Simulation And Optimization Of A/A/O Process Based On BioWin

Water environment is closely related to the survival of human beings,and sewage treatment is an important part of the protection of water environment.In recent years,more stringent effluent standards have been put forward for WWTPs.Many traditional WWTPs seek for renovation measures.However,debugging according to experience is not only associated with risks,but also time-consuming.Therefore,research was carried out to solve the problems of improving effluent quality and saving energy consumption in WWTPs.A/A/O process of a WWTP in wuhan was taken as the research object.Aiming at the problem of unstable denitrification effect and high aeration energy consumption,Bio Win6.0 was used to establish the kinetic activated sludge model for A/A/O process of the WWTP.The physical and chemical methods were used to determine the influent quality of the WWTP,and the values of partial influent components were calculated as follows:Fbs=0.2008,Fac=0.3497,Fus=0.0309,Fup=0.2185,Fna=0.8287 and Fnox=0.5674.The steady state and dynamic calibration of the model was carried out with the measured data,and the dynamic verification of the model was carried out with the actual operation data after changing the working conditions,and the model with good prediction ability was finally obtained.By adjusting the parameters such as influent ratio,sludge reflux ratio,dissolved oxygen,sludge discharge volume and reflux ratio of nitrifying liquid,the influence law of each parameter change on effluent quality was analyzed,and the results showed that the optimal value range of each parameter was 5-15%,50-65%,1.5-3mg/L,550m³/d and100-300%respectively.Through the optimization and simulation of the dosing process,the optimal dosing scheme of carbon source and the optimal dosing quantity of chemical phosphorus removal were put forward,which can greatly improve the qualified rate of effluent quality.By optimizing the aeration system,based on the current aeration strategy,a cascade control strategy based on feedforward of influent NH₃-N and feedback of DO in aerobic tank was established.The control effect was simulated by BW Controller.The simulation results showed that the new aeration control strategy not only reduced the total aeration by 20.58%,but also increased the qualified rate of TN by 7.84%.Response surface method was used to establish the functional relationship between TN effluent concentration and sludge reflux ratio,reflux ratio of nitrifying liquid and dissolved oxygen in aerobic tank.The optimal operation strategy of the WWTP was worked out,that is,the reflux ratio of nitrifying liquid was adjusted to 300%,the sludge reflux ratio was adjusted to 50%.The dissolved oxygen in aerobic tank was controlled to be less than 3mg/L,the aerator at the reflux of nitrifying liquid in the aerobic tank was closed,and the dissolved oxygen was controlled to be less than 0.5mg/L.The carbon source adding device was added in the anoxic tank,and the average adding amount was90kg COD/d.The dosage of chemical phosphorus removal was optimized and the average dosage of PAC was about 31.6kg/d.After 60 days of actual operation in the WWTP,the data showed that the qualified rate of each parameter effluent was 100%.Compared with the data before optimization,the average concentration of TN,the average dosage of PAC and the average concentration of DO in aerobic tank were decreased by 14.5%,54.9% and 41.3%,respectively.