ANAEROBIC DEGRADATION OF DCM DIFFUSING THROUGH CLAY

Two series of diffusion tests were performed to examine the degradatio n of dichloromethane (DCM) as it diffuses through clay. The first seri es showed the use of a synthetic leachate with no significant initial bacterial population diffusing through a plug of intact clay; there wa s an induction period of 95-135 d, during which diffusion was as expec ted in the absence of degradation, followed by a second stage, where d egradation occurred with an apparent half-life of less than 55 d at a temperature of 24 degrees C. The second series of tests examined the d iffusion of an actual leachate from the Keele Valley Landfill (KVL) (w hich provided both nutrients and a source of bacteria), through a comp acted clay. In these tests, the induction period was reduced to 40-60 d, after which the apparent half-life was 20 d or less at 27 degrees C . The diffusion coefficient for DCM was approximately 8 X 10-(10) m(2) /s, with partitioning coefficient K-d = 1.5 cm(3)/g. Biological activi ty was confirmed by evaluating the change in the concentration of aden osine-5-triphosphate and the biological activity reaction test (BART). The degradation of DCM did not produce any detectable levels of chlor omethane.