Isolation,Screening And Nitrogen Removal Characteristics Of A Novel Heterotrophic Nitrification And Aerobic Denitrification Bacterium Under Low Temperature

With the rapid development of human society and the increasing expansion of population,a large number of nitrogen oxides are discharged into natural water bodies,resulting in the proliferation of algae and the death of aquatic organisms due to hypoxia,resulting in serious pollution to surface water and groundwater.The treatment of nitrogen-containing wastewater has gradually become one of the research hotspots in the field of environmental science.The new heterotrophic nitrification aerobic denitrification denitrification process has attracted extensive attention of researchers.In northern China,the sewage temperature is low in winter,and most aerobic denitrifying bacteria are extremely sensitive to temperature,resulting in poor microbial activity and substandard effluent quality.Therefore,it is of great significance to explore the heterotrophic nitrifying aerobic denitrifying bacteria in low temperature which could effectively remove different nitrogen sources for sewage treatment in cold areas.To solve this problem,the activated sludge samples from sewage plants and sediment samples from Wuliangsuhai were collected,isolation and screening of low-temperature tolerant heterotrophic nitrifying aerobic denitrifying bacteria and denitrification characteristics were investigated:(1)In this study,six heterotrophic nitrification aerobic denitrification strains with low temperature tolerance were isolated,and the denitrification performance of the strains was tested.The strain TY1 with the best denitrification effect was selected as the target strain.This strain efficiently metabolized nitrogen from ammonium at low temperatures,utilizing NH₄⁺-N,NO₃^--N and NO₂^--N as nitrogen sources.By 16S r RNA gene sequencing and morphological observation,combined with its physiological and biochemical characteristics,the target strain TY1 was identified as Acinetobacter calcoaceticus TY1.(2)After the strain was cultured for 60 hours with sodium succinate as carbon source,125 r/min,8?,and p H 7.2,the maximum removal rates of NH₄⁺-N(106 mg/L),NO₃^--N(70 mg/L)and NO₂^--N(35 mg/L)were 97.47%,81.85%and 97.51%respectively.The removal rates of NH₄⁺-N(50 mg/L)and NO₃^--N(50 mg/L)from mixed nitrogen sources were 99.25%and 43.63%.The removal rates of NH₄⁺-N(50mg/L)and NO₂^--N(50 mg/L)were 91.60%and 29.38%,and there was almost no accumulation of NO₂^--N in the process of culture.(3)The nitrogen metabolism-associated genes amo A,nir K,and nos Z were identified in TY1,it is further proved that strain TY1 has heterotrophic nitrification aerobic denitrification function at the gene level.(4)Optimal requirements for growth and nitrogen removal were pH 7,shaking speed of 90 r/min,a C/N ratio of 10,and sodium citrate for the carbon supply.The ability to denitrify at low temperature suggests TY1?s potential for wastewater management.