Efficient nitro reduction and dechlorination of 2,4-dinitrochlorobenzene through the integration of bioelectrochemical system into upflow anaerobic sludge blanket: A comprehensive study

Bioelectrochemical system (BES) coupled upflow anaerobic sludge blanket (UASB) was developed for the removal of recalcitrant pollutants but lack of a comprehensive study. Thus in this study an integrated UASB-BES system was operated continuously for 240 d to systematically investigate the feasibility of the enhanced reduction of 2,4-dinitrochlorobenzene (DNCB), with the key operation parameters, the system stability as well as the microbial biodiversity emphasized. The results indicate that high voltage supplied had a positive effect on DNCB reduction but a negative impact for the overhigh voltage (>1.6 V). The ability to resist shock loading was strengthened in the UASB-BES system in comparison with the control UASB system. High-throughput sequencing analysis suggested that the enhanced reduction of DNCB in UASB-BES could be attributed to higher diversity and the enrichment of reduction-related species, potential electroactive species and fermentative species. Both DNCB removal and dechlorination gradually increased with the increase of operation time, indicating the improved performance of the coupled UASB-BES system. The heatmap visualized only slight differences in the microbial community during long-term operation, indicating the stability of the microbial community. The observed efficient and stable performance highlights the potential for long-term operation and full-scale application of the UASB-BES coupled system particularly for highly recalcitrant pollutants removal. (C) 2015 Elsevier Ltd. All rights reserved.