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Complete dechlorination and mineralization of pentachlorophenol (PCP) in a hydrogen-based membrane biofilm reactor (MBfR)

Long, Min, Ilhan, Zehra Esra, Xia, Siqing, Zhou, Chen, Rittmann, Bruce E.
Water research 2018 v.144 pp. 134-144
Azospira, Desulfomicrobium, Flavobacterium, Thauera, Xanthobacter, bacteria, biodegradation, biofilm, bioremediation, carbon dioxide, carboxylation, dechlorination, denitrification, groundwater contamination, hydrogen, microbial communities, mineralization, nitrates, pentachlorophenol, phenol, pollutants, sulfates, sulfur, water treatment
Complete biodegradation and mineralization of pentachlorophenol (PCP), a priority pollutant in water, is challenging for water treatment. In this study, a hydrogen (H2)-based membrane biofilm reactor (MBfR) was applied to treat PCP, along with nitrate and sulfate, which often coexist in contaminated groundwater. Throughout 120-days of continuous operation, almost 100% of up to 10 mg/L PCP was removed with minimal intermediate accumulation and in parallel with complete denitrification of 20 mg-N/L nitrate. PCP initially was reductively dechlorinated to phenol, which was then mineralized to CO2 through pathways that began with aerobic activation via monooxygenation by Xanthobacter and anaerobic activation via carboxylation by Azospira and Thauera. Sulfur cycling induced by SO42− reduction affected the microbial community: The dominant bacteria became sulfate-reducers Desulfomicrobium, sulfur-oxidizers Sulfuritalea and Flavobacterium. This study provides insights and a promising technology for bioremediation of water contaminated with PCP, nitrate, and sulfate.