Native bacteria can be used to destroy one of the most tenacious and widespread contaminants that is poisoning the nation's groundwater, Stanford researchers have shown.

The pollutant is trichloroethylene (TCE). In the 1980s, Americans used 150 million tons of TCE annually to dryclean their clothes and to degrease aircraft and automobile engines. Now it is one of the most widespread and difficult to treat groundwater contaminants in the country.

The researchers -- working at Edwards Air Force Base in Southern California -- have completed the first full-scale test to determine if TCE can be removed from groundwater using a method called in situ bioremediation, which uses naturally occurring microorganisms to break down toxic chemicals.

"The test has shown that this method can successfully reduce the levels of TCE in groundwater by 96 to 98 percent," said Perry L. McCarty, the Silas H. Palmer Professor of Civil Engineering who heads the project, report in a at the American Chemical Society meeting in San Francisco this week. Working with him on the project are: Mark Goltz, associate professor at the Air Force Institute of Technology, graduate student Jason Allan, post-doctoral student Mark Dolan and Gary Hopkins, a science and engineering associate.

In addition to performing effectively, the bioremediation process lived up fully to the researchers' predictions, indicating that they understand the basic processes involved well enough to determine how the method will work in other areas contaminated with TCE, McCarty said.

The conventional approach to groundwater decontamination is called pump-and-treat. Groundwater is pumped to the surface, where air is blown through it to strip out volatile contaminants, which are then adsorbed onto activated charcoal filters. This approach wastes water, because the treated water is seldom reinjected into the aquifer. The contaminated charcoal als
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Contact: David F.Salisbury
salisbury@stanford.edu
415-725-1944
Stanford University
18-Apr-1997