Simulation And Optimization Of Typical Activated Sludge Process Operation Based On ASM Model

With the development of society and economy,the discharge of industrial wastewater and domestic sewage in our country are increasing,the discharge standards are becoming stricter,and the sewage treatment pressures faced by major sewage treatment plants are also increasing.In order to meet national sewage discharge standards and improve emergency response treatment capacity,reducing the concentration of effluent pollutants,and saving operating management costs are the common goals of major sewage treatment plants.Establishing the activated sludge model of the sewage treatment plant can provide theoretical suggestions and transformation schemes for the optimal operation of the sewage treatment plant,and it has more reference value and timeliness.In this paper,the improved A2 O process of a large sewage plant in Chongqing is taken as the research object.The concentration and proportion of each dissolved and particulate component in the COD influent of the sewage plant are measured and analyzed.Based on the MIKE WEST software platform,the ASM2D(Activated sludge model 2D)model theory,the whole process simulation of this sewage plant was carried out.After the model was determined to be credible according to the evaluation index,the corrected model was used to explore the water intake ratio of the selection pool,the water intake ratio of the three series of hypoxic pools,The influence of the five influencing factors of reflux ratio,external reflux ratio,and DO on the treatment effect of the improved A2 O process of the wastewater treatment plant is proposed.A parameter optimization scheme library strategy is proposed to provide theoretical guidance for the management and decision-making of the wastewater treatment plant.First,the influent components of the sewage plant were determined experimentally.SS(easily biodegradable organic matter)and XS(slow degradable matrix)were measured by intermittent OUR(active sludge respiration rate)method,and determined by gas chromatography.SA(fermentation product),SI(inert dissolved organic matter)measured by flocculation precipitation method,SF(fermentable and easily biodegradable organic matter)is obtained from the material conservation formula SF = SS-SA,and material conservation formula XI = total COD-SA-SF-SI-XS yields XI(inert particulate organic matter),and the measured SA,SF,SI,XS,XS,and XI components account for 11.95%,15.88%,43.12%,6.18%,19.56 % As input data for the next step of modeling the sewage plant.The operation conditions of the sewage plant were investigated on site,and basic information of the sewage plant was obtained.There are mainly structure size information,internal and external reflux ratio information,phosphorus removal and dosage information,and aeration information.Obtained the water inflow data and experimental report data from October 1,2018 to December 31,2018.The measured water inflow component ratio data and the historical system data and basic operating parameters of the online system obtained from the sewage plant survey were used at MIKE.The WEST software platform builds an ASM2 D model of the improved A2 O process of the sewage plant.After the initial simulation,sensitivity analysis of 20 related parameters in the model shows that the five parameters that have the greatest influence on the effluent index are YH(heterotrophic bacteria yield coefficient).),QPP(rate constant of particulate phosphorus storage),μPAO(maximum growth rate of polyphosphate bacteria),YPAO(polyphosphate growth factor),μH(maximum growth rate of heterotrophic bacteria).After calibrating the parameters,comparing the re-simulated effluent results with the actual effluent results of the sewage plant,the relative error was reduced by about 10%,which improved the accuracy of the model and the actual match of the sewage plant.The model is then evaluated according to relevant evaluation criteria,and the credibility of the model is obtained.The results show that the simulation of COD and TP works well,and the simulation of ammonia nitrogen and TN is qualified.The model can be used for subsequent offline or online use of the sewage plant.The corrected model was used to simulate the internal reflux ratio,external reflux ratio of the sewage plant,the water intake ratio of the three series of anoxic ponds,the water intake of the selected pool,the carbon source addition,and the DO concentration at the end of the three series of aerobic ponds against the water output.Among the many parameters,it was found that the internal reflux ratio,the external reflux ratio,and the DO concentration at the end of the aerobic tank had a significant effect on the effluent result.The external reflux ratio and the end of the aerobic tank had the most significant effect on the effluent result.The waste caused by gas energy consumption is relatively obvious.It provides a reference for the selection of those parameters as the optimization object in the pre-plan library,and also provides suggestions for the operation of the sewage plant and the process;In view of the problems existing in the current online model,an optimization strategy library is proposed.Based on the concentration range of the influent pollutants of the sewage plant,20 influent conditions with different gradient combinations of influent indicators are established.The constant water inflow is constant.The external reflux ratio and the front-end aerobic tank DO are not changed.Using the parameters in the model to estimate advanced experimental functions,the effluent reaches the first-level A standard and the lowest energy consumption is the objective function.The optimal external reflux ratio parameters of the water intake conditions and the DO concentration parameter of the last aerobic pond have derived the formula for the operation strategy when the water quality fluctuates,which provides a new idea for smart water services.