Panel urges caution in drinking reclaimed wastewater

A National Research Council panel has urged caution in the use of reclaimed wastewater for drinking water and said the requirements for indirect potable reuse systems should exceed those of conventional drinking water treatment facilities.

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A National Research Council panel has urged caution in the use of reclaimed wastewater for drinking water and said the requirements for indirect potable reuse systems should exceed those of conventional drinking water treatment facilities.

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A small but growing number of communities have begun using highly treated municipal wastewater to augment their raw water supplies.

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“This trend is motivated by need, but made possible by advances in treatment technology,” a NRC committee said in a report, “The Viability of Augmenting Drinking Water Supplies with Reclaimed Water.”

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The report said a distinction should be made between “direct” and “indirect” reuse. It only studied indirect reuse.

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“Direct use of reclaimed wastewater for human consumption, without the added protection provided by storage in the environment, is not currently a viable option for public water supplies.

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“...this report focuses on planned indirect potable reuse, which refers to the intentional augmentation of a communitys raw water supply with treated municipal wastewater. The reclaimed water might be added to a water course, lake, water supply reservoir, or underground aquifer and then withdrawn downstream after mixing with the ambient water and undergoing modification by natural processes...”

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The report noted that many communities now use water sources of varying quality, including sources that receive significant upstream discharges of wastewater.

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“More than two dozen major water utilities use water from rivers that receive wastewater discharges amounting to more than 50 percent of the stream flow during low flow conditions.”

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The NRC report said, “planned, indirect potable reuse is a viable application of reclaimed water — but only when there is a careful, thorough, project-specific assessment that includes contaminant monitoring, health and safety testing, and system reliability evaluation.”

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It said there should be a spectrum of tests for microbiological and organic chemical contaminants.

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And it stressed, “Indirect potable reuse is an option of last resort. It should be adopted only if other measures — including other water sources, nonpotable reuse, and water conservation — have been evaluated and rejected as technically or economically infeasible.”

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It said uncertainties about the potential health risks of drinking reclaimed water are not an adequate reason for rejecting indirect potable reuse, because current information suggests the risks are comparable to, or less than, the risks associated with many conventional supplies.

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But it noted current drinking water standards are intended for water obtained from conventional, relatively uncontaminated sources of fresh water, not for reclaimed water, and therefore cannot be relied on as the sole standard for safety.

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“The requirements for indirect potable reuse systems thus should exceed the requirements that apply to conventional drinking water treatment facilities.

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“The major recommendation of this report is that water agencies considering potable reuse fully evaluate the potential public health impacts from the microbial pathogens and chemical contaminants found, or likely to be found, in treated wastewater through special microbiological, chemical, toxicological, and epidemiological studies, monitoring programs, risk assessments, and system reliability assessments.”

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