Isolation And Screening Of Aerobic Denitrifying Bacteria And The Study Of Denitrification Characteristics

With the speeding up of industrialization and urbanization,the seven majior river systems of China are polluted in different degree,and nitrogen pollution is one of the main pollution factors among numerous pollution factors.In recent years,eutrophication of water bodies happen frequently because of the excessive nitrogen emissions,and the abuse of nitrogen fertilizers lead to nitrate exceeding standard in the undergroud water,so it is significant that taking effective measures to solve nitrogen pollution.Traditional biological nitrogen removal technologies have certain significance in the field of nitrogen wastewater treatment,however,on accout of the different requirements of nitrifying bacteria and denitrifying bacteria in DO,pH and other reaction conditions,traditional biological technologies usually need to separate aerobic area and anaerobic area,which leads to complex process and long running time.But the discoverment of aerobic denitrifying bacteria solves this problem successfully,aerobic denitrifying bacteria are able to denitrify in aerobic condition,which can make nitrification and denitrification occur in the same time and space.The study adopted limiting dilution method,chromogenic medium method and streak plate method screening three strains of aerobic denitrifiers from eight environment samples,named ADM 2-2,ADM 7-2 and ADM 8-1.Through 16S rDNA sequencing analysis,strain ADM 2-2.ADM 7-2 were identified as Pseudomonas chengduensis,and strain ADM 8-1 was identified as Pseudomonas chloritidismutans.Strain ADM 2-2 and ADM 8-1 were chosen to study further,which had better aerobic denitrifying abilities,and the 48h nitrate removal rate of the two strains were 87.83%and 88.06%sparately.Through denitrification analysis of two strains under different cultured conditions,the optimum pH of strain were 11 and 9,the optimum carbon sources were sodium succinate,the optimun C/N ratios were 11 and 13,and the optimum concentration of NaCl were 20 g/L and 30 g/L.In order to study the aerobic denitrification characteristics further,put the efficient aerobic denitrifying bacteria ADM 2-2 and ADM 8-1 into SBR reactors.Trough the contrast tests,compare the aerobic denitrification among activate sludge,activate sludge added strains and strains.In order to study handling capacity of denitrifying bacteria under different concentrations of organic wastewater,the influent C/N ratio need to be decreased by degrees,and it decreased from 20:1 to 17:1,14:1,11:1,8:1 and 5:1.During the stable operation of reactors,the optimum nitrate removal rate of three SBR reactors were 78.93%,83.99%and 88.17%seperately.Thus,the addition of aerobic denitrifying bacteria would increase the nitrogen removal ability in some ways.According to the biodiversity high-throughput sequencing results of different reaction phases,the biodiversity of reactor ? and reactor ? that were added strains was lower than reactor ?,and Pseudomonas was the superiority strain,thus,the Pseudomonas which existed in reactor ? and reactor ? abundantly were Pseudomonas chengduensis and Pseudomonas chloritidismutans possibly,and the more Pseudomonas existed,the higher aerobic denitrfication was.Thus,after enlage cultivation,strain ADM 2-2 and ADM 8-1 not only kept excellent aerobic denitrification,but also had strong competitiveness.