Simulation And Optimization Of Modified A~2/O Process Based On ASM2D Model

With the development of the national economy and the enhancement of people’s living standard,the state put forward higher requirements for sewage treatment plants.To enhance the emergency capacity of wastewater treatment plants,reduce effluent pollutant concentration and save operation cost has become the goal of wastewater treatment plant optimization.The sewage treatment process model based on activated sludge model can effectively simulate the operation of the process.In view of the existing problems of the sewage plant,the reform scheme can be quickly put forward and its operating parameters are optimized.Based on the modified A2/O process of a sewage plant in Guangzhou,this paper uses the method of combining experimental research and computer simulation to determine the content of COD components in the influent,single factor and multi factor analysis of the effect of six control parameters on the modified A2/O process effect by analyzing the six control parameters of influent distribution ratios of pre-denitrification tank,reflux ratio of nitrifying liquid,reflux ratio of sludge,DO,SRT and HRT.The main contents and conclusions of this paper are as follows:(1)The content of COD components in the influent of a sewage plant in Guangzhou for 12 months from October 2016 to October 2017 was measured.SS,XS and XH were measured by intermittent OUR method.SI and distillation were measured by flocculation filtration method and SA was detected by distillation.SF and XI were calculated by SF=SS-SA and XI=COD-SS-XS-SI-XH.The concentrations of influent SI,SS,XS,SA,SF and XH were 11.8 mg/L~62.1 mg/L,10.73 mg/L~41.98 mg/L,22.97mg/L~98.98 mg/L,4.6 mg/L~22.5 mg/L,4.59mg/L~22.86 mg/L,13.58mg/L~119.39mg/L.(2)Based on the ASM2 D model,the modified A2/O process model was constructed by using WEST software platform.By the sensitivity analysis of the stoichiometric parameters and dynamic parameters,the relative error between the simulated results of the effluent COD,ammonia nitrogen,TN and TP is smaller than 5%,and the model and the actual conditions were reached the greatest agreement.(3)Based on the modified A2/O process model,the effects of six technological parameters on effluent COD,ammonia nitrogen,TN and TP were analyzed by single factor analysis.Then the single factor analysis results were used to select the suitable range of parameters for multi factor orthogonal analysis.The results showed that when HRT,influent distribution ratios of pre-denitrification tank,DO,SRT,sludge reflux ratio and mixing liquid reflux ratio were 10 h,50%,1.8mg/L,11 d,40%,50% respectively,the lowest TP concentration in the effluent was 0.42 mg/L,and the effluent quality reached the first order A standard,and the operation condition of the process reached the best state.(4)When the improved A2/O process operates under the optimal operating conditions,the plant can reduce the cost about 2 million 700 thousand yuan,the aeration cost about 3 million 400 thousand yuan,the cost of sludge reflux about 1 million 600 thousand yuan,the reflux cost of mixed liquid about 1 million 700 thousand yuan,20 thousand yuan for the removal of excess sludge and about 9 million 400 thousand yuan in total operation cost.