Isolation,Identification And Performance Study Of Heat-tolerance Nitrogen Removal Bacterial Strain

Nitrogen pollution control is an important problem to be solved urgently in coal chemical wastewater.The removal of ammonia nitrogen from this kind of industrial wastewater usually requires biological nitrogen removal technology such as nitrification and denitrification.However,the temperature of coal chemical wastewater often exceeds 37?,which affects the activity of nitrogen removing microorganism,leading to the substandard effluent.In this study,two strains of heat-tolerance ammonia-oxidizing bacteria(AOB)A1 and A2 and two strains of heat-tolerance denitrifying bacteria(DB)D1 and D2 were isolated from activated sludge under high temperature of 42? as selective pressure.Their species and genera were identified by 16S rRNA gene sequencing and BLAST comparison.The optimal temperature,pH and maximum nitrogen conversion performance of each strain were investigated by batch experiments.The optimal pH and C/N range of the short-cut nitrification-denitrification process composed of the preferred ammonia-oxidizing strain A2 and the denitrification strain D1 were investigated by batch experiments.The results showed that the strains A1 and A2 were both classified as Aquamicrobium aestuarii,which showed straight rod shape under electron microscope.The optimal growth temperature was 42?,and the optimal pH was 9.0.Under these conditions,the maximum ammonia nitrogen conversion rate of the strain A1 was 1.56 mg N·g protein-1·h-1,and its half saturation coefficient was 111.41 mg/L.The maximum ammonia nitrogen conversion rate of the strain A2 was 1.62 mg N·g protein-1.h-1,and its half saturation coefficient was 62.60 mg/L.The strains D1 and D2 were identified as Pseudomonas stutzeri,which were rod-shaped under electron microscope.The optimal denitrification temperature,pH and C/N ratio were 40?,7.0 and 4:1 respectively.Under these conditions,the maximum nitrite-nitrogen removal rate of strain D1 was 17.19 mg N-g protein-1·d-1,and its half saturation coefficient was 31.48 mg/L.The maximum nitrite-nitrogen conversion rate of strain D2 was 18.34 mg N·g protein-1·d-1,and its half saturation coefficient was 35.41 mg/L.Interestingly,the N2O accumulation rates of both denitrifiers were more than 70%.The results showed that the short-cut nitrification-denitrification technology composed of ammonia oxidizing bacterial strain A2 and denitrifying bacterial strain D1 could achieve the optimal initial pH range of 8.0?9.0 and the optimal initial C/N range of 2:1-3:1.The nitrogen removal rate reached 100%,and the N2O accumulation rate reached 51.3%under the high temperature of 42?.Based on the above experimental results,the heat-tolerance and high-efficiency nitrogen removing bacteria strains were successfully isolated and obtained in this study,which provided technical support and strain reserve for the biological treatment and nitrogen recovery of coal chemi cal wastewater with high ammonia nitrogen.