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TABLE OF
CONTENTS
Article Summaries / Case Studies
INDIRECT POTABLE REUSE (WATER RECYCLING)
In traditional water systems, raw water is diverted from a
source, such as a stream, lake, or aquifer, and treated before being distributed
to consumers for drinking water. After use by consumers, wastewater is
collected, treated and discharged to a receiving water body, often to the same
one from which raw water is diverted. The discharge of treated wastewater occurs
downstream of the raw water diversion.
In many places in the United States unplanned indirect
potable reuse is being practiced. Unplanned potable reuse occurs when treated
wastewater discharged from an upstream community is subsequently withdrawn for
drinking water use downstream by another community. The fraction of wastewater
effluent in the raw drinking water can vary significantly depending upon the
relative amounts of native water and effluent. In some cases, more than half of
the water in rivers used as a drinking water source comes from wastewater
discharges.
In planned indirect potable reuse systems, treated wastewater
is intentionally used to augment water supplies. Rather than discharging treated
wastewater downstream of the raw water diversion, it is returned upstream. The
treated wastewater mixes with native water and then is diverted and treated for
potable use.
Fundamental to the practice of planned indirect potable reuse
is the concept of multiple barriers to remove contaminants. These barriers
include wastewater treatment, dilution and natural cleansing in the water body,
effective drinking water treatment, and extensive raw and treated water
monitoring to ensure high quality drinking water.
Planned indirect potable reuse systems should incorporate a
number of safety measures beyond those normally included in conventional water
systems. These barriers to potential contaminants include advanced wastewater
treatment, the receiving water, and the water treatment system. Facility
redundancy and increased water quality testing enhance system reliability.
There are a number of successful planned indirect potable
reuse systems in operation across the country. There are systems in California,
Virginia and Texas that provide safe drinking water to citizens every day.
Several of these systems have been operating for over 25 years. Studies have
shown that there are no health effects, long or short term, as a result of
consuming reclaimed water.
The proposed Cottonwood Water and Sanitation District (CWSD)
and Arapahoe County Water and Wastewater Authority (ACWWA) planned indirect
potable reuse project will have multiple barriers to produce safe water for
their consumers. Wastewater is treated at the Lone Tree Creek Wastewater
Treatment Plant (LTCWWTP). This advanced treatment plant provides biological
nutrient removal followed by membrane microfiltration and disinfection. The
plant successfully removes nitrate and phosphorous, as well as pathogens. The
highly treated effluent would be discharged into the Cherry Creek alluvium, an
aquifer influenced by surface water flow in Cherry Creek. The water will seep
through the sandy alluvial material taking about 18 months to reach the supply
wells. While travelling through the alluvium, the water will be further filtered
and diluted with native flows. After reaching the supply wells, the water will
be treated in a new advanced water treatment facility. The treatment will
include a reverse osmosis membrane process to remove organic and pathogenic
contaminants. The clean water from the membrane process will then be disinfected
and distributed to CWSD and ACWWA customers.
Recent articles on the subject of planned indirect potable
reuse were researched. The following literature review of these articles
includes title, author(s), date, and a summary of the main points.
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Recharge Project Overcoming Impediments to Water
Recycling: The San Gabriel Valley Groundwater , Hartling, Earle C.,
and Margaret H. Nellor, WEFTEC 2000.
- Initially developed in 1989, the San Gabriel Valley Groundwater Recharge
Project is a 25,000 AFY project. Tertiary treated effluent from the
Sanitation Districts of Los Angeles County San Jose Creek West WRP is used
to surface recharge a potable water aquifer in the San Gabriel Valley. A
10,000 AFY "demonstration" was scheduled for completion in late
2001.
- California DHS required 450 mg-min/L CT (chlorine residual multiplied by
contact time) and a minimum of 90 minutes contact time (peak dry weather
flow) for 5-log virus inactivation.
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Use of Recycled Water to Augment Potable Supplies: An
Economic Perspective, Potable Reuse Committee, WateReuse
Association, Sept. 1999.
- The East Valley Water Recycling Project, proposed by the City of Los
Angeles Department of Water and Power, has an ultimate capacity of 35,000
AFY. The water would be used for industry, irrigation, and groundwater
recharge of potable aquifers. The estimated cost of the project is $478 per
acre-foot.
- The Groundwater Replenishment System operated by the Orange County Water
District and Orange County Sanitation District employs reverse osmosis and
UV disinfection of secondary treated wastewater. The effluent is disposed of
at existing spreading basins or injection wells for replenishment of
groundwater supply and seawater intrusion control barrier, respectively. The
existing capacity will be 68,000 AFY by 2003, and the ultimate capacity is
20,000 AFY. The cost of the project is estimated to be $565 per acre-foot.
- The City of San Diego Water Purification Project would construct a system
with a capacity of 15-20,000 AFY. The system would include microfiltration,
reverse osmosis, ion exchange and ozonation to treat North City WRP tertiary
effluent. The project would also include the construction of a pipeline to
the San Vicente water supply reservoir. The estimated cost of the project is
$1,060 per acre-foot.
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Development of Regulations for Potable Water Reuse in
Georgia, Hall, Ken C., WEFTEC 2000.
- The key points of the paper are: the provision of multiple barriers to key
pollutants, provision of reliability and redundancy, use of demonstrated
technologies, protection of public health, and importance of public
perception.
- In order to reuse treated wastewater to augment the water supply, the
draft guidelines would require two barriers for suspended solids, three
barriers for pathogens, and one barrier each for both metals and total
organic carbon.
- Biological nutrient removal, nanofiltration, and reverse osmosis are
considered barriers for suspended solids, pathogens, metals, and total
organic carbon. Microfiltration and ultrafiltration are considered barriers
for suspended solids, pathogens, and total organic carbon. Disinfection is
considered a barrier for pathogens.
- Based on this, the proposed project would include three barriers for
suspended solids, five barriers for pathogens, two barriers for metals, and
two barriers for total organic carbon. This does not include the aquifer,
which is not considered in the guidelines.
- The guidelines also include monitoring and effluent limits for the
wastewater treatment plant. Turbidity, TOC, and total coliform limits would
be imposed on the wastewater discharge. For discharges to water supplies,
Turbidity would be sampled every 4 hours and the maximum limit for any
sample would be 5.0 NTU. TOC would be monitored daily and the maximum
monthly average would be 10 mg/l. Total coliforms would be sampled daily,
and at least 75% of the results shall be less than detect and no sample
shall exceed 25 cfu/100 ml.
- Semiannual samples for giardia and cryptosporidium shall be taken and
analyzed for discharge to water supply reuse. Results shall always be less
than detect.
- There would also be finished water quality requirements. Reclaimed water
shall not cause violation of water quality standards of the receiving water
body in addition to standards set forth in guideline. Priority pollutant and
SDWA parameters shall be analyzed semiannually.
- Indirect potable reuse is the preferred option for potable reuse. It has
also been proven safe after years of unintentional practice.
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Developing Indirect Potable Reuse to Increase Water
Supply, Improve Water Quality and Manage Wastewater Discharge
in Orange County, California, Anderson, Blake P., Thomas M. Dawes,
Gregory L. Leslie, Donald F. McIntyre, William R. Mills Jr., J.E. Norman,
Wendy Sevenandt, and T.S. Snow, WEFTEC 2000.
- Three phase, 100,000 AFY Groundwater Replenishment system to recharge
local groundwater basin by Orange County Water District and Orange County
Sanitation District.
- System design based on new regulatory guidelines, which include complete
treatment with a process designed to reduce the concentration of TOC.
Additional treatment with a process to remove TDS might be required to
comply with local groundwater quality objectives.
- The use of ultrafiltration and microfiltration as pretreatment for reverse
osmosis is the industry standard for indirect potable reuse.
- California DHS requires 2,000 foot horizontal separation and a one-year
detention time between the point of injection and extraction for indirect
potable reuse projects.
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East Valley Water Recycling Project: Challenges of
Implementation, Van Wagoner, William T., WEFTEC 2000.
- City of Los Angeles Department of Water and Power project will ultimately
provide 35,000 AFY of tertiary treated recycled water for groundwater
recharge, irrigation, and industrial uses.
- Three-year demonstration project started in September 1995, providing
10,000 AFY for groundwater recharge.
- Proposed requirements state that water extracted from the ground may not
contain more than 20% recycled water over the course of a five-year running
average.
- Groundwater recharge regulations specify that monitoring wells be placed
one fourth and half of the distance between the spreading grounds and the
closest domestic production well.
- Extensive public involvement program. Six public hearings, nine press
releases, a media open house, 46 newspaper articles, numerous television
news reports, project information bill stuffers, a project hotline
telephone, numerous project fact sheets, a project description was published
on the Department’s website, and two full page color articles in the Los
Angeles Times were all part of the program. The program began in 1990
and ran through April 2000.
- Project currently under review by City Council.
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Microfiltration and Reverse Osmosis Pilot Testing for
Indirect Potable Reuse at the University Area Joint Authority,
Book, Brian L., Steven M. Siegfried, Stephen T. Welch, and Jason D. Wert,
WEFTEC 2001.
- Pilot testing facility constructed to determine the feasibility of
reclaiming 3.0 mgd of secondary effluent for water reuse and streamflow
augmentation.
- Commercial and industrial customers will use effluent, followed by
discharge to Slab Cabin Run. The discharge will mix with several State
College Borough Water Authority supply wells, and the Pennsylvania
Department of Environmental Protection determined the expected treatment
level for indirect potable reuse.
- "Microfiltration/Ultrafiltration is not sufficient alone to
completely produce recycled water that meets all established water quality
limits." Nitrates, TDS, and TOC are of concern to this project (all of
these would be removed by reverse osmosis, BNR would remove nitrate).
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Indirect Potable Reuse and Aquifer Injection of Reclaimed
Water, Beverly, Sharon D., William J. Conlon, and David F. MacIntyre,
AWWA Water Sources Conference Proceedings 2002.
- Membranes followed by ultraviolet disinfection provides multiple effective
barriers.
- Pilot study in Orlando, Florida looked at reinjecting water into aquifer
or augmenting lakes for potable reuse.
- Reverse Osmosis is not always necessary to reach desired water quality.
- All indirect potable reuse projects would have to meet Florida Maximum
Contaminant Levels for Direct Aquifer Injection. These MCLs include primary
and secondary drinking water standards, TOC less than 3.0 mg/l, total
organic halides less than 0.2 mg/l, and total nitrogen less than 10.0 mg/l.
- Membrane fractionation studies showed that NF removed all contaminants
except nitrate. 50 Daltons was the effective molecular weight cutoff for
nitrate. This cutoff is designated as an RO membrane.
Thomas, and Tama Snow, WateReuse Association Newsletter,
1998.
- National Research Council (NRC) report entitled Issues in Potable
Reuse: the Viability of Augmenting Drinking Water Supplies with Reclaimed
Water in March 1998.
- Careful, thorough, project-specific assessment that includes contaminant
monitoring, health and safety testing, and system reliability evaluation is
required for indirect potable reuse projects.
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The Ongoing Evolution of Water Reuse Criteria,
Crook, James, AWWA Water Sources Conference Proceedings, 2002.
- The California Water Recycling Criteria were updated in 2000. The updated
criteria include total coliform limits and required treatment for
groundwater recharge by spreading are determined on a case-by-case
evaluation.
- Disinfection requirements of 2000 California Water Recycling Criteria
include a chlorine disinfection process that provides a residual chlorine
concentration times modal contact time (CT) value of at least 450 mg-min/L
at all times with a modal contact time of at least 90 minutes where
disinfected tertiary treated wastewater is required. This is based on the
Pomona Virus Study.
- The paper summarizes the USEPA Guidelines for Water Reuse. Groundwater
recharge of potable aquifers by injection and augmentation of surface water
supplies requires secondary, filtration, disinfection, and advanced water
treatment. Water quality goals include pH 6.5-8.5, turbidity less than 2 NTU,
no detectable fecal coliforms, less than 1 mg/L chlorine residual, and
compliance with all drinking water standards.
- USEPA Guidelines for Water Reuse has different requirements for
groundwater recharge of potable aquifers by spreading. It requires
site-specific treatment with secondary treatment and disinfection at a
minimum. The reclaimed water quality is also site specific, but must be able
to meet drinking water standards after percolation through the vadose zone.
- The paper also presents the World Health Organization guidelines for
potable municipal reuse. They include no fecal coliform or virus particles
plus no toxic effects on man. Essential treatment processes include primary,
secondary, nitrification, and disinfection. In addition, one or more of the
following processes will be essential: filtration or equivalent,
denitrification, chemical clarification, carbon adsorption, and ion exchange
or other means to remove ions.
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Too Much or Too Little: Public Health
Perspectives of Water Reclamation Reliability, Riley, Craig L., AWWA
Water Sources Conference Proceedings, 2002.
People are Watching: Public Participation in a
"Win-Win" Reuse Project, Janga, Ram G., and Richardson,
Andrew W., AWWA Water Sources Conference Proceedings.
- 10-mgd plant called Northwest Water Resource Center began
operation in Las Vegas in July 2001. The plant treats municipal wastewater
for irrigation use in the summer, and for potable water storage in the
aquifer during the winter. Recharge/recovery wells inject/withdraw water
from the aquifer based on demand and time of year.
- Community Relations and Public Involvement Program was developed for the
project. They took on a number of tasks including development of
audio-visual programs, brochures, fact sheets, project newsletters, and news
releases. They also coordinated with the media, organized public information
meetings, responded to public inquiries via phone and mail, and organized
field trips to similar projects.
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Indirect Potable Reuse: Committee Report,
McEwen,
Brock, and Tom Richardson, AWWA/WEF Water Reuse Conference Proceedings,
1996.
- Water supply development policy has shifted from large, trans-basin water
conveyance projects to conservation and reuse.
- More stringent wastewater disposal standards are becoming common. It may
be more advantageous to reclaim treated wastewater for potable use than
discharge highly treated water to sensitive aquatic systems.
- Current planned indirect potable reuse in Los Angeles County, CA, Orange
County, CA, Fairfax County, VA, and El Paso, TX.
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"Potable use of Reclaimed Water," Crook,
James, Jacqueline A. MacDonald, and R. Rhodes Trussell, Journal AWWA,
August 1999.
- Treatment technology is advanced enough that very high quality water can
be produced from wastewater effluent.
- More than two dozen large water utilities use water that receives
significant contributions from wastewater discharges.
- Reuse requirements should exceed drinking water and wastewater discharge
requirements.
- Public health should be protected by providing increasingly effective and
reliable treatment and through more comprehensive monitoring in scope and
frequency. Projects with less conservative treatment should incorporate more
comprehensive monitoring and vice versa.
- More rigorous pretreatment programs should be considered when indirect
potable reuse is planned.
- Multiple barriers are essential.
- Aquifer storage appears to be a better buffer for reclaimed water than
surface water bodies.
- The treatment of the water in the aquifer may be considered an additional
barrier to certain contaminants.
- Alternative means of disposing of reclaimed water should be maintained in
the event that water quality standards are not met.
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Using Reclaimed Water to Augment Potable Water Resources,
Joint Task Force of the Water Environment Federation and the American Water
Works Association, 1998.
- From the WEF water reuse policy statement: "Treated wastewaters
already comprise an unplanned, but significant component of our nation’s
freshwater supplies through discharge to streams, lakes, and groundwater
basins used to supply domestic, industrial, and agricultural water
demands."
- From the AWWA water reuse policy statement: "…whereby reclaimed
water is a supplement to existing raw water sources receiving appropriate
subsequent treatment."
- System reliability takes on far greater importance in a potable water
reuse project.
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Issues in Potable Reuse, National Research Council
Commission on Geosciences, Environment, and Resources Water Science and
Technology Board, 1998.
- Concerns about planned indirect potable reuse also apply to conventional
water supplies under the influence of wastewater discharges.
- Significant health risks have not been identified in communities using
reclaimed water. This is confirmed by analytical and toxicological testing
as well as epidemiological studies.
- Indirect potable reuse system requirements should exceed the requirements
for conventional water treatment facilities.
- Every reuse project should have a rigorous and regularly updated
monitoring system to ensure the safety of the product water.
- All major chemical inputs from household, industrial, and agricultural
sources should be considered.
- Stringent industrial pretreatment and pollutant source control programs
should be used.
- Potable reuse systems should continue to employ strong chemical
disinfection processes to inactivate microbial contaminants even if they
also use physical treatment systems.
- Barriers for microbiological contaminants should be more robust than
convention water treatment.
- Operators of reuse facilities need training beyond that typically
provided.
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Singapore Water Reclamation Study – Expert Panel Review and
Findings, June 2002.
- "NEWater" project in Singapore began in 1998. Project takes
effluent from the Bedok Water Reclamation Plant and treats it with
microfiltration, reverse osmosis, and UV. The plan is to augment raw water
reservoirs with reclaimed water.
- 2.6 mgd demonstration plant in operation since May 2000. The plant
demonstrated that reclaimed water can be consistently and reliably produced
on a large scale.
- Sampling and Monitoring Programme included extensive analysis of many
parameters in the following categories: physical, disinfection by-products,
inorganic, disinfection by-products, pesticides/herbicides, radionuclides,
wastewater signature components, synthetic and natural hormones, and
microbes.
- The report concludes that the physical, chemical, and microbiological data
for the reclaimed water are within the requirements of USEPA and the World
Health Organization.
- A health effects study on mice and fish is being conducted.
- To date, the Health Effects Testing Programme show that exposure to or
consumption of reclaimed water does not have carcinogenic or estrogenic
effects on fish or mice.
- Expert Panel findings include: reclaimed water is considered safe for
potable use; Singapore should adopt indirect potable reuse because trace
minerals are provided, by blending with natural reservoir, that are removed
from reclaimed water by treatment, storage provides additional safety, and
for public acceptance; Singapore should consider the use reclaimed water for
indirect potable reuse as it is a safe supplement to the water supply; and a
vigilant and continuous monitoring programme be implemented if indirect
potable reuse is used.
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