Effect of sorption on the microbial reductive dechlorination of soil-bound chloroalkenes

摘要

The sequential, microbial reductive dechlorination of tetrachloroethylene and other chlorinated alkenes under methanogenic conditions was studied in liquid and soil slurry systems. A field contaminated soil was used and the effect of sorption on the reductive dechlorination rates was elucidated. As a result of microbial activity and enhanced reductive dechlorination, the extent of soil-bound contaminant release was five-fold more than in the soil slurry controls. The reductive dechlorination rates in the soil slurry system were between one and two orders of magnitude lower than those achieved in a soil-free culture. Therefore, the soil-bound contaminants exhibited lower bioavailability when compared to liquid-phase chloroalkenes. This study demonstrated the need for a continuous supply of electron donors to sustain an active primary metabolism (e.g., methanogenesis), as well as to supply the required electrons for the reductive dechlorination process. A very small fraction (less than 0.01percent) of the total reducing power used for both the methanogenesis and dechlorination processes was actually channeled towards the latter process. The results of this study indicate that development and/or enhancement of subsurface, methanogenic activity could effectively result in the biotransformation of soil-bound chloroalkenes.