Screening Of Biological Pretreatment Nitrification Bacteria In Drinking Water In North And Its Removal Efficency Of Ammonia Nitrogen

At the same time of water shortage in China,it is also facing the problem of ammonia nitrogen pollution,especially in the northern region affected by temperature,low carbon-nitrogen ratio and other factors,resulting in more serious ammonia nitrogen pollution of water bodies,which increases the difficulty of drinking water treatment and is an urgent problem to be solved.Due to the advantages of heterotrophic nitrifying bacteria,the use of heterotrophic nitrifying bacteria for drinking water pretreatment has been applied in some water sources and water supply plants in recent years.At present,some research work on heterotrophic nitrifying bacteria has been carried out at home and abroad,but mainly focused on the treatment of normal-temperature sewage,and less research on low-temperature drinking water treatment.In view of this reality,heterotrophic nitrifying bacteria adapted to the characteristics of low temperature and drinking raw water were screened in this paper,and the characteristics of ammonia nitrogen removal were discussed.The research results can provide technical reference for ammonia nitrogen pollution control of low-temperature water.In view of the poor removal effect of ammonia nitrogen at low temperature,four heterotrophic nitrifying bacteria,N16,N19,N25 and N27,were isolated and screened from Songhua River at 10℃,and their culture characteristics,physiological and biochemical identification were carried out.N16,N19 and N27 were identified as Pseudomonas sp.and N25 as Bacillus sp.In order to better understand the growth and nitrification efficiency of the screened strains.The growth curves of the four strains were analyzed,and it was found that the growth rate of the strains was N27 > N25 > N16 > N19.The influencing factors of nitrification efficiency of four strains of bacteria were discussed in many aspects.It was found that these four strains had the best nitrification efficiency under the conditions of temperature of 20℃,p H of 8～9,initial ammonia nitrogen concentration of 5～7 mg·L^-1,C/N of 6～8 and inoculum volume of 5～10%.In order to improve the treatment effect of ammonia nitrogen,the construction of mixed flora and the optimization of ammonia nitrogen removal conditions were carried out.When the ratio of N16,N19,N25 and N27 was 3:1:3:1,the optimal ratio was obtained,and the removal rate of ammonia nitrogen was 54.97%.The optimum ammonia nitrogen removal conditions were determined to be the mixed bacterial flora with p H of 7,C/N of 10,inoculum volume of 3%,initial ammonia nitrogen concentration of 7 mg·L^-1.After optimizing the conditions,the ammonia nitrogen removal rate could reach 95.78%.The growth kinetics and ammonia nitrogen degradation kinetics of the experimental strains were analyzed,and it was found that their growth conformed to the Logistic model.The model suitable for ammonia nitrogen degradation of low-temperature heterotrophic nitrifying bacteria in this paper was determined to be a first-order reaction kinetic model by studying the ammonia nitrogen degradation law of a single strain.The ammonia nitrogen degradation coefficients of the four strains were 0.0128 d^-1,0.0219 d^-1,0.0099 d^-1,and 0.0569 d^-1,respectively,and the effects of different factors on the ammonia nitrogen degradation coefficients were analyzed by multiple linear regression.The model was used to predict the ammonia nitrogen degradation rule of mixed bacterial flora and ammonia nitrogen degradation rule after optimization of conditions,which has certain reference value for the practical application of this bacterial flora.