Simultaneous debromination and mineralization of bromophenol in an up-flow electricity-stimulated anaerobic system

Due to highly recalcitrant and toxicological nature of halogenated organic compounds, conventional anaerobic dehalogenation is often limited by low removal rate and poor process stability. Besides, the reduction intermediates or products formed during dehalogenation process, which are still toxic, required further energy-intensive aerobic post-treatment. In this study, an up-flow electricity-stimulated anaerobic system (ESAS) was developed by installing cathode underneath and anode above to realize simultaneous anaerobic debromination and mineralization of 4-bromophenol (4-BP). When cathode potential was -600 mV, high TOC removal efficiency (98.78 ± 0.96%), complete removal of 4-BP and phenol could be achieved at 4-BP loading rate of 0.58 mol m^-3 d^-1, suggesting debrominated product of 4-BP from cathode (i.e., phenol) would be utilized as the fuel by the bioanode of ESAS. Under high 4-BP loading rate (2.32 mol m^-3 d^-1) and low electron donor dosage (4.88 mM), 4-BP could be completely removed at acetate usage ratio as low as 4.21 ± 1.42 mol acetate mol^-1 4-BP removal in ESAS, whereas only 13.45 ± 1.38% of 4-BP could be removed at acetate usage ratio as high as 31.28 ± 3.38 mol acetate mol^-1 4-BP removal in control reactor. Besides, electrical stimulation distinctly facilitated the growth of various autotrophic dehalogenation species, phenol degradation related species, fermentative species, homoacetogens and electrochemically active species in ESAS. Moreover, based on the identified intermediates and the bacterial taxonomic analysis, possible metabolism mechanism involved in enhanced anaerobic debromination and mineralization of 4-BP in ESAS was proposed.