The Characteristics Of Cold-tolerant Aerobic Denitrifying Bacteria Pseudomonas Plecoglossicida Y-1 And Its Characteristics For Nitrogen Removal From Different Nitrogen Sources And Domestic Sewage

For the ecosystem,water is one of the important constituent factors,and it is also an indispensable material for social production,human life,and the survival of various organisms.Since the reform and opening up,China’s economy has developed rapidly,and the population increased quickly.However,people ignored the protection of the environment while developing the economy and pursuing a better life.A serious of human activities such as the unreasonable discharge of industrial wastewater and urban sewage,excessive application of nitrogen fertilizer and the oversupply with fish food has caused an increase in the concent of“trinitrogen”in water bodies such as rivers,lakes,sesa and groundwater.The pollution problem is getting worse.It’s very important for both environmental protection and human health to removal the excess nitrogen in water bodies.Among the existing denitrification methods,one of the widely used methods is biological nitrogen removal method,and the aerobic denitrifying bacteria are getting more and more attention because of the low construction cost and operating cost.Most of the aerobic denitrifying bacteria reported so far are sensitive to extreme environments,especially low temperature water bodies.In sewage treatment plants from late autumn to early spring,the low temperature of sewage water reduces the efficiency of biological nitrogen removal and accumulation of nitrification products.The phenomenon caused the increased of nitrate nitrogen content in the water,and the total nitrogen concentration exceeded the standard and failed to meet the discharge standard.In order to adapt to the complex and changeable sewage environment and improve the removal rate of nitrogen in sewage treatment,it is very important to select strains that have alkali resistance and can effectively remove nitrate nitrogen,ammonium nitrogen and total nitrogen in low temperature sewage environment.Our laboratory isolated and screened a strain from the soil of the long-flooded winter paddy field in Guizhou and named it Y-1,the strain can effectively remove nitrate nitrogen at15℃and has strong tolerance to alkaline environment.In order to study the characteristics of strain Y-1,the strain was identified by morphological observation,specific phospholipid fatty acid identification and 16S rRNA,then researched the removal of nitrate nitrogen by the strain under different environmental conditions.The identification results showed that strain Y-1 was Pseudomonas plecoglossicida,it is a denitrifying bacteria,and this is the first report about this bacterium can perform denitrification.The experiments showed that the optimal conditions for strain Y-1 to remove nitrate nitrogen are:temperature 15℃,pH 7,rotation speed 150 r/min,C/N 15,inoculation amount 1.5×10⁸ CFU,and glucose is the most suitable carbon source.When the pH is as high as 11 even 12,strain Y-1 can still remove nitrate nitrogen effectively.When under low temperature and alkaline environments,strain Y-1 can growth and denitrification as usual,it’s a cold and alkali resistant aerobic denitrifying bacteria.We studied the removal of different nitrogen sources by strain Y-1 under optimal conditions.The results show that when use single nitrogen as nitrogen source,the strain can remove high concentration of nitrate nitrogen well,and can completly remove nitrate nitrogen within 36 hours,but it can’t remove high concentration of nitrite nitrogen.The removal of ammonium nitrogen is achieved by assimilation rather than nitrification.When the mixed nitrogen source is 50 mg/L NO₃^--N+50 mg/L NO₂^--N,the strains could use both nitrate nitrogen and nitrite nitrogen with removal rates of 92.42%and 91.94%,respectively.When the mixed nitrogen source is 50 mg/L NO₃^--N+50 mg/L NH₄⁺-N,the strain preferentially used ammonium nitrogen for growth,and at the 36h,the removal rate of ammonium nitrogen was 100%,and the removal rate of nitrate nitrogen reached 92.74%at the 60th hour.When the mixed nitrogen source is 50 mg/L NO₂^--N+50 mg/L NH₄⁺-N,after 48 hours,the ammonium nitrogen was removed completely,and at the 60th hour the removal rate of nitrite nitrogen was 53.33%.When the mixed nitrogen source is 50 mg/L NO₃^--N+50 mg/L NO₂^--N+50 mg/L NH₄⁺-N,at the 48h the removal rate of ammonium nitrogen reached 100%,the removal of nitrate nitrogen and nitrite nitrogen started slowly after 36h,and the final removal rates were 71.30%and 56.94%,respectively.The growth of the strain was generally delayed in the presence of nitrite nitrogen,indicating that nitrite nitrogen can inhibite the growth of strain.When the concentration of nitrite nitrogen reached a certain level,the strains grow slowly or hardly and even die.The strain Y-1 was applied to the actual domestic sewage treatment,and different carbon sources were added at the same time to explore the removal of nitrate nitrogen,ammonium nitrogen and total nitrogen in the actual domestuc sewage.And the experimental water samples were tested for phospholipid fatty acids,the changes of microbial community in water were analyzed,and the relationship between nitrogen removal in water and microbial biomass in water was investigated.The results showed that the removal of TN,NH₄⁺-N,and NO₃^--N were effectively improved by the addition of separate bacterial agents or input of both bacterial agents and carbon source.Compared with CK which did none treatment,the removal rate of NO₃^--N by bacteria addition and sodium acetate treatment P3,bacteria addition and glucose treatment P2,bacteria addition only treatment P1 increased by 48.67%,40.61%,34.83%,TN removal rates increased by 16.13%,17.42%,and 7.21%,respectively,and removal rates of NH₄⁺-N increased by 47.31%,48.35%,and 7.95%respectively.Compared with CK,the total PLFA,bacteria,fungi,G-bacteria,and G+bacteria contents of treatment P1,P2,and P3 increased obviously.On the basis of the study,the removal of TN,NH₄⁺-N and NO₃^--N is in connection with the microbial biomass,and nitrogen removal in water can be promoted by increasing microbial biomass.