Study On The Technology Of Anaerobic Nitrophenol Reduction Assisted By Electirc Field

Anaerobic reduction was an important step of bioremediation for nitroaromatic compounds, however, convention anaerobic reduction process existed insufficient in some aspects, such as low efficiency and unstability. There had been growing interest in the development of bioelectrochemistry method, because it integrated the advantages of biological treatment, electrolytic dissociation and electrochemical oxdatiom/reduction process. In this project, bioelectrochemisty system was proposed for the improvement of anaerobic nitrophenol-treating system, which was up-flow anaerobic sludge bed (UASB in short). Biological reduction system assisted by electric field (also knowed as UASB-BES system) would be constructed with enhanced co-metabolic reduction of nitrophenols (using p-nitrophenol as substrate, PNP for short) achieved in the presence of electric field. In this study, both the reduction of PNP and the cosubstrate consumption would been in UASB and UASB-BES. In addition, the power consumption performance was investigated in UASB-BES.In UASB, the performance of three cosubstrates, namely sodium acetate, glucose and methanol, was compared, demonstrating that glucose had the best performance for the reduction of PNP. However, sodium acetate had the least consumption. Considering the cost of external cosubstrates, sodium acetate was much better for engineering application. Both the dosage of cosubstrates and PNP concentration had significant impact on the reduction of PNP. The result showed that the increase of sodium acetate concentration would promote the reduction of PNP. When influent PNP concentration>250mg/L, anaerobic bacteria were inhibited gradually.In UASB-BES, the presence of electric field would promote the reduction of PNP. When the current density changed from OA/m3to4.7A/m3, the performance of PNP removal also increased. Compared to conventional UASB system, in the presence of electric field, the consumption of electron donor sodium acetate significantly reduced and methane production was inhibited. In UASB-BES, nitrophenol load rate obviously increased compared to conventional UASB system. Under a high current condition, the yield of aminophenol significantly improved. When the current density was at4.71A/m3, the power consumption was only0.017kwh/mol. Compared to pure electrochemical process, the power consumption significantly reduces. Compared to BES with proton exchange membrane, the power consumption was also reduced. The high coulombic efficiency of cathode indicated that the anaerobic reduction was dominant for PNP removal. The coulombic efficiency of anode (6.5%) was relatively low compared to the diaphragm BES. But the simple design of this reactor avoided the problem of high cost and concentration polarization caused by the use of proton exchange membrane.The results of this paper showed that the UASB-BES system had a broad application prospect of the reduction pretreatment on refractory organic pollutants such as nitrophenols.