Isolation,Identification And Denitrification Characteristics Of A Heterotrophic Nitrification-aerobic Denitrification Bacterium

The accumulation of nitrogen in water lead a series of problems such as eutrophication and ecological imbalance,which seriously threaten the survival and health of aquatic organisms and restrict the sustainable development of aquaculture industry in China.Heterotrophic nitrification-aerobic denitrification bacterial nitrogen removal is a new nitrogen removal technology,it can effectively remove ammonia nitrogen and nitrite nitrogen in the water.At present,the application of heterotrophic nitrification-aerobic denitrification bacteria in nitrogen removal from aquaculture wastewater has become a research hotspot.In this article,a strain with a strong nitrite removal ability was obtained by enrichment and domestication screening from the bottom mud of aquaculture ponds.The species and genus of the strain were identified,the nitrogen removal characteristics and the nitrogen removal effect of cell embedding were investigated.The main results are as follows:（1）A heterotrophic nitrification-aerobic denitrification bacterial strain HD-NAH was screened from the bottom mud of aquaculture pond,the strain HD-NAH was identified as Enterobacter kobei by observation of cell morphology,determination of physiological and biochemical parameters,and analysis of 16S r DNA sequences.（2）Effects of carbon source,C/N,p H value,temperature,and rotation speed on the denitrification characteristics of strain HD-NAH were investigated using single-factor test method.Results showed that the optimum denitrification conditions were as follows:trisodium citrate as carbon source,C/N of 18,initial p H as 7.0,temperature as 27°C,and rotational speed of 190 r/min.The removal rate of nitrite nitrogen by the strain was 99.98%,and the total nitrogen removal rate was 89.37%in 24 h under these conditions.By investigating the denitrification pathway of the strain,when the concentration of ammonia nitrogen in the environment was low（60.87 mg/L NH₄⁺-N）,the strain mainly performed nitrate-type nitrification;meanwhile,when the concentration of ammonia nitrogen was high in the environment（121.74 mg/L NH₄⁺-N）,the strain was prone to form nitrite-type nitrification,and there was a certain short-range heterotrophic nitrification-aerobic denitrification process.（3）This experiment chose polyvinyl alcohol and sodium alginate to the compound embedding of strain HD-NAH in order to improve adaptation.With the optimized preparation process of immobilized spheres:polyvinyl alcohol addition of 8%,sodium alginate addition of 2%,dropwise addition of Ca Cl₂ solution with 2%concentration,cross-linking for 15 h,and 20%addition of bacterial agent,the immobilized spheres had the best nitrogen removal rate,and the removal rate of total nitrogen from water reached 92.2%.The nitrogen removal effect and the environmental adaptability of the embedded strain was better than that of the free strain.