Chemical-physical parameters and microbial community changes induced by electrodes polarization inhibit PCB dechlorination in a marine sediment

• Published in: Journal of hazardous materials 2024-05, Vol.469, p.133878, Article 133878
• Main Authors: Botti, Alberto, Musmeci, Eliana, Matturro, Bruna, Vanzetto, Giampietro, Bosticco, Caterina, Negroni, Andrea, Rossetti, Simona, Fava, Fabio, Biagi, Elena, Zanaroli, Giulio
• Format: Article
• Language: English
• Subjects: anodes; cathodes; dechlorination; electrochemistry; graphene; Marine sediments; microbial communities; Microbial electrochemical technologies; Microbiome; oxidation; Polychlorinated biphenyls; redox potential; Reductive dechlorination; sulfur
• ISSN: 0304-3894; 1873-3336; 1873-3336
• DOI: 10.1016/j.jhazmat.2024.133878

Microbial reductive dechlorination of organohalogenated pollutants is often limited by the scarcity of electron donors, that can be overcome with microbial electrochemical technologies (METs). In this study, polarized electrodes buried in marine sediment microcosms were investigated to stimulate PCB reductive dechlorination under potentiostatic (−0.7 V vs Ag/AgCl) and galvanostatic conditions (0.025 mA·cm−2-0.05 mA·cm−2), using graphite rod as cathode and iron plate as sacrificial anode. A single circuit and a novel two antiparallel circuits configuration (2AP) were investigated. Single circuit polarization impacted the sediment pH and redox potential (ORP) proportionally to the intensity of the electrical input and inhibited PCB reductive dechlorination. The effects on the sediment’s pH and ORP, along with the inhibition of PCB reductive dechlorination, were mitigated in the 2AP system. Electrodes polarization stimulated sulfate-reduction and promoted the enrichment of bacterial clades potentially involved in sulfate-reduction as well as in sulfur oxidation. This suggested the electrons provided were consumed by competitors of organohalide respiring bacteria and specifically sequestered by sulfur cycling, which may represent the main factor limiting the applicability of METs for stimulating PCB reductive dechlorination in marine sediments. [Display omitted] •Electrochemical input inhibited PCBs dechlorination in a marine sediment.•Sulfate reduction was primed by the electrochemical input.•Electrochemically-induced pH changes can contribute to the inhibition of dechlorination.•Double circuit systems mitigated pH shifts and the inhibition of dechlorination.