| Heterotrophic nitrification-aerobic denitrification bacteria（HN-AD bacteria）have been studied for several decades,but there are still few examples of application in wastewater treatment,mainly due to the lack of strains with high nitrogen removal efficiency and strong environmental adaptability.In this study,a variety of samples that may enrich HN-AD bacteria were collected and a large number of screening work was carried out.Finally,an efficient HN-AD strain was obtained by optimizing the screening method.The main results of this study are as follows:（1）124 HN-AD strains were preliminarily screened from environmental samples such as fish pond sediment,pig farm wastewater and activated sludge of sewage treatment plant.The simulated wastewater treated by different primary screening bacteria was color-coded to quickly identify the concentration of retained nitrogen,so as to compare the nitrogen removal capacity of primary screening bacteria,and finally obtain the high-efficiency HN-AD strain named FS.FS was identified as Pseudomonas putida by 16S r DNA sequencing and whole genome sequencing.（2）The removal rates of ammonia nitrogen（NH4+-N）,nitrate nitrogen（NO3--N）and nitrous nitrogen（NO2--N）by strain FS were above 99.5%,and the average removal rates were 8.43 mg/（L·h）,5.34 mg/（L·h）and 6.32 mg/（L·h）,respectively.When the three forms of nitrogen existed at the same time,FS strain preferentially removed NH4+-N.（3）In the simulated wastewater with NH4+-N as the only nitrogen source,the effects of temperature,rotational speed,p H,carbon source,chemical oxygen demand/total nitrogen（COD/TN）and nitrogen concentration on the growth and nitrogen removal ability of strain FS were investigated by single factor optimization method.The optimum growth and nitrogen removal conditions are as follows:temperature is 30℃～35℃,rotation speed is 210 r/min,p H value is 6.0～8.0,sodium citrate is used as carbon source,COD/TN value is 20,NH4+-N concentration is 100 mg/L.（4）Strain FS has a strong ability to adapt to the environment.The conditions for its function are as follows:temperature is 15℃～35℃,p H is 5.0～9.0,NH4+-N concentration is10～1000 mg/L.In the above range,the denitrification rate can reach more than 95.01%.（5）Strain FS has a good treatment effect on coal chemical wastewater.After adding certain kinds and concentrations of minerals,the removal rates of NH4+-N,NO3--N and NO2--N can reach 96.88%,80.15%and 97.31%respectively,and the total removal rates of three kinds of nitrogen can reach 93.62%.The average nitrogen removal rate was 7.17mg/（L·h）.However,in the wastewater without mineral supplement,only a small amount of NH4+-N was removed,and the total removal rate of three kinds of nitrogen was 8.48%,the average nitrogen removal rate was 0.44 mg/（L·h）.It shows that strain FS is strict with inorganic salts.The strain FS screened in this study has high efficiency in removing a variety of inorganic nitrogen,strong adaptability to the environment,and good treatment effect on actual wastewater,which has great application value in the field of sewage treatment. |
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