Screening Identification And Denitrification Characteristics Of Heterotrophic Nitrifying And Aerobic Denitrifying Bacterium X1-L

With the rapid development of China's economy,the total discharge of industrial wastewater and domestic sewage is increasing day by day,and the content of ammonia nitrogen and organic matter in water is seriously exceeding the standard.Heterotrophic nitrification and aerobic denitrification technology,as a new denitrification technology,can not only transform ammonia nitrogen into gaseous products,but also have a good removal effect on COD[1].At present,bacillus in gram-positive bacteria has a strong ability to remove ammonia nitrogen and COD,and domestic and foreign scholars regard it as the dominant strain in industrial and municipal sewage treatment [2].Heterotrophic nitrifying aerobic denitrifying bacteria have been widely concerned for their rapid growth,strong resistance and high denitrifying efficiency.However,there are few reports on single strains at present.Therefore,in-depth study on denitrifying performance of pure strains is of great significance for enriching germplasm resources and applying in practical projects.In this study,several strains of bacteria were selected from the acclimated and mature activated sludge,and a strain X1-L with good performance was selected for in-depth study by measuring its growth curve and capacity of heterotrophic nitrification and oxygen denitrification.The morphological characteristics of strain X1-L were observed,and it was determined to be short rod-shaped,with spores in the body,uneven surface and no flagella.According to the determination of microbial identification plate,54 kinds of carbon sources could be utilized by strain X1-L.Through systematic analysis of three characteristic parameters,strain X1-L was determined to belong to bacillus.In order to determine strain X1-L,the 16 S rRNA gene was sequenced,through Blast software to other bacterial 16 S rRNA gene sequences and compare the strains X1-L,and use the MEGA 7.0 software to establish the phylogenetic tree,found its and Bacillus flexus in relatively close relatives,the homology is as high as 99.86%,belong to bend the Bacillus,the registration number for MT457091 in Genbank.In order to determine strain X1-L growth and nitrogen efficiency,needs to determine its growth curve within 24 h,and in a different form of nitrogen as the sole nitrogen source of culture medium,the determination of strain X1-L growth and nitrogen,the results show that 24 h after training COD removal rate reached more than 95%,NH₄⁺-N,NO₂^--N and NO₃^--N removal rates were 99.6%,95.5%,96.5%,explain strains X1-L take advantage of the ability of different nitrogen source were stronger.In order to improve strain X1-L ammonia nitrogen removal ability,on its growth environment conditions optimization,set different p H value respectively 5,6,7,8,9,different carbon source,respectively for sodium citrate,sodium acetate,sodium succinate,glucose,sodium tartrate wine,different C/N ratio respectively 7,9,11,13,15,and different temperatures of 15 ?,20 ?,25 ?,30 ?,35 ? were determinedunder different conditions in the growth of OD660 and NH₄⁺-N,NO₂^--N and NO₃^--N,the utilization of the COD The results showed that at p H value of 8,sodium succinate as carbon source,C/N ratio of 11 and temperature of 30 ?,the growth capacity and ammonia nitrogen removal effect of strain X1-L were the best.