An Overview of Water Recycling in the United States
Dennis M. Diemer1
Water Environment Research Foundation
Board of Directors (Vice Chair)
1. Introduction
Water recycling is a growing practice in many regions of the world. Countries andregions in which water reuse is on the rise include the United States (U.S.), WesternEurope, Australia, and Israel. In the U.S., the practice of recycling water is a large andgrowing industry. An estimated 3.4 billion gallons per day (bgd) (13 million m3/d) isreused in the U.S. However, this is but a small fraction of the total volume ofwastewater generated. According to the U.S. Environmental Protection Agency’s(EPA) 2000 Watershed Needs Survey, a total of 34.9 bgd (132 million m3/d) of
municipal wastewater effluent is produced. Thus, the proportion currently reusedamounts to only 9.7%, suggesting that future potential for recycling treated wastewater
is enormous.
2. Discussion
There are a number of factors that drive water reuse in the U.S., including thatrecycled water is a drought-resistant and reliable local supply, the increasing demand
for water as the population grows, preservation of limited potable water supplies fordrinking, that recycled water is a method for wastewater disposal, the economic
feasibility of recycled water projects with well-established technology, and thatrecycled water is an integrated part of public policy particularly in states with limited
water supplies.
Recycled water use on a volume basis is growing at an estimated 15% per year in theU.S. All evidence suggests that water recycling will play an expanded role in water
management in the 21st century, not only in the semi-arid western states and “sunbelt”
states, but perhaps in all 50 states. At a compound annual growth rate of 15%, thevolume of recycled water would amount to 12 bgd (45 million m3/d) by the year 2015.
The early applications of water reuse were for irrigation of landscaping; this is nolonger the case, however. Other applications include industrial reuse, irrigation ofedible and non-edible agricultural crops, commercial uses such as toilet flushing in
high-rise office buildings, groundwater recharge, and indirect potable reuse. Industrial
reuse applications include use in cooling towers and for boiler feedwater. In Sonomaand Monterey Counties in California, lettuce, artichokes, strawberries, and grapes areirrigated with recycled water. There are several well known examples of indirect
potable reuse around the world, including a facility in Orange County, California.
Water recycling represents a viable, long-term solution to the challenges presented by
growing demands for water. Recycled water has numerous benefits, including a local,
dependable water supply that is drought-resistant and under local control, reduction oftreated wastewater discharge to sensitive or impaired surface waters, reduction ofimported water and avoided costs associated with importing water, environmental
benefits, and that it represents a sustainable water resource.
Recycled water regulations vary across the U.S. from state to state. There are nonational standards. In general, the highest treatment is required for the highest use toensure adequate level of protection of public heath. California has the most stringent________________________________
1375 Eleventh Street, Oakland, California 94607-4240 U.S.A. e-mail: dennisd@ebmud.com- 153 -regulations (Title 22 as set by the Department of Health Services) in the U.S. In Title
22, Chapter 4, of the California Code of Regulations, bacteriological water quality
standards are established based on the expected degree of public contact withrecycled water.
The technologies used most frequently in California for treatment prior to groundwater
recharge are microfiltration (MF), reverse osmosis (RO), and ultraviolet disinfection(UV). Many California experts believe that in the future, virtually all wastewater
treatment plants, especially those that discharge into the Bay-Delta surface waters, willfeature filtration of some type. Groundwater recharge requires that a municipal utility
purify water to a higher quality than most natural water resources. Clear, treatedwastewater is subjected to three purification processes in order to produce clean waterthat is allowed to filter through the ground by natural filtration processes (e.g., the paththat rainwater takes) into deep aquifers in an underground basin, where it will beextracted by wells for drinking water after mixing with exiting groundwater supplies forat least a year. The first of these three purification processes is MF, which uses a lowpressure membrane that takes small suspended particles and other materials out of
the water. MF efficiently prepares water for the RO process.
Technologies employed to treat recycled water in the U.S. depend almost entirely on
the application, which is called “highest treatment for highest use.” For example, if
the primary application is irrigation or cooling tower water, sand or dual media filtration
after secondary treatment is sufficient to achieve a state’s water quality criteria. If, on
the other hand, the intended application is indirect potable reuse, sophisticatedtechnologies such as MF, RO, and UV disinfection must be employed to ensurechemical and microbiological safety of the recycled water. Although membranes are
not required for all applications of water reuse, it is becoming the technology of choice
as the pricing becomes more competitive.
The cost for a water agency to implement recycled water projects vary across the U.S.
from minimal to over $2,000 per acre-ft ($1,5/m3). Variable factors include proximity tousers, federal and state funding availability, subsidies offered, and retrofit users or newdevelopment. Projects are more cost effective where there is a large user located inclose proximity to the source of recycled water, as compared to projects where anextensive distribution system is needed to reach a number of smaller users. Federal
and state funding can help offset project costs. For example, some types of federal
funding can offset up to 75% of project costs. Some water wholesalers offer subsidies
to water retailers to encourage implementation of recycled water projects in order tooffset demand for imported potable water supplies. The Metropolitan Water District ofsouthern California offers the West Basin Municipal Water District $250 per acre-ft($0.2/m3) for recycled water produced. Another variable involves whether a new
development is mandated to use recycled water. In this case, the water agency canoften negotiate with the developer to pay for a substantial portion of the recycled waterproject costs. With retrofit customers, a large industrial user may have more incentive
and capital available to help jointly fund a recycled water project than smaller, irrigation
users.
Some of the principal issues, barriers, and impediments to widespread water reuse
include the need for further public education, lack of available funding, better
documentation of the economics of water reuse, consistent regulations that enable
protection of public health, and the need for additional research.
As for public perception and acceptance, while non-potable reuse applications (e.g.,landscape irrigation) are generally acceptable, as reuse moves toward indirect potable- 154 -

reuse, the reaction from the public – usually in the form of negative publicity in themedia – becomes more negative. More focus and consideration should be given tothe psychological factors that lead to the public’s resistance to indirect potable reuse.
A survey of municipalities in California several years ago revealed that the major
constraint to water recycling is lack of funds. Although many larger municipalities haveconstructed recycled water projects, smaller utilities have not, often due to lack offunding support from Federal and/or state governments.
There is the need for additional research on water recycling issues, including
development of innovative and emerging technologies that could lower projects costs,
testing and monitoring methods, and emerging issues relating to public andenvironmental heath such as the emergence of endocrine disrupting compounds andpharmaceutically active compounds.
3. Conclusion
Water recycling already represents an important water supply in many areas of theworld. Reuse is growing in importance in the U.S., Australia, Europe and other regions.
Its potential is largely untapped, however, due to a number of barriers. Water reuseshould not be viewed as simply the reuse of wastewater effluents. Rather, water reuseshould be viewed as one of several alternative sources of new water, all of which willbe important tools in the toolkit of the water manager of the 21st century.
Both water professionals and the consuming public will need to view water differently
in the 21st century. It is incumbent upon the consuming public that they develop moretrust in the ability of water utilities to treat any poor quality (impaired) water to drinking
water or higher standard. Similarly, water professionals must earn that trust. Water
will finally be recognized for its inherent great value in the 21st century as demand
grows and readily available and inexpensive supplies remain at virtually the same level.
The water community should strive to convey the value of water through a variety ofmeans, including education of the public and elected officials.
References
Miller, G. Wade, “Integrated Concepts in Water Reuse: Managing Global WaterNeeds,” 2005
Talley, Pick, Presentation at the American Water Works Association Annual
Conference in San Antonio, TX, June 14, 2006

- 155 -Outline• Background – global water supply• Water recycling in the U.S.

Overview of Water Recycling in
the United States– Driving factors– Projected increase– Applications– Benefits– Regulations– Treatment technologies– Costs– Areas of increased emphasis needed

Japan-U.S. Conference on Drinking Water Quality andWastewater Control
January 22, 2007

2

Areas of Water Stress in2020

Supply vs. Demand
Population &Demand

SupplyorDemand

Available
WaterTime
3

4Factors Driving Water Recycling in
the U.S.

Population Growth in the U.S.

• Drought-resistant/reliable supply• Population growth/increasing demand for water• Preserving limited potable water supplies fordrinking• Wastewater disposal• Ecosystem and environmental protection• Economically feasible• Well-established technology• Public policy and integrated water planning
56

Projection of Water Recycling inthe U.S.
Projected Water Reuse
2001 to 2015
50

Potential for Water Recycling• Approximately
9,7% of municipal
wastewater
effluent in the U.S.
is currently
recycled or reused

2015

Million Cubic Meters per Day

45
40
35
30
25

9,7%Recycled2015105

Municipal effluent in the U.S. = 132 million m3/d0

2001

2007

Year

78- 156 -90% of Water Reuse Occurs inFour States

However, Water Reuse is Growing
in Other States

Washington
MontanaVermont

North Dakota

Washington

Maine

Montana

MinnesotaOregon
Idaho

Wisconsin

South Dakota

Nebraska

NevadaUtah
California

Arizona

Iowa

Pennsylvania
Illinois Indiana

Ohio

Colorado

New Mexico

New York

Michigan

WyomingKansasMissouriOklahoma

Arkansas

West
Virginia

Kentucky

Minnesota
Idaho

Nebraska

NevadaUtah
California

Virginia

South
Carolina

HawaiiPennsylvania
Illinois Indiana

Arizona

New Mexico

Oklahoma

Mississippi

Texas

Iowa
Ohio

Colorado
KansasNew York

Michigan

MissouriWest
Virginia

KentuckyNorth
Carolina

Tennessee

Alabama

Massachusetts
New Hampshire
Wisconsin

South Dakota
Wyoming

New Jersey
DelawareMaryland

MaineVermont

North Dakota

OregonNew Hampshire
Massachusetts
Rhode Island
Connecticut

Rhode Island
Connecticut

New Jersey
DelawareMaryland

Virginia

North
Carolina

Tennessee

South
Carolina

Arkansas
Mississippi

Georgia

Alabama
TexasLouisiana

GeorgiaLouisiana

FloridaFloridaHawaii

910Water Recycling
Not Just for Irrigation

Industrial Use

RecycledWater
Commercial
Toilet Flushing

Applications of Recycled Water• Landscape irrigation• Agricultural irrigation• Industrial and commercial• Non-potable urban uses (toiletflushing in high-rise commercialbuildings)• Environmental uses
• Groundwater recharge• Potable water supply augmentation

Residential Lawns

Commercial Use
Recreational Use

1112

Benefits of Recycled Water

Recycled Water Regulations• Local, dependable water supply• Drought-resistant• Reduces wastewater discharge to surfacewaters• Reduces uses of imported water• Benefits the environment• Sustainable supply• Regulations vary across the U.S.
• No national standards in the U.S.
• In general, highest treatment required forhighest use• California has the most stringent
regulations (Title 22), as set by theDepartment of Health Services

1314

Treatment Technologies for
Recycled Water

Good News:RO Technology Costs Fall• Conventional treatment– Media (sand) filtration– Chlorination or ultraviolet (UV) disinfection

4$/m33• Advanced treatment– Microfiltration and reverse osmosis (RO) membranes– Membrane bioreactor– UV disinfection

1.5
0.5

• Membranes are becoming the technology ofchoice around the world as the best available
technology for water purification1950 1960 1970 1980 1990 2000
AWWARF Study, 2001

15- 157 -16

West Basin Water Recycling Plant
El Segundo, California

Costs of Recycled Water Projects

Conventional ProcessTitle 22FilterFlocculation
Basin• Costs for a water agency to implement
recycled water projects vary across theU.S. (minimal to over $1,5/m3)

To Distribution
113.500 m3/d
Disinfection

Membrane Treatment Process
Lime
ClarifierBarrier
FilterReverseOsmosis

MicroMicrofiltration

ReverseOsmosis

ReverseOsmosis

ReverseOsmosis• Variable factors:

To Sea Water Barrier
18.900 m3/d

– Proximity to users– Federal and state funding availability– Subsidies offered– Retrofit or new development

Disinfection

To Sea Water Barrier
9.500 m3/d
Disinfection

MicroMicrofiltration

To Chevron
Boiler Feed18.900 m3/d

1718

Areas of Increased Emphasis
Needed for Water Reuse

Conclusion• Further public education• Funding assistance from federal
and state governments• Better documentation ofeconomics• Consistent regulations thatenable protection of publichealth• Additional research• Water recycling is growing in the U.S.
• Water recycling is also increasing inAustralia, Europe and other regions of theworld• Opportunities for water recycling arenumerous in the future as population anddemand increase

1920

Title 22 Regulations

Thank YouDennis M. Diemer
Board of Directors, Vice Chair
Water Environment Research Foundationwww.werf.org(510) 287-0101
dennisd@ebmud.com

21

Treatment
Level

Treatment Required

Total Coliform(MPN) Limit

Turbidity Limit

Disinfected
Tertiary(UnrestrictedUse)

Filtration & chlorine
disinfection or otherforms of disinfection
to inactivate 99.999%virus

Median <= 2.2 per
100 mL (7 days),
Max <= 23 per 100
mL (30 days),
Max <=240 per 100mL

Conventional filtration(2 NTU avg, <= 5 NTU
5% of time, <= 10 NTUmax)
Membrane (<= 0.2 NTU
5% of time, <= 0.5 NTUmax)

Disinfected
Secondary 2.2(RestrictedUse)

Secondary, oxidized,
disinfectedMedian <= 2.2 per
100 mL (7 days),
Max <= 23 per 100mL (30 days)

None

Disinfected
Secondary 23(RestrictedUse)

Secondary, oxidized,disinfected

Median <= 23 per
100 mL (7 days),
Max <= 240 per 100mL (30 days)

None22- 158 -