Control And Optimization Of Operating Parameters Of A~2/O Process And CAST Process Domestic Sewage Treatment Plant In Low Temperature Period

Focus on solving obviously environmental problems and build a beautiful China are hotspots of concern to the whole nation.In order to meet the growing demand for a high-quality environment of the people,the country has gradually improved environmental protection standards.It is an important task for the sewage plants to accelerate the prevention and control of water pollution and to cope with the improvement of the emission standards.How to ensure that the output index of water meet the standards and realize the stable operation of the sewage treatment plants in cold area is an important subject worth studying.This paper is based on data collected from two sewage treatment plants operated by Longjiang Environmental Protection Group,and it analyzes low-temperature operation conditions of A~2/O and CAST processes commonly used in waste water treatment plants in cold regions.Annual operating data of the A~2/O and CAST process were collected to analyze and grasp the operation status of the conventional process.The key point was detecting the temperature effect on the efficiency of pollutants remove process,identifying key parameters and summarizing rules.The low-temperature process could optimize and regulate the operating parameters and provide operational experience and technical support for the conventional process of sewage treatment plants in cold regions.Taiping Wenchang waste water treatment plant worked well throughout the year and the removal effect of low temperature COD,BOD and total phosphorus remained stable,only ammonia nitrogen and total nitrogen removal efficiency and decreased during the low temperature period.The result demonstrated that temperature is a limiting factor of A~2/O nitrogen removal process.The CAST process of Zhaodong city wastewater treatment plant was running well throughout the whole year.The removal efficiency of COD,BOD,ammonia nitrogen and total phosphorus were basically stable during the low temperature period.Only the total nitrogen removal was seriously affected by temperature which decreased at low temperature.The result demonstrated that temperature is the limiting factor of nitrogen removal in CAST process.According to the annual data analysis,in view of the improvement of nitrogen removal efficiency and the optimization of process parameters through production test,this paper puts forward the control strategy of cold season's operation parameters.Among them,through the optimization of the three parameters of sludge age,mixture internal reflux ratio and sludge return ratio,the ammonia nitrogen removal rate of the A~2/O process during the low temperature period increased by 15%,and the ammonia concentration of the effluent water was stable and reached Class A standard.In three indicators,prolonged sludge age on the removal of ammonia A~2/O process has obvious effect,mixed the liquid reflux ratio and reflux ratio of sludge on ammonia nitrogen removal effect was not obvious;through the optimization of the three parameters,the total nitrogen removal rate increased by 25%,the effluent total nitrogen concentration and reached a stable level of A standard.Sludge age,recycle ratio and sludge return ratio had a significant effect of removal the total nitrogen of the A~2/O process.Through the parameters optimization of the sludge concentration,DO value and sludge return ratio that the total nitrogen removal rate of CAST process at low temperature increased by 13%,the effluent total nitrogen concentration and reacheed a stable level of A.The effect of sludge concentration,sludge reflux ratio DO value and three parameters on total nitrogen removal were significant.Through data analysis,the change of removal efficiency A~2/O process and CAST process in cold areas were mastered.The efficiency of nitrogen removal was obviously affected by the low temperature factors in the cold area,and the other parameters were basically stable,which indicated that the temperature was the limiting factor of the nitrogen removal in the cold regions A~2/O process and the CAST process wastewater treatment plant.By controlling and optimizing the process parameters at low temperature stage,the nitrogen removal efficiency of A~2/O process and CAST process in cold area have been significantly improved at low temperature stage,providing data support for the stable operation of sewage treatment plants in cold regions.