Screening And Denitrification Characteristics Of An Efficient Heterotrophic Nitrification-aerobic Denitrification Bacterium WZ17

Livestock and poultry breeding industry is the pillar industry for agricultural economy,agricultural non-point pollution has become biggest pollutant now.Ammonia nitrogen as one of the most important pollutants has already become the research focus in the field of environmental pollution control.Biological nitrogen removal process was currently widely concerned due to its low cost,high efficiency and no second pollution.However,the traditional biological denitrification theory has been smashed by the discovery of heterotrophic nitrification-aerobic denitrification bacteria,which can complete nitrification and denitrification processes under aerobic conditions simultaneously has become the focus of many scholars'research at home and abroad.In present study,a heterotrophic nitrification–aerobic denitrification bacterium was isolated from swine wastewater.The strain was identified through 16S r DNA.Meanwhile,the culture conditions were optimized by single factor experiment and response surface methodology?RSM?.On this basis,the nitrification and aerobic denitrification properties of the strain were analyzed.The enzymatic activity analysis,kinetic analysis and denitrification performance analysis under different conditions were used to understand the growth conditions and denitrification mechanism of the strain.Furthermore,the application potential of strain WZ17 in swine wastewater treatment was investigated by bio-augmentation,which provide the theoretical basis for future practical applications.The main research results are as follows:A heterotrophic nitrifying bacterium WZ17 was isolated and identified as Acinetobacter junii WZ17 through molecular biological identification.The preferred conditions of strain wz17 were sodium acetate as the carbon source,C/N ratio of 26,p H of 8.0,temperature of 26?,and the shaking speed of 165 r/min.The bacterial growth process of strain WZ17 matched to the Logistic model,and the nitrogen degradation conformed to the Compertz model.The maximum removal rates are 8.47,5.76 and 5.16mg·?L·h?^-1,and the removal efficiencies are 99.31%,91.82%and 83.60%,respectively,with ammonia nitrogen,nitrate and nitrite as sole nitrogen source.The accumulation of nitrate and nitrite nitrogen in the whole process were only 0.13 and 0.14 mg/L,and nearly 25.89%of the removed NH₄⁺-N was converted to intracellular nitrogen.The specific activities of HAO,NAP and NIR were 0.0313,0.0438,0.0130 U/mg,respectively.Combined with the nitrification and denitrification process,it can be seen that the denitrification pathway of strain WZ17 is:NH₄?-N?NH₂OH?NO₂?-N?NO₃?-N?N₂.The removal rate of NH₄?-N and COD were 5.84%and 26.85%during a 10-day Biofortification test.After adding the sodium acetate as carbon source,the removal rate of NH₄?-N increased to 57.65%,after filtering out the influence of indigenous microorganisms,the removal rate of NH₄?-N reached 77.38%,and the effluent COD concentration was 102.91mg/L.The lower purification efficiency of the strain in actual pig wastewater was related to lower C/N in raw water and competition with indigenous microorganisms.