Screening Of Aerobic Denitrifying Phosphorus-accumulating Bacteria And Its Nitrogen And Phosphorus Removal Performance

At present,urban domestic sewage is mainly treated by biological method for nitrogen and phosphorus removal.With the rapid increase of urban domestic sewage discharge and the trend of low C/N ratio,traditional biological methods are faced with insufficient carbon sources and different functional microorganisms competing with each other.Many problems such as nitrogen and phosphorus emissions are not up to standard,and many problems need to be solved.The aerobic denitrifying phosphorus-concentrating bacteria has attracted a lot of attention from scholars because of its good nitrogen and phosphorus removal and low carbon source requirements.Based on the principle of aerobic denitrification,the aerobic denitrifying phosphorus accumulating bacteria were screened and used to simulate urban domestic sewage treatment.The mechanism and influence factors of nitrogen and phosphorus removal were discussed.The following conclusions were drawn:?1?Screened a high-efficiency nitrogen and phosphorus removal strain with the function of heterotrophic nitrification-aerobic denitrifying phosphorus removal,identified as Pseudomonas stutzeri ATCC17588,named DB-11.The bacteria can use NO₃^-,NO₂^-to achieve aerobic denitrification and phosphorus removal,the removal rate of nitrate nitrogen was over 95%in the case of nitrate below 600 mg/L,and the removal rate of phosphorus was over 80%at the initial concentration is 15 mg/L.And the removal rate of phosphorus increased with nitrate concentration changed from 0 to 400 mg/L.What's more,the bacteria can achieve heterotrophic nitrification-aerobic denitrification under the conditions of ammonia,nitrate and nitrite nitrogen,in which the removal rate of phosphorus was 85%and the utilization rate of nitrogen source was 58.82%,100%and 98.74%,respectively.Therefore,the order of nitrogen source utilization was NO₃^--N>NO₂^--N>NH₄⁺-N.?2?Through the trace analysis of the metabolites in DB-11 nitrification and aerobic denitrification and the expression analysis of related enzymes,it is concluded that the bacteria may have the following nitrogen removal pathway:NH₄⁺-N??NH₂OH??NO₂^--N?NO₃^--N?NO₂^--N??NO?N₂O??N₂.In the aerobic denitrifying phosphorus process,DB-11 may synthesize PHB through the glycolytic pathway,and NO₃^-or NO₂^-act as an electron acceptor to oxidize PHB to provide energy for the intake of inorganic phosphate.?3?DB-11 had better nitrogen and phosphorus removal effect in the matrix of sodium acetate and sodium citrate as carbon source.In contrast,DB-11 had the best comprehensive removal effect of nitrogen and phosphorus when sodium acetate was used as carbon source.The C/N had a great impact on microorganisms,when the C/N ratio was 4-8,the aerobic denitrifying phosphorus removal ability of DB-11 was stronger.DB-11 had higher phosphorus removal capacity below 30°C,while it had a better denitrification effect above30°C,so the optimal temperature is 30°C.DB-11 had a strong tolerance to the acidity and alkalinity of the solution at pH 7-9 and achieved optimal nitrogen and phosphorus removal at pH of 8.?4?DB-11 had good removal effect on COD,TP,TN and NH₄⁺-N in simulated sewage with COD concentration of 600-1200 mg/L in the modified SBR reactor.And the simulated domestic sewage with a lower C/N ratio?4.1?can be discharged after treatment,and the total nitrogen and total phosphorus reach the first-class A emission standard of the Pollutant Discharge Standard for Urban Sewage Treatment Plants?GB 18918-2002?.