Isolation And Identification Of Efficiently Aerobic Denitrifying Phosphorus Removing Bacteria And Analysis Of The Factors Influencing Denitrification And Phosphorus Removal

In recent years,water eutrophication has become a major environmental problem in water pollution control in China.Among them,excessive emission of plant nutrients such as nitrogen and phosphorus into the water body is the important causes of eutrophication.Therefore,how to deal with the wastewater efficiently and economically,and solve the inherent contradiction in the traditional biological nitrogen and phosphorus removal system,are of great practical significance to control eutrophic water.In this study,the activated sludge from aerobic biochemical pond was used as the source of the strain,and the rich nitrogen and phosphorus medium was used as the simulated wastewater to provide carbon source and energy.Through the plate coating and streaking methods and the blue–white spot screening method,isolated and identified the highly effective aerobic denitrifying phosphate accumulating bacteria.The growth characteristics of the dominant strains and the influencing factors of the efficiency of nitrogen and phosphorus removal were investigated.The orthogonal experiment was designed to explore the best combination of factors for nitrogen and phosphorus removal,and the dominant strains should be applied in simulated wastewater for bioremediation of wastewater.The results obtained are as follows:?1?Using the specific screening method to isolate a efficient aerobic denitrifying phosphorus removal bacteria J16,to observe and record its growth characteristics,the growth adaptation period of the strain J16 was 0³ h,and 3²0 h was the logarithmic phase of growth,the rate of growth and reproduction was significantly accelerated,and reaches the maximum cell concentration at 20h,after which it entered into a stable phase of growth.The advanced PCR technology was used to amplify the 16S rDNA sequences of the strain J16 and phylogenetic analysis.The strain J16 was identified as Escherichia coli.the GenBank number of the bacteria is MF667015,and the preservation number of the bacteria is CGMCC NO.15044.?2?The results of single factor experiment on the effect of the denitrification and phosphorus removal efficiency of the strain J16 showed that the optimum temperature of denitrification and phosphorus removal of the strain was 30°C to 35°C.In this temperature range,the growth status of the strain J16was good,and the rate of nitrogen and phosphorus removal was up to more than90%.The optimum pH for denitrification and phosphorus removal is 7.2⁸,that is,the strain J16 was suitable for living in a neutral and weak alkaline environment,and in this environment,high-efficiency denitrification and phosphorus removal can be performed.The optimal inoculation amount was about 3%.The optimal initial PO₄^3--P concentration was 8.9 mg/L,and the denitrification and phosphorus removal rate of the strain J16 was the highest at this concentration.?3?The optimum operating conditions of denitrification and phosphorus removal by strain J16 were optimized by establishing an orthogonal test of 4factors and 3 levels.The results indicated that when the NO₃^--N concentration was 69.31 mg/L,the effects of various factors on the denitrification efficiency of J16 strain were respectively:temperature>inoculation amount>pH>the initial concentration of PO₄^3--P,and when the optimum conditions for denitrification were as follows:temperature was 35?,pH was 7.5,inoculation amount was 3%,the initial concentration of PO₄^3--P was 8.9 mg/L;The effects of various factors on the phosphorus removal efficiency of J16 strain were respectively:temperature>pH>inoculation amount>the initial concentration of PO₄^3--P,and when the optimum conditions for phosphorus removal were as follows:temperature was 35?,pH was 7.5,inoculation amount was 3%,the initial concentration of PO₄^3--P was 8.9 mg/L??4?Under the above optimal factor level conditions,the nitrogen and phosphorus removal capacity of the strain J16 was studied.After aerobic culture for 24 h,the concentration of NO₃^--N in the nitrogen and phosphorus-rich medium was reduced from 69.31 mg/L to 4.08 mg/L,and the denitrification rate was up to 94.11%;the concentration of PO₄^3--P was reduced from 8.9 mg/L to0.35 mg/L,and the phosphorus removal rate was up to 96.06%.?5?The application of the strain J16 to bioremediation of eutrophic water body showed that the intensifying sludge of different mass ratio was composed by strain J16 and single sludge,and all can promote the effect of denitrifying phosphorus removal in simulated wastewater.The intensifying sludge with a mass ratio of 2:1 had the highest denitrifying phosphorus removal efficiency.After 18 h culture,the highest nitrogen removal rate was up to77.06%,and the highest phosphorus removal rate was up to 94.34%,which was increased by 15.73%and 13.32%compared with the single sludge treatment.The results of this study provided effective bacterial resources for the treatment of eutrophic water,and provided theoretical and data support for the engineering application of denitrifying phosphorus removal bacteria.