reuse within a single building or facility.
Precipitation and Surface Runoff
(e.g. Singapore NEWater and
Upper Occoquan Service Authority,
Virginia)
IPR
(e.g. Orange County Water District
Groundwater Replenishment System,
California)	
IPR
IPR
Other types of
Reuse and/or
Discharge to
Receiving
Water Bodies
Surface Water
Blending
Drinking Water
Treatment Plant
Water Users
Distribution
System
Advanced
Wastewater Treatment
Conventional
Wastewater Treatment
Groundwater
Aquifer
Surface Water
Supply Reservoirs
Conventional Water Supply
Groundwater
Environmental Buffer
Figure 1-1. Planned IPR scenarios and examples (adapted from EPA, 2012a)
DPR

Precipitation and Surface Runoff
i
Conventional Water Supply
Surface Water
Groundwater


I
Blending
:x:
Drinking Water
Treatment Plant
Distribution
System
Water Users
Note:
When an Advanced Wastewater Treatment facility sends
treated reclaimed water directly to the distribution system,
the facility is regulated as a Public Water System.
(e.g. Cloudcroft, New Mexico)
Conventional
L
Advanced

Wastewater Treatment
¦**
Wastewater Treatment

Other types of
Reuse and/or
Discharge to




Engineered Storage Buffer
Receiving
Water Bodies
(e.g. Big Spring, Texas)
(e.g. El Paso, Texas)
Figure 1-2. Planned DPR scenarios and examples (adapted from EPA, 2012a)
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2017 Potable Reuse Compendium
Chapter 1 | Introduction
1.4 What is Potable Reuse?
As shown in Figure 1-1 and Figure 1-2, potable reuse involves the indirect (IPR) or direct (DPR) use of
highly treated municipal wastewater as a municipal drinking water source. In DPR, a drinking water
treatment plant receives reclaimed water directly and often blends it with other water sources before
treatment. The drinking water treatment plant, which the Safe Drinking Water Act (SDWA) regulates as
described in Chapter 3, may be located at the advanced wastewater treatment site or in another location.
IPR is similar to DPR, but IPR contains an environmental buffer. See Table 1-3 for more comparisons
between IPR and DPR.
Table 1-3. Comparison of IPR and DPR practices
Factor
IPR
DPR
Public
perception
Public perception may favor IPR
over DPR, but conditions are
site-specific. Public outreach and
involvement are important
components of any form of
potable reuse.
While DPR was previously referred to as "toilet-to-tap" and
"flush-to-faucet," more recent surveys indicate that the public
understands that the treated reclaimed water potentially has
higher quality than current sources; this is reflected in the San
Diego project where some public responses have called for the
highly-purified water not to be released to the environment
where its quality could be degraded.
Practicality
The lack of a suitable
environmental buffer may make
IPR impractical.
While the elimination of an environmental buffer provides a
higher level of control over the water, there may be a higher
level of monitoring and/or treatment complexity required to
offset the loss of response time and other potential benefits
provided by the buffer.
Costs
Environmental buffers can incur
significant costs to protect,
maintain, operate, and monitor.
Conveyance to the
environmental buffer may be
costly.
DPR may require a higher level of operator training and may
involve additional treatment steps beyond IPR.
Water quality
Environmental buffers have the
potential to either enhance or
degrade water quality, depending
on site-specific conditions.
DPR provides a high level of control; but, the process
monitoring and control may be more complicated than IPR
because response times are shorter.
Water rights
Water rights issues can
complicate IPR potential.
Water rights issues can complicate DPR potential.
Regulations
Several states have regulations
or guidelines governing IPR.
While the state of North Carolina recently lifted the regulatory
ban on DPR, to date, no states have formal regulations or
guidelines governing DPR. DPR facilities are currently
considered on a case-by-case basis in the United States
T reatment
Requirements
Several states have regulations
or guidelines for IPR treatment
requirements.
There may be no difference in the treatment objectives
between IPR and DPR; but, the level of process monitoring
and control and, in some cases, the total level of treatment
may be more complex for DPR, due to the absence of an
environmental buffer.
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2017 Potable Reuse Compendium
Chapter 1 | Introduction
1.5 Comparing Potable Reuse with Other Alternative Water Supplies and
Approaches
There are a number of approaches to addressing water supply challenges; conservation and other best
practices, such as addressing water loss, should be primary goals of any water resources management
program. But, when these activities cannot close the gap between supply and demand, other
implementation options can offset water demands. Some of these options may include non-potable reuse
and desalination, recognizing that both of these options carry implementation challenges. For example, it
may be difficult to obtain rights-of-way to construct and permit new purple pipe systems or brine disposal
for desalination projects.
1.5.1	Conservation
Conservation, water use efficiency improvements, and water loss control are important components of
managing water portfolios and important steps before implementing water reuse. The relative impact of
conservation measures is site-specific and largely based on the local history of incentives and education
(WRRF, 2014b). In some locations, the "low hanging fruit" of water use reductions already exist, and
additional opportunities are of marginal impact and may rely on customers investing in water-saving
appliances (WRRF, 2014b). One program that indicates water-saving appliances for interested consumers
is EPA's WaterSense program (EPA, 2017u). Reduced revenues from lower water sales may impact water
utilities' fiscal obligations and may result in higher customer water rates (WRRF, 2014b). Water loss
controls, including repair of leaking pipes and reduction of non-metered uses, can provide substantial
reductions in water supply demands without negatively impacting water sales.
1.5.2	Non-Potable Reuse
There are many applications within non-potable reuse, as described in depth in the 2012 Guidelines. In
general, water for non-potable reuse does not require the same level of treatment as potable reuse (AWWA,
2016). Centralized non-potable reuse requires dedicated pipe networks and pumping systems, or an
alternate delivery system such as trucking (WRRF, 2014b). Potable reuse scenarios utilize existing water
delivery infrastructure, rather than the new purple pipe infrastructure often mandatory in non-potable reuse
applications (WRRF, 2014b). This feature can facilitate water reuse in locations where laying new purple
pipe infrastructure is infeasible due to cost and other considerations.
1.5.3	Imported Water
Much of the U.S. southwest developed because of the ability to import water from other areas. However,
new imported water sources may be difficult to develop and sustain. Imported water sources can experience
large interannual variability and exposure to natural disasters, require significant energy, and can impose
significant adverse environmental consequences at water extraction sites (WRRF, 2014b).
1.5.4	Desalination
Seawater and brackish water desalination are viable options that provide high-quality, potable supply
worldwide (WRRF, 2014b). Seawater desalination offers a water supply resistant to drought, but it can be
susceptible to challenges from varying source water quality (red tides, storm events), and it can be costly
and energy intensive to operate (WRRF, 2014b). Some seawater desalination facilities, particularly in
California, face challenging regulatory requirements due to potential environmental impacts associated with
feed water intakes, brine discharges, and construction near sensitive shoreline habitats. Seawater
desalination is generally costlier than potable reuse (WRRF, 2014b). Where brackish aquifers exist, inland
brackish water desalination tends to be less energy intensive and expensive than seawater desalination.
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2017 Potable Reuse Compendium
Chapter 1 | Introduction
In locations where brine management cannot include coastal discharges (in both inland and coastal
locations), the desalination cost can be high due to energy or land requirements to treat brine; the cost
depends on the total dissolved solids (TDS) of the brackish source and disposal options (WRRF, 2014b).
1.6	Expansion of Potable Reuse
Table 1 -2 introduced some of the factors that may make potable reuse a valid water supply component for
communities. Potable reuse is expected to grow in the coming decades. A report from Bluefield Research
(2015) estimates that by 2025, municipal utilities' wastewater reuse will increase by 61 percent and will
require $11 .OB of capital expenditures. The report notes that 94 percent of this activity is expected to occur
in nine states. Potable reuse installations are expected to grow by 25 - 50 million gallons per day (MGD)
per year (100,000-200,000 m3/day added per year) (Bluefield Research, 2015). Current estimates suggest
that potable reuse could use about one-third of California's wastewater by 2020 (WRRF, 2014b).
1.7	Document Organization and Additional Reports
Table 1-4 provides a brief overview of this document's organization and content. See Table 1-5 for the
scope of additional reports on potable reuse.
Table 1-4. Document organization
Chapter
Overview of Contents
Chapter 1 - Introduction
Provides an overview of the drivers for potable reuse in the United States
and the objectives, scope, audience, and structure of the document.
Chapter 2 - Potable Reuse in the
United States and Abroad
Describes the history and current extent of IPR, DPR, and de facto reuse
practices in the United States and worldwide.
Chapter 3 - Safe Drinking Water Act
and Clean Water Act: Opportunities
for Water Reuse
Outlines existing federal regulatory structures that govern water,
wastewater, and surface water quality in the United States as they relate
to potable reuse. Defines regulatory challenges that exist in potable
reuse. Describes the approaches that specific states have taken to
regulate IPR and DPR.
Chapter 4 - Constituents in Potable
Reuse Water Sources
Describes chemical and microbial constituents that are present in potable
reuse water sources as the water moves through the potable reuse
system.
Chapter 5 - Risk Analysis
Provides an overview of frameworks appropriate to analyze risk in
potable reuse.
Chapter 6 - Treatment Technologies
for Potable Reuse
Provides an overview of the key categories of treatment unit processes
that are applicable to potable reuse.
Chapter 7 - Alternative Treatment
Trains for Potable Reuse
Illustrates examples of treatment trains used in the United States for
potable reuse.
Chapter 8 - Source Control
Outlines approaches that utilities take to eliminate industrial wastes of
concern before they reach the wastewater treatment plant (WWTP), with
a special focus on the particular source control concerns in potable
reuse.
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2017 Potable Reuse Compendium
Chapter 1 | Introduction
Chapter
Overview of Contents
Chapter 9 - Environmental and
Engineered Buffers
Describes what environmental and engineered buffers are capable of
providing in terms of treatment, blending, and retention time, with
particular focus on resultant water quality and process upset response
times.
Chapter 10 - Training, Operating, and
Monitoring
Provides an overview of operational approaches to manage risk,
including training requirements, and a brief discussion on monitoring
resources and indicators and surrogates.
Chapter 11- Cost of Potable Reuse
Provides a cost comparison between potable reuse and other alternative
water sources, including capital and operation and maintenance costs as
well as environmental and social elements of the triple bottom line.
Chapter 12 - Epidemiological and
Related Studies
Provides an overview of published epidemiological studies on potable
reuse.
Chapter 13 - Public Acceptance
Describes the current state of public acceptance for potable reuse in the
United States and how utilities have approached public involvement in
planning and operations.
Chapter 14- Research
Documents current research in the field of potable reuse.
Appendix A - Case Study Examples
of IPR and DPR in the United States
A-1: Los Alamitos Barrier Water Replenishment District of So. CA/Leo J.
Vander Lans Advanced Water Treatment Facility - Indirect Potable
Reuse
A-2: Orange County Groundwater Replenishment System Advanced
Water Treatment Facility
A-3: Gwinnett F. Wayne Hill Water Resources Center, Chattahoochee
River and Lake Lanier Discharge - Indirect Potable Reuse
A-4: Village of Cloudcroft PURe Water Project - Direct Potable Reuse
A-5: Colorado River Municipal Water District Raw Water Production
Facility Big Spring Plant - Direct Potable Reuse
A-6: Wichita Falls River Road WWTP and Cypress WTP IPR and DPR
Project
A-7: Potable Water Reuse in the Occoquan Watershed
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2017 Potable Reuse Compendium
Chapter 1 | Introduction
Table 1-5. Reports on potable reuse (not intended to be a complete survey)
Author/Sponsoring
Organization
Title
Year
U.S. Overview
Chemicals
Pathogens
Risk Assessment
Regulatory Summary
Treatment
Source Control
Buffers
Monitoring
Operations
Cost
Epidemiology
Public
Research
Case Studies
WateReuse Association
Innovative Applications in
Water Reuse
2004
~











~

~
Water Environment
Using Reclaimed Water to
















Federation/American Water
Augment Potable
2008

~
~

~
~



~


~

~
Works Association
Resources
















WateReuse Research

















Foundation Project 11-00,
Bureau of Reclamation,
California State Water
Direct Potable Reuse - A
Path Forward
2011





~
~
~
~



~
~
~
Resources Control Board

















Water Environment
Federation, American
Society of Civil Engineers
Municipal Wastewater
Reuse by Electric Utilities:
Best Practices and Future
Directions
2012



~
~









~

Water Reuse: Potential for
















National Research Council
Expanding the Nation's
Water Supply Through
Reuse of Municipal
Wastewater
2012
~
~
~
~
~
~
~
~
~
~
~
~
~
~

WateReuse Research
Foundation and National
Water Research Institute
Examining the Criteria for
Direct Potable Reuse
2013

~











~
~
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2017 Potable Reuse Compendium
Chapter 1 | Introduction
Author/Sponsoring
Organization
Title
Year
U.S. Overview
Chemicals
Pathogens
Risk Assessment
Regulatory Summary
Treatment
Source Control
Buffers
Monitoring
Operations
Cost
Epidemiology
Public
Research
Case Studies
WateReuse Research
Foundation Project 11-02
and Bureau of Reclamation
11-02-2
Potable Reuse: State of
the Science Report and
Equivalency Criteria for
Treatment Trains
2013

~
~

~
~

~
~




~
~
Australian Academy of
Technological Sciences and
Engineering
Drinking Water through
Recycling: The Benefits
and Costs of Supplying
Direct to the Distribution
System
2013
~
~
~

~
~

~


~

~

~
WateReuse Research
Foundation
Fit for Purpose Water: The
Cost of Overtreating
Reclaimed Water
2014










~

~


WateReuse Research
Foundation
The Opportunities and
Economics of Direct
Potable Reuse
2014
~

~




~


~



~
General Electric Power and
Water
Addressing Water Scarcity
Through Recycling and
Reuse: A Menu for
Policymakers
2015
~



~








~
~
Texas Water Development
Board and Alan Plummer
Associates
Texas Water Development
Board Direct Potable
Reuse Resource
Document
2015

~
~
~
~
~
~

~
~
~

~
~

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2017 Potable Reuse Compendium
Chapter 1 | Introduction
Author/Sponsoring
Organization
Title
Year
U.S. Overview
Chemicals
Pathogens
Risk Assessment
Regulatory Summary
Treatment
Source Control
Buffers
Monitoring
Operations
Cost
Epidemiology
Public
Research
Case Studies
American Waterworks
Association (AWWA), NWRI
(National Water Research
Institute), WEF (Water
Environment Federation),
and WateReuse
Framework for Direct
Potable Reuse
2015



~
~
~
~
~
~
~
~
~
~
~

Water Environment
Federation
Water Reuse Roadmap
Primer
2016
~
~
~
~
~
~
~
~




~
~
~
Water Research Foundation
Assessment of
Techniques to Evaluate
and Demonstrate Safety
of Water from Direct
Potable Reuse Treatment
Facilities
2016

~
~

~



~


~



Water Environment & Reuse
Foundation
Final Report: Potable
Reuse Research
Compilation Synthesis of
Findings
2016
~
~
~
~
~
~
~
~
~
~
~
~
~
~
~
World Health Organization
Potable Reuse: Guidance
for Producing Safe
Drinking-Water
2017
~
~
~
~
~
~
~
~
~





~
U.S. Environmental
Protection Agency
2017 Potable Reuse
Compendium
2017
~
~
~
~
~
~
~
~
~
~
~
~
~
~
~
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2017 Potable Reuse Compendium
Chapter 2 | Potable Reuse in the United States and Abroad
CHAPTER 2
Potable Reuse in the United States and
Abroad
2.1 Potable Reuse in the United States
Potable reuse has long been considered in the United States. As early as 1962, indirect potable reuse (IPR)
was used in Los Angeles County Sanitation District's Montebello Forebay project, followed in 1976 by
Orange County California's Water Factory 21, and again in 1978 in Fairfax County by Virginia's Upper
Occoquan Service Authority (EPA, 2012a). These pioneering IPR projects were the first in the United States
to use highly treated reclaimed water for potable reuse (EPA, 2012a). As a result, in 1980, EPA sponsored
a workshop on Protocol Development: Criteria and Standards for Potable Reuse and Feasible Alternatives
(EPA, 1980b). In the document's Executive Summary, the chairman of the planning committee remarked
that"[a] repeated thesis for the last 10 to 20 years has been that advanced wastewater treatment provides
a water of such high quality that it should not be discharged but put to further use. This thesis when joined
to increasing problems of water shortage, provides a realistic atmosphere for considering the reuse of
wastewater. However, at this time, there is no way to determine the acceptability of renovated wastewater
for potable purposes." The committee, at the time, recognized the potential for potable water reuse; but,
there were technical limitations and knowledge gaps which did not allow the group to fully understand the
potential public health impacts of the practice.
2.1.1 Current State of Potable Reuse in the United States
Table 2-1 summarizes some of the most prominent United States potable reuse projects. To date,
communities with severe drought conditions have implemented direct potable reuse (DPR), including Big
Spring, Texas (2013) and Wichita Falls, Texas (2014) (EPA 2012a; Dahl, 2014). In these locations, DPR
was either the most cost effective or the only feasible solution to water resource challenges (see Appendix
A for case studies on Big Spring and Wichita Falls). Table 2-1 also identifies the treatment technologies
employed downstream of conventional wastewater treatment for each potable reuse facility. The table lists
technologies used before the environmental discharge for IPR facilities and lists the entire treatment
scheme for DPR facilities with no environmental discharge.
Today, the United States produces 32 billion gallons of municipal wastewater effluent per day of which 7 to
8 percent is reclaimed (EPA, 2012a). Currently, planned IPR and DPR account for a negligible fraction of
the reused water volume (NRC, 2012a). However, potable reuse is a significant portion of the Nation's
water supply when considering de facto reuse (where treated wastewater impacts drinking water sources)
(NRC, 2012a). The map and table below show locations of example planned IPR and DPR projects around
the United States (Figure 2-1; Table 2-1).
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2017 Potable Reuse Compendium
Chapter 2 | Potable Reuse in the United States and Abroad
Table 2-1. Overview of selected planned IPR and DPR projects in the United States (not intended
to be a complete survey)
Project Name
Location
Year of
Installation
Status
Size
(MGD)
Type of
Reuse
Technologies
Montebello
Forebay,
County
Sanitation
Districts of Los
Angeles
County
USA - CA
1962
Operational
44
IPR:
Groundwater
recharge via
soil-aquifer
treatment
Media Filtration —> CI
Water Factory
21, Orange
County
USA - CA
1976
Built in 1976 but
superseded by
Orange County
GWRS in 2004
15
IPR:
Groundwater
recharge via
seawater
barrier
LC —> Air Stripping —>
RO —>
UV/AOP CI
Upper
Occoquan
Service
Authority,
Fairfax (UOSA)
USA - VA
1978
Operational
54
IPR: Surface
water
augmentation
LC —> Media
Filtration —> GAC —>
IX ^ CI
Denver Potable
Reuse
Demonstration
USA-CO
1980-1993
Studied ($30
million project)
1
DPR
demonstration
plant (not used
for drinking
water supply)
LC
Recarbonation —>
Filtration —> UV —>
GAC —> RO —> O3 —>
CI
Huecco Bolson
Recharge
Project, El
Paso Water
Utilities
USA - TX
1985
Operational
10
IPR:
Groundwater
recharge via
direct injection
LC —> Media
Filtration —> O3 —>
GAC —> O3 —> CI
Clayton County
USA - GA
1985
Operational
18
IPR: Surface
water
augmentation
CI UV
West Basin
Water
Recycling Plant
USA - CA
1995-2014
Operational
17.5
IPR:
Groundwater
recharge via
direct injection
03 —> MF —> RO —>
UV/AOP
Gwinnett
County
USA - GA
1999
Operational
60
IPR: Surface
water
augmentation
UF —> O3 —> GAC
Scottsdale
Water Campus
USA - AZ
1999-2014
Operational
20
IPR:
Groundwater
recharge via
direct injection
Media Filtration —>
MF —> RO —> UV
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Project Name
Location
Year of
Installation
Status
Size
(MGD)
Type of
Reuse
Technologies
Dominguez
Gap Barrier,
Terminal
Island, City of
Los Angeles
USA - CA
2002-2014
Operational
6
IPR:
Groundwater
recharge via
direct injection
Media Filtration —>
MF —> RO
Alamitos
Barrier, Water
Replenishment
District of So.
CA, Long
Beach
USA - CA
2005
Operational
8
IPR:
Groundwater
recharge via
direct injection
Media Filtration —>
MF —> RO —> UV/AOP
Chino Basin
Groundwater
Recharge
Project, Inland
Empire Utility
Agency
USA - CA
2007
Operational
18
IPR:
Groundwater
recharge via
soil-aquifer
treatment
Media Filtration —> CI
Orange County
Groundwater
Replenishment
System
(GWRS)
USA - CA
2008-2014
Operational
100
IPR:
Groundwater
recharge via
direct injection
and spreading
basins
UF —> RO —> UV/AOP
Arapahoe
County/Cotton
wood
USA-CO
2009
Operational
9
IPR:
Groundwater
recharge via
riverbank
filtration
Media Filtration —>
RO UV/AOP CI
Prairie Waters
Project, Aurora
USA - CO
2010
Operational
50
IPR:
Groundwater
recharge via
riverbank
filtration
Riverbank
Filtration —> ASR —>
Softening —>
UV/AOP BAC
GAC CI
San Diego
Advanced
Water
Purification
Demonstration
Project
USA - CA
2012
Operational
1
Demonstration
only (not used
for IPR or
DPR)
03 BAC —> MF —>
RO UV/AOP
Big Spring -
Colorado River
Municipal
Water District
(CRMWD)
USA - TX
2013
Operational
1.8
DPR: Blending
then
conventional
water
treatment
MF —> RO —>
UV/AOP
Conventional
Treatment
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Project Name
Location
Year of
Installation
Status
Size
(MGD)
Type of
Reuse
Technologies
City of
Clearwater and
the Southwest
Florida Water
Management
District
USA - FL
2013-2014
(study only)
Studied for 1 year
(pilot test)
3
(studied)
IPR:
Groundwater
recharge via
direct injection
UF —> RO —> UV/AOP
Wichita Falls -
IPR and River
Road WWTP
and Cypress
WTP DPR
projects
USA - TX
2014
Decommissioned
7
Temporary
DPR: Blending
prior to
conventional
treatment (long
term IPR will
be
implemented
by 2018)
MF —> RO —> UV —>
Storage —>
Conventional
Treatment
Cambria
Emergency
Water Supply
USA - CA
2014
Operational
0.65
IPR:
Groundwater
recharge via
direct injection
UF —> RO —> UV/AOP
Village of
Cloudcroft
USA-NM
2016
Built but delayed
0.026
DPR: Blending
prior to
treatment
MBR —> RO —>
UV/AOP
Storage —> UF —>
UV GAC CI
Hampton Road
Sanitation
District SWIFT
project
USA - VA
Under study
Under study
120
IPR:
Groundwater
recharge via
direct injection
Not determined
Franklin
USA -TN
Future
Not yet built
8
IPR: Surface
water
augmentation
Not determined
San Diego-
Advanced
Water
Purification
Facility
USA - CA
Under study
Under study
18
IPR: Surface
water
augmentation
Media Filtration MF —>
RO UV/AOP
El Paso -
Advanced
Water
Purification
Facility
USA - TX
Future
Under going
regulatory
approval
10
DPR: Straight
to distribution
system
MF—> RO—>
UV/AOP—> GAC—> CI
Abbreviations used for technologies:
ADF - Average Daily Flow; AOP - Advanced Oxidation Processes; ASR - Aquifer Storage and Recovery; BAC -
Biological Activated Carbon; CI - Chlorination; DAF - Dissolved Air Flotation; GAC- Granular Activated Carbon; IX-
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Ion Exchange; LC - Lime Clarification; MBR - Membrane Bioreactor; MF - Microfiltration; 03 - Ozone Disinfection;
PAC - Powdered Activated Carbon; RO - Reverse Osmosis; UF - Ultrafiltration: UV - Ultraviolet Radiation
D
Tenino
LOU Cleanwater Alliance, Hawk's Prairie
tgm.	Airway Heights
^	—Ephrata
-	Quincy
-	Royal City
I \ *VvEl
-Portland Clean Water Services (studied)
-Santa Clara (planned)
-Soquel Creek Water District (under study)
-Pure Water Monterey (planned)
-Cambria
-West Basin Water Recycling Plant
- Montebello Forebay, County Sanitation Districts of Los Angeles County
Dominguez Gap Barrier, City of Los Angeles
—Chino Basin Groundwater Recharge Project, Inland Empire Utility Agency
-Alamitos Barrier, Water Replenishment District % Aurora Prairie Waters
-Donald C. Tillman Groundwater Replenishment (understudy)
-Water Replenishment District Groundwater Reliability Improvement Program (under construction)
-OCWD & OCSD Groundwater Replenishment System Advanced Water Treatment Facility
-Water Factory 21 (built but replaced by OCGWRS In 2004)
-Eastern Municipal Water District (under study)
•. Loudoun County
Upper Occoquan Service Authority £>
~ Hampton Roads Sanitation District
(planned)
Franklin (planned)
• Raleigh (understudy)
Padre Dam (under study and demonstration)
— San Diego (under design and demonstration)
• Scottsdale
Water Campus W
Cloudcroft (delayed) —
#	Indirect Potable Reuse
•	Direct Potable Reuse
i—Big Spring, Colorado River Municipal Water District
•.Wichita Falls
I	% North Texas Municipal Water District
&	% Tarrant Regional Water District
- • Brownwood (approved but not built)
Abilene
El Paso Water Utilities (planned)
-Hueco Bolson Recharge Project,
El Paso Water Utilities
> Laguna Mad re
Gwinnett County
: Clayton County
C> Jacksonville (under study)
Clearwater (planned) •>
Hollywood (under study) •
W
West Palm Beach (decommissioned)
fy Miami (studied)
Figure 2-1. Planned and constructed IPR and DPR projects in the United States as of 2017
2.1.2 Water Supply Enhancement
While DPR is considered a relatively new concept, the 2012 Guidelines state, "[DPR] should be evaluated
in water management planning, particularly for alternative solutions to meet urban water supply
requirements that are energy intensive and ecologically unfavorable." In regions that face imminent water
supply shortages due to population pressures or changes in historical precipitation patterns, the only
options to expand water supplies may include water importation, saltwater desalination, and water reuse
(Snyder, 2014). Especially in inland locations, water reuse may be the only viable option (Snyder, 2014).
Examples include Big Spring, Texas (1.8 million gallons per day (MGD)) and Wichita Falls, Texas (5 MGD),
which temporarily implemented DPR in response to extreme drought (Nix, 2014; see Appendix A). Wichita
Falls designed a temporary DPR scheme that successfully implemented DPR for an 11-month period; a
permanent iPR installation will supersede the now decommissioned DPR scheme (see Appendix A).
Brownwood, Texas is also evaluating and pursuing DPR because of severe drought (Miller, 2015).
Cloudcroft, New Mexico recently permitted a DPR project in response to limited water sources for the
seasonal tourist population, but it is not in operation (see Appendix A).
It is important to note that U.S. communities with adequate annual rainfall are also evaluating potable reuse
as a potential component of future water resource portfolios. For example, the City of Franklin, Tennessee
is considering planned IPR to expand its ability to provide reasonably priced, high-quality drinking water to
customers while also addressing discharge permitting ("City of Franklin"). In Raleigh, North Carolina ("City
of Raleigh") and Gwinnett County, Georgia (see Appendix A), local utilities are studying direct potable
reuse.
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2017 Potable Reuse Compendium
Chapter 2 | Potable Reuse in the United States and Abroad
2.1.3 De facto Reuse in the United States
Upstream or upgradient wastewater discharges contribute to many of our Nation's water supplies. Typically,
facilities using these as drinking water sources do not characterize their process as potable reuse; but it is
instructive to consider this practice as de facto reuse, whether intentional or not.
There is a general public perception that rivers and lakes help attenuate wastewater-derived contaminants
before use as a downstream drinking water source. Generally, the factors that determine the concentration
of wastewater-based contaminants in source water include the type and performance of the wastewater
treatment plant (WWTP), dilution, residence time in the surface water, and water body characteristics
(including depth, temperature, turbulence, water quality, and sunlight exposure) (NRC, 2012a).
Large cities that draw their drinking water from rivers with numerous upstream wastewater discharges (for
example, Atlanta, Philadelphia, Houston, Nashville, Cincinnati, New Orleans, and Washington D.C.) utilize
de facto reuse (Bell et al., 2016a). For instance, in Houston, an average of 50 percent of the water entering
the water treatment plant (WTP) drawing from Lake Livingston is made up of wastewater effluent from the
Dallas/Fort Worth area upstream (NRC, 2012a). While the drinking water treatment technologies used in
these de facto reuse locations yields potable water that meets current drinking water regulations, many
wastewater impacted source waters in de facto potable reuse locations receive less monitoring and
treatment prior to entering the potable water supply than planned potable reuse projects (NRC, 2012a).
Recent studies contribute to understanding the extent of de facto reuse nationwide. Using a mass balance
approach, the National Research Council (NRC) used EPA WWTP discharge data to estimate that of the
32 billion gallons per day (BGD) of U.S. municipal wastewater effluent, approximately 12 BGD discharge
into an ocean or estuary, and 20 BGD discharge into surface water sources (NRC, 2012a). These
discharges to surface water sources, which represent 63 percent of all municipal effluent generated daily
in the United States, re-enter the hydrologic cycle and may become part of downstream drinking water
sources, sources for irrigation, power generation, and ecological flows.
2.2 Potable Reuse Worldwide
There are a number of facilities worldwide that are currently operating successful potable reuse processes.
Several of these facilities are identified in Figure 2-2 and Table 2-2.
The most notable project employing DPR is the Goreangab Water Reclamation Plant in Windhoek, Namibia
(EPA, 2012a). Windhoek was the first city to implement long-term potable reuse without the use of an
environmental buffer. Windhoek's experimental DPR project began in 1969 and was expanded in 2002 to
5.5 MGD (EPA, 2012a). It can supply about 50 percent of the city's potable water demand (NRC, 2012a).
In Beaufort West, South Africa, a severe drought in 2010 resulted in the need for trucks to deliver water to
more than 8,000 homes (Khan, 2013). The Beaufort West Water Reclamation Plant was commissioned in
2011 to provide up to 0.6 MGD (2.1 ML/d) (Khan, 2013).
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2017 Potable Reuse Compendium Chapter 2 | Potable Reuse in the United States and Abroad
Essex and Suffolk
Langford, UK*
Toreele Reuse Plant
Wulpen, Belgium
Sulaibiya Wastewater Treatment & Reclamation Plant
Sulaibiya, Kuwait
Mexico City, Mexico
Vrishabhavathi Valley Project
Bangalore, India
(studied)
i NEWater
Singapore
Sao Paulo, Brazil <
(studied)
Goreangab
Water Reclamation Plant
Windhoek, Namibia #
peMalahleni Municipality
I South Africa
Indirect Potable Reuse
• Direct Potable Reuse
_ • eThekwini Municipality
Beaufort West • South Africa
South Africa	(studied and put on hold)
Beenyup Advanced
Water Recycling Plant
Perth, Australia
Western Corridor Project
SE Queensland, Australia
(offline)
Figure 2-2. Overview of selected planned and constructed IPR and DPR projects worldwide
(not intended to be a complete survey)
The eThekwini Municipality in South Africa, which includes Durban and surrounding towns, is rapidly
approaching a water shortage (Khan, 2013). The Municipality formally began exploring water resource
alternatives in 2008, including dams, desalination, rainwater harvesting, and potable water reuse.
Proposals for a DPR process were put on hold in 2012 following negative media reports, with seawater
desalination being pursued as a key alternative (Khan, 2013).
A study by the Australian Academy of Technological Sciences and Engineering (ATSE) (Khan, 2013)
published findings on the science, technology, and engineering associated with DPR, indicating that with
the rapid advancements in recent decades,
"DPR is growing internationally and will be an expanding part of global drinking water supply in
the decades ahead. DPR is technically feasible and can safely supply drinking water directly into
the water distribution system, but advanced water treatment plants are complex and need to be
designed correctly and operated effectively with appropriate oversight. Current Australian
regulatory arrangements can already accommodate soundly designed and operated DPR
systems."
"High levels of expertise and workforce training within the Australian water industry are critical.
These must be supported by mechanisms to ensure provider compliance with requirements to
use appropriately skilled operators and managers in their water treatment facilities. This will be no
less important for any future DPR implementation and to maintain high levels of safety with
current drinking water supply systems."
Singapore's NEWater plants are some of the best known IPR systems in the world (WHO, 2017; EPA,
2012a). Potable reuse can satisfy up to 40 percent of Singapore's water demand, and it has helped the
city-state pursue water sustainability (WHO, 2017; EPA, 2012a). The potable water produced is consistently
noted for achieving drinking water standards, including EPA drinking water standards and World Health
Organization guidelines (WHO, 2017; EPA, 2012a).
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In Brazil, the worst drought in 80 years spurred the government to take action prior to the recent Olympics
(Steadman, 2015). While Sao Paulo has reduced consumption by 20-25 percent, the city's two rivers remain
heavily polluted (Steadman, 2015). A Brazilian state company requested Suez Environment propose
solutions to this challenge, and Suez returned four possible solutions with the first being IPR (Steadman,
2015). The city has a significant amount of municipal wastewater that is not currently reused; when
considering the available treatment technologies, it would be possible to reuse this source by returning
highly treated water into one of the large reservoirs (Steadman, 2015). The City of Campinas is already
testing IPR, potentially indicating acceptance of this practice (Steadman, 2015).
Table 2-2. Overview of selected planned IPR and DPR projects outside of the United States (not
intended to be a complete survey)
Project Name
Lo
ca
tion Year of
Installatio
n
Status
Size
(MGD)
Type of Reuse
Technologies
Vrishabhavathi
Valley project,
Bangalore
India
N/A
Studied
53
IPR: Surface water
recharge
UF -~ GAC -~ CI
Goreangab Water
Reclamation
Plant, Windhoek
Namibia
1969;
expanded
in 2002
Operational
5.5
DPR: Blending
prior to treatment
PAC -~ 03 -~
Clarification —> DAF
—> Sand Filtration —>
03/AOP -~
BAC/GAC —> UF —>
CI
Toreele Reuse
Plant, Wulpen
Belgium
2002
Operational
1.8
IPR: Groundwater
recharge via
infiltration ponds
UF —> RO —> UV
NEWater, Bedok
Singapore
2003
Operational
23
IPR: Surface water
augmentation
UF —> RO —> UV
NEWater, Kranji
Singapore
2003
Operational
15
IPR: Surface water
augmentation
UF —> RO —> UV
Essex and
Suffolk, Langford
United
Kingdom
2003
Operational
8
IPR: Surface water
augmentation
Biological Filtration
—> UV disinfection
Western Corridor
Project,
Southeast
Queensland
(Bundamba,
Luggage Point,
Gibson Island)
Australia
2008
Intermittent
Operation for NPR
only
61
Designed for IPR:
Surface water
augmentation into
drinking water
reservoir
(never used for
IPR due to
changes in local
conditions)
UF —> RO —>
UV/AOP
George
South
Africa
2009
Intermittent
Operation when
necessary
2.6
IPR: Surface water
augmentation
Drum Screen —> UF
^Cl
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2017 Potable Reuse Compendium
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Project Name
Lo
ca
tion Year of
Installatio
n
Status
Size
(MGD)
Type of Reuse
Technologies
NEWater, Changi
Singapore
2010;
expanded
in 2017
Operational
122
IPR: Surface water
augmentation
UF —> RO —> UV
Beaufort West
South
Africa
2011
Built
0.26
DPR: Blending with
pretreated
conventional
sources
Sand Filtration —> UF
^ RO^
UV/AOP CI
Beenyup
Groundwater
Replenishment
Reuse Trial,
Perth, Australia
Australia
2011
Decommissioned
1.3
IPR: Groundwater
recharge via direct
injection
UF —> RO —> UV
Beenyup
Advanced Water
Recycling Plant,
Perth, Australia
Australia
2016;
expansion
ongoing
Operational
10
IPR: Groundwater
recharge via direct
injection
UF —> RO —> UV
Mexico City
Mexico
Ongoing
Ongoing -
untreated
wastewater used
for agricultural
irrigation and
incidental
groundwater
replenishment
570
IPR: Groundwater
infiltration
None
Abbreviations used for technologies:
ADF - Average Daily Flow; AOP - Advanced Oxidation Processes; ASR - Aquifer Storage and Recovery; BAC -
Biological Activated Carbon; CI - Chlorination; DAF - Dissolved Air Flotation; GAC- Granular Activated Carbon; IX-
lon Exchange; LC - Lime Clarification; MBR - Membrane Bioreactor; MF - Microfiltration; 03 - Ozone Disinfection;
PAC - Powdered Activated Carbon; RO - Reverse Osmosis; UF - Ultrafiltration; UV - Ultraviolet Radiation
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2017 Potable Reuse Compendium Chapter 3 | SDWA and CWA: Opportunities for Water Reuse
CHAPTER 3
Safe Drinking Water Act and Clean Water
Act: Opportunities for Water Reuse
Currently, there are no federal regulations specifically governing potable water reuse in the United States.
There are state regulations, policies, and state and federal guidance addressing certain aspects of the
process, including specific requirements for wastewater treatment and drinking water treatment.
Additionally, several states have supported currently operational potable reuse projects. While there are no
federal regulations directly addressing potable water reuse, it is a permissible approach to produce drinking
water, provided all generally applicable Safe Drinking Water Act (SDWA), Clean Water Act (CWA), and
state requirements are met.
3.1 Existing Regulatory Opportunities for Potable Reuse
The SDWA and the CWA provide the core statutory requirements relevant to potable water reuse. While
the SDWA and the CWA are the federal laws that identify water quality criteria and standards (either in
guidance or regulation), regulations specific to water reuse exist only at the state level.
As of the summer of 2017, no state had developed comprehensive, final regulations fordirect potable reuse
(DPR); but, North Carolina approved legislation in 2014 allowing limited DPR use with engineered storage
buffering and blending with other sources (see Table 3-2). In 2016, the California State Water Resource
Control Board concluded that it is feasible to develop uniform water quality criteria for DPR, a first step in
consideration of state regulation development (CSWRCB, 2016). Some states are developing regulatory
approaches for planning, permitting, and implementing risk management strategies to support potable
reuse projects; these actions are in response to water supply challenges, population shifts and growth, and
increasing interest in providing more resilient water supplies.
Historical Perspective
The concept of reclaiming water for potable use is not new. In a 1972 memo titled EPA Policy Statement
on Water Reuse, EPA found that "the direct introduction of chemicals from a waste-stream and their build-
up through potable system-waste system recycling can present increased long- term chronic hazards,
presently undefined." The memo concluded that: "We do not have the knowledge to support the direct
interconnection of wastewater reclamation plants into municipal water supplies at this time," and "an
accelerated research and demonstration program is vitally needed to: Develop basic information and
remedial measures with respect to viruses, bacteria, chemical build-ups, toxicological aspects and other
health problems. Develop criteria and standards to assure health protection in connection with reuse."
(EPA, 1972).
However, as early as 1980, EPA noted "that advanced wastewater treatment provides a water of such high
quality that it should not be discharged but put to further use" (EPA, 1980b). In 1982, the National Research
Council (NRC) addressed water quality criteria for reuse in the report Quality Criteria for Water Reuse.
Although the report did not endorse potable reuse, it provided some guidance on the topic. (NRC, 1982).
In 1998, the NRC published Issues in Potable Reuse: The Viability of Augmenting Drinking Water Supplies
with Reclaimed Water that reflected significant changes from the 1982 report, including technological
advances and emerging public health concerns. Additionally, the report analyzed several U.S. indirect
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2017 Potable Reuse Compendium Chapter 3 | SDWA and CWA: Opportunities for Water Reuse
potable reuse (IPR) projects and concluded that reclaimed water might safely supplement raw water
supplies, subject to further treatment. (NRC, 1998).
In 2012, the NRC published Water Reuse: Potential for Expanding the Nation's Water Supply through
Reuse of Municipal Wastewater. The report concluded that the use of reclaimed water to augment potable
water supplies has significant potential to contribute to the Nation's future needs. It also concluded that
potable water reuse projects only account for a relatively small fraction of the total volume of water currently
being reused when considering de facto or unplanned water reuse (NRC, 2012a). The committee
commented on the potential utility of reused water (NRC, 2012b):
"... with recent advances in technology and design, treating municipal wastewater and reusing
it for drinking water, irrigation, industry, and other applications could significantly increase the
nation's total available water resources, particularly in coastal areas facing water shortages.
Moreover, new analyses suggest that the possible health risks of exposure to chemical
contaminants and disease-causing microbes from wastewater reuse do not exceed, and in
some cases, maybe significantly lower than, the risks of existing water supplies."
EPA, in partnership with Camp Dresser & McKee (now CDM Smith), published informational guidelines
for water reuse in 1980 and updated them in 1992, 2004, and 2012 (EPA, 1980a; EPA, 1992; EPA,
2004; EPA, 2012a). The documents were intended to serve as authoritative references on water reuse
practices. Among other things, the most recent guidelines (2012) include a discussion of water reuse in
the United States and in other countries (developed in partnership with the U.S. Agency for International
Development), advances in reuse-relevant wastewater treatment technologies, factors that would allow
expansion of safe and sustainable water reuse, and presents case studies. The 2012 water reuse
guidelines can be found at: https://nepis.epa.aov/Adobe/PDF/P100FS7K.pdf.
3.1.1 Clean Water Act (CWA)
The foundation of wastewater treatment requirements in the United States is the 1948 Federal Water
Pollution Control Act. During the 1972 amendments, the law became known as the "Clean Water Act."
Since then, the law has been reauthorized three times (1977, 1981, and 1987). The CWA authorizes water
quality standards for surface waters and regulates pollutant discharge into U.S. waters with technology-
based and water-quality based permit limits (EPA, 2017j). The subsections below describe specific aspects
of the CWA that may apply to potable reuse.
3.1.1.1 Ambient Water Quality Criteria (AWQC)
To protect a given use of a water body, including those that serve as designated drinking water supplies,
section 304(a)(1) of the CWA requires EPA to develop science-based water quality criteria. These criteria,
based on pollutant concentrations and environmental or human health effects data, are developed for the
protection of both aquatic life and human health. The criteria developed under section 304(a)(1) serve as
recommendations to states and authorized tribes creating water quality standards, specifically water quality
criteria, under section 303(c). 40 CFR 131.11(b) presents the options for states and/or authorized tribes
establishing numerical water quality criteria (EPA, 2000a):
•	Adopt EPA's 304(a) recommendations.
•	Adopt 304(a) criteria but modify them based on site-specific characteristics.
•	Develop their own scientifically-based criteria.
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Currently, EPA has 122 recommended water quality criteria for the protection of human health and 60
recommended water quality criteria for the protection of aquatic life (EPA, 2017p). EPA also has
recommended recreational water quality criteria for enterococci and E. coli (EPA, 2012c). These water
quality criteria protect human health and the environment for primary contact recreational and drinking water
supply uses.
Microbial (Pathogen) Criteria
Microbial criteria can protect the public from exposure to harmful levels of pathogens during primary contact
recreational activities such as swimming.
As discussed in the 2012 Recreational Water Quality Criteria (RWQC), EPA currently recommends the
culture-enumerated fecal indicator bacteria, E. coli, and enterococci to characterize the level of fecal
contamination present in environmental waters (EPA, 2012c). However, there is a growing body of scientific
evidence demonstrating that these culture-based bacterial indicators may not be good predictors of the
presence of pathogenic enteric viruses and protozoa (EPA 2015a).
As of 2017, EPA is considering the use of male-specific (F-specific) and somatic coliphages as possible
viral indicators of fecal contamination in ambient water. Coliphages are a type of virus that infects E. coli.
EPA published a literature review titled Review of Coliphages as Possible Indicators of Fecal Contamination
for Ambient Water Quality in 2015. The review summarizes the scientific literature on coliphage properties
and evaluates its suitability as an indicator of fecal contamination in ambient water (EPA, 2015a).
Additionally, EPA has published two standardized enumeration methods for male-specific and somatic
coliphages (EPA, 2015a). The development of a coliphage criterion for ambient water could ensure that
wastewater treatment plants are effectively reducing viruses in discharges. A coliphage criterion could also
identify viral source water quality and its suitability for potable reuse waters.
Because of concerns about future increases in microbial contamination and potential new threats, EPA is
considering future strategies that integrates the goals of both the CWA and the SDWA. In general, the new
strategy objectives are to address important contamination sources, anticipate emerging problems, and
efficiently use the CWA and the SDWA programmatic and research activities to protect public health. To
help support this new approach, EPA has completed several risk assessment documents. First, EPA issued
Microbial Risk Assessment (MRA) Tools, Methods, and Approaches for Water Media, which can assist risk
assessors and scientists in developing rigorous and scientifically defensible risk assessments for
waterborne pathogens (EPA, 2014a). The document describes a human health risk assessment framework
for microbial hazards in water media (e.g., pathogens in treated drinking water, source water for drinking
water, recreational waters, shellfish waters, and biosolids) that is compatible with other existing risk
assessment frameworks for human health and chemical hazards. Secondly, EPA researchers and partners
published two quantitative microbial risk assessments (QMRA) specifically addressing DPR (Soller et al.
2017; Soller et al., 2018). Together, these publications provide a risk methodology useful for regulators
considering potable reuse projects as they consider how to best protect public health. Finally, EPA is
working to finalize technical support material documents for QMRA, which will serve as a tool for states to
use when developing CWA water quality standards based on local conditions and non-human sources of
fecal contamination (EPA, 2014b).
Chemical Criteria
Human health ambient water quality criteria are numeric values that limit chemical concentrations in the
Nation's surface waters to achieve designated uses and protect human health (EPA, 2015b). EPA develops
these criteria by assessing the pollutant's effect on human health and the environment; States and tribes
may use these criteria to establish water quality standards (CWA section 304(a)(1); EPA, 2015b). These
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standards ultimately provide a basis for National Pollutant Discharge Elimination System (NPDES) permit
limits in designated waters. A human health criterion provides guidance on the pollutant concentration in
water that is not expected to pose a significant risk to human health (EPA, 2015b).
In 2015, EPA issued updated National Recommended Human Health Water Quality Criteria for 94 chemical
pollutants to incorporate new information on exposure (body weight, drinking water, and fish consumption
rates), bioaccumulation factors, health toxicity values for carcinogenic and non-carcinogenic compounds,
and relative source contributions (EPA, 2015b).
3.1.1.2 NP rogram
To help attain ambient water quality criteria, the CWA provides for EPA pollution control and permitting
programs to limit the discharge of harmful pollutants into navigable waters (EPA, 2017j). With respect to
protecting uses of the Nation's waters including drinking water sources, the National Pollutant Discharge
Elimination System (NPDES) is a permit program under section 402 of the CWA that regulates point source
discharges. Point sources include industrial, municipal, or other facilities that discharge effluent
(wastewater) orstormwater into receiving surface waters (CWA sections 402 and 502(14)). Publicly owned
treatment works (POTWs) are a subset of dischargers that discharge treated municipal and industrial
wastewater and are required to have NPDES permits; however, dischargers connected to municipal sewer
systems (i.e., indirect dischargers) do not need a NPDES permit (section 402; EPA, 2017q). The National
Pretreatment Program controls industrial and commercial indirect dischargers (see 40 CFR 403.1). Most
NPDES permits are issued by authorized states, however, EPA remains the permitting authority in
Massachusetts, New Hampshire, New Mexico, Idaho, and for federal Indian lands and most U.S. territories
(EPA, 2017a). There are two types of permits under the NPDES program: individual permits and general
permits. Individual permits are issued for specific facilities whereas general permits cover discharges from
multiple facilities that are similar in nature (EPA, 2013a).
NPDES permit limits are established using two basic approaches for protecting and restoring the Nation's
waters. One is a technology-based approach, whereby the permitting authority bases permit conditions on
either secondary treatment standards for POTWs, national effluent limitations guidelines for certain
categories of non-POTWs, or case-by-case on the permit writer's best professional judgment (see CWA
section 301(b) and 40 CFR 125.3). The other approach establishes water quality-based permit limits
designed to ensure attainment of the water quality standards applicable to a particular water body. Where
the permitting authority determines that technology-based effluent limits would not ensure attainment of the
water quality standards, a more stringent water quality-based effluent limitation would be included in the
permit (EPA, 2013a).
If the permitting authority determines that a discharge has a "reasonable potential" to cause or contribute
to an excursion above an applicable water quality standard, the permitting authority must develop a limit
that derives from and ensures compliance with the applicable standard (40 CFR 122.44(d)). Where a water
body is already meeting its water quality standards, then those standards are used in calculating the water
quality-based effluent limit for the NPDES permit, and the permitting authority may consider dilution of the
effluent and receiving water in calculating the limit if state water quality standards allow (40 CFR 122.44(d)).
Because effluent limits derive from and ensure compliance with all applicable water quality criteria (e.g.,
aquatic life protection criteria, human health criteria, wildlife criteria) there are instances in which the
discharge limits for a given contaminant at a municipal wastewater treatment plant (WWTP) may be more
stringent than drinking water maximum contaminant levels (MCLs) derived under the SDWA. These
differences are seen, in part, because the risk-based approach for establishing the ambient water quality
criteria for protection of aquatic life and wildlife differ from the risk management approach for establishing
MCLs.
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If a water body is not meeting its water quality standards and has a total maximum daily load (TMDL), then
the permitting authority must develop water quality-based limits that are consistent with that TMDL
(EPA,2017i).
3.1.1.3	Impaired Waters and Total Maximum Daily Loads (TWIDLs)
Under section 303(d) of the CWA, jurisdictions (states, territories and authorized tribes) must evaluate and
develop a list of "water quality-limited segments," i.e., waters that do not meet or are not expected to meet
applicable water quality standards after application of technology-based effluent requirements. Jurisdictions
must develop TMDLs for the specific pollutant(s) and water body combinations on the 303(d) list. The TMDL
identifies the maximum amount of a pollutant that a water body can receive and still meet water quality
standards and allocations the pollutant loadings among wasteload allocations for point sources and load
allocations (LA) for nonpoint sources and natural background with a margin of safety.
3.1.1.4	National Pretreatment Program
EPA promulgates pretreatment standards under section 307 of the CWA. These standards apply to all non-
domestic dischargers that discharge wastewater to POTWs. Some pretreatment standards are
promulgated directly into the General Pretreatment Regulations for Existing and New Sources of Pollution
("Pretreatment Regulations") (40 CFR 403), and these are referred to as the General and Specific
Prohibitions. EPA also identifies best available technology that is economically achievable for industry
categories and promulgates national pretreatment standards for indirect dischargers at the same time it
promulgates effluent limitations guidelines for direct dischargers under sections 301(b) and 304(b) of the
CWA. Such pretreatment regulations are known as categorical pretreatment standards. Categorical
pretreatment standards are designed to prevent the discharges of pollutants that pass through, interfere
with, or are otherwise incompatible with the operation of POTWs on a nationwide basis (see 40 CFR 403.2
and 403.6).
The National Pretreatment Program requires, in specific circumstances, that POTWs develop local
pretreatment programs to implement national pretreatment standards (see 40 CFR 403.5). A POTWs
NPDES permit lists enforceable requirements for the development and implementation of its pretreatment
program (see 40 CFR 403.8). Among other things, a POTW must evaluate its facility's capabilities in order
to prevent pass through or interference with its operations. Based on this evaluation, the POTW adopts
local limits to address specific needs and concerns of the POTW treatment plant, its sludge (and sludge
management practices), and its receiving waters (including reuse concerns). POTWs must also have the
legal authority to control industrial users' contributions through a permit, order, or similar means, which may
include either general or individual control mechanisms. These control mechanisms impose monitoring and
reporting requirements to assess the industrial users' compliance with the more stringent of all three types
of pretreatment standards.
3.1.2 5c liking Water Act (SDWA)
The SDWA, originally passed by Congress in 1974 to protect the Nation's public drinking water supply, is
the law that provides EPA the authority to regulate public water systems. A public water system is "a system
for the provision to the public of water for human consumption through pipes or other constructed
conveyances, if such system has at least fifteen service connections or regularly serves at least twenty-five
individuals" (42 U.S.C. 300f(4)(A)). A drinking water treatment plant in a potable reuse system would be
considered a public water supply system. An advanced wastewater treatment facility (AWTF) would also
be considered a public water supply system in DPR scenarios where treated water enters a distribution
system directly after treatment from that AWTF. The law, amended in 1986 and 1996, requires actions to
protect drinking water and its sources—including rivers, lakes, reservoirs, springs, and groundwater wells.
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The SDWA does not regulate private wells or systems that serve fewer 15 service connections or fewer
than 25 individuals for at least 60 days a year (EPA, 2017b). It authorizes and requires EPA to set national
health-based standards for drinking water to protect against naturally-occurring and anthropogenic
contaminants found in drinking water and drinking water sources; this includes contaminants from
wastewater discharges (EPA, 2017b). EPA, states, and utilities work together to meet these standards. Any
water reuse application should not compromise the ability of the affected public water system to comply
with the requirements of the SDWA. It should also be recognized that, depending upon how the water reuse
application is designed or operated, there may be opportunities to facilitate compliance with the SDWA or
improve finished water quality (e.g., by application of advanced treatment processes).
While the CWA addresses protection of surface drinking water sources, there are still potential source water
threats to safe drinking water, such as improperly disposed of household and industrial chemicals, runoff
of nutrients from non-point sources, and pesticides. Improperly treated or disinfected drinking water, or
drinking water that travels through an improperly maintained or operated distribution system may also pose
a health risk. Regulations developed under the SDWA require that systems take appropriate measures to
address these risks.
Originally, the SDWA focused primarily on treatment as the means of providing safe drinking water at the
tap. The 1996 amendments greatly enhanced the existing law by adding new requirements: consumer
confidence reports, a cost-benefit analysis for every new standard, an assessment of threats that may
warrant source water protection, operator training, significant infrastructure funding for water system
improvements, and strengthened controls over microbial contaminants and disinfection by-products (EPA,
2015c). This approach strives to ensure the quality of drinking water by protecting it from source to tap.
The SDWA requires EPA to set enforceable drinking water standards; EPA typically approves states and
authorized tribes for implementation and enforcement responsibilities (SDWA section 1413). EPA retains
oversight authority over tribal, state, local, and water providers' drinking water programs. The SDWA
defines primary and secondary drinking water standards, and also includes special provisions for programs
that protect both finished water and drinking water sources.
3.1.2.1 National Primary Drinking Water Regulations and Maximum Contaminant
Levels
National Primary Drinking Water Regulations (NPDWRs) are drinking water standards developed under the
authority of the SDWA that apply to U.S. public water systems and undergo review every six years (EPA,
2017b). In general, to set a NPDWR, EPA identifies contaminants for potential regulation (EPA, 2017c). If
EPA decides to regulate a contaminant, EPA determines a maximum contaminant level goal (MCLG) for
the contaminant. The MCLG is the level of a contaminant in drinking water below which there is no known
or expected health risks (EPA, 2017c). EPA then specifies an enforceable MCL, which is the maximum
permissible level of a contaminant in drinking water delivered to any public water system user (EPA 2017c).
MCLs are standards set as close to the MCLGs as feasible after considering best available treatment
technologies, detection methods, and cost. The SDWA defines feasible as the level that may be achieved
with the use of the best available technology, treatment technique(s), and other available means (EPA,
2015c). Once the technical feasibility is determined, the MCL is established to account for economic factors
and projected health benefits. If it is not economically or technically feasible to set an MCL, or when there
is no reliable or economically feasible method to detect or measure contaminants in the water, EPA sets a
treatment technique (TT) that specifies the level of treatment that a system must apply to remove or
minimize that specific contaminant (EPA 2017c).
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NPDWRs are legally enforceable standards to protect public health. As opposed to NPDWRs, Secondary
Drinking Water Regulations are guidelines that regulate contaminants based on aesthetic or cosmetic
effects; these contaminants do not threaten public health and therefore are not legally enforceable (EPA,
2017k).
EPA has set MCLs for contaminants from six categories: microorganisms, disinfectants, disinfection by-
products, inorganic chemicals, organic chemicals, and radionuclides (EPA, 2017n). Also, treatment
technique requirements exist for three of these categories: disinfection by-products, pathogens, and lead
and copper. EPA has also set Maximum Residual Disinfectant Levels (MRDLs) for disinfectants (40 CFR
141.2).
3,1.2.2 Unregulated Contaminants
Unregulated Contaminant Monitoring Rule
The 1996 SDWA amendments required EPA to establish criteria for an unregulated contaminant monitoring
program and publish a list of contaminants to monitor every five years (EPA, 2017b; EPA 2017o). EPA
uses the Unregulated Contaminant Monitoring Rule (UCMR) to collect data on contaminants of potential
health concern that are suspected to be present in drinking water but do not have health-based standards
under the SDWA (EPA, 2017o).
EPA develops the UCMR list of contaminants largely based on the Contaminant Candidate List (CCL). The
1996 SDWA Amendments describe the process (EPA, 2017o):
•	Monitoring of up to 30 contaminants every five years.
•	Monitoring by a representative sample of public water systems serving less than or equal to
10,000 people and all systems serving more than 10,000 people.
•	Storing analytical results in a National Contaminant Occurrence Database to support contaminant
occurrence analysis and support regulatory determinations.
Contaminant Candidate List (CCL) and Regulatory Determinations
EPA relies on a science-driven CCL process to identify candidates for possible new drinking water
regulations. The CCL is a list of contaminants that are currently not subject to any proposed or promulgated
national primary drinking water regulations, but are known or anticipated to occur in public water systems
and may occur at levels of potential public health concern (EPA, 2017d). Contaminants listed on the CCL
may require future regulation under the SDWA. The Agency considers health effects and drinking water
occurrence information when placing contaminants on the list and places contaminants on the list that
present the greatest potential public health concern (EPA, 2017d). The CCL is used to prioritize agency
research needs and serves as the primary tool for identifying contaminants to be monitored under EPA's
UCMR program (EPA, 2017c).
EPA published the most recent CCL (CCL 4) on the November 17, 2016 (EPA, 2016c). The CCL 4 includes
97 chemicals or chemical groups and 12 microbial contaminants. The list includes, among others,
chemicals used in commerce, pesticides, biological toxins, disinfection by-products, pharmaceuticals, and
waterborne pathogens. The list is available at https://www.epa.gov/ccl.
EPA later determines whether or not to regulate at least five contaminants from the CCL in a separate
process called Regulatory Determinations. Section 1412(b)(1)(A) of the 1996 SDWA lists three criteria for
making a positive regulatory determination for a CCL contaminant:
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1.	The contaminant may have an adverse health effect.
2.	The contaminant occurs, or is likely to occur, at a level and frequency of public health concern.
3.	A national regulation provides a meaningful opportunity for health risk reduction.
A Regulatory Determination is a formal decision on whether (or not) EPA should initiate a rulemaking
process to develop a regulation for a specific contaminant or group of contaminants (EPA, 2017c). EPA
completed its most recent Regulatory Determination on January 4, 2016. For more information, see
https://www.epa.aov/ccl/basic-information-ccl-and-reaulatorv-determination.
Health Advisories
The SDWA authorizes EPA to produce health advisories (HAs) for unregulated contaminants which provide
information on drinking water contaminants that may cause adverse human health effects (EPA, 20171).
HAs are non-regulatory, non-enforceable, and a way for the Agency to provide technical advice to states,
public health officials, public water systems, and other stakeholders. These documents typically contain the
following information for the contaminant:
•	Physical and chemical properties.
•	Occurrence and environmental fate.
•	Pharmacokinetics.
•	Health effects.
•	Analytical methodologies.
•	Treatment technologies associated with drinking water contamination.
Additionally, HAs may identify drinking water concentrations of the contaminant at which adverse health
effects are not anticipated to occur over a given exposure period (EPA, 2012b). Historically, HAs have
been derived for three reasons: 1.) in response to emergency spills or contamination incidents, 2.) to
provide technical assistance to state and local officials for unregulated contaminants that may have
locally or regionally elevated concentrations, and 3.) in response to a public or stakeholder request for an
HA.
3,1,2.3 Surface Water Treatment Rules
The most recent Surface Water Treatment Rules (SWTRs) were developed with the Stage 1 and Stage 2
Disinfectants and Disinfection Byproducts Rules (DBPRs). These rules are known as the
Microbial/Disinfection Byproduct (M-DBP) cluster and are intended to reduce microbial contaminants in the
water while minimizing the risks posed by disinfectants and disinfection by-products (DBPs).
Microbes such as Giardia and Cryptosporidium, viruses such as hepatitis A virus, and Legionella cause
waterborne diseases and exist in fluctuating concentrations in surface waters (EPA, 2017e). The SWTRs
require filtration and/or disinfection of surface water sources to remove and inactivate harmful microbes.
The SWTRs apply to all public water systems utilizing surface water or groundwater that is under the direct
influence of surface water (GWUDI).
In 1990, EPA's Science Advisory Board, established by Congress as an independent panel of experts, cited
drinking water contamination as one of the most important public health risks (EPA, 2001a). They indicated
that disease-causing microbial contaminants (e.g., bacteria, protozoa, and viruses) pose the greatest
remaining health risk challenge for drinking water suppliers. The 1989 SWTR set MCLGs for Legionella,
Giardia lamblia, and viruses at zero because any exposure to these contaminants presents some level of
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health concern (EPA, 1989a). The 1989 SWTR required all systems using surface water or GWUDI (also
known as Subpart H systems), to achieve at least 99.9 percent (3-log) and 99.99 percent (4-log) removal
and/or inactivation of Giardia and viruses, respectively. Under the SWTR, systems are assumed to meet
these treatment technique requirements if they meet design and operating conditions, turbidity performance
criteria, and CT values (defined as the product of disinfectant residual concentration and the contact time
that the residual is present in the water). Further, systems must maintain a detectable disinfectant residual
throughout the distribution system. The 1989 SWTR does not specifically address Cryptosporidium, a
protozoan organism responsible for an outbreak in Milwaukee, Wl in 1993. To reduce the public health risk
associated with Cryptosporidium in finished water, the Interim Enhanced Surface Water Treatment Rule
(IESWTR) lowered the turbidity standard at Subpart H systems that serve 10,000 or more people to improve
filtration performance (EPA, 1998a). The IESWTR also requires states to conduct sanitary surveys for all
surface water and GWUDI community systems every three years and for noncommunity systems every five
years.
The Long Term 1 Enhanced Surface Water Treatment Rule (LT1ESWTR) extends this requirement to
systems serving fewer than 10,000 persons (EPA, 2002b). The Long Term 2 Enhanced Surface Water
Treatment Rule (LT2ESWTR) requires additional treatment for Cryptosporidium at those surface water or
GWUDI systems considered to have high levels of Cryptosporidium in source waters based on monitoring
results (EPA, 2006b). Those systems must provide for additional reduction of Cryptosporidium in their
source waters based on placement in one of three Cryptosporidium concentration bins, with one additional
bin requiring no extra treatment. Total removal requirements range from 2-log reduction of Cryptosporidium
for sources classified for no additional treatment in Bin 1 (< 0.075 oocysts/L) to 5.5-log for sources classified
as Bin 4 (>3.0 oocysts/L).
Finally, the Filter Backwash Recycling Rule is intended to reduce pathogen concentrations in finished water
by properly managing WTP backwash water and waste streams (EPA, 2001 d).
3,1.2,4 Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rules
(DBPR)
Disinfectants used in water treatment can react with natural organic and inorganic materials in the water
and form potentially harmful by-products. DBPs have been associated with adverse health effects, including
cancer and developmental and reproductive effects (EPA, 2001a). The Stage 1 DBPR sets maximum
residual disinfectant level goals (MRDLGs) and MRDLs for chlorine, chloramine, and chlorine dioxide (EPA,
1998b; EPA, 2001a). It also sets MCLGs for specific trihalomethanes (THMs) and haloacetic acids,
bromate, and chlorate; and MCLs forthe sum concentration of four THMs (total trihalomethanes, orTTHM),
five haloacetic acids (HAA5), bromate, and chlorite. Whereas the Stage 1 Rule bases MCL compliance on
a system-wide average (running annual average) forTTHM and HAA5, the Stage 2 DBPR requires MCL
compliance at each monitoring location (location running annual average) (EPA, 2006a).
The bromate MCL only pertains to systems using ozone and is based on a running annual average of
monitoring results at the entrance to the distribution system. The chlorite MCL only pertains to systems
using chlorine dioxide based on monitoring at the entrance to and within the distribution system. Since short
term exposure to chlorite may impose health risks, daily monitoring for chlorite is required at the entrance
to the distribution system. If any sample exceeds the MCL value, three additional samples must be taken
in the distribution on the following day; if the average of these sample measurements exceeds the MCL,
the system is in violation. The Stage 1 DBPR also sets a treatment technique fortotal organic carbon (TOC)
removal to reduce unregulated DBPs in surface water and GWUDI systems that use conventional
treatment.
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3,1.2,8 Ground Water Rul<
In 2006, EPA published the Ground Water Rule (GWR) to facilitate enhanced protection against microbial
pathogens from fecal contamination in drinking water systems supplied by groundwater sources (EPA,
2006c; EPA, 2017f). The GWR requires sanitary surveys to identify significant deficiencies in water systems
and requires mitigation of these deficiencies. The GWR is a risk-based rule requiring triggered source water
monitoring for fecal contamination indicators if a system observes a positive total coliform sample in the
distribution system (Section 3.1.2.6). It also provides states with the option to require assessment source
water monitoring to target systems that may have higher fecal contamination risks. Also, if the system is
found vulnerable to fecal contamination, then the system must remediate such contamination (e.g.
treatment to achieve at least 4-log or 99.99 percent inactivation or removal of viruses) (EPA, 2017f).
3.1.2.6	Revised Total Coliform Rule (RTCR)
The presence of pathogens in finished drinking water has the potential to result in a public health impact,
including waterborne disease outbreaks. In addition to the aforementioned SWTRs and GWR, EPA also
enacted the Total Coliform Rule (TCR) in 1989 and revised this rule in 2013 (Revised Total Coliform Rule,
RTCR) to address these concerns (EPA, 1989b; EPA, 2013b). The RTCR includes an MCLG of zero for E.
coli because some E. coli organisms are pathogenic, and ingestion of a single pathogen has the potential
to cause disease. The goal of the RTCR is to reduce potential public health threats associated with microbial
contamination. Under the RTCR, each public water system must monitor for total conforms at a
rate proportional to the number of people served (EPA, 2017g). Public water systems are also required to
test for E. coli if they detected total conforms. If specified coliform occurrence frequency levels are
exceeded, it will trigger an investigation and possible corrective action. If the system has not done the
investigation or has not corrected the problem, or if it has the specified levels of E. coli total coliform
occurrence (an MCL violation), then it must notify the public (EPA, 2017g).
3.1.2.7	Lead and Copper Rule
EPA's NPDWRs regulate lead and copper in drinking water at 40 CFR part 141, Subpart I. The Lead and
Copper Rule includes requirements for corrosion control treatment, source water treatment, lead service
line replacement, and public education (EPA, 2007; EPA, 2017h). These requirements are triggered, in
some cases, by lead and copper action levels measured in samples collected at consumers' taps. The
action level for lead is exceeded if the concentration of lead in more than 10 percent of tap samples collected
during any monitoring period is greater than 15 ppb (EPA, 2017h). The action level for copper is exceeded
if the concentration of copper in more than 10 percent of tap samples is greaterthan 1.3 ppm (EPA, 2017h).
The most common source of lead and copper in drinking water is leaching of these metals from the drinking
water distribution system after the treated water has left the drinking water treatment plant. The corrosivity
of the treated water and the presence of lead or copper in distribution systems or premise plumbing both
play an important role in determining the levels of lead and copper that will be present in drinking water. It
is important to note that purified water from DPR systems can be highly aggressive to plumbing materials,
and proper corrosion control may be critical for maintaining the safety of these systems.
3.1.2.8	Source Water <»ments
Protecting water at the source is the first step in the multiple-barrier approach that also includes treatment
for removal of contaminants, monitoring to ensure that health-based standards are met, adequate
infrastructure maintenance, and actions to improve consumer awareness and participation. Source water
is untreated (raw) water from streams, rivers, lakes, or underground aquifers that is used to provide public
drinking water (EPA, 2017r). Some level of water treatment (e.g., filtration, disinfection, corrosion control)
is usually necessary before it is delivered to the customer. Protecting source water from contamination can
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reduce the cost of treatment and the risks to public health (EPA, 2017r). Source water protection is one of
the critical intersections between the CWA and the SDWA, where both Acts serve to protect valuable
drinking water sources.
The 1996 SDWA amendments, section 1453, required all states to receive EPA approval for a source water
assessment program and to execute assessments for all public water system supplies within three years
(SDWA section 300j-13). The program does not specifically dictate nor require implementation of source
water protection measures; but, the assessments help identify potential public health threats to address
through either source water protection or additional treatment. This provision of the SDWA provides an
additional check for the protection of drinking water supplies; i.e. waters that are designated as drinking
water supplies are also protected under the CWA by application of ambient water quality criteria. The
ambient surface water quality criteria under the CWA and source water protection programs under the
SDWA are central to an effective programmatic approach to protecting human health during the
implementation of potable reuse through surface water augmentation.
3,1.2,9 Underground Injection Control Program
The Underground Injection Control (UIC) program under the SDWA is an important part of existing IPR
programs that use injection to implement artificial aquifer recharge (AR) to enhance natural groundwater
supplies (EPA, 2016a). Recharge can occur using man-made conveyances such as infiltration basins or
injection wells. Similarto AR, aquifer storage and recovery (ASR) is a type of AR practiced to both augment
groundwater resources and recover the water for future uses (EPA, 2016a). The type of water injected in
recharge projects can include treated drinking water, surface water, stormwater, and reclaimed water.
Chapter 2 of the 2012 Guidelines provides an extensive discussion of groundwater recharge.
The SDWA authorizes EPA to develop minimum federal regulations for state and tribal UIC programs to
protect underground sources of drinking water (USDW) and prohibits any injection which endangers a
USDW (SDWA section 300h). USDWs are defined as an aquifer, or a part of an aquifer, that is currently
used as a drinking water source or may be used as a drinking water source in the future with these specific
characteristics (40 CFR 144.3):
•	Supplies any public water system, or contains a sufficient quantity of groundwater to supply a
public water system, and currently supplies drinking water for human consumption, or contains
fewer than 10,000 mg/l total dissolved solids (TDS).
•	Is not an exempted aquifer.
The UIC program is overseen by either a state or tribal agency or one of EPA's regional offices, and these
agencies are responsible for regulating the construction, operation, permitting, and closure of injection wells
that place fluids underground for storage or disposal (EPA, 2017s).
All injections require authorization under either general rules or specific permits. Injection well owners and
operators may not site, construct, operate, maintain, convert, plug, abandon, or conduct any other injection
activity that endangers USDWs (EPA, 2016b). The UIC requirements have two purposes (EPA, 2016b):
•	Ensure that injected fluids stay within the well and the intended injection zone.
•	Mandate that fluids that are directly or indirectly injected into a USDW do not cause a public water
system to violate drinking water standards or adversely affect public health.
EPA regulations group injection wells into six "classes" (EPA, 2016b). Classes I - IV and VI include wells
with similar functions, construction, and operating features (EPA, 2016b). This creates consistent technical
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requirements for each well class. Class V wells do not meet the description of any other well class and
include storm water drainage wells, septic system leach fields, and agricultural drainage wells (EPA,
2016b). Class V wells do not necessarily have similar functions, construction, or operating features (EPA,
2016b). Aquifer recharge wells and aquifer storage and recovery wells are regulated as Class V injection
wells and, as such, well owners and operators must submit basic inventory information to the EPA region
or state with primary enforcement authority (primacy) (EPA, 2016a).
Additional recharge well regulations vary between primacy states. As of 2007, nine states require that water
used for ASR injection be potable or treated to national or state drinking water standards or state
groundwater standards (EPA, 2016a). Potable water is defined differently in each state but generally refers
to high-quality water that poses no immediate or long-term health risk when consumed. Some primacy
states allow ASR to use additional types of water, including treated effluent, untreated surface and
groundwater, reclaimed water subject to state recycled water criteria, or "any" injectate (EPA, 2016a). State-
specific regulations do not supersede the prohibition of movement of fluid into a USDW. EPA regulations
provide that "[n]o owner or operator shall construct, operate, maintain, convert, plug, abandon, or conduct
any other injection activity in a manner that allows the movement of fluid containing any contaminant into
USDW, if the presence of that contaminant may cause a violation of any primary drinking water regulation
under 40 CFR part 142 or may otherwise adversely affect the health of persons" (40 CFR 144.12). These
regulations do not specifically stipulate treatment requirements (e.g. filtration, disinfection) for the injected
water, but such treatment may be necessary to protect against the adverse health effects referenced in the
regulation.
3.1.3 Regulatory Considerations for Planned Potable Reuse
While there are some stakeholders who look to EPA to establish additional regulations for potable water
reuse, the CWA and the SDWA already allow for planned potable reuse implementation. Utilities and states
must meet all applicable SDWA and CWA provisions, at a minimum, including the SWTRs, when
implementing planned potable reuse projects. Potable reuse systems should provide water quality
treatment at a level sufficient to ensure public health protection. Examples of approaches designed to
protect public health include California's indirect potable reuse regulatory approach (see Chapters 3 and
5) and EPA's approach in the LT2ESWTR, which requires PWSs with more challenging source waters to
determine additional treatment requirements (EPA, 2006b). In order to ensure adequate public health
protection, potable reuse systems should provide water quality treatment equivalent to or better than that
afforded by first treating the water to meet limits otherwise required by an NPDES permit (i.e., secondary
treatment at a minimum), followed by treatment to meet all applicable SDWA requirements. Some states,
as previously described in the 2012 Guidelines, have already established rules, regulations, or guidance
for IPR project implementation.
The WateReuse Association and National Water Research Institute (NWRI), in cooperation with the
American Water Works Association and Water Environment Federation, supported an Independent
Advisory Panel (IAP) to identify issues to address when developing DPR guidelines that could ultimately
support state rules or regulations. The result of that IAP effort was published as the Framework for Direct
Potable Reuse (NWRI, 2015). This document offers one approach on DPR and may help decision-makers
understand DPR's role in a community's water portfolio. Additionally, EPA development of planned potable
reuse support documents would allow the EPA, states, and stakeholders to work in partnership to achieve
greater progress towards developing locally sustainable water supplies for drought-stricken communities.
Anchoring a potable reuse framework within the existing risk-based human health regulatory structure could
promote higher levels of treatment at municipal WWTPs and clarify treatment and monitoring needs for
potable reuse projects (Soller et al., 2017; Solleretal. 2018).
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3.2 Local Regulatory Approaches
The 2012 Guidelines provided guidance regarding IPR, but only defined the concept of DPR. As of 2012,
only eight states had some IPR guidance, and no states had DPR regulations. As of 2017, multiple states
have addressed potable reuse in their regulations, and some states are developing or evaluating DPR
regulations or guidelines (Table 3-1). For example, in August 2014, the state of North Carolina passed
legislation allowing the use of Type 2 Reclaimed Water as a drinking water supply under certain conditions
(see N.C. Gen. Stat. § 143-355.5). The following two tables highlight regulatory approaches taken in
different states related to potable reuse.
Table 3-1. Number of U.S. states or territories addressing potable water reuse as of 2017 (Updated
from EPA, 2012a)
Category
of Reuse
Description
Number of States with
Policies to Address
Potable Reuse in 2012
Number of States with
Policies to Address
Potable Reuse in 2017
IPR
Augmentation of a drinking water
source (surface or groundwater) with
reclaimed water followed by an
environmental buffer that precedes
normal drinking water treatment.
8 (Arizona, California,
Florida, Hawaii,
Massachusetts,
Pennsylvania, Virginia,
Washington)
14 (Arizona, California, Florida,
Hawaii, Idaho, Massachusetts,
Nevada, North Carolina,
Oklahoma, Oregon,
Pennsylvania, Texas, Virginia,
Washington)
DPR
The introduction of reclaimed water
(with or without retention in an
engineered storage buffer) into a
drinking water treatment plant. This
includes the treatment of reclaimed
water at an Advanced Wastewater
Treatment Facility for direct
distribution.
0
3 (California, North Carolina,
Texas)
Table 3-2. Select U.S. states addressing potable reuse as of 2017
States Types of Potable
Treatment
Highlights
Reuse Addressed
Requirements

¦	12-log virus removal (1 -log virus credit given
per month of subsurface retention time)
¦	10-log Cryptosporidium and Giardia removal
¦	3 or more separate treatment barriers
¦	Each treatment process is granted between
0.5-log and 6-log removal credit
¦	Minimum allowable underground response
time is 2 months
¦	Drinking water MCLs
¦	Action levels for lead and copper
¦	Less than or equal to 10 mg/L total nitrogen
(applies to recycled water effluent or blended
water concentration)
California1
Groundwater
Replenishment Using
Recycled Water via
Surface Spreading
and Subsurface
Applications (Direct
Injection)
Full-Advanced
Treatment for Direct
Injection
Filtration + Disinfection
for Surface Spreading
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States
Types of Potable
Treatment
Highlights

Reuse Addressed
Requirements




¦	TOC < 0.5 mg/L divided by the fraction of
recycled water contribution
¦	< 10 ng/L NDMA
¦	Wastewater management agency must have
industrial pretreatment and pollutant source
control program
Florida2
Groundwater
Recharge to a Potable
Aquifer via Injection
¦	Secondary
¦	Filtration
¦	Disinfection
¦	Multiple barriers
for control of
pathogens and
organics
¦	Pilot testing
required
Injection to groundwater with TDS < 3,000
mg/L:
¦	Primary and secondary drinking water
standards
¦	TSS < 5 mg/L
¦	TOC < 3 mg/L
¦	No detectable total coliforms/100 mL
¦	TOX < 0.2 mg/L
¦	Total N < 10 mg/L
¦	CBODs < 20 mg/L
¦	Secondary
¦	Filtration
¦	Disinfection
Injection to groundwater with TDS between
3,000 -10,000 mg/L:
¦	Primary and secondary drinking water
standards
¦	TSS < 5 mg/L
¦	No detectable total coliforms/100 mL
¦	Total N < 10 mg/L
¦	CBODs < 20 mg/L
Surface Water
Augmentation
¦	Secondary
¦	Filtration
¦	Disinfection
¦	Multiple barriers
for control of
pathogens and
organics
¦	Pilot testing
required
Planned use of reclaimed water to augment
surface water resources which are used or
will be used for public water supplies
¦	Primary and secondary drinking water
standards
¦	TSS < 5 mg/L
¦	TOC < 3 mg/L
¦	No detectable total coliforms/100 mL
¦	TOX < 0.2 mg/L
¦	Total N < 10 mg/L
¦	CBODs < 20 mg/L
North
Carolina3
IPR and DPR
Type 2 reclaimed
water facilities:
¦ Dual disinfection
systems
containing UV
disinfection and
chlorination or
equivalent that
In 2014, Senate Bill 163 was signed into law
(N.C. Gen. Stat. § 143-355.5), allowing for local
water supply systems to combine reclaimed
water with other raw water sources before
treatment if all of the following conditions are
satisfied:
¦ Reclaimed water use is not required for
compliance with flow limitations
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2017 Potable Reuse Compendium Chapter 3 | SDWA and CWA: Opportunities for Water Reuse
States
Types of Potable
Reuse Addressed
Treatment
Requirements
Highlights


can meet
pathogen
reduction
requirements
¦	Reclaimed water and source water are
combined in an impoundment, sized for > 5
days' storage
¦	Impoundment design should ensure mixing
¦	Reclaimed water treated to highest standard
(Type 2)
¦	Average daily flow of reclaimed water into
impoundment is < 20%
¦	Conservation measures are implemented and
maximized
¦	Unbilled leakage is maintained below 15%
¦	Reuse Master Plan
¦	Public Participation
Type 2 Reclaimed Water Effluent Standards
¦	E.coli> log 6 reduction; < 3/100 ml (monthly
geometric mean)
¦	Coliphage > log 5 reduction; < 5/100 ml
(monthly geometric mean)
¦	Clostridium perfringens > log 4 reduction; <
5/100 ml (monthly geometric mean)
¦	BODs ^ 5 mg/L (monthly avg)
¦	TSS < 5 mg/L (monthly avg)
¦	NH3 ^ 1 mg/L (monthly avg)
¦	NTU < 5
Oklahoma4
Category 1A - DPR
N/A
In development stages
Category 1B - I PR
(Surface Water)
Category 1C-IPR
(Groundwater)
Virginia5
IPR
¦	Multiple barrier
approach
¦	Secondary
¦	Filtration
¦	Disinfection
Projects proposed after 1/29/14 require multiple
requirements (the most stringent standard
applies if there is more than one pollutant
standard):
¦ Level 1 standards
0 BODs ^ 10 mg/L (monthly avg)
0 CBODs ^ 8 mg/L (monthly avg)
0 NTU < 2
0 Fecal coliform < 14 colonies/100
mL (monthly geometric mean)
0 E. coli < 11 colonies/100 mL
(monthly geometric mean)
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2017 Potable Reuse Compendium Chapter 3 | SDWA and CWA: Opportunities for Water Reuse
States
Types of Potable
Reuse Addressed
Treatment
Requirements
Highlights



o Enterococci < 11 colonies/100 mL
(monthly geometric mean)
o pH 6-9
o Total residual chlorine < 1 mg/L4
¦	Specific standards based on factors
considered by the State Water Control
Board
¦	Other standards (i.e. - TMDLs)
Nevada6
Reuse Category A+:
IPR via spreading
basins or direct
injection

¦	State adopted NPDWRs
¦	State adopted secondary MCLs
¦	Enteric virus = 12-log reduction
¦	Giardia = 10-log reduction
¦	Cryptosporidium = 10-log reduction
Texas8
IPR and DPR
• Case-by-case
¦	Determined on a case-by-case basis for IPR
and DPR
¦	In DPR, assigned log removal credits do not
include the WWTP, rather they start at the
WWTP effluent
Washington7
Class A reclaimed
water (surface water
augmentation, indirect
and direct
groundwater recharge,
aquifer recovery)
¦	Oxidation
¦	Coagulation
¦	Filtration
¦	Disinfection
Performance Standards:
¦	Disinfection requires 4-log virus removal or
inactivation
¦	BODs ^ 30 mg/L (monthly avg)
¦	CBODs ^ 25 mg/L (monthly avg)
¦	TSS < 30 mg/L (monthly avg)
¦	NTU < 2 (coagulation and filtration) or =< 0.2
(membrane filtration) (monthly avg)
¦	Total Coliform < 2.2 MPN/100 mL g day
median)
¦	Total N < 10 mg/L (monthly average)
pH = 6-9 or 6.5-8.5 (groundwater recharge)
Additional requirements are based on use
Class A+ reclaimed
water (DPR)
¦	Same as Class A
¦	Additional
requirements
determined on
case-by-case
basis
¦ Specific performance standards must be
health based and require state department
of health approval
Class B reclaimed
water (surface water
augmentation, indirect
groundwater recharge)
¦	Oxidation
¦	Disinfection
Performance Standards:
¦	BODs 2 30 mg/L (monthly avg)
¦	CBODs ^ 25 mg/L (monthly avg)
¦	TSS < 30 mg/L (monthly avg)
¦	Total Coliform < 23 MPN/100 mL (7 day median)
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States
Types of Potable
Reuse Addressed
Treatment
Requirements
Highlights



¦ pH = 6-9 or 6.5-8.5 (groundwater recharge)
Additional requirements are based on use
1	See Cal. Code Reg. tit. 22 § 60320.100-60320.230;
http://vwvw.waterboards.ca.gov/drinkinq water/certlic/drinkinqwater/Lawbook.shtml
2	See Fla. Admin. Code 62-610; http://www.dep.state.fl.us/leqal/Rules/wastewater/62-610.pdf
3	See N.C. Gen. Stat. § 143-355.5; 15A N.C. Admin. Code 02U;
http://www.ncleq.net/EnactedLeqislation/Statutes/PDF/BvArticle/Chapter 143/Article 38.pdf;
http://reports.oah.state.nc.us/ncac/title%2015a%20-%20environmental%20quality/chapter%2002%20-
%20environmental%20manaqement/subchapter%20u/subchapter%20u%20rules.pdf
4	See Okla. Admin. Code § 252:656-27 (ODEQ, 2014);
http://www.deq.state.ok.us/wqdnew/wqmac/Proposed2014/RequlatorvPathForwardforlndirectandDirectPotableReuse
ofReclaimedWaterNov2014.pdf; http://www.deq.state.ok.us/rules/656.pdf
5	See 9 Va. Admin. Code §§ 25-740-70, 25-740-90;
https://law.lis.virqinia.gov/admincode/title9/aqencv25/chapter740/section70/;
https://law.lis.virqinia.qov/admincode/title9/aqencv25/chapter740/section90/
6	See Nev. Admin. Code § 445A (revised Dec. 21, 2016); https://www.leq.state.nv.us/Reqister/2016Reqister/R101-
16A.pdf
7	See RCW 90.46; Reclaimed Water (proposed rule Aug. 23, 2017) (to be codified at Wash. Admin. Code § 173-219);
http://apps.leq.wa.qov/RCW/default.aspx?cite=90.46; https://ecoloqv.wa.gov/DOE/files/2e/2e59fa6e-b5ab-4612-
ba13-a56b23ba7b40.pdf
8	See TWDB, 2015 and 2017
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2017 Potable Reuse Compendium
Chapter 4 | Constituents in Potable Reuse Water Sources
CHAPTER 4
Constituents in Potable Reuse Water
Sources
Potable reuse implicates both the Clean Water Act (CWA) and Safe Drinking Water Act (SDWA).
Wastewater effluent must meet, if not exceed the CWA requirements, including National Pollutant
Discharge Elimination Systems (NPDES) requirements. Subsequently, reused water must meet drinking
water treatment requirements under the SDWA, including the National Primary Drinking Water Regulations
(NPDWRs). See Chapter 3 for a more in-depth discussion of the CWA and the SDWA. This chapter
carefully considers the constituents that may be relevant when considering the use of reclaimed water in
community drinking water supplies.
4.1 Constituents in Potable Reuse Water Sources
Potential chemicals and pathogenic microorganisms in water sources need to be carefully studied and
evaluated when considering potable reuse as these can impact human health. This section explores the
constituents of concern in potable reuse water sources (e.g., source water, wastewater, stormwater,
greywater).
4.1.1 Pathogenic Microorganisms in Potable Reuse Water Sources
Microorganisms are abundant in nature and most are not pathogenic to humans. Microorganisms are
present in high concentrations in wastewater in the form of bacteria, viruses, protozoa, and helminths. The
pathogenic microorganisms are those that cause negative human health effects, such as gastrointestinal
illness. The source of primary pathogens in domestic wastewater is primarily feces, and infection typically
occurs through the "fecal-oral" route. Pathogens that are able to survive outside of the host are primarily
transmitted via ingestion or consumption of contaminated water or food, or by inhalation of aerosolized
water containing suspended opportunistic pathogens. Pathogen survival in water, including wastewater,
can depend on a variety of factors, such as: the distance of travel, rate of transport, temperature, exposure
to sunlight, water chemistry, and predation by other organisms. In potable reuse scenarios, most pathogen
exposures pose an acute risk since disease generally presents on the order of hours to days following
exposure. There are some pathogens that pose chronic risks. Table 4-1 presents the infectious dose levels
of various types of pathogens.
Table 4-1. Median infectious dose of waterborne pathogens (Feachem et al., 1983; Messneret al.,
2014, 2016; Teunis et al., 2008)
Pathogenic Organism
Examples
Median Infectious Dose (ID50) Category

Campylobacter

Bacteria
Shigella
~106

Salmonella

Viruses
Hepatitis A
Rotaviruses
Adenoviruses
Noroviruses
<102
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2017 Potable Reuse Compendium
Chapter 4 | Constituents in Potable Reuse Water Sources
Pathogenic Organism
Examples
Median Infectious Dose (ID50) Category
Protozoa
Giardia
Cryptosporidium
<102
Three recent publications compiled peer-reviewed pathogen density and pathogen log removal data in
raw wastewater (Soller et al., 2017; Eftim et al., 2017; Soller et al., 2018). See Table 4-3 for a summary of
pathogen concentrations in raw wastewater.
4.1.2 Chemical Constituents in Potable Reuse Water Sources
Chemicals present in wastewater may be from atmospheric contact, geology, natural products, pesticides,
runoff, or discharges from industrial facilities, amongst other sources (EPA, 2012a). The chemical makeup
of municipal wastewater can vary depending on the activities taking place at the wastewater source. In
domestic wastewater, pharmaceutical^ active substances enter the wastewater stream through human
excretion and improper disposal of medications via toilet flushing. Additionally, pesticides and other
agricultural chemicals have the potential to enter wastewater through stormwater runoff (which may also
include oil, gasoline, road salts). Table 4-2 summarizes categories of chemicals potentially present in
wastewater and gives examples of specific chemicals of interest.
Table 4-2. Chemical substances potentially present in wastewaters (not intended to be a complete
list)
Origin
Categories of Sources of Chemical
Substance
Examples of Specific Chemical
Substances
Industrial
Pesticides, preservatives, flame retardants,
perfluorochemicals, nanoparticles
Plasticizers, heat stabilizers, biocides, epoxy
resins, bleaching chemicals, solvents, dyes,
polymers, hydrocarbons, phthalates, atrazine,
DEET
Domestic
Personal care products, surfactants
Laundry detergent, ammonia, bleach, antifreeze,
lotions, perfume
Human-based
Steroidal hormones, pharmaceutical
residues
Oestradiol, oestrone, testosterone, trimethoprim,
caffeine, ibuprofen, gemfibrozil,
sulfamethoxazole, carbamazepine
Formed during
WW treatment
Disinfection by-products
THMs, HAAs, NDMA, NDEA, aldehydes,
bromate, chlorate
Types of chemicals include inorganic chemicals such as metals, salts, and nutrients, as well as organic
chemicals such as naturally-occurring humic substances, fecal matter, kitchen wastes, liquid detergents,
oils, etc. There are also extremely low concentrations of individual inorganic and organic water constituents
known as "trace chemical constituents," "trace organic chemicals" (TrOCs), or "contaminants of emerging
concern" (CECs). CECs may be from pharmaceuticals, non-prescription drugs, personal care products,
household chemicals, food additives, flame retardants, plasticizers, or biocides (EPA, 2012a). Reported
concentrations of trace constituents in untreated domestic wastewater range from several ng/L to several
hundred |jg/L (Asano et al., 2007). Some of the specific chemicals that may be found in potable reuse water
sources are discussed further below.
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2017 Potable Reuse Compendium
Chapter 4 | Constituents in Potable Reuse Water Sources
4.1.3	Inorganic Chemicals in Potable Reuse Water Sources
Dissolved inorganic constituents present in potable reuse water sources are a combined result of elevated
levels of minerals in existing drinking water sources, the introduction of minerals from domestic water uses
(such as salt-based water softeners), impacts of commercial and industrial discharges, and chemicals used
during water treatment such as sodium hypochlorite and some coagulants (Asano et al., 2007). Typically,
the concentration of dissolved inorganics in wastewater ranges between 200 to 400 mg/L higher than the
associated potable water supply (Khan, 2013).
4.1.4	Organic Chemicals in Potable Reuse Water Sources
Dissolved organic constituents primarily include natural organic matter, soluble microbial products, fecal
matter, kitchen wastes, liquid detergents, oils, grease, consumer products, and low concentrations of an
extensive range of organic chemicals from industrial and domestic sources. Examples include
pharmaceuticals and personal care products (PPCPs), pesticides, preservatives, surfactants, flame
retardants, disinfection by-products (DBPs), and chemicals released by humans such as dietary
compounds and steroidal hormones (Khan, 2013).
Trace organic chemicals (sometimes given the acronym TrOC to avoid confusion with Total Organic Carbon
(TOC)), are generally present at or below |jg/L concentrations (NRC, 2012a), whereas dissolved organic
carbon (DOC) or TOC is typically on the order of mg/L.
4.1.5	Trace Chemical Constituents in Potable Reuse Water Sources
Trace chemical constituents may include pharmaceuticals, non-prescription drugs, personal care products,
household chemicals, food additives, flame retardants, plasticizers, biocides, as well as degradation and
disinfection by-products deriving from these original parent compounds (EPA, 2012a). Trace chemical
constituents can include both inorganic and organic chemicals and are sometimes described by their
associated human health effects, such as endocrine disrupting compounds (EDCs) or pharmaceutical^
active compounds (PhACs).
Pharmaceuticals were detected in U.S. surface waters starting in the 1970s (Hignite and Azarnoff, 1977;
Garrison et al., 1976). In the 1990s, steroid hormones in wastewater were linked to ecological impacts in
impacted surface waters (Daughton and Ternes, 1999; Snyder et al., 2001; Desbrow et al., 1998). There
are now well over 1000 research articles documenting the presence of trace chemical constituents, such
as per- and polyfluoroalkyl substances (PFAS), in aquatic ecosystems impacted by human populations
worldwide (e.g. Wells et al., 2008; 2009; 2010; da Silva et al., 2012; 2013; King et al., 2016; Glassmeyer et
al., 2017; Furlong et al., 2017; Kostich et al., 2017).
4.2 Constituents after Wastewater Treatment
Wastewater treatment does not address all potable reuse constituents of concern. This section highlights
some of the microbial and chemical constituents that remain after wastewater treatment and priorto drinking
water treatment. These remaining constituents may inform drinking water treatment techniques necessary
to produce safe drinking water, as well as design considerations when constructing wastewater treatment
plants.
4.2.1 Microbials after Wastewater Treatment
Wastewater effluent may contain microorganisms including bacteria, viruses, protozoa, and helminths.
Significant concentrations of bacteria can remain during sedimentation, secondary clarification, or
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2017 Potable Reuse Compendium
Chapter 4 | Constituents in Potable Reuse Water Sources
coagulation and flocculation; bacteria are inactivated or destroyed in drinking water applications using
ultraviolet radiation (UV) disinfection or various oxidative processes (e.g., chlorination, ozonation, or
chlorine dioxide) (EPA, 2012a). Enteric viruses are harder to remove than bacteria via coagulation,
sedimentation, or filtration processes due to their small size and are more resistant than bacteria to
disinfectants, especially chlorine (EPA, 2012a; EPA. 2015a). Viruses can be found in secondary effluent in
the range of 10-105 plaque forming units per 100ml (Rose et al., 2004; EPA, 2015a). Protozoa also tend to
be highly resistant to environmental stresses such as heat, freezing, and sunlight; additionally, protozoa
and helminths tend to be resistant to chemical disinfectants such as chlorination (EPA, 2012a).
4.2.2 Chemical Constituents after Wastewater Treatment
Most municipal wastewater treatment plant effluents contain metals, salts, oxyhalides, nutrients, and other
inorganic particles. Oxyhalides (including bromate, chlorite, and chlorate) can form during some wastewater
treatment disinfection processes, particularly those using chlorine or ozone (NRC, 2012a). Therefore,
treatment facility design and operation should consider minimizing oxyhalide formation even though the
NPDES program rarely regulates these parameters. The main forms of nitrogen in wastewater treatment
plant effluent are ammonia, nitrate, nitrite, and organic nitrogen (NRC, 2012a).
Conventional wastewater treatment processes do not remove many PPCPs due to hydrophilic tendencies
at the typical operational pH values (pH 7-8). Some researchers have demonstrated ecological impacts on
local aquatic organisms from trace chemical constituents present in wastewater treatment plant (WWTP)
outfalls, whereas laboratory studies have found that much higher concentrations are necessary to result in
acute impacts. The ecological impacts due to chronic exposure to trace chemical constituents and mixtures
of these compounds are still unknown. This is due to the difficulty in designing studies that control for the
complex set of variables occurring in human impacted aquatic ecosystems. A 2005 study on PhACs showed
that acidic drugs, beta-blockers, and antibiotics remained in conventional WWTPs' effluent at
concentrations between 10 and 10,000 ng/L (Sedlak et al., 2005). The study found that reverse osmosis
(RO), granular activated carbon, and soil aquifer treatment (SAT) were effective removal mechanisms for
many PhACs, but low concentrations of some compounds remained even after advanced treatment (Sedlak
et al., 2005). In a 2014 EPA study, Kostich et al. measured concentrations of 56 active pharmaceutical
ingredients (APIs) in effluent samples from 50 large U.S. WWTPs and found concentrations similar to the
Sedlak study. Researchers further concluded that the risks of human exposure to individual PhACs and
mixtures are generally very low (Kostich et al., 2014).
4.3 Constituents During Water Treatment
By utilizing multiple unit processes in combination with one another, direct potable reuse (DPR) treatment
trains ideally should target the reduction of pathogens to achieve de minimis risk, while providing an
additional measure of redundancy.
EPA researchers and partners' recent publication Direct Potable Reuse Microbial Risk Assessment
Methodology: Sensitivity Analysis and Application to State Log Credit Allocations summarizes indicative
ranges of key pathogens in raw wastewater (influent) and microbial log reductions reported in the relevant
literature for various treatment technologies, replicated here in Table 4-3 (Soller et al, 2018). Generally,
treatment process steps receive log reduction credits during the permitting stage of a potable reuse project,
but this varies from state to state. Log reduction credits are often determined based on the ability to monitor
the reduction through microbial surrogates, such as E. coli orcoliphage. Log reduction credits are a function
of the detection limit of the analytical technique and the concentration present or injected in the feed water
to the unit process. The log removal and/or inactivation rates through secondary wastewater treatment
remain an area of ongoing research.
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Chapter 4 | Constituents in Potable Reuse Water Sources
Table 4-3. Pathogen Densities in Raw Wastewater and Log10 Reductions Across Unit Treatment
Processes (adapted from Solleret al., 2018)


Adenovirus
Min Max
Campylobacter
Min Max
Cryptosporidium
Min Max
Giardia
Min Max
Norovirus
Min Max
Salmonella
Min Max
Raw
Wastewater1
1.75
3.84
2.95
4.60
-0.52
4.38
0.51
4.95
0.02
9.17
0.48
7.38
CSWT2
0.9
3.2
0.6
2
0.7
1.5
0.5
3.3
0.8
3.7
1.3
1.7
Ozonation
BAF
4
0
0.6
4
0.5
2
1
0
0.85
3
0
3.88
5.4
0
1
4
0.5
2
MF
RO
2.4
2.7
4.9
6.5
3
4
9
4
2.7
7
6.5
4
2.7
7
6.5
1.5
2.7
3.3
6.5
3
4
9
UF
4.9

5.6
9
4.4
6
4.7
7.4
4.5

5.6
9
UV Dose
800_mJ/cm2
12 mJ/cm2
6
0
0.5
6
4

6
2
3.5
6
2
3.5
6
0.5
1.5
6
4

CDWT
Cl2
1.5
4
2
5
3
4
4
1.4
0
3.9
0.3
0
4
0.5
1.5
1.1
2
3.9
2
4
3
1	Iog10 units; Adenovirus IU/L, Campylobacter MPN/L, Cryptosporidium oocysts/L, Giardia cysts/L, Norovirus copies/L,
Salmonella PFU/L
2	CSWT= conventional secondary wastewater treatment; BAF = biologically active filtration; MF = microfiltration; RO =
reverse osmosis; UF = ultrafiltration; UV = ultraviolet radiation; CDWT = conventional drinking water treatment
The probabilistic Quantitative Microbial Risk Assessment (QMRA) on DPR treatment train combinations
for recycled water documents the reduction of reference pathogens (norovirus, adenovirus,
Cryptosporidium spp., Giardia iambiia, Campylobacter jejuni, and Salmonella enterica) across each unit
process considered (Soller et al. 2017; Soller et al. 2018). The California State Water Resource Control
Board also recommended using a QMRA approach for the development of uniform DPR water recycling
criteria (California SWRCB, 2016). The Water Environment & Reuse Foundation's (WE&RF's) Establishing
Additional Log Reduction Credits for Wastewater Treatment Plants (WE&RF, est. 2017) will examine
biological treatment processes for protozoa, bacteria, and viruses, and will further document pathogen
removal rates to assign log removal credits to various wastewater treatment steps. The Water Research
Foundation (WRF) report Assessment of Techniques to Evaluate and Demonstrate Safety of Water from
Direct Potable Reuse Treatment Facilities (Rock et al., 2016) provides information on methods to detect
microbial indicators and pathogens.
4.4 Constituents After Drinking Water Treatment
Water treatment plants may produce constituents through the disinfection process. If ammonia levels are
high in the source water and the system uses chloramination, there may be an increased chance for
nitrification to occur in the distribution system, as well as elevated levels of nitrate and nitrite within the
distribution system (EPA, 2002a). Since monitoring for drinking water standards occurs at the distribution
system's point of entry, nitrate and nitrite could occur above the drinking water standard in the distribution
system if appropriate treatment measures to prevent nitrification are not taken.
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Chapter 4 | Constituents in Potable Reuse Water Sources
When using chlorine for disinfection, organic compounds can contribute to the formation of regulated
disinfectant by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs).
Chloramination can result in the formation of N-nitrosodimethylamine (NDMA). Ozone treatment and
advanced oxidation processes can also result in the formation of regulated and unregulated DBPs (Khan,
2013). Disinfection by ultraviolet light (UV), on the other hand, does not result in significant formation of
halogenated DBPs. Typically, high UV doses (800 mJ/cm2) are applied with advanced oxidation processes
to destroy DBPs like NDMA (Gerrity et al., 2015b) and for effective pathogen inactivation.
Additionally, drinking water treatment processes may not capture some trace chemical constituents.
Numerous U.S. sites have detected trace chemical constituents in drinking water supplies and finished
drinking water at very low concentrations (generally on the order of ng/L with rare exceptions in |jg/L (i.e.
lithium)) (Benotti et al., 2009; Furlong et al., 2017). Advances in monitoring technologies have enabled the
quantification of chemicals in water at parts per trillion (ppt) (10-12) and even parts per quadrillion (10-15)
concentrations (EPA, 2012a). The effects of long-term exposure to chemical combinations and their
degradation products at extremely low concentrations is unknown and an area of potential public concern
(WHO, 2012). Based on available information, there is no indication that using highly-treated reclaimed
water for potable purposes poses a greater health risk than using existing water supplies (NRC, 2012a).
Indeed, potable reuse treatment facilities have consistently produced water with lower concentrations of
trace chemicals than most of the Nation's tap water (Snyder, 2014).
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CHAPTER 5
Risk Analysis
Although it is not feasible to completely eliminate risks from conventional treatment or those associated
with reuse, in both cases, it is possible to produce high-quality water that, from a scientific standpoint, does
not present a significant risk. One approach to addressing the risks associated with reclaimed water
includes providing treatment to remove a specified minimum concentration of chemicals or pathogens.
Rigorous methods such as advanced oxidation and reverse osmosis (RO) have frequently been employed
to meet these treatment objectives; additionally, multiple treatment modalities may be incorporated to
provide redundancy in treatment trains.
Individual unit processes in a potable reuse treatment train operate within limitations dictated by source
water quality, removal capacities, maintenance requirements, and failure modes. These limitations as a
whole define the overall capacity of a treatment train to produce water quality that is protective of human
health. Understanding health hazards associated with chemicals and pathogens in source water allows the
design of treatment trains with sufficient capacity, reliability, and redundancy.
Advanced treatment may be required to reach protective levels for key water quality parameters. Some
constituents may be difficult to assess directly, and in some cases, detection methods could be insufficient
to detect levels of viruses and protozoa that could potentially cause disease. In other cases, some
chemicals' toxicological information may be insufficient to define required detection limits and/or to evaluate
concentrations in terms of health risk.
Additional information is needed to identify those parameters, chemical and pathogenic, that place
restrictions on drinking water treatment plant design (e.g. impose a need for advanced oxidation and/or
RO). Risk analysis, which is the nexus of risk assessment and risk management, can inform questions
related to these parameters and other constituents of concern in drinking water. A state or drinking water
utility may want to consider whether to analyze case-specific risks to ensure their systems using indirect or
direct potable water reuse adequately protect consumers and meet all SDWA and relevant state
requirements.
5.1 Risk Assessment
Risk assessment is a formal process for developing qualitative and quantitative information on possible
adverse health effects associated with chemical and pathogen exposure. It involves estimating the nature
and potential for adverse health effects in humans potentially exposed to chemicals or pathogenic
organisms in contaminated environmental media. Risk assessments that yield meaningful water quality
criteria and drive the design of system reliability, system redundancy (multiple barriers), and effective
treatment monitoring can be useful for ensuring public health protection.
For direct potable reuse (DPR), the key information supplied to risk managers from risk assessments
includes evaluation of hazards represented by chemicals and pathogens in drinking water, identification of
uncertainties in estimates of health risk, recognition of gaps in knowledge that may affect confidence in the
risk assessment process, and, often, consideration of concentrations that are protective of public health.
This section discusses some of the tools that can characterize constituents of concern or indicators used
for potable reuse, including standard chemical risk assessment procedures, quantitative microbial risk
assessment, and comparisons with water quality in indirect potable reuse (IPR) situations.
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5.1.1 Quantitative Risk Assessment
In both conventional drinking water treatment systems and in IPR and DPR processes, there are chemicals
and pathogens present in source water that are not fully understood and do not have an available maximum
contaminant level (MCL) or other criteria to inform health impacts and treatment requirements. Using
available toxicological or pathological data, along with extrapolation and uncertainty factors, is one
approach to developing chemical and pathogenic health-based criteria. Quantitative estimates of health
risks are the basis for developing water quality standards such as MCLs. These estimates require toxicity
or infectivity criteria that reflect the quantitative relationship between exposure and adverse health effects.
Chemicals
Quantifying risks from chemical exposure has a long history in the United States. EPA developed guidance
for estimating health risks that follows a four-step process: hazard identification, dose-response
assessment, exposure assessment, and risk characterization (see EPA, 2016d for more information on this
process). EPA's guidance, or a close adaptation of it, is used by other federal agencies and most state
regulatory bodies.
When toxicity criteria are available, cancer risks are estimated in consideration of the potential exposure
and the potential cancer potency of the compound. This calculation generates an estimate of the potential
cancer risks associated with chronic chemical exposure. Risks of 1 in 1 million to 1 in 10,000 (1x10-6 to
1x10-4) have frequently been used as a target risk for setting Agency standards.
Non-carcinogen hazards are estimated by comparing the potential exposure to the estimated safe dose
level (typically referred to as a reference dose, RfD) to determine the potential for adverse health effects to
occur. This comparison of potential chemical exposure and the RfD produces a ratio termed a hazard
quotient (HQ). Values above one suggest that health impacts could occur. The higher the HQ, the greater
the concern for such impacts; but, a HQ is not an estimate of the odds of these impacts occurring.
Pathogens
Health risks related to pathogen exposure can be quantified using a process analogous to that used for
chemicals, known as quantitative microbial risk assessment (QMRA), as defined in Chapter 3. A key issue
for determining pathogen health risks is understanding the pathogen doses needed to cause an infection
or illness. Dose-response relationships are established for some pathogen exposures and potential
occurrences of disease that are relevant to drinking water (Soller et al. 2018). Using QMRA, the potential
health impacts from pathogens (e.g., Cryptosporidium oocysts) in potable supplies can be estimated
quantitatively, which can provide useful information on recommended log removal goals for a potable reuse
treatment train.
As discussed in Soller et al. (2018), "IPR projects in California apply the "12/10/10 Rule", meaning viruses
should be reduced by 12-logs through treatment, and Cryptosporidium and Giardia by 10-logs each (CDPH,
2014; NWRI, 2013). These log-reduction values are intended to achieve a 1 infection per 10,000 people
per year benchmark and were initially derived from the maximum reported densities of culturable enteric
viruses, Giardia iambiia, and Cryptosporidium spp. found in raw sewage (Macler and Regli, 1993; Metcalf
and Eddy, 2003; Sinclair et al., 2015; EPA, 1998b). California is now considering the same microbial log-
reductions for DPR projects (Olivieri et al., 2016), which are also intended to achieve a risk benchmark of
1 infection per 10,000 people per year (NWRI, 2013; 2015; TWDB, 2014)."
However, QMRAs coupling updated pathogen density estimates (Eftim et al., 2017) with more recently
published dose-response relationships (Messner et al., 2014; Messner and Berger, 2016; Van Abel et al.,
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2017; Teunis et al. 2016) suggest higher log-removal values may be necessary to consistently achieve the
1 infection per 10,000 people per year benchmark. For example, Soller et al. (2017; 2018) highlight that
cumulative annual risks are driven by the highest daily pathogen raw wastewater values; this is especially
true for Norovirus and Cryptosporidium spp. Soller et al. (2018) found that enteric viruses should be reduced
by 14-logs, and Cryptosporidium spp. and Giardia by 11-logs to consistently meet the benchmark of 1
infection per 10,000 people per year in 95% of the simulations. On the other hand, the World Health
Organization (WHO) (2017) used a Disability Adjusted Life Year risk assessment approach and found that
enteric viruses should be removed by 9.5-logs, enteric bacteria by 8.5-logs, and enteric protozoa by 8.5-
logs.
Dose-response relationships for other pathogens, such as Legionella, are more complex. This bacterium
can grow readily within home plumbing devices, such as hot water heaters, and within commercial air
conditioning units, hot tubs, and decorative fountains, making it more difficult to quantify in water systems.
Exposure occurs most commonly through inhalation rather than ingestion, further complicating dose-
response relationships. Exposure and associated pathogen risk are important issues; but, monitoring
disease-causing agents and disease incidence is quite difficult. This difficulty is due to a number of factors:
die-off and replication of organisms in finished and wastewater effluent/receiving water, inability to
distinguish viable and non-viable agents (for some methods), differences in human sensitivity, large
numbers of serotypes and strains with differing infectivity, sensitivity of sampling methods, and the difficulty
in tracking disease incidence within communities. Also, many pathogens are detected using culture
methods that may not yield results until long after the exposure has occurred.
In some cases, the use of well-studied indicator organisms might help circumvent some of these
complications. As an example, Clostridium spp. might be used to estimate the survival of protozoan
pathogens Cryptosporidium and Giardia. Spores of these bacteria are relatively resistant to treatment; their
survival during drinking water treatment may be similar to Cryptosporidium oocysts and Giardia cysts
survival. Thus, the more easily monitored bacterium might be a surrogate for survival of the two protozoa.
Typically, titers of protozoan oocysts and cysts are too low to be directly monitored to indicate treatment
effectiveness. Rather, EPA relies on the measurement of engineering process control parameters such as
turbidity and CT values to inform treatment effectiveness.
5.1.2 Alternative Risk Assessment Methods
Alternative risk assessment methods are available that take a broader approach to evaluating risks than
the previously described quantitative assessments. These methods, both qualitative and quantitative, are
described below and may be particularly useful for potable reuse evaluation.
8,1.2.1 Relative Risk Assessment
One qualitative means of addressing the risks posed by chemicals and pathogens in wastewater effluent is
to compare water quality across a range of planned IPR, de facto reuse, and DPR cases. Where drinking
water complies with drinking water standards, based on studies or long-term observation, recycled water
of similar or better quality can adequately protect human health. Under this approach, a similar water quality
could indicate the safety of the recycled water supply rather than defining specific limits for additional water
quality parameters (NRC 2012a).
For example, the Texas Water Development Board (TWDB) recently produced a resource document that
contains a quantitative relative risk assessment (QRRA) comparing two raw surface water sources and two
wastewater treatment effluents after disinfection and filtering (TWDB, 2015). From a health risk standpoint,
as defined by the QRRA, water quality from the two raw sources did not differ substantially from the
wastewater effluents' water quality. That is, differences noted in various water quality parameters did not
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translate into substantive differences in possible health impacts. The Texas Water Development Board
(TWDB) QRRA does not emphasize a comparison of IPR to DPR or a comparison of de facto reuse to
DPR. However, the study approach does make some appropriate comparisons for a limited number of
cases of raw water and treated effluent.
8.1.2.2	Probabilistic	lent
A more rigorous quantitative approach to risk assessment recognizes that, in some cases, health risks are
best understood using probabilistic (stochastic) risk assessment. Probabilistic methods use distributions
instead of point estimates to define inputs to MCLs, treatment technique requirements, or equivalent criteria,
and produce a range of target concentrations or titers that could be health protective.
Probabilistic risk assessments use the same methods described previously to arrive at a range of risk
estimates. This range will provide a more complete assessment of possible health impacts. For instance,
deterministic risk assessments typically provide a conservative estimate of exposure levels and associated
potential health impacts. A probabilistic analysis may show that such risks are atypical and may allow
flexibility in the design of treatment methods based on the site-specific characterization of DPR designated
wastewater effluent.
In addition, a probabilistic model can help set reasonable bounds for exposure and target pathogen
densities in drinking water. This approach can further differentiate input parameters to risk calculations that
are most critical for defining health risk. This information is important for designing treatment methods that
specifically address key factors in reducing exposure and risk to consumers.
Finally, probabilistic risk assessment can be coupled with similar treatment train assessments to provide
an overall assessment of water quality in finished water. As mentioned in Chapters 3 and 4, a study
conducted a QMRA to evaluate microbial risks associated with DPR treatment trains, expanding on a
previously published statistical approach suggested by Haas and Trussell (1998) and demonstrated by
Olivieri et al. (1999) (Soller et al., 2017). This approach was the first quantitative evaluation of the
microbial risks associated with various multi-barrier DPR treatment strategies. More recent sophisticated
approaches are discussed in Evaluation of microbiological risks associated with direct potable reuse
(Soller et al., 2017) and Direct potable reuse microbial risk assessment methodology: sensitivity
analysis and application to State log credit allocations (Soller et al. 2018).
8.1.2.3	Other Methods
Computational toxicology attempts to use the totality of in vitro and in vivo data available in the toxicological
literature to predict some of the characteristics of chemicals that are not well-studied or even new chemicals
as a first step in safety evaluation. This field is still developing and has not yet been used to address
potential concerns associated with water reuse. The field is likely to become increasingly important to all
areas of toxicology in the coming years and may represent a viable means to develop toxicity criteria for
unregulated chemicals.
5.2 Risk Management
Risk analysis uses the information from the risk assessment, along with policy and legal requirements, to
inform decision-making; if risk reduction measures are needed, then any necessary control options are
selected and monitored forthe protection of public health (Asano et al., 2007). This latter process is the risk
management component of the analysis.
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Risk assessment can provide information on health risks associated with reuse into the process of effective
treatment design. This information includes target chemical or pathogen concentrations/titers that can
protect human health and uncertainties in these targets that require consideration in decisions on how to
manage health risks. Risk management is the process of deciding how best to address potential health
risks. It requires consideration of legal, economic, and behavioral factors, as well as the ecological and
human health and welfare effects of each decision/management alternative. Management may consider
regulatory and non-regulatory responses to protect public health. An example of a risk management action
includes determining appropriate discharge levels for a river that feeds into a drinking water supply. Thus,
the difference between risk assessment and risk management is that risk management is the action taken
based on consideration of the risk assessment; EPA Risk Characterization Handbook (EPA, 2000b)
describes the factors considered:
1.	Scientific factors provide the basis for the risk assessment, including information drawn from
toxicology, chemistry, epidemiology, ecology, and statistics. Factors of age, sex, race, etc. fall
into this category.
2.	Economic factors inform the manager on the cost of risks and the benefits of reducing them, the
costs of risk mitigation or remediation options, and the distributional effects.
3.	Laws and legal decisions are factors that define the basis for the Agency's risk assessments,
management decisions, and, in some instances, the schedule, level or methods for risk reduction.
4.	Social factors, such as income level, ethnic background, community values, land use, zoning,
availability of health care, lifestyle, prevalence of underlying health conditions, and psychological
condition, may affect exposure to and/or susceptibility of individuals or groups to a particular
stressor, leading to greater health risk.
5.	Technological factors include the feasibility, impacts, and range of risk management options.
6.	Political factors are based on the interactions among branches of the Federal government, with
other Federal, state, and local government entities, and even with foreign governments; these
may range from practices defined by Agency policy and political administrations through inquiries
from members of Congress, special interest groups, or concerned citizens.
7.	Public values reflect the broad attitudes of society about environmental risks and risk
management.
5.2.1 Risk Reduction Concepts and Management
In addition to water quality criteria that are anchored in human health risk assessment, there is ongoing
work to address operational risks while providing treatment to achieve reuse water quality that is protective
ofthe consumer. A WateReuse Research Foundation (WRRF) study titled Risk Reduction for Direct Potable
Reuse reviewed the development of an operational risk assessment framework for practical public health
protection that employed a cost-effective approach specifically relating to DPR (WRRF, 2014a). This
operational risk framework applies for both individual unit processes and from an overall system standpoint
through four steps; Figure 5-1 illustrates these steps (WRRF, 2014a). The four risk reduction concepts
central to ensuring safety in potable reuse schemes include multiple barriers, system reliability, system
redundancy, and process coupling.
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Chapters | Risk Analysis
Multiple Barrier
Systems
System
Redundancy
Risk
Mitigation
Concepts
Process
Coupling
System
Reliability
Figure 5-1. Risk mitigation concepts in potable reuse schemes (adapted from WRRF, 2014a)
5.2.1.1 Multiple Barrier Systems
Multiple barrier systems are a component of potable reuse schemes because they provide several
individual processes capable of stopping the flow of pathogenic organisms and chemical substances into
treated effluent water. In a multiple barrier scenario, no single treatment step is responsible for meeting
target effluent requirements; instead, each step is partially or completely redundant of another (WRRF,
2014a). Design plans incorporate multiple barriers into the treatment scheme: monitoring at multiple and
various points of the treatment process, real-time or near real-time monitoring, operator certification,
training, a combination of treatment steps, and wastewater effluent control programs that strive to limit the
amount of toxic substances entering the waste stream prior to wastewater treatment. The purpose of
multiple barriers is to decrease the probability of process failure by adding units of reliability and redundancy
to the treatment scheme; this ensures that if one step of the process fails, another treatment unit will reliably
provide public health protection (Khan, 2013). Regulatory agencies employ an approach called log removal
value (LRV) or log removal credit (LRC) to verify the functionality of multiple barriers for pathogen control.
Regulatory agencies grant LRVs based on pathogen removal and/or inactivation knowledge of the
individual unit treatment process (Khan, 2013). The LRVs required to achieve effluent targets, as set by
regulation or permitting mechanism, are calculated and compared to actual treatment results for validation
(Khan, 2013). The California Division of Drinking Water (DDW), for example, controls pathogens and forces
multi-barrier design in groundwater replenishment reuse systems by requiring that the recycled municipal
wastewater achieves at least 12-log enteric virus reduction, 10-log Cryptosporidium oocyst reduction, and
10-log Giardia cyst reduction (see Cal. Code Reg. tit. 22 § 60320.108, 60320.208). California DDW requires
at least three individual treatment processes in the treatment works, and each step is credited with a
maximum of 6-log reduction (see Cal. Code Reg. tit. 22 § 60320.108, 60320.208). The purpose of the
maximum log removal and/or inactivation credit value is to ensure that reuse projects are designing systems
that achieve de minimis risk levels utilizing the multiple barrier approach.
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8,2.1,2 System and Process Reliah
Some of the earliest guidance on process reliability was published by EPA in 1974 in Design Criteria for
Mechanical, Electric, and Fluid System and Component Reliability (EPA, 1974). The document was meant
to supplement the Federal Guidelines for Design, Operation, and Maintenance of Wastewater Treatment
Facilities by establishing minimum practices of reliability for mechanical, electric, and fluid systems and
components. At the time of publication, there was a great deal of federal funding available for new
construction and wastewater treatment plant (WWTP) upgrades, and the design criteria under this guidance
document was often a requirement for obtaining federal financial assistance, including grants (EPA, 1974).
EPA's document defined reliability:
"A measurement of the ability of a component or system to perform its designated function without
failure."
This definition has been readily used by many other technical documents. It is also important to note that
the reliability concept applies not only to the system, but also individual system components. The
wastewater system includes the main wastewater treatment as well as the solids handling system and other
auxiliary systems. A component is a single piece of equipment that performs a specific function; in this
context, a component could be an entire process or may be a single piece of equipment, e.g., a pump.
Extending this concept of reliability to potable reuse treatment trains will likely have a positive effect on
public perception, because consumers must trust that the system's performance protects public health
(Asano et al., 2007). Utilizing extensive monitoring techniques within the potable reuse scheme is one way
to demonstrate that the process is performing reliably. The evaluation of reliability in a system is done
through risk assessment. There are several factors that may impact the reliability of a system including
wastewater quality and its fluctuations, variation of both biological and advanced treatment processes, the
level of automation and type of equipment, the effectiveness of employed monitoring techniques, and the
accessibility of back-up materials such as equipment replacements and connections to power supplies
(Asano et al., 2007). Additionally, operator reliability includes the level of awareness, skills, and knowledge
of the system to ensure a high degree of safety in the potable reuse scheme (Khan, 2013).
As an example from another industry, aviation and space flight is a high-risk industry and, as such, places
a large emphasis on the "fail-safe design" principle. Fail-safe design means that if a failure or combination
of failures were to occur, the result would not be catastrophic (WRRF, 2014a). The aviation industry uses
a concept called "hours-to-failure" to classify the integrity of a certain structural element by estimating the
time of use in hours before a deficiency occurs that results in decreased strength (WRRF, 2014a). This
concept could be applied to DPR, such as in the integrity testing of an RO system. Given that systems
inevitably have failures within their lifetime, there are fail-safe design principles that apply following a system
failure. These include approaches such as Hazard Analysis and Critical Control Points (HACCP), which
gives an assessment of points within the system where impactful failures could occur (WRRF, 2014a). The
International Space Station (ISS) water recycling system (WRS) serves as an example of a fail-safe design
within the space flight industry (EPA, 2012a). The WRS has treated urine and humidity condensate to
potable water quality for astronauts to consume since 2008 (EPA, 2012a). Given that the WRS is the sole
source of water in outer space, the design must exemplify robustness, require minimal maintenance, and
guarantee high-quality effluent. The WRS system incorporates methods that operate relatively independent
of one another, meaning one component of the treatment process could malfunction without being
detrimental to the end-product. This dynamic is known as being "loosely coupled" (WRRF, 2014a). Although
it is inappropriate to apply the specific ISS WRS system to DPR, the fundamental goal remains the same;
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systems providing potable water to the public should be designed to be fail-safe, meaning they produce
water that, is safe for public consumption and meets target effluent, requirements.
5.2.1.3 System Redundancy
Redundancy is one method of ensuring system reliability. Redundancy in its simplistic form refers to the
use of "backup" treatment methods should a given treatment method malfunction or underperform (WRRF,
2014a). Redundancy in potable reuse schemes is crucial because water is continuously distributed.
Continuous operation and source water production requires a mechanism to produce high-quality water,
even in the event, of mechanical or structural failures, servicing of equipment, or a power failure (Asano et
al„ 2007).
This concept of system redundancy is not new to the water and wastewater treatment industry. While there
are not federally mandated system redundancy requirements, state and/or local permitting agencies have
the authority to implement rules, regulations, or guidelines with respect to facility design. And, in fact, most
states do have some form of system redundancy guidance that is evaluated during plans review for facility
permitting. The status of U.S. states with respect to redundancy guidance, as of 2003, is provided in Figure
5-2; a Water Environment Research Foundation study gathered this information to document efficient
redundancy design practices so that WWTPs could optimize treatment for efficiency.
'ISA
^ State or Provincial Redundancy Regulations in place
Q J State or Provincial Redundancy Recommended Guidelines or Standards
Regional/Local Redundancy Regulations
^ Regional/Local Redundancy Recommended Guidelines or Standards
Figure 5-2. States with redundancy regulations or requirements (WERF, 2003)
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8,2.1,4 Process Coupling
Process coupling is important to potable reuse schemes because it characterizes the dependency of one
unit process on an upstream process (WRRF, 2014a). Process coupling ranges from loose to tight, where
tightly coupled systems tend to operate highly dependent on another process. There are some negative
effects found within tightly coupled systems: difficulty of intervention to mitigate local process failures,
explicit design regarding buffers and equipment replacements, and very specific procedures to achieve
effluent targets - where a deviation from the ideal procedure could result in global system failure (WRRF,
2014a). Potable reuse and most engineered systems favor loosely coupled systems.
5,2,2 Risk Analysis Framework
The risk analysis framework utilizes the concepts discussed above to generate methods for identifying,
characterizing, and mitigating human health risks associated with potable reuse. This approach already
accounts for the fact that in many scenarios, treated wastewater effluent is returned to the environment and
is regulated under the Clean Water Act (CWA), which uses a risk-based approach to establish discharge
standards. Further, EPA already establishes standards for drinking water that are anchored in human health
risk assessment. Utilizing a similar risk approach is appropriate when evaluating the potential health risks
associated with drinking water supplies originating from wastewater or wastewater effluent.
In addition to extending the approaches used by Solleret al. (2017; 2018), TWDB (2015), or WHO (2017)
to more DPR projects, it is also important to consider opportunities for DPR approaches to improve the
quality of the source water for drinking water supplies. By applying more consistent controls on the quality
of wastewater effluent used in DPR, these systems have the potential to improve the overall safety of
drinking water provided to the public.
Efforts are being expended to modify and refine risk frameworks for evaluating health impacts of potable
reuse. Additional work in this area is expected in the near future from the EPA, the Water Environment
Federation (WEF) and the Water Environment and Reuse Foundation (WE&RF), all of which are interested
in examining the relative health risks associated with different source waters, including systems using
planned IPR, de facto reuse, and DPR. Risk analysis in the evaluation of water reuse is evolving rapidly
and is likely to undergo further modification and refinement in the next several years.
5.3 Summary
Risk analysis for potable reuse schemes consists of an initial assessment of health hazards associated
with the source water, followed by a risk management phase where treatment is designed to protect
consumers from both acute and chronic illnesses.
A comprehensive risk management framework for DPR still awaits definition and development. Since
potable reuse, including limited DPR, is already occurring and will increasingly be an important potential
solution for community water resource needs, effective risk management strategies will continue to be
critical as potable reuse projects advance.
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Chapter 6 | Treatment Technologies for Potable Reuse
CHAPTER 6
Treatment Technologies for Potable Reuse
6.1 Overview: Five Overall Treatment Objectives for Potable Reuse
The purpose of this chapter is to provide an overview of individual unit processes used in advanced
wastewater treatment facilities (AWTFs) for potable water treatment. An AWTF employs advanced
wastewater treatment (extending beyond secondary treatment) for direct and indirect potable reuse
applications. Individual unit processes are assembled in a range of combinations to achieve water quality
appropriate for potable reuse, as described in Chapter 7 of this document. It is important to note that potable
reuse facilities rely on upstream controls including rigorous source control programs (Chapter 8) and
effective treatment of raw wastewater at a wastewater treatment plant (WWTP). After treatment in an
AWTF, the water may be sent to an environmental or engineered buffer (Chapter 9), or to a drinking water
treatment plant (WTP). Depending on the type of environmental buffer employed, the water may or may
not undergo additional treatment after extraction.
There are five main objectives for AWTFs: removing suspended solids, reducing dissolved chemicals,
disinfection, water stabilization, and producing water with satisfactory aesthetics (Table 6-1) (Khan, 2013).
Table 6-1. Overall treatment objectives and corresponding unit processes
Overall Treatment Objectives
Processes to Accomplish Treatment Objectives
Removal of Suspended Solids
•	Coagulation
•	Flocculation
•	Sedimentation
•	Media filtration
•	Microfiltration (MF)
•	Ultrafiltration (UF)
Reducing the Concentration of Dissolved Chemicals
•	Reverse osmosis (RO)
•	Electrodialysis (ED)
•	Electrodialysis reversal (EDR)
•	Nanofiltration (NF)
•	Granular activated carbon (GAC)
•	Ion exchange
•	Biologically Active Filtration (BAF)
Disinfection and Removal of Trace Organic Compounds
•	Ultraviolet disinfection (UV)
•	Chlorine/chloramines
•	Peracetic acid (PAA)
•	Pasteurization
•	Ozone
•	Chlorine dioxide;
•	Advanced oxidation processes (UV/H202,
03/H202, UV/CI2) (AOP)
Stabilization
•	Sodium hydroxide
•	Lime stabilization
•	Calcium chloride
•	Blending
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Overall Treatment Objectives
Processes to Accomplish Treatment Objectives
Aesthetics (taste, odor, and color control) *
•	03/Biologically Activated Carbon (BAC)
•	MF/RO
* Taste and odor control and color removal does not necessarily require separate treatment processes in advanced
wastewater treatment schemes. For example: 03/GAC or BAC and MF, RO typically address these issues.
6.2 Removal of Suspended Solids
AWTFs are responsible for further purifying treated effluent from conventional wastewater treatment. The
conventional wastewater treatment process does not remove all suspended solids (Asano et al., 2007;
Khan, 2013). Suspended solids, such as bacteria, viruses, and protozoan cysts and oocysts, can be a
threat to human health if present in treated effluent (Khan, 2013). Additionally, the presence of particulates
can negatively impact the performance of downstream treatment processes such as reverse osmosis (RO)
and disinfection. Filtration capabilities with media filters are a function of the operating conditions, design
conditions, and source water quality, and may demonstrate large variations in treatment effectiveness from
changes in flow rate, feed water quality, or chemical dosing. In contrast, filtration capabilities with
membranes are primarily a function of the membrane's pore size. Commercially available microfiltration
(MF) and ultrafiltration (UF) membranes consistently remove large pathogens such as protozoan cysts;
smaller pathogens such as viruses and bacteria require either smaller pore sizes (such as in nanofiltration
(NF) or RO membranes) or adsorption to larger particles which may subsequently be removed (EPA,
2012a). Sections 6.2 - 6.4 describe treatment processes that provide the removal of particulates, including
pathogens, and include media filtration, MF, and UF. The distinguishing characteristic of these different
types of filtration is the size of particles that each technology can remove, as shown in Figure 6-1.
"1
Micrometers
{Log Scale)
^ ST Micros copo ^ Scanning Electron Mici
roscope ^ 0
iptlcal Microscope
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6.2.1	Media Filtration
Sand and media filtration are examples of particle filtration through porous beds of granular
media by gravity or pressure differentials (EPA, 2012a; Khan, 2013). Particle removal in potable reuse
treatment trains serves dual purposes. First, the removal of solids removes microbial agents including
pathogens and those associated with particulates, colloids, or organics. Secondly, removal of particles
improves the effluent quality for disinfection and other subsequent treatment processes. Lower
concentrations of organics and other particulates can reduce the demand for chemical oxidants in
disinfection; additionally, lower turbidities can improve UV disinfection by increasing the UV transmittance
and allowing pathogen removal that otherwise may be shielded from UV light. There are two general
mechanisms for particle removal through media filtration: physical adsorption and size exclusion. Physical
adsorption occurs when smaller particles and pathogens adsorb to the surface of larger particles (filter
media) and are subsequently removed. Size exclusion occurs when suspended solids are larger than the
open spaces in the filter media and are physically excluded at the media surface (EPA, 2012a; Khan, 2013).
Depth filtration is effective through physical adsorption processes and most commonly utilizes several feet
of packed sand, anthracite, garnet, or other non-compressible media as the filter media (EPA, 2012a). The
effective media size for non-compressible media filters ranges from 0.4 and 2.0 mm in average diameter
(EPA, 2012a). Depth filters can contain one or more filter media types at specified depths. Some examples
of media filters are slow sand filters, monomedia rapid sand filters, and multi-media filters containing
anthracite, sand, and/or gravel (AWWA, 2011a). Depth filtration can also utilize compressible synthetic
media (EPA, 2012a). Media filtration generally relies on coagulation, flocculation, and settling to increase
contaminant particle size and improve filterability. For this reason, removal effectiveness is highly
dependent on operating conditions and the feed water quality. Rapid changes in flow or feed water quality
can result in high levels of particulate breakthrough in a media filter due to temporary non-optimal coagulant
doses.
6.2.2	Microfiltration and Ultrafiltration
Microporous membrane filtration, such as MF and UF, began being used for large scale municipal water
treatment in the early 1990s (Yoo et al., 1995) and was adapted for use in wastewater treatment later that
decade (Cote et al., 2012). In potable reuse applications, membrane filtration processes can be used as
pretreatment to RO to mitigate fouling or clogging of the RO membrane (Wetterau et al., 2013).
A membrane is a thin porous polymer film or a ceramic structure separating two phases that act as a
selective barrier to the transport of matter (EPA, 2012a). Polymeric membrane filters are commonly made
from one of three materials:
•	Polypropylene.
•	Polyvinylidene fluoride.
•	Polysulfone and polyethersulfone.
Each material has different advantages and challenges, but all polymeric membranes run at least some
risk of membrane breakage, which compromises the effectiveness of the membrane. Ceramic membranes
offer an alternative without the risk of breakage, but they have not seen widespread use. Additionally, costs
are considerably higher than polymeric membranes, and they may not have an established direct integrity
testing method to receive pathogen credit.
Membrane filters function primarily by size exclusion, achieving near complete removal of all contaminants
greater than the nominal pore size. As such, membrane filters typically achieve little-to-no removal of
dissolved solids and other contaminants smaller than the nominal pore size. Unlike with media filters,
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operating conditions, such as flow rate, feed water quality, or filtration run length impact the removal
effectiveness of a membrane filter. While membrane filters can remove dissolved organic material when
used in conjunction with coagulation or powdered activated carbon (PAC) (AWWA Subcommittee, 2008),
most membrane filtration plants (particularly those in the United States) utilize filtration without coagulant
or PAC, allowing dissolved organic constituents to pass through unchanged. "MF membranes have a
nominal pore size between 0.1 jjm and 0.2 jjm," allowing them to achieve near complete removal of all
suspended solids, protozoa, and bacteria, with limited removal of viruses (CORPUD, 2014). "UF
membranes have a nominal pore size between 0.01 jjm and 0.08 jjm," achieving significantly higher
removal of viruses, although not all viruses (CORPUD, 2014). Neither type of membrane achieves
significant removal of dissolved organic matter, nor any measurable impact on total dissolved solids (TDS)
(AWWA, 2005).
"For both UF and MF systems, membrane geometry typically [consists] of hollow fiber membranes, where
several hollow fibers are wrapped in a tubular formation, with filtration occurring through the walls of the
fibers" (CORPUD, 2014). MF and UF systems most commonly use an outside-in operation, where the
influent water goes from outside the membrane, through the membrane, into the small hollow fibers, and
finally moves to downstream processes (CORPUD, 2014). "The suspended solids and pathogens remain
on the outside of the membrane where they are then backwashed to waste" (CORPUD, 2014). "There are
a few inside-out membrane filtration systems," "including the world's largest membrane-based reuse facility
in Kuwait" (CORPUD, 2014). MF and UF membranes for municipal use are most commonly configured as
hollow fibers that are packaged into modules containing 4,000 to 20,000 individual membrane fibers, and
range from 0.5 to 2 meters in length and 0.5 to 2 mm in diameter (Khan, 2013). The substances that do not
pass through the filters are periodically backwashed from the membrane modules and transported to waste,
or returned upstream to the wastewater treatment plant.
Both MF and UF systems contain a backwash system and a chemical clean-in-place (CIP) system, with
chemical cleanings needed periodically (roughly once per month) to improve plant efficiency and reverse
membrane fouling (CORPUD, 2014). "The CIP systems typically clean the membranes about once a month
if the influent water is relatively clean[; but,] some reuse facilities utilize chemical cleanings on a more
frequent basis" (CORPUD, 2014). Water quality impacts CIP periods: it occurs more frequently in "waters
with high organic content, high microbial presence, or high coagulant doses, and less frequently in higher
quality source waters, such as wastewaters [that use] full nitrification" (CORPUD, 2014). For example, the
Orange County Groundwater Recharge System in California has a "typical cleaning interval of 14-21 days
when treating secondary effluent with only partial nitrification" (Figure 6-2 and Figure 6-3 show the
submerged MF and RO membranes at OCGWR, respectively) (CORPUD, 2014; see Appendix A).
Generally, CIP systems "apply a combination of acid and sodium hypochlorite to the membranes, coupled
with an air scour as necessary, and proprietary detergents [on occasion]" (CORPUD, 2014). Some
manufacturers use sodium hydroxide as a CIP chemical (CORPUD, 2014).
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Pretreatrnent for membrane filtration is used primarily to prevent fouling and membrane damage, rather
than to enhance the filtration process. Automatic strainers, with slot or screen sizes between 100 and 500
microns, are used to remove large particulates that could damage polymeric membranes or plug up the
filter modules. In wastewater, it is also common to maintain a continuous chlorine or chloramine
concentration in the feed water to prevent biofouling; but, this is not essential if a sufficiently low membrane
flux (or filtration rate) is maintained and the membranes are chemically cleaned and backwashed on a
frequent basis. Membrane filters can treat either settled secondary effluent in a tertiary application or mixed
liquor in a membrane bioreactor.
Membrane filtration requires a driving force for water to pass through. There are two general configurations
for membranes: submerged and pressurized (CORPUD, 2014). Membranes in submerged systems are
"suspended in a basin, and the feed water is at atmospheric pressure;" a pump adds vacuum pressure on
the membrane's filtrate side (CORPUD, 2014). "Pressurized systems typically use pumps to apply a trans-
membrane pressure to the feed, [and] the filtrate is at roughly atmospheric pressure" (CORPUD, 2014).
The pressure difference generated across the membranes in submerged and pressurized configurations
drives the filtration process and suspended solid and pathogen removal (CORPUD, 2014). Historically,
submerged systems were more common for large facilities (>10 million gallons per day (MGD)), while
pressurized systems were more common with smaller facilities. This has changed in recent years, and both
types of systems can be seen in various sized plants.
6.3 Reducing the Concentration of Dissolved Chemicals
Chapter 4 describes trace chemical constituents potentially present in raw wastewater. Unit processes that
achieve degradation and/or removal of dissolved chemicals include RO, electrodialysis (ED), electrodialysis
reversal (EDR), NF, granular activated carbon (GAC), ion exchange, and biologically active filtration (BAF).
These treatment technologies are described below.
6.3.1 Reverse Osmosis
RO is a physical separation process in which feed water is forced through a semi-permeable membrane
using a pressure gradient to separate permeate from a concentrated reject (concentrate). In RO, the feed
Figure 6-2. Submerged MF membranes at OCGWR
Figure 6-3. RO system at OCGWR
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water must be pressurized to exceed the osmotic pressure difference between the feed and permeate,
while providing additional driving pressure to overcome hydraulic losses of water passing through
the membrane material. RO is used extensively for the desalination of seawater and brackish
groundwater; potable reuse can also take advantage of RO because of its ability to effectively remove
pathogens, dissolved chemical substances, total organic carbon (TOC), trace organic compounds, and
TDS (Wetterau et al., 2011). The RO membranes most commonly used in drinking water treatment today
are composed of a thin film composite, which includes a thicker support structure and a thin membrane
skin. Two flat sheet membranes are glued together at their edges, with the membrane skins facing out and
a permeate spacer mesh between the membrane sheets, creating a membrane envelope. Multiple
envelopes are then rolled into a spiral wound configuration, with feed spacer meshes separating each
envelope, creating an individual membrane module or element. Multiple elements (typically six to eight) are
placed in series within a longer pressure vessel and multiple vessels are then banked in parallel and in
series to create a treatment skid (AWWA, 2007).
There are five components to an RO system:
1.	A high-pressure pump, which is used to increase the pressure in the feed water to overcome
osmotic force and pass permeate through the RO membranes.
2.	Multiple membrane modules (typically six to eight), which are installed in series within cylindrical
pressure vessels. Sets of pressure vessels are often also placed in series to create multiple
stages of treatment, with the concentrate from the first stage treated by the second, increasing
the amount of product water that can be recovered by the system.
3.	Membrane modules, which are generally purchased in a spiral wound configuration containing
multiple membrane envelopes, utilizes a feed/concentrate channel on the outside of the envelope
and a permeate channel on the inside. Water passing through the semi-permeable membrane to
the inside of the envelope becomes the treated permeate and is collected in a central permeate
tube.
4.	Permeate piping, which collects treated water from the permeate tubes inside the membrane
modules and conveys the permeate from the RO system.
5.	Concentrate piping, which conveys the concentrated waste stream (i.e., reject flow) to final
disposal.
Sufficient pretreatment is essential for reliable operation of RO membranes; organic colloids, biological
growth, and inorganic scale can all impede the production of water and cause elevated feed pressures,
increased cleaning frequency, and higher operating costs. Pretreatment depends on the feed water
characteristics, and designing an RO system requires a thorough chemical analysis. MF or UF traditionally
serves as a pretreatment process for the RO in wastewater applications to mitigate potential fouling that
results in higher operating costs, more frequent chemical cleaning, and more rapid RO membrane
replacement. When fouling does occur, it decreases the membrane system efficiency, requiring more
energy to treat the water. Membranes are periodically chemically cleaned to remove foulants. Foulants can
cause permanent damage that requires membrane replacement. Common types of membrane fouling
improve with pretreatment:
•	Scaling - Scaling over the membrane can be a problem if there is high calcium, magnesium, or
other sparingly soluble salts in the wastewater, or if there are high recovery rates.
•	Colloidal fouling - Elevated organic material, silica, and clarifier treatment chemicals (iron or
aluminum salts) can cause colloidal fouling of the membranes.
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• Biological fouling - Active microorganisms often can attach to the membranes and cause biofilm;
the biofilm can then block the membrane surface.
A chloramine residual is typically added to the feed water to prevent biofouling or biological growth on the
membranes (both MF and RO). A free chlorine residual is not recommended in full advanced treatment
(Chapter 7) because of the potential to damage downstream RO membranes.
One disadvantage of RO treatment is that it creates a highly concentrated reject water stream. For reuse
facilities, it is important that RO waste streams are not returned to the same wastewater treatment plant
supplying the flow unless the RO plant represents a very small portion of the overall plant flow (<10 percent
of the total plant flow). This will avoid concentrating salts and other contaminants within a closed loop
between the two plants. The most common methods for disposal of wastewater RO concentrate are ocean
discharges combined with existing wastewater outfalls, sewer disposal with flows directed to a downstream
wastewater treatment facility, surface water discharge and deep well injection. Because the reject stream
is highly concentrated (TDS from 3,000 to 20,000 mg/L), permitting a direct discharge of RO concentrate
to surface water may be difficult, unless high salinity surface waters are present. Alternate methods of
concentrate disposal, not previously mentioned, include use of evaporation ponds, mechanical evaporation,
brine crystal I izers, and various emerging technologies such as forward osmosis and membrane distillation.
Additionally, the RO permeate requires subsequent stabilization due to the near complete removal of
hardness and low alkalinity. Calcium and alkalinity are reintroduced to the RO permeate to stabilize the
water, as discussed in Section 6.6.
6.3.2	ianofiltration (NF)
NF membranes are commonly made of the same or similar materials and through the same processes as
RO membranes (AWWA, 2007). NF membranes are typically configured in the same pressure vessels
as RO and require the same pretreatment steps, making the two hard to differentiate in some instances
(CDM Smith, 2014). In contrast to RO membranes, NF membranes allow the passage of more monovalent
ions, while rejecting highly charged inorganic ions and larger molecular weight organic constituents
(CORPUD, 2014). NF typically requires a lower feed pressure than RO and therefore can be lower in cost;
however, NF can still provide an effluent water quality comparable to RO when TDS reduction is not
required. Early studies looking at NF wastewater treatment found that many NF membranes fouled more
quickly than the RO membranes most commonly used in potable reuse, resulting in operating pressures
that were not any lower than RO (Bellona et al., 2008).
NF has two important disadvantages compared to RO. The first disadvantage is that NF membranes
provide less TDS removal than RO membranes (CORPUD, 2014). The second disadvantage is that NF
membranes have poor nitrate rejection (Amouha et al., 2011), which can be a crucial consideration for
potable reuse schemes that treat wastewater with potentially high nitrate levels (Bellona et al., 2008). When
considering NF for potable reuse treatment trains, an effective nitrogen removal process such as ion
exchange orsidestream RO may need to ensure adequate removal (CORPUD, 2014).
6.3.3	Electrodialysis/Electrodialysis Reversal (ED/EDR)
ED utilizes ion selective membranes in an electrically driven process to transport mineral salts and other
constituents from one solution to another, forming a concentrate and a dilute solution (Asano et al., 2007).
An ED system includes both cation and anion membranes stacked in an alternate pattern between spacers
with a positive electrode (anode) on one end and a negative electrode (cathode) at the other end (Asano
et al., 2007). A direct current is applied, creating an electrical current potentially responsible for moving the
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ions through the membranes. Ions of opposite charge from the membrane are rejected and exit the system
in the form of a concentrate (Asano et al., 2007).
EDR was introduced in the early 1970's (Asano et al., 2007). EDR is identical to ED, but it employs periodic
reversal of the direct current polarity as a self-cleaning mechanism (Asano et al., 2007). EDR operates
most ideally using water with a TDS concentration of 1,000 to 5,000 mg/L, but it can treat water with
concentrations reaching 10,000 to 12,000 mg/L.
Unlike RO and NF membranes, ED and EDR do not result in a reduction of suspended solids, pathogens,
or non-charged contaminants of emerging concern (CECs), but they are capable of reducing TDS through
the removal of charged ions. EDR is also effective for bromide removal, which can reduce bromate
formation. With respect to potable reuse, ED and EDR would only apply in situations where other unit
processes capable of removing total suspended solids (TSS), pathogens, and CECs are included in the
treatment train.
6.3.4	Ion Exchange
Ion exchange incorporates a solid phase ion exchange material that is used to replace an ion in the aqueous
phase for an ion in the solid phase. The most common cation application of ion exchange processes is in
water softening methods, where the hardness of the water is lessened by removing magnesium and calcium
ions from the water and replacing them with sodium ions from a solid phase exchange material such as
polymeric resin, kaolinite, or montmorillonite. Cationic resins replace cations, whereas anionic resins
replace anions. Essentially, the exchange materials have fixed charge functional groups attached to the
material itself. Oppositely charged ions, known as counter ions, uphold the electroneutrality of the exchange
material and the aqueous solution, allowing removal of select ions from the water via replacement. Ion
exchange can remove a variety of constituents such as boron, barium, radium, arsenic, perchlorate,
chromate, Na+, CI", SO42", NH4+, and NO3" (Asano et al., 2007). Ion exchange is not currently used in any
potable reuse applications but could provide benefit as a polishing step for nitrate removal.
6.3.5	Activated Carbon
Activated carbon works by adsorption, which is the process by which molecules are concentrated on a solid
surface. The structure of the activated carbon results in a very large effective surface area for compound
adsorption. Activated carbon can have a surface area of greater than 1000m2/g (Wan Nik et al., 2006).
Activated carbon's characteristics and performance are influenced by the substance it is made from, which
can include various materials like coal, coconut shells, or wood (NRC, 1980)
There are two primary forms of activated carbon used in water treatment processes: GAC and PAC. GAC
includes "irregularly shaped particles [with] sizes ranging from 0.2 to 5 mm" (Wan Nik et al., 2006); it is
often used as filtration bed media. PAC is a "pulverized [material] with a size predominantly less than
0.18mm" (Wan Nik et al., 2006).
Activated carbon can adsorb contaminants, such as organic chemicals. Activated carbon is particularly
well-suited for removal of larger molecular weight and hydrophobic organic compounds, while smaller-chain
hydrophilic aliphatic hydrocarbons are not as well-removed. PAC is sometimes utilized in the activated
sludge process to increase solids contact, and GAC is commonly used as the media component in pressure
and gravity filters (NRC, 2012a).
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6.3.6 Biologically Active Filtration (BAF)
BAF is an operational practice of managing, maintaining, and promoting biological activity within a filter to
enhance treatment for organic and inorganic constituents. A biofilter can be any filter that allows a
biologically active layer to establish and colonize the filter media surface. Examples include slow sand
filtration, rapid rate filtration with or without preoxidation, GAC filtration with or without preoxidation,
riverbank filtration, aquifer filtration, and anoxic biological treatment (Evans et al., 2010). Typically,
indigenous microbial organisms populate the biofilter, and contaminants are biodegraded through direct
substrate utilization or cometabolism. Biofilters can remove turbidity, natural organic matter (NOM),
disinfection by-product precursors, taste and odor compounds, iron, manganese, ammonia, algal toxins,
and trace chemical constituents including pharmaceuticals and personal care products (Evans et al., 2013;
Bouwerand Crowe, 1988; Hoegeretal., 2004; Evans et al., 2010; Hozalski and Bouwer, 2001; Wunderet
al., 2008).
Water quality and operational parameters such as pH, temperature, and hydraulic loading rates can impact
treatment performance (Evans et al., 2013). Biofiltration does not remove TDS. Potable reuse treatment
trains that utilize biofiltration and require TDS management may couple other processes such as EDR or
RO in a split stream treatment scenario to achieve site-specific TDS targets. Chapter 7 further discusses
biofiltration.
6.4 Disinfection and Removal of Trace Organic Compounds
Disinfection is used as an additional barrier after removing suspended solids and reducing dissolved
chemical concentrations. Chapter 4 describes pathogens potentially present in raw wastewater. With
respect to drinking water from surface water systems and groundwater systems under the direct influence
of surface water (GWUDI), disinfection treatment requirements are driven by source water quality, as
indicated in the Surface Water Treatment Rules; the 2006 Ground Water Rule regulates contaminated
groundwater. Chapter 3 provides further elaboration on these rules.
While the primary purpose of disinfection is to inactivate pathogenic microorganisms, some disinfection
processes can also degrade chemical contaminants through oxidation (CDM Smith, 2014). The disinfection
technologies used throughout a potable reuse treatment train are designed to meet recreational water
quality criteria and extend into oxidation and advanced oxidation to address trace organic contaminants.
Disinfection technologies that might apply in a potable reuse scenario include UV, chlorination, peracetic
acid disinfection, pasteurization, chlorine dioxide, ozone, and advanced oxidation processes (AOPs).
6.4.1 UV
UV light is considered a biophysical disinfection method primarily because of its ability to prevent
microorganisms from replicating; this is because light is absorbed by nucleic acids and results in
dimerization (Khan, 2013). At high UV doses, UV photons are capable of breaking chemical bonds that
have lower energy than the photons themselves (CDM Smith, 2014).
There are three types of UV lamps currently used in water treatment at WWTPs, AWTFs, and WTPs. These
include low-pressure low output, low-pressure high output (LPHO), and medium pressure (MP). The most
common lamp type used in water treatment applications is the LPHO lamp with a monochromatic output at
a wavelength of 254 nanometers. While LP lamps are also commonly employed due to their low energy
consumption in comparison to MP lamps, LPHO systems are usually employed in low dose applications,
such as permitted wastewater discharges to surface waters. MP UV lamps are used at facilities with limited
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space because they are more energy intensive, and the high output allows for the use of fewer lamps; but,
these lamps have a lower germicidal efficiency.
The water quality parameters of concern for UV disinfection systems are UV transmittance (UVT), which is
related to TSS and particle size. Utilizing filtration methods prior to disinfection can enhance UV disinfection
performance. UV intensity, a measure of the incident UV light, is directly related to the UVT; the higher the
UVT, the higher the intensity (actual UV intensity is also affected by the extent of sleeve fouling, power
input, and the age of the lamps). The UV dose is the UV intensity multiplied by the exposure time. Shielding
of target organisms can occur when high TSS orturbidity are present in water. In some cases, higherdoses
of UV light can help overcome this shielding, but it may not be possible to provide adequate disinfection in
some secondary effluents (CDM Smith, 2014). In direct potable reuse (DPR) treatment trains in particular,
employing high UV doses (~800 mJ/cm2) are critical for both pathogen removal (Soller et al. 2017; Soller
et al. 2018) and carcinogenic by-products, such as N-nitrosodimethylamine (NDMA) (Gerrity et al., 2015b)
6.4.2 Chlorine/Chloramines
Chlorine disinfection is the most widely used form of disinfection in water and wastewater treatment in the
United States. Chlorine may be applied as chlorine gas, liquid sodium hypochlorite, or as solid calcium
hypochlorite. On a pound for pound basis, chlorine gas is much less expensive than other chlorination
methods, but it poses significant safety challenges regarding storage and handling (CORPUD, 2014). As
such, many U.S. utilities converted to alternative technologies to eliminate its use.
Raw wastewater contains nitrogen in the form of ammonia; plants that provide only secondary treatment
cannot convert or remove ammonia. When ammonia remains in the secondary effluent and chlorine (in any
form) is added to the water, the chlorine reacts to form chloramines. Although dependent on the chlorine to
nitrogen ratio and operating parameters such as pH, temperature, and contact time, the dominant forms of
chloramines are monochloramine and dichloramine, and the less common form is trichloramine. These
types of chloramines also serve as disinfectants; but, they are significantly less effective at inactivating
pathogens, especially for viruses, and react slower when compared to free chlorine (White, 1986; EPA,
1989a). Because chloramines are a less powerful disinfectant than free chlorine, they tend not to oxidize
trace chemical constituents; therefore, chloramination reduces the likelihood of some disinfection by-
products, such as trihalomethanes, haloacetic acids, and chlorate (EPA, 1999b). However, chloramines
can increase the formation of nitrosamines, such as NDMA (Wetterau et al., 2011).
The two types of residual chlorine, free and combined, are distinguished by the disinfection method utilized
and the breakpoint chlorination curve (Szerwinski et al., 2012). When breakpoint chlorination is used (along
with a free chlorine reagent during analysis), the measured chlorine residual is known as the free chlorine
residual as shown in Figure 6-4.
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DjO 4 —
E
Initial
Chlorine
Demand
Chlorine Reducing
Compounds
(e.g. Orgonic-N,
Additional
Chlorine Dose
\ , TRC Required for FRC
Breakpoint
o
1234S6789 10 11
CHLORINE DOSE (mg/L)
Figure 6-4. Typical breakpoint chlorination curve
When chloramines are the sole disinfectant, the measured chlorine residual is combined chlorine
(dependent upon the reagent used during analysis). The breakpoint chlorination curve determines the
amount of chlorine needed to oxidize organic and inorganic material and leave a free chlorine residual to
achieve pathogen reduction (Asano et al., 2007). Many U.S. drinking water systems utilize combined
chlorine in the distribution system to overcome issues associated with regulated disinfection by-product
(DBP) formation, such as THMs and HAAs.
6.4.3	Peracetic Acid (PAA)
PAA can be used as a wastewater disinfectant, although it is a relatively new method in the United States.
There are only a few WWTPs currently using PAA, but it has a long history of use in the food, beverage,
medical, and pharmaceutical industries (CORPUD, 2014). PAA is delivered as an equilibrium mixture of
acetic acid, hydrogen peroxide, PAA, and water. The PAA component of the solution has the chemical
formula CH3CO3H. PAA performance as a disinfectant is dependent upon water quality and operating
conditions. At pH values below seven, PAA's disinfection efficacy increases (CORPUD, 2014). Disinfection
with PAA requires very low doses and short contact times to inactivate bacteria (Kitis, 2003). Additionally,
because of PAA's widespread use in the medical and agricultural industries, there is a significant, body of
information that suggests that PAA is effective against viruses and protozoa. Further, when paired with UV
processes forwastewaterdisinfection, the efficacy increases substantially (Asano et al 2007). Additionally,
PAA does not form known harmful disinfection by-products.
6.4.4	Pasteurization
Recently, pasteurization gained attention in the wastewater disinfection field. In sewage sludge processing,
pasteurization produces Class A Biosolids (EPA, 2012a). The efficacy of pasteurization depends on
operating conditions such as temperature and exposure time, characteristics of the organisms of interest,
and characteristics of the medium (EPA, 2012a). Pasteurization processes could save operational costs
compared to other disinfection methods, such as UV, because waste heat can preheat undisinfected water.
While the process received California Title 22 approval for reclaimed water disinfection, only one
pasteurization unit appears to be in operation to date at a small municipal facility in Graton, California
(CSWRCB, 2014). This facility is utilizing the process to provide reclaimed water for non-potable use.
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6.4.5	Chlorine Dioxide
Chlorine dioxide has a high oxidation potential and therefore excellent germicidal power. While chlorine
dioxide is commonly used in drinking water treatment, there are no U.S. publicly owned treatment works
utilizing this technique for wastewater disinfection or reuse. It is both an effective bactericide and virucide
and achieves more effective inactivation of viruses than chlorine itself. Chlorine dioxide is inherently
unstable and readily decomposes and is typically generated onsite. The required dose for meeting
disinfection objectives varies based on the pH and the microorganisms in the water. It is thought to be
similarly effective as combined chlorine at inactivating bacteria, and similarly effective as free chlorine at
inactivating viruses (Asano et al., 2007). Chlorine dioxide was included as a toolbox option for
Cryptosporidium inactivation in the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR)
and dose tables for receiving inactivation credit were provided (EPA, 2006b). But, a major drawback to
chlorine dioxide is that it can form toxic disinfection by-products such as chlorate and chlorite (NRC, 2012a).
The control methods (other than process control management of dose/residual application) to mitigate
these DBPs can be costly, including the addition of ferrous iron, sulfite, or using granular activated carbon
to absorb the ions (Asano et al., 2007).
6.4.6	Ozone
Ozone (O3) is a disinfection technology commonly used in drinking water treatment. Ozone is a powerful
oxidant, capable of breaking down organic compounds including taste and odor compounds and trace
chemical constituents. The concept of using ozone for wastewater and reclaimed water treatment gained
increasing interest in recent years; a handful of plants have adopted the technology (Gerrity et al., 2015a;
EPA, 2012a) because of its ability to provide disinfection and oxidation of organic carbon, including CECs.
Ozone is produced when oxygen separates into atomic oxygen; the result is an unstable gas (O3). It is likely
that free radicals form when ozone is decomposed. HO2 and HO» are responsible for a significant portion
of the oxidation in the disinfection process, making ozone an AOP (Asano et al., 2007). Ozone is a potent
chemical disinfectant with an oxidant electrode potential (redox potential) of 2.08 V at 25 degrees Celsius
and is very effective at pathogen inactivation - stronger than both chlorine (0.8 to 1.5 V) and
monochloramine (0.7 to 0.8 V) at 25 degrees Celsius (James et al., 2004). Because ozone is an unstable
gas that decomposes to elemental oxygen very rapidly after generation, it requires on-site generation. In
general, an ozone disinfection system typically includes the following major components:
•	Oxygen supply system (typically liquid oxygen is supplied to tanks onsite, but it can also be
generated onsite at large capacity facilities).
•	Ozone generators and the associated power supply units (PSUs).
•	Ozone contactors and associated ozone gas transfer systems.
•	Ozone contactor off-gas handling and residual ozone gas destruction systems and ozone gas
monitoring and control systems.
Recent ozone technology improvements have made the process more energy efficient. Some of these
improvements include oxygen production for feed gas, improvements in generator technologies, and
injection technologies that allow higher mass transfer efficiencies. Additionally, improvements in dielectric
technology, materials of construction, power supply components, control methods, and ozone generation
production control logic resulted in reduced energy requirements and many economic benefits.
Ozone is a mature disinfection technology that merits serious consideration as a cost-effective treatment
option for potable reuse treatment trains, particularly in light of the recent advances in ozone generation
and application technologies. It is increasingly evaluated for its applicability to reuse, primarily because it is
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the only mature disinfection alternative capable of treating complex, non-degradable trace organic
compounds (e.g., pharmaceutical and personal care products and endocrine disrupting compounds
(EDCs)) at typical disinfection doses (CORPUD, 2014).
Ozone can replace MF, UF, or RO processes and supplement biofiltration within potable treatment trains
to remove trace chemical constituents; additionally, it can be a pretreatment process for MF to increase MF
performance (CORPUD, 2014). However, when polymeric filters are utilized, the ozone residual must be
dissipated before filtration to protect against the oxidation of the membrane material. Ozone can also be
used as a disinfectant either in place of UV-AOP or in conjunction with UV to produce an AOP.
6.4.7 Advanced Oxidation Processes (AOPs)
AOPs can destroy trace chemical constituents. AOPs produce the hydroxyl radical (HO»), which is a very
powerful oxidant (Asano et al., 2007). The breakdown products at different doses and water qualities are
largely unknown, although organic compounds can be oxidized to CO2 at extreme doses. Because of their
unique ability to destroy and not just remove these compounds, AOP is often a final component of treatment
trains in potable reuse applications (Asano et al., 2007). While AOP is part of the full advanced treatment
train (described further in Chapter 7), it may not be necessary when additional treatment will be applied
at a downstream public water system. AOP prior to discharge to a surface water storage reservoir is
generally unnecessary. However, AOP may be quite useful at WTPs that have taste and odor issues, and
also as a treatment tool to address contaminants that may pass through the previous treatment processes.
6.4.7.1	UV/Hydrogen Peroxide
The combination of UV light and hydrogen peroxide (H2O2) results in two simultaneous mechanisms
responsible for the degradation of trace chemical constituents (CORPUD, 2014). The first mechanism is
UV photolysis (discussed in Section 6.4.1), and the second mechanism is the generation of hydroxyl
radicals through the UV light and hydrogen peroxide reaction (CORPUD, 2014). In some instances, low
concentrations of very small compounds including trace chemical constituents may remain in permeate
from upstream RO processes; UV/hydrogen peroxide is effective at oxidizing these constituents (CORPUD,
2014). It has been applied successfully in the development of potable reuse projects such as the Orange
County GWRS (California), West Basin Advanced Water Treatment Plant (AWTP) (California), Vander Lans
AWTP (California), Big Spring (Texas), and Cloudcroft (New Mexico) (CORPUD, 2014).
6.4.7.2	Ozone/Hydrogen Peroxide
Ozone/hydrogen peroxide AOP is an alternative process to UV/hydrogen peroxide and used for taste and
odor control in drinking water. The combination of ozone/hydrogen peroxide results in lower power costs
than UV/hydrogen peroxide (CORPUD, 2014). Ozone/hydrogen peroxide also results in higher removal
efficiencies for some select trace chemical constituents (CORPUD, 2014). However, the process achieves
lower removal rates of NDMA and other light sensitive species when compared with UV-based AOPs
(CORPUD, 2014). In situations where the reclaimed water has sufficiently low nitrosamine
concentrations, or where the UVT is a limiting factor, ozone/hydrogen peroxide may be a viable process
alternative (Gerrity et al., 2013a).
6.4.7.3	UV/Chlorine
UV/Chlorine, like UV/hydrogen peroxide, utilizes photolysis and the formation of hydroxyl radicals to
degrade small, trace chemical constituents in reclaimed water (CORPUD, 2014). The UV/chlorine process
requires a free chlorine residual and is very sensitive to pH; but, it can be more efficient than UV/hydrogen
peroxide when chlorine demand is low, and the pH is less than 6 to 6.5 (Wetterau et al., 2015b). For this
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reason, UV/chlorine offers advantages for AOP in RO permeate but may offer fewer advantages in non-
RO based reuse facilities that have higher pHs. UV/chlorine offers three primary advantages for direct
potable reuse, independent of any operational or capital cost savings. First, chlorine is a far superior
disinfectant to hydrogen peroxide, providing disinfection redundancy not present in the UV/hydrogen
peroxide process. Secondly, use of UV/chlorine avoids the need for peroxide quenching priorto the drinking
water treatment plant, or prior to introducing the purified water into a drinking water system. Finally,
UV/chlorine offers a low cost means of integrity monitoring through the measurement of free chlorine
residual. As of 2015, UV/chlorine was not used at any indirect potable reuse (IPR) or direct potable reuse
(DPR) facilities; but, it has been full-scale tested in California at the Vander Lans AWTP and the Cambria
Emergency Water Supply, and it is planned for the Terminal Island AWTP plant expansion (Wetterau et al.,
2015a). The drawback to UV/chlorine AOP is that little research exists on the disinfection by-products that
may form during this treatment process.
6.5 Aesthetics
Public perception will play a substantial role in the future acceptance of DPR schemes. The end result of
the scheme is the final purified water (or drinking water) that the general public ultimately consumes. It is
important to emphasize the aesthetic properties of the final purified water with respect to taste, odor, and
color. Independent of the consistent safety of a purified product, the water will be judged based on how it
tastes, looks, and smells. Water which stains sinks or discolors glasses is viewed negatively, regardless of
how well the treatment processes remove regulated and unregulated contaminants. In potable reuse
applications, the goal is to produce an effluent free from any objectionable taste, odor, or color, while
meeting or exceeding the aesthetic quality of any existing local drinking water supplies. Table 6-2 lists some
potential aesthetic compounds from wastewater.
Table 6-2. Aesthetic compounds potentially present in untreated municipal wastewaters
Contaminant
Noticeable Effects above the Secondary MCL
Aluminum
Colored water
Chloride
Salty taste
Color
Visible tint
Copper
Metallic taste; blue-green staining
Corrosivity
Metallic taste; corroded pipes/fixtures staining
Fluoride
Tooth discoloration
Foaming agents
Frothy, cloudy; bitter taste; oily, fishy, or perfume-like odor
Iron
Rusty color; sediment; metallic taste; reddish or orange staining
Manganese
Black to brown color; black staining; bitter metallic taste
Odor
"Rotten-egg," musty or chemical smell; quantified by TON
PH
Low pH: bitter metallic taste; corrosion
high pH: slippery feel; soda taste; deposits
Silver
Skin discoloration; graying of the white part of the eye
Sulfate
Salty taste
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Contaminant
Noticeable Effects above the Secondary MCL
TDS
Hardness; deposits; colored water; staining; salty taste
Zinc
Metallic taste
6.5.1	Taste and Odor Control
Taste and odor issues in water can arise from a variety of different sources. For example, surface waters
may have significant algal blooms or groundwater may contain dissolved minerals such as iron and
manganese. Disinfection by-products formed during treatment can cause taste and odor problems in water.
Salinity can also cause taste issues (EPA, 2012a). Inaccurate chlorine dosing can result in product water
that tastes or smells like bleach. Industrial discharges such as phenols cause a distinct "medicinal" taste.
Demineralized effluent from RO or NF can have a taste often described as "metallic" if it is not sufficiently
stabilized through hardness addition (Khan, 2013).
Two well-known compounds that negatively affect the taste and odor of water are Geosmin and
2-methylisoboreneol (MIB). These compounds are naturally occurring in lakes and reservoirs and cause an
earthy, musty smell and taste in the water. The taste and odor concerns associated with these compounds
are not related to any negative health effects, but they can cause public discontent (NRC, 2012a).
Processes that incorporate powerful oxidants are typically good strategies for controlling taste and odor
(i.e. ozone, chlorine dioxide, AOP), but strong oxidants run the risk of harmful by-product formation.
Activated carbon (PAC, GAC) is another method that can effectively reverse poor aesthetics. The combined
process of ozone and biologically activated carbon (BAC) effectively controls taste, odor, and color
(CORPUD, 2014). UV/chlorine is also an effective means of taste and odor control as demonstrated by
Watts etal. (2012).
6.5.2	Color
When there is a hue in wastewater, it may be due to dissolved organic material or inorganic constituents
such as metals. Even waters without visible color can cause staining of sinks and plumbing fixtures over
time. Ozone is effective at lessening organic related hues in water, but ozone can oxidize manganese to
permanganate, causing a purple color in water. Dissolved organic carbon (DOC), iron, and manganese
concentrations can be used as indicator parameters to trace whether a wastewater has lost its "color"
identity (Trussell et al., 2013). Although color is not an enforceable primary drinking water regulation, EPA's
Safe Drinking Water Act secondary standard is 15 color units (EPA, 2017k).
6.6 Stabilization
In instances where RO or NF processes treat reclaimed water, it is typically necessary to stabilize the water
by remineralization techniques (Chalmers et al., 2010). RO and NF remove minerals, such as calcium and
magnesium, and produce a permeate water with pH often below 6. The resulting product water is extremely
corrosive and can cause severe corrosion in metal piping or concrete tanks. Advanced treated water is
stabilized through some combination of decarbonation, or addition of lime, caustic soda, and/or calcium
chloride. The stabilization generally targets a Langelier Saturation Index (LSI) near or above zero through
the addition of hardness and alkalinity (AWWA, 2007). Other stabilization indices, such as the Ryznar
Stability Index, can be used in addition to the LSI to determine stabilized water. The following paragraphs
provide basic information on processes commonly used for product water stabilization in RO and NF
facilities. For additional information, AWWA has published a Manual of Practice: Internal Corrosion Control
in Water Distribution Systems (AWWA, 2011 b).
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6.6.1	Decarbonation
Often after RO treatment, packed tower aerators are used to remove carbon dioxide and increase the pH
of the permeate without the addition of chemicals, or in addition to other chemical usage. Decarbonation
can be a low cost means of increasing the pH when sufficient carbonate alkalinity is present. However,
removal of carbon dioxide does not impact the total alkalinity of the water and, in some cases, can increase
the amount of chemicals required to reach a stabilized LSI value. Decarbonation can provide advantages
if other dissolved gases or volatile chemicals, such as trihalomethanes, hydrogen sulfide, methane, or
radon, are present in the water.
6.6.2	Sodium Hydroxide
Sodium hydroxide, or caustic soda, is the most common chemical used for pH adjustment after RO. The
addition of sodium hydroxide will increase the total alkalinity and pH of the water, increasing the LSI and
producing a more stable product water. Because RO permeate is generally low in hardness as well as
alkalinity, sodium hydroxide alone is rarely sufficient for producing a stable product water.
6.6.3	Lime Stabilization
Calcium oxide, or lime, can be used for product water stabilization, adding alkalinity, hardness, and pH to
the water with a single chemical (Khan, 2013). Lime can be purchased as either quicklime (CaO), which
requires the use of a slaker, or hydrated lime (Ca(OH)2), which can be added directly (Khan, 2013). Lime
is often challenging to work with; this is due to clumping in the dry feed equipment, dust accumulation, and
turbidity carryover in the water. While lime is often the lowest cost means of stabilizing RO product water,
many utilities choose to avoid it due to its operational challenges.
6.6.4	Calcium Chloride
Calcium chloride can add hardness to water, but it does not impact the pH or alkalinity. For this reason,
calcium chloride needs to be used in conjunction with another chemical, such as sodium hydroxide. Calcium
chloride can be purchased in liquid form, and it does not cause turbidity when added to water. While it is
costlier than lime, some utilities have chosen to use calcium chloride and caustic soda for stabilization to
avoid the operational challenges associated with lime.
6.6.5	Blending
Blending with fresh surface waters is an additional way to stabilize water following RO or NF treatment.
Mixing the treated water with water of appropriate quality can restore hardness and alkalinity levels.
Blending is a cost-effective restabilization method when sufficient blend water is readily available; the
Wichita Falls emergency DPR system took this approach (see case study in Appendix A).
In DPR schemes, blending could occur at different steps throughout the treatment process; it could occur
before entry into an engineered storage buffer, after storage in the buffer, or before introduction into the
potable water system (WRRF, 2011a). Blending advanced treated wastewater with conventional source
water prior to consumption may or may not occur within a given DPR scheme; this depends on site-specific
constraints (Khan, 2013). For example, some DPR systems may not need to target TDS for removal if they
anticipate high ratios of blending with low TDS source water. Additionally, blending with conventional source
water may mean that remineralization of the DPR water is not required (Khan, 2013). Different blending
configurations can occur within a DPR system. Blending of reclaimed water with alternative water supplies
could occur prior to advanced wastewater treatment or drinking water treatment (Khan, 2013). Researchers
are investigating the potential to blend purified water with conventionally treated water or even direct
distribution. A Water Research Foundation study titled Blending Requirements for Water from Direct
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Chapter 6 | Treatment Technologies for Potable Reuse
Potable Reuse Treatment Facilities will evaluate the possible blending scenarios and associated impacts
(WRF, est. 2018).
6.7 Summary Table of Treatment Technologies
Table 6-3 summarizes the effectiveness of the treatment technologies discussed in this chapter with
respect to achieving three of the five treatment objectives.
Table 6-3. Treatment technologies and associated treatment capabilities (adapted from CORPUD,
2014)
Overall
Treatment
Objective
Unit Processes
TOC
TSS
TDS
Trace
Chemical
Constituents
Pathogens5
Removal of
Suspended
Solids
Media Filtration,
Microfiltration and
ultrafiltration
R
(Minimal)
R
-
-
R6
Reducing the
Concentration
of Dissolved
Chemicals
NF/RO
R3
R
R
R1
R
ED/EDR
-
-
R
-
-
PAC
R
-
-
R
-
GAC
R3
R
-
R3
R (Minimal)
Ion exchange
-
-
R
R
-
Biofiltration
R, D34
R
-
D4
R
Ozone
-
-
-
D2
D
Disinfection
and Removal
of Trace
Organic
Compounds
UV
-
-
-
D2
D
Free Chlorine
-
-
-
D2
D
Chloramines7
-
-
-
-
D2
PAA8
-
-
-
D2
D
Pasteurization8
-
-
-
D
D
Ozone
-
-
-
D2
D
Chlorine dioxide
-
-
-
D2
D
Advanced oxidation
processes (UV/H202,
03/ H202, UV/CI2)
-
-
-
D2
D
Key:
Pink = no impact, orange = partial impact; green = significant impact
R = constituents that are physically removed; D = constituents that are degraded or destroyed
Notes:
1	Some chemical constituents may have RO removal efficiencies less than 90%, such as NDMA, 1,4-dioxane, and
flame retardants. Additionally, RO likely has greater removal efficiency than NF.
2	Removal depends on contaminant dose and contact time.
3	TOC removal is 40-60% and 98% for GAC/BAC and RO/NF, respectively.
4	BAC is effective at removing trace chemical constituents, but, BAC will result in higher TOC levels than RO.
5	Actual removal efficiencies vary by unit process depending on the specific constituent or group of constituents of
concern. The doses and contact times used in some processes, such as oxidation, define the extent of removal of
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pathogens. In any case, potable reuse applications should always employ multiple barriers to ensure redundancy and
resiliency.
6	MF and UF membranes can remove bacteria and protozoa. MF is not considered an effective barrier against
viruses, while UF can remove viruses to a certain extent.
7	Extended chloramine contact times are required for virus inactivation, but, no Giardia or Cryptosporidium
inactivation should be anticipated with chloramine disinfection.
8	Currently used only in wastewater treatment.
6.8 Residuals Management
As in conventional WTPs and WWTPs, the residuals generated from potable reuse treatment trains must
be managed. This can include treatment, reuse, and/or disposal. The residuals produced from an AWTF
can include screenings, backwash solids and liquid streams, and RO concentrate (NWRI, 2015). Solids
from backwashing and screening are commonly macerated and returned to the WWTP, where they are
mixed with other process solids, removed/disposed, and/or incinerated. Reject streams and backwash
water (other than RO concentrate) are often returned to the WWTP or AWTF inlet for retreatment (NWRI,
2015).
In AWTFs utilizing RO, RO concentrate management is a major consideration. In coastal regions, the
concentrate is sometimes sent to ocean outfalls (NWRI, 2015). Where ocean outfalls are not practical, or
are not permitted by state or local ordinance, concentrate may be treated using various brine concentration
and crystallization methods or other salt recovery techniques. This results in a residual that must be
disposed of as a solid waste or sold if the quality of the final product is sufficient for the market. Alternatively,
if it is feasible, concentrate disposal may be accomplished more cost-effectively through deep-well injection,
surface water discharge, land application, ordischarge to the wastewater collection system (for small flows).
The Framework for Direct Potable Reuse describes some of the common RO concentrate management
approaches, regulatory considerations, and costs (NWRI, 2015). Refer to Chapter 11 for a discussion of
the costs of residuals management.
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Chapter 7 | Alternative Treatment Trains for Potable Reuse
CHAPTER 7
Alternative Treatment Trains for Potable
Reuse
7.1 Overview
Chapter 6 covered individual unit treatment processes. This chapter will cover the integration of these unit
processes into a number of different treatment trains. A treatment train is a series of unit processes that
treat water to the desired effluent quality (NWRI, 2015). Advanced wastewater treatment for potable reuse
involves a strict source control program of raw wastewater treatment at a wastewater treatment plant
(WWTP) and additional treatment at an advanced wastewater treatment facility (AWTF). Subsequently, the
advanced treated wastewater may go to an environmental buffer, an engineered buffer, or a drinking water
treatment plant. While some researchers are evaluating the feasibility of introducing AWTF water directly
into the potable water distribution system, this scenario is not currently practiced in the United States.
Treatment trains for water reuse are assembled to address site-specific requirements and developed based
on influent water quality characteristics and applicable federal, state, and local regulatory requirements.
Other factors such as energy requirements, operation and maintenance (O&M) requirements, capital and
O&M costs, staffing considerations, and affinity with existing operations also determine the optimal
treatment train (Asano et al., 2007). There are numerous possible combinations of unit processes for
specific reuse applications. In potable reuse applications, the treatment train needs to encompass
redundancy and reliability against waterborne pathogens and chemical contaminants to protect public
health. It also should allow enough time to address any loss in integrity of any components of the treatment
train.
There are two ways to achieve redundancy within the treatment train. First, system designs can build in
redundancy by providing additional capacity within each unit process (e.g., N+1). Second, the system
design can utilize multiple treatment barriers capable of collectively removing a wide range of constituents
with varying physiochemical properties, including inorganic contaminants, organic contaminants, viral,
bacterial, and protozoan pathogens. As described in the 2012 Guidelines for Water Reuse it may not always
be necessary to provide such high levels of redundancy given the effectiveness and reliability of available
technologies (EPA, 2012a). There is the potential to "over-design" AWTFs using large margins of safety to
account for uncertainty in target treatment objectives for unregulated chemical compounds (Gerrity et al.,
2013a; NRC, 2012a).
Figure 7-1 illustrates different potable reuse treatment trains. The key distinguishing difference between
indirect potable reuse (IPR) and direct potable reuse (DPR) is the lack of an environmental buffer in DPR.
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Namibia Model ¦ DPR • No RO
Cloudcroft Model • DPR • MBR
Big Springs Model • DPR • UV-AOP
Wichita Falls Model • DPR • UV
Singapore Model • IPR • UV
California Model • IPR • UV-AOP
Upper Occoquan Service
Authority (UOSA) Model • IPR •
Chlorination
Gwinnett County • IPR •
Ozone/Bioflltration
San Diego Advanced Water Purification
Demonstration Project- Demo Only •
Ozone-BACFull Advanced Treatment
Buffers	Blends
P> Aquifer J)> Surface Water Body O Spring and Well Water O Surface Water
* Blending occurs in engineered storage buffer (holding lagoon)
" Only requires chlorination after residence time
Figure 7-1. Overview of potable reuse treatment trains in existence as of 2015
(not intended to be a complete survey)
7.1.1	Multiple Barrier Approach
In 1982, a document, titled A Guide for the Planning, Design, and Implementation of a Water Reclamation
Scheme highlighted critical aspects of potable reuse learned from a DPR plant in Namibia (PGJ Meiring &
Partners, 1982). The document emphasized that incorporation of multiple barriers in potable reuse
treatment trains is crucial to ensuring public health protection. The concept of multiple barriers refers to a
series of unit processes operating, with some level of redundancy, to prevent harmful microbes and
chemical constituents from passing into the treated water system (Khan, 2013). Potable reuse requirements
in the United States developed to date mandate use of multiple barrier approaches, including the California
Division of Drinking Water (DDW) Groundwater Replenishment with Recycled Water regulations (see
Chapter 3 for regulations). More recently, the Texas Commission on Environmental Quality approved
individual projects using treated effluent from the wastewater treatment facilities to supplement water
treatment plant (WTP) supplies (see Appendix A). In both cases, treatment scenarios were modeled after
the Singapore and California facilities using rigorous process controls and monitoring requirements and
resulted in designs protective of human health.
7.1.2	Source Control
Source control programs are a fundamental element of the multi-barrier approach to ensure the protection
of public health. Source control programs for wastewater are implemented to reduce the discharge of
contaminants not specifically treated at WWTPs. The constituents originate from industrial, commercial,
health-related, and residential sources (Alan Plummer Associates, 2010). For a discussion of source
control, refer to Chapter 8.
WWTP V DAF V	Ozone	BAC/GAC — UF » BlendQ
tB^r MBR
>
RO
^ UV-AOP
\
Blend (J ,3 WTP
w WWTP
>
MF
y4
RO
UV/H20J Blend 0 .^ WTP







WWTP
>
MF
>
RO
>
UV ^ Blend'O — WTP ,
WWTP
N>
MF
\
RO

UV _ Buffer J WTP
WWTP
>
MF
\
RO
\
UV-AOP Buffer WTp"

«—* WWTP
X
Media
Filtration
I
GAC
A
Chlorine Buffer — WTP
— WWTP - Fitomh'ti "* 0zon» - BAC - Oione - Buffer f
WWTP M Ozone V BAC /jb MF ^ RO	UV-AOP
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7,1.3 Optimizing Upstream Wastewater ttmemt
Wastewater treatment is a critical step in producing water that is suitable for an AWTF (NWRI, 2015).
Optimizing upstream wastewater treatment can ensure that high quality, reliable, and consistent effluent
goes to the AWTF. This is an important first step in AWTF design and can help ensure cost-effective and
functional treatment. For an overview of wastewater treatment and a brief description of components that
should be optimized before investing in an AWTF, see Chapter6 ofthe Framework for Direct Potable Reuse
(NWRI, 2015).
It is important to note that in the United States, all wastewater must undergo secondary treatment (unless
there is some extenuating circumstance). Some AWTFs utilize secondary effluent as source water for
potable reuse applications, but further treatment may be desirable to improve the feed water quality prior
to entering advanced treatment.
Optimization of wastewater treatment processes can enhance treatment performance to meet these
objectives. Operational parameters of activated sludge, such as solids retention time (SRT) and oxygen
conditions, are important in addressing constituents of emerging concern. For example, Gerrity et al.
(2013b) and Zeng et al. (2013) demonstrated enhanced removal of compounds susceptible to
biodegradation and/or sorption, such as antibiotics and analgesics, when the SRT was optimized for control
of nitrogen in a conventional full-scale activated sludge WWTP. However, some pollutants do not exhibit
susceptibility to biodegradation or sorption. Similarly, Miller et al. (2013) found that operational conditions
are likely the greatest influence on antibiotic resistant genes (ARGs). Thus, optimizing wastewater
treatment can dramatically improve the water quality received by the AWTF.
7.2 Types of AWT Unit Processes Used in Potable Reuse Treatment Trains
In general, there are two categories of treatment train options considered for AWTF use in a DPR scenario;
one based on reverse osmosis (RO), and a second based on ozone-biological active filtration (BAF). There
are many other combinations potentially acceptable for planned IPR or de facto reuse. This section
describes the major treatment combinations considered for both IPR and DPR applications, including the
more common treatment combinations for different treatment objectives.
7.2.1	WWTP to Surface Water Discharge
In the most common potable reuse and de facto reuse applications, wastewater is treated to secondary
standards, as outlined in the Clean Water Act (CWA); the criteria include using full biological treatment to
produce treated effluent with < 30 mg/L of biochemical oxygen demand (BOD) and < 30 mg/L of total
suspended solids (TSS). Often, the conventional WWTP's secondary process is modified by changing the
SRT, adding chemicals to facilitate settling, or by carefully selecting the microorganism populations to
accomplish nitrification, denitrification, and phosphorus removal (Gerrity et al., 2013a). In many scenarios,
treated wastewater effluent receives additional treatment when it is discharged into a surface water body
that serves as the drinking water source; treatment may include biological nutrient removal and othertertiary
treatment processes. Tertiary treatment could consist of membrane or media filtration and disinfection
through chlorine, chloramines, ultraviolet light (UV), or ozone (Gerrity et al., 2013a). Following surface water
discharge, the water in these reuse schemes receives further treatment at a drinking water treatment plant.
The treated wastewater augments the available water resources (NRC, 2012a).
7.2.2	WWTP to Soil Aquifer I .'~ itment (SAT)
California is well-known for employing conventional WWTP processes before groundwater recharge into
drinking water basins (Gerrity et al., 2013a). SAT can be initiated through surface spreading operations or
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Chapter 7 | Alternative Treatment Trains for Potable Reuse
direct injection. In surface spreading applications, SAT has been shown to be effective for the attenuation
of pathogens, bulk organic matter, and trace organic compounds over time and is described in Chapter 9
(Gerrity et al., 2013a). The California DDW grants log removal credits (LRCs) for viruses, Giardia, and
Cryptosporidium when employing surface spreading (CDPH, 2014) The underground residence time of the
water determines the LRCs. Giardia and Cryptosporidium receive full removal credit when the source is
disinfected filtered effluent, and surface spreading occurs for a minimum 6-month aquifer travel time
(CDPH, 2014). Virus removal, in contrast, receives 1 -log credit per month for in-basin travel time, up to 6
months (Gerrity et al., 2013; CDPH, 2014). Projects using direct injection receive no credit for SAT impact
on Giardia or Cryptosporidium but receive a 1 -log per month virus credit, up to 6-log (CDPH, 2014). LRCs
require a minimum 2-month ground travel time regardless of the level of pathogen reduction achieved by
upstream processes (CDPH, 2014). As of 2015, only one facility, the Cambria Emergency Water Supply,
received approval for the minimum 2-month travel time.
The 2012 Guidelines suggested approaches for groundwater recharge of potable aquifers via surface
spreading, injection, and augmentation of surface water supplies (EPA, 2012a). A summary of these
approaches is in Table 7-1. Aquifer storage and recovery (ASR) is a term for the widely used technical
method for storage of reclaimed water and excess water in a groundwater formation for later withdrawal
and beneficial use. For a technical report on principles involved in ASR, as well as tools and methods for
ASR system planning, assessment, design, and evaluation, refer to EPA's Decision Support System for
Aquifer Storage and Recovery (ASR) Planning, Design and Evaluation- Principles and Technical Basis
(EPA, 2017m).
Table 7-1. IPR application approaches (adapted from EPA, 2012a)
Type of IPR
Treatment Steps
Water Quality Parameters
Groundwater Recharge via
Spreading into Potable
Aquifers
¦	Secondary1
¦	Filtration2
¦	Disinfection3
¦	SAT
¦	No detectable total coliform /100 mL
¦	1mg/L Cb residual (Min)
¦	pH = 6.5-8.5
¦	< 2 NTU
¦	< 2 mg/L TOC of wastewater origin
¦	Meets drinking water standards by time of exit
from the vadose zone
Groundwater Recharge by
Injection into Potable
Aquifers
¦	Secondary1
¦	Filtration2
¦	Disinfection3
¦	Advanced Wastewater
Treatment4
¦	No detectable total coliform /100 mL
¦	1mg/L CI2 residual (Min)
¦	pH = 6.5-8.5
¦	< 2 NTU
¦	< 2 mg/L TOC of wastewater origin
¦	Meets drinking water standards
Augmentation of Surface
Water Supply Reservoirs
¦	Secondary1
¦	Filtration2
¦	Disinfection3
¦	Advanced Wastewater
Treatment4
¦	No detectable total coliform /100 mL
¦	1mg/L CI2 residual (Min)
¦	pH = 6.5-8.5
¦	< 2 NTU
¦	< 2 mg/L TOC of wastewater origin
¦	Meets drinking water standards
(1)	Refers to treatment processes such as conventional activated sludge, trickling filters, rotating biological
contactors, and may include stabilization pond systems. BOD and TSS should be < 30 mg/L.
(2)	Filtration through soils, filter media such as sand or anthracite, or membrane filtration.
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(3)	Disinfection can be achieved through chemical, physical, or biological processes so long as pathogen inactivation
is accomplished (e.g. through chlorine, ozone, UV, membrane processes).
(4)	Examples of advanced wastewater treatment processes include chemical clarification, carbon adsorption, RO,
membrane filtration, advanced oxidation, air stripping, ultrafiltration (UF), ion exchange.
7.2.3 Full Advanced Treatment and Related Models
Full advanced treatment, or the "California model," does not rely on SAT to remove trace chemical
constituents, meet water quality limits, or achieve additional Giardia or Cryptosporidium removal credits.
Lower levels of treatment are approved and used in California with surface spreading. Also, the California
regulations allow for alternative treatment schemes for direct injection on a case-by-case basis. (CDM
Smith, 2014). Because most of the existing facilities discharge into protected groundwater aquifers not
under the direct influence of surface water, additional treatment after extraction is generally limited to
chlorination for secondary disinfection.
RO is at the heart of the full advanced treatment process and is typically preceded by microfiltration (MF)
or UF. RO pretreatment can be operationally challenging; suspended particulates can plug feed channels
in the membrane modules or damage the membrane surfaces. See Section 6.3.1 for a discussion on RO
pretreatment and other operational considerations. In water reuse applications, the typical recovery rate of
an RO system ranges from 85 to 93 percent, with higher recoveries often driven by limitations in disposal
alternatives (Chalmers et al., 2013). RO is capable of reaching TDS reductions to below 50 mg/L, total
organic carbon (TOC) reductions to less than 0.1 mg/L, and more than 99 percent removal of pathogens
and most trace chemical constituents. Some low molecular weight and volatile compounds are less readily
removed, with nitrosamine and trihalomethane removal ranging from 40 to 90 percent (CDM Smith, 2014).
A WateReuse Research Foundation (WRRF) study entitled Guidelines for Engineered Storage Systems
proposes the LRC granted to RO systems in DPR schemes should be 1.5 for viruses, Cryptosporidium,
and Giardia (WE&RF, 2016c). Studies have demonstrated that removals up to 6-log can be achieved
(EPHC, 2008). Credits granted at existing facilities have ranged from 0-log to 3-log (Wetterau et al., 2015b),
depending on the selected method of integrity monitoring and the regulatory agency responsible. For
example, the Cambria Emergency Water Supply Project in California used only conductivity to continuously
monitor RO performance and did not receive any pathogen credits. However, the Orange County
Groundwater Replenishment System (GWRS) received 2-log credits using online TOC monitoring as a
surrogate, and the Beenyup Water Recycling Plant in Perth, Australia received 3-log credits using periodic
grab samples of sulfate as a pathogen surrogate.
The cost of implementing the full advanced treatment process is fairly well-understood because of its wide-
spread application in California. The American Water Works Association (AWWA) is currently developing
M62 Manual of Practice on membrane based reuse, which will include cost curves for IPR facilities;
however, this information has not yet been publicly released. In general, treatment costs will depend on
numerous factors, including the specific site and application, the cost of source water, treatment
technologies used, plant facilities constructed, power, labor, and chemical costs, annual water production,
and many other factors. Recognizing these factors, it is possible to gain an understanding of the costs of
implementing a full advanced treatment system. Chapter 11 contains additional information on costs of full
advanced treatment systems. Interestingly, economies of scale for RO-based processes with increasing
plant size are not significant. Further, if costs for a zero-discharge concentrate disposal system are
considered, there are significant additional capital and O&M costs that nearly equal the cost of treatment
to produce AWT water.
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7.2.3.1	Plants/Projects Using Full Advanced Treatment or Related Models
Currently, five full-scale facilities in California, one in Big Spring, Texas, and three in Queensland, Australia
use California's full advanced treatment model. Four plants in Singapore, one in Perth, Australia, and one
in Wichita Falls, Texas use a modified version of the California model known as the "Singapore model" (Bell
et al., 2016b) Singapore's model uses MF, RO, and UV; but, UV only serves to reduce viruses, without
advanced oxidation, while RO is relied on to address trace chemical constituents (Bell et al., 2016b).
7.2.3.2	Water Quality
Full advanced treatment achieves a high-quality effluent using redundant barriers for pathogens and
chemical contaminants. TDS levels less than 50 mg/L are typically achieved, with TOC less than 0.5 mg/L.
Table 7-2 compares the water quality credits associated with each unit process in the California model and
the Singapore model adapted at Beenyup AWTF in Western Australia. Variations in the credits granted
between California and Western Australia relate primarily to differences in integrity monitoring approaches
used at the facilities and accepted by state regulators. In contrast, differences in total treatment
requirements relate more to the risk mitigation approaches discussed in Chapter 5. It should be noted that
pathogen reduction requirements in Western Australia must be achieved prior to injection in the
groundwater, while the California regulations allow credit for soil aquifer treatment after spreading or
injection. Table 7.4a of the Framework for Direct Potable Reuse provides additional information on
pathogen LRCs and the associated performance monitoring method for each treatment step in a full
advanced treatment train (NWRI, 2015).
Table 7-2. Comparison of pathogen and contaminant reduction in California and Western Australia
IPR approaches
Requirement
California
Western Australia
MF/UF
0 to 1 -log virus
4-log Giardia
4-log Cryptosporidium
Turbidity < 0.2 NTU
3-log virus
3-log Cryptosporidium
3-log Campylobacter
Turbidity < 0.2 NTU
RO
1 to 2-log virus
1 to 2-log Giardia
1 to 2-log Cryptosporidium
TOC < 0.25 mg/L
3-log virus
3-log Cryptosporidium
3-log Campylobacter
UV
6-log virus
6-log Giardia
6-log Cryptosporidium
4-log virus
4-log Cryptosporidium
4-log Campylobacter
AOP
0.5-log 1,4-dioxane
Not required
Total Pathogen
Requirement
12-log virus
10-log Giardia
10-log Cryptosporidium
9.5-log virus
8-log Cryptosporidium
8.1-log Campylobacter
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Chapter 7 | Alternative Treatment Trains for Potable Reuse
7.2.3,1 Costs
Many have accepted full advanced treatment and modified forms as the standard for potable reuse
treatment trains (WRRF, 2013a) as this process provides consistent, exceptional quality product water that
exceeds the quality of most conventional drinking water supplies. However, this approach can lead to very
high capital and operating costs. Also, facilities located more than a few miles from an ocean may find brine
disposal alternatives costly and challenging to permit. Inland RO facilities without an option for deep
injection wells or surface water disposal face exacerbated challenges for brine disposal; brine disposal can
at least double the capital and operating costs of an RO facility where there is no ocean for reasonably
economical disposal (Poulson, 2010; Bond & Veerapaneni, 2007). Comparative costs are summarized in
Chapter 11.
7.2.4 Ozone-BAF or the Alternative Treatmei n
Some utilities are evaluating alternative treatment trains capable of producing a similar quality product water
as full advanced treatment trains (Bell et al., 2016b). Ozone-BAF is one such alternative, providing a
potential substitute for RO, addressing trace chemical constituents without producing a brine stream (Bell
et al., 2016b).
7.2.4.1 Process 1 ption
Ozone-BAF is a simple process leveraging a combination of chemical and biological oxidation processes,
both mature treatment technologies currently widely used in drinking water treatment. The ozone-BAF
process generally consists of an ozone pretreatment step followed by biological filtration in a media filter
(Figure 7-2). Ozone is a strong oxidant, and when used in conjunction with BAF, it can remove iron and
manganese, BOD or chemical oxygen demand (COD) (including trace chemical constituents), taste and
odor compounds, color, and disinfection by-product precursors (Bell et al., 2016b; Bouwer and Crowe,
1988; Evans et al., 2010; Evans et al., 2013; Hozalski and Bouwer, 2001; Wunder and Hozalski, 2012).
During ozonation, high molecular weight organic compounds are broken down into smaller chain
compounds that are more readily biodegradable by the BAF, regardless of the composition of the filter
media.
For ozone-BAF, ozonated water is sent to a biologically "active" granular media filter. Biofiltration is a
treatment technique where the biomass on a granular media filter removes organic carbon that was made
more biodegradable through pre-ozonation. Most granular media filters are capable of supporting microbial
growth, assuming that the filtered water does not have a disinfectant residual. As a result, the biological
activity can improve treatment performance beyond particle removal; water quality is improved with respect
to a wide range of dissolved organic contaminants, including pesticides, endocrine disrupting chemicals
(EDCs), and pharmaceuticals, although the degree to which biological activity contributes to treatment
performance varies (Bonne et al., 2002; Wunder et al., 2008; Van der Aa et al., 2003). If the biofilter is not
a carbon bed, a granular activated carbon (GAC) bed may follow it for further sorptive removal.
When compared with sand or anthracite media, GAC has adsorptive properties and can accumulate greater
microbial biomass (or biofilm) due to its porosity and high surface area. Biomass is critical in biodegrading
contaminants and supplementing GAC filtration and adsorption. GAC can extend the lifetime—the time
between media replacements—because biogrowth is the main removal mechanism, not adsorption. For
example, the original GAC was installed in 2006 at the F. Wayne Hill Water Resources Center, a AWT plant
that provides water for IPR through surface water augmentation, and was still in use as of 2016.
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2017 Potable Reuse Compendium Chapter 7 | Alternative Treatment Trains for Potable Reuse
Qxyqefi
I'OplKifi fry rpuvcl
Ozone Destructor
Master PiLC
Wastewater Effluerrt
Water 5er*wJ* Signal e.g.
TOC, IW.T
T
PI Sysiero Efiaw
HE)
Water Backwash
Oxygen
Ozone Generator
Water Sensor Signal e.g.	Biologically
Dissolved 0»™, DO. Turbidity	Active FiHer —3
Water Sensor Signal e.g.
TOC UV-T. DO. Turbdity
Air Backwash
Figure 7-2. Oxelia oxidation-enhanced biologically active filtration system (courtesy of Xylem Inc.)
Depending on contact time requirements to remove target contaminants, a biofilter can be a rapid-rate filter,
a mono-media deep-bed contactor, or a GAC filter cap on top of a sand or anthracite filter bed. As with
conventional rapid-rate filters, upstream coagulants and oxidants improve contaminant removal. GAC's
adsorptive properties aid in producing the desired filtered water quality; GAC must be regenerated
periodically, particularly where adsorption may play a more dominant treatment role than the biological
mechanism of contaminant removal. Biofiltration leverages low energy biological treatment processes to
produce higher quality reclaimed water; this can make biofiltration an important component of a multi-barrier
treatment process and it may replace higher energy processes, such as RO, in certain applications. With
ozone present onsite, ozone-BAF could utilize ozone as a post-filtration disinfection process, similar to the
F. Wayne Hill Water Resources Center in Gwinnett County, Georgia (Appendix A). See Section 6.4.6 for
more information on ozone as a treatment technology.
7.2.4.2 Plants using Ozone-BAF
Drinking water treatment facilities have used ozone-BAF successfully for decades. A significant number of
drinking water utilities utilize BAFs to remove organic carbon, often to meet TOC removal requirements of
the Stage 1 D/DPR Rule. Wastewater treatment has demonstrated ozone-BAF's effectiveness at a few
notable water reclamation facilities. The longest running DPR operation, the Goreangab plant in Windhoek,
Namibia, utilizes the ozone-BAF treatment train, demonstrating that the process can operate successfully
(process details in Figure 7-1) (CORPUD, 2014). A recent Water Research Foundation project included a
survey of multiple water utilities that utilize BAF (Evans et al., 2013). Table 7-3 highlights potable reuse
facilities utilizing the ozone-BAF treatment train.
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The city of San Diego piloted a new DPR treatment train that incorporated ozone-BAF upstream of the full
advanced treatment train (Figure 7-1) (Pecson et al., 2017). The pilot system was monitored with multiple
online sensors to verify performance. This study found the pilot system "demonstrated reliable pathogen
control that met or exceeded the risk goals used by the U.S., [World Health Organization], Australia, and
other countries" (Pecson et al., 2017).
Table 7-3. Reclamation facilities using the ozone-BAF process
Project
Location
Year
Installed
(Upgraded)
Treatment Process
Treatment
Application
Scale
F. Wayne Hill
Water
Reclamation
Center
(FWHWRC)
Gwinnett
County,
Georgia
2003
(2006)
Secondary effluent —> Chemical
clarification —> Granular media filtration
—> Pre-ozonation —> GAC Filtration —>
Post-ozonation
or
Secondary effluent —> MF —> Pre-
ozonation —> BAC Filtration —> Post-
ozonation
IPR
48 MGD
Goreangab
Reclamation
Plant
Windhoek,
Namibia
2002
PAC —> Pre-ozonation —> Coagulation
/Flocculation —> DAF —> Rapid Sand
Filtration —> Ozonation —> BAC Filtration
GAC Filtration UF
Chlorination/Stabilization
DPR
5.5 MGD
Fred Hervey
Water
Reclamation
Plant (FHWRP)
El Paso,
Texas
1995
(2008)
High pH Lime addition —> Two-stage
recarbonation —> Sand Filtration —> Pre-
ozonation/Disinfection —> GAC Filtration
DPR and IPR
10 MGD
Reno-Stead
Water
Reclamation
Facility
(RSWRF)
Reno,
Nevada
2010
Phase 1: UF —> Ozone/Hydrogen
peroxide —> BAC filtration
Phase 2: Sand filtration —>
Ozone/Hydrogen peroxide —> BAC
Filtration
Reclaimed
water pilot
10.6 GPM
(Pilot)
7.2.4.3 Water Quality
Table 7.4b of the Framework for Direct Potable Reuse proposes pathogen LRCs and the associated
performance monitoring method for each treatment step in an ozone-BAF treatment train (NWRI, 2015).
Considering that ozone-BAF leverages a biofilm established on filter media, there is concern over the
potential to generate pathogenic bacteria from microbial biomass sloughing. However, research shows that
the potential is low and post-disinfection processes can sufficiently mitigate any potential microbial
breakthrough (LeChevallier et al., 1998; Evans et al., 2010; Burr et al., 2000).
One noteworthy difference between the ozone-BAF process and RO processes is that the full advanced
treatment train can reduce TOC to below 0.5 mg/L. In practice, when ozone-BAF is used in lieu of RO this
generally results in < 95 percent TOC reduction. Ozone-BAF is typically paired with other treatment trains
that can increase overall organic carbon removal, but the low TOC levels achieved with RO are difficult to
match with any other treatment scheme. However, the nature of the TOC remaining after an ozone-BAF
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Chapter 7 | Alternative Treatment Trains for Potable Reuse
process, such as an increase of assimilable organic carbon, may differ in composition from that remaining
after an RO-based process, and therefore acceptable TOC concentrations may be site-specific.
Ozone-BAF requires careful operator attention to maintain optimized ozone dosing, proper filter loading,
and sufficient backwashing. A poorly operated facility could see wide variations in product water quality;
this is a significant difference from the full advanced treatment process, where product water quality remains
relatively consistent and independent of operating conditions or operator attention.
Ozone-BAF does not remove TDS, therefore it will be limited to applications where the water's salt
concentrations are not a concern. However, ozone-BAF can be coupled with sidestream TDS removal in
certain cases to achieve local TDS requirements. In the California Groundwater Replenishment Using
Recycled Water regulations, ozone-BAF is an alternative process that requires approval on a case-by-case
basis, if accepted. Ozone-BAF is allowed in California for surface spreading operations, but full advanced
treatment is currently the only treatment train specifically approved for direct injection of reclaimed water
into groundwater (CDPH, 2014).
7.2.4,4 Costs
Because a range of treatment configurations and operational strategies perform biological filtration,
estimating capital and operating costs of ozone-BAF is more challenging than for full advanced treatment.
These variations result in a range of options for filter construction and the operational strategies for running
a BAF filter.
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2017 Potable Reuse Compendium
Chapter 8 | Source Control
CHAPTER 8
Source Control
8.1 Introduction
Source control programs are a fundamental element of the multiple barrier approach utilized in potable
reuse to protect public health. Wastewater source control programs are implemented to reduce chemical
and contaminant discharges that are difficult to remove, not specifically treated for at wastewater treatment
plants (WWTPs), or could impact the ability to meet discharge requirements. Source control programs for
potable reuse must appropriately address industrial and commercial discharges to protect the treatment
processes, public health, and downstream infrastructure and the environment. Figure 8-1 illustrates the
interaction of these goals for direct potable reuse (DPR) (FCM and NRC, 2003). These three goals are
central to the operation of a successful wastewater source control program; but, not all entities currently
exploring potable reuse have existing or approved pretreatment or source control programs.
Protect
Public Health
Source
Control
for DPR
Protect
Environment
and Infrastructure
Protect
Treatment Plant
Processes
Figure 8-1. Fundamental goals of a DPR source control program
8.2 Elements for Potable Reuse - Source Control Program
An important question to consider for a potable reuse project is whether existing source control measures,
designed solely for wastewater agencies discharging to ambient waters, are appropriately designed for
facilities with a direct or indirect connection to a public drinking water system. Potable reuse source control
programs are essential components of the multiple barrier approach implemented to ensure consumer
safety and acceptability of potable reuse water. Therefore, there is likely a need for enhanced source control
programs for potable reuse, and potentially a need for enhanced source control programs when DPR is
employed (CUWA et al., 2010). Potable reuse source control programs may not remove all unwanted
publicly owned treatment work (POTW) pollutants. Therefore, programs should reduce problematic and
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measurable constituents, identify contributing sources, and determine where contributing sources are within
the management agency's control. Figure 8-2 presents the overall structure of a potential potable reuse
source control program. Table 8-1 gives further details regarding the specific content of program elements.
1 Evaluation of Wastewater Sewer Service Area
Critical
Components	Discharge Characteristics Assessment
of a Source
Control
Program for	3 Educational Awareness and Public Outreach Program
Potable	a
Reuse
4 Sewer-Use By-Laws and Best Management Practices
5 Enforcement and Response
Figure 8-2. Critical components of a source control program for potable reuse
Table 8-1. Specific content of potable reuse source control program elements (Adapted from FCM
and NRC, 2003)
Source Control Program Element Specific Content
Evaluation of Wastewater Sewer Service
Area
¦	Identify potential 'pass-through' and 'interference' constituents
specific to the sewer service area in order to evaluate local limits
for necessary constituents
¦	Prioritization of constituents
¦	Assessment of technical limits for regulated constituents and
contaminants of emerging concern
Discharge Characteristics Assessment
¦	Database of chemicals stored or discharged by industrial users
¦	Hauled waste inventory
Educational Awareness and Public
Outreach Program
¦	Quantity control
¦	Quality control
¦	Information on proper disposal methods
¦	Incentives program
¦	Pollution prevention program/seivice-area wide stewardship
programs
Sewer-Use By-Laws and Best
Management Practices
¦	Prohibited Wastes
¦	Restricted Wastes
¦	Discharge permits
¦	Best Management Practices
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Chapter 8 | Source Control
Source Control Program Element
Specific Content
Enforcement and Response
¦	Routine monitoring program
¦	Response plan for pollutant concerns
¦	Flow trace of pollutants to industrial user source using geometric
network
¦	Enforcement response plan for non-compliance
8.2.1	California's IPR Source Control Program Requirements
The California Groundwater Replenishment Using Recycled Water regulations require a source control
program for recycled municipal wastewater (see CDPH, 2014). The source control program includes
multiple requirements: a fate assessment of specific wastewater and recycled municipal wastewater
chemicals and contaminants; specific chemical and contaminant source identification and monitoring; an
industrial, commercial, and residential outreach program; and an inventory of specific chemicals and
contaminants (CDPH, 2014).
8.2.2	DPR Source Control Program Elements
Typically, an effective DPR source control program includes six principle elements: "(1) regulatory authority;
(2) monitoring and assessment of commercial and industrial dischargers to the wastewater collection
system within the service area; (3) investigation of chemical and other constituent sources; (4) maintenance
of the current inventory of chemical constituents; (5) preparation of a public outreach and participation
program; and (6) preparation of a response plan for water quality deviations." (NWRI, 2015)
8.3 National Pretreatment Program
The National Pretreatment Program controls and regulates commercial and industrial wastewater
discharges to POTWs (EPA, 2011). This program was not designed to address potable reuse systems. A
more rigorous source control program, in conjunction with the National Pretreatment Program, is an
important consideration in potable reuse planning to eliminate or control discharges that might impact the
reliable treatment of water used for potable reuse.
The following POTWs must develop pretreatment programs: 1.) POTWs receiving pollutants from industrial
users that may pass through or interfere with operations or are otherwise subject to pretreatment standards;
and 2.) POTWs with a design capacity greater than 5 million gallons per day (MGD) (40 CFR 403.8).
WWTPs with a capacity less than 5 MGD may be required to develop a pretreatment program (40 CFR
403.8).
Industrial discharges can potentially interfere with POTWs by upsetting treatment processes and/or sludge
and biosolids operations. In addition to interferences, industrial pollutants discharged into the collection
system and POTW may pass through all treatment processes and ultimately be discharged to surface
water, sludges, or air emissions. POTWs are not designed to provide significant removal of some toxic
chemical pollutants (EPA, 2011); pollutants passing through POTWs can result in aquatic life or human
health impacts, including contamination of sludges initially intended for beneficial reuse.
Local municipalities and agencies also require additional source control regulations that protect the POTW
or local environment. An approved pretreatment program frequently incorporates limits identified by local
authorities (40 CFR 403.5(c)). For example, the City of Los Angeles has local limits on the amount of
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Chapter 8 | Source Control
industrial pollutants discharged into the sewer, which includes arsenic, metals, and other materials that
could degrade the effluent (SDLAC, 2017).
National Pollutant Discharge Elimination System (NPDES) regulations (40 CFR 122.44(i)) require that
POTWs periodically measure influent, effluent, and biosolids for pollutants of concern. Chemicals such as
polychlorinated biphenyls (PCBs), pesticides, and phenolic compounds are often locally regulated from
industrial discharges; these types of chemicals may impact the performance of some advanced removal
technologies (e.g. foulant) as well as public acceptance of a potable reuse water program.
Nitrogen and TDS have potential negative impacts on a membrane treatment program if not controlled by
a potable source control program. Higher TDS increases the pressure required for reverse osmosis (RO)
treatment, impacting electric power usage and cleaning cycle frequency. Nitrogen compounds can impact
reservoir discharge limits; higher nitrogen could also contribute to algal blooms or taste and odor issues in
IPR situations (NRC, 2012a).
Orange County's GWRS includes local limits for potable reuse source control. Certain discharges may not
enter the GWRS through the Orange County Sanitation District's wastewater collection system; this
includes discharges from the Stringfellow Superfund site. Discharges from the Stringfellow Superfund site
are non-reclaimable flow that cannot be recycled. Because of the public concern associated with Superfund
site discharges in the IPR project, the wastewater agency made revisions to their collection and wastewater
treatment systems to ensure the GWRS would not receive this water.
8.4	Pollution Prevention
Pollution Prevention (P2), a national objective enacted with the Pollution Prevention Act of 1990, and source
control can complement one another. P2 objectives are built into EPA regulatory guidelines (EPA, 2011)
and in some state and local agency guidelines. The main objectives of P2 Programs are to prevent pollution
from occurring at the source, encourage the use of non-toxic or less toxic substances, and actively conserve
natural resources (EPA, 2011). The P2 Program encourages the quantification of POTW influent pollutants
to identify the source(s) of a pollutant or pollutant concentration and to determine pollutant loading.
8.5	POTW Chemical Impacts on Reuse Facilities
Chemicals and materials used at a POTW may also impact the suitability of influent water for a potable
reuse facility. POTWs can reduce costs and simplify or improve wastewater treatment and reuse
performance by avoiding cross-contamination from difficult-to-treat chemical compounds. Segregating
processes at the wastewater plant can minimize the impact of these materials by either bypassing the reuse
plant connection, allowing for pretreatment of that key contaminant, or switching to another chemical.
For example, Mannich polymer is a chemical often used at POTWs to aid settling in the sludge dewatering
process. When the dewatering side streams are discharged back into the POTW, trace amounts of this
compound can enter the downstream potable reuse facility in the influent water. Mannich polymer is known
to increase N-nitrosodimethylamine (NDMA) formation and is a possible foulant to the RO membranes. If
possible, even trace amounts should be eliminated from the influent stream.
NDMA forms in water treatment plants (WTPs) when chloramines react with dimethylamine (DMA), a
constituent of the Mannich polymer (Huitrich et al., 2006). Hutrich et al. (2006) evaluated two alternatives
for minimizing NDMA formation during chloramination: breakpoint chlorination while using Mannich polymer
and chloramination while using emulsion polymers without DMA. Laboratory and full-scale tests were
performed "to evaluate disinfection efficacy and formation of NDMA and trihalomethanes (TTHM) with these
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alternatives" (Huitrich et al., 2006). The emulsion polymer alternative produced much lower NDMA levels
than the Mannich polymer scenario, but it was less effective as a settling mechanism (Huitrich et al., 2006).
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2017 Potable Reuse Compendium
Chapter 9 | Environmental and Engineered Buffers
CHAPTER 9
Environmental and Engineered Buffers
9.1 Environmental Buffers
An environmental buffer refers to an aquifer, wetland, or other body of water such as a river, stream, lake,
or reservoir, that serves as an intermediate discharge and holding point within a potable reuse scheme.
The environmental buffer receives treated water from an advanced wastewater treatment facility (AWTF).
Dilution, blending, and some contaminant removal through filtration (aquifers), photolysis (surface waters),
or biological degradation can occur before indirect potable reuse (IPR) withdrawal (Figure 9-1) (WE&RF,
2016c). Environmental buffers tend to dissociate the origin of the water (wastewater discharge) from the
end-point (drinking water); environmental buffers also create a window of time in which the water enters
into a natural environment (Khan, 2013). Although environmental buffers can improve water quality, they
are not a universally required component in potable reuse projects, and they do not conform to controlled
performance standards (Khan, 2013). In fact, some environmental buffers may degrade the quality of
purified water; including risks of surface water contamination.
Water Treatment
Facility/Drinking
Water
Distribution
I
Figure 9-1. Environmental buffers in potable reuse treatment schemes
An environmental buffer's importance to public health largely depends on the influent water quality and the
buffer's specific characteristics. For example, reclaimed water that undergoes advanced treatment
upstream of the environmental buffer may have less stringent dilution and residence time requirements
than reclaimed water that only undergoes filtration and disinfection (WE&RF, 2016c). Two types of
environmental buffers, aquifers and surface storage, are discussed herein.
9.1.1 Aquifer Recharge
Aquifers can serve as subsurface environmental buffers. In this approach, treated effluent is either diverted
to surface spreading basins whereby infiltration occurs, or used in more modern approaches such as rapid
infiltration basins, vadose zone injection wells, infiltration trenches, or riverbank filtration to reach the water
table. Reclaimed water percolates through sediment until it reaches the aquifer and blends with
groundwater; it remains underground for a predetermined residence time before being extracted as a
drinking water source. The process of enhancing natural groundwater supplies using engineered
conveyances to route water to an aquifer is known as managed aquifer recharge (MAR), and in a number
Advanced Water
Reclamation
Facility
Environmental Buffer
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of cases in near coastal areas, MAR has also helped to reduce saltwater intrusion. Purified water sent to a
spreading basin undergoes a natural water treatment process known as soil aquifer treatment (SAT). As
opposed to full advanced treatment (discussed in Chapter 7), SAT does not result in the generation of a
brine requiring disposal and provides additional pathogen removal, therefore making it a popular option for
inland geographies. Lab analysis of soil columns can assess the removal of pathogens, such as
Cryptosporidium, through SAT. Field studies using actual Cryptosporidium are relatively rare due to low
oocyst concentrations, even in raw surface waters. Field studies typically utilize surrogates, such as
bacterial spores or microspheres, to assess log removal of pathogens through SAT (WRRF, 2015a). SAT,
given a suitable aquifer, is considered the most economical potable reuse alternative. The WateReuse
Research Foundation (WRRF) completed a study, titled Enhancing the Soil Aquifer Treatment Process for
Potable Reuse, that investigated two alternative treatment trains for potable reuse using SAT, one involving
chlorine disinfection and the other involving ozone disinfection. Findings from this study indicated that SAT
is an effective and natural treatment option (WRRF, 2015a). The level of treatment achieved through aquifer
recharge depends on the quality of the feed water. There is the possibility of water quality degradation;
blending high quality feed water with groundwater that was exposed to municipal, agricultural, industrial,
and natural contaminants can result in added treatment requirements when the water is extracted (WE&RF,
2016c). Aquifer storage and recovery (ASR) is a specific type of MAR practiced to augment groundwater
resources and recover the water in the future for various uses (EPA, 2012a). In the United States, ASR is
used frequently as a method of improving water availability during droughts, and offsetting water shortages;
ASR projects that utilize underground injection require an underground injection control (UIC) permit (EPA,
2017m). Most of the current U.S. ASR practices are utilized in non-potable water and wastewater reuse
applications intended for irrigation, industrial, and urban landscape end uses; however, ASR for IPR has
recently increased in popularity (EPA, 2017m). As mentioned in Chapter 7, for a technical report on
principles involved in ASR, as well as tools and methods for ASR system planning, assessment, design
and evaluation, referto EPA's Decision Support System for Aquifer Storage and Recovery (ASR) Planning,
Design and Evaluation- Principles and Technical Basis (EPA, 2017m).
9.1.2	Surface Water Storage
Surface water storage occurs when reclaimed effluent is discharged into a lake, reservoir, or river. In this
instance, the receiving surface water blends with reclaimed water before being extracted and sent to the
water treatment plant (WTP). Surface water storage provides a mitigation response time in the event of
process failure, and can provide a level of treatment; however, the effectiveness of treatment depends on
the water quality of the reclaimed effluent, and the water quality and environmental conditions of the surface
water (WE&RF, 2016c). Surface water storage can be a limiting factor in IPR operation implementation,
because a viable location for the surface water storage may not exist in all situations (Khan, 2013).
Interestingly, even if the surface water storage exists, there can be utilization challenges. As mentioned
above, contamination risks can be challenging with surface water. Also, storage and withdrawal contracts
can be contentious for surface water sources, as illustrated in the Gwinnett County case study (Appendix
A).
9.1.3	Wetlands
There are numerous examples of using wetlands as "environmental buffers." Many of these facilities, such
as in Clayton County, Georgia, discharge treated effluent into a constructed treatment wetland system to
recharge the water supply (CCWA, 2017). Constructed wetlands rely on aquatic ecosystem components to
filter and biologically treat the water that flows through them; these components include soils, plants, and
bacteria. Constructed wetlands can serve as a treatment process for potable reuse applications; but, storing
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treated water in a natural wetland could contribute additional total organic carbon (TOC) to the treated water
and make WTP treatment significantly more challenging.
9.1.4	Fate and Transport of Pathogens in Subsurface Environmental Buffers
As discussed in Chapter 4, wastewater pathogens may pose acute or sometimes chronic risks to public
health. Environmental buffers can remove pathogens by sieving, sorption, predation, and subsequent die-
off in soil and subsurface media. Pathogen removal is most efficient in granular (sand) media subsurface
environments as opposed to non-porous media dominated environments, such as bedrock (e.g. basalt).
Site-specific conditions, including soil saturation and aquifer flow type (porous or non-porous media), media
composition, groundwater pH, and microorganism type and strain all interact to affect the removal capacity
and die-off rate in soils and aquifers.
Pathogen concerns resulted in the implementation of residence and travel time requirements for
environmental buffers in systems with potential hydraulic connectivity to drinking water supplies or in IPR
schemes. Travel times are average values, and some groundwater takes a faster path and arrives sooner
than the average. Porous media aquifers have the most accurately calculated travel times. In non-porous
media aquifers, travel times are best determined using site-specific field tracer tests. For IPR systems in
California, travel time requirements range from 2 to 12 months, depending on the percentage of reclaimed
water in the planned IPR system. In 2009, Massachusetts adopted a six-month travel time requirement for
environmental buffers in IPR systems. Although New York does not have water reuse guidelines, the State
Sanitary Code (November 2011) requires that all new and existing effluent discharges to groundwater
systems have a 60-day travel time or more from the point of discharge to the point of intake (NYCRR Title
10, 2011).
9.1.5	Fate and Transport of Trace Chemical Constituents in Environmental
Buffers
As presented in Chapter 4, wastewater from properly well-operated publicly owned treatment works
(POTWs) contains a wide variety of chemicals including trace chemical constituents that are generally
present at nanogram per liter concentrations (ng/L) or less. Trace chemical constituents can include
pharmaceutical^ active compounds and personal care and consumer product additives; they are the
subject of numerous wastewater treatment and environmental removal studies (Wells et al., 2008, 2009,
2010; Bell, et al., 2011, 2012, 2013; Keen et al., 2014).
A combination of mechanisms can remove trace chemical constituents during subsurface transport,
including sorption and biodegradation. Bulk organic matter components such as natural organic matter
(NOM) and soluble microbial products (SMPs) are "reduced during subsurface transport as high-molecular-
weight compounds are hydrolyzed into lower-molecular-weight compounds and the lower molecular weight
compounds serve as a substrate for microorganisms" (NRC, 2008). Synthetic organic compounds with
"concentrations too low to directly support microbial growth may be co-metabolized, as NOM and SMPs
serve as the primary substrate for growth" (NRC, 2008). During subsurface transport, the transformation of
organic compounds falls into two categories of either relatively fast, short-term transformations, or slow,
long-term transformations (NRC, 2008). Easily biodegradable carbon transforms within a timescale of days
and when transport paths are sufficiently long; providing longer retention times in the subsurface allows
organic compounds to transform. The variability of influent trace chemical concentrations to subsurface
environments could be temporally or seasonally dependent (Hinkle et al., 2005). Biodegradation rates
increase with warmer temperatures.
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Easily biodegradable trace chemical constituents, such as caffeine and 17p-estradiol, tend to degrade on
a timescale of days, while more refractory compounds, such as N-nitrosodimethylamine (NDMA) and
sulfamethoxazole, tend to degrade over a timescale of weeks to months (Dickenson et al., 2008). Persistent
compounds, such as carbamazepine and primidone, can persist for months or years in the subsurface
(Clara et al., 2004; Heberer, 2002). The transformation of organic trace chemical constituents can depend
on the presence of biodegradable dissolved organic carbon because the concentrations of constituents of
concern are very low and may not support growth (Rausch-Williams et al., 2010; Nalinakumari et al., 2010).
The various removal mechanisms of trace chemical constituents in subsurface environments are discussed
below. It is important to emphasize that site-specific conditions govern removal rates.
9.1.5.1	Biociegraciation
Aerobic microbial reactions that occur underground preferentially use oxygen as the terminal electron
acceptor due to energy requirements. Higher levels of oxygen result in microbial community growth that
can attenuate chemical contaminants. Anaerobic biodegradation can also occur; however, aerobic
conditions can enhance trace chemical constituent removal (Conn et al., 2010; Swartz et al., 2006; Carrara
et al., 2008; Schaider et al., 2013; Teerlink et al., 2012; Heufelder, 2012).
9.1.8.2	Sorption and to hange
Sorption is another key mechanism governing the subsurface attenuation of trace chemical constituents.
Factors affecting sorption include the hydrophobicity of the trace chemical, the organic matter present in
the soil, the acid dissociation constant (pKa), and the soil pH (Schaider et al., 2013). If a chemical has a
net negative charge in the soil, it is more likely to remain in solution because certain soil constituents (e.g.
clay particles) also have a net negative charge (Schaider et al., 2013). Refer to the WateReuse Research
Foundation (WRRF) project Enhancing the Soil Aquifer Treatment Process for Potable Reuse for further
information on laboratory soil column studies assessing the key mechanisms governing subsurface
attenuation of trace chemical constituents and pathogens (WRRF, 2015a).
Ion exchange is the soil's capacity to hold exchangeable ions at a given pH value. The acid dissociation
constant and soil pH determine the ionization state of a given chemical, which affects sorption due to ion
exchange.
9.2 Engineered Storage
Engineered storage is an additional approach in direct potable reuse (DPR) systems designed to provide
capacity to manage fluctuations in water supply, water quality, and demand. An engineered storage reuse
scenario is classified as DPR because there is no discharge to a natural water body. The number of facilities
utilizing engineered storage in lieu of environmental buffers remains extremely limited to date. Engineered
storage provides the appropriate residence time to allow adequate monitoring of the reclaimed effluent
before discharging to the WTP or drinking water distribution system (Figure 9-2) (WRRF, 2011a).
Characteristics of an environmental storage buffer (ESB) may include the following: full control over the
ESB environment, exclusion of contaminants from the surrounding environment, flow diversion and/or
equalization, designed monitoring and sampling equipment, and optimized hydraulics (Khan, 2013). ESB
construction can be costly and may not provide the same natural treatment associated with environmental
buffers. There are multiple examples of ESB structures (stand-alone or integrated within the distribution
system): large subsurface pipelines, constructed aquifers, enclosed subsurface storage reservoirs, lined
and covered surface storage reservoirs, and above ground tanks (WRRF, 2011a). In all cases, ESB design
depends on site-specific constraints and safety requirements (WRRF, 2011a). ESBs require proper sizing
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and water quality parameter monitoring. To provide further treatment, an ESB can use chlorination or
ozonation so long as residual monitoring occurs (WE&RF, 2016c). In instances where the DPR treatment
train has relatively short failure response times (FRTs), disinfectant dosing may determine the ESB's size
and design. This concept is described further in Section 9.4.
Advanced
Wastewater
Treatment
Facility
Engineered Storage
Buffer
Water Treatment
Facility/Drinking
Water
Distribution
Figure 9-2. Engineered storage buffers in potable reuse treatment schemes
9.3	Response Time in Buffers
Response time is the time required to evaluate monitoring results and respond to a treatment failure before
affecting the downstream water quality. There is an associated response time for each unit process and its
applicable monitoring procedure (WE&RF, 2016c). Response time is one of the most significant factors in
DPR system design, because a loss of response retention time may occur in the absence of an
environmental or engineered buffer (WE&RF, 2016c). ESB functions incorporate response time.
Additionally, DPR treatment systems require advanced monitoring techniques. Rapid, online, and real-time
monitoring could serve as tools to protect public health; these tools enable the system operator to observe
off-specification water and mitigate accordingly (Khan, 2013).
The Water Environment & Reuse Foundation's (WE&RF's) Guidelines for Engineered Storage for Direct
Potable Reuse studied the FRTs for common unit processes and found that advanced monitoring
techniques may drastically reduce the FRT. For example, standard monitoring approaches (direct integrity
testing) for microfiltration membranes result in a FRT of 24+ hours; conversely, advanced monitoring
techniques such as bioscans and particle counting can reduce the FRT for bacteria to minutes and protozoa
to hours (WE&RF, 2016c). The log removal credit process can account for both sensitivity of monitoring
techniques (actual reduction confirmed through monitoring) and the known process efficiency (actual
proven reduction per unit process) (WE&RF, 2016c). For example, the FRT for reverse osmosis (RO)
systems in DPR treatment trains is on the order of minutes using standard or advanced monitoring
technologies. However, standard monitoring tests would result in a log removal credit of less than 2-log,
whereas advanced monitoring tests could increase the log removal credit to between 4 and 6-log (WE&RF,
2016c).
9.4	Replacing the Value of the Environmental Buffer
Much of the literature regarding potable reuse and environmental buffers focuses on the buffer's role when
it receives filtered and disinfected waters (WRRF, 2014e). The literature does not expand on the impact of
an environmental buffer on high quality water, such as full advanced treatment and/or RO permeate
(WRRF, 2014e). Risk Reduction for Direct Potable Reuse concludes that a process that can remove an
additional 60% of trace chemical constituents and achieve a 5-log reduction of both viruses and protozoa
is required to replace the environmental buffer's treatment value (WRRF, 2014a). While an additional level
of treatment can offset the treatment effectiveness of an environmental buffer, it does not address the loss
in response time from a process upset. A higher level of automation and monitoring or an engineered
storage buffer can offset the loss in response time. Real time or near real time monitoring can potentially
serve as a critical strategy in replacing the value of the environmental buffer.
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Chapter 10 | Training, Operating, and Monitoring
CHAPTER 10
Training, Operating, and Monitoring
Operator training and certification is critical for the protection of public health and the maintenance of safe,
optimal, and reliable operations of wastewater and water treatment plants and distribution facilities. EPA's
role in operator certification is primarily related to providing tools, training, and guidance that is implemented
by authorized states. There are no specific operator certification requirements outlined in the Clean Water
Act (CWA); but, many state agencies have operator training and certification requirements for publicly
owned treatment works (POTWs). The Safe Drinking Water Act (SDWA) contains requirements for drinking
water plant training and operator certification; this chapter outlines some of the relevant requirements for
potable reuse implementation. The chapter also covers key operations issues, such as hazard analysis and
the establishment and monitoring of critical control points, start-up and commissioning, operation and
maintenance (O&M), optimization of plant operations, and other monitoring considerations. This chapter
does not specifically outline operator training requirements for advanced wastewater treatment facility
(AWTF) operations in a potable reuse scenario. Instead, this chapter outlines the existing operator training
and certification framework that exists within the CWA and the SDWA, and how these existing concepts
may apply to AWTFs.
10.1 Operator Training and Licensure
The requirements for water treatment plant (WTP) operators could serve as an excellent guideline for the
requirements for AWTF operators because the processes are similar. The staff that operates AWTFs for
potable reuse should have extensive knowledge and skills regarding the design, management, and
treatment processes used in the potable reuse system. Accredited training and certification programs will
likely be a mandatory aspect of indirect potable reuse (IPR) and direct potable reuse (DPR) schemes. Thus,
it is useful to examine the drinking water operator certification requirements in the context of potable reuse.
The 1996 SDWA amendments directed EPA on multiple operator-related issues:
•	Initiate a partnership with states, water systems, and the public to develop information on
recommended operator certification requirements.
•	Issue guidelines for minimum operator certification and recertification standards in community
water systems (CWSs) and nontransient, noncommunity public water systems (NTNCWSs).
•	Reimburse, through grants to the states, training and certification costs for operators of CWS and
NTNCWS systems serving 3,300 persons or fewer.
Subsequently, two EPA convened workgroups addressed issues related to operator certification and
formulated specific program guidelines. EPA published the workgroups' nine baseline standards in Final
Guidelines for the Certification and Recertification of Operators of Community and Nontransient
Noncommunity Public Water Systems (1999a):
1.	Authorization.
2.	Classification of Systems, Facilities, and Operators.
3.	Operator Qualifications.
4.	Enforcement.
5.	Certification Renewal.
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6.	Resources Needed to Implement the Program.
7.	Recertification.
8.	Stakeholder Involvement.
9.	Program Review.
Licensed wastewater operators operate AWTFs. Currently, AWTF operators do not require a separate
category of licensure or training. But, the AWTF processes require a different operator focus than
wastewater treatment facilities. Additionally, most of these AWTFs are used in IPR applications, meaning
licensed drinking water operators are responsible for the final treatment and distribution of the water
downstream of the environmental buffer. Similarly, the two DPR facilities operated in Texas (Big Spring and
Wichita Falls) include downstream drinking water plants operated by licensed drinking water operators.
Many states have separate certification programs for water and wastewater operators, creating
complications for the type of certification needed for the operation of a potable reuse facility.
As potable reuse plants become more common and the transition point between advanced wastewater
purification and drinking water processes becomes less defined, requirements for operator training will need
to evolve. Operator training must ensure that proper safeguards and procedures are maintained for
monitoring and controlling water with potentially unique public health risks. Several organizations and state
regulatory agencies are evaluating or developing operator training and licensure for AWTF facilities or for
unit processes pertinent to AWTF. The Southeast Desalination Association, which provides operator
training in the southeastern United States, developed membrane operator certification courses for reverse
osmosis and nanofiltration plants, as well as a general certification course on membrane systems. These
curricula were adapted by the South-Central Membrane Association (SCMA) and the Southwest Membrane
Operator Association (SWMOA), providing training and certification for operators throughout the southern
and western regions of the United States. In addition, SCMA developed a certification course focused on
low pressure membranes (microfiltration and ultrafiltration), while SWMOA is developing certification
training for operators of membrane bioreactors. California is currently evaluating whether to require a new
type of operator certification for the operation of AWTFs used in potable reuse schemes. The California-
Nevada American Waterworks Association is developing an operator certification program for water reuse
facilities. The Wichita Falls case study in Appendix A describes how the city developed additional operator
requirements when its DPR facility came online. A Water Environment and Reuse Foundation (WE&RF)
study titled Development of Operation and Maintenance Plan and Training and Certification Framework for
DPR Systems developed a framework for uniform training and certification requirements in DPR schemes
(WE&RF, 2016a). It may not be essential to establish a uniform nationwide certification program for all
AWTFs; but, it is clear that some portion of the treatment process will include drinking water treatment
certification. Furthermore, developing training material and certification criteria can aid operators in
understanding the critical nature of treatment barriers and the uniqueness of potable reuse treatment
technologies.
10.2 Hazard Analysis and Critical Control Points (HACCP)
The Hazard Analysis and Critical Control Points (HACCP) approach is one proposed method for informing
AWTF operations under the CWA and the SDWA. This approach was developed to prevent gastrointestinal
illness in astronauts in the 1960's. It was subsequently adapted in the food industry to ensure food safety
(FDA, 2017). HACCP can apply to potable reuse systems the same way it applies in other industries, such
as aviation. But, it is important to note that HACCP is not a full risk assessment framework, but just one
piece of a complete risk mitigation framework.
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HACCP includes five pre-steps and seven steps. The five HACCP pre-steps include the following:
1.	Assemble the HACCP team.
2.	Describe the product.
3.	Identify intended use.
4.	Construct a flow diagram.
5.	On-site confirmation of flow diagram.
There are seven steps in HACCP (FDA, 2017):
1.	Hazard Identification - Characterize the wastewater, recognize constituents that may pose adverse
health effects if not treated properly, assess the necessary (or mandated) log-removal values and
allocate them amongst individual treatment processes.
2.	Critical control point identification and design - Identify critical control points within each unit
process and within the process as a whole.
3.	Critical limits set - Identify a mechanism for measuring performance utilizing easily measurable
parameters such as indicators and surrogates.
4.	Monitoring system design and installation - Determine the components of the monitoring system
that will be used to measure performance at the critical control points identified in step two.
5.	Corrective actions planned and practiced - Establish an operational plan for mitigating local failures
(i.e. performance criteria not met) and a plan for system failures.
6.	Verification validation - Ensure quality assurance and quality control by outlining a framework for
third-party verification and process validation.
7.	Documentation - Document and develop recordkeeping systems.
HACCP is a widely-used approach for identifying hazards in order to control, minimize, and lessen the
impact of system failures, and many variations of it have developed over the years (WRRF, 2014c). A 2014
WateReuse Research Foundation (WRRF) study titled Utilization of HACCP Approach for Evaluating
Integrity of Treatment Barriers for Reuse proposes a HACCP outline for potable water reuse treatment. The
National Research Council's 2012 document titled Water Reuse: Potential for Expanding the Nation's Water
Supply Through Reuse of Municipal Wastewater also outlines a potable reuse approach for HACCP (NRC,
2012a). The WE&RF (2016b) study Critical Control Point Assessment to Quantify Robustness and
Reliability of Multiple Treatment Barriers of a DPR Scheme will conduct a hazard assessment for key unit
operations and determine the critical control points of DPR schemes. Additionally, the World Health
Organization (WHO) published a framework for a water safety plan that closely follows the HACCP
concepts (WHO, 2009).
10.3 Start-up, Commissioning, and Initial Operation
During AWTF start-up, each component of the treatment train is tested separately, in combination with other
key components, and finally as a complete treatment train. Each component's mechanical performance
and produced water quality are verified. During the facility's initial months of operation, operations staff
remain in close communication with equipment manufacturers and other third-party professionals to modify
on-site conditions and ensure performance targets are met. In states where the project needs permit
approval before operating, such as California, regulators review start-up data and visit the facility during
commissioning. The facility should have a written standard operating procedure (SOP) review and SOP
operator training.
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10.4 Ongoing Operation and Maintenance
Primacy states must have "a systematic program for conducting sanitary surveys of public water systems
in the State, with priority given to sanitary surveys of public water systems not in compliance with State
primary drinking water regulations" (40 CFR 142.10(b)(2)). In the Interim Enhanced Surface Water
Treatment Rule (IESWTR) (EPA, 1998a), a sanitary survey is defined as:
"an onsite review of the water source (identifying sources of contamination using results of source
water assessments where available), facilities, equipment, operation, maintenance and monitoring
compliance of a public water system to evaluate the adequacy of the system, its sources and
operations and the distribution of safe drinking water."
Conducting sanitary surveys on a routine basis is an important element in preventing contamination of
drinking water supplies. Sanitary surveys provide an opportunity for the primacy agency to visit the water
system and educate the operator about proper monitoring and sampling procedures and to provide
technical assistance. Sanitary surveys are a proactive public health measure and an important component
of the SDWA public water system supervision program (EPA, 2017t). The IESWTR requires that a sanitary
survey addresses eight elements: source; treatment; distribution system; finished water storage; pumps,
pump facilities, and controls; monitoring and reporting and data verification; system management and
operation; and operator compliance with state requirements. IESWTR describes the timing for sanitary
surveys (EPA, 1998a):
"The State must complete sanitary surveys for all surface water systems and [ground water under
the direct influence of surface water] no less frequently than every three years for community
systems and no less frequently than every five years for non-community systems.... The rule also
provides that for community systems determined by the State to have outstanding performance
based on prior sanitary surveys, successive sanitary surveys may be conducted no less frequently
than every five years. In its primacy application, the State must include: 1) how it will decide whether
a system has outstanding performance and is thus eligible for sanitary surveys at a reduced
frequency, and 2) how it will decide whether a deficiency identified during a survey is significant."
While the references herein specifically address surface water sources, there are also requirements for
groundwater sources. The Ground Water Rule (GWR) requires states to conduct sanitary surveys for all
groundwater sources to identify significant deficiencies, including deficiencies that could make a system
susceptible to microbial contamination. Following the initial sanitary survey, states must conduct surveys
every 3 years for community water systems (CWSs) (with allowance up to every 5 years depending upon
the system's performance and state's evaluation) and every 5 years for non-community water systems
(NCWSs) (EPA, 2006c).
AWTFs should have a regularly updated "living" operations plan that clearly identifies the roles and
responsibilities of each staff. The plan should describe communication and decision-making procedures,
provide a basic overview of the facility and the treatment unit processes, acceptable operating ranges for
key processes, and contingency plans for process deviations or failures. For an example of an operations
plan manual from the Orange County Water District in California, refer to National Water Research Institute
(NWRI) section 11.6.2 (NWRI, 2015).
AWTFs need a facility maintenance strategy that includes an asset management program with software to
track maintenance; this is a key component of avoiding equipment failure and protecting of public health.
The facility needs a robust maintenance team to ensure proper operation of all conveyance, treatment, and
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monitoring equipment. Periodic evaluation of facility operations could help provide a greater level of public
acceptance for potable reuse.
10.5	Optimization and Improvement
Many AWTFs continually evaluate new technologies through an active program to identify and test new
chemicals, processes, equipment, or tools to improve performance. AWTFs should carefully consider the
protection of public health when changing operational practices.
Maintaining public health protection at water supply systems has become more challenging in recent years
due to the resistance of some pathogens to chlorination and an increase in the immuno-compromised
population (e.g., people with HIV, organ transplant patients). Also, as evidenced by documented pathogen
occurrence, compliance with the 1989 Surface Water Treatment Rule (SWTR) and Total Coliform Rule
(TCR) did not always assure public protection from waterborne disease. Based on this awareness, EPA
developed new regulations to enhance control of microbial pathogen contamination in drinking water, while
concurrently addressing other concerns such as disinfection by-products (DBPs). This interrelated
regulation approach is moving the water supply industry toward meeting increasingly more complex water
treatment requirements.
In 1988, the Composite Correction Program (CCP) was developed and demonstrated as a method of
optimizing surface water treatment plant performance for protection from microbial contamination. This
approach is based on the effective use of available water treatment process barriers against particle
passage to the finished water. The program uses specific performance goals to define optimum
performance for key treatment process barriers such as sedimentation, filtration, and disinfection. The CCP
consists of two components - a Comprehensive Performance Evaluation (CPE) and Comprehensive
Technical Assistance (CTA). A CPE is a thorough review and analysis of a plant's performance-based
capabilities and associated administrative, operation, and maintenance practices. It identifies factors that
may be adversely impacting a plant's ability to achieve permit compliance without major capital
improvements. CTA is the performance improvement phase that is implemented if the CPE results indicate
improved performance potential. During the CTA phase, identified plant-specific factors are systematically
addressed and eliminated (40 CFR 142.16(g)(1)).
A similar approach, in complement with existing CCPs and CPEs for wastewater treatment plants
(WWTPs), could apply to AWTFs that produce source water for drinking water treatment plants to provide
optimized treatment processes and proactively identify and resolve maintenance issues.
10.6	Process Control and Monitoring
The transformation of municipal wastewater to a high-quality drinking water supply involves rigorous
process control and monitoring protocols to ensure continuous public health protection. The purpose of
monitoring is to assess process performance and trigger alarms if there is a change in normal operating
conditions from a pathogen or chemical constituent outlook. Online real time and offline monitoring of
potable reclaimed water is essential to protecting public health. Monitoring is already required for both
wastewater treatment plants (WWTPs) and WTPs under the CWA and the SDWA, respectively.
Though existing advanced treatment processes are fully capable of producing a comparable, if not superior,
water quality when compared to existing drinking water supplies, the response time for failure mitigation is
inevitably shorter in DPR schemes. Therefore, accurate and robust monitoring and process control
technologies are fundamental priorities during project development. While process control and monitoring
are identified as key elements in advancing potable reuse, and many ongoing or planned research projects
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aim to advance monitoring methods for DPR, it is not likely that new monitoring tools or programs will
substantially change the current paradigm of treatment methods, or sizing and management of
environmental and engineered storage buffers. Instead, it will likely be the meaningful use of the extensive
body of data that is already collected through existing monitoring programs that could impact the
implementation of DPR. Analysis of a facility's operating data could, for example, be facilitated through use
of artificial neural networks and other predictive analytics. These kinds of tools have proven useful in
predicting trends in financial and economic market sectors for nearly a decade. With the increasing
availability of computing power, predictive analytics could be applied to DPR to provide integrated process
evaluation, control, and proactive identification of preventive actions to demonstrate that the facility and
processes are meeting the treatment objectives on a continuous basis.
The Water Research Foundation (WRF) report Assessment of Techniques to Evaluate and Demonstrate
the Safety of Water from Direct Potable Reuse Facilities: Literature Review (Rock et al., 2016) characterizes
available monitoring tools and strategies for meeting DPR treatment objectives. The WRF report provides
practical information to utilities and municipalities interested in implementing DPR programs (Rock et al.,
2016).
10.7 Selecting Monitoring Locations
Each treatment process must demonstrate its functioning as expected by careful selection of monitoring
tools and locations. For potable reuse monitoring to be reasonably practical and operable, monitoring must
focus on managing the risks to public health. Section 10.2 describes the application of the HACCP
methodology to water reuse. This methodology requires critical control points (CCPs) for both pathogen
and chemical control.
tC ' 1 Distinguishing Critical Control Poi<«t •>	a\n Critical Operating Points
(COPs)
CCPs are locations where essential unit processes occur, and powerful monitoring techniques can evaluate
process performance to protect public health. Selecting a focused, concise list of CCPs that represent key
risks to health, rather than adding every possible monitoring parameter for every piece of the process,
allows the CCP methodology to succeed. Pathogen and chemical constituents require CCPs. An example
of a CCP might be a reverse osmosis (RO) system, where the RO represents a CCP for both microorganism
and chemical removal. In this case, the CCP can monitor for electrical conductivity: if the conductivity rises
above a critical limit, a Supervisory Control and Data Acquisition (SCADA) system would sound an alarm
and operators could take corrective action.
Additional monitoring requirements, called critical operating points (COPs), may be important to ensure
successful facility operation. For example, antiscalant dosing and pH correction are important parameters
for RO scaling management, but are not directly related to public health protection; therefore, these
parameters serve as COPs rather than CCPs. Failure to manage RO scaling may result in loss of
production, increased operating costs, and increased maintenance.
Operators must manage both CCPs and COPs. Differentiating between the two can clarify reporting,
maintain appropriate regulator focus, and clearly demonstrate that public health is paramount.
For more examples of CCP and COP applications and step-by-step instructions on how to use the CCP
framework for a potable reuse system, refer to the WE&RF (2016b) study Critical Control Point Assessment
to Quantify Robustness and Reliability of Multiple Treatment Barriers of a DPR Scheme.
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10.8	Phases of Monitoring: Validation and Compliance
Assessment of unit processes occurs in two phases: the piloting or commissioning phase (validation
monitoring) and the full-scale operation phase (compliance/operational and verification monitoring).
10.8.1	Validation Monitoring
The objective of validation monitoring during commissioning is to ensure the treatment process is
functioning as expected. Water quality is monitored for each treatment process and the final product water.
Validation monitoring can last from 30 days to up to 6 months. The data collected during this period serves
as a baseline of system performance for future comparison.
10.8.2	Compliance Monitoring
Long-term monitoring demonstrates the continuous production of high-quality water. Periodic grab sampling
complements online continuous monitoring of certain parameters. For parameters that cannot be measured
cheaply or quickly, infrequent periodic samples (such as quarterly or annually) can further verify process
performance and build confidence in the treatment system.
In states that set log removal requirements for microbial or chemical indicators, unit process performance
is monitored during operation to verify achievement of target log removals. In some cases, spiking studies
(such as with viruses) demonstrated higher log removals through a given unit process than online
monitoring demonstrated. For example, some spiking studies have shown 6-log removal of viruses through
RO. However, RO performance is typically verified using online electrical conductivity or online total organic
carbon (TOC) meters, which only can detect 1 to 2-log range. Therefore, the RO system can only receive
1 to 2-log removal credits if ongoing monitoring includes these instruments. Alternatively, surrogates such
as sulfate, phosphate, and proprietary dyes can provide a range of 3 to 5-log. As a result, the selection of
monitoring tools has important design implications and should be a significant design component.
Monitoring tools with greater detection ranges allow for higher credits for the unit processes they monitor.
For a summary of pathogen log reduction credits achieved by full advanced treatment and biofiltration-
based treatment and the performance monitoring methods used to verify those log removal values, refer to
Tables 7.4a and 7.4b in the Framework for Direct Potable Reuse (NWRI, 2015). The credited log removals
for each unit process may change as monitoring tools improve.
10.9	Calibration
All monitoring tools require regular calibration per manufacturer guidance. Also, periodic grab samples
measured with bench-top methods occur regularly (often weekly); bench-top methods verify data generated
by continuous online tools. These calibration procedures are similar or identical to those used in
conventional drinking water plants. But, potable reuse facilities may rely on critical control instruments
generally not considered critical at a conventional plant (such TOC or free ammonia analyzers).
10.10	Reporting
Although local authorities specify reporting requirements, it must involve annual reports at a minimum.
Annual report preparation is an opportunity to critically evaluate facility operations for meeting the stated
water quality objectives. For an example of the components of an annual report from the Orange County
Water District in California, refer to NWRI section 11.6.3 (2015).
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10.11 Indicators and Surrogates
Chapter 4 discussed potential chemical and microbial constituents present in wastewater. Indicator
compounds, surrogate parameters, and/or conservative tracers are commonly used to predict
concentrations or removal of pathogenic microorganisms and hazardous chemical contaminants. Accurate
characterization of water quality involves the meticulous selection of a suite of indicators and surrogate
parameters appropriately aligned with target contaminants. Indicators and surrogates help determine the
efficacy of individual removal mechanisms and treatment barriers where it is impractical to measure actual
target contaminants (Khan, 2013; EPA, 2012a; WHO, 2001). The overall objective of such monitoring is to
inform whether potable reuse water can demonstrate log removal or de minimis risk situations. Monitoring
less costly indicators, rather than pathogens or hazardous chemical contaminants, allows for more testing
and potentially provides for a more reliable assessment of process variability. Ideally, the selected suite of
indicators represents many physiochemical properties and behaviors, and provides information regarding
the removal of other compounds with similar properties. The ultimate goal is to develop a potable reuse
monitoring framework that provides assurance that potentially harmful chemical and microbial constituents
are removed during treatment.
Table 10-1 and Table 10-2 summarize important monitoring terms that can help remove the ambiguity in
using the general terms indicators and surrogates.
Table 10-1. Microbial monitoring terms (adapted from WHO, 2001; WRF, 2008; NRC, 2012a; EPA,
2012a)
Term
Comment
Fecal contamination
indicator
Historically, total coliforms, fecal coliforms, Escherichia coli, fecal streptococci, and
enterococci are used as indicators of possible sewage contamination, because they are
commonly found in human and animal feces. Although they are generally not harmful
themselves, they indicate the possible presence of a fecal contamination event. There is no
direct correlation between any fecal contamination indicator and enteric pathogens - the
indicators only imply that pathogens may be present since fecal matter may be present.
Microbial treatment
process performance
indicator
A valid performance indicator has the same relative rate of removal or destruction as a
specific target pathogen for a specific treatment process. For example, monitoring total
heterotrophic bacteria or total coliforms can give an idea of the effectiveness of chlorine
disinfection for many bacterial pathogens, but does not give meaningful predictions of the
effectiveness against viral or protozoan pathogens. Similarly, coliphage is used to predict
viral degradation in treatment processes.
Microbial treatment
process performance
monitoring tool
Similar to performance indicators, a valid performance surrogate has the same relative rate
of removal or destruction as a specific target pathogen or group of pathogens for a specific
treatment process. For example, measuring electrical conductivity across an RO membrane
demonstrates membrane integrity, and indirectly implies whether pathogens are removed
upstream of the membrane (all pathogens are orders of magnitude larger than the salt ions
detected in conductivity measurements).
Table 10-2. Chemical monitoring terms (adapted from WRF, 2008; NRC, 2012a)
Term
Comment
Chemical treatment
process performance
indicator
Indicators can be selected for specific treatment processes or a complete treatment train.
Examples of chemicals that represent broader classes of compounds based on
physicochemical properties, such as functional groups. These indicators demonstrate the
effectiveness of advanced oxidation performance.
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Term
Comment
Chemical treatment
process performance
surrogate
As for indicators, surrogates can be selected for specific treatment processes or a
complete treatment train. TOC is a surrogate for organic matter and often is monitored for
overall treatment performance as well as the proper functioning of specific treatment steps.
California requires purified water have a TOC less than 0.5 mg/L prior to groundwater
recharge, whereas Florida requires less than 3 mg/L. EPA 2012 Guidelines suggest less
than 2 mg/L.
10.11.1 Microbial Treatment Process Performance Indicators
Monitoring pathogen densities at low enough concentration levels in finished water to indicate log
removal, inactivation, or de minimis risk is not feasible due to cost, time, and enumeration method
constraints. Therefore, the use of indicator organisms or treatment process control parameters are
required to determine microbiological treatment performance of potable treatment trains.
10.11.1.1	Protozoa
The most recognized treatment process performance criteria for protozoan removal/inactivation includes 1)
defined design and operating conditions and turbidity criteria for different filtration processes and 2) the use
of CT (residual concentration x contact time) values for inactivation. These criteria form the basis for
demonstrating protozoan removal/inactivation efficiencies under EPA's treatment technique requirements
(EPA, 1998b). Alternatively, Clostridia, such as Clostridium perfringens and Clostridium sporogenes, can
act as treatment process performance indicators for protozoa such as Giardia lamblia and Cryptosporidium
parvum; but, this approach may not be as easy to monitor (Khan, 2013).
The North Carolina regulations for Type 2 reclaimed water, which is the most restrictive water quality
category regulated for state water reuse, recently added C. perfringens. Type 2 reclaimed water can directly
supplement a drinking water source, provided the blended water is impounded for 5 days and the reclaimed
water does not exceed 20 percent ofthe average flow into the impoundment. The rules forType 2 reclaimed
water specify effluent microbial concentrations and treatment performance requirements for E. coli,
coliphage, and C. perfringens. To date, North Carolina is the only state that uses C. perfringens as an
indicator in its water reuse regulations. Europe has used C. perfringens as a fecal contamination indicator
(not process performance indicator) since the 1960s (NRC, 2004). Some states, such as California, require
monitoring of Giardia and Cryptosporidium spp., which can take up to 24 hours to cultivate and are costlier
than indicator compounds, as mentioned previously (EPA, 2012a).
10.11.1.2	Bacteria
The most commonly tested fecal bacterial indicators are total conforms, fecal conforms, Escherichia coli,
and enterococci.
Total conforms are a group of bacteria that are widespread in nature. All members ofthe total coliform group
can occur in human feces, but some can occur in animal manure, soil, submerged wood, and in other
places outside the human body. In drinking water, total conforms inform the adequacy of water treatment
for bacteria and the integrity ofthe distribution system, because their presence indicates contamination of
a water supply by an outside source (see discussion ofthe Total Coliform Rule in Chapter 3).
Fecal conforms, a subset of total coliform bacteria, are more fecal-specific in origin. E. coli is a species of
fecal coliform bacteria that is specific to fecal material from humans and other warm-blooded animals. The
Revised Total Coliform Rule added E. coli to drinking water regulations (fully implemented April 1, 2016).
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Enterococci are distinguished by their ability to survive in saltwater; this characteristic more closely mimics
many pathogens compared to other bacterial indicators. Enterococci are typically more human-specific than
the larger fecal streptococcus group. EPA does not currently have drinking water recommendations for
enterococci.
Potable reuse schemes use microbial indicators because they are non-seasonal, more abundant, and
therefore more sensitive, affordable, and fasterto enumerate than directly monitoring pathogens of concern
(e.g. noroviruses and rotaviruses) (Khan, 2013). However, they are also relatively limited in their ability to
predict the presence of pathogens (as fecal contamination indicators) or removal of pathogens (as microbial
treatment process performance indicators) (EPA, 2012a; Khan, 2013).
10 11.1,3 Viruses
Enteric viruses may exist in water that is free of bacterial indicators because bacteria are less resistant than
most viruses to environmental factors and water and wastewater treatment processes (EPA, 2015a). This
shortcoming of bacteria as a treatment performance indicator also pertains to protozoa; this is why EPA
prescribes treatment technique requirements for viral and protozoan pathogens rather than relying on
coliform occurrence in distribution systems. The same is true for ambient surface waters. While existing
2012 recreational water quality criteria are based on enterococci and E. coli, published research indicates
that coliphages may be equally good indicators of fecal contamination as E. coli and enterococci, and better
indicators of pathogenic virus removal in treated wastewater than bacteria (EPA, 2015a). As mentioned in
Chapter 3, EPA is currently developing a coliphage-based recreational water quality criterion. EPA
published two standardized enumeration culture-based methods published (Method 1601 and 1602) for
both male-specific and somatic coliphages (EPA 2001 b,c). EPA is also currently evaluating an ultrafiltration
method (dead-end hollow tube fiber) for concentrating viruses in multiple liters of water, with enumeration
by EPA Method 1602.
California recycled water regulations utilize lab strain coliphages (MS2) as treatment performance
indicators, whereas North Carolina reclaimed water regulations utilize indigenous coliphages at the end of
the pipe to verify removal of infectious viruses (regulations can be found in Chapter 3).
Some pathogenic viruses can be detected using cell culture methods. Cell culture methods are not,
however, available for all pathogens, and some cell culture assays require several weeks. Where cell
culture based methods are not available, researchers rely primarily on molecular methods; but, these
methods cannot distinguish between viable and non-viable particles. See Assessment of Techniques to
Evaluate and Demonstrate the Safety of Water from Direct Potable Reuse Facilities (Rock et al., 2016) for
a discussion on cell culture methods.
10,11.2 Microbial Treatment Process Performance Surrogates
There are several examples of microbial treatment process performance surrogates for various membrane-
based treatment systems. For example, measuring electrical conductivity or TDS across an RO membrane
demonstrates membrane integrity. It also indirectly implies whether pathogen removal occurs upstream of
the membrane since all pathogens are orders of magnitude larger than the salt ions detected in conductivity
measurements. Fluorescent dyes and microspheres may detect RO membrane imperfections that would
impact virus removal with up to 4-log sensitivity (Khan, 2013). The presence of dyes or microspheres in the
permeate stream would indicate membrane damage or overall system compromise (such as faulty
interconnectors or o-rings). Similarly, there is a range of treatment process performance surrogates used
for monitoring disinfection processes. In chlorine disinfection systems, monitoring free chlorine residual
determines if CT treatment objectives are met. Alternatively, application of the CT concept also applies to
systems using chloramines, ozone, or chlorine dioxide. For UV disinfection systems, UV dose is measured
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Chapter 10 | Training, Operating, and Monitoring
rather than CT to inform log inactivation for viruses or protozoa. Often, all of these process monitoring
parameters are tied to process control. For example, often when total residual chlorine or UV intensities
are low, the chemical or UV dose can be increased.
10.11.3	Chemical Treatment Process Performance Indicators
Multiple chemical indicators should be selected to represent a wide-range of physiochemical properties,
such as molecular size, pH adjusted octanol-water partition coefficients (Dow), acidity constants, volatility,
dipole moment, etc. Physiochemical properties govern the attenuation of contaminants during treatment,
therefore selecting multiple chemical indicators with a variety of physiochemical properties will inform the
removal performance of unknown or emerging contaminants and target contaminants with similar
properties (Khan, 2013; Bellona et al., 2004). In concept, monitoring indicators that are consistently
measurable in secondary treated wastewater and possess a broad range of physicochemical properties
can provide some level of assurance that chemical constituents, including unknown compounds and
degradation products, are removed (Dickenson et al., 2011). Detection of indicator compounds above some
threshold could indicate performance deficiencies (Kahn, 2013). There is currently no consensus in the
scientific research community regarding what thresholds are appropriate. In potable reuse projects, current
practice is to remove indicator compounds to current detection levels; however, current detection limits may
come into debate as methodological improvements continue to lower detection levels. See 2016 WRF
report Assessment of Techniques to Evaluate and Demonstrate the Safety of Water from Direct Potable
Reuse Facilities for a discussion on indicators applied to potable reuse (Rock et al., 2016).
10.11.4	Chemical Treatment Process Performance Monitoring Surrogates
Since chemical indicator measurements generally involve sophisticated analytical equipment and require
days to weeks for analytical results, monitoring chemical surrogates can provide a way to assure that
treatment barriers are performing as expected with near instantaneous results. There are various chemical
surrogates, such as conductivity, turbidity, biochemical oxygen demand (BOD), UVA, TOC, total nitrogen,
nitrate, and fluorescence excitation/emission matrix spectroscopy; see the 2016 WRF report Assessment
of Techniques to Evaluate and Demonstrate the Safety of Water from Direct Potable Reuse Facilities for a
discussion on these surrogates (Rock et al., 2016).
A WateReuse Foundation (WRF) study, entitled Development of indicators and surrogates for chemical
contaminant removal during wastewater treatment and reclamation (WRF, 2008), investigated surrogate
parameters and indicator compounds for wastewater-derived chemical contaminants in IPR systems. The
project goals were to analyze the performance of analytical methods used to measure indicator
concentrations and to assess the capability of the selected surrogates and indicators to accurately predict
the occurrence of target contaminants. The study included an inter-laboratory comparison that revealed
significant variations in recovery and relative standard deviations of indicator concentrations between
experienced analytical laboratories. This indicated the high degree of uncertainty in concentrations reported
at the low ppt-level. Researchers binned indicator compounds into categories indicating whether they were
well-removed by specific unit processes and suggested monitoring approaches for start-up and full-scale
operation of various types of treatment. The study demonstrated that surrogates do not usually correlate
strongly with the actual removal of trace chemical constituents at the ng/L level. However, changes in
surrogate parameters can demonstrate the beginnings of performance deficiencies and can monitor a
specific unit operation or an entire treatment train's performance. By combining the monitoring of surrogate
measures with targeted indicator chemicals, the surrogates can be calibrated to indicate when treatment
processes are not performing as designed (Snyder, 2014).
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The monitoring requirements outlined in the California Groundwater Replenishment with Recycled Water
regulations serve as an example of surrogate parameters and a suite of chemical indicators used in
conjunction to assess the performance of unit operations. The California Department of Public Health
(CDPH) specifies that one of two approaches involving chemical indicators must be used to ensure the
proper functionality of advanced oxidation processes through pilot testing. The first option requires an
occurrence study involving the identification of nine indicators present in the source water. It also requires
the identification of appropriate dosing conditions to achieve 0.5-log removal of indicators in Groups A-G
and 0.3-log removal of indicators in Groups H-l (Table 10-3). In addition, at least one surrogate parameter
or operating parameter must be used to continuously monitor for the removal of at least five of the nine
chemical indicators (WRRF, 2013a; CDPH, 2014). Pilot testing, including challenge or spiking tests, must
confirm the results. (See Chapter 3 for additional information on California requirements.)
Table 10-3. Potential indicator compounds with differing physiochemical properties to
demonstrate
Group Title
Functional Group
Potential Indicators1
A
Hydroxy Aromatic
Acetaminophen, Benzyl salicylate, Bisphenol A, Estrone, Hexyl
salicylate, Nonylphenol, Triclosan, Clorifibric Acid
B
Amino-Acylamino Aromatic
Sulfamethoxazole, Atorvastatin, Triclocarban
C
Nonaromatics with Carbon
Double Bonds
Acetyl cedrene, Carbamazepine, Codeine, Methyl ionine,
Simvastatin hydroxyl, Terpineol
D
Deprotonated Amine
Atenolol, Caffeine, Diclofenac, Erythromycin-hhO, Fluoxetine,
Metoprolol, Nicotine, Trimethoprim
E
Alkoxy Polyaromatic
Naproxen, Propranolol
F
Alkoxy Aromatic
Gemfibrozil, Hydrocodone
G
Alkyl Aromatic
Benzophenone, Benzyl acetate, Bucinal, DEET, Dilantin, Ibuprofen,
Primidone, Tonalide
H
Saturated Aliphatic
lopromide, Isobornyl Acetate, Meprobamate, Methyl
Dihydrojasmonate
I
Nitro Aromatic
Musk Ketone, Musk Xylene
1 Not intended to be an exhaustive list.
In addition to online or rapid off-line surrogate testing, the use of rapid bioassays can provide information
about water quality that aggregates impacts from all chemicals or nanomaterials present. This includes
degradation products and new chemicals underdevelopment. Recent advances in genomics, proteomics,
metabolomics, and computer modeling have proliferated the ability to examine cellular responses to water
quality using a range of bioassays (Snyder, 2014). These approaches help capture potential effects due to
the presence of chemical mixtures. Whole effluent toxicity testing is an example of a bioassay that is
routinely used to monitor the water quality of treated wastewater prior to discharge into surface waters.
Challenges persist in extrapolating observed cellular responses to adverse human health effects and in
developing high-throughput broad bioassays (Tice et al., 2013; Snyder, 2014). Bioassays can be paired
with mass spectroscopy; a sample that produces bioactivity (observed through inexpensive bioassays) can
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be used to screen samples for targeted analysis using more expensive high-resolution mass spectrometry
ex post facto to identify chemicals.
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Chapter 11 | Cost of Potable Reuse
CHAPTER 11
Cost of Potable Reuse
11.1	Introduction
Much of the discussion on potable reuse implementation deals with public perception issues, regulatory
concerns, and safety considerations, all of which have significant impacts on the cost of implementing
potable reuse. These concerns have driven existing potable reuse projects to utilize advanced treatment
technologies with extensive monitoring approaches and consistent, near complete removal of potentially
harmful contaminants.
The costs of these advanced wastewater treatment facilities (AWTFs), which include microfiltration (MF),
reverse osmosis (RO), and ultraviolet light (UV or UV-advanced oxidation), provide a baseline for
understanding costs for the majority of recent, U.S. potable reuse projects. Less costly alternatives may be
available forfuture projects, particularly for inland locations where total dissolved solid (TDS) concentrations
in treated wastewater effluent do not require salt removal. Understanding how alternative treatment train
options impact costs will provide a basis for evaluating potable reuse against other water supply alternatives
within a community's water supply portfolio.
11.2	Cost Estimates
Cost often drives the selection of treatment alternatives; but, it is important to consider other technical
criteria for a long-term project that includes substantial operating and maintenance costs. Most engineering
feasibility studies include the development of lifecycle costs; this allows for comparison between alternative
systems when evaluating multiple configurations that could meet the same treatment objectives.
In addition, the same treatment system may vary in cost based on project delivery and equipment
procurement methods. Decisions about these methods are multifaceted and are both site- and owner-
specific. Lifecycle costs should include capital equipment costs, construction, replacements part costs
(based on warranty period), chemical and labor costs, power costs, and several other ancillary factors. Final
decision-making about the best treatment system for a specific application may include non-cost factors.
These non-cost factors may include environmental and recreational impacts, avoided costs of water supply,
local economic impacts, and water quality reliability (Tricas and Liner, 2017).
A recent WateReuse Research Foundation (WRRF) study provided an overview of alternative treatment
trains for reuse, the costs, and a triple bottom line (TBL) (financial, environmental, and social elements)
evaluation of the treatment train alternatives. Additionally, WRRF provided a comparison of the costs of
direct potable reuse (DPR) and indirect potable reuse (IPR) to seawater desalination, brackish groundwater
desalination (inland), imported water, non-potable reuse, and water use efficiency, conservation, and
restrictions based on California cost estimates (WRRF, 2014b). Since costs vary significantly with time,
future cost considerations should reflect published cost indices and anticipation of future cost escalation.
11.2.1 Capital Costs
Total capital costs should include any structural, civil, electrical, instrumentation and controls, and other
support systems necessary for project implementation. The cost of treatment equipment for any potable
reuse project is often only a fraction of the total construction cost, but required to make accurate estimates
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of both construction and lifecycle costs; additionally, treatment equipment costs contain an understanding
of the equipment suppliers' scope of supply.
While the database of operational DPR facilities is limited (AWWA, 2016), there are a large number of
operational indirect potable reuse (IPR) projects using similar or identical treatment processes (Chalmers
et al., 2010). The construction costs for reuse facilities varied, depending on the location, capacity, and
ancillary facilities included; the facilities averaged approximately $6.75/1,000-gal capacity (February 2015
dollars), with a limited economy of scale between projects ranging in size from 1.8 million gallons per day
(MGD) (Big Spring, Texas: $7.0/1,000 gal) to 70 MGD (Orange County, California: $6.5/1,000 gal)
(Chalmers et al., 2010; Bailey, 2013; Sloan, 2013; Chalmers et al., 2013; WRRF, 2014c)
The costs above do not include engineering, permitting, or other project development costs, which can be
approximately 25 percent of the total project costs. Further, these costs do not include off-site costs for
transmission of product water or supply of feed water; these costs will vary depending on the project. The
largest components of capital costs are the microfiltration and RO equipment, which each account for
approximately 25 percent of the overall construction costs once installed. Low costs are the result of the
unique locations of existing facilities, either near the ocean or near an inland location where brine disposal
will not have a significant environmental impact.
11.2.2 Operations and Maintenance Costs (O&M Costs)
Operations and maintenance costs (O&M costs) for membrane based potable reuse facilities generally
range from $1.8 to $2.0 per thousand gallons or $0.48 to $0.53 dollars per cubic meter (Bailey, 2013;
Patel, 2010; Won et al., 2010; Chalmers et al., 2013). Some O&M costs will vary depending on the actual
production of the plant, while other O&M costs will be fixed. Variable O&M costs include costs for chemicals,
power, UV lamp replacement, cartridge filter replacement, concentrate disposal, and other miscellaneous
costs. Fixed O&M costs include labor, membrane replacement, and equipment repair and replacement,
which are generally independent of the variations in daily production. Most operational U.S. IPR facilities
currently operate at or near their rated capacities, limiting the variation in O&M costs (Won et al., 2010;
Chalmers et al., 2013).
Figure 11-1 includes a breakdown of typical O&M costs of a potable reuse facility using a membrane-based
treatment train. These costs are based on a hypothetical 10 MGD facility but derive from actual operating
costs of existing, online facilities. The actual breakdown of various O&M costs will vary from plant-to-plant
and treatment train, but the largest cost components will generally be power and labor.
For potable reuse facilities, the RO feed pumps typically account for roughly half of the overall power use,
with membrane filter pumps and UV systems each accounting for 5 to 10 percent of the total power. Higher
salinity water will require more power to treat with RO, while water with high fouling potential (such as a
non-nitrified source water) will result in higher power costs for all of the membrane processes.
Finished water pumping may be a substantial cost, but it depends on the pumping distance and elevation
that the water must be pumped to; the costs presented in Figure 11-1 do not include finished water
pumping. Similarly, brine disposal costs can be a substantial component of the operating costs for many
inland facilities. However, disposal costs are typically only minor O&M cost components for IPR. Treatment
requirements post-AWTF may impact the overall cost of producing final product water. For example, AWTF
water requires subsequent treatment to satisfy the surface water treatment rules (SWTRs) if it discharges
into a surface water body or engineered storage buffer or goes directly to the water treatment plant (WTP).
AWTF water may only require chlorination if it is for aquifer recharge and the withdrawn water is considered
groundwater.
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Chapter 11 | Cost of Potable Reuse
Cher
ll
Replacement
Parts/Materials
10%
Membranes
9%
Power
41%
Labor
22%
Figure 11-1. Typical O&M cost breakdown of a potable reuse facility using a membrane-based
treatment train
11.2.3	Cost of Alternative Treatment Trains
There are methods for assessing alternative treatment processes that would support the implementation of
more cost-effective treatment trains, particularly where TDS removal does not require RO. Ozone-
biologically active filtration (ozone-BAF) is garnering interest as one of the alternative treatment trains for
DPR applications, as described in Chapter 7. From an O&M cost perspective, the O&M costs for an ozone-
BAF system include labor, power, chemicals (including liquid oxygen), laboratory and monitoring costs,
equipment maintenance and repair, residuals management, and other minor costs. RO-based plants have
significantly higher O&M costs, primarily due to significantly higher power requirements than the ozone-
BAF treatment train. RO-based treatment trains employ mechanically intensive processes, which result in
2.5 times as much electricity as the ozone-BAF plants (average of 3867 kWh/MG [1.0 kWh/m3] for RO-
based treatment compared to approximately 1400 kWh/MG [0.37 kWh/m3] for ozone-BAF treatment)
(WRRF, 2014d). In contrast, the San Diego Pure Water Facility treatment train used ozone-BAF as
pretreatment and full advanced treatment, resulting in a projected power usage of more than 11,000
kWh/MG (3.0 kWh/m3) (MWH et al., 2016). These higher costs are partially due to conservative
assumptions used in facility planning, but also demonstrate the potential for increased facility costs when
adding additional treatment steps beyond full advanced treatment.
11.2.4	Cost of Water
The nominal cost of water is calculated by dividing the sum of the annualized capital cost and annual O&M
costs by the volume of water produced during the year; the result is usually expressed as dollars per unit
volume, for example, in dollars per thousand gallons ($/kgal), dollars per cubic meter ($/m3), or dollars per
acre-foot ($/AF). The calculations included herein assume a 5 percent interest rate with capital costs
annualized over 20 years. Typical treated water costs for a 10 MGD indirect potable reuse facility would
range from $2.8 to $4.1 per thousand gallons. A white paper from the WateReuse Research Foundation
(WRRF, 2014b) lists a larger range of $2.5 to $6.1 per thousand gallons ($820 to $2,000 per acre-foot or
$0.7 to $1.6 per m3) that includes estimates of significant brine disposal costs and conveyance costs for
pipeline construction in the high-end estimates.
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The level of treatment provided in potable water reuse projects may vary throughout the country, depending
on the source water quality, the level of treatment required, and the type of potable reuse practiced Thus,
selecting the appropriate treatment technology for potable reuse (including both IPR and DPR) can be a
complex decision. Governmental organizations, non-governmental organizations, and advocacy groups
can influence the selection of more expensive treatment. This is partially because the full financial,
environmental, and social elements of the TBL may not be considered (WRRF, 2014d). WRRF funded a
study to develop and apply a TBL framework to guide the water reuse selection process to provide
information to utilities about the real cost of treatment. Fit for Purpose Water: The Cost of Overtreating
Reclaimed Water evaluated and documented two IPR via surface water augmentation reuse scenarios.
The treatment trains considered for planned IPR were the full advanced treatment train and an ozone-BAF
process, as shown in Figure 11-2 and Figure 11-3; these scenarios were evaluated for flows of 5, 20, and
70 MGD.
MISSflElLIEAIlflU
WCNOCHLORAUWE
REVERSE
OSMOSIS
I'V'AQP
RAW '.VOTER
RESERVOIR FDR
DRNKIN3WTF
VVWTP
Secsnoary
=ffuen:





J
1


>	ij
ANTlSCALisT
CChC
H2C2
BW Waste to
WWTP Influenf
Discharge
LIME AND
CC2
SALT D-3POSAL TO
LAND =ILL
OR
EVAPORATION PONDS
OCEAN¦
SE'h'ER
disposal
OR MECHANICAL EVAPORATION
'BRINE OONOENTEATOR +
BR NE crystallizer:
Figure 11-2, Full advanced treatment train
© Copyright 2014 WateReuse Research Foundation (project 10-01), used with permission
UV	RAW WATFK
GAP !"DSINFECTION RESERVOIR FOR
ONLYi CRNKNGWTP
OpTIGiSAL
FLOCKED
OZONE
WWTP
qC'AGULANT
Discharge
To gravity
thickening and
centrifuge
Figure 11-3. Ozone-BAF treatment train
© Copyright 2014 WateReuse Research Foundation (project 10-01), used with permission
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Chapter 11 | Cost of Potable Reuse
The study demonstrated several important points (WRRF, 2014d):
•	Non-membrane based treatment trains have the lowest TBL costs for all flows analyzed; capital,
O&M, and total TBL costs were lowest for the ozone-BAF alternative.
•	There is an economy of scale for non-membrane based treatment at higher flows (> 20 MGD); for
example, at 20 MGD, the full advanced treatment alternative was 32% more than the ozone-BAF
train and at 70 MGD, full advanced treatment was 54% higher than ozone-BAF.
•	Management of RO concentrate is a limiting factor for locations where sewer or ocean outfall
options for brine disposal were not possible; concentrate handling and disposal significantly
impacted the cost of the full advanced treatment alternative and approximately doubles the cost
of providing treated water.
Table 11-1 provides a summary of the costs developed in this report for a 20 MGD scenario.
Table 11-1. Cost of alternative treatment trains for a 20 MGD facility (adapted from WRRF, 2014d)
Process

Full advanced treatment with RO
Ozone-
Concentrate Disposal
Cost/Impact
BAF
Ocean
Outfall
Mechanical
Evaporation
Evaporation
Ponds
Capital Cost (millions)
$91
$120
$172
$303
Annual O&M Cost (millions)
$4.2
$5.9
$10.9
$6.3
Annual Environmental Costs (millions)
$0.4
$1.6
$6.3
$2.2
Total TBL NPV (millions)
$173
$267
$533
$512
Cost of Water (including
environmental costs)
$/AF
$386
$596
$1,190
$1,143
$/1000 gal
$1.18
$1.83
$3.65
$3.51
$/m3
$0.31
$0.48
$0.96
$0.93
Power Consumption (MWh/year)
4,400
16,000
65,400
22,000
Chemical Consumption (dry tons/year)
1,770
1,860
3,020
1,860
Air Emissions (tons/year)
C02
2,900
13,400
44,200
17,200
Other
11
30
150
49
While others have presented similar cost data ranges (NWRI, 2015), extrapolating the cost data presented
here to a specific current or future project requires caution, because these costs derive from a limited
number of operational facilities. Furthermore, these costs are presented to give the reader an approximate
idea of costs for two generic treatment options. Detailed estimates of costs for any potable reuse facility
should be part of a potential feasibility analysis. However, it is quite clear from the cost information
presented here that a non-membrane based treatment process is the most cost-effective solution for
providing AWT water. Typically, IPR does not use salt removal processes, but certain conditions require its
use; these conditions include coastal and desert areas where water supplies are already high in TDS. In
these cases, RO treatment may be necessary for reducing TDS; but, utilities should consider this process
carefully before implementation because of the high costs. Alternatives should be considered, such as
partial RO treatment and blending with other lower TDS sources (WRRF, 2014d).
RO brine management costs may limit the cost effectiveness of DPR employing RO as compared to other
options for providing potable reuse source water. As previously discussed, costs associated with RO
11-5

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2017 Potable Reuse Compendium
Chapter 11 | Cost of Potable Reuse
concentrate management are site-specific and vary depending on the characteristics and volume of the
concentrate.
Table 11-2. Costs of RO concentrate management options for potable reuse treatment (from Table
10.3 in NWRI, 2015)1
Disposal option
Cost Range2
Typical Cost2
$/AF
$/103 gal
$/AF
$/103 gal
Deep well injection
50-80
0.15-0.25
70
0.21
Evaporation ponds
140-175
0.43-0.54
155
0.48
Land application, spray
135-160
0.41-0.49
115
0.35
Brine line to ocean
110-150
0.35-0.38
115
0.35
Zero liquid discharge
700-850
2.15-2.61
775
2.38
Notes: Adapted in part from WRRF, 2014b.
1The reported costs are based on an Engineering News Record Construction Cost Index of 9900. Value of index in
1913=100.
2Based on a concentrate flow of 2 Mgal/d. S/103 gai*325.892=$/A.
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2017 Potable Reuse Compendium
Chapter 12 | Epidemiological and Related Studies
CHAPTER 12
Epidemiological and Related Studies
Epidemiological studies can be used to study the occurrence and etiology of adverse health outcomes
including potential adverse health impacts originating from reclaimed water. Currently few epidemiological
studies evaluate the possibility of adverse health impacts from drinking reclaimed water, and these studies
are limited and represent an area where additional data is needed.
For water reuse, identifying the cause of public health issues that coincide with conditions at a treatment
plant or in finished water could assist in determining the source of potential infections. For example, if a
certain strain of adenovirus is the cause of a gastroenteritis outbreak and the same strain is also detected
in treated water, the case for cause and effect is stronger. If no such relationship is observed, then the
source of infection is potentially a causative agent other than virus strain detected in the potable water.
12.1 Epidemiology of Water Reuse
A discussion of epidemiological studies on reclaimed water can be found in Appendix A of Water Research
Foundation's Assessment of Techniques to Evaluate and Demonstrate the Safety of Water from Direct
Potable Reuse Treatment Facilities (Rock et al., 2016) shown below in Table 12-1.
Table 12-1. Epidemiological and related studies on health effects pertaining to reclaimed water
consumption (Rock et al., 2016. Reproduced with permission. ©Water Research Foundation)
Study
Brief Project
Epidemiological
Reporting
Primary
Reference

Description
Study Description
Period
Conclusion

IPR Montebello
Recycled water, in
Evaluated mortality,
1962-1980
Study results did
Frerichs 1983
Forebay Project -
addition to
morbidity, cancer

not support the

LA County, CA,
imported river
incidence, and birth

hypothesis of a

Study No.1 (The
water and
outcomes using

causal relationship

Health Effects
stormwater, has
census tracts for two

between potable

Study)
been used for
recycled water areas

reuse and cancer,


recharge of the
(high and low

diseases, or


groundwater since
concentration) and

mortality. No dose-


1962. From 1962
two control areas. A

response


to 1977, recycled
telephone interview

relationship


water used for
study was conducted

between reclaimed


recharge was
interviewing adult

water and disease


treated to
females living in areas

could be deduced


secondary effluent
where recycled water




disinfection
was consumed, as




standards.
well as interviews of





adult females who





were part of a control





group. Interviews





included questions on





abortions, adverse





reproductive





outcomes, and





general well-being.



12-1

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Chapter 12 | Epidemiological and Related Studies
Study
Brief Project
Description
Epidemiological
Study Description
Reporting
Period
Primary
Conclusion
Reference
IPR Montebello
Forebay Project -
LA County, CA,
Study No.2 (The
Rand Study)

Examined mortality,
morbidity, infectious
diseases such as
Giardia, Hepatitis A,
Salmonella, and
Shigella, and cancer
incidence using
census tracts for two
recycled water areas
(high and low
concentration) and
two control areas.
1987-1991
Study results did
not determine a
causal relationship
between potable
reuse and cancer,
diseases, or
mortality.
Sloss et al.
1996
IPR Montebello
Forebay Project -
LA County, CA,
Study No.3 (The
Second Rand
Study)

Examined adverse
birth outcomes such
as prenatal
development and
infant mortality (low
birth weight, birth
defects, nervous
system defects, etc.)
1982-1993
Study found that
rates of adverse
births were
equivalent between
the reclaimed water
users and a control
group.
Sloss et al.
1999
Health status of
residents of an
urban dual
reticulation
system - Sydney,
Australia
Households in dual
reticulation
developments
receive water from
the Rouse Hill
Recycled Water
Scheme in
Sydney, Australia
for non-potable
purposes, such as
filling swimming
pools. Residents in
neighboring
suburbs receive
conventionally
treated potable
water.
Primary-care
consultation rates
were examined for
both communities.
Five conditions were
tested including:
Gastroenteritis,
respiratory complaints,
dermal complaints,
urinary tract infections
and musculoskeletal
complaints.
2005-2006
No increased rates
of health issues as
a result of
reclaimed water
exposure. There
was little variation
in consultation
rates was noted
between residents
of using reclaimed
and conventional
water supply
alternatives.
Sinclar et al.
2010
DPR Goreangab
Plant-Windhoek,
Namibia
First direct potable
reuse project in the
world. Treatment
at the time of the
study included
sand filtration and
granular activated
carbon. Water was
then distributed in
the drinking water
pipeline network.
Analyzed > 15,000
cases of diarrheal
disease in surrounding
area. Residents
receiving conventional
water were compared
to those receiving
recycled water.
1976-1983
Found that
diarrheal disease in
Caucasians
drinking reclaimed
water was
marginally lower
than Caucasians
drinking
conventional water
supply. Incidence
rates greatly
Isaacson and
Sayed, 1988;
Odendaal,
1991
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2017 Potable Reuse Compendium
Chapter 12 | Epidemiological and Related Studies
Study
Brief Project
Epidemiological
Reporting
Primary
Reference

Description
Study Description
Period
Conclusion





increased in blacks





and colors, all of





whom received the





conventional water





supply.

Total Resource
San Diego
Telephone interviews
1988-1990
Study concluded,
Cooper et al.
Recovery Project,
investigated a
were conducted on

based on short-
1992 and
City of San Diego
proposed surface
1,100 women

term bioassay
1997; NRC

water
regarding adverse

results, that
1998

augmentation
birth outcomes,

reclaimed water did


scheme utilizing
infectious diseases,

not display more


advanced
and mortality.

genotoxic or


treatment and
Additionally, four

mutagenic


discharge into the
bioassays were used

tendencies than the


Miramar Reservoir
to evaluate genetic

raw water supply.


(source of drinking
toxicity and




water supply at the
carcinogenic effects




time).
between the Miramar





Reservoir (reclaimed





water) and the city's





raw water supply.



The Chanute
Chanute, Kansas
An epidemiology study
150 days
The study
Metzler et al.
Kansas
experienced a
was completed
during 1956-
concluded that
1958
Emergency Direct
drought between
investigating the
1957
fewer instances of

Potable Reuse
1956 and 1957
instances of stomach

stomach and

Project
requiring the
and intestinal illness

intestinal illness


implementation of
during the period in

were reported


an indirect reuse
which the Neosho

when recycled


scheme involving a
River was dammed.

water was being


dam on the


consumed vs.


Neosho River


instances reported


below the WWTP.


during the following


The dam was


winter when the


subsequently


conventional water


washed out when


supply was being


the area


utilized.


experienced heavy





precipitation.





Before the dam





was implemented,





a portion of intake





to the drinking





water plant was





municipal





wastewater.




Denver Potable
Denver
A bio-analytical
1990-1994
No treatment
Lauer et al.
Water Reuse
implemented a
epidemiological study

related effects were
1994 and

demonstration
was completed



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2017 Potable Reuse Compendium
Chapter 12 | Epidemiological and Related Studies
Study
Brief Project
Description
Epidemiological
Study Description
Reporting
Period
Primary
Conclusion
Reference
Demonstration
Project
potable reuse
project in order to
evaluate the
viability of potable
reuse.
investigating the
relative health impacts
of highly treated
reclaimed water
derived from
secondary wastewater
compared to Denver's
drinking water supply.
Chronic toxicity and
oncogenicity in rats
and mice was
measured using in
vivo methods for 150
to 500 organic residue
concentrates.

observed during
this study
1996; NRC
1998
Tampa Water
Resource
Recovery Project
This planned but
not implemented
potable reuse
project involved
augmentation of
the Hillsborough
River raw water
supply using
advanced treated
effluent from a
granular activated
carbon and ozone
disinfection
treatment train.
The epidemiology
study evaluated
approximately 1,000 x
organic concentrates
used in Ames
Salmonella,
micronucleus, and
sister chromatid
exchange experiments
in three dose levels. In
vivo testing comprised
mouse skin initiation,
strain A mouse lung
adenoma, 90-day
subchronic assay on
mice and rats. A
reproductive study on
mice was also
completed.
1987-1992
There was no
mutagenic activity
detected in any of
the samples. All
tests completed
showed negative
results, excluding
some fetal toxicity
exhibited in rats,
but not mice, for
the AWT sample.
CH2M Hill
1993, Pereira
et al. No Date;
NRC 1998
Toxicological
Relevance of
EDCs and
Pharmaceuticals
in Drinking Water
- Water Research
Foundation
Project 3085
Water samples
were studied from
20 drinking water
facilities, four
wastewater plants
(raw and reuse
water), and food
products. 62 target
compounds (EDCs
and
pharmaceuticals)
were investigated.
In vitro cellular
bioassay (E-screen)
was used with a
method reporting limit
of 0.16 nanograms per
liter (ng/L), expressed
as estradiol
equivalents (EEq).
2007
Of 62 compounds
studied, only three
were consistently
detected in drinking
waters of the US
(Atrazine,
meprobamate,
phenytoin). Only 11
compounds were
found in greater
than 20% of
drinking waters.
Out of food
products, raw
wastewater,
Snyder et al.
2008
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Chapter 12 | Epidemiological and Related Studies
Study
Brief Project
Description
Epidemiological
Study Description
Reporting
Period
Primary
Conclusion
Reference




recycled water, and
finished drinking
water, finished
drinking water had
the lowest levels of
estrogenicity.

Potomac Estuary
Experimental
Wastewater
Treatment Plant
Potomac Estuary
Experimental
Water Treatment
Plant (EEWTP)
receives a 50-50
blended mix of
estuary water and
nitrified secondary
effluent from the
Blue Plains
Wastewater
Treatment Plant
which treats
wastewater from
Washington D.C.
EEWTP provides
treatment in the
form of aeration,
coagulation,
flocculation,
sedimentation,
predisinfection,
filtration, carbon
adsorption, and
postdisinfection.
This bioanalytical
study included short-
term in vitro tests on
both EEWTPs influent
and effluent, as well
as effluent from three
drinking water
treatment plants in the
vicinity. Tests
completed included
the Ames Salmonella/
microsome test and a
mammalian cell
transformation test.
1980-1982
Toxicological
parameters
investigated
showed that
EEWTP effluent
was comparable to
product water from
the local drinking
water treatment
plants.
Montgomery,
1983; NRC
1998
Singapore
NEWater Potable
Reuse
The majority of
Singapore's
NEWater is
currently used for
industrial and
commercial use,
however some is
blended with raw
water in reservoirs,
which is then
treated using
MF/RO/UV and
distributed as
drinking water.
Study included a 12-
month period of
testing on Japanese
Medaka fish (Oryzias
latipes) comparing
advanced treated
effluent (NEWater)
and untreated
2001-2003
This study was
completed twice
due to poor
experimental
design; however,
both rounds found
no indication of
estrogenic or
carcinogenic
effects in advanced
treated effluent.
Khan and
Roser, 2007
Santa Ana River
Water Quality
Monitoring Study
This study
included a de facto
indirect potable
This bioanalytical
study included three
rounds of testing on
2004-2005
The three rounds of
testing did not yield
statistically
Woodside,
2004
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Chapter 12 | Epidemiological and Related Studies
Study
Brief Project
Epidemiological
Reporting
Primary
Reference

Description
Study Description
Period
Conclusion


reuse scheme
Japanese Medaka fish

significant


originating from an
comparing shallow

differences


Orange County
groundwater adjacent

between fish & the


Water District
to the Santa Ana River

shallow


(OCWD) diversion
and control water. The

groundwater


directing Santa
study analyzed fish for

adjacent to the


Ana River water to
tissue pathology,

river and fish & the


the Orange County
vitellogenin induction,

control water.


groundwater basin
reproduction, limited




for recharge. The
tissue pathology, and




majority of flow for
gross morphology.




recharge is





tertiary-treated





product water.




Soil Aquifer
Water from
In vitro methods used

WWTPs with the
Fox, Houston
Treatment (SAT)
multiple
included:

longest retention
et al. 2006
Investigation
wastewater
treatment plants,
product water from
soil-aquifer
treatment, and
stormwater were
assessed to
evaluate
estrogenic activity
using in vitro
bioassay methods.
-	Estrogen binding
assay
-	Glucocorticoid
receptor competitive
binding assay
-Yeast-based reporter
gene assay
-	MCF-7 cell
proliferation assay
-	in vivo fish
vitellogenin synthesis
assay
-	Enzyme-linked
immunosorbent
assays (ELISAs)
-	GC/MS

times generally had
the lowest detected
levels of
estrogenicity.
Estrogenicity was
effectively removed
during SAT.

12.2 Future Research
Epidemiological information can inform health risks potentially associated with potable reuse. The existing
epidemiological literature on potable water reuse is one potential source of information to support the
assessment of health risks. Additional information and data from risk assessments (see Chapter 5) and
monitoring are needed to characterize possible adverse health outcomes.
While there are numerous limitations to conducting and interpreting available epidemiological data, several
approaches could make better use of future epidemiological opportunities:
•	Selecting large test and control populations.
•	Identifying, where possible, target endpoints that have low incidence and/or variability in control
populations.
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2017 Potable Reuse Compendium
Chapter 12 | Epidemiological and Related Studies
•	Using control and test populations that are as similar as possible controlling for confounders as
appropriate.
•	Incorporating measures of exposure as part of study designs.
As drought conditions persist in certain U.S. regions, there is a growing interest in potable reuse, along with
a need for more information about the potential impact of the practices. Waterborne disease outbreaks
occasionally occur in conventional water supplies; but, this reporting relies on passive surveillance (e.g.,
self-reporting by states to the Centers for Disease Control), which is relatively insensitive and often
inadequate for detecting less than population-level effects. Subtle and background effects, as well as
chronic or sub-chronic effects (e.g., reproduction and developmental effects), are more difficult to attribute
to a water supply. This is an important area for additional research in the United States going forward.
Water Environment and Reuse Foundation released a white paper titled Feasibility of Establishing a
Framework for Public Health Monitoring, which was last updated in 2017. The white paper discusses a
potential framework approach to evaluate DPR using public health surveillance (WE&RF, 2017a).
Additionally, in lieu of epidemiology studies, many scientists are using microbial risk assessment
approaches to understand health risks associated with a given potable reuse treatment scheme (Amoueyan
et al. 2017; Chaundry et al., 2017; Lim et al., 2017; Pecson et al., 2017; Soller et al., 2017; Soller et al.,
2018). Quantitative microbial risk assessment (QMRA) approaches, specifically those using probabilistic
models and inputs, can provide more nuanced information about how consistently public health
benchmarks are achieved, as compared to the traditional log credit allocations and epidemiology studies.
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2017 Potable Reuse Compendium
Chapter 13 | Public Acceptance
CHAPTER 13
Public Acceptance
The topic of direct potable water reuse can be viewed as a controversial, yet beneficial, strategy for reducing
demand on stressed freshwater supplies. Americans tend to be less aware of where their water comes from
than citizens in some countries. In 2012, GE Power and Water conducted an online survey with 1,000
respondents each from the United States, China, and Singapore; 31 percent of Americans did not know
where their water came from, compared to 10 percent in China and Singapore (GE, 2012).
Public outreach can allow the public to access accurate and sufficient information for effective participation
in managing human health and environmental risks. As in all water supply projects, public acceptance is a
crucial step in the planning of potable reuse schemes. An uninformed public may become a major obstacle
to direct potable reuse (DPR), regardless of its technical feasibility or safety.
There are many ways to enhance public involvement. One way to begin is with the identification of key
stakeholders that the project will impact; a two-way communication effort between stakeholders and project
leaders should occur early in the planning process to facilitate education, input, and trust between entities.
Water management issues often require public involvement because water management decision-making
directly impacts the community (EPA, 2012a) as they are usually the prime consumers. Provided below is
a discussion of public acceptance regarding water reuse in the United States, as well as an evaluation of
public relations principals and behaviors that have historically lent themselves to beneficial public
acceptance results.
13.1 Current State of Public Acceptance
13.1.1	Public Awareness and Opinion
The previously mentioned GE survey showed a high level of support among Americans for water reuse and
a willingness to pay a bit more to ensure future clean water. The study found that the vast majority of
American respondents (80 percent) strongly support non-potable reuse, and just over half (51 percent)
agree that recycled water is drinkable; but, only 30 percent of those surveyed favor drinking it (GE, 2012).
In Australia, when asked why DPR might be less attractive or more difficult to implement than indirect
potable reuse (IPR), respondents indicated that public acceptance was a main obstacle and mentioned
specific barriers (Khan, 2013):
•	DPR lacks "community acceptance and/or wider public acceptance."
•	The "yuck factor."
•	Lack of "public confidence in the safety of advanced treatment technologies" and the abilities of
the operators.
•	"Non-equal distribution of recycled water."
13.1.2	Shifting Opinions with Public Outreach and Changing Conditions
Water scarcity is one issue that is forcing parts of the United States to visit, or revisit, water reuse from both
a technological and public opinion standpoint, potentially including the use of advanced treated recycled
water to augment drinking water supplies.
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2017 Potable Reuse Compendium
Chapter 13 | Public Acceptance
The types of steps and tools effective at building trust and ultimately shifting public opinion are briefly listed
in Section 13.2 and summarized in the Framework for Direct Potable Reuse Chapter 12 (NWRI, 2015).
Multiple communities invested in these types of tools:
•	Santa Clara Valley Water District (California) holds public tours of the Silicon Valley Advanced
Water Purification Center and has other forms of outreach, including a website.
•	Pure Water San Diego (California) ran a demonstration project with public tours and hosts a
website.
•	Orange County Groundwater Replenishment System (California) offers public tours and a
website.
•	Los Angeles Groundwater Replenishment Project (California).
•	Wichita Falls DPR Project (Texas) - see Appendix A.
13.2 Important Factors in Stakeholder Engagement for Potable Reuse
Research shows that it is important to start outreach efforts early, set goals, engage the media, use
consistent terminology, avoid the use of jargon, and confront misinformation as soon as it is encountered
(WRRF, 2015b; AWWA/WEF, 2008).
Involving stakeholders from the beginning can be critical for effective policy decisions. There are trust-
building strategies for water utilities tackling potable reuse public engagement processes (AWWA/WEF,
2008):
•	Gaining the support of stakeholders in the project, including customers, the public overall, and
policy makers, through persistent communication.
•	Highlighting the overall water supply concerns and emphasizing the importance of water
reliability.
•	Creating confidence in the quality of the reclaimed water.
•	Confronting conflict head-on.
There are a series of core steps and behaviors that, when used together, have proven to be successful in
engaging the public on water reuse and potable reuse projects:
•	Situational Analysis: Assess the community (i.e. identify the "public") and the utility itself.
Define the problem the community needs to solve.
The "general public" is hard to define, as people belong to many geographic, socio-economic,
gender, age groups, political affiliations, social orientations, and recreation interests. When
identifying the "public," it is important to be overarching and diverse, including representatives
from different ethnic, demographic, geographic, cultural, professional, and political backgrounds.
Outreach to organized groups is just as essential as outreach to individuals. Outreach must
clearly articulate the problem that the community faces (or, phrased in a positive spin, the
opportunity for community improvement) to foster understanding and support.
•	Determine the desired/required level of public involvement and identify potential
stakeholders.
There needs to be a complete list of stakeholders before a project plan is in place to establish
early adopters that other stakeholders can turn to for questions or concerns.
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2017 Potable Reuse Compendium
Chapter 13 | Public Acceptance
•	Develop and follow a broad and tactical communication plan (EPA, 2012a).
There is no "one-size-fits-all" model for public involvement plans because the most effective
approach will be the result of specific context and project analysis. Consider consistent and clear
messaging, avoid technical jargon, take note that vocabulary words and structure count, and
emphasize "purity" of reuse water. In public acceptance endeavors, it is important to ensure that
the water industry itself is communicating consistent, effective, and well-received vocabulary
words and water reuse messages to the general public.
•	Gauge the community and utility perspectives; evaluate trusted information sources and
potential participation pathways.
Trusted information sources vary significantly amongst communities and states. It is a good idea
to perform a public opinion survey in each community considering a water reuse project.
•	Meet and discuss with community officials and leaders early in the planning process, and
regularly throughout the project lifetime.
Addressing community viewpoints and concerns can increase support for a given project, both
from an opinion and monetary aspect. Policy makers can correctly answer stakeholder's
questions if they are well-informed about the project.
•	Request the participation of outside experts as spokespeople or evaluators, but voice that
the utility should be the primary source of credible information.
An advisory group with representatives from multiple community perspectives can be helpful, and
the group should be aware of their expected contribution and role within the project's decision-
making process.
•	Explore the media, social media, and informational channels.
The power of the media in today's society can both help and hinder the implementation of potable
reuse projects. Therefore, project leaders trying to promote acceptance should engage with the
media to facilitate accurate and science-based DPR fact reporting. Strong opponents of DPR, as
well as the media, tend to use attention-gaining phrases that magnify public fear, such as "toilet-
to-tap," perpetuating the idea that consumers are drinking wastewater rather than treated
reclaimed water. However, the media can widely and effectively distribute fact-based information
once they receive the correct information. For example, in 2011, USA Today ran a story regarding
the DPR operation in Big Spring, Texas, and in 2012, the New York Times featured a front-page
story titled "As 'Yuck Factor' Subsides, Treated Wastewater Flows from Taps."
Social media enables a direct form of contact with stakeholder groups that can be very effective
and beneficial. However, committing to the use of social media through the project lifetime
requires dedication, time, and resources. Failing to maintain a social media presence could be
detrimental to the project.
•	Involve employees and ensure they are knowledgeable on the most up-to-date
information.
Employees working for the utility or organization leading the project effort often receive questions
or concerns relating to project material or ideas. If employees are well-versed on the subject
matter, they will be able to convey a flow of factual information to the public.
•	Create a dialogue with the wider community of stakeholders, listen to opposition, and be
timely with responses.
DPR projects typically have opposition due to fears of public health impacts, especially on
children. Involving opponents of the project in initial public involvement groups can ease concerns
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Chapter 13 | Public Acceptance
from the rest of the opposing public and can bring up issues early in the process that may be
overlooked otherwise (EPA, 2012a).
The WateReuse Research Foundation (WRRF) (now the Water Environment and Reuse Foundation
(WE&RF)) has published communication frameworks that may facilitate state and local outreach. For further
information about one possible communication framework, please see Model Public Communication Plans
for Increasing Awareness and Fostering Acceptance of Direct Potable Reuse. This document includes
examples for suggestions of how to phrase messages to induce a positive connotation with potable reuse
water, among other things (WRRF, 2015b).
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Chapter 14 | Research
CHAPTER 14
Research
14.1 Current Highlighted Research
The field of potable reuse has advanced significantly over the past several years, with several foundations,
researchers, and utilities contributing to groundbreaking research. In 2011, Direct Potable Reuse: A Path
Forward laid out numerous relevant research needs and existing knowledge gaps (WRRF, 2011a). The
following year, Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of
Municipal Wastewater identified direct potable reuse (DPR) research topics (NRC, 2012a). Several entities
have committed to and launched significant research programs dedicated to potable reuse since 2012, as
described below.
14.1.1	EPA
EPA has several ongoing projects related to potable reuse. First, EPA is researching municipal wastewater
treatment plant (WWTP) performance in removing pathogens, microbial indicators, and trace chemical
constituents. This research aims to characterize the removal of these constituents upstream of an advanced
wastewater treatment facility (AWTF) for potable reuse.
Secondly, EPA is evaluating recreational water quality criteria (RWQC) for coliphage - a viral indicator. As
part of this effort EPA has published a literature review (EPA, 2015a); held the 2016 Coliphage Experts
Workshop; and published a peer-reviewed Proceedings of the Coliphage Expert Workshop (EPA, 2017v).
EPA is currently working on the derivation of the coliphage-based RWQC, which involves a risk assessment
approach. Coliphage-based RWQC can help improve ambient source water quality for drinking waters.
Additionally, coliphage monitoring may also be used for characterizing source water for AWTFs for potable
reuse. For example, North Carolina reuse legislation has proposed coliphage be assessed in reclaimed
waters (see Chapter 3 for relevant North Carolina law).
Additionally, EPA researchers and partners systematically collected and published data on viruses in raw
wastewater and conducted quantitative microbial risk assessment (QMRA) using distributions of viruses
and other reference pathogens found in raw wastewater to assess risk differences associated with various
DPR treatment trains (Eftim et al., 2017; Soller et al., 2017; Soller et al., 2018). QMRA methodology is
adaptable to other DPR treatment trains and can incorporate additional data as it becomes available. Soller
et al. (2018) included a sensitivity analysis of the aforementioned QMRA work using updated dose-
response models (Messner et al., 2014; Messner and Berger, 2016; Teunis et al., 2008; Soller et al., 2017)
and evaluated the QMRA methodology against the log-credit approach currently applied in several states.
Collectively, this work will be useful to multiple groups: federal and state regulators considering DPR for
drinking water, state and local decision-makers considering whether to permit a particular DPR project, and
design engineers considering which unit treatment processes to employ for particular projects.
14.1.2	Water Environm* rt K use Foundation (WE&RF)
In 2016, the Water Environment Research Foundation (WERF) merged with the WateReuse Foundation
(WRRF) and became the WE&RF.
The California DPR Initiative began in June 2012 through WE&RF (then WRRF) and WateReuse California
to address the feasibility of developing criteria for DPR (per CA Senate Bill 918). The December 2012 DPR
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2017 Potable Reuse Compendium
Chapter 14 | Research
Research Needs meeting forged the framework of WRRF's DPR research agenda. From 2012-2016,
WRRF allocated $6 million to fund over 30 DPR research projects. When combined with funding from
partners, this DPR research portfolio addressing DPR's regulatory, utility, and community barriers is $24
million.
In total, there are 34 WE&RF supported DPR projects completed or underway (Table 14-1). The research
listed in Table 14-1 aims to facilitate the implementation of DPR in a safe, economical, and socially
acceptable manner (Figure 14-1). The research under this initiative is summarized in a single document
Potable Reuse Research Compilation: Synthesis of Findings (WE&RF, 2016b). Dozens of technical expert
authors synthesized the 34 DPR projects into 9 chapters by topic: Source Control, Evaluation of Potential
Direct Potable Reuse Treatment Trains, Pathogens (Surrogates and Credits), Pathogens (Rapid
Continuous Monitoring), Risks and Removal of Constituents of Emerging Concern, Critical Control Points,
Operation and Maintenance and Operator Training and Certification, Failure and Resiliency, and
Demonstration of Reliable, Redundant Treatment Performance.
WE&RF is continuing research to advance potable reuse. They are leveraging a $4.5M grant from the state
of California to address research needs and gaps across the country (WE&RF, 2017b).
14.1.3 Water Research Foundation (WRF)
In addition to WE&RF research, Table 14-1 also summarizes the WRF's published and ongoing potable
reuse research projects. Notably, along with other partners including the National Research Council (NRC),
WRF supported two seminal studies - the Augmenting Potable Water Supplies with Reclaimed Water
project which resulted in Issues in Potable Reuse: The Viability of Augmenting Drinking Water Supplies
With Reclaimed Water (NRC, 1998), and the Assessment of Water Reuse as an Approach for Meeting
Future Water Supply Needs project that resulted in Water Reuse: Potential for Expanding the Nation's
Water Supply Through Reuse of Municipal Wastewater (NRC, 2012a). Currently, WRF research includes
DPR as part of a comprehensive (One Water) approach to water supply planning. In 2014, WRF launched
a research program titled "Integrated Water Management: Planning for Future Water Supplies" with the aim
of developing data, tools, and knowledge to support integrated, resilient, and reliable water supply
diversification by 2019. In addition, WRF supported a significant research portfolio specifically dedicated to
biofiltration, a technology showing promise for DPR applications (Table 14-2).
DPR Initiative Research
Figure 14-1. Barriers to potable reuse research (WRRF figure used with permission)
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2017 Potable Reuse Compendium
Chapter 14 | Research
Together, these research efforts hold promise for continuing to advance the use of DPR and indirect potable
reuse (IPR) projects for providing a safe and reliable source of drinking water for communities across the
United States.
Table 14-1. DPR and related research projects




Research Focus
Project Title
Project
Number(s)
Organi-
zations)
Publication
Date
Regulatory
Concerns
Utility
Concerns
Commu-
nity
Concerns
Augmenting Potable
Water Supplies with
Reclaimed Water
WRF 371
WRF, NRC
1998
X
X

Issues with Potable
Reuse: The Viability of
Augmenting Drinking
Water Supplies with
Reclaimed Water
-
AWWA
1998
X
X

Soil Treatability Pilot
Studies to Design and
Model Soil Aquifer
T reatment Systems
WRF 901
WRF
1998

X

Protocol for Designing
and Conducting UV
Disinfection Studies
WRF 2674
WRF, NWRI
2001
X
X

Water Reuse:
Understanding Public
Perception and
Participation
00-PUM-1
WERF
2003


X
Water Quality
Requirements for
Reclaimed Water
WRF 2697
WRF,
AECOM
2004
X
X
X
Framework for
Developing Water
Reuse Criteria with
Reference to Drinking
Water Supplies
WRF 2968
WRF, WRRF,
UKWIR
2005
X


Organic Nitrogen in
Drinking Water and
Reclaimed
Wastewater
WRF 2900
WRF
2006

X

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Chapter 14 | Research




Research Focus
Project Title
Project
Number(s)
Organi-
zations)
Publication
Date
Regulatory
Concerns
Utility
Concerns
Commu-
nity
Concerns
Understanding Public
Concerns and
Developing Tools to
Assist Local Officials
in Planning
Successful Potable
Reuse Projects
WRF2919
WRF, WRRF
2006


X
Removal of EDCs and
Pharmaceuticals in
Drinking and Reuse
Treatment Processes
WRF 2758
WRF
2007

X

Comparing
Nanofiltration and
Reverse Osmosis for
Treating Recycled
Water
WRF 3012
WRF
2008

X

Fate of
Pharmaceuticals and
Personal Care
Products through
Wastewater T reatment
Processes
03-CTS-22-
UR
WERF
2008

X

Microbial Risk
Assessment Interface
Tool and User
Documentation Guide
04-HHE-3
WERF
2008
X
X

Using Reclaimed
Water to Augment
Potable Water
Resources
-
WERF
2008
X


Contributions of
Household Chemicals
to Sewage and their
Relevance to
Municipal Wastewater
Systems and the
Environment
03-CTS-21-
UR
WERF
2009

X

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Chapter 14 | Research




Research Focus
Project Title
Project
Number(s)
Organi-
zations)
Publication
Date
Regulatory
Concerns
Utility
Concerns
Commu-
nity
Concerns
Development of
Indicators and
Surrogates for
Chemical
Contaminant Removal
during Wastewater
Treatment and
Reclamation
04-HHE-
1CO
WERF
2009
X
X

Minimizing Water
Treatment Residual
Discharges to Surface
Water
WRF 4086
WRF
2010

X

Optimizing Filtration
and Disinfection
Systems with a Risk-
Based Approach
04-HHE-5
WERF
2010

X

Regulatory Aspects of
Direct Potable Reuse
in California
-
NWRI
2010
X


Direct Potable Reuse:
A Path Forward
-
WRRF
2011
X
X

Enhanced Reverse
Osmosis Systems:
Immediate Treatment
to Improve Recovery
WRF 4061
WRF
2011

X

Assessment of Water
Reuse as an Approach
for Meeting Future
Water Supply Needs
WRF 4276
WRF, NRC,
and other
organizations
2012
X
X

Challenge Projects on
Low Energy Treatment
Schemes for Water
Reuse: Phase 1
WERF5T10a
WERF
2012

X

Demonstrating
Advanced Oxidation
with Biodegradation
for Removal of
Carbamazepine
INFR3SG09
WERF
2012

X

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Chapter 14 | Research




Research Focus
Project Title
Project
Number(s)
Organi-
zations)
Publication
Date
Regulatory
Concerns
Utility
Concerns
Commu-
nity
Concerns
Demonstration of
Membrane Zero Liquid
Discharge for Drinking
Water System:
Literature Review
06-CTS-1CO
WERF
2012

X

Direct Potable Reuse:
Benefits for Public
Water Supplies,
Agriculture, the
Environment, and
Energy Conservation
-
NWRI
2012
X
X

The Effect of Prior
Knowledge of
'Unplanned' Potable
Reuse on Acceptance
of 'Planned' Potable
Reuse
WRRF-09-
01
WRRF
2012


X
Research Strategy for
Water Reuse
Workshop
WRF 3145
WRF
2012

X

Treatment Processes
for Removal of
Emerging
Contaminants
INFR6SG09
WERF
2012

X

Challenge Projects on
Low Energy Treatment
Schemes for Water
Reuse: Phase 1
ENER2C12b
WERF
2013

X

Challenge Projects on
Low Energy Treatment
Schemes for Water
Reuse: Phase 1
ENER2C12c
WERF
2013

X

Challenge Projects on
Low Energy Treatment
Schemes for Water
Reuse: Phase 1
ENER2C12d
WERF
2013

X

Evaluation of Risk
Reduction Principles
for Direct Potable
Reuse
WRRF-11-
10
WRRF
2013
X
X

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Research Focus
Project Title
Project
Number(s)
Organi-
zations)
Publication
Date
Regulatory
Concerns
Utility
Concerns
Commu-
nity
Concerns
Pilot Testing of
Membrane Zero Liquid
Discharge for Drinking
Water Systems
ENER2C12a
WERF
2013

X

Demonstrating the
Benefits of
Engineered Direct
versus Unintended
Indirect Potable Reuse
Systems
WRRF-11-
05
WRRF
2014
X
X

Desalination
Concentrate
Management Policy
Analysis for the Arid
West
WERF5T10
WERF
2014
X
X

Economics of DPR
WRRF-14-
08
WRRF
2014
X
X

Protocol for
Evaluating Chemical
Pretreatment for High
Pressure Membranes
WRF 4249
WRF
2014

X

Colorado Direct
Potable Reuse White
Paper - An Overview
WERF5C11
WERF
2015
X
X

Considering the
Implementation of
Direct Potable Reuse
in Colorado
WERF5T10b
WERF
2015
X
X

Developing Direct
Potable Reuse
Guidelines
WRA-14-01
WRA
2015
X
X

Institutional Issues for
One Water
Management
WRF 4487
WRF
2015
X
X

Integrated Water
Management:
Planning for Future
Water Supplies
WRF 4550
WRF
2015

X

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Research Focus
Project Title
Project
Number(s)
Organi-
zations)
Publication
Date
Regulatory
Concerns
Utility
Concerns
Commu-
nity
Concerns
Model Public
Communication Plans
for Increasing
Awareness and
Fostering Acceptance
of Direct Potable
Reuse
WRRF-13-
02, WRF
4540
WRRF, WRF
2015


X
Advanced Oxidation
of Pharmaceuticals
and Personal Care
Products: Preparing
for Indirect and Direct
Water Reuse
WRF 4213
WRF
2016

X

Colorado Direct
Potable Reuse Study
-
WateReuse
Colorado,
Colorado
Water
Conservation
Board
(CWCB)
Water Supply
Reserve
Account
Grant
Program
2016
X
X

Creating a Roadmap
for Bioassay
Implementation in
Reuse Waters: A
cross disciplinary
workshop
WE&RF-15-
02
WE&RF
2016
X
X

Critical Control Point
Assessment to
Quantify Robustness
and Reliability of
Multiple Treatment
Barriers of DPR
Scheme
WE&RF-13-
03, WRF
4541
WE&RF,
WRF
2016
X
X

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Research Focus
Project Title
Project
Number(s)
Organi-
zations)
Publication
Date
Regulatory
Concerns
Utility
Concerns
Commu-
nity
Concerns
Development of
Operation and
Maintenance Plan and
Training and
Certification
Framework for Direct
Potable Reuse (DPR)
Systems
WE&RF-13-
13
WE&RF
2016
X
X

Direct Potable Reuse
(DPR): Comparing
relative human health
risk of indirect potable
reuse (IPR) and DPR
-
WEF,
WE&RF, and
CDM Smith
2016
X
X
X
DPR Research
Compilation:
Synthesis of Findings
from DPR Initiative
Projects
WE&RF-15-
01
WE&RF
2016
X
X
X
Enhanced Pathogen
and Pollutant
Monitoring of the
Colorado River
Municipal Water
District Raw Water
Production Facility at
Big Spring Texas
WE&RF-14-
10
WE&RF
2016

X

Ensuring stable
microbial water
quality in Direct
Potable Reuse
distribution systems
(workshop)
WE&RF-14-
18
WE&RF
2016
X
X

Equivalency of
Advanced Treatment
Trains for Potable
Reuse (3 publications)
WRRF-11-
02
WRRF
2016
X
X

Evaluation of Source
Water Control Options
and the Impact of
Selected Strategies on
DPR
WE&RF-13-
12
WE&RF
2016
X
X

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Research Focus
Project Title
Project
Number(s)
Organi-
zations)
Publication
Date
Regulatory
Concerns
Utility
Concerns
Commu-
nity
Concerns
Guidelines for
Engineered Storage
for Direct Potable
Reuse
WE&RF-12-
06
WE&RF
2016
X
X

Monitoring for
Reliability and
Process Control of
Potable Reuse
Applications
WE&RF-11-
01
WE&RF
2016
X
X

Methods for Integrity
Testing of NF and RO
Membranes
WE&RF-12-
07
WE&RF
2016
X
X

Using Greywater and
Stormwater to
Enhance Local Water
Supplies: An
Assessment of Risks,
Costs, and Benefits
WRF 4521
WRF
2016
X
X

Soil Aquifer Treatment
Characterization with
Soil Columns for
Groundwater
Recharge in the San
Fernando Valley
WRF 4600
WRF
2017
X
X

Blending
Requirements for
Water from Direct
Potable Reuse
Treatment Facilities
WE&RF-13-
15, WRF
4536
WRF,
WE&RF
2017
(anticipated)
X
X

Demonstrating
Redundancy and
Monitoring to Achieve
Reliable Potable
Reuse
WE&RF-14-
12
WE&RF
2017
(anticipated)
X
X
X
Develop Methodology
of Comprehensive
(fiscal/triple bottom
line) Analysis of
Alternative Water
Supply Projects
Compared to DPR
WE&RF-14-
03
WE&RF
2017
(anticipated)

X

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Research Focus
Project Title
Project
Number(s)
Organi-
zations)
Publication
Date
Regulatory
Concerns
Utility
Concerns
Commu-
nity
Concerns
Enhanced Removal of
Nutrients from Urban
Runoff with Novel
Unit-Process Capture,
Treatment, and
Recharge Systems
WRF 4567
WRF
2017
(anticipated)

X

Establishing
Additional Log
Reduction Credits for
WWTPs
WE&RF-14-
02
WE&RF
2017
(anticipated)
X
X

Anticipating Trade-
offs of Using
Alternative Water
Supplies
WRF 4715
WRF
2018
(anticipated)

X
X
Assessment of
Techniques to
Evaluate and
Demonstrate the
Safety of Water from
DPR Treatment
Facilities
WE&RF-13-
14, WRF
4508
WRF,
WE&RF
2018
(anticipated)
X
X

Blending
Requirements for
Water from DPR
Treatment Facilities
WRF 4536
WRF
2018
(anticipated)

X

Conventional Drinking
Water T reatment of
Alternative Water
Sources: Source
Water Requirements
WRF 4665
WRF
2018
(anticipated)

X

Framework for
Evaluating Alternative
Water Supplies
WRF 4615
WRF
2018
(anticipated)

X

Integrating Land Use
and Water Resources:
Planning to Support
Water Supply
Diversification
WRF 4263
WRF
2018
(anticipated)

X

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Research Focus
Project Title
Project
Number(s)
Organi-
zations)
Publication
Date
Regulatory
Concerns
Utility
Concerns
Commu-
nity
Concerns
Building-Scale
Treatment for Direct
Potable Water Reuse
& Intelligent Control
for Real Time
Performance
Monitoring
WRF 4691
WRF
2019
(anticipated)

X

Challenges and
Practical Approaches
to Water Reuse
Pricing
WRF 4662
WRF
2019
(anticipated)

X

Kinetics Modeling and
Experimental
Investigation of
Chloramine
Photolysis in
Ultraviolet-driven
Advanced Water
T reatment
WRF 4699
WRF
2019
(anticipated)

X

Application of
bioanalytical tools to
assess biological
responses associated
with water at DPR
facilities
WE&RF-14-
15
WE&RF
TBD
X
X

Building-Scale
Treatment for Direct
Potable Water Reuse
& Intelligent Control
for Real Time
Performance
Monitoring
WRRF-16-
02
WE&RF,
WRF
TBD
X
X

Characterization and
Treatability of TOC
from DPR Processes
Compared to Surface
Water Supplies
WE&RF-15-
04
WE&RF
TBD
X
X

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Research Focus
Project Title
Project
Number(s)
Organi-
zations)
Publication
Date
Regulatory
Concerns
Utility
Concerns
Commu-
nity
Concerns
Demonstration of High
Quality Drinking Water
Production Using
Multi-Stage Ozone-
Biological Filtration
(BAF): A Comparison
of DPR with Existing
IPR Practice
WE&RF-15-
11
WE&RF,
Gwinnett
County
TBD
X
X

Developing
Curriculum and
Content for DPR
Operator Training
WE&RF-15-
05
WE&RF
TBD
X
X

Evaluating Post
Treatment Challenges
for Potable Reuse
Applications
WRRF-16-
01
WE&RF
TBD

X

Fate of sulfonamide
antibiotics through
biological treatment in
WRRFs designed to
maximize reuse
applications
WRRF-16-
04
WE&RF
TBD

X

Framework for Public
Health Monitoring:
White paper
WE&RF-14-
14
WE&RF
TBD
X
X

From Sewershed to
Tap: Resiliency of
Treatment Processes
for DPR
WE&RF-14-
13
WE&RF
TBD
X
X

Molecular Methods for
Measuring Pathogen
Viability/lnfectivity
WE&RF-15-
07
WE&RF
TBD
X
X

NDMA Precursor
Control Strategies for
DPR
WE&RF-15-
13
WE&RF, Los
Angeles
Sanitation
TBD

X

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Research Focus
Project Title
Project
Number(s)
Organi-
zations)
Publication
Date
Regulatory
Concerns
Utility
Concerns
Commu-
nity
Concerns
Operational,
Monitoring, and
Response Data from
Unit Processes in Full-
Scale Water
Treatment, IPR, and
DPR
WE&RF-14-
16
WE&RF
TBD
X
X

Optimization of ozone-
BAC treatment
processes for potable
reuse applications
WE&RF-15-
10
WE&RF,
American
Water
TBD
X
X

Predicting RO removal
of toxicologically
relevant unique
organics
WE&RF-14-
19
WE&RF
TBD
X
X

White Paper on the
Application of
Molecular Methods for
Pathogens for Potable
Reuse
WE&RF-14-
17
WE&RF
TBD
X
X

Advanced Oxidation
of Pharmaceuticals
and Personal Care
Products: Preparing
for Indirect and Direct
Water Reuse
-
AWWA
-
X
X

Table 14-2. WRF biofiltration related research projects (WRF, 2017)
Project Title
Project Number
Publication Date
Microbial Activity on Filter-Adsorbers
WRF 408
1992
Biologically Enhanced Slow Sand Filtration for Removal of
Natural Organic Matter
WRF 409
1993
Ozone and Biological Treatment for DBP Control and Biological
Stability
WRF 504
1994
Drinking Water Denitrification with Entrapped Microbial
Technology
WRF 513
1994
Advances in Taste and Odor Treatment and Control
WRF 629
1995
Removal of Natural Organic Matter in Biofilters
WRF 631
1995
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Chapter 14 | Research
Project Title
Project Number
Publication Date
Design of Biological Processes for Organics Control
WRF 712
1998
Microbial Impact of Biological Filtration
WRF 917
1998
Advanced Oxidation and Biodegradation Processes for the
Destruction of TOC and DBP Precursors
WRF 289
1999
Colonization of Biologically Active Filter Media with Pathogens
WRF 263
2000
Optimizing Filtration in Biological Filters
WRF 252
2001
Removal of Bromate and Perchlorate in Conventional
Ozone/GAC Systems
WRF 2535
2001
Evaluation of Riverbank Filtration as a Drinking Water
Treatment Process
WRF 2622
2001
Innovative Biological Pretreatments for Membrane Filtration
WRF 2570
2003
Application of Bioreactor Systems to Low-Concentration
Perchlorate- Contaminated Water
WRF 2577
2004
Cometabolism of Trihalomethanes in Nitrifying Biofilters
WRF 2824
2005
Ozone-Enhanced Biofiltration for Geosmin and MIB Removal
WRF 2775
2005
Subsurface Treatment for Arsenic Removal—Phase I
WRF 3082
2006/2009
Hexavalent Chromium Removal Using Anion Exchange and
Reduction with Coagulation and Filtration
WRF 3167
2007
State of Knowledge of Endocrine Disruptors and
Pharmaceuticals in Drinking Water
WRF 3033
2008
Biological and Ion Exchange Nitrate Removal Evaluation
WRF 4131
2010
Biological Drinking Water Treatment Perceptions and Actual
Experiences in North America
WRF 4129
2010
Biological Nitrate Removal Pretreatment for a Drinking Water
Application
WRF 4202
2010
Cost-Effective Regulatory Compliance with GAC Biofilters
WRF 4155
2010
Removal and Fate of EDCs and PPCPs in Bank Filtration
Systems
WRF 3136
2010
Treating Algal Toxins Using Oxidation, Adsorption, and
Membrane Technologies
WRF 2839
2010
Engineered Biofiltration for Enhanced Hydraulic and Water
Treatment Performance
WRF 4215
2011
Fate and Impact of Antibiotics in Slow- Rate Biofiltration
Processes
WRF 4135
2012
Occurrence, Impacts, and Removal of Manganese in
Biofiltration Processes
WRF 4021
2012
14-15

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2017 Potable Reuse Compendium
Chapter 14 | Research
Project Title
Project Number
Publication Date
A Monitoring and Control Toolbox for Biological Filtration
WRF 4231
2013
Minimizing Waste Backwash Water from a Biological
Denitrification Treatment System
WRF 4470
2014
Nitrate and Arsenic Removal from Drinking Water with a Fixed-
Bed Bioreactor
WRF 4293
2014
Optimizing Engineered Biofiltration
WRF 4346
2014
An Operational Definition of Biostability for Drinking Water
WRF 4312
2015
Control of Pharmaceuticals, Endocrine Disruptors, and Related
Compounds in Water
WRF 4162
2015
Development of a Biofiltration Knowledge Base
WRF 4459
2015
Pretreatment of Low Alkalinity Organic- Laden Surface Water
Prior to a Coagulation-Ultrafiltration Membrane Process
WRF 4477
2015
Biological Oxidation Filtration for the Removal of Ammonia
from Groundwater
WRF 4574
2016
Chemically Enhanced Biological Filtration to Enhance Water
Quality and Minimize Costs
WRF 4429
2016
Full-Scale Demonstration of Engineered Biofiltration and
Development of a Biofiltration Performance-Tracking Tool
WRF 4525
2016
Optimizing Filter Conditions for Improved Manganese Control
During Conversion to Biofiltration
WRF 4448
2016
Pilot Testing Nitrate Treatment Processes with Minimal Brine
Waste
WRF 4578
2016
Converting Conventional Filters to Biofilters
WRF 4496
2017 (anticipated)
Impact of Filtration Media Type/Age on Nitrosamines
Precursors
WRF 4532
2017 (anticipated)
Impact of Wildfires on Source Water Quality and Implications
for Water Treatment and Finished Water Quality
WRF 4525
2017 (anticipated)
Major Sources of Nitrosamine Precursors in Raw Waters
WRF 4591
2017 (anticipated)
Optimizing Biofiltration for Various Source Water Quality
WRF 4555
2017 (anticipated)
Simultaneous Removal of Multiple Chemical Contaminants
Using Biofiltration
WRF 4559
2017 (anticipated)
Unintended Consequences of Implementing Nitrosamine
Control Strategies
WRF 4491
2017 (anticipated)
Practical Monitoring Tools for the Biological Processes in
Biofiltration
WRF 4620
2018 (anticipated)
14-16

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2017 Potable Reuse Compendium
Chapter 15 | References
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Wells, M. J. M., M.-L. Pellegrin, A. Morse, K.Y. Bell, L.J. Fono. 2008. "Emerging Pollutants." Water Environment
Research, 80 (10): 2026-2057
Wells, M. J. M., A. Morse, K.Y. Bell, M.-L. Pellegrin, L.J. Fono. 2009. "Emerging Pollutants." Water Environment
Research, 81(10): 2211-2254.
Wells, M. J. M., K.Y. Bell, K.A. Traexler, M.L. Pellegrin, A. Morse. 2010. "Emerging Pollutants." Water Environment
Research, 82(10): 2095-2170.
Wetterau, G., P. Liu, B. Chalmers, T. Richardson, H.B. VanMeter, H. B. 2011. "Optimizing RO design criteria for
indirect potable reuse." IDA Journal of Desalination and Water Reuse, 3(4): 40-45.
Wetterau, G., R. Chalmers, P. Liu, W. Pearce. 2013. "Advancing indirect potable reuse in California." Water Practice
& Technology, 8(2): 275-285.
Wetterau, G., P. Fu., C. Chang., B. Chalmers. 2015a. Full-Scale Testing of Alternative UV Advanced Oxidation
Processes for the Vander Lans Water Treatment Facility. WateReuse California Annual Conference.
Wetterau, G., B. Chalmers, K. Bell. 2015b. Comparing Recycled Water and Potable Water Treatment Requirements
in California. Presentation at International Desalination Association World Congress on Desalination and Water
Reuse. REF: IDAWC15-Wetterau.
White, G. C. 1986. Handbook of chlorination. Van Nostrand Reinhold Company.
Won, W., T. Walker, M. Patel, E. Owens. 2010. "Comparing Membrane Operations at Three of the World's Largest
Advanced Water Treatment Plants." IDA Journal of Desalination and Water Reuse, 2(3): 10.
Woodside, G., K. O'Connor-Patel. 2004. Final Report Santa Ana River Water Quality and Health Study. Orange
County Water District.
World Health Organization (WHO). 2001. Water Quality: Guidelines, Standards, and Health. Edited by Lorna Fewtrell
and Jamie Bartram. IWA Publishing. London, UK.
World Health Organization (WHO). 2009. Water Safety Plan Manual: Step-by-step risk management for drinking-
water suppliers. World Health Organization. Geneva.
World Health Organization (WHO). 2012. Pharmaceuticals in Drinking-Water. World Health Organization. Geneva.
World Health Organization (WHO). 2017. Potable Reuse: Guidance for Producing Safe Drinking-Water. World Health
Organization. Geneva.
15-12

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2017 Potable Reuse Compendium
Chapter 15 | References
Wunder, D. B., V. A. Horstman, R. M. Hozalski. 2008. Antibiotics in Slow-Rate Biofiitration Processes: Biosorption
Kinetics and Equilibrium. In Proc. of the Thirty-Sixth Annual; AWWA Water Quality Technology Conference. Denver,
CO.sses. Water Research Foundation, Denver, CO.
Wunder, D.B., R.M. Hozalski. 2012. Fate and Impact of Antibiotics in Slow-rate Biofiitration Processes. Water
Research Foundation, Denver.
Yoo, R.S., D. Brown, R.J. Paradini, G.D. Bentson. 1995. "Microfiltration: A Case Study." Journal of the American
Waterworks Association, 87(3):38-49.
Zeng, Q., Y. Li, S. Yang. 2013. "Sludge Retention Time as a Suitable Operational Parameter to Remove Both
Estrogen and Nutrients in an Anaerobic-Anoxic-Aerobic Activated Sludge System." Environmental Engineering
Science, 30(4): 161-169.
15-13

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Appendix A: Case Study Examples of IPR
and DPR in the United States
Appendix A-1
Appendix A-2
Appendix A-3
Appendix A-4
Appendix A-5
Appendix A-6
Appendix A-7
Los Alamitos Barrier Water Replenishment District of So. CA/Leo J. Vander Lans
Advanced Water Treatment Facility - Indirect Potable Reuse
Orange County Groundwater Replenishment System Advanced Water Treatment
Facility
Gwinnett F. Wayne Hill Water Resources Center, Chattahoochee River and Lake
Lanier Discharge - Indirect Potable Reuse
Village of Cloudcroft PURe Water Project - Direct Potable Reuse
Colorado River Municipal Water District Raw Water Production Facility Big
Spring Plant - Direct Potable Reuse
Wichita Falls River Road WWTP and Cypress WTP Permanent IPR and
Emergency DPR Project
Potable Water Reuse in the Occoquan Watershed

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2017 Potable Reuse Compendium
Appendix A.1 | Vander Lans AWTF
A.1 Los Alamitos Barrier Water
Replenishment District of So. CA/Leo J.
Vander Lans Advanced Water Treatment
Facility (LVLAWTF) - Indirect Potable Reuse
Paul Fu, Water Replenishment District of Southern California
Greg Wetterau, CDM Smith
Project Facts
Location
Size
Year of Installation
Status
Cost
Background
California along the Los Angeles County and Orange County border
3 million gallons per day (MGD) initial, expanded to 8 MGD
2005 initial, expansion completed in 2014
Operational
$14 million initial, $32 million expansion
The Water Replenishment District of Southern California (WRD) is responsible for managing the Central
and West Coast Groundwater Basins, which provide groundwater to 4 million residents in WRD's service
area. Prior to WRD's formation in 1959, over-pumping resulted in water wells becoming dry and seawater
intrusion contaminating coastal groundwater (WRD, 2013). One of WRD's main objectives is to ensure
water delivery to seawater intrusion barrier projects, such as the Alamitos Gap Barrier (AGB), to protect
local aquifers from water quality degradation that would render the resource unusable for beneficial use
(Figure A.1-1).
WRD
Boundary
Los Angel*
Central
Santa Fe
Springs
„ *\Coasf
Coast	
V Barrier
Beach . IW*
Basin
Dominguez
Barrier
Alamitos Gap
Barrier Project
Figure A.1-1. Seawater barrier projects in California (Chang, 2013)
A schematic illustrating the use of well injection to prevent seawater intrusion can be seen in Figure A.1-
2.
A.1-1

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2017 Potable Reuse Compendium
Appendix A.1 | Vander Lans AWTF
Seawater Barrier
Injection Well
U t

—

—










Blocked Seawater
Intrusion

¦
I Hydraulic
Vi=[\ pressure created


Figure A.1-2. Schematic of well injection to prevent seawater intrusion (adapted from Chang, 2013)
WRD has relied on imported water to replenish its groundwater sources. However, in 2005 WRD began
sending recycled water from the Leo J. Vander Lans Advanced Water Treatment Facility (LVLAWTF) to the
AGB for injection (Figure A.1-3). WRD's Water Independence Now program seeks to entirely eliminate
WRD's dependence on imported water as a groundwater replenishment source and instead utilize
alternative supplies such as stormwater and recycled water.
Figure A.1-3. Leo J. Vander Lans Advanced Water Treatment Facility (WRD, 2015)
The AGB currently has 43 injection wells stretching 2.2 miles and 220 associated observation wells. From
1966 through 2005, only municipal potable water was used for injection. The LVLAWTF was constructed
in 2005 with a capacity of 3 MGD (EPA, 2012); the plant expansion completed in December 2014 increased
capacity to 8 MGD (WRD, 2014). Tertiary treated recycled water from the Long Beach Water Reclamation
Plant (LBWRP) serves as the influent water to LVLAWTF where microfiltration, reverse osmosis (RO) and
ultraviolet disinfection with advanced oxidation process (MF/RO/UV-AOP) ensue before being sent, to the
AGB for injection (Chalmers, 2013) .
With the expansion, LVLAWTF is capable of delivering 100 percent advanced treated recycled water to the
AGB instead of blended municipally treated water and recycled water. The expansion will ultimately include
influent water from the 37 MGD Los Coyotes Water Reclamation Plant, located 6 miles north of LVLAWTF.
Treatment Type and Process Flow Block Diagram
The plant expansion increases the overall plant recovery rate from 77 percent to 92 percent (WRD, 2014)
- the highest recovery rate of any equivalent MF/RO/UV-AOP treatment train in the United States. This is a
dramatic increase compared to typical recovery rates of approximately 80 percent (Chalmers, 2013). The
A. 1-2

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2017 Potable Reuse Compendium
Appendix A.1 | Vander Lans AWTF
plant employs a treatment combination of MF, RO, and UV-AOP utilizing hydrogen peroxide (Figure A.1-
4).
Chlorine
i
Tertiary ,	k.
(Title 22)
Effluent
Microfiltration
Dissolved Ai
Flotation
Hydrogen Peroxide
Reverse
Osmosis
I
A
uv
I

3rd
pj

Stage

RO
Wastewater
Treatment
To
Blending
and
Alamitos
Barrier
Injection
Figure A.1-4. LVLAWTF expansion treatment process (adapted from WRD, 2013)
Before the expansion, the reclaimed water was blended with 50 percent municipal water before being
distributed to the AGB. The expansion includes an MF backwash treatment system which recovers 99
percent of the MF influent utilizing dissolved-air flotation (DAF) clarification technology (Figure A.1-5).
DAf EQUAL
TANK
MF Backwash Recovery System
~>K0WRV v
T0R0
DAf
FEEDPUMP
DAT RECOVERY RECOVERY Mr
MF FEEDPUMP
FEEDTANK
TO
WASTE
EQUAL
Figure A.1-5. MF and backwash recovery system at LVLAWTF (Chalmers, 2013)
DAF clarifiers achieve better than 2 nephelometric turbidity units (NTU) turbidity when operated with alum
or ferric chloride as the coagulants. Due to stringent downstream requirements, a major design constraint
of the plant expansion included limiting the amount of waste (i.e. RO brine) generated from treatment
processes to 760,000 GPD, which is sent to a wastewater treatment plant downstream (Chalmers, 2013).
By installing the MF backwash treatment system and an RO-recovery system, which increased RO recovery
A. 1-3

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2017 Potable Reuse Compendium
Appendix A.1 | Vander Lans AWTF
to greater than 92 percent, the plant is able to successfully deliver discharges to the wastewater treatment
plant under 760,000 GPD (Table A.1-1).
Table A.1-1. LVLAWTF plant processes (Chalmers, 2013)
Process
Recovery Rate
Microfiltration
98%
Reverse Osmosis
>92%
Overall Plant Recovery
92%
A third-stage RO system was added as part of the expansion for the purpose of treating RO concentrate
from both two-stage upstream RO systems (Chalmers, 2013). The final steps include UV-AOP and
stabilization of the product water with sodium hydroxide and calcium chloride to control the pH and re-
mineralize the water before it is injected into the AGB. The total chlorine residual leaving the plant is
approximately 3-4 mg/L (WRD, 2012).
Permitting and Monitoring
The LVLAWTF original permit has been revised under the Regional Water Quality Control Board, making
LVLAWTF the first facility to receive approval under the finalized 2014 Groundwater Replenishment Reuse
Regulations (Table 3-2 in Chapter 3). On May 7, 2014, the County Sanitation Districts of Los Angeles
County applied for a wastewater change petition in orderto discharge an additional 5 MGD from the LBWRP
to WRD. The recycled water is continually monitored and available for public view on a web database
known as Geotracker, and also through an interactive well search website owned by WRD.
Influent N-nitrosodimethylamine (NDMA) concentrations to LVLAWTF average 420 parts per trillion (ppt).
NDMA in water can originate from many potential sources including chlorine disinfection processes, ion
exchange resins, water treatment polymers, circuit board manufacturing, leather tanning, pesticide
manufacturing, cosmetic manufacturing, and rocket fuel (Trojan Technologies, 2010). The State Water
Resource Control Board Division of Drinking Water (DDW) and EPA both recognize the danger of NDMA
and have set notification levels at 10 ppt. NDMA passes through unit processes such as RO because of its
small molecular weight and weak ionic charge (Trojan Technologies, 2010). Therefore, LVLAWTF utilizes
low pressure and high output UV disinfection to destroy NDMA via photolysis to levels below 10 ppt (Trojan
Technologies, 2010). Design criteria forthe plant expansion included 2-log NDMA removal and 0.5-log 1,4-
dioxane removal. 1,4-dioxane is an organic solvent used in many industrial and synthetic processes,
present at the |jg/L level in some wastewaters. It is likely to penetrate through RO membranes, and
therefore was included as a log-removal requirement in the DDW Groundwater Replenishment Reuse
Regulations. Influent levels of 1,4-dioxane have historically been low for LVLAWTF, so it was necessary to
spike the compound into the RO permeate to test the removal efficiency of AOP (Wetterau et al., 2015).
References
Chalmers, B. 2013. "High-Water Mark: Indirect Potable Reuse with a 92 percent Recovery Rate." Water Online. 18-
19.
Chang, C. 2013. "Moving Towards 100 percent Recycled Water at the Seawater Intrusion Barrier Wells, Central
Basin and West Coast Basin." WRD Technical Bulletin, Volume 25. Accessed on September 28, 2017 from
http://www.wrd.org/sites/pr/files/TB25%20-
%20Movinq%20Towards%20100%25%20Recvcled%20Water%20at%20the%20Seawater%20lntrusion%20Barrier%
20Wells%20-%20WRD%20Service%20Area.pdf
Trojan Technologies. 2010. 'Recycled Water Project, Water Replenishment District, Leo J. Vander Lans Water
Treatment Facility'.
A. 1-4

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2017 Potable Reuse Compendium
Appendix A.1 | Vander Lans AWTF
U.S. Environmental Protection Agency (EPA). 2012. Guidelines for Water Reuse, EPA/600/R-12/618. Washington
D.C.
Water Replenishment District of Southern California (WRD). 2012. Leo J. Vander Lans Water Treatment Facility
Expansion Presentation. WateReuse LA Chapter Meeting, February 14.
Water Replenishment District of Southern California (WRD). 2013. Retrieved from http://www.wrd.org/
Water Replenishment District of Southern California (WRD). 2014. WRD Increases Production of Recycled Water to
8 Million Gallons Per Day. Accessed on September 28, 2017 from http://www.prnewswire.com/news-releases/wrd-
increases-production-of-recycled-water-to-8-million-qallons-per-day-300012773.html
Wetterau, G., Fu, P., Chang, C. and Chalmers, B. 2015. Full-Scale Testing of Alternative UV Advanced Oxidation
Processes for the Vander Lans Water Treatment Facility. WateReuse California Annual Conference Proceedings.
A. 1-5

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2017 Potable Reuse Compendium
Appendix A.2 | Orange County GWRS
A.2 Orange County Groundwater
Replenishment System (GWRS) Advanced
Water Treatment Facility
Mehul Patel, Orange County Water District
Greg Wetterau and Bruce Chalmers, CDM Smith
Project Facts
Location
Size
Year of Installation
Status
Cost
Background
Orange County, California
70 MGD initial, expanded to 100 MGD
2008 initial, expansion completed in 2015
Operational
$481 million initial, $143 million expansion
Water Factory 21 was established in Orange County, California in 1976 as the first project utilizing direct
injection of recycled wastewater as a seawater intrusion barrier (EPA, 2012), The Orange County Water
District (OCWD) obtains water from the Santa Ana River, the Colorado River, the State Water Project (Delta
conveyance), local precipitation, and recycled water from the Orange County Sanitation District (OCSD)
(Wehner, 2010). Starting in 2004 and completed in 2008, the OCWD upgraded their recharge system by
superseding Water Factory 21 with the unveiling of a 70 MGD Groundwater Replenishment System
(GWRS) - the world's largest advanced water treatment system for potable reuse (Figure A.2-1).
Figure A.2-1. The world's largest wastewater recycling system for indirect potable reuse
(Photo Credit: Jim Kutzle, Orange County Water District, from GWRS, 2013)
During construction of the GWRS, the Interim Water Factory operated from 2004-2006 and produced 5
MGD of reclaimed water utilizing MF, RO, and UV-AOP with hydrogen peroxide (Wehner, 2010). This water
was blended with 8 MGD imported water before being used for groundwater replenishment and seawater
intrusion prevention. At the GWRS, influent water flows from the OCSD Plant 1 to the GWRS. After
treatment, the GWRS pipelines initially distributed 35 MGD of purified reclaimed water from the OCWD's
facility located in Fountain Valley to groundwater recharge basins (Kraemer, Miller, and Miraloma) located
A.2-1

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2017 Potable Reuse Compendium
Appendix A.2 | Orange County GWRS
in Anaheim (Figure A.2-2). The purified water flows year-round through a 13-mile long pipeline before
reaching and percolating through recharge basins that provide up to 75% of the drinking water supplied to
the northern and central parts of the OCWD (OCWD, 2014). The other 35 MGD was pumped into the Talbert
Gap seawater intrusion barrier injection wells. The plant completed an expansion to 100 MGD in 2015. The
expansion included the addition of two 7.5 million gallon equalization tanks to help increase production due
to limited availability of wastewater from OCSD Plant 1. The facility is planning a future expansion to 130
MGD and is evaluating alternatives for providing additional wastewater flows for both the current and
expanded facility. At 70 MGD, the GWRS served approximately 600,000 people. With the completed
expansion, the GWRS will produce enough water to sustain a population of 850,000 people (OCWD, 2014).
Kraemer Basin
Santa Ana River
Santiago Creek
S'JL
\Paciflc Ocean
GROUNDWATER REPIEMSHMINT SYSTEM
xaj-j/jsnd
yjmt
Figure A.2-2. Map of GWRS facilities, pipeline and recharge basins (Source: GWRS)
Treatment Type and Process Flow Block Diagram
The GWRS treatment process utilizes MF, RO, UV-AOP with hydrogen peroxide as part of the advanced
purification process follow by decarbonation and lime addition (Figure A.2-3). The MF process has a 90%
recovery rate at the GWRS; backwash from the process is sent to OCSD Plant 1 for treatment and returned
to GWRS. Each MF cell experiences backwashing every 22 minutes to prevent high-pressure buildup
(GWRS, 2013). Additionally, each microfiltration cell receives a full chemical cleaning every 21 days. The
RO process has an 85% recovery rate and the resulting brine is distributed to the OCSD ocean outfall. MF
and RO are followed by UV trains each consisting of six low pressure, high output UV reactors in series,
each with 72 lamps. Following UV disinfection, the water is stabilized to pH levels between 8.5 and 9 by
partial degasification and lime addition (GWRS, 2013).
A.2-2

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2017 Potable Reuse Compendium
Appendix A.2 | Orange County GWRS
Flow Equalization
Sodium
MF Cleaning
Compressed
MF
Hypochlorite
System
Air
Backwash
OCSD
Plant No, 1
Secondary
ttllumt
OCSD
Plant No. 1
OCSD
Ellis Ave.
Interplant Sewer
To
D;lt I il'l
Injection Wells
To
Ktmnw/MMw/
Miraloma
Spreading
Basins
Filter
Screens
MMItration
Break
Tank
RO
Transfer
Pump
Station
To
Santa Ana River
or -4-
OCSO Ocean Outfall
Decaf benator
.-¦•v. ..!•
it
RO Flush Tank
10 rlti'.h
Peak Flow ana Emergency Bypass
Ultraviolet
Irradiation System
Sodium
Bisulfite
Sulfuric
Anti-Sealant
Aod
Addition'
~ No Anri-Valant during
SAK Discharge Event

Hydrogf
Perowfc

Reverse Osmosis
¦ ¦ m '¦¦¦*«*4*
m .

To OCSD Ellis Ave.
Interplant Sewer
To OCSD Ocean Outfall
RO bypass (SAK only)	
Cartridge
Filters
FPWB
Figure A.2-3. Process Flow Diagram of Advanced Treatment at the GWRS (Source: GWRS, 2013)
The water quality of influent water to the GWRS and product water following the complete treatment process
is summarized in Table A.2-1.
Table A.2-1. GWRS influent and effluent water quality
Water Quality Parameter
Influent Levels (mg/L)
Effluent Levels (mg/L)
TDS
1,000
<30
TOC
12-15
<0.30
Pharmaceuticals
-
Non-detect (<10 ng/L)
Permitting arid Monitoring
Similar to the LVLAWTF/Alamitos Gap Barrier Injection project, the California Regional Water Quality
Control Boards are responsible for regulatory oversight of potable reuse projects in Orange County, and to
that extent, for all potable reuse projects in the State of California. The Regional Water Quality Boards issue
permits for water recycling and the State Water Resource Control Board Division of Drinking Water (DDW)
establishes the criteria used for water recycling. DDW (formerly the California Department of Public Health)
recommendations were incorporated into the original reuse permit that was issued in 2004 after Water
Factory 21 was out of commission and in the revised permit that was issued in 2015. The GWRS uses
online sensors and supervisory control and data acquisition systems to monitor real-time performance of
the treatment system. The RO process is monitored using measures of electrical conductivity (EC) and total
organic carbon (TOC). Electrical conductivity is used to measure the concentration of total dissolved solids
A.2-3

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2017 Potable Reuse Compendium
Appendix A.2 | Orange County GWRS
whereas TOC is used to measure the level of organics in the product water, and therefore gauges removal
levels. TOC also serves as a surrogate for pathogen reduction, allowing a 2-log pathogen credit to be
granted across the RO system. The UV-AOP process is monitored using a UV transmittance online sensor
and an additional sensor measuring UV power delivered.
Unique WWTP or WRF Permit Limits in the National Pollutant Discharge
Elimination System (NPDES) Permit or Additional Permit
OCSD has a source control program that strives to limit pollution from drugs/medications or industrial
chemicals, such as 1,4-dioxane, dumped into the source water. In addition to their source control program,
the OCSD has implemented additional programs such as educational outreach programs, toxics inventory,
and a pollutant ranking system in response to permit criteria set by DDW. The GWRS has received greater
than 20 awards over the years, including the coveted 2014 Lee Kuan Yew Water Prize and the 2014 U.S.
Water Prize (OCWD, 2014).
References
Groundwater Replenishment System Technical Brochure (GWRS). 2013. Fountain Valley, California.
Orange County Water District (OCWD). 2014. http://www.ocwd.com
U.S. Environmental Protection Agency (EPA). 2012. Guidelines for Water Reuse, EPA/600/R-12/618. Washington D.C.
Wehner, M. 2010. Orange County's Groundwater Replenishment System - Potable Reuse forthe Best Available Water.
PowerPoint Presentation. Tampa, Florida.
A.2-4

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2017 Potable Reuse Compendium	Appendix A.3 | Gwinnett County
A.3 Gwinnett F. Wayne Hill Water Resources
Center, Chattahoochee River and Lake
Lanier Discharge - Indirect Potable Reuse
Denise Funk and Robert Harris, Gwinnett County
Darren Boykin, CDM Smith
Project Facts
Location	Gwinnett. County, Georgia
Size	Phase I 20 MGD; Phase II 40 MGD; 60 MGD (total)
Year of Installation Phase I opened in 2001; Phase II opened in 2006
Status	Operational
Cost	$200 million initial plan construction, $350 million plant expansion, $72 million
pipeline
Background
The F. Wayne Hill Water Resources Center (WRC), an advanced water reclamation facility, was initially
constructed in 1999 on 700 acres of land located approximately 30 miles north of downtown Atlanta (Figure
A.3-1 and Figure A.3-2). The facility, which opened in 2001, currently receives influent wastewater
(primarily residential) from numerous locations throughout Gwinnett County via six large force mains, three
of which are used to divert flows from two other water reclamation facilities in the county. While the original
Phase I 20 MGD WRC was in the midst of construction, population projections predicting rapid growth in
Gwinnett County instigated the early design of a Phase II expansion to 60 MGD. Phase II design
incorporated many technological improvements to the Phase I facility.
Initially, F. Wayne Hill WRC effluent, was discharged to the Chattahoochee River through 20 miles of pipe
from the plant. However, the facility was designed to discharge reclaimed water to Lake Lanier, a US Army
Corps of Engineers (Corps) impoundment located on the Chattahoochee River. The $72 million dollar, 9.5-
mile pipeline extension to Lake Lanier started in 2008, and F. Wayne Hill WRC began discharging reclaimed
water to Lake Lanier in 2010. Lake Lanier is the drinking water supply source for Gwinnett County and the
Atlanta metropolitan region. Gwinnett County's Shoal Creek Filter Plant water intake is located less than
one mile away from the F. Wayne Hill WRC discharge point within the lake.
Figure A.3-1. Aerial view of the F.	Figure A.3-2. Map of F. Wayne Hill Water Resources
Wayne Hill Water Resources Center Center, Lake Lanier, Chattahoochee River, and Atlanta
A.3-1

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2017 Potable Reuse Compendium
Appendix A.3 | Gwinnett County
Storage and Withdrawal Rights
In July 2, 1973, Gwinnett County entered into a "Contract between the United States of America and
Gwinnett County, Georgia, for Withdrawal of Water from Lake Sidney Lanier," administered by the Mobile
District of the Corps and has since entered into several extensions and modifications to that agreement
(collectively known as the "Contract").
The Contract granted the county the right to withdraw raw water from Lake Lanier for municipal and
industrial uses at a rate of 53 MGD. The Contract also permitted the county to construct and operate
facilities to withdraw water and required the county to maintain certain records. The Contract originally
provided that either party could terminate it upon providing three years advanced notice. Unless otherwise
terminated, the Contract would continue for 30 years or until the Federal government completed its study
of area water storage, discharge, and withdrawal needs. In June 1985, the Corps gave the county notice
that the Contract would be terminated on July 1, 1989. In June 1989, the Contract was extended for six
months. That historical contract is no longer in effect; but, the county has continued to withdraw and pay
the Corps for water from Lake Lanier, which provides all of the county's raw water. From 1990 to 2000, the
county paid $9.74 per million gallon (MG) for water withdrawn. In April 2000, the Corps increased this fee
to $18.80 per MG.
The use of storage in Lake Lanier for water supply has been under litigation since 1990. The multiple
lawsuits in this litigation have been directed at the Corps. The litigation affects water supply for the entire
region. Despite a favorable appeals ruling in July 2011, there is still uncertainty regarding the quantity of
future supply that will be available. As of March 2012, the amount of Lake Lanier storage available for
municipal and industrial use, and its corresponding yield, has not been determined. As a party to the
litigation, Gwinnett County seeks to secure its water rights by obtaining storage contracts, as necessary,
pursuant to past acts of Congress. Further Congressional action, which would remove any residual doubt
regarding the use of Lake Lanier storage for water supply, is an alternative means of resolving the conflict.
The Corps has prepared an updated Water Control Manual for its dams in the Apalachicola-Chattahoochee-
Flint (ACF) Basin. The outcome of the litigation will bear upon the Water Control Manual. While Gwinnett
County will be engaged in this update through public participation channels, they plan to continue
withdrawing water from Lake Lanier and to maximize return of highly treated flows from the F. Wayne Hill
WRC.
Due to Gwinnett's geographic location at the upper end of two water basins and the absence of any sizable
or dependable groundwater aquifer source, Lake Lanier is currently the only viable source for Gwinnett
County. However, the county will continue to explore additional water supply alternatives including the
feasibility of including direct potable reuse (DPR) as a means of augmenting and diversifying its water rights
and water supply portfolio for the long-range future.
Treatment Type and Process Flow Block Diagram
Gwinnett's F. Wayne Hill WRC consists of primary and secondary biological treatment and two parallel
trains of tertiary treatment to accomplish reliability utilizing the multi-barrier approach (Figure A.3-3). One
of the two parallel trains includes chemical clarifiers and granular media filters, whereas the other consists
of chemical clarifiers and ultrafiltration. Following the two treatment trains, water is blended prior to initial
ozone disinfection, biologically active carbon filtration, and final ozone disinfection before being discharged
via pipeline to Lake Lanier and the Chattahoochee River. The plant uses packed-tower wet scrubber
technologies for odor control for its preliminary, primary and secondary treatment systems. The use of
A. 3-2

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2017 Potable Reuse Compendium
Appendix A.3 | Gwinnett County
ultrafiltration membranes for tertiary treatment makes the F. Wayne Hill WRC one of the world's largest
ultrafiltration plants,
f. Wayns Hill WRC liquid Process Flaw Diagram
Screening/ Primary
Grit Removal Clarlfier
Biological
Reactor Basin
Secondary
(larlliers
Solkls Contact
(larifiers
Chemical
ClarlAers
Granular
Media Fitters
Pre-Ozone
BAC
Filtration
Shoal Cr« k Filter Plant Process How Diagram
Lamella Plate
Clarrfiers
Ultrafiltration
Membranes
Eflhttt tO
Lain Liimr
i
Raw Water from
lake Lanier
•s-
Equaliiatron
Tank
I
Rapid Mix
HflcculatKMi
Biological
Filtration
Finithtd
Figure A.3-3. Treatment process schematic of F. Wayne Hill Water Resources Center
Permitting and Monitoring
Lake Lanier and the F. Wayne Hill WRC are both monitored for conventional wastewater parameters such
as ammonia, phosphorous, total suspended solids, pH, dissolved oxygen, chemical oxygen demand, and
fecal coliforms. Total phosphorous influent concentrations average approximately 9 mg/L, and effluent
standards are 0.08 mg/L. This criterion is low in comparison to other facilities; typical total phosphorus
standards range between 0.13 - 0.5 mg/L. Lake Lanier is monitored in both upstream and downstream
locations in proximity to the discharge outlet (Georgia EPD, 2014). The discharge from the reclamation
facility is regulated under two NPDES permits; one permit for Lake Lanier, and one permit for F Wayne Hill
WRC and Crooked Creek WRF combined discharge to the Chattahoochee River. Permit limits for Lake
Lanier are outlined in Table A.3-1.
Table A.3-1. Water quality permit limits for FWH Discharge to Lake Lanier
(Georgia EPD, 2014)
Water Quality Parameter
Permit Limit
(monthly average)
2015 Annual
Average Values
Units
Flow
40
33
MGD
Total Suspended Solids (TSS)
3
0.6
mg/L
Chemical Oxygen Demand
(COD)
18
8
mg/L
Fecal Coliform
2
1
Count/100 mL
Turbidity
0.5
.12
NTU
Ammon ia-N itrogen
0.4
.07
mg/L
Total Phosphorous
0.08
.03
mg/L
Dissolved Oxygen (DO)
7.0 (minimum)
13.2
mg/L
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2017 Potable Reuse Compendium
Appendix A.3 | Gwinnett County
References
Georgia Department of Natural Resources Environmental Protection Division (EPD). 2014. F. Wayne Hill Water
Resources Center NPDES Permit No. GA0038130. Gwinnett County, Chattahoochee River Basin, GA.
A. 3-4

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2017 Potable Reuse Compendium
Appendix A.4 | Cloudcroft
A.4 Village of Cloudcroft PURe Water
Project - Direct Potable Reuse
David Venable, Mayor, Village of Cloudcroft, NM
Eddie Livingston, P.E., Livingston Associates
Jillian Vandegrift, CDM Smith
Project Facts
Location
Size
Year of installation
Cloudcroft, New Mexico
0.1 MGD
Anticipated in 2018
Approved, 80 percent constructed, not online
$3.5 million
Status
Cost
Background
The Village of Cloudcroft, New Mexico resides at an elevation of 8,600 feet with a population of 750 people.
As a mountain resort town, the population often increases during ski season weekends and holidays to
approximately 2,000 people, resulting in an average water demand of 0.18 MGD and a peak water demand
of up to 0.36 MGD. The town has historically relied on water from springs and wells, however drought
conditions have resulted in low flows and have challenged water supply sources. In 2009, the local
community approved the construction of an advanced water treatment facility with 0.1 MGD capacity to
treat wastewater to drinking water standards.
When operational, the Cloudcroft direct potable reuse (DPR) project will be one of the first potable reuse
project implemented in New Mexico. The project, termed "PURe Water," is designed to double the water
supply of this small community.
Conservation Efforts and Project Benefits
This project will help provide Cloudcroft with sufficient water for the next 40 years. For much of the time,
the project will provide for all of the village's water demands, including aquifer recharge, fighting forest fires,
dust control, and construction. Additionally, the project will provide a clean and green energy efficient
wastewater treatment plant (WWTP), reducing wastewater discharge and sludge handling loads to landfills.
A photovoltaic (PV) electricity generating system will help to operate the water treatment facility; excess
power not consumed by the facility will be resold to the Otero Electric Cooperative.
Regulatory Leadership
Because there are no potable reuse regulations in New Mexico, the New Mexico Environment Department
(NMED) brought on the National Water Research Institute (NWRI) for regulatory assistance. NWRI
assembled an Independent Advisory Panel (IAP) of local and national water quality and public health
experts to review the Cloudcroft project and work with NMED regulators to develop potable water reuse
regulatory guidance for Cloudcroft and future projects in New Mexico. The IAP concluded that, if properly
monitored, operated, and maintained, the proposed DPR system in Cloudcroft is protective of public health
A.4-1

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2017 Potable Reuse Compendium
Appendix A.4 | Cloudcroft
and should be permitted for operation. The detailed analysis of this project by the NWRI Expert Panel can
be obtained from NWRI (NWRI, 2015).
DPR System
Wastewater from the local community will undergo multi-barrier treatment, blending with raw water, and
additional water purification processes prior to being used for potable consumption and aquifer recharge.
The project converts the existing trickling filter system at the WWTP (Figure A.4-1) to a membrane
bioreactor (MBR) process (operational in 2017). Once the remaining construction is completed, the MBR
permeate will be stored in an 80,000-gallon water storage tank at the WWTP site (Figure A.4-2), with a
chloramine residual to minimize biofouling.
Following storage, MBR permeate will be pumped a half-mile to another 80,000-gallon storage tank (Figure
A.4-2), and will flow by gravity to the Water Purification Facility, five miles away. Using only the pressure
resulting from gravity flow through the pipeline, the MBR permeate will pass through a RO system, followed
by advanced oxidation using ultraviolet light (UV) and hydrogen peroxide, chlorination, and discharge into
a 1 MG covered and lined reservoir (Figure A.4-3).
Figure A.4-1. Wastewater treatment plant
Figure A.4-2. WWTP site aerial view
¦QBasir
Membrane
Bioreactor
Tower Tank
Injection
Well
Cloudcroft, NM ,
RO/UF
future ASR
Figure A.4-3. PURe water pipeline from WWTP to water treatment facility
(Courtesy of Eddie Livingston from Livingston Associates)
RO permeate will be blended with existing spring and groundwater at a blend ratio of approximately 50
percent. Up to 180,000 GPD (0.18 MGD) of the blended water will be treated utilizing ultrafiltration (UF),
A.4-2

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2017 Potable Reuse Compendium
Appendix A.4 | Cloudcroft
UV disinfection, granular activated carbon (GAC), and final chlorine disinfection. After this treatment, the
product water will be introduced into the village's water distribution system.
Concentrate resulting from the RO process, along with UF backwash water, will be stored in a 300,000-
gallon open-top reservoir. This water will be put to beneficial uses such as gravel washing and dust control.
There will also be the option to dispose of concentrate using deep-well injection, as illustrated in Figure
A.4-3.
Purification Process Details
As previously stated, the Cloudcroft treatment train is a multiple barrier purification process: WWTP (MBR)
—> RO —> UV/AOP with H2O2 —> Chlorine disinfection —> Storage and 50% Blending with spring water —> UF
—> UV —> GAC —> Chlorine Disinfection —> Distribution System (as shown in Figure A.4-4).
WASTEWATER
MEMBRANE

REVERSE

UV

CHLORINE
BIOREACTOR

OSMOSIS

AOP

DISINFECTION
BLENDING
WELL/SPRING
CHLORINE

ACTIVATED

UV
DISINFECTION

CARBON

DISINFECTION
ULTRA-
FILTRATION
WATER DISTRIBUTION SYSTEM
Figure A.4-4. Village of Cloudcroft PURe water treatment process flow schematic
(Courtesy of Eddie Livingston from Livingston Associates)
The MBR has been designed for full nitrification-denitrification with a target five-day biochemical oxygen
demand (BODs) of less than 5 mg/L and total nitrogen less than 1 mg/L. The gravity fed RO system will
operate with a recovery between 75 and 80 percent and maximum feed pressure of 175 psi. The UV system
utilizes a dose exceeding 500 mJ/cm2 with a peroxide dose between 4 and 5 mg/L. Following UV, free
chlorine contact will achieve additional disinfection.
Following blending, the UF system, which will be permitted as a drinking water system, will operate at a
recovery of 90 to 95 percent and will include online integrity testing through pressure decay and turbidity.
UV disinfection, following the UF, will achieve pathogen reduction with a target dose of 40 mJ/cm2. The
GAC will operate with an empty bed contact time of 10 minutes. A final free chlorine contact will achieve
final disinfection.
DPR Microbial Log Removal Requirements
As designed, the series of multi-barrier treatment processes provides a robust barrier to pathogens and
trace pollutants, based on criteria established by NMED and the IAP (Salveson, 2014; NWRI, 2015). Table
A.4-1 shows the pathogen log reduction values for the PURe Water project. The log reduction values
achieved using these consecutive treatment processes exceed those as recommended by California for
IPR and Texas for DPR (Salveson, 2014), although the methods used to calculate the credits differ from
those used in the other states. One item worth noting is that the MBR used for pretreatment of the RO was
A.4-3

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2017 Potable Reuse Compendium
Appendix A.4 | Cloudcroft
given considerably less Cryptosporidium and Giardia reduction credit than the UF and MF membranes used
at advanced treatment facilities in California and Texas. This difference is attributed to the methods used
for integrity monitoring in these systems rather than any inherent differences in the membranes. The UF
membranes employed in the drinking water facilities at Cloudcroft received Cryptosporidium and Giardia
credits similar to those in California and Texas.
Table A.4-1. Pathogen credits obtained from treatment process
(Source: Adapted from Salveson, 2014)
Treatment
Process
Disinfection
Credits
Pathogen
Cryptosporidium
Giardia
Enteric Viruses
MBR
2
2
2
RO
1.5
1.5
1.5
UV
6
6
6
Free chlorine
0
1
4
UF
4
4
3
UV
4
4
0.5
GAC
0
0
0
Free chlorine
0
1
4
Total
17.5
19.5
21
References
Livingston, Eddie. 2015. Village of Cloudcroft PURe Water Project - Direct Potable Reuse.
NWRI. 2015. Developing Proposed Direct Potable Reuse Operational Procedures and Guidelines for Cloudcroft, New
Mexico. NWRI IAP Report. September, 2015.
Salveson, Andrew. 2014. Visions in Potable Reuse: Research. Research Solutions. Spring 2014: 11-12.
A.4-4

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2017 Potable Reuse Compendium
Appendix A.5 | Big Spring
A.5 Colorado River Municipal Water District
Raw Water Production Facility Big Spring
Plant - Direct Potable Reuse
Background
This direct potable reuse (DPR) project is a Colorado River Municipal Water District (CRMWD) project
providing water to the communities of Big Spring, Stanton, Midland, Odessa, and Snyder. The CRMWD's
service area overlaps with the Chihuahuan desert to the west, thus water is always in short supply. In 2002,
CRMWD began looking at ways to use sources of water that had not previously been considered for
municipal water use. A reuse feasibility study was performed in 2005 that covered an analysis of municipal
effluent quantity and quality, preliminary contact with regulators, costs, and a public outreach strategy,
amongst other things (Sloan et al., 2010). Non-potable uses such as irrigation and industrial applications
were considered, as well as indirect potable reuse (IPR); but, DPR was chosen partially due to poor
expected performance from an environmental buffer located in the Permian Basin (Khan, 2013). Big Spring
has very high levels of dissolved solids in their surface water, and dry air conditions cause high evaporation
rates. Forthese reasons, IPR via discharge to surface water bodies proved infeasible and would likely result
in a loss of product water (Sloan, 2013). Additionally, non-potable reuse tends to be seasonal and the
opportunities for non-potable reuse in Big Spring were few and far between. Instead, CRMWD initiated a
goal to "reclaim 100 percent of the water, 100 percent of the time" (Sloan et al. 2010). Pilot testing on the
raw water production facility was completed in 2009 (Sloan et al., 2010). Refer to the previous Big Spring,
TX case study in the 2012 Guidelines for further background and lessons learned (EPA, 2012).
In 2012, during a period of record drought throughout Texas, one of the reservoirs on the Colorado River,
Lake Spence, which provides water to Big Spring, dropped to as low as 0.2 percent full (Sloan, 2013).
Fortunately, in 2013 the 3.7 MGD Big Spring WWTP started to transfer 2.5 MGD of treated secondary
effluent to a newly constructed raw water production facility (RWPF) that purifies the water to drinking water
quality (Figure A.5-1).
John Grant, Colorado River Municipal Water District
Susan Crawford and Jillian Vandegrift, CDM Smith
Project Facts
Location
Size
Year of Installation
Big Spring, Texas
1.8 MGD
2013
Operational
$14 million
Status
Cost
A.5-1

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2017 Potable Reuse Compendium
Appendix A.5 | Big Spring
CRMWD
MM won PROflOCTlOM WCIUTT
BIO SfflfflG PLANT
MM'
Figure A.5-1. CRMWD raw water production facility (Source: TWDB, 2015)
Treatment Type and Process Flow Block Diagram
The conceptual treatment process for the Big Spring DPR scheme is illustrated in Figure A.5-2. Filtered
secondary effluent from the Big Spring WWTP is transferred to a 1.8 MGD raw water production facility in
which microfiltration (MF), RO, and UV-AOP using hydrogen peroxide treat the water to drinking water
quality (Figure A.5-3). It should be noted that this simplified schematic does not show chemical feed
facilities used at the existing water treatment plant, such as coagulant and disinfectant. The UV-oxidation
treatment destroys low molecular weight compounds such as NDMA, which is a suspected carcinogenic
compound (EPA, 2014). The UV-oxidation system achieves 1,2-log reduction of NDMA and 0.5-log
reduction of 1,4-dioxane (Trojan UV, 2012). The CRMWD RWPF product water is then blended with
CRMWDs raw water supply before being treated by the Big Spring, Stanton, Midland, Odessa, and at
times Snyder conventional water treatment plants. The water treatment plants use rapid mix, flocculation,
sedimentation, media filtration, and disinfection methods. Recycled water constitutes approximately 15-
20 percent of the total blended water volume.

Frlm«-y Clarrliem
Hpb Utfriinrs
Atftfign ftssr^
CMarirflban
~J nprMMUvninr
-QJ—
Wastewater Irwimcrrt

I
31
*
f
I;-
HFwrw
.—Chrnmii
MirnErjr«* I
I lllrtttinn
UVQtfldviian
Acclaim
Treatment
Rsw warier
Ri-wrvc r
wntpr Trs-iimnn1
HapU Mbi
f )QL>C uLj Ben's
an
Fibers
Figure A.5-2. Big Spring DPR conceptual schematic (Source: Sloan et al. 2010)
A.5-2

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2017 Potable Reuse Compendium
Appendix A.5 | Big Spring
J.B. Thomas
^Reservoir
Big Spring
Water
Treatment
Plant
Big Spring
CRMWD
Raw Water
Production
Facility
Big Spring
Wastewater
Treatment
Plant
Red Draw
Reservoir
Figure A.5-3. Treatment flow diagram representing City of Big Spring WWTP, CRMWDs RWPF, and
Individual Water Treatment Process for Individual Customers (Source: CRMWD)
Energy
In total, Big Spring water reclamation uses 5.34 kWh/1000 gallons for membrane treatment, UV oxidation,
and source water and product water pumping collectively (Sloan, 2013). This is only slightly higher than the
energy required to bring water to Big Spring from Lake Spence and to divert water from Beal's Creek so it
does not enter the Colorado River, totaling approximately 5.04 kWh/1000 gallons. Comparing the two
energy requirements illustrates an important concept; the energy avoided from raw water pumping to
Big Spring is more or less equal to treating municipal wastewater effluent to drinking water quality (Sloan
etal., 2010).
Disposal
Concentrate from the RO process is discharged to Beal's Creek under a permit obtained by CRMWD. Beal's
Creek is a naturally brackish stream. CRMWD operates a brackish water system to divert low flow, high
chloride water with an off-channel reservoir, where water is stored before being sold to oil companies or
evaporated (Sloan et al. 2010). Membrane filtration backwashing waste is directed to the head of the
WWTP, where it then flows through the treatment process instead of disposing of the waste elsewhere off-
site (Sloan et al., 2010).
Permitting and Monitoring
As with other Texas potable reuse projects and in the absence of state enforced potable reuse guidelines,
Texas Commission on Environmental Quality (TCEQ) reviewed the project proposal in accordance with its
case-by-case exception approval process. The letter that grants the exception, which functions as a permit
for the facility, includes requirements on treatment, design, operation, and monitoring. Subsequent to pilot
testing, TCEQ set water quality requirements for the system which is permitted to produce raw water for
municipal and industrial use. The original requirement for source water to the RWPF was to achieve
turbidity levels less than 10 NTU and a 4-log reduction of virus through the RWPF. Furthermore, the
A.5-3

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2017 Potable Reuse Compendium
Appendix A.5 | Big Spring
blending percentage, initially limited to 20 percent reclaimed water, was later amended to allow up to 50
percent reclaimed water.
The raw water production facility underwent an intensive period of testing in January 2013 in which
regulated drinking water contaminants, secondary contaminants, unregulated radionuclides, and
unregulated trace chemical constituents were monitored and documented. TCEQ required the following
other regulatory actions before project implementation: concentrate discharge permit, reclaimed water use
authorization (from TCEQ reuse group), industrial pretreatment permit (for membrane filtration backwash),
a membrane pilot study, and a plan and specification review. One of the major stresses when planning
potable reuse projects, beyond the public perception, has been operator certification and training. As
mentioned in the Wichita Falls case study, TCEQ places significant emphasis on the ability of the plant
operators to manage all processes and mitigate when necessary. One of the TCEQ requirements was that
the facility must be under the supervision of a Class B licensed operator (Sloan, 2013).
Between November 2013 and May 2015, the RWPF underwent a detailed, independent operational and
water quality evaluation conducted on behalf of the Texas Water Development Board, which concluded that
"the RWPF produces water of very high quality [which is] more than sufficient to serve as a raw water
source" (Steinle-Darling et al., 2016).
References
Khan, S. 2013. Drinking Water Through Recycling: The Benefits and Costs of Supplying Direct to the Distribution
System. Report of the Australian Academy of Technological Sciences and Engineering, funded by the Australian
Water Recycling Centre of Excellence through the Commonwealth Government's Water for the Future initiative.
Sloan, D.; Wingert, C.; Cadena, I. 2010. Potable Reuse in the Permian Basin. Accessed on September 28, 2017 from
https://www.freese.com/sites/default/files/Potable%20Reuse%20in%20the%20Permian%20Basin.pdf.
Sloan, D. 2013. Direct Raw Water Blending in Big Spring. 2013 Direct Potable Reuse Specialty Conference
Presentation.
Steinle-Darling, E., A. Salveson, J. Sutherland, E. Dickenson, D. Hokanson, S. Trussell, and B. Stanford, 2016, Direct
Potable Reuse Monitoring, Final Report to the Texas Water Development Board under contract no. 1348321632, co-
funded by Water Environment and Reuse Foundation underTailored Collaboration No. 14-10, December, 2016.
Trojan UV Solutions. 2012. UV Oxidation-Raw Water Production Facility (RWPF) Big Spring, Texas. Accessed on
September 28, 2017 from
http://www.troianuv.com/resources/troianuv/casestudies/ECT/Direct Potable Reuse Big Spring Texas Case S
tudy.pdf.
TWDB. Water Reuse. Retrieved January 2015 from http://wviAw.twdb.texas.gov/innovativewater/reuse/.
U.S. Environmental Protection Agency (EPA). 2012. Guidelines for Water Reuse, EPA/600/R-12/618. Washington D.C.
U.S. Environmental Protection Agency (EPA). 2014. Technical Fact Sheet-N-Nitroso-dimethylamine (NDMA). Office
of Solid Waste and Emergency Response. EPA 505-F-14-005.
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2017 Potable Reuse Compendium	Appendix A.6 | Wichita Falls
A.6 Wichita Falls River Road WWTP and
Cypress WTP Permanent IPR and
Emergency DPR Project
Daniel	Nix and Russell Schreiber, City of Wichita Falls
Project Facts
Location	Wichita Falls, Texas
Size	DPR: 5 MGD; IPR: 16 MGD
Year of Installation	DPR: 2014; IPR: potentially 2018
Status	DPR: Decommissioned; IPR: Planning stages
Cost	DPR: $13 million; IPR: projected $33.5 million
Background
Lake Arrowhead and Lake Kickapoo are the main surface water supplies forthe City of Wichita Falls, Texas.
During 2013, both lakes were less than 35 percent full (Figure A.6-1), sending Wichita Falls into extreme
drought conditions with no readily available water supply solution (Khan, 2013).
Figure A.6-1. Lake Arrowhead levels in 2013 (Photo credit: Daniel Nix)
By May 2014, Wichita Falls declared a Stage 5 drought. Wichita Falls, however, proactively began
investigating the possibility of implementing a DPR project following the drought of 1995-2000 during which
they supplemented their drinking water supply with highly saline water from Lake Kemp and Lake Diversion
(Dahl, 2014). By using microfiltration (MF) and RO, they were able to integrate the treated saline lake water
with the existing potable water supply. Wichita Falls Public Works Department was confident they could do
the same with municipal wastewater when faced with the most recent drought conditions. In 2012,
recognizing the city wouid be out of water by 2014 without further action, Wichita Fails drafted a two-phase
project plan involving both a permanent IPR scheme and an emergency temporary DPR scheme.
A.6-2

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2017 Potable Reuse Compendium
Appendix A.6 | Wichita Falls
Conservation Efforts
By December 2014, staged water conservation efforts saved up to 6,1 billion gallons of water (about 1,5
years' supply). Stage 5 drought restrictions had lowered the average summer usage by 65 percent.
Nonetheless, conservation alone was insufficient to sustain a reliable drinking water supply (Nix, 2014).
Emergency (short-term) DPR System
The DPR scheme was implemented because drought conditions led to severe and abrupt drinking water
needs for the City of Wichita Falls, with lake levels well below the 40 percent considered to be an
emergency. The emergency DPR project began operating online on July 9, 2014 after only 27 months of
design, permitting, and construction. The city expected the temporary DPR system to remain in operation
for 2-2.5 years, at which time the permanent IPR system would come online. Due to significant rainfall, the
DPR project was decommissioned on July 21, 2015.
A unique context in Wichita Falls was that the city already had an MF/RO plant that treated the Lake Kemp
water. This MF/RO system was scheduled to be taken offline because the salinity in Lake Kemp had
increased dramatically (going from the normal 2500 ppm total dissolved solids (TDS) to 8000 ppm TDS),
The Lake Kemp MF/RO system could not successfully treat this higher TDS water. Reusing the facility kept
costs and time down because design and construction of a new membrane plant was not needed.
The DPR system transferred treated effluent from the River Road WWTP to the Cypress water treatment
plant (WTP) through 13 miles of pipe that were laid in 3 months - all above ground. The pipeline was sized
for the future permanent IPR system and will be reused. By laying the pipeline through the city's flood
control channels, the city did not face any right of way issues.
At. the Cypress WTP, the treated effluent was purified through MF and RO. A disinfection-dose UN/ system
was added after six months of operation. The UV dose employed targeted pathogen inactivation, but was
not designed to address unregulated constituents, such as n-nitrosodimethylamine (NDMA), or provide
advanced oxidation. The advanced-treated water was then blended at a 1:1 ratio with raw, untreated Lake
Arrowhead water and subsequently treated at a conventional WTP, followed by holding in an engineered
storage buffer for 24 hours before being sent to the distribution system. The process created an additional
5 MGD (up to 50 percent of daily demand) of municipal drinking water. 2.5 MGD of brine from the MF and
RO processes was discharged to the Big Wichita River under the discharge permit acquired for the Lake
Kemp operation (Figures A.6-2 A and B) (Nix, 2014).
Figure A.6-2 A. RO permeate	Figure A.6-2 B. RO modules
(Photo credit: City of Wichita Falls)	(Photo credit: City of Wichita Falls)
A.6-3

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2017 Potable Reuse Compendium
Appendix A.7| Occoquan Watershed
Permanent (long-term) IPR system
The IPR project will use the existing 13-mile pipeline constructed for the DPR project to complete the 15-
mile pipeline from River Road WWTP to Lake Arrowhead. Wichita Falls has received a new discharge
permit from TCEQ for the permanent IPR installation. The IPR project will ultimately pipe up to 16 MGD of
advanced treated (i.e., tertiary) effluent from River Road WWTP back to Lake Arrowhead, which will serve
as an environmental buffer, before the water is treated at the city's conventional WTPs and distributed to
customers. River Road WWTP will be retrofitted with a new phosphorous reduction process, tertiary
filtration processes, and a new pump station using loan money to fund the upgrades (Ingle, 2014).
Treatment Process
DPR
WWTP —~ Pipeline (including chloramine disinfectant down the pipeline) —~ WTP (MF —~ RO —~ UV) —~
Holding Lagoon (engineered storage buffer) —* Blending 50-50 Conventional WTP (chlorine dioxide pre-
disinfection, chloramine primary disinfection, coagulation, lime, sedimentation, gravity media filtration,
fluoridation, chloramine terminal disinfection) —>¦ Storage (engineered storage buffer) (Figure A.6-3)
7.5 MGD down an 12.3 mile pipeline
River Road Wastewater Treatment Plant
Permit ID: TX0047686
Distribution System
Cypress Water Treatment Facility
MF/RO Plant
Conventional Plant
Fe(S04};
MF Filters
Clarifier
NahSO
Break
Tank
h-so
Scale Inhibitor
5 MGD
RO
Permeate
RO Filters i
•v=t.


Ground Storage
Tanks
4
Clearwell
Granular Filtration
H-SlF
Blended
Phosphate



I
*T~
Sedimentation
Restabilization c°i
Fe(SO+);
Splitter
Box

Cb NHj
1 1.

/
Cation ic
PolymeF"
Coagulation
Secondary Reservoir
2.5 MGD MF/RO Reject

Figure A.6-3. Emergency DPR treatment process flow diagram (Source: Daniel Nix)
IPR
River Road WWTP (upgrades will include chemical phosphorus reduction with filters and new re-aeration)
—> Effluent Pump station and pipeline —> Lake Arrowhead (environmental storage buffer) -s Conventional
WTP.
A. 7-4

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2017 Potable Reuse Compendium
Appendix A.7| Occoquan Watershed
Collaboration between TCEQ and City
Although there are no IPR or DPR regulations currently implemented in Texas, TCEQ reviews submitted
project proposals individually and grants approval and discharge permits on a case-by-case basis. TCEQ
approved the Wichita Falls DPR scheme after reviewing the DPR project proposal and the proposed long-
term IPR system solution. Since there are no regulatory guidelines for DPR in Texas, TCEQ and the City
of Wichita Falls Public Works Department collaboratively discussed the necessary treatment requirements
and effluent limitations.
DPR Permitting Process
The city worked with TCEQ for the first 9 months of 2013 to discuss how to operate the plant and received
the approval to build the pipeline towards the end of 2013. Following the completion of the DPR system
installation in December 2013, TCEQ worked with the city on carrying out an intense 45-day testing period,
followed by 30 additional days of testing. During this full-scale verification testing, TCEQ staff spent time
onsite understanding how the plant was operating and observing the lab operations. Based on the results
from these full-scale verification test periods, TCEQ approved a permit on June 28, 2014 which allowed six
months of operation. TCEQ has subsequently extended the permit based on excellent operation but
required the addition of UV after the initial six months of operation.
DPR Microbial Log Removal Requirements
TCEQ used the Surface Water Treatment Rules (SWTRs) as the basis for assigning log removal
requirements. However, to be more conservative than required by the SWTRs, rather than using a 24-
sample average concentration as the basis for assigning log removal requirements, they took the maximum
concentration ever observed, and applied this standard to viruses, Giardia, and Cryptosporidium, rather
than only Cryptosporidium as required by the SWTRs.
The DPR process is required to achieve 9-log virus removal, 8-log Giardia removal, and 5.5-log
Cryptosporidium removal as specified by TCEQ. Initially, TCEQ had required 8-log virus removal but
increased it to 9-log because chloramines were pre-forming at the wastewater plant, and therefore TCEQ
felt that there would not be as much free chlorine disinfection occurring. Likewise, TCEQ initially required a
lower Giardia removal target (6-log) but increased it to 8-log removal required after continuous effluent
monitoring indicated higher concentrations of Giardia could be present in the treated wastewater than the
maximum concentration observed previously. These adjustments show the adaptability on the part of TCEQ
to changing conditions and the open communication between the regulators and the city with the common
goal of protecting public health.
Because no daily integrity test has been demonstrated to the satisfaction of the TCEQ to date for RO, it
does not give microbial log removal credits forthe DPR RO elements. As a result, other employed treatment
methods must successfully achieve the log removal requirements.
IPR Permitting Process
TCEQ approved the permit forthe IPR system in Fall 2014 which allowed the city to go forward with design.
The system is funded with a $33.5 million loan through the Texas Water Development Board and the Clean
Water Act State Revolving Fund. The city is in the midst of a required archaeological investigation along
the pipeline route and the design process and expects to have the permanent IPR system online and
upgrades to the River Road WWTP complete by 2018.
A.7-5

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2017 Potable Reuse Compendium
Appendix A.7| Occoquan Watershed
DPR System Monitoring
The city worked with TCEQ in a collaborative process to decide upon 42 monitoring locations and
requirements within the DPR system to ensure public health was protected and off-speculation drinking
water was prohibited from entering the distribution system (Figure A.6-4). The range of chemical and
microbial constituents required for monitoring of the temporary DPR scheme were similar to the current
Safe Drinking Water Act (SDWA) requirements. Constituents in the SDWA were monitored in the
wastewater effluent, RO permeate before blending, lake water, and at the end of the conventional WTP.
TCEQ required bi-weekly monitoring of Cryptosporidium, Giardia, and total culturable viruses using
standard methods, A polymerase chain reaction (PGR) based method was also tried for Cryptosporidium
and Giardia during verification testing but was removed from the monitoring requirements because PCR
results were difficult to interpret. Other monitoring parameters included E. coli (daily); full metal scans; algal
counts; inorganic, organic, radioactive, and secondary chemicals specified under Texas drinking water
codes; and disinfection by-products. The city monitored unit processes to ensure that the required microbial
log removals are being met. For example, every eight hours, log removal credits for each disinfection zone
were calculated based on disinfectant concentration and contact time. The log removal values were entered
into a table with values from other unit processes and an overall observed log removal was tabulated. The
DPR process regularly provided a calculated 25-log removal for viruses and 16-log removal for Giardia
(compared to the 9- and 7-log removal requirements, respectively).
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Appendix A.7| Occoquan Watershed
Operator Certification
The City of Wichita Falls has historically produced high-quality drinking water, and prides itself on its plant
operator certification system. Wichita Falls plant operators must be certified by the State of Texas and
continue training throughout their career lifetime. They can achieve certification levels A through D, A being
the highest achievable level. Operators must be recertified every three years (City of Wichita Falls, 2014a).
In total, the City of Wichita Falls has five class A operators, 19 class B operators, and 11 class C operators
(City of Wichita Falls, 2014).
Because there are no specific regulations regarding operator certification for reuse, Wichita Falls
implemented two additional requirements for its operators. First, water operators are required to tour the
wastewater plant, so they would understand the wastewater treatment processes. Second, water operators
are required to take basic wastewater, wastewater treatment, and waterborne pathogens classes. Likewise,
wastewater operators are required to tour the water treatment plant and take basic water, surface water,
and waterborne pathogens classes. There is currently an ongoing effort to determine and begin a certified
DPR operator program in Texas.
Collaboration between the County Public Health Department and the City's
Public Works Department
The city had an existing local water quality task force that was established in 1997 in response to the
Milwaukee Cryptosporidium outbreak. The task force is made up of members of the City's Public Works
Department and the City/County Public Health Department. The task force has met regularly and has
established protocols for what action and communication is required in the case of unexpected process
upsets or disease outbreaks observed in the population. TCEQ has attended one of the task force meetings
to observe how information and data are exchanged. This relationship is unique and helps to guarantee
public health safety.
Leadership
The Director of the City's Public Works Department and the Utilities Operations Manager were trailblazers
with DPR. However, they also felt that the science was already proven and there was nothing innovative
technically - all of the components had been previously studied for four decades or more. Wichita Falls
simply did extensive research to assemble and digest published literature from the U.S., Australia, Europe,
and Japan, and then put the pieces together.
Public Outreach
Public outreach techniques were used to educate doctors, professors of environmental science and
chemistry, and the general public (Dahl, 2014). Ensuring the community was comfortable with the potable
reuse concept immensely helped the project's evolution. The leadership of the Public Works Department
feels that the DPR and IPR projects have been 100 percent transparent with the citizens and that they could
not have succeeded without the support of the community.
Public Perception
City and state officials did not receive any complaint calls regarding taste during DPR operations. In fact,
some residents felt the water tasted better since the DPR scheme was brought online.
The Public Works Department monitored bottled water sales at the three large Walmart retailers in town.
Water bottle sales increased by about 9 percent after DPR was brought online, indicating that some
residents may have switched from tap water to bottled water for drinking; but the majority of the population
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Appendix A.7| Occoquan Watershed
did not begin buying bottled water. City residents have embraced their place in history as a leader in DPR
(Figure A.6-5).
Figure A.6-5. T-shirts sold in Wichita Falls touting DPR (Photo credit: F5 Concepts, Inc.)
References
City of Wichita Falls. 2014. Wichita Falls Direct Potable Reuse Project: Complete Detail. Retrieved December 2014
from http://www.wichMfallstx.gov/DocumentCenterA/iew/21987.
Dahl. R. 2014. "Advanced Thinking: Potable Reuse Strategies Gain Traction." Environmental Health Perspective.
122(12): A332-A335. Published online Dec 1, 2014. doi: 10.1289/ehp.122-A332
Ingle, John. 2014. 'Water board approves Wichita Falls loan'. Wichita Falls Times Record News.
Khan, S. 2013. Drinking Water Through Recycling: The Benefits and Costs of Supplying Direct to the Distribution
System, Report of the Australian Academy of Technological Sciences and Engineering, funded by the Australian
Water Recycling Centre of Excellence through the Commonwealth Government's Water for the Future initiative.
Nix, D. 2014. City of Wichita Falls Water Conservation and Emergency Direct Potable Reuse. PowerPoint
Presentation at North Central Texas American Waterworks Association Meeting
WICHITA FALLS. TX
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2017 Potable Reuse Compendium	Appendix A.7 | Occoquan Watershed
A.7 Potable Water Reuse in the Occoquan
Watershed
Robert W. Angelotti, Upper Occoquan Service Authority
Thomas J. Grizzard, PhD, P.E., Virginia Tech
Project Facts
Location	Fairfax, Virginia
Size	54 MGD
Year of Installation Initial (1978): 15 MGD; 1987: 27 MGD; 1993: 32 MGD; 2003: 54 MGD
Status	Operational
Cost	Replacement value of owned infrastructure exceeds $0.5 billion
Background
The Occoquan Reservoir is a critical component of the water supply for approximately 1.8 million residents
of Northern Virginia, a highly-urbanized region located west of Washington, D.C. Figure A.7-1 shows an
aerial photo of the Occoquan Reservoir above the dam in the vicinity of the raw potable water plant intakes
Reclaimed water from the reservoir represents a significant supplement to potable water supply yield
and has been successfully augmenting the drinking water supply for nearly four decades.
Figure A.7-1. Aerial view of the Occoquan Reservoir
(Photo Credit: Roger Snyder, Manassas, Virginia)
Rapid transformation from a largely rural to a predominantly urban/suburban region began in the 1960s
as a result of unprecedented growth from the westward expansion of the urban core of Washington, D.C.
By the mid-1960s, this urbanization was adversely affecting water quality of the Occoquan Reservoir,
resulting in an unplanned and unintended indirect potable reuse scenario, where 11 small wastewater
treatment plants were discharging effluent upstream of the reservoir. Poorly treated wastewater with urban
and agricultural runoff threatened the continued use of the Occoquan Reservoir for public water supply.
In 1971, the Virginia State Water Control Board (VDEQ) and the Virginia Department of Health (VDH)
adopted a plan to protect the Occoquan Reservoir as a drinking water supply. The Occoquan Policy
mandated a newly conceived framework for water reuse and set in motion the first planned and intentional
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Appendix A.7 | Occoquan Watershed
use of reclaimed water for supplementing a potable surface water supply in the United States (EPA,
2012).
The Occoquan Policy mandated the creation of a regional state authority, the Upper Occoquan Service
Authority (UOSA), to provide collection and reclamation of wastewater, and the Occoquan Watershed
Monitoring Program (OWMP) to continuously monitor the watershed and reservoir, provide independent
water quality assessments, and provide advice on protective measures for the reservoir. By the 1970s,
Fairfax Water was responsible for potable water production and distribution for much of Northern Virginia,
The VDEQ and VDH were also highly involved in developing the ultimate solution.
While water quality improvement was the primary driver for implementing planned and intentional potable
water reuse in the Occoquan system, supplementing the raw water supply was always an underlying
objective. Although the mid-Atlantic region of the United States is not considered dry or arid, the population
density results in stressed water supply and limited per capita water availability. This situation becomes
more pronounced during periodic extended drought conditions.
Treatment Type and Process Flow Block Diagram
A diagram illustrating how the UOSA reclamation system interacts with the drinking water supply is
provided in Figure A.7-2. The UOSA reclamation plant produces about 35 MGD(1535 L/s) of water
on an annual average basis, and the plant has the capacity to reclaim as much as 54 MGD (2,365 L/s).
A future plant flow of around 65 MGD is projected for the build out condition of the UOSA service area.
Future reclaimed water production is anticipated to effectively double the safe yield of the Occoquan
Reservoir. Although the majority of water produced supplements the drinking water supply, an additional
1 to 3 MGD (44 to 131 L/s) is delivered for non-potable uses on the UOSA campus.
FAIRFAX WATER POTABLE
WATER TREATMENT PLANT
Figure A.7-2. The UOSA Reclamation Plant provides an important source
of water for the service area (Schematic credit: CDM Smith for UOSA)
Water reclamation at UOSA employs a multi-barrier approach to treatment, includes large volumes of
engineered storage, and incorporates a high-level of redundant and resilient features designed to deal with
plant, local, or regional failures. The water reclamation process includes preliminary and primary
treatment, followed by complete mixed activated sludge with biological nitrogen removal. Advanced
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Appendix A.7 | Occoquan Watershed
water treatment processes include lime precipitation and two stage recarbonation with intermediate
settling. These processes stabilize organic matter, remove nutrients, and act as barriers to pathogens and
heavy metals. Final polishing is accomplished with multimedia filtration, granular activated carbon
adsorption, freechlorination and dechlorination. Blended water is withdrawn from the reservoir and treated
at the Fairfax Water Potable Water Treatment facility utilizing flocculation, settling, ozonation, biofiltration
with GAC, free chlorination, and final chloramination prior to distribution. The UOSA Reclamation Plant
treatment process is outlined in Figure A.7-3.
Conventional Treatment
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Permits and Regulated Monitoring
The initial permit that authorized delivery of reclaimed water flow to the Occoquan Reservoir was capped
at 10.9 MGD. The flow limit was increased to 15 MGD soon after successful operation of the reclamation
plant was demonstrated. The first plant expansion began operation in 1987 and increased capacity from
15 MGD to 22.5 MGD. Rapid development continued in the region, which furthered capacity needs. By
2003, the plant was expanded to a 54 MGD production capacity. Increased production of high quality water
from the UOSA plant is crucial to maintain water quality in the Occoquan Reservoir; it offsets higher non-
point pollutant loads that result from increased urbanization within the watershed.
A few of the concentration limits provided in UOSA's operating permit are shown in Table A.7-1 The
plant is highly automated and extensively monitored using industrial control computers. Performance is
continuously determined using a broad array of online monitoring techniques implemented to improve
operational reliability. The quality of online instrument measurements is verified with field and central
laboratory monitoring and an asset centric, dynamic process model can be used to compare predicted
values with those produced from the plant's laboratory information management and supervisory control
and data acquisition (SCADA) systems. A watershed monitoring subcommittee convenes regularly to
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Appendix A.7 | Occoquan Watershed
ensure that sufficient monitoring and reclaimed potable water treatment has occurred and that water
quality and plant performance continuously meets expectations.
Table A.7-1. Examples of UOSA's product water requirements (source: Occoquan Policy)
Water Quality Parameter
Product Water Requirement
Concentration (Monthly Average)
COD (mg/L)
< 10
Total Suspended Solids (mg/L)
< 1
Nitrogen (TKN) (mg/L)
< 1
Phosphorous (mg/L)
< 0.1
Turbidity (NTU)
< 0.5
Total Conforms (CFU/100 mL)
< 2
Water produced at the UOSA plant meets all federal primary and secondary drinking water standards with
exceptions for nitrate and occasionally TDS. Seasonally, the nitrate drinking water standard is exceeded
purposefully to accomplish specific reservoir water quality goals to retard the release of undesirable
contaminants from the hypolimnion when the reservoir is thermally stratified. TDS above the secondary
drinking water standard may occur during prolonged periods of dry weather. Historically, this has not
been a significant issue because dilution occurs downstream after UOSA's product water is blended with
the native reservoir source waters (which contains a much lower TDS concentration).
Unregulated Compounds and Voluntary Monitoring
The potable reuse scenario implemented within the Occoquan Watershed applies a multiple barrier
approach to deal with trace organic compounds. The first barrier to such contaminants is a source control
program that builds upon the framework offered by the Federal Pretreatment Program for publicly owned
treatment works (POTWs). UOSA's source control program emphasizes the need to protect its product
water for beneficial use as a supplement to the local potable water source. This important aspect is
considered when issuing pretreatment permits to significant industrial users. There are a host of additional
barriers that further ensure that the potable water is safe for end users. These are listed below.
1.	Biological degradation and transformation - suspended growth activated sludge at long solids
retention time with nitrification and denitrification followed by two stages of bio-filtration at the UOSA
facility. Further biological treatment occurs through natural bio-decay in the environmental buffer
and finally further degradation occurs in ozone enhanced bio-filtration at the potable water
treatment plant.
2.	Solids partitioning and absorption - onto biologically and chemically flocculated solids at the UOSA
facility, in stream and reservoir portions of the environmental buffer and through the flocculation
and settling stages of the potable water treatment plant.
3.	Volatilization - via extended aeration at the UOSA facility and in the free-flowing stream portions
of the environmental buffer.
4.	Hydrolysis - occurs at high pH through the lime treatment portion of the UOSA facility.
5.	Physical/chemical adsorption - onto granular activated carbon at both the UOSA and potable water
treatment facilities.
6.	Oxidation - by free chlorine at the UOSA and Fairfax Water facilities and again by ozone at the
drinking water plant.
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Appendix A.7 | Occoquan Watershed
7. UV photolysis - in open storage tanks at the UOSA facility, in the reservoir and again at the drinking
water plant.
A significant amount of voluntary monitoring is performed to confirm that the water produced is safe for use
by the community. UOSA typically monitors for selected microbial pathogens and around 300 unregulated
compounds in its finished product water at least annually. The watershed program monitors for trace
organic compounds in the reservoir water column, sediments, and fish tissue at several reservoir monitoring
stations on a biannual or quarterly basis. Raw source and finished drinking waters are analyzed quarterly
for unregulated compounds and results are posted publicly on the internet. Bioassays are used to
demonstrate that the product water yields no toxic, estrogenic, or other undesirable biological outcomes.
Years of accumulated data support the conclusion that there is no significant increased risk to public health
that results from supplementing the reservoir water supply with the reclaimed water product.
Management Practices and Institutional Considerations
Today, the concept of indirect potable reuse is well-communicated to regulators and public official
stakeholders within the region. Interested parties within local municipalities are aware that a significant
portion of the water supply is comprised of reclaimed water. Both Fairfax Water and UOSA are run by
a board of directors. Board members are representatives for their community and make decisions in the
best interest of the communities they serve. It is not uncommon for UOSA to collaborate closely with
representatives of local governments about issues relating to water quality.
The community and the independent water quality monitoring entity, OWMP, both openly acknowledge
that the reclaimed water produced by UOSA is the most reliable and highest quality water entering
the Occoquan Reservoir. The OWMP has a technical advisory panel that is comprised of members from
EPA, VDEQ, VDH, and an expert from an accredited and well-renowned academic institution within the
state (Virginia Polytechnic Institute and State University, otherwise known as Virginia Tech). This
provides even greater confidence and credence for potable reuse in the region.
Periodically, water related issues within the region result in the formation of technical advisory groups,
citizen action committees, and task forces. These may be composed of agency stakeholders, city or
county government officials, community representatives, water experts, and interested citizens.
Examples of issues tackled by such groups include the following: land zoning around the reservoir to
protect water quality, siting of a major semiconductor industry within the UOSA service area, and
consumptive use of reclaimed water by a proposed power plant. These collaborative efforts with
interested and affected parties are used to gather input before important decisions are made that might
impact water quality or its availability to users.
Cultural and Social Considerations
When water reclamation was first proposed, a number of hearings were conducted to explain what was
to be implemented and to provide the public a venue to express their views. UOSA has always engaged
in an active program to provide tours to local students, from grade school through college, during which
potable reuse is thoroughly explained. These tours have been conducted for nearly 40 years, providing
public outreach to the local population on the importance of UOSA's mission. In addition, UOSA maintains
a public website where its role in potable water reuse is clearly expressed. UOSA's success has not
required dedicated public relations staff or a formal public outreach and communication program.
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Appendix A.7 | Occoquan Watershed
Successes and Lessons Learned
Perhaps the greatest key to success of this project is that it was implemented specifically to improve
water quality problems in the existing surface water reservoir being used as the drinking water supply.
The project was initiated by the Commonwealth of Virginia via state regulation (the Occoquan Policy)
that was developed by the VDEQ and VDH. Early water quality problems in the Occoquan Reservoir
were clearly articulated, and the best solution for the region was presented to stakeholders and
interested citizens. Although water quality was the major driver, it was clearly recognized that treated
wastewater flows returned to the reservoir would be a significant and valuable resource in the future.
This project is unique in that there is a separate watershed management program (OWMP), along with
its associated water quality monitoring laboratory, that provides oversight, independent accountability
and recommendations to the water reclamation agent (UOSA), the potable water treatment and
distribution entity (Fairfax Water), and the state regulatory agencies. This was critical in establishing a
credible voice of endorsement and recommendation for the plan. Collaboration among major
institutional entities that work toward the common goal of protecting and improving reservoir water
quality demonstrates leadership for water related issues to the community. Nearly 40 years of
successful implementation has demonstrated confidence that the original plan is still working well
today.
References
U.S. Environmental Protection Agency (EPA). 2012. Guidelines for Water Reuse, EPA/600/R-12/618. Washington D.C.
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