Microbes take bite out of nitrate.

Vegetable oil is great for cooking french fries, but even better for energizing microbes. Scientists at the Department of Energy's Pacific Northwest Laboratory (PNL) believe it may provide an inexpensive and effective way of stimulating microbes to eat toxic contaminants in water.

PNL, in conjunction with the Department of Agriculture, successfully has demonstrated in the laboratory that microbes energized by vegetable oil can filter nitrate from simulated underground aquifers. Nitrate is considered one of the most pervasive groundwater contaminants in the U.S.

The process works by injecting the oil into the ground around the base of a well. As it enters the subsurface, the oil becomes trapped in pockets between the various layers of sediment. The nitrate filtration takes place as the contaminated water flows past a zone of naturally occurring microbes that use the carbon in the oil as an energy source. The microbes metabolize the nitrate and transform it into nitrogen gas, which is absorbed into the water. The water then can be pumped from the earth free of the nitrate. The microbes remain underground until they die.

Nitrate in groundwater often is associated with agricultural practices such as the leaching of excess fertilizer, use of...