Chlorinated ethene contamination in groundwater is a major environmental concern at several sites. Bioaugmentation, which involves in situ delivery of electron donor, nutrients, and microorganisms to degrade the chlorinated ethenes, has been shown to be a cost-effective approach for addressing such sites. Dehalococcoides sp. (DHC) is the only microbial species known to completely dechlorinate PCE and TCE, and have been used extensively for bioaugmentation treatment of chlorinated ethenes. Despite their widespread application, a fundamental understanding of DHC activity, growth, and transport in situ is lacking.

A series of laboratory batch and column experiments were performed to evaluate the activity (with respect to chlorinated ethene biodegradation), growth, and transport of a commercially available DHC consortia. The specific objective of the study was to determine the mechanisms controlling DHC migration through the column while the bacteria were actively growing and degrading the contaminants.

Results of the column experiments showed that only a small fraction (<1%) of the injected DHC eluted through the column. No spatial gradient in aqueous phase DHC concentrations were observed, but measured aqueous phase DHC concentrations increased with time at a rate that was well-predicted by the Monod model coupled with a microbial transport model. VOC concentrations were also well-predicted by the coupled model. Overall results of the column experiments suggest that observed DHC distribution and VOC degradation during bioaugmentation is dependent upon a relatively small fraction of mobile and active DHC that grow and detach from retained biomass.