Degradation Of Nitrobenzene By Aerobic Granular Sludge Cultured In SBR

Nitrobenzene(NB)is a kind of organic matter which is an important intermediate in organic synthesis and also an important raw material in synthesis of dyes.It has important uses and huge output in chemical industry.Data show that there are a large number of nitrobenzene releasing iinto environment each year due to the rapid development of chemical industry.Nitrobenzene can be accumulated in the environment,which will do great harm to human beings because of its toxicity and mutagenicity.As a kind of persistent organic pollutant,it will lead to serious organic pullution of water.Direct cause of water eutrophication is the emissions of excess nitrogen and other nutrients.It will affect the safety of drinking water and the sustainable use of water resources.Therefore,it is extremely important to find effective denitrification and nitrobenzene degradation methods.This dissertation has developed the research of granulation of aerobic sludge,nitrobenzene degradation and wastewater denitrification,taking the sequencing batch reactor(SBR)and nitrobenzene as the platform and the only pollution.The research results are shown below:In order to obtain granular aerobic sludge,under the condition that take nitrobenzene as the only carbon and nitrogen energy with different concentration gradient,the aeration speed is 0.4 m3/h,the sludge settling time is 10 min.Mature granule close to sphere come into focus in aerobic sludge at 55 d.The average grain diameter and SVI of mature granule are 0.44 mm and 68 mL/g,removal amount of nitrobenzene during 24 h is 4.4g.Taking particle sludge gained by domestication to study the influence of different situations(including load,initial pH,aeration speed,temperature and MLSS)on reaction system degradation(including NB,COD and TOC)ability and monitoring variations of MLSS and SVI at the same time.The results show that nitrobenzene can be degraded completely under concentration less than 200 mg/L during a reation period(24 h),which degradation rate is 7.63 mg/(L·h),removal rates of COD and TOC are 98%and 93%.Settleability maintains good under nitrobenzene concentration of 400 mg/L with SVI less than 75 mg/L.The optimum initial pH is 7,optimum aeration speed is 0.5 m3/h,optimum temperature is 25?,optimum MLSS is 4.2 g/L.Under the conditions that operating parameters being consistent with them in granulation,the removal rate of TN is only 17%;for the conduct of denitrification,the removal rate of TN reached 28%after extending standing time;in order to enhance aerobic nitrification,nitrifying bacteria was added to the water,the removal rate of TN reached 35%;the nitrification rate[m(NH4-N)/m(MLSS)·t]of granular sludge is 0.61 mg/(g·h),denitrification rate[m(NO3-N)/m(MLSS)·t]is 0.05 mg/(g·h).Granular sludge has good performance in terms of degradation of high-concentration wastewater.At the same time the particularity of granule structure and technological characteristics of SBR form a microenvironment with aerobic and anaerobic zone coexisting in the system.Therefore it is possible that SBR system with granular sludge performs well in wastewater denitrification.It has practical implications in engineering applications.