Reactive iron barriers: a niche enabling microbial dehalorespiration of 1,2-dichloroethane

A reactive iron barrier in a contaminated aquifer with low pH was found to dechlorinate 1,2-dichloroethane (1,2-DCA) in situ. This chlorinated ethane is known to resist abiotic reduction by zero valent iron. Samples taken up-gradient and within the barrier were used to inoculate anaerobic batch cultures amended with various electron donors. Cultures inoculated with groundwater from within the reactive iron barrier reduced 1,2-DCA to ethene. The same effect could be achieved by simultaneously supplying hydrogen while neutralising pH. The presence of iron or hydrogen at neutral pH had negligible effects on 1,2-DCA reduction in cultures inoculated with groundwater sampled up-gradient of the barrier. Molecular microbial community characterisation revealed that Dehalobacter species were more abundant in groundwater sampled from within the barrier. These findings suggest reactive iron barriers represent a remediation technology for 1,2-DCA degradation acting through in situ recruitment of 1,2-DCA reducing bacteria such as Dehalobacter.