Research On Optimization Of Two-step Feed Three-stage A/O-Moving Bed Biofilm Reactor System

As China pays more and more attention to the quality of the water environment,and the requirements for sewage discharge are becoming higher and higher,accelerating the construction of urban sewage treatment infrastructure has become an important measure to improve the quality of urban water bodies at this stage.However,the sewage treatment plant still faces many problems in actual operation,such as low nitrogen removal efficiency,high operating cost,unstable treatment effect,etc.Especially in the northern region,how to achieve stable and efficient treatment under low temperature conditions in winter has become a problem that the sewage treatment industry needs to solve urgently.Therefore,in order to solve the technical problem of high-efficiency nitrogen removal for low-temperature sewage treatment in cities and towns,this study constructed a pilot-scale two-step influent three-stage A/O-MBBR system,Use the advantages of multi-segment A/O and MBBR technologies to solve this technical problem.During the study,the effect of the system on the removal of various pollutants in different temperatures and different water quality environments was investigated,The effect of the layout of the reactor(two-stage A/O-MBBR sub-systems in series,the anoxic zone and the aerobic zone are divided into two reactor arrangements)on the removal capacity of the system was explored,The effects of different operating conditions(temperature,BFCOD removal load,nitrification load,BFCOD concentration,nitrate concentration)on the denitrification capacity of each reactor in the two-step influent three-stage A/O-MBBR system were analyzed,The range of boundary conditions(nitrification load,BFCOD concentration)for the system to achieve efficient nitrogen removal under various temperature conditions is proposed,Provide technical support for the construction and optimization of multi-stage A/O-MBBR system for multi-stage influent of nitrogen removal in urban sewage treatment.The main findings are as follows:(1)Taking hotel domestic sewage as the treatment object,under the conditions of reaction temperature 12?15?,pilot system HRT is 7 h,A9 reactor plus 60 mg COD/L sodium acetate,A5 reactor plus 50 mg COD/L sodium acetate,the removal rates of COD,ammonia nitrogen and TIN can reach 81.58±6.94%?99.42±2.91%?89.65±4.53%,respectively.Taking urban domestic sewage as the treatment object,under the conditions of reaction temperature 13?16?,system HRT is 17.5 h,and A9 reactor plus 40 mg COD/L sodium acetate,the removal rates of COD,ammonia nitrogen and TIN can reach 91.19±3.89%?99.10±1.22%?68.16±9.99%,respectively.(2)Compared with the two-stage A/O-MBBR sub-system parallel arrangement,the two-stage A/O-MBBR sub-system connected in series can improve the removal capacity of SCOD,ammonia nitrogen and TIN of the second-stage A/O-MBBR sub-system at each temperature(6?15?).And it can improve the removal capacity of SCOD and ammonia nitrogen in the second-level A/O-MBBR sub-system under each load.The lower the temperature and the higher the system volume load,the more the nitrogen removal capacity of the second-level A/O-MBBR sub-system is improved by adopting the two-level A/O-MBBR sub-system in series arrangement.In addition,the two-stage A/O-MBBR sub-system is connected in series to enhance the simultaneous nitrification and denitrification process,low temperature resistance and impact load resistance of the second-stage A/O-MBBR sub-system.(3)Under the reaction temperature of 6?15?,The system COD volume load is 497.33±157.73 g COD/(m3·d),the system organic volume load is 353.83±121.11 g SCOD/(m3·d),and the system ammonia nitrogen volume load is 106.92±30.71gNH4+-N/(m3·d),The nitrification removal load of the O3 reactor is mainly affected by the BFCOD removal load,and the nitrification removal load of the O4,O7,O8,O10 reactors is mainly affected by the nitrification load.The nitrification load of each aerobic reactor to achieve the best nitrification effect is different at different temperatures.In actual operation,the aerobic reactor can be controlled to be in the optimal nitrification by adjusting the proportion of the two sections of inlet water flow rate,reactor volume,DO concentration,to achieve the best nitrification load.When the temperature is 12?15?,the optimal BFCOD concentration of A1 reactor is 37.5 mg/L;when the temperature is 9?12? and 12?15?,the optimal BFCOD concentration of A5 reactor is 35 mg/L and 22.5 mg/L respectively.The sum of the concentration of the external carbon source in the two reactors and the original BFCOD concentration in the reactor should not exceed the optimal BFCOD concentration.(4)In actual operation,it can be considered to reduce the volume of the O4 and O8 reactors(the filling rate is unchanged)to increase the nitrification load to enhance the ammonia nitrogen removal capacity of the two reactors;When the concentration of ammonia nitrogen in the inlet of the O10 reactor is less than 2 mg/L,the aeration in the reactor should be reduced to reduce energy consumption;When the low matrix concentration leads to poor denitrification effect in A2 and A6 anoxic reactors,you can consider reducing A2 and A6 The reactor volume even eliminates these two reactors.