The Anaerobic Biodegradation Of Nitrobenzene And The Application Of Combined A/O System To Wastewater Containing Nitrobenzene

Nitrobenzene, one of the nitroaromatic compounds, a representative organic pollutant in industrial wastwater, is widely used for the manufacture of dyes, pharmaceuticals, reduction to aniline, and solvent. Many countries categorize it as a priority pollutant. This experiment used residual activated sludge of urban wastwater plant as inoculum to start UASB reactor, and applied continuous running and static experiment to research anaerobic sludge acclimatization for nitrobenzene in mesophilic range, optimum environmental factor for anaerobic sludge, anaerobic biodegradation characteristic of nitrobenzene and aerobic sludge acclimatization for aniline in room-temperature, and the influencing factors of anaerobic/aerobic reactor and the steady performances of anaerobic-aerobic process for removing nitrobenzene were surveyed. The follwing results were achieved after one year and half:(1)The residual activated sludge of urban wastwater plant could effectively start UASB reactor. It's beneficial to keep good status of UASB for increasing COD load according to the concentration of effluent VFA.(2)The nitrobenzene-degrading anaerobic granular sludge were acclimated and enriched when a mixture of glucose and nitrobenzene was employed as influent of anaerobic reactor. The anaerobic reactor was operated under 3.134~0.930kg/(m3·d) COD, 18~236mg/L nitrobenzene and 30~24h HRT, more than 93% of nitrobenzene was removed. The chief degradation product of effluent was aniline, but COD removal tended to falling owing to the accumulation of aniline.(3)In mesophilic range(35℃), the optimum environmental condition of anaerobic sludge was pH6.0~7.0, sanility0.5%~1.0%. Anaerobic granular sludge were better than free bacterium in harmful environment. As co-metabolizing substrate, glucose could promote the degradation of nitrobenzene.(4)The results of static batch test showed that anaerobic granular sludge absorbed nitrobenzene firstly, then degraded it. The anaerobic biodegradation kinetics of nitrobenzene were followed by first-order reaction without exterior electron donor, k, reaction rate constant reduced along with the concentration of nitrobenzene increased. A little aniline could be opened loop, and mineralized sequentially under anaerobic condition.(5)If a little primary substrate-glucose were added in the influent-water, the performance of anaerobic reactor would be promoted greatly. Glucose could play an very effective part in restoring activity of anaerobic sludge which was restrained.(6)The combined anaerobic-aerobic system was effective and suitable for treating wastewater containing high concentrate nitrobenzene. A/O system was operated with influent 141.6~212.4mg/L nitrobenzene, 30h HRT (anaerobic process) and 8h HRT (aerobic process), COD concentration in effluent was lower to 34.2~70.0mg/L, nitrobenzene and aniline concentration in effluent were respectively 0.56~13.6mg/L and 0.1~0.15mg/L, water quality in effluent achieved first-class wastewater discharge standard of GB8978―1996.