Research On Construction And Coupling Of Municipal Sewage Treatment Plant Model For Control Mode Optimization

With great seasonal variations of influent loads in typical municipal wastewater treatment plant?WWTP?,WWTPs were under extensive experience controlling mode for a long time,which led to high effluent pollutant concentrations and high energy consumption.The anaerobic tank+oxidation ditch process in a Suzhou WWTP was studied in this paper.By analyzing influent and process characteristics,biological treatment process model was built.Meanwhile,modeling key points applied to typical municipal wastewater treatment plant were summarized.The effect of operational parameters on effluent concentrations was analyzed with simulation method.The critical point of stable operation and energy saving was diagnosed.In order to achieve the stable low effluent concentrations and low energy consumption,optimization scheme of oxidation ditch in the dry weather was proposed at last.Error in discharged sludge and returned sludge flow was identified and adjusted with overlapped material balance in building oxidation ditch model.The relationship between aeration discs opened quantity and the velocity in the oxidation ditch was established to reflect the hydraulic transmission characteristics reasonably.These practices improved the accuracy of operational parameters as the boundary condition of model.For the wastewater treatment plant with large historical data,to optimize the annual operational control mode of sewage treatment plant,calibration was taken with the data of different water temperature interval during the whole historical year,main effluent quality and change trend of pollutants along biological treatment zone were compared.Verification was taken with another set of historical year data.Thus reliable calibration results could be obtained.For the problem of low effluent NH₄⁺-N,high effluent TN and high energy consumption caused by experienced control mode,model was applied.According to the dynamic relationship between influent,effluent and process variables,two goals of effluent quality reaching the standard stably and consumption reduction were realized.Simulation and operation results showed,after optimization strategy was applied,effluent COD,NH₄⁺-N,TN and TSS achieved discharge standard stably,the rate of reaching the standard for TP was improved.Power consumption per ton water decreased by about 29.4%,load consumption decreased by 22.5%compared with the same period last year.To reduce the pollution of receiving water body caused by rainfall runoff,meanwhile to maximize the treatment potential of the WWTP,WWTP model and non-point source pollution model was combined to study the dynamic change of influent quality and quantity of WWTP and its influence on the biological treatment process under rainfall conditions.Results showed,key point to coupling the non-point source pollution model with the WWTP model was the characterization of influent quality.Rainfall runoff changed composition of influent,resulting in the reduction of biodegradable components and the increasing of granular components.Finally,the operation strategy of sewage treatment plant under wet weather condition was optimized from inflow,sludge return flow and aeration capacity.