Isolation,Identification And Denitrification Characteristics Of Heterotrophic Nitrifying And Denitrifying Bacteria Zobellella Sp.XH5

With the development of economy,people’s living standards have been gradually improved,and environmental problems have become increasingly prominent.China is facing severe challenges in water pollution control,especially the problem of excessive nitrogen emissions has been widely concerned.Microbial denitrification is strongly advocated in the field of water treatment because of its economic and efficient advantages.The nitrification and denitrification processes in traditional biological denitrification processes can not be completed simultaneously in the same space because of different requirements.Heterotrophic Nitrification-aerobic denitrification bacteria can overcome this shortcoming.Therefore,highly efficient heterotrophic Nitrification-aerobic denitrification bacteria are screened out to become microorganisms.Hot issues in the field of water treatment.In this study,a heterotrophic Nitrification-aerobic denitrification bacteria was isolated from the sediment of Qinghe River in Beijing and identified.In order to improve the denitrification efficiency,the denitrification characteristics and the optimization of heterotrophic nitrification conditions of the bacteria under different culture conditions were investigated.In addition,the immobilized denitrification characteristics of the bacteria and the effect of water treatment applied to the unipolar A/O system were studied,which provided a basis for future engineering applications.Theoretical guidance.The main conclusions of this study are as follows:（1）A heterotrophic Nitrification-aerobic denitrification strain XH5 was obtained by microbial screening and isolation.According to its morphological,physiological and biochemical characteristics and 16S rDNA identification method,the strain was identified as Zobellella sp.,named Zobella sp.XH5.（2）In the experiments of heterotrophic nitrification and aerobic denitrification of strain XH5,factors such as carbon source type,C/N,pH,temperature and rotational speed can affect the denitrification effect of strain XH5.The optimum heterotrophic nitrification conditions of strain XH5 are as follows:carbon source is trisodium citrate,C/N is 11,pH is 8.0,temperature is 25℃,shaking speed is 150r/min,initial concentration of NH₄⁺-N is 175 mg/L can be degraded to 16.78 mg/L,and removal rate of NH₄⁺-N is up to 90.42%.The optimum Aerobic Denitrification Conditions of strain XH5 were as follows:glucose as nitrogen source,C/N 13,pH 8.0,temperature 30℃,shaking speed 150 r/min.The initial concentration of NO₃^--N was238 mg/L,and there was almost no accumulation of nitrous nitrogen.The denitrification effect is very obvious.（3）Response surface methodology was used to optimize the factors affecting the heterotrophic nitrification process of strain XH5.The results showed that the degradation rate of ammonia nitrogen was the best within 24 hours when C/N=11,pH=8.5 and T=25℃.Combining Box-Behnkens experimental design and response surface model,the culture conditions of strain XH5 were optimized.The optimum values were C/N=10.72,pH=8.27,T=25.72℃.Under these conditions,the degradation rate of ammonia nitrogen could reach 94.82%.（4）Heterotrophic nitrification and aerobic denitrification of microbial pellets were more obvious in the experiment of immobilized XH5.The removal rates of NH₄⁺-N and NO₃^--N were 89.1%and 93.55%respectively.However,the removal efficiency of NH₄⁺-N and NO₃^--N by microbial pellets after immobilization was lower than that of strain XH5 itself.It may be due to the activity of enzymes in strain XH5by polyvinyl alcohol and sodium alginate.It can inhibit the removal rate and reduce the removal rate.（5）In the experiment of treating A/O system with immobilized strain XH5,in the first stage of the system,due to the action of activated sludge,the average removal rate of NH₄⁺-N is about 85.04%,the highest is 89.01%,the average removal rate of TN is about 54.23%,the highest is 61.56%,and the average removal rate of COD is about 80.66%,the highest is 84.38%.In the second stage of the system,due to the addition of immobilized microbial pellets,the average removal rate of NH₄⁺-N is about 91.41%,the highest is 94.48%,the average removal rate of TN is about 64.16%,the highest is 69.98%,and the maximum removal rate of COD is 87.24%.The concentration of NO₃^--N in effluent is larger than that in influent,and the concentration of NO₂^--N is less than 0.1 mg/L,with little change.The results showed that immobilized microbial pellets had better heterotrophic nitrification effect and aerobic denitrification had a certain denitrification effect,but the denitrification rate decreased.This may be due to the design parameters of A/O system did not reach the optimum level.It is still necessary to improve and debug the A/O system in the later stage to improve its denitrification rate.