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Spring 2012 Vol. 12 Number 1

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Southside Water Treatment Plant in Albuquerque, N.M., ©Jonathan A. Meyers/Photo ResearchersWastewater’s Potential

Tapping Into Reclaimed Water for Multiple Uses

The thought of drinking water that once flowed through our toilets may make many people cringe. But with water shortages striking different regions of the country, alternatives such as reclaimed water are starting to be considered a viable option. In fact, a number of locations across the country already use reclaimed wastewater for potable and non-potable purposes.

A new report from the National Research Council says that with recent advances in technology, treating wastewater and reusing it for drinking, irrigation, industry, and other applications could significantly increase the amount of water resources available to the nation, particularly in coastal areas that face shortages in clean water supplies. This is a significant recommendation given that a 1998 Research Council report found that reclaimed wastewater represented “an option of last resort” to supplement drinking water sources and only after a thorough health and safety evaluation.

New analyses also suggest that the possible exposure to chemical contaminants and disease-causing microbes from wastewater reuse do not exceed, and in some case may be significantly lower than, the risks of existing water supplies, the report says.

"Wastewater reuse is poised to become a legitimate part of the nation’s water supply portfolio," said R. Rhodes Trussell, chair of the committee that wrote the report and president of Trussell Technologies. “Although reuse is not a panacea, the large quantity of wastewater discharged to the environment could eventually complement water from other sources and management strategies.”

While the notion of drinking reclaimed water may require people to overcome a certain “ick” factor, some may not realize that they are drinking it already. De facto reuse, also known as “unplanned” potable reuse, occurs when drinking water supplies contain a significant fraction of wastewater effluent, typically from upstream discharges, even though this supply of water is not formally recognized or permitted as a water reuse project. De facto reuse is thought to occur widely in the United States, although the last assessment of its extent occurred more than 30 years ago. The report recommends another analysis be carried out to quantify the current degree of de facto reuse.

Nevertheless, the committee found that many communities have already implemented potable and non-potable water reuse projects that are well-established and generally accepted. Examples of non-potable applications include irrigating golf courses and parks or providing industrial cooling water in locations near wastewater reclamation plants.

The report outlines engineered and natural treatment processes that would limit chemical and microbial contaminants in the water and meet the quality requirements of intended reuse applications. The committee emphasized the need for process reliability and careful monitoring to ensure that all reclaimed water meets the appropriate quality objectives for its use.

Although technology and processes are available to start considering the use of wastewater to augment future water supplies, the cost may be a key determinant for municipalities considering reclaimed as an option. Costs for potable and non-potable applications vary widely because they depend on site-specific factors.

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 could also 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 generally not based on risk-assessment methods. 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 says.   -- Jennifer Walsh & Solmaz Spence

Water Reuse: Potential for Expanding the Nation’s Water Supply Through Reuse of Municipal Wastewater. Committee on the Assessment of Water Reuse as an Approach for Meeting Future Water Supply Needs, Water Science and Technology Board, Division on Earth and Life Studies (2012, approx. 200 pp.; ISBN 0-309-25749-2; available from the National Academies Press, tel. 1-800-624-6242; $45.00 plus $5.00 shipping for single copies).

The committee was chaired by R. Rhodes Trussell, president, Trussell Technologies, Pasadena, Calif. The study was sponsored by the U.S. Environmental Protection Agency.

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Copyright 2012 by the National Academy of Sciences