Optimization And Simulation Of AOAO-MBR Biological Denitrification Process

At present,many urban sewage treatment plants have been rebuilt,and the effluent has been upgraded to the Class A standard,and some water plants have advanced to Class IV standards for surface water.Under the condition of low water C/N,how to further optimize the process and complete the deep treatment of total nitrogen has become a research hotspot.In this paper,the AOAO-MBR biological nitrogen removal process was studied,and Biowin software was used for simulation simulation to provide suggestions and verification for further optimization of the process,and to provide technical support for meeting the high emission standards of surface water class IV.The main conclusions are as follows:?1?Exploring the operation effect of AOAO process under different carbon-nitrogen ratio?C/N?,nitrifying liquid reflux ratio?IR?and sludge reflux ratio?r?.Under the condition of chemical oxygen demand?COD?average water intake of 195.0mgL,ammonia nitrogen?NH₄⁺-N?average influent water of 21.3mg/L,and total nitrogen?TN?average influent of water of 32.7mg/L,the staged water inlet ratio is determined to be 6:4.The C/N has the best working condition under the condition of 6:1,internal reflux ratio of200%and external reflux ratio of 50%.The average effluent of COD,NH₄⁺-N and TN were 17.1mg/L,0.8mg/L and 13.6mg/L,respectively,and the removal efficiencys were91.21%,96.23%and 58.61%,respectively.The effluent could be stabilized to the first-class A standard.?2?After increasing the MBR membrane module,the sludge concentration is about4600mg/L,the average COD water inflow is 195.4mgL,the ammonia nitrogen influx is21.2mg/L,and the total nitrogen influent is 30.9mg/L.The final COD effluent of the system is 12.3mg/L,removal efficiency 93.69%;ammonia nitrogen average effluent0.5mg/L,removal efficiency 97.82%;total nitrogen average effluent 10.2mg/L,removal efficiency 66.88%.The effluent range of total nitrogen fluctuated from 8.5mg/L to 12.1mg/L,and the effluent could not be stabilized to the surface water class IV standard.?3?The AOAO-MBR process was modeled and optimized by Biowin software.The optimal operating parameters were:the DO control in the MBR reaction tank was 1.2mg/L,the stepwise water inlet ratio was 6:4,and the internal reflux ratio was 200%.The optimization experiment was carried out for demonstration experiments.The average COD of effluent was 12.8mg/L,the average ammonia nitrogen was 0.4mg/L,the average TN was 9.4mg/L,and the effluent was stable to the surface water category IV emission standard.