ARS Method Shows Promise for Decontaminating Groundwater

Trichloroethylene (TCE), a colorless, toxic liquid widely used as a solvent for dry cleaning and degreasing, has been known to seep into groundwater and make it dangerous for consumption. TCE also has been found in groundwater on some military bases. Now Agricultural Research Service scientists may have found an inexpensive but effective product to clean up the mess: vegetable oil.

Microbiologist Jim Hunter of the ARS Soil-Plant-Nutrient Research Laboratory, Ft. Collins, Colo., has discovered that vegetable oil can be used to clean up groundwater contaminated with TCE. He recommends using soybean oil since it is inexpensive.

Battelle, a nonprofit scientific company, originally suggested that vegetable oil may clean up pollutants in groundwater, and Hunter was able to prove it. Hunter also has shown that vegetable oil can clean up groundwater that is contaminated with nitrogen fertilizer and the herbicide chlorate.

Hunter believes the best way to get the oil into the water is by injecting the oil into the ground as an emulsion using high pressure to create a porous, oil-containing barrier across the contaminated aquifer. The oil, used in low concentrations, stimulates microorganisms naturally present in the aquifer to grow and accumulate in the barrier. The TCE is degraded by these microorganisms as contaminated groundwater flows through the barrier.

Parsons Corporation, an environmental consulting firm in Denver, Colo., is using this ARS method to cleanse TCE from groundwater. Parsons is halfway through its tests on several Air Force and Navy bases to see how effective the vegetable oil is. The company has already completed some pilot tests and is now working on full-scale evaluations.

ARS is the U.S. Department of Agriculture’s primary scientific research agency.