Complete Reductive Dechlorination of Trichloroethene by a Groundwater Microbial Consortium^a

Abstract

Bioremediation promises to be an important technique in the removal of trichloroethene (TCE) and tetrachloroethene (PCE) from contaminated waste sites and contaminated groundwater systems. However, the use of aerobic degradation to degrade these compounds is not always possible. Thus, anaerobic degradation is a promising alternative that may be used to remediate these sites. Recently, literature reports indicate complete anaerobic dechlorination of TCE and PCE by microorganisms enriched from wastewater treatment plants. We report here the complete dechlorination of TCE to ethene in anaerobic microcosms by microorganisms enriched from a TCE contaminated groundwater aquifer using glucose as an electron donor. Initial TCE degradation activity occurred after 10 days of incubation and TCE was no longer detected after 20 days of incubation. During the incubation period, the reductive dechlorination products associated with TCE degradation were detected. Ultimately, all of the TCE was converted to ethene. The glucose culture was further enriched and demonstrated increased rates of TCE conversion to ethene. Our results show that organisms isolated from a contaminated groundwater site are capable of completely degrading TCE to ethene at appreciable rates, and indicate the potential of using in situ anaerobic bioremediation to clean up TCE contaminated sites.

Reductive dechlorination of chlorinated ethene DNAPLs by a culture enriched from contaminated groundwater

“…Sufficient amounts of glucose were present in each vial to indicate that the glucose was not a limiting factor in the dechlorination of the chlorinated ethenes. Because VC is a long-lived intermediate in the reductive dechlorination of TCE and PCE (Freedman and Gossett, 1989;Bolesch et al, 1997), the effect of the initial VC concentration on the TCE dechlorination rate was investigated. The experimental results indicate that VC does not have a significant effect on the TCE dechlorination rate (Fig.…”

“…Resazurin (0.001 g/L) was added as an indicator of the redox potential. From this sample, a mixed culture of microorganisms capable of degrading TCE completely to ethene under anaerobic conditions was obtained (Bolesch et al, 1997).…”

“…Recently, Gossett and co-workers (Freedman and Gossett, 1989;DiStefano et al, 1991;DiStefano et al, 1992) and Zehnder and co-workers (de Bruin et al, 1992;Holliger et al, 1993) enriched microorganisms from activated sludge and river sediment that show the ability to completely convert PCE and TCE to either ethene or ethane under methanogenic conditions. Also, Bolesch and co-workers (Bolesch et al, 1997) enriched a mixed culture of microorganisms from a TCE-contaminated site that has the ability to anaerobically convert TCE to ethene. Recently, Maymo-Gatell and co-workers reported the isolation and characterization of a single organism that dechlorinates PCE to ethene (Maymo-Gatell et al, 1997).…”