Potential stimulation of oxidative biodegradation of vinyl chloride in an anaerobic matrix with a bioelectrochemical technology

Vinyl chloride (VC) is a toxic byproduct from microbial hydrogenolysis of chlorinated solvents such as perchloroethylene and trichloroethylene. This study evaluates a bioelectrochemical system (BES) using a microbial electrochemical snorkel (MES) configuration at pilot scale to enhance the oxidative degradation of VC in an anaerobic matrix. Three BES units were operated for nine months, reducing VC concentrations from 1840 ± 2.1 μg/L to non-detect levels. A robust redox gradient was established, significantly increasing the microbial electron transfer within target treatment zone. 16S rRNA-based taxonomic analysis revealed enrichment of electroactive genera such as Desulfurivibrio, Sulfuricurvum, and f_Comamonadaceae, correlating positively with system voltage and chloride accumulation, while no intermediate indicative of stepwise dechlorination process was detected. Metagenomics detected a high abundance of genes associated with extracellular electron transfer (e.g., pilA, mtrC) and oxidative degradation pathway (e.g., alkB, pmoA), while VC-dechlorinating dehalogenases (e.g., vcrA) were missing. The MES potentially facilitated oxygen-dependent enzyme activity by enabling indirect access for microorganisms in anaerobic zone to oxygen. These evidence supports that VC degradation proceeds primarily through an oxidative pathway under anaerobic conditions, providing the first evidence that BES may stimulate this oxidative biodegradation, offering an alternative strategy for bioremediation of VC-contaminated sites.