Experimental Assessment of Bioenhanced Dissolution and Microbial Distribution During PCE-NAPL Source Zone Bioremediation
Abstract
Specialized anaerobic bacteria are capable of detoxifying tetrachloroethene (PCE) and trichloroethene (TCE) as well as enhancing contaminant dissolution from dense nonaqueous phase liquid (DNAPL) source zones. Thus, the microbial reductive dechlorination process has emerged as a promising remedial technology for PCE- and TCE-DNAPL source zones. However, the effects of microbial activity and distribution within DNAPL source zones on dissolution enhancement remain poorly understood. Experiments to evaluate the activity and distribution of dechlorinating populations in the immediate vicinity of a PCE-NAPL source zone were performed in a one-dimensional soil column containing a 10 cm NAPL (0.25 mol/mol PCE in hexadecane) source zone and a 50 cm down-gradient plume region. In one column experiment, Sulfurospirillum multivorans, a PCE-to-cis-DCE dechlorinating isolate, transformed PCE to cis-DCE with an approximate 4-fold cumulative dissolution enhancement. Quantitative real-time PCR (qPCR) correlated activity and distribution of S. multivorans with enhanced PCE dissolution. Similar NAPL dissolution enhancement was observed in another column augmented with a PCE-to-ethene dechlorinating consortium containing Dehalococcoides, Dehalobacter, and Geobacter populations, with PCE dechlorinated primarily to cis-DCE and vinyl chloride. Geobacter and Dehalococcoides populations were detected within the source zone, and increases in the dechlorinator population sizes coincided spatially with increased formation of dechlorination products. Experimental results indicate that mass transfer enhancement by microbial reductive dechlorination within NAPL source zones is possible, and that the distribution of relevant microbial populations directly affects dissolution enhancement. Ongoing work focuses on evaluating the distribution of specific Dehalococcoides strains in the vicinity of PCE-NAPL.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.H33I..06A
- Keywords:
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- 0418 Bioremediation;
- 0471 Oxidation/reduction reactions (4851);
- 1831 Groundwater quality