OREGON STATE UNIVERSITY

Pollution technology uses gas-loving bacteria

02/25/1998

CORVALLIS - There's no accounting for tastes, but there may be ways to take advantage of them: It appears that some types of bacteria love to feed on compounds such as butane gas and, in the process, are quite effective at degrading other toxic wastes that may be in the vicinity.

Environmental researchers at Oregon State University have discovered new ways to use these "co-metabolizing" bacteria in technologies that may help clean up seriously contaminated soils or groundwater at far lower costs than some other "pump and treat" alternatives.

There's potential to save millions of dollars in cleanup costs while addressing major environmental problems, the scientists say.

Findings of the continuing research have been recently published in professional journals in the fields of microbiology and environmental biotechnology.

"In the laboratory, the existence of such bacteria and some of their capabilities has been observed for some time," said Lewis Semprini, an associate professor of environmental engineering at OSU. "But we've discovered one of particular value and found some new uses. This is a multi-billion dollar problem and we believe some of this technology may play an important role."

In the past, a variety of commercial, industrial or military activities have contaminated soils with chlorinated hydrocarbons such as trichloroethylene or chloroform. Many industries are facing mandates to clean up these sites, Semprini said, often at extraordinary expense and difficulty.

With funding support from the EPA and the National Institutes of Health, OSU scientists have conducted both basic research on microbial physiology and applied studies that may help create an engineered technology that can address this problem.

One of the most promising approaches is a bacteria that "feeds" on butane or propane gas.

"This type of bacteria literally uses butane as a food, as its source of carbon and energy," said Dan Arp, an OSU professor of botany and plant pathology and collaborator on these studies. "During their digestive process, the bacteria produce an enzyme that also will react with toxic pollutants. If everything works, all that's left over is the chemical equivalent of table salt and carbon dioxide."

Continuing studies are examining the rates at which this interaction can degrade pollutants, the limiting factors and what enzymes are involved, the researchers say.

"To be completely successful this process requires both the metabolism of the butane and the toxin," Semprini said. "And we have to engineer it right so it works in the real world."

Field studies examining just that are being conducted at McClellan Air Force Base in Sacramento, Calif., in a project funded by the Department of Defense that will attempt to treat underground "plumes" of pollutants. A challenge is to get the needed oxygen, butane and bacteria all present in the appropriate combinations. One approach may be to use water under pressure to inject one or more of these elements into polluted groundwater aquifers.

"Bioremediation of these chlorinated solvents is clearly a promising technology," Semprini said.

"Another value may be in using this system to contain the spread of a pollution problem, where you let the pollutant naturally flow with the groundwater through a passive biological barrier you create, and then degrade it before it spreads any further," he said.