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Abstract

A significant obstacle to the application of microbial reductive dechlorination of PCE and TCE is the undesirable accumulation of cis-DCE and vinyl chloride. In this study, lab-scale aquifer sediment column experiments were conducted to evaluate the feasibility of using ethene to stimulate cometabolic and/or auxiliary aerobic degradation of DCE in aquifer sediments from Edwards Air Force Base (EAFB). A mixture of ethene in air was supplied to gas-permeable membranes installed in a test column to stimulate aerobic degradation of DCE by ethenotrophic populations. Membranes in a parallel column were supplied with air or nitrogen as a negative control. The experimental results indicated that simply supplying ethene and air to the EAFB aquifer sediments alone did not produce conditions favorable for growth of DCE-degrading ethenotrophs. Moreover, amending the aquifer sediments with nutrients and bioaugmenting with enriched and pure (Nocardioides strain JS614) ethenotrophic cultures failed to stimulate growth of DCE-degrading ethenotrophs. This may have been due to the presence of inhibitory substrates or the absence of requisite growth factors. Parallel microcosm studies demonstrated that both the enriched ethenotrophic culture and the Nocardioides strain JS614 culture rapidly cometabolized DCE in mineral salts media, but did not readily acclimate to the EAFB aquifer sediments. The results of the column study and microcosm study together indicated that achieving ethenotrophic degradation of cis-DCE may be more difficult under in situ conditions than under ideal microcosm conditions.

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