Anaerobic biodegradation of trichloroethylene sorbed by a surrogate soil organic matter

The effects of aging trichloroethylene (TCE) with a surrogate soil organic matter (SSOM) on its anaerobic biodegradation and desorption characteristic s were studied, Surrogate soil organic matter comprised of composted sphagn um moss was used as a model sorbent, and Desulfomonile tiedjei was used as a model member of an anaerobic consortium capable of reductive dechlorinati on, 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-dichloroet hylene (DCE) by D. tiedjei in this period decreased by 72% from 2 to 30 d o f aging. Although there was an increase in the equilibrium desorption coeff icient (Kd) With aging, sorption was completely reversible. Hence, the redu ced availability of TCE for degradation was not coupled with irreversible s orption. To examine the longer-term fate of TCE, the unaged TCE-SSOM slurri es 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 eigh t 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.