9523870 Miller Bioavailability and Biodegradation of Organic Contaminants in Heterogeneous Subsurface Environments. One of the most promising and cost-effective environmental cleanup technologies for contaminated soil and groundwater is in situ bioremediation. In situ bioremediation is the use of microorganisms to restore a contaminated environment without having to excavate or otherwise disturb the contaminated site. Many natural environments contain microbial communities capable of degrading (destroying) pollutants. There are two serious problems facing successful implementation of in situ bioremediation. These are the physical and chemical heterogeneities found in natural environments, and the reduced availability of contaminants that results from the sorption (sticking) of contaminants to solid surfaces (clay or sand particles). The goal of this project is to use an integrated biological and physical/chemical approach to investigate the factors controlling bioremediation in natural (heterogeneous) subsurface environments. This proposal outlines a unique approach to understanding the effect of heterogeneity on contaminant availability, and how availability constraints can be overcome to enhance the magnitude and rate of bioremediation. This approach combines state-of-the-art intermediate-scale flow and transport experiments with an advanced technique for the determination of both the number and activity of contaminant-degrading microorganisms (fiber optic detection of luminescing microorganisms). This approach will allow the simultaneous detection of contaminant transport and microbial activity, which will allow for the investigation of the relationship between spatial heterogeneity and availability of contaminants for microbially-mediated destruction. In addition, the approach will be used to evaluate the physical and biological parameters that control the transport of microorganisms in a heterogeneous environment, and to relate microbial mechanisms for enhanced transport to their potential to enhance the degradation of inaccessible organic contaminants. The approach will also be used to evaluate strategies to enhance in situ bioremediation, for example, the application of surfactants (detergents) that may increase the availability of sorbed contaminants. The results of the research will improve our understanding of these issues and will provide significant advancement in prediction of contaminant transport and fate, for evaluating groundwater contamination potential, and for the manipulation of subsurface systems to enhance the effectiveness of bioremediation technologies.
