Isolation And Ammonia Nitrogen Removal Characteristics Of Biological Denitrification Bacteria

Ammonia nitrogen pollution is one of the major environmental problems in modern society,which not only leads to eutrophication of water,but also directly endangers the health of human beings and plants and animals.Biological nitrogen removal has the advantages of economy,high efficiency and no secondary pollution,and has been widely used in the treatment of ammonia nitrogen pollution.In this study,two strains Y-4 and ZHU-1 with good ammonia-degrading effects were isolated from subaqueous sludge,and their biological identification was carried out.The optimal denitrification conditions of these two strains and the laboratory strain Candida tropicali were investigated,and their tolerance to different ammonia nitrogen concentrations was studied,and the denitrification ability of these three strains was investigated.After preliminary identification of morphological observation and18S r DNA gene analysis,strain Y-4 was identified as Pichia sp,and ZHU-1 was identified as Meyerozyma athensensis.After single factor experiment and orthogonal experiment optimization,the optimal denitrification conditions of strain Y-4 were25℃,p H 8.0,C/N 20,salinity 2%,optimal denitrification conditions of strain ZHU-1 were 37℃,p H 7.5,C/N 50,salinity 3%,and optimal denitrification conditions of the C.tropicali were 35℃,p H 8.0,C/N 30,salinity 4%.Among them,the C.tropicali could tolerate 6%salinity and the degradation rate of ammonia nitrogen reached 65.3%.When the C/N was 50,the ammonia nitrogen degradation rate and the OD₅₉₅ of the strain ZHU-1 was 63.17%and was 4.2.Through the ammonia nitrogen tolerance research of Y-4,ZHU-1and C.tropical,it was found that the denitrification of three strains occurred mainly in the logarithmic phase.The ammonia nitrogen degradation rate of three strains could reach 100%in the medium with the initial concentration of 100 mg/L.When the initial concentration of ammonia nitrogen was more than 200 mg/L,the ammonia nitrogen degradation rate of three strains was decreased with the concentration of ammonia nitrogen increasing,but the maximum ammonia nitrogen degradation rate and bacteria growth did not change significantly.When the initial ammonia concentration was 1000 mg/L,the degradation rates of ammonia nitrogen were 18.8%,19.3%and 19.8%,and the maximum degradation rates of ammonia nitrogen were 5.04,4.20 and 4.38 mg/L/h,respectively.In the nitrite degradation experiment,Y-4,ZHU-1 and C.tropical all had good degradation effects,with similar degradation characteristics,and the denitrification mainly occurred in the logarithmic growth period of the strains.In the nitrite medium with an initial concentration of 200mg/L,the consumption rates reached 100%,with the maximum consumption rates of 7.81,10.22,and 6.72 mg/L/h,respectively.The consumption rate of nitrite reached 80.5%,85.7%and 75.8%at 24 h,and the nitrite was completely comsumed at 48 hours.The final OD₅₉₅ of three strains was 3.32,3.60,and 3.31,respectively.The final nitrite consumption rate was 100%.