Effects of 1,1,1-Trichloroethane and Triclocarban on Reductive Dechlorination of Trichloroethene in a TCE-Reducing Culture

Abstract

Chlorinated compounds were generally present in the environment due to widespread use in the industry. A short-term study was performed to evaluate the effects of 1,1,1- trichloroethane (TCA) and triclocarban (TCC) on trichloroethene (TCE) removal in a reactor fed with lactate as the sole electron donor. Both TCA and TCC inhibited TCE reduction, but the TCC had a more pronounced effect compared to TCA. The TCE-reducing culture, which had never been exposed to TCA before, reductively dechlorinated TCA to 1,1-dichloroethane (DCA). Below 15 μM, TCA had little effect on the transformation of TCE to cis-dichloroethene (DCE); however, the reduction of cis-DCE and vinyl chloride (VC) were more sensitive to TCA, and ethene production was completely inhibited when the concentration of TCA was above 15 μM. In cultures amended with TCC, the reduction of TCE was severely affected, even at concentrations as low as 0.3 μM; all the cultures stalled at VC, and no ethene was detected. The cultures that fully transformed TCE to ethene contained 5.2–8.1% Dehalococcoides. Geobacter and Desulfovibrio, the bacteria capable of partially reducing TCE to DCE, were detected in all cultures, but both represented a larger proportion of the community in TCC-amended cultures. All cultures were dominated by Clostridium_sensu_stricto_7, a genus that belongs to Firmicutes with proportions ranging from 40.9% (in a high TCC (15 μM) culture) to 88.2%. Methanobacteria was detected at levels of 1.1–12.7%, except in cultures added with 15 and 30 μM TCA, in which they only accounted for ∼0.4%. This study implies further environmental factors needed to be considered in the successful bioremediation of TCE in contaminated sites.

Efficient and Complete Detoxification of Polybrominated Diphenyl Ethers in Sediments Achieved by Bioaugmentation with Dehalococcoides and Microbial Ecological Insights

“…, PCBs and PBDEs), threatening survival of the exogenous OHRB at the sites. Moreover, various organohalides may coexist at contaminated sites, which usually cause inhibitory, occasionally stimulatory effects on microbial reductive dehalogenation. − Soil and sediment are the sink of hydrophobic organohalide pollutants, where both chloroethenes and PBDEs have been detected. − However, the effects of co-contaminant PCE on the performance of bioaugmentation using exogenous OHRB like Dehalococcoides remain unknown.…”

Metagenomic Analysis Reveals Microbial Interactions at the Biocathode of a Bioelectrochemical System Capable of Simultaneous Trichloroethylene and Cr(VI) Reduction

“…Additionally, Desulfovibrio species were found. They are metabolically versatile microorganisms capable of anaerobic sulfate reduction and RD ( Men et al, 2013 ; Mao et al, 2017 ; Wen et al, 2017 ; Lim et al, 2018 ), already detected in TCE-consortia enriched on a variety of electron donors ( Kotik et al, 2013 ). Some Desulfovibrio species (i.e., D. vulgaris and D. desulfuricans ) were previously described as capable of heavy metal reduction in anaerobic environments ( Franco et al, 2018 ).…”

Microbial Reductive Dechlorination by a Commercially Available Dechlorinating Consortium Is Not Inhibited by Perfluoroalkyl Acids (PFAAs) at Field-Relevant Concentrations

“…47−51 The co-contaminants 1,1,1-trichloroethane, triclocarban, and chloroform have been shown to impact specific Dhc strains, typically having a greater impact on cells harboring vcrA than those harboring tceA. 6,52,53 One study 31 demonstrated that PFAAs can inhibit TCE degradation by Dhc strain 195 (harboring the tceA gene) but did not examine the strainspecific impact of PFAAs on a culture containing multiple Dhc strains.…”

“…Since specific Dhc strains are necessary to fully transform PCE to ethene, understanding strain-specific impacts of co-contaminants is essential to successful EISB. Geochemical parameters, including oxygen concentration, temperature, and pH, have been shown to impact RDase gene abundance and tend to most inhibit cells harboring the vcrA gene. − The co-contaminants 1,1,1-trichloroethane, triclocarban, and chloroform have been shown to impact specific Dhc strains, typically having a greater impact on cells harboring vcrA than those harboring tceA . ,, One study demonstrated that PFAAs can inhibit TCE degradation by Dhc strain 195 (harboring the tceA gene) but did not examine the strain-specific impact of PFAAs on a culture containing multiple Dhc strains.…”