Report: Stormwater and graywater valid water sources, but guidelines for use are needed

WASHINGTON – In the face of drought and major water shortages, the U.S. is increasingly turning to alternative water sources like stormwater and graywater, but guidelines and research on their risk to public health and the environment are needed to support decisions for safe use, says a new report from the National Academies of Sciences, Engineering, and Medicine. Graywater and stormwater could significantly supplement traditional potable water supplies using existing technology to capture and treat the waters, but there is currently limited information on the costs, benefits, risks, and regulation of such projects, the report concludes. Additional research and changes in infrastructure will be necessary to take full advantage of the potential of graywater and stormwater, the report adds.

Graywater is untreated wastewater from bathroom sinks, showers, tubs, washers, and laundry sinks, and stormwater is runoff from rainfall or snowmelt from roofs, parking areas, and land surfaces. These types of water can be collected and treated for nonpotable uses including irrigation, toilet flushing, and laundry and outdoor washing. The committee that conducted the study and wrote the report undertook a comprehensive analysis of the risks, costs, and benefits of various uses of graywater and stormwater, as well as their capture and use at household, neighborhood, and regional scales.

More research and data on stormwater and graywater quality are necessary to assess the risks under various human exposures, particularly on the types and concentrations of pathogens that are likely to occur, the report says. Additional information is also needed on the organic chemicals in stormwater and their consequences for various uses.