Research On Operation Regulation Of Modified AA/O Process In Rainy Season Based On Confluence System

With the rapid development of economy and the acceleration of urbanization,the impervious area of urban underlying surface is also increasing,which reduces the infiltration capacity of rainwater.There are still a large number of confluent pipelines in the old urban area;this part of the rainwater will enter the sewage treatment plant through the pipe network system after scouring the surface.The water quality and quantity of this influent water are significantly different from those of normal influent,which will impact the normal operation of sewage treatment plant and affect the stability of effluent of combined sewage treatment plant.In the summer of 2007,the cyanobacteria pollution broke out in the Taihu Lake basin,which greatly affected the water supply in Wuxi city.The environmental protection department required that the effluent from sewage enterprises and municipal wastewater treatment plants in the Taihu Lake water network should strictly implement the Class A standard of GB18918-2002.Suzhou City is also investigating the sewage disposal enterprises in the Taihu Basin,and preparing to implement stricter emission standards than the Class A standard.The implementation of the new standards will bring new challenges and opportunities to the operation of sewage treatment plants.Many water quality indicators will face the risk of exceeding the standard,especially when the rainy season comes,the water quality and quantity of influent will change dramatically,and the difficulty of stabilizing effluent will further increase.In terms of operation cost and technology,higher requirements are put forward for sewage treatment enterprises and sewage treatment plants.Based on the investigation of hydrometeorology and precipitation in Zhangjiagang City,Suzhou,this paper analyzed the influent quality and operation status of the combined sewage treatment plant in Jinfeng District of Zhangjiagang City in rainy season,and optimized the operation parameters of the improved AA/O process in rainy season.Through the analysis,it was concluded that there were many operational problems in the combined sewage treatment plant during the rainy season: first,the carbon source of nitrogen and phosphorus removal was insufficient;second,the hydraulic impact load was too large;third,the biological foam and activated sludge bulged;fourth,the influent DO was too high,affecting the release of phosphorus and denitrification.According to the characteristics of water quality and quantity of influent in rainy season,the energy consumption and drug consumption during the operation of improved AA/O process could be reduced by adjusting several key operating parameters(sludge recycling ratio,internal recycling ratio,dissolved oxygen concentration)in the improved AA/O process,and the ability of resisting water quality and water impact load could be improved.Taking pollutant removal efficiency and energy saving and consumption reduction as comprehensive evaluation indexes,the optimum operation parameters of improved AA/O process with increasing water volume in rainy season were as follows: internal circulation ratio 100%~200%,sludge circulation ratio 60%~80%,DO concentration 2.0 mg/L~3.0 mg/L,and adding a certain amount of carbon source under low carbon-nitrogen ratio.Applying the best operation parameters to the future regulation and control operation of Jinfeng sewage treatment plant in rainy season can improve the treatment capacity of the combined sewage treatment plant in rainy season,and further weaken the pollution degree of the receiving water body in rainy season,and save energy consumption and drug consumption.