Land Disposal and Spill Site Environments

Abstract

Land is a receptor of many chemicals through both intentional and unintentional depositions. Mitigation methods for control of the chemicals resulting from unintentional depositions such as unsuccessful landfills, spills, and leaks include excavation and disposal, entombment in place, and in some situations, in situ biodegradation. If genetically engineered bacteria could expand the number of situations where in situ degradation is applicable, then more economically efficient control methods resulting in the destruction of chemicals would be available.

This paper outlines the various processes affecting the fate of organic chemicals in the soil environment, summarizes the environmental conditions encountered by organisms, and reviews two case histories of biodégradation of chemicals within the soil environment.

Environmental conditions encountered by organisms are distinctly different in the two major soil zones: the unsaturated zone and the saturated zone. Chemicals may be present within the soil environment including the vapor phase, the adsorbed phase, and the soluble phase. These differences affect the fates of each chemical and result in greatly different rates of biodegradation of chemicals by naturally occurring microorganisms. Case histories discussed are that of a spray irrigation field treating wastewater from a creosote wood treating process, and that of an in situ biodegradation program for clean up of surface soils contaminated with pentachloro-phenol. Recommendations for bacterial characteristics that could be engineered to greatly expand the applicability of in situ biodegradation are made.