Activated Sludge Model Parameters Calibration Based On Multi-objective Particle Swarm Optimization

Many scholars domestic and abroad have spend a lot of research in activated sludge ma-thematical model since its launch, which greatly promoted the series model application in the wastewater treatment process of activated sludge system. The wide application of activated sludge process around the world also promoted the further development of the mathematical model.Due to the differences in water quality conditions in different regions, a series of acti-vated sludge model simulation of actual working condition need the specific environment pa-rameter correction, in order to improve the accuracy of simulation. Based on a sewage treat-ment plant of Orbal oxidation ditch process, this article uses the ASM3model to simulate the internal chemical reaction of biochemical reaction tank, Takacs double index sedimentation rate model to simulate the internal physical settlement process of the second pond, and link the two together, setting up integrated model of sewage treatment process.According to the monitoring data of influent and effluent, the conventional concentration monitoring indicators were transfered into the model component concentration through mea-surement and statistical analysis. Using the recommended parameters value given by interna-tional water quality association, steady state simulation and dynamic simulation were ex-ecuted. The results show that the effluent error of target COD and SNH is bigger, the error of the target TN is relatively small, but still need to correction parameters.Treat the three error of water indicators as target for multi-objective correction. But due to the possible conflict each other between the optimization direction of COD TN and SNH, there is no absolute individual history optimal and global optimal, making directly using the PSO to the multi-objective impossible. Aiming at this problem, this article combined the ran-dom selection strategy of individual history optimal, and under the background of mul-ti-objective problem, selected a global optimal for each particle from the noninferior set crea-tively, mixed with particles elimination mechanism based on grid, in order to obtain the final solution of uniform distribution and diversity richness.To analyze the sensitivity of the parameters in the model, select larger sensitivity para-meters (KH,bH,O2,bH,NO,μA,KA,NH,KA,O,bA,O2,fSI,YSTO,O2,YSTO,NO,YH,O2,YA) for parameter calibration.Using parameter value after correction for dynamic simulation again, the target values of effluent error reduce further contrast to the default parameters, increase the applica- bility of the model in the current environment, so as to promote the development of model re-search, improve the efficiency of wastewater treatment.