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item Hunter, William

Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2002
Publication Date: 10/1/2002
Citation: Hunter, W.J. 2002. Bioremediation of chlorate or perchlorate contaminated water using permeable barriers containing vegetable oil. Current Microbiology. 45:287-292.

Interpretive Summary: Chlorate and perchlorate are used in a number of industrial, military, and agricultural applications. They are both highly soluble in water and persistent in deep groundwater. The presence of chlorate in drinking water is a concern because it may cause thyroid lesions and anemia, while the presence of perchlorate in drinking water is a concern because it interferes with the proper functioning of the thyroid gland. Ion exchange reverse osmosis, and nanofiltration can remove both anions from water but these processes do not destroy the anion. Biological treatment removes these anions by converting them to chloride and oxygen. These studies demonstrate the principles whereby a simple in situ permeable barrier composed of sand, gravel and small amounts of an insoluble carbon substrate can be used to remove chlorate and perchlorate from flowing ground water. In these studies the soil columns contained innocuous vegetable oils though hother carbon substrates or electron donors might also be used in situ to remove perchlorate from contaminated groundwater.

Technical Abstract: In this study I examined the use of a permeable barrier formed by injecting a vegetable oil emulsion onto a soil column to remove chlorate and perchlorate from flowing groundwater. The working hypothesis was that oil trapped in the soil matrix can serve as a substrate for soil microorganisms enabling them to reduce chlorate or perchlorate in groundwater to chloride as water flows through the oil rich zone. The hypothesis has merit, ~ 96% of the chlorate (0.2 mM or 16.7 mg L-1 chlorate) and ~99% of the perchlorate (0.2 mM or 20 mg L-1 perchlorate) present in flowing water was removed as contaminated water was pumped through soil columns containing a barrier formed by the injection of an oil emulsion onto the columns. The principal product formed was chloride. When nitrate at 1.4 mM (20 mg L-1 nitrate-N) was added to the water both nitrate and chlorate were removed from the water by the barrier. Vegetable oil can serve as a substrate to treat high concentrations of chlorate or perchlorate, 24 mM (2000 mg L-1) chlorate and 6 mM (597 mg L-1) perchlorate were completely reduced to chloride during microcosm incubations. Microorganisms capable of the reduction of perchlorate are plentiful in the environment.