Directional bioelectrochemical dechlorination of trichloroethene to valuable ethylene by introduction poly-3-hydroxybutyrate as a slow release carbon source

Bioelectrochemical dechlorination is one of the prospective and economic strategies for remediation of halogenated organics contaminated site, however, exploring the way of system construction with high detoxification efficiency and low organocarbon risk is still challenging. Herein, the slow-release organic carbon-sources (SOCs) coupled bioelectrochemical dechlorination system with generally accelerated trichloroethene (TCE) dechlorination performance and controllable organocarbon release was reported. It is interestingly found the introduction of Poly-3-hydroxybutyrate (PHB) achieved the greatly improved dechlorination efficiency (2.23 times improved k value) with valuable ethylene as a major metabolite (recovery ratio of 94.00 ± 1.62 %), reflecting the superior TCE detoxification and ethylene recovery potential. Microbial molecular mechanism analysis revealed the enriched electroactive dechlorinators (Geobacter and Desulfovibrio) in cathode representing the positive correlation (r > 0.8, p < 0.05) with TCE removal, were involved in the accelerated TCE dechlorination to 1,2-DCE. The non-electroactive dechlorinator (Dehalococcoides) observed in suspension symbiotically cooperating with some fermenters (Petrimonas, Sedimentibacter, etc.) and positively correlating with 1,2-DCE removal, was responsible for dechlorination of 1,2-DCE to ethylene through utilizing PHB fermentation generated H₂ as electron donor. PHB coupled bioelectrochemical dechlorination system realized the quick and directional conversion of TCE to ethylene, while maintaining the organocarbon release at a controllable and stable level, providing a feasible approach for simultaneous pollution removal and resource recovery by applying bioelectrochemical system in chlorinated hydrocarbon contaminated field.