PECASE: Integrated Modeling and Experimental Evaluations of Competition Between PCE-Dehalogenating Populations: Implications for In Situ Bioremediation

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Proposal Title: PECASE: Integrated Modeling and Experimental Evaluations of Competition Between PCE-Dehalogenating Populations: Implications for In Situ BioremediationInstitution: University of Maryland College ParkThe chlorinated solvents tetrachloroethene (PCE) and trichloroethene (TCE) are among the most common contaminants of groundwater. The toxicity and physical properties of these compounds, along with the frequency with which they are detected, mean that cleanup of groundwater systems contaminated with PCE and TCE is both critical to protecting human health and technically challenging. Biological transformation of PCE is limited to anaerobic reductive dehalogenation. From a remediation standpoint, only complete dechlorination of PCE to ethene is an acceptable outcome, because lightly chlorinated ethenes also pose a health hazard. Unfortunately, the potential for complete detoxification of highly chlorinated ethenes is frequently not realized in situ, resulting in the accumulation of lightly chlorinated ethenes. An improved understanding of the factors that influence the extent of PCE transformation that occurs in impacted environments is needed to better predict contaminant fate and transport, protect human health, and improve the effectiveness of bioremediation strategies. The proposed research addresses a specific type of microbial interaction, competition between dehalogenating populations for chlorinated ethenes and electron donors. Competition between dehalogenating populations may have a major impact on the fate of chlorinated ethenes in situ because these organisms differ with respect to transformation rates, and even more importantly, the extent of dechlorination.The goals of the proposed research are:(1) to determine how competition among dehalogenating populations is influenced by the intrinsic biokinetics of the dehalogenating populations, the nature and concentrations of the available electron donors, and chlorinated ethene concentrations; and (2) to develop tools for predicting the outcome of competition between dehalogenating populations, the impact on chlorinated ethene fate, and the success of bioaugmentation strategies. These goals will be accomplished using an integrated approach involving modeling predictions and verification in a series of increasingly complex experimental systems, including defined co-culture competition experiments and field surveys involving microbiological and chemical characterization of groundwater at PCE-impacted sites. Quantification of key PCE-dehalogenating populations in groundwater systems will be achieved through 16S rRNA-based methods. This project was originally funded as a CAREER award, and was converted to a Presidential Early Career Award for Engineers and Scientists (PECASE) award in May 2004.