[Pharmwaste] Researchers study micropollutants in wastewater -
article about using bacteria to treat them
Laurie.Tenace at dep.state.fl.us
Thu Aug 25 11:25:03 EDT 2011
PORT ORCHARD - University of Washington researchers are learning to form specialized armies of bacteria that can seek and destroy micropollutants lurking in sewage effluent.
Heidi Gough of the UW's Department of Civil and Environmental Engineering described the process Wednesday in Port Orchard, where experts gathered for a daylong conference about the future of reclaimed wastewater.
Micropollutants - which include medicines, pesticides and personal-care products - wash down the drain and get into sewers in extremely low concentrations. Some micropollutants, such as human estrogen from birth-control pills, have been implicated in reproductive problems among freshwater fish and amphibians in other parts of the country.
As sewage-treatment plants in Kitsap County prepare to use highly treated effluent for watering parks and ball fields, questions are surfacing about the effects of every possible contaminant - even when no environmental risks are expected.
Most micropollutants are destroyed during the sewage-treatment process, along with bacteria and viruses. Some bind to solids, which are separated and eventually trucked away. But some compounds survive in concentrations of parts per billion or parts per trillion, and researchers across the country are trying to measure the risks.
"So far, it is in the aquatic environment that we have seen the impacts," Gough said. "It is not an environmental crisis yet, but all the water eventually gets recycled."
It is happening now, she said, in major river systems. One community discharges treated wastewater upstream of another community, which withdraws the same water for drinking and other uses. Then that community discharges the water upstream of the next community. Theoretically, even micropollutants can build up over time.
Fortunately, she said, something else is happening to the water, because concentrations don't increase very much.
"I want to know what is happening," she said, "because, as an engineer, I want to do it better."
It has taken four years of study, but Gough and her associates have isolated groups of bacteria, each one specialized to break down one of several micropollutants chosen for her study. The bacteria were in the effluent all along, but the researchers found ways to grow the strains of bacteria, most of which belonged to a group called Sphingomonas.
Once the technique is perfected, a treatment plant would be able to respond to any micropollutant that becomes a concern, she said. Treatment plant operators could grow the specialized bacteria in a tank. The Sphingomonas, for example, seem to thrive on whey, a byproduct of cheese production, but they don't like sugars.
Studies show that a little of the bacteria added at the right time in the treatment process can eliminate bisphenol A, a plastic additive, in about 20 minutes. BPA, as it is called, has been linked to cancer in mice with possible implications for humans.
Mariko Lust, a UW graduate student involved in the project, has examined the fate of various estrogen compounds in sewage effluent. She said many types of estrogen are largely removed during normal treatment in a membrane bioreactor system, such as West Sound Utility District's treatment plant in Port Orchard. But some, including synthetic estrogen, pass through in reduced concentrations.
Lust said she was excited about the prospect of looking for bacteria that can remove estrogen from sewage.
Meanwhile, others at Wednesday's conference talked about the need to expand the use of reclaimed water, as communities are doing in California and Texas, as well as other places in the world. The prospect of drinking sewage effluent, once considered unlikely, is coming to pass in drought-stricken areas.
While water covers 68 percent of the Earth, only 3 percent is freshwater and 2 percent of that is ice, said Paul Schuler of General Electric World Vision. That leaves 1 percent for humans to share with fish and wildlife, and many areas of the world are running out of water.
"The amount of water that is safe to use is actually declining," said Schuler, whose company manufactures advanced sewage treatment plants."We need to take care of our precious water resources."
The conference, at Kitsap County Administration Building, was organized by West Sound Utility District with support from the city of Port Orchard, Kitsap County Public Works, Kitsap Public Utility District and Silverdale Water District.
Waste Reduction Section
Florida Department of Environmental Protection
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Laurie.Tenace at dep.state.fl.us
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