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Microbes to sup at Superfund sites.

By pairing two kinds of bacteria and adding a little sugar, environment engineers have drafted a winning team for purifying contaminated groundwater.

Separately, these bacteria had proved too slow or ineffective at breaking down industrial carcinogens such as perchloroethylene (PCE), also known as tetrachloroethylene, and trichloroethylene (TCE). But then William Jewell and his colleagues at Cornell University decided to piggyback the efforts of these microbes. They build a two-stage "bioreactor" that looks a lot like a moonshine still.

In one chamber, they add sugar to bacteria that need no oxygen to survive. Fueled by this sweet stuff, the bacteria readily strip chlorine atoms from the carcinogens, producing vinyl chloride and methane. The reactor then shunts the vinyl chloride (a toxic gas), methane and oxygen to a second compartment, where bacteria consume the methane and degrade the vinyl chloride into water, carbon dioxide and chloride ions. "And we found that the second-stage system could use vinyl chloride [rapidly] like a rocket," says Jewell. This hybrid reactor can reduce the concentration of PCE in water from 10,000 parts per billion to less than 1 part per billion, safe enough for drinking, the researchers will report in an upcoming Journal of Environment Engineering.

This cost-effective treatment system works fast, even in cool temperatures, and could travel in the back of a truck to contaminated areas designated as Superfund sites by the U.S. Environmental Protection Agency, Jewell adds.

This year, Westinghouse Savannah River Co. in Aiken, S.C., will build a pilot bioreactor capable of processing 40,000 gallons of contaminated groundwater a day.
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Title Annotation:Science & Society; purifying contaminated groundwater
Publication:Science News
Date:Mar 14, 1992
Words:262
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