Study On The Parameter Estimation Of ASM3Based On Genetic Algorithm

In view of the serious water pollution, water shortages,low level of the operation andmanagement of sewage treatment plant,low and poor operation stablity and automation.it’simperative to optimize the operation of sewage treatment plant.this article based on WESTsoftware plantform,and construct a reasonable process model of the sewage treatmentplant,then go on with parameter estimation using MATLAB based on geneticalgorithm.through model simulation,parameter estimation can effectively improve thefitting of model and provide a theoretical reference for the process running and automationcontrol.This topic base on ASM3launched by IWA,it focuses on nitrogen removal and carbonprocess of activated sludge system,combined with the actual operating conditions of theWuzhong District,suzhou City Sewage Treatment Plant Phase II Carrousel oxidation ditchprocess,construct a process model based on WEST,then go on with parameter estimationand simulation tests.According to the water quality and the process of the research object, puts forward athought that it’s appropriate to omit some component or process to simplify themodel.According to the process characteristics of Carrousel oxidation ditch and measuredDO variation characteristics, WEST model is built with the15CSTRs in the same volumeto express the oxidation ditch process.It’s necessary to set up structures physical parameters,characteristic parameters,operation parameters and model parameters of the process model of sewage treatmentplant.under these conditions,inplement the steady state simulation,analysis simulationvalues and measured values.The next step is sensitivity analysis, the main analysis object including stoichiometrycoefficient, component and dynamic parameters,using the perturbation analysis method,changing the parameters in accordance with the amplitude by10%, the sensitivity of eachparameter to each kind of model components can be calculated by calculation formula.The sensitivity anslysis can reduce the workload and save time for parameterestimation,this study selected four kinetic parameters, based on genetic algorithm and leastsquare principle, using MATLAB program, then obtained the estimated value of a set ofoptimal parameters. In order to test whether the parameter estimation results can effectively improve themodel fitting degree, implement the steady-state and dynamic simulation in the defaultparameters and estimation parameters conditions, comparative analysis of COD, TSS,ammonia nitrogen and TN.The conclusions are achieved as follows:(1)The CSTR series model can effectively express the Carrousel oxidation ditchprocess reaction system, and the method of omitting part components or process tosimplify model is feasible;(2) The steady state simulation was carried out after the model built complete,bycomparing simulated results and measured results of effluent COD,TSS,ammonia nitrogenand TN, the absolute error and relative error is14mg/L,0.12mg/L,1.33mg/L,0.1mg/L and39%,7.1%,20.5%,1.2%respectively.simulation results show that the construction of theprocess model is feasible sence the error is acceptable,and the method of the modelbuilding is also suitable for domestic wastewater treatment plant.(3)The sensitivity analysis results shows that:simulation of ammonia nitrogensensitive to μA, KA,NH, bA,O2, YH_O2, YSTO_O2; simulation of nitrate nitrogen sensitive to μA,ηNO,bA,O2,YSTO_NO,YH_NO;simulation of TN sensitive to bSTO,NO,KA,NH,ηNO,KO,YSTO_NO,YH_NO,this study selected μA,KA,NH,bA,O2,kA,O2as the objects of the parameter estimation.(4)According to the sensitivity analysis of parameters, selected four kineticparameters and carried out parameter estimation using MATLAB program and geneticalgorithm, the results shows that:μA=1.1192d-1,KA,NH=0.9027gN/m3,kA,O2=0.6081gO2/m3,bA,O2=0.1625d-1.(5)Carried out the steady-state and dynamic simulation using the default parametersand estimation parameters,the results show that the fitting degree is higher underestimation parameters than under the condition of default parameters.especially obvious inthe effect of ammonia nitrogen and TN.therefore the proposed method of parameterestimation can effectively improve the effort of simulation.