Synergistic Complete Detoxification of Mixed Chlorinated Solvents by Integrating Sulfidated nZVI and Organohalide-Respiring Bacteria

Cocontamination of groundwater with multiple chlorinated ethenes and ethanes, particularly trichloromethyl alkanes like 1,1,1-trichloroethane (1,1,1-TCA), presents persistent remediation challenges due to their toxicity toward organohalide-respiring bacteria (OHRB) like Dehalococcoides and the frequent accumulation of hazardous intermediates. Here, we report a complementary abiotic–biotic strategy that couples sulfidated nanoscale zerovalent iron (S-nZVI) with an enriched dechlorinating culture. The enrichment culture exhibited broad dechlorination versatility toward chlorinated ethenes and ethanes due to the synergistic interactions of Desulfitobacterium and Dehalococcoides but was fully inhibited by 1,1,1-TCA. In contrast, S-nZVI rapidly degraded 1,1,1-TCA to ethane and ethene without toxic intermediate accumulation but incompletely transformed other chlorinated ethanes and ethenes. Integrating the two approaches achieved complete detoxification (>98%) of a mixed solvent containing 1,1,1-TCA, 1,1,2-TCA, and trichloroethene, without the accumulation of toxic intermediates like vinyl chloride. Mechanistically, S-nZVI eliminated the inhibitory 1,1,1-TCA by completely detoxifying it to ethane and ethene, priming OHRB for subsequent microbial detoxification of residual 1,1,2-TCA and vinyl chloride. This sequential division of labor represents a distinct abiotic–biotic synergy beyond conventional hydrogen provision or parallel dechlorination, reducing intermediate accumulation and enhancing system robustness. Our findings highlight a promising design principle for effective in situ remediation of complex mixed-solvent contaminated environments.