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AN ENRICHMENT CULTURE THAT DEGRADES MTBE UNDER ANAEROBIC CONDITIONS
Citation:
Kaiser*, P. M., J T. Wilson*, AND C J. Adair*. AN ENRICHMENT CULTURE THAT DEGRADES MTBE UNDER ANAEROBIC CONDITIONS. Presented at Battelle Conference, Monterey, CA, May 24 - 27, 2004.
Impact/Purpose:
To inform the public.
Description:
Biodegradation of MTBE in ground water may be a significant factor helping to reduce MTBE contamination from gasoline spills. Previously, decreases in MTBE concentrations in wells at release sites were thought to be due exclusively to dispersion and dilution. Researchers have isolated aerobic bacteria that degrade MTBE, but anaerobic bacteria capable of transforming MTBE have not been isolated, but their existence has been inferred from field data, including enrichment of stable carbon isotope ratios in the residual MTBE as concentrations of MTBE decrease.
Laboratory microcosms, created from aquifer sediments from a gasoline spill at Parsippany, New Jersey were dosed with MTBE and it was consumed within six months. Enrichment microcosms were created by inoculating them with a composite soil made by mixing all of the soil from the successful treatments. The microcosms were made in 25 mL serum bottles contained 2.5 g of soil and filled with MTBE dosed media. Four different media: methanogenic, acetogenic, sulfate reducing, and nitrate reducing with 100 mg/L MTBE were used to enrich for the bacterial type involved in the degradation. Three enrichment microcosms containing the media favoring methanogenic activity began to show increased levels of tertiary-butyl alcohol (TBA) after a three to six month lag time. One microcosm degraded 98% of the initial MTBE within five months after the lag time ended. 10 mL of MTBE depleted media was removed and an equivalent amount of dosed media was added which was totally degraded within two months. Isotopic monitoring showed an enrichment factor of -12.8 which agrees with previously reported values. None of the enrichment microcosms containing the other media showed any MTBE consumption through 14 months of incubation. On-going work includes the monitoring of established secondary enrichment cultures in the absence of soil.