Making wastewater potable: feasible, but getting over the yuck factor is tough
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Used to be you could flush it and forget about it, but not anymore.
Advances in wastewater treatment technology and design make it possible to convert sewage wastewater to potable water and a variety of other more palatable uses, according to a report by the National Research Council, an arm of the National Academies.
The study, released earlier this month, said the ability to reuse "reclaimed water" for drinking supplies, irrigation, recreational and industrial purposes, and well as to replenish depleted aquifers and surface water, could play a significant role in meeting future water supply needs, especially in coastal areas facing fresh water shortages.
In addition, the study's analysis of advanced treatment processes, including reverse osmosis filtration, carbon absorption and oxidation, found that health risks from exposure to chemical contaminants and disease-causing microbes in the reclaimed water do not exceed and in some cases may be lower than in 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," said R. Rhodes Trussell, president of Trussell Technologies in California and chair of the committee that wrote the report. "Although reuse is not a panacea, wastewater discharged to the environment is of such quality that it could measurably complement water from other sources and management strategies."
But making nature's water cycle much more personal by piping reclaimed water directly to the water tap is highly unlikely in southwestern Pennsylvania, where water is abundant and relatively clean, said Stanley States, water quality manager with the Pittsburgh Water and Sewer Authority, which draws water from the Allegheny River for its 400,000 customers.
"Pittsburgh is blessed. We have lots of water and it's good quality," Mr. States said. "There isn't any reclamation done here and it doesn't need to be."
He said reclaimed wastewater is used now for irrigation in California, to water golf courses in Florida and for snow-making by Seven Springs, the ski resort in the Laurel Highlands. Other ski resorts in California, Arizona and around Lake Tahoe on the California-Nevada border also make snow with reclaimed water.
Mr. States said he knows of only one city -- Windhoek, the semi-arid capital of Namibia, in Africa -- where, due to scarcity, reclaimed water is used to directly and significantly supplement the drinking water supply. There it makes up about 25 percent of tap water.
"The problem is the aesthetics," he said. "Technologically we could do it. Psychologically, no one would drink it. Who's going to line up to drink it unless they absolutely must?"
But a number of factors could make use of reclaimed water a must for drinking in the U.S. sooner rather than later despite the high public "yuck" factor, said Jorg Drewes, a professor of civil and environmental engineering at the Colorado School of Mines and a member of the national Research Council who worked on the report. Those include the increased urbanization of the American population and migration to areas of the coastal South and desert Southwest where water is already scarce.
Water reuse projects can have widely varying costs, the report noted, but Mr. Drewes said there are high costs to importing water into a region where it is scarce.
"Adding freshwater resources as population grows is very difficult today in many areas," he said. "If an area runs out of water it can import it or use the drought-proof supply that is its local wastewater. That already has a pipe system to bring that water in. And in the long run, that's likely more viable and reliable than an imported water source."
Wastewater reclamation is also useful in areas that have both limited fresh water resources and discharge limitations, like the State College area in Centre County. There a growing population in five communities around Penn State University and a sewage system that discharges into Spring Creek, a small, high-quality cold-water trout fishery, caused the University Area Joint Authority to begin planning for water reclamation 13 years ago.
The authority built an advanced wastewater treatment facility that uses microfiltration and high pressure reverse osmosis membranes before disinfecting the flow in pressurized ultraviolet units. The reclaimed water is used to supply a commercial laundry, hotel laundry, carwash, golf course and for industrial heating and cooling. This summer the authority will begin pumping the water seven miles to Slab Cabin Run, a feeder tributary high in the watershed of Spring Creek to recharge surface water flows and the underground aquifer.
"The driving factor was the growth in the region but we also had a limited ability to discharge the treated wastewater into the high-quality stream," said Cory Miller, authority executive director. "We're not drinking the [reclaimed] water but we're using it to replace some drinking water uses."
The report, sponsored by the U.S. Environmental Protection Agency, the U.S. Bureau of Reclamation, National Science Foundation, National Water Research Institute and a dozen water supply districts in California, found that water reuse regulations differ widely among states and are not based on health risk assessments.
In Pennsylvania, Mr. Miller said, there are no state regulations specifically for water reclamation discharges. A draft water reuse manual was put together by the state Department of Environmental Protection in 2006 but never finalized.
"It's interesting that we have to get really complicated permits to discharge this really clean water into the stream," Mr. Miller said. "The state and the EPA are treating this as a wastewater discharge so we are required to get a National Pollutant Discharge Elimination System permit."
The report also recommended that federal regulations be updated to include a wider inventory of toxic substances and ensure a higher level of public health protections.
First Published January 22, 2012 12:00 am
