Bioelectrochemical system for recalcitrant p-nitrophenol removal.

Bioelectrochemical system (BES) for recalcitrant p-nitrophenol (PNP) removal was investigated in this study. Effective removal of PNP at rates up to 9.14 ± 0.48 mol m(-3)d(-1) was achieved at an energy consumption as low as 0.010 ± 0.002 kWh mol(-1) PNP. PNP removal rate was enhanced with negative cathode potential, increased influent PNP concentration and shortened hydraulic retention time (HRT). Although the coulombic efficiencies at the anode did not exceed 40%, coulombic efficiencies for PNP removal at the cathode were above 70% at various cathode potentials. Compared with conventional anaerobic process, the cosubstrate dosage in BES was significantly reduced due to the high coulombic efficiencies at the cathode. p-Aminophenol (PAP) was identified as the dominant product of PNP reduction at the abiotic graphite cathode of BESs. This study demonstrated that the BES had a potential for efficient removal of nitrophenol pollutants from wastewater.