Efficient 2,4-dichloronitrobenzene removal in the coupled BES-UASB reactor: Effect of external voltage mode

In this study, bioelectrochemical-upflow anaerobic sludge blanket (BES-UASB) system was developed for treatment of 2,4-dichloronitrobenzen (DClNB) containing wastewater to investigate the effect of external voltage with different supplying modes. Results showed that 2,4-dichloroaniline (DClAN) was under detection limit in R1 (applied with intermittent voltage) and R2 (applied with continuous voltage) when the DClNB loading increased from 25 to 100gm³d^-1 (hydraulic retention time (HRT) was decreased from 24 to 6h) while sudden accumulation of DClAN (1.7mgL^-1) was observed in R0 (control). Dechlorination efficiency (DE) decreased to 32.7%, 45.0% and 45.3% in R0, R1 and R2 when HRT was further shortened to 4h. Microbial community analysis indicated the significant enrichment of dechlorination-related species in R1 and R2 compared with R0, e.g., Dehalobacter and Dehalococcoides. In summary, the BES-UASB system with intermittent voltage is an alternative process for efficient treatment of DClNB containing wastewater, and the energy input was reduced markedly.