| As a common raw material in the chemical industry, nitrobenzene (NB) is intensivelyused in the aniline (AN) manufacturing process. Since NB is persistent and toxic in theenvironment, it has been listed as priority pollutant in many countries. Since NB wastewatercontains a lot of nitrite whicn is difficult to remove by physical and chemical method, thetreatment of NB under anoxic denitrifying conditions is a kind of new biological treatmentmethod.This experiment used sludge stored in the laboratory to the start anaerobic upflow filter(AF) reactor, and applied continuous running experiment to research anaerobic sludgeacclimatization for nitrobenzene and the effect of hydraulic retention time(HRT) on thereactor performance. The experimental results showed that through acclimatization, reactorobtained anaerobic sludge with high efficient degradation of nitrobenzene. HRT has asignificant impact on the removal of NB. As HRT was decreased form72h to4h, the NBremoval decreased from99.9%to93.2%, COD removale from94.8%to71.5%, and anilineyield from60.2%to24.8%.To investigate the degradation of NB under denitrifying conditions, experimentresearched the effect of COD/NO3--N on reactor effluent quality. The results found that themain product of NB degradation under denitrifying conditions was aniline. NB removalefficiency decreased from98.3%to78.7%with decrease of COD/NO3--N from20to3.3.Compareing the NB degradation under denitrifying conditions with under anaerobicconditions: with value of COD/NO3--N20, both had good nitrobenzene degradation (removalrate is above98%); with value of COD/NO3--N less than20, denitrification treatment hadworse nitrobenzene degradation. However, denitrification had a lower concentration of anilineand NB was mineralized.The amount of substrate has an important influence on water quality. With addition ofdifferent concentration of substrate, the influence of nitrobenzene concentration loading onthe reactor effluent is different. With addition of2500mg/L COD, the effluent concentrationof nitrobenzene was minimum with the best removal efficiency; With addition of1250mg/LCOD, nitrobenzene concentration increased slightly and AN began to be used by the denitrifying bacteria; With addition of750mg/L COD and250mg/L COD, the effluentconcentration of nitrobenzene were similar, but the latter had a very low COD degradationefficiency (impact load when the concentration of375mg/L, the COD degradation efficiency<5%), and effluent of the latter contained a lot of nitrate and nitrite. |
