Conversion And Utilization Of Carbon Source In MPR And Its Nitrogen And Phosphorus Removal Effect

Micro-pressure internal circulation reactor（MPR）is a new type of sewage treatment process,which forms a circulating flow pattern through unilateral aeration,and constructs a variety of dissolved oxygen environments,which is conducive to simultaneous nitrogen and phosphorus removal.Organic carbon sources play an important role in biological nitrogen and phosphorus removal of sewage.Denitrifying bacteria and phosphorus accumulating bacteria have different metabolic pathways for different types of carbon sources,and their demands are different.In this paper,the single-stage aerobic sequencing batch reactor（MPR）was taken as the research object,the operation effect of different carbon source types and different influent nitrogen loads was investigated,the transformation law of pollutants and sludge endogenous substances was analyzed,and the characteristics of sludge and microbial flora structure were monitored and analyzed.The main conclusions are as follows:（1）Single carbon source and composite carbon source reactors have good pollutant removal effect.Under the condition 1 which average influent COD concentration of302～347mg/L,TP concentration of 3.8～4.1mg/L and TN concentration of 30mg/L,the effluent COD,TN and TP concentrations are below 40、10、0.5mg/L,respectively.When the influent concentration of TN increased to 50mg/L,the denitrification effect became worse,and the effluent NO₃^--N increased to 10mg/L The operation of complex carbon source reactor is unstable,and the concentrations of TN and TP in effluent water increase during sludge bulking in condition 2.（2）The changes of COD,TP and carbon source in sludge in single carbon source and composite carbon source reactors are similar.After aeration for 5～20min,the COD concentration drops to the lowest level,and obvious phosphorus release and PHA synthesis from sludge occur,and then TP and PHA continue to decrease.The phenomenon of TP release and absorption in complex carbon source reactor is not obvious,and PHA is kept at a low level;The initial phosphorus release rate in aerobic stage:single carbon source>complex carbon source>complex carbon source,which are 27.1,9.5 and 0.4mg/L respectively;the maximum PHA content in sludge synthesis:complex carbon source>single carbon source>complex carbon source,which are 32,21.3 and 8 mg（/g MLSS）respectively.（3）In a single operation cycle,the concentration of ammonia nitrogen in aerobic stage decreased continuously,and nitrate and nitrite did not accumulate obviously.Nitrogen removal was mainly based on simultaneous nitrification and denitrification SND.Under the condition of average influent C/N ratio of 11,the ESND of three types of carbon source reactors was 68%～70%.When the influent C/N ratio drops to 7,ESND drops to 60%～65%.（4）The sludge concentration in different types of influent carbon source reactors is different,and the average sludge concentration is:complex carbon source>complex carbon source>single carbon source,the ratio of MLVSS/MLSS is kept at 0.7～0.8.The sludge settling performance of single carbon source reactor is the best,and the average SV and SVI of sludge are 41%and 71ml/g,respectively.During sludge bulking in complex carbon source reactor,SVI reached above 150m L/g;The content of activated SOUR and EPS in sludge in single carbon source reactor was the highest,while that in complex carbon source reactor was the lowest in both groups.（5）Among the MPR systems with different influent carbon sources,the main dominant phyla are Proteobacteria,Bacillus,Actinobacteria,Patescibacteria;At the level of genus,Saccharimonadale and Tetrasphaera in the composite carbon source reactor reach 71%and11%,which is an important guarantee for the good nitrogen and phosphorus removal effect.