Technical BRIEF
INNOVATIVE RESEARCH FOR A SUSTAINABLE FUTURE
www.epa.gov/research
Onsite Non-Potable Water Reuse Research
Advancing the safe adoption of smaller scale systems for recycling locally collected water
Background
Increasing pressures on water resources has led to greater
water scarcity and a growing demand for alternative water
sources in many parts of the United States In response,
many communities have initiated or are developing
treatment systems for planned reuse of stormwater
runoff, and various domestic/municipal wastewaters.
Although there are several types of water reuse, this fact
sheet is focused on EPA's onsite non-potable water reuse
research. This fit-for-purpose water reuse is one solution
that can help communities collect, treat and reuse water
for non-drinking water purposes. Onsite non-potable
water reuse systems (ONWS), such as the one shown on
Page 2, capture, treat, and reuse water at a building or
district scale. The treated water is then used onsite or in a
local area for non-drinking water purposes, such as toilet
flushing, clothes washing, and ornamental plant irrigation.
Collaborative Efforts
EPA is collaborating with states and utilities who are
facilitating the development of ONWS to define treatment
and monitoring approaches that will ensure adequate
safety and to build the utility business case for
implementing such systems. EPA researchers are
committed to active engagement with various partners
and stakeholders to ensure that water reuse practices are
protective of public health. One of these partners, the
National Blue Ribbon Commission (NBRC) for Onsite Non-
Potable Water Systems, is a nationwide group of utilities,
state and local public health agencies, and federal
agencies interested in advancing the use of ONWS at the
building- or district-scale to recycle various types of locally
collected water, such as wastewater, source separated
graywater, stormwater runoff, and rainwater.
Defining Challenges
Initial partnership meetings identified a definition of
appropriate water quality "criteria" that indicated
adequate treatment and the associated monitoring
approach to verify on-going performance of the system as
key roadblocks to responding to the increasing number of
requests to permit ONWS. While existing criteria and
Blackwater:
Wastewater from
toilets, dishwashers
kitchen sinks,
and utility sinks
Greywater:
Wastewater from
clothes washers,
bathtubs, showers,
and bathroom sinks
Rainwater: Precipitation
collected from roofs and
above-grade surfaces
Air Conditioning Condensate:
Water collected from evaporator coils
Stormwater:
Precipitation
collected at or
below grade
Foundation Drainage:
Nuisance groundwater
from dewatering operations
Within a building, several M>citer sources are generated that
can be treated and used onsite or in a local area for non-
drinking water purposes, such as toilet flushing, clothes
washing, and ornamental plant irrigation.
(Original photo credit: San Francisco Public Utilities Commission)
monitoring guidelines did exist for some reuse options,
guidance varied greatly from state to state,
in addition to the need for standardization, the existing
approaches for setting and monitoring treatment
performance were not risk-based. In other words, the level
of the water quality parameters used to verify safety was
not based on a quantitative assessment of the exposure
risk to pathogens during the projected reuse. A systematic
evaluation of exposure risks for the range of locally
collected wastewaters for different non-potable end uses
was clearly needed to provide a basis for defining
treatment and monitoring. Finally, while utilities identified
several drivers for implementing ONWS, ranging from
addressing water scarcity to the development of green
space within urban areas, quantifiable data was needed on
the life cycle impacts and costs to build the business case
for implementation.
Research Focus
EPA's onsite non-potable water reuse research is focusing
on three areas: (1) risk-based modeling to define the
necessary level of treatment to safely reuse locally
collected wastewater for non-potable purposes in and
around buildings; (2) describing and quantifying the
microorganisms, both bacterial and viral, found in these
wastewaters to define improved targets for monitoring
U.S. Environmental Protection Agency
EPA/600/F-18/342 October 2018

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treatment performance; and (3) life cycle assessment
(LCA) and life cycle costing to understand relative
cost/benefits of various forms of ONWS.
Risk Based Modeling
EPA researchers are conducting risk-based modeling to
define the necessary level of treatment to safely reuse
several locally collected wastewaters for non-potable uses
in and around buildings. Specifically, quantitative microbial
risks assessment (QMRA) models were developed to
define the level of potential risks from using locally
collected wastewaters for non-potable purposes. The
models also predict the level of pathogen removal that
would be required to achieve acceptable risk benchmarks.
The reduction targets for each of the three major groups
of waterborne pathogen risks (viruses, bacteria and
protozoans) provide specific performance metrics for
treatment systems. This research also includes evaluation
of the initial concentrations of pathogens in the different
wastewaters and the risks associated with ONWS cross-
connections.
Recent Research Publications:
•	Human health impact of non-potable reuse of distributed
wastewater and grevwater treated by membrane
bioreactors (2018)
•	Human health impact of cross-connections in non-potable
reuse systems (2018)
•	Risk-based enteric pathogen reduction targets for non-
potable and direct potable use of roof runoff, stormwater,
and grevwater (2017)
•	Simulation of enteric pathogen concentrations in locally-
collected grevwater and wastewater for microbial risk
assessments (2017)
•	Review of pathogen treatment reductions for onsite non-
potable reuse of alternative source waters (2017)
Monitoring of Treatment Performance
A critical component of ONWS is the need for
identification of indicators that can be used to monitor
treatment effectiveness with regard to the reduction of
microbes. To address this, research was done to identify
common gray water contaminants, including bacteria,
viruses, and human mitochondrial DNA, and evaluate the
impact of treatment on these potential indicators. The
goal of this work is to define improved targets for
monitoring treatment performance.
Recent Research Publications:
•	Reducing inherent biases introduced during DNA viral
metagenome analyses of municipal wastewater (2018)
•	Characterization of the relative importance of human-and-
infrastructure-associated bacteria in grey water: a case
study (2015)
•	Human mitochondrial DNA and endogenous bacteria
surrogates for risk assessment of grevwater reuse (2014)
Life Cycle Assessment (LCA)
From the perspective of the local utility or government,
the implementation of ONWS must account for the costs
of installing and operating the ONWS relative to the
benefits derived. To provide insight from a system level
perspective, life cycle costs and environmental impacts
were assessed for ONWS of various scales and types.
Recent Research Publication:
• Energy and greenhouse gas life cycle assessment and cost
analyst of aerobic and anaerobic membrane bioreactor
systems: Influence of scale, population density, climate,
and methane recovery (2018)
Additional Information
Websites:
•	EPA's Onsite Non-Potable Water Reuse
epa.gov/water-research/onsite-non-potable-water-
reuse-research
•	National Blue Ribbon Commission for Onsite Non-
Potable Water Systems
uswateralliance.org/initiatives/commission
Guidelines:
•	EPA's 2012 Guidelines for Water Reuse
nepis.epa.gov/Exe/ZvPURL.cgi?Dockey=P100FS7K.txt
•	2018 Guidebook for Developing and Implementing
Regulations for Onsite Non-Potable Water Systems
uswateralliance.org/sites/uswateralliance.org/files/nb
rc%20guidebook%20for%20developing%20onws%20r
egulations.pdf
•	2017 Risk-Based Framework for the Development of
Public Health Guidance for Decentralized Non-
Potable Water Systems
nwri-usa.org/pdfs/SIWM10C15 Decentralized-Non-
Potable-Water-Svstems.pdf
Contacts:
•	Jay Garland, Principal Investigator
garland. jay(S>epa.gov
•	Michelle Latham, Communications
latham.michelle(5)epa.gov
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U.Sv Environmental Protection Agency

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