Experimental Study On MBBR-A~2/O Process For Treatment Of Urban Domestic Sewage

China's urbanization has developed rapidly in recent years,but problems such as difficulties in handling domestic sewage still exist in remote urban areas.To better solve this problem,this experiment intends to use the most widely used anaerobic-anoxic-aerobic?A²/O?wastewater treatment system in the field of wastewater treatment as the research object.There are many different contradictions such as carbon source competition and sludge age in a single A²/O treatment system.It is difficult to achieve simultaneous and efficient nitrogen and phosphorus removal in urban sewage treatment.Therefore,in order to ensure that the urban sewage problem can be effectively solved,this test is to combine traditional biological treatment systems by adding fiber-type combined fillers to the anaerobic,anoxic,and aerobic tanks with a volume filling rate of 30%.The combined activated sludge method and biofilm method form a new system that can efficiently remove nitrogen and phosphorus.The existence of biofilm on the filler surface can effectively provide a living environment for different bacteria groups,making the composite system more efficient in removing nitrogen and phosphorus..This experiment is to optimize the allocation of the MBBR-A²/O process mixture?inside?reflux ratio,sludge?outside?reflux ratio,dissolved oxygen concentration?DO?,and sludge age?SRT?,and scientifically add polymer aluminum.To achieve stable and efficient operation of the system,to ensure the efficient removal of COD,NH₄⁺-N,TN,TP in urban domestic sewage.The MBBR-A²/O system has successfully started the stable and efficient operation of the MBBR-A²/O system after 30 days of startup and adjustment of the film hanging stage.The system has a good effect of removing various pollutants.COD,NH₄⁺-N,TN,The average removal rates of TP were 90.23%,87.56%,66.72%and 65.51%.The sludge concentration of each reaction tank in the MBBR-A²/O system was basically maintained between 2500 and 3200 mg/L.The research results show that when the reflux ratio of the mixed liquid is 150%,200%,250%,and 300%,the COD effluent effect is stable,but it has a significant effect on the nitrogen and phosphorus removal of the A²/O system.During the gradual increase of 250%,the nitrogen removal efficiency of the system gradually increased,and the average removal rate of TN increased from 55.2%of the mixed liquid?internal?reflux ratio to 150%to 71.76%of the mixed liquid?internal?reflux ratio.However,increasing the reflux ratio of the mixed liquid?internal?did not further improve the denitrification effect;the DO of the aerobic tank was adjusted to stabilize the reactor.When the DO was 3 mg/L,the average removal rate of NH4⁺-N was 97.21%.The effluent concentration is 0.69mg/L;different sludge reflux ratio conditions have a greater impact on the N and P effluent of the A²/O system.When the sludge reflux ratio is 60%,the average removal rates of TN and TP are 69%.70.7%,when the sludge reflux ratio is 100%,the TN removal rate increased to 78%,and the TP removal rate decreased to 61.56%;under different sludge age conditions,the TP effluent of the A²/O system The concentration fluctuates greatly.When the SRT is 12d,15d,and 18d,the TP removal rates are 71.24%,68.34%,and 54.53%,respectively.The COD and NH₄⁺-N fluctuate.Smaller,when the SRT is 12d,the effluent concentrations are 16.01mg/L and 1.87mg/L,respectively.Adding polyaluminum-iron at the front of the aerobic tank is not conducive to the efficient and stable nitrogen and phosphorus removal of the MBBR-A²/O system.At the same time,the effect of COD removal is also deteriorating with the increase of the dosage.When the dosage is 4mg/L,the minimum TP effluent concentration is 0.68mg/L,and the removal rate reaches 87.14%,which meets the national level B standard.Adding polyaluminum-iron at the end of the aerobic tank has a small effect on the microbial activity in the MBBR-A²/O system.When the dosage is 4mg/L,the phosphorus removal effect is the best.The average removal rate of TP reached 95.14%,reaching Grade A standard.