Period Covered by the Report: September 1, 2002 to November 30, 2002
Date of Report: January 1, 2003
EPA Grant Number: R827015-01-0
Title: Anaerobic Intrinsic Bioremediation of MTBE
Investigators: Joseph Suflita
Institution: University of Oklahoma
Research Category: Intrinsic bioremediation/natural attenuation
Project Period: March 1, 200 to February 28, 2003
MTBE biodegradation under anaerobic and aerobic conditions has been evaluated in sediment slurry incubations prepared with material collected from ten impacted sites. The initial assay of the incubations was conducted by Surbec-Art. The biodegradation of MTBE in the presence of oxygen has been noted in seven of the ten samples evaluated. Tertiary butyl alcohol (TBA) biodegradation activity was assessed concurrently in parallel incubations prepared with samples from four of the seven sites that tested positive for aerobic MTBE biodegradation. TBA biodegradation was noted in all four, thereby indicating the capacity for complete MTBE biodegradation under aerobic conditions.
The anaerobic biodegradation of MTBE has been detected only in one of ten samples. This activity was dependent on the presence of hydrogen added to the headspace of the incubations. This was not an experimental variable in the original proposal and something that Surbec-Art incorporated into their screening efforts. At this time, it is not known whether the MTBE has been mineralized or converted to TBA via methyl group removal. Radiotracer mass balances and 14C-TBA analyses will be conducted in an effort to make this determination. Therefore, at this time we cannot conclude that there is a significant anaerobic fate process for MTBE beyond the simple methyl group removal.
The analysis of sulfate, soluble ferrous iron, and methane in the anaerobic incubations relative to autoclaved controls revealed that sulfate reduction and methanogenesis were the predominant terminal electron accepting conditions in the anaerobic incubations. Therefore, the experiments have not fully evaluated MTBE biodegradation in the presence of other alternate electron acceptors including iron, manganese, or nitrate. Analyses for 14C- CO2 and 14C-CH4 will be continued in an effort to obtain a more exhaustive analysis of anaerobic MTBE biodegradation activity.
A comprehensive review of the literature covering the aerobic and anaerobic biodegradation of MTBE in both the laboratory and the field has been prepared and submitted for publication as part of this project.