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Anaerobic Biodegradation of Trichloroethylene Sorbed by a Surrogate Soil Organic Matter

Dep. of Civil Engineering & Applied Mechanics, McGill Univ., Montréal, QC H3A 2K6, Canada.
Environmental Bio-Engineering Group, Biotechnology Research Institute, National Research Council of Canada, Montréal, QC H4P 2R2, Canada.

^* Corresponding author (Tamara.Sheremata{at}nrc.ca).

ABSTRACT

The effects of aging trichloroethylene (TCE) with a surrogate soil organic matter (SSOM) on its anaerobic biodegradation and desorption characteristics were studied. Surrogate soil organic matter comprised of composted sphagnum moss was used as a model sorbent, and Desulfomonile tiedjei was used as a model member of an anaerobic consortium capable of reductive dechlorination. After TCE was aged with the sterile SSOM for periods of 2, 14, and 30 d, the completely mixed batch reactors were inoculated with D. tiedjei cells and incubated for 5 d. The mass of TCE dechlorinated to cis-1,2-dichloroethylene (DCE) by D. tiedjei in this period decreased by 72% from 2 to 30 d of aging. Although there was an increase in the equilibrium desorption coefficient (K_d) with aging, sorption was completely reversible. Hence, the reduced availability of TCE for degradation was not coupled with irreversible sorption. To examine the longer-term fate of TCE, the unaged TCE-SSOM slurries were inoculated with D. tiedjei and then incubated for longer times (15, 24, and 29 d vs. 5 d). The conversion of TCE to cis-1,2-DCE was up to eight times greater than what was observed in control experiments without SSOM. Therefore, although aging resulted in reduced TCE biodegradation for short-term incubation (5 d), longer-term incubation (29 d) with the unaged SSOM resulted in extensive TCE dechlorination (up to 40%) to cis-1,2-DCE.