Bioaugmentation of an anaerobic biotrickling filter for enhanced conversion of trichloroethene to ethene

摘要

During biological reduction of trichloroethene (TCE), incomplete reduction to partially dechlorinated intermediates cis-1,2-dichloroethene (cis-DCE) and vinyl chloride (VC) can occur due to kinetic and inhibitory limitations. In this study, an anaerobic biotrickling filter was inoculated initially with a mixed culture containing Dehalococcoides spp. that contained the TceA and VcrA reductive dehalogenases. After significant accumulation of cis-DCE and VC was observed in the bioreactor effluent, it was hypothesized that bioaugmentation with Dehalococcoides strain BAV1, which contains the BvcA dehalogenase responsible for the metabolic dechlorination of cis-DCE and VC, would improve the conversion of TCE to ethene. It was found that at TCE loadings of 8-9 g m_(bed)~(-3) h~(-1), bioaugmentation with strain BAV1 resulted in 45% conversion of TCE to ethene, as opposed to less than 10% prior to bioaugmentation. Strain BAV1 was found to grow to the same density (10~6-10~7 cells per g of packing material) as Dehalococcoides strains containing the TceA and VcrA dehalogenases. Strain BAV1 was also confirmed to be active, as determined by RT-qPCR of the BvcA mRNA. This study shows that it is possible to enhance the performance of continuously fed dechlorinating bioreactors by using a consortium that contains all three known reductive dehalogenases in the TCE dechlorination pathway. This is also the first study where a gas-phase biotrickling filter has been bioaugmented with a single strain to result in improved performance.