Student Presenter

Na Wei, University of Illinois - Urbana Champaign, Dept of Civil and Environmental Engineering, NCEL 205 N. Mathews, Urbana, IL, 61801, Tel: 217-333-8121, Email: nawei2@uiuc.edu
Kevin T. Finneran, Assistant Professor, University of Illinois - Urbana Champaign, Dept of Civil and Environmental Engineering, NCEL 205 N. Mathews, Urbana, IL, 61801, Tel: 217-333-1514, Fax: 217-333-6967, Email: finneran@uiuc.edu

The fuel oxygenate methyl tert-butyl ether (MTBE) is a prevalent groundwater contaminant, and its key degradation intermediate tert-butyl alcohol (TBA) often accumulates in subsurface environments. Although studies have reported potential for aerobic microbial degradation of MTBE and TBA, in situ conditions within proximity of source areas are typically anaerobic, and moreover, oxygen introduced artificially can be consumed quickly by chemical oxidation of Fe (II) and sulfides. Source area bioremediation strategies must encompass anaerobic conditions from nitrate reduction, Fe (III) reduction, sulfate reduction to methanogenesis, as these processes shift from higher to lower redox processes. This research has investigated the mechanisms and kinetics of MTBE and TBA biodegradation under shifting anaerobic conditions.

Microcosm experiments were initiated using petroleum contaminated sediment, river sediment, and anaerobic digester sludge. Radiolabeled (14C) and non-radiolabeled MTBE and TBA were amended to different incubations to quantify MTBE/TBA biodegradation. Different electron acceptor amendments and electron shuttling amendments were added to identify the MTBE degradation (and potential TBA accumulation) dynamics as conditions shift from one dominant process to another. To date the microcosms are in acclimation stage with up to 5% recovery of [U -14C ]-MTBE or [U -14C ]-TBA as 14CO2.  Data suggest that fumarate and electron shuttles increase the extent of MTBE biodegradation; however, TBA degradation is slower than corresponding MTBE incubations.  Sulfate increases the rate of MTBE and TBA biodegradation, but is very dependent on the starting material. Liquid enrichments with petroleum contaminated sediment degraded MTBE and TBA in less than one month under nitrate reducing, Fe (III) reducing, sulfate reducing and fumerate reducing conditions. These liquid enrichments may provide a model, anaerobic microbial culture for investigating basic cellular processes related to anaerobic MTBE and TBA biodegradation – currently, no such anaerobic culture has been reported.  These data suggest that anaerobic MTBE/TBA biodegradation is influenced by shifting electron accepting processes, and the effects of these geochemical factors on MTBE/TBA degradation continue to be investigated.  

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