Rk. Rowe et al., ANAEROBIC DEGRADATION OF DCM DIFFUSING THROUGH CLAY, Journal geotechnical and geoenvironmental engineering, 123(12), 1997, pp. 1085-1095
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.