Complete dechlorination and mineralization of para-chlorophenol (4-CP) in a hydrogen-based membrane biofilm reactor (MBfR)

Complete mineralization of para-chlorophenol (4-CP), a toxic xenobiotic compound, is challenging for water treatment due to the high energy use of destructive methods. Herein a sustainable hydrogen (H₂)-based membrane biofilm reactor (MBfR) is presented in treating 4-CP and NO₃-. With the increase of 4-CP surface loading, this technology can achieve continuous depletion (> 99%) of up to 100 mg/L 4-CP and 10 mg-N/L NO₃^- with minimal intermediates accumulation. The function of H₂, the controlling parameter in the H₂-MBfR, was examined in degrading 4-CP and NO₃^-. H₂ served as the electron donor in fueling the denitrification and dechlorination process. Activated by H₂, 4-CP can fulfill the ‘loop-closing degradation’ mediated by the heterotrophic bacteria: the products of 4-CP, served as electron donors, which refuel 4-CP degradation. In addition, H₂ created an anaerobic condition for the biofilm, and in turn, shifted the microbial community and the possible degradation pathways of 4-CP. The absence of H₂ induced the main functional bacteria changed from anaerobic bacteria Thauera to aerobic bacteria Xanthobacter, and further enhanced the genes encoding the enzymes responsible for oxidative dechlorination and aerobic activation of phenol. With no soluble chemical oxygen demand (sCOD) accumulated at the steady state, this technology provides promising visions into complete bioremediation of water containing 4-CP and NO₃^- with no residues.