Study On Treatment Of Domestic Sewage By Bubbleless Filled Oxygen Membrane Bioreactor

Bubbleless aerated membrane bioreactor（MABR）is a new type of wastewater treatment technology with wide application prospects.It uses hollow fiber membrane to aerate water,and as the attachment medium of microorganisms,microorganisms are used to biochemical treatment of carbon,nitrogen and phosphorus pollutants in water.The MABR process has many advantages,such as high efficiency,energy saving and small space occupation,due to its characteristics of bubbleless oxygen charging,oxygen and substrate heterotransmission,and microbial membrane structure stratification.In this paper,the treatment effect of MABR system on domestic sewage was studied,and the removal of carbon,nitrogen and phosphorus pollutants in domestic sewage under different working conditions was systematically investigated.A new membrane bioreactor was designed to make the flow uniformly distributed and the flow direction cross-flow with hollow fiber membrane.Three parts of operation tests were carried out,and the following conclusions were obtained:1.The characteristics of aeration of hollow fiber filament were studied.The bubbleless aeration membrane bioreactor uses hollow fiber membrane filament to aerate,and its bubble point is（0.0368±4.5E-4）MPa.Compared with traditional bubble aeration,the oxygen volumetric mass transfer coefficients（K_Lα）of the two methods are 0.5592h^-1 and 0.0641h^-1.The bubbleless aeration is about 8.7 times of the traditional bubble aeration,and the bubbleless aeration has high efficiency.In a certain suitable range,the higher the oxygen pressure,the higher the flow velocity and the deeper the water depth,the better the oxygen filling effect of the membrane filament to the water.2.Study on the treatment of domestic sewage by bubbleless aeration reactor:Taking domestic sewage with low C/N ratio as the test object,the start-up of the reactor was tracked.The effects of hydraulic retention time（HRT）,flow rate,aeration time,temperature,organic loading of influent water and ammonia-nitrogen loading on the removal efficiency of the reactor were investigated,and the process parameters were optimized.The results showed that:（1）MABR system was activated by inoculating activated sludge,and the microorganisms were domesticated successfully after 30 days of biofilm hanging;（2）when HRT was 24 hours,flow rate was 0.068 m/s,water temperature was 18-36℃,dissolved oxygen（DO）was 1.38（±0.2 mg/L）,the reactor had good treatment effect;the average removal rates of COD_Cr,NH₄⁺-N,total nitrogen and total phosphorus were 85.30%,65.60%,48.20%and 25.37%.（3）The reactor has certain impact resistance and adaptability,and has good adaptability potential for organic load and ammonia nitrogen load.3.The basic working mechanism and performance of reactors:The MABR process uses the hollow fiber membrane as a medium for oxygenation of water bodies and as an attachment medium for biofilms.Oxygen diffusion through hollow fiber membranes results in oxygen concentration gradient,resulting in layered structure of biofilm attached to the filaments,which are aerobic zone,facultative zone and anaerobic zone,respectively,to meet the survival conditions of different microorganisms.Therefore,organic matter such as carbon,nitrogen and phosphorus entering the reactor can be degraded and removed in different zones,and the microbial phase is abundant,which can verify the layered structure of the biofilm from the side.The main energy consumption of the reactor is air compressor power consumption,circulating pump power consumption and intake diaphragm pump power consumption.The volume transfer coefficient（K_Lα）of bubbling oxygen charging is about 8.7 times of that of traditional bubbling oxygen charging.The potential of aeration power consumption can reach 88.5%.