Study On Bubble-free Aeration-Aerobic Contact Oxidation Reactor In Domestic Sewage Treatment

With the continuous improvement of the living standards of our residents,the discharge of urban domestic sewage is also increasing.Domestic sewage contains a large amount of organic matter and pathogenic microorganisms.If it is not handled properly,it will cause environmental damage and cause epidemic outbreaks.And it will be a great threat to human health.Therefore,it is extremely urgent to deal with the domestic sewage in towns more efficiently.However,in the process of treating domestic sewage by biological treatment,most of the oxygenation as a bubble rises to the surface of the water with the flow of water in the reactor,and finally enters the outside air,resulting in a decrease in the utilization rate of oxygen.The bubble-free membrane aeration technology can generate bubbles that are indistinguishable and allow oxygen to enter the water body,greatly improving the utilization of oxygen.However,since the biofilm of membrane aeration biofilm reactor(MABR),which is currently widely used,directly adheres to the aeration membrane,it is easy to cause clogging of the membrane pores,and in the long-term,the aeration efficiency is lowered,thereby affecting the treatment effect.Based on this phenomenon,the paper proposed a membrane assembly construction form.By attaching the biological carrier to the aeration membrane,this will effectively alleviate the membrane fouling,and this new reactor is called Bubble-free Aeration-Aerobic Contact Oxidation Reactor.Bubble-free Aeration-Aerobic Contact Oxidation Reactor is a new type of sewage treatment technology that combines bubble-free membrane aeration technology with microbial contact oxidation technology.It uses a membrane device composed of a microporous membrane with high oxygen permeability and a filler with high bioadhesive rate.It can be used as a biological carrier and as a highly efficient oxygen supply source.At the same time,due to the relative independence of the biological carrier and the aeration membrane,the phenomenon of membrane fouling is greatly alleviated.It has high processing efficiency and low energy consumption compared with traditional biological treatment methods and MABR,so using the Bubble-free Aeration-Aerobic Contact Oxidation Reactor is an effective way to treat sewage.In this paper,the PTFE hollow fiber membrane is used as an aeration tool,and air is used as an aeration source,exploring the bubble point of aeration membrane and its influencing factors through clear water experiment,and the effects of circulating flow and aeration pressure on the aeration membrane oxygenation effect.The results show that on the same condition,the bubble point increases with the immersion depth of the membrane and decreases with the increase of circulating flow.When the aeration pressure is within the aeration bubble point,on the same condition,increasing the aeration pressure can increase the oxygenation effect of the aeration membrane,increasing the circulation flow rate can also increase the oxygenation effect of the aeration membrane.Compared with the ordinary aeration diffuser,the oxygen utilization rate of the bubble-free membrane aeration is as high as 63.3%,while the oxygen utilization rate of the latter is only 10.5%.Then during the start-up of the reactor,the artificial domestic sewage with different influent chemical oxygen demand(COD)concentration and ammonia nitrogen concentration was prepared as the phase concentration gradient to culture and acclimate the biofilm.The reactor in the whole phase ran for a total of 35 days.During the start-up operation,under normal influent concentration conditions,The highest COD removal rate after stabilization is 95%,and ammonia nitrogen is 84.1%.The data showed that the reactor was successfully started.At the same time,compared with the processing efficiency of the traditional MABR reactor under the same operating parameters,the result shows:The Bubble-free Aeration-Aerobic Contact Oxidation Reactor has better treatment effect on COD and ammonia nitrogen than the traditional MABR reactor.In the face of higher influent concentration shocks,the system recovery capability of the Bubbleless Aeration-Aerobic Contact Oxidation Reactor is also significantly better than that of the conventional MABR reactor.In comparison with the treatment efficiency of aeration with a ordinary aeration head,the bubble-free aeration method has a better effect on COD and ammonia nitrogen treatment,the average COD removal rate difference is 11.8%,and the average ammonia nitrogen removal rate difference is 9.3%.Under the condition that the reaction system is stable,the single factor experiment was designed to investigate the effects of hydraulic retention time(HRT),dissolved oxygen concentration(DO Concentration)and pH on the efficiency of the reaction system.Subsequently,the three influencing factors,HRT,DO Concentration and pH,were analyzed by multi-factors to obtain the optimal process operating parameters of the reaction system.The optimal operating parameters of the reaction system are:HRT=11.97h,DO Concentration=4.74mg/L and pH=7.67.The reliability of the operating parameters was verified by experiments.