Complete mineralization of poly-halogenated organic contaminants, such as chlorobenzenes (CBs), to innocuous end-products requires both anaerobic and aerobic biodegradation processes. Anaerobic dechlorination of highly chlorinated CBs can lead to the accumulation of daughter products such as monochlorobenzene and benzene, which are toxic and have higher mobility than their parent compounds in aqueous environments. However, aerobic biodegradation can readily mineralize these less chlorinated daughter compounds to harmless end-products. Natural anaerobic-aerobic gradients that exist in contaminated groundwater can be leveraged to sequentially pair anaerobic and aerobic biodegradation pathways to completely mineralize dissolved halocarbons in groundwater. In this research, we develop an in situ remediation strategy that deploys both anaerobic and aerobic degrading biofilms in a permeable barrier to passively intercept and treat dissolved CB contaminants carried by groundwater flow. A commercially-available anaerobic bioaugmentation culture that is able to rapidly transform CBs and develop degradative biofilms is paired with an enriched aerobic degrading culture to inoculate a “dual-biofilm” barrier. Using a continuous-flow upflow column to simulate a packed barrier along an anaerobic-aerobic interface, we evaluate the extent of biodegradation in a dual-biofilm system under varying electron donor and acceptor inputs. We experimentally compare the performance of this system to more traditional bioaugmented barriers inoculated with only one of the two paired cultures. Initial results indicate dechlorination of model compound 1,2,4-trichlrobenzene to dichlorobenzene in an anaerobic zone, followed by significant removal of the total CB mass in an aerobic zone. These results demonstrate the promise of a dual-biofilm approach to in situ remediation. Additional experiments to fully develop this strategy are ongoing.

Dual-biofilm reactive barrier for in situ remediation of chlorobenzenes at anaerobic-aerobic interfaces in contaminated groundwater

254th National Meeting (2017)

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