Simulation And Optimization Of MBBR Process Based On ASM2d

By adding a certain amount of carriers to the reaction tank, the MBBR process forms the suspended activated sludge and the attached biofilm, and the concentration of nitrifying bacteria in the system is increased and the nitrogen removal effect is enhanced.As the national nitrogen and phosphorus standards improved and sewage treatment plant to seek a effective way of upgrading,the MBBR process is gradually applied to the upgrading of sewage treatment plant.In this paper, ASM2d model is used to simulate the MBBR process of the fourth sewage treatment plant in Xi’an and to optimization of nitrogen and phosphorus removal process,then, the MBBR process optimization control scheme is proposed, and the feasibility of the optimization scheme is verified by numerical simulation.Simulation results and actual operation deviation was found by modeling and Simulation of MBBR process.Because the sewage treatment plant is affected by the influent water quality and the regional environment and the biochemical reaction environment of microorganism is different,parameter range is large. The influent components and parameters of the model need to be measured according to the actual situation of the water treatment plant.Through the sensitivity analysis, the influence of different parameters on the output of the model was understand, then the parameters which have great influence on the model output was selected.The kinetic parameters with large susceptibility are heterotrophic decay rate constant bH, maximum growth rate of autotrophic bacteria μAUT, maximum growth rate of heterotrophic bacteria μH;Stoichiometric parameters with high sensitivity are heterotrophic bacteria yield coefficient YH and autotrophic bacteria yield coefficient YAUT; In sensitivity analysis of influent components,Si has a great influence on component of COD ,influent component SNH4 has a great influence on ammonia nitrogen and TN,Xs has some influence on ammonia nitrogen and TN,fermentation product SA and influent SPO4 had a greater impact on total phosphorus.In the determination of influent components and parameters,the measured values of YH、bH、μH、μA were 0.684、0.415d-1、5.100d-1、0.708d-1 by the way of intermittent OUR method.YA is relatively stable in activated sludge,using the theoretical value 0.24 asYA.Currently,there is no effective method to determine bA,using recommended value of ASM2d model 0.15d-1 as bA.In the determination of influent components,the average values of SF、SA、SI、XS、XI、XH were 51.8mg/L、35.8mg/L、28.9mg/L、204mg/L、41.0mg/L、32.4mg/L,accounting for the proportion of COD were 13%、9%、7%、52%、10%、8%.,There is a difference of influent components between the sewage treatment plant and the others , which indicates that the water quality is related to the nature and sources of sewage.The model is calibrated,then the effects of system aeration (DO), mixed liquor recirculation ratio (R), sludge recycle ratio (R), filling ratio (PR), and temperature on the process were analyzed. The optimal control scheme is proposed,which DO was controlled in the range of 2.0～2.5mg/L, R was in the range of 150%～200%, R was 60%, PR was 20%,in the high temperature season, and DO was 2.5～3.0mg/L, R was 150%～200%, R was 80%, PR was 25%,in low temperature season.If the nitrogen removal effect is not ideal in the process of operation,the first consideration is to increase the R ,followed by increasing DO;If the process of removing phosphorus is not ideal, the priority regulation r in a reasonable range, and secondly,a reasonable control DO.While both considering the denitrification and phosphorus removal,the comprehensive control of r and DO, then consider other parameters.