The Research Of Rural Domestic Sewage Treatment With Simultaneous Nitrification And Denitrification By Modified SBR

In recent years,China has made great progress in urban sewage treatment,but the treatment of rural sewage is in the initial stage.Due to the lack of effective control and management of rural sewage,resulting in a large number of untreated rural sewage at random emissions,seriously affecting the rural residents of the production and life.It was necessary to controlled the discharge of nitrogen and phosphorus in sewage which was an important reason of eutrophication of water.Rural areas with relatively small amount of sewage generated,the weak economic base and the lack of rural management and technical level was relatively low and other conditions,research and development for rural sewage treatment technology,efficient low-cost removal of pollutants in the rural sewage,for improve the rural ecological environment and promote the sustainable and healthy development of rural areas is of great significance.Sequencing batch activated sludge(SBR)has advantages of strong sludge activity,strong impact loading,low operating cost and high pollutant removal rate.In this study,the effect of temperature,Sludge Retention Time(SRT)and Dissolved oxygen(DO)on the removal efficiency of COD and ammonia nitrogen was investigated by changing the aeration method.The microbial diversity of the system was analyzed by high throughput sequencing.Aeration time?SRT?temperature and DO have a great effect on the removal of pollutants.With the increase of aeration time,NH4+-N and COD concentrations decreased gradually,and remained stable at 240 min.With the increase of SRT from 10 d to 25 d,the removal efficiency of NH4+-N?COD and TN gradually increased,and the removal efficiency of NH4+-N,COD and TN was 95.04%,98.24%,69.05% when the SRT was 20 days.The content of polysaccharide and protein in the extracellular polymer loose layer increased first and then decreased with the increase of SRT.And the content of polysaccharide in the extracellular polymer was not changed obviously,and the trend of protein content was consistent with that of the loose layer.Temperature had an effect on the removal of pollutants and the content of extracellular polymers.When the temperature was 25 ?,the average removal rates of NH4+-N,COD and TN were 97.76%,91.27% and 68.76% respectively.The average removal rate of NH4+-N,COD and TN decreased by 31.52% and 10.74% and 15% respectively when the temperature decreased from 25 to 10 ? ?.The low temperature resulted in the increase of the content of polysaccharide in the extracellular polymer loose layer by 11.1mg/g,the protein content decreased by 6.15mg/g.In comparison,the effect of temperature reduction on the content of the loose layer is greater than the total extracellular polymer and the compact layer.The effect of dissolved oxygen concentration on COD and NH4+-N removal were not significant,but it had a great effect on simultaneous nitrification and denitrification.When the main reaction zone dissolved oxygen from 1.0-1.5mg/L reduced to 0.5-1.0mg/ L,COD removal rate decreased from 86% to 80%,NH4+-N average removal rate from 98.89% to 95.09%;and TN average removal rate increased from 64.6% to 72.58%,and the simultaneous nitrification and denitrification rate increased from 65.94% to 75.5%.The content of extracellular polymer and its polysaccharide and protein decrease with the decrease of dissolved oxygen concentration.Through the analysis of microbial diversity in SBR system,the diversity of community structure and species richness were all higher.There were large numbers of heterotrophic bacteria such as Saccharibacteria and Zoogloea,which were capable of degrading organic contaminants.There were also flora with denitrification capacity such as Thauera ? Flavobacterium and Cytophagaceae with potential nitrification and denitrification.Under the action of microorganisms,the pollutants in the sewage could be effectively removed.