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

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 mbed−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 (106–107 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.

► The dynamics of an anaerobic biotrickling filter treating trichloroethene (TCE) were investigated.
► Reductive dehalogenation resulted in cis-1,2-dichloroethene (cis-DCE), vinyl chloride (VC) and ethene.
► Bioaugmentation with Dehalococcoides BAV1 which can effectively dechlorinate cis-DCE and VC was performed.
► Bioaugmentation dramatically improved the conversion of TCE to ethene and shifted the distribution of dehalogenation by-products.
► qPCR and RT-qPCR of reductive dehalogenase genes showed that performance improvements were due to the added strain.