||Chlorinated aliphatic hydrocarbons (CAHs) are frequently found as contaminants|
of soil and groundwater as a result of their widespread use in various industrial
processes and improper disposal methods. When they are released into the subsurface,
they tend to adsorb onto the soils and cause the appearance of DNAPL
(dense-non-aqueous phase liquid) pool. The 1,2-dichloroethane (1,2-DCA or EDC) has
been shown on induces hepatocellular carcinogens in mice and is a human carcinogen.
Application of in situ anaerobic bioremediation is a feasible technology to remediate
DNAPL site. In situ anaerobic bioremediation of chlorinated compounds (e.g.,
1,2-DCA) requires the injection of primary substrates to enhance the reductive
dechlorination process of chlorinated compounds. In this study, 1,2-DCA was used as
the target compound. The main objective was to compare the effectiveness of using
BS-1 (brand name) (developed for continuous carbon release) and commercially
available substrate C-Mix (brand name) (a carbon-substrate complex) on 1,2-DCA
dechlorination under anaerobic conditions. Results from the microcosm study show that
the pH in microcosms with BS-1 supplement remained in neutral (in the range from 6.5
to 7) throughout the experiment (93 days of operation). Approximately 99% of
1,2-DCA could be removed when BS-1 was added in the system. However, in
microcosms using C-Mix as the primary substrate, significant pH drop was observed.
Results from the column experiment show that 1,2-DCA can be degraded to below 0.05
mg/L (with initial concentration of 136 mg/L, flow rate of 0.1 L/day, and detention time
of 8 days) with the addition of BS-1 as the substrate. Results of the microbial diversity
analyses for the BS-1 microcosm show that the following bacteria were observed:
hydrogen-producing bacteria Clostridium sp., uncultured Desulfitobacterium sp. Clone
E15 bac, sulfate reduction species Sulfate-reducing bacterium LZK1, Desulfovibrio
psychrotolerans strain JS1, Delta proteobacterium K2-52, and Desulfovibrio sp.
SKKL8. Results from his study demonstrate that BS-1 can serve as the primary
substrate to enhance the reductive dechlorination of 1,2-DCA effectively.