Nitrogen Removal And Denitrification Products Generation By Heterotrophic Nitrifiers Pseudomonas Sp. And Its Kinetic Characteristics

The massive discharge of nitrogenous wastewater makes water eutrophication become more and more serious,so the nitrogen removal from water body has been the focus problem.However,conventional BNR processes gradually exposed the weaknesses of low efficiency,high energy consumption,weak stability,excessive greenhouse gas?GHG?emission and so on.To overcome the aforementioned disadvantages,the novel BNR processes have been developed,and especially the isolate of hetertrophic nitrifing bacteria?HNB?provide a new idea for energy efficient nitrogen removal.In addition,most of HNB can perform organic degradation,nitrification and denitrification simultaneously with the characteristics of rapid growth,high acitivity,various proliferating substrate and strong environmental adaptability.In practise,these HNB exhibit marvelous ability in treating groundwater,high strength nitrogenous wastewater and industrial sewage.However,the understanding of the biology,kinetics and denitrification mechanisms of HNB are still unclear,which definitely constrict the application of HNB.In the study,the physiological characteristics,nitrogen removal characteristics,product generation,influencing factors,functional gene and kinetic analysis were systematically studied with the research object of two heterotrophic nitrifiers that possessing efficient nitrogen removal ability.The main results are as follows:?1?The testing strains could utilize NH₄⁺-N?NO₂^--N and NO₃^--N as the sole nitrogen source to perform nitrification or denitrification.At a concentration of 100mg/L,the nitrogen removal efficiencies were 99.1%,99.5%and 99.8%for strain YH and 96%?99.9%and 99.5%for strain YL,respectively.Combining with physiological characteristics,the successful amplification of denitrifying functional genes?napA,nirK and nosZ?futher proved the aerobic denitrifying chatacteristics of two strains.The nitrogen removal pathway was speculated as:NH₄⁺?NH₂OH?NO₂^–?NO₃^–?NO₂^–?NO?N₂O?N₂.?2?The bacterial growth process of stain YH and YL matched to the Logistic model?R²>0.99?,and the nitrogen degradation conformed to the Compertz model?R²>0.99?.For strain YH,the order of maximum conversion rate of nitrogen?R_m?was NH₄⁺-N>NO₃^--N>NO₂^--N,and that of lag time?t₀?was NO₃^--N>NO₂^--N>NH₄⁺-N.For strain YL,the order of R_m was NH₄⁺-N>NO₂^--N>NO₃^--N,and that of t₀ was NO₃^--N>NO₂^--N>NH₄⁺-N.The determination of the fitting parameters helps to further clarify the metabolic characteristics of the strains.?3?The optimal conditions for nitrogen removal by the strains were succinate as the carbon source,C/N=10,T=30-37?,r=160-200 r/min,and pH=6.0-8.0.?4?The main denitrification product of strain YH and YL was N₂,and there was little N₂O emission during this process.Moreover,the gaseous nitrogen products of the strains accounted for 30-40%of the removed TN,whereas the intracellular nitrogen accounted for 50-60%of the removed TN.In addition,some unfavorable factors,such as high C/N,low pH,high temperature and the accumulation of ammonia and nitrite,would induce the increment of N₂O emission.However,most environmental factors had less effect,which certificate the ability of two strains to control N₂O emission.