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, says a new report from the National Research Council. It adds that the reuse of treated wastewater, also known as reclaimed water, to augment drinking water supplies has significant potential for helping meet future needs. 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 may be significantly lower than, the risks of existing water supplies.
“Wastewater reuse is poised to become a legitimate part of the nation’s water
supply portfolio given recent improvements to treatment processes,” says R.
Rhodes Trussell, chair of the committee that wrote the report and president of
Trussell Technologies, a Pasadena,
Calif., firm. “Although reuse is
not a panacea, wastewater discharged to the environment is of such quantity
that it could measurably complement water from other sources and management
The report examines a wide range of reuse applications, including potable
water, non-potable urban and industrial uses, irrigation, ground water
recharge, and ecological enhancement. The committee found that many communities
already have implemented water reuse projects – such as irrigating golf courses
and parks or providing industrial cooling water in locations near wastewater
reclamation plants – that are well-established and generally accepted. Potable
water reuse projects account for only a small fraction of the volume of water
currently being reused. However, many drinking water treatment plants draw
water from a source that contains wastewater discharged by a community located
upstream; this practice is not officially acknowledged as potable reuse.
The report outlines wastewater treatment technologies for mitigating chemical
and microbial contaminants, including both engineered and natural treatment
systems. These processes can be used to tailor wastewater reclamation plants to
meet the quality requirements of intended reuse applications. The
concentrations of chemicals and microbial contaminants in reuse projects
designed to augment drinking water supplies can be comparable to or lower than
those commonly present in many drinking water supplies. The committee
emphasized the need for process reliability and careful monitoring to ensure
that all reclaimed water meets the appropriate quality objectives for its
Costs of water reuse for potable and non-potable applications vary widely
because they depend on site-specific factors, the committee says. Water reuse
projects tend to be more expensive than most water conservation options and
less expensive than seawater desalination and other new supply alternatives.
Although the costs of reclaimed water often are higher than current water
sources, the report urges water authorities to consider other costs and
benefits in addition to monetary expenditures when assessing reuse projects.
For example, water reuse systems used in conjunction with a water conservation
program could be effective in reducing seasonal peak demands on the drinking
water system. Depending on the specific designs and pumping requirements, reuse
projects also could have a larger or smaller carbon footprint than existing
supply alternatives, or reduce water flows to downstream users and ecosystems.
Water reuse regulations differ by state, and are not based on risk-assessment
methods, the report says. Adjustments to the federal regulatory framework could
help ensure a high level of public health protection, provide a consistent
minimum level of protection across the nation, and increase public confidence
in potable and non-potable water reuse. The report notes that existing
legislative tools could be applied to improve the quality of water for reuse,
including updating the National Pretreatment Program’s list of priority
pollutants to include a wider inventory of known toxic substances. Also, it
lists 14 areas of research to help guide the country on how to apply water
reuse appropriately. Such research would require improved coordination among
federal and nongovernmental organizations.
Municipal Wastewater Reuse
March 1, 2012