Anaerobic Degradation of DCM Diffusing through Clay

Abstract

Two series of diffusion tests were performed to examine the degradation of dichloromethane (DCM) as it diffuses through clay. The first series showed the use of a synthetic leachate with no significant initial bacterial population diffusing through a plug of intact clay; there was an induction period of 95–135 d, during which diffusion was as expected in the absence of degradation, followed by a second stage, where degradation occurred with an apparent half-life of less than 55 d at a temperature of 24°C. The second series of tests examined the diffusion of an actual leachate from the Keele Valley Landfill (KVL) (which provided both nutrients and a source of bacteria), through a compacted 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°C. The diffusion coefficient for DCM was approximately 8 × 10−10 m2/s, with partitioning coefficient Kd= 1.5 cm3/g. Biological activity was confirmed by evaluating the change in the concentration of adenosine-5-triphosphate and the biological activity reaction test (BART). The degradation of DCM did not produce any detectable levels of chloromethane.