Biotechnology for the Treatment of Pesticide Waste

in HortScience
Jeffrey S. KarnsUSDA/ARS/NRI/Soil Microbial Systems Laboratory, 10300 Baltimore Ave., Beltsville, MD 20705-2350

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The use of microbes and/or microbial processes for the bioremediation of soils contaminated with pesticides is an idea that has enjoyed considerable interest over the past several years. Many microbes with specific pathways for the degradation of particular pesticides, or classes of pesticide, have been isolated and characterized. Unfortunately, most sites that are heavily contaminated with pesticides contain a mixture of the many different types of pesticides that have been used over the last 5 decades. This complex mixture of compounds may inhibit microbial degradation or may require multiple treatments to assure that all the chemicals are degraded. Treatment of wastes before they contaminate the environment is one way to avoid the problems associated with mixed wastes. We have isolated a number of microorganisms that detoxify insecticides, such as carbaryl of parathion via the action of hydrolase enzymes. These enzymes can be used to treat waste pesticide solutions before disposal. A system was developed for the disposal of one high-volume organophosphate insecticide waste by treatment with parathion hydrolase, followed by ozonation to yield harmless products that were readily degraded by other soil microorganisms. A second method for disposal of this waste involves altering the environmental conditions in the waste to stimulate the growth of microorganisms naturally present in the material utilizing the pesticide as a carbon source. This accomplishes degradation of the material over a 2-week period. Many, if not all, pesticides are degradable to some degree by microorganisms, and this fact can be exploited to provide cost-effective methods for the safe disposal of pesticide wastes.

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