Research On Carbon And Nitrogen Removal Performance Of Filler And Membrane Aeration Biofilm Reactor

Aeration is an important operation unit of aerobic biochemical wastewater treatment process.However,the low efficiency of traditional aeration leads to large power consumption and high operation cost.In recent years,people have used gas separation membrane as both an aeration unit and a carrier of microorganisms,which has greatly improved the utilization efficiency of oxygen.However,the problems of small specific surface area of membrane and serious pollution need to be overcome.In this paper,a new type of filler and membrane aeration biofilm reactor（FMABR）is proposed,which aims to comprehensively improve oxygen utilization rate and pollutant treatment efficiency by using porous membrane as aeration unit and filler as microbial carrier with close to aeration method.Based on the principle of oxygen transfer,the research studied the diffusion and distribution of oxygen in a very close distance and the influence of liquid disturbance on the distribution of dissolved oxygen concentration,explored the difference in the oxygenation performance of homemade tubular membrane（HTM）and hollow fiber membrane（HFM）,guided the design of coupling filler and aeration membrane,designed tracer experiment to study the hydraulic performance in the reactor,and studied the carbon and nitrogen removal performance of sewage in the coupling reactor through biological experiments,Finally,a comprehensive analysis of the microbial population on the surface of the aeration membrane and the filler was investigated at different sites of the coupling process.The main results are as follows:（1）The concentration distribution of dissolved oxygen varies greatly within 0.01m from the surface of the aeration membrane.Prolonging the diffusion time and shortening the diffusion distance can improve the dissolved oxygen concentration in very close distance,but the change of diffusion distance has a greater impact on the distribution of dissolved oxygen.In the design of the coupling form of aeration membrane and filler,it is necessary to limit the distance between the filler and the aeration membrane.Increasing the liquid disturbance intensity and aeration pressure（aeration volume）can rapidly increase the dissolved oxygen concentration in the very short distance of the aeration membrane.For hollow fiber membrane aeration,the change of liquid disturbance intensity has more obvious influence on the dissolved oxygen concentration;For tubular membrane aeration,the aeration capacity is in direct proportion to the aeration volume.It was found that the oxygenation capacity per unit area of tubular membrane was about 3-5 times that of hollow fiber membrane.（2）The short flow phenomenon can be significantly weakened after the filler is added.The dead zone is reduced by 6.95%-17.47%,and the effective volume ratio of the reactor is increased by 1.73-2.29 times after the filler is added.Theoretically,the number of full mixed flow reactors in series is positively related to the hydraulic retention time.Prolonging the hydraulic retention time can make the fluid flow in the reactor tend to plug flow.（3）Both the hollow fiber membrane aerated biofilm reactor（RM）and the filler coupled hollow fiber membrane aerated biofilm reactor（RFM）have high carbon and nitrogen removal performance.Compared with RM,the average removal rates of final COD and NH₄⁺in RFM increased by 5.97%and 5.15%respectively,the maximum removal loads of COD and NH₄⁺increased by 4.88%and 11.76%respectively,and the membrane fouling decreased by 8%-26%after long-term operation.（4）In the filler and HTM aerated biofilm reactor（HTM-FMABR）,with the increase of the fillers per membrane area,the pollutant removal effect is improved and the membrane fouling is reduced.Compared with the reactor with the least fillers per unit membrane area（R0.5 reactor）,the reactor with the most fillers per unit membrane area（R2 reactor）increased the average removal rates of COD and NH₄⁺by10.71%and 27.85%respectively in the final stage,and the maximum removal loads of COD and NH₄⁺increased by 16.59%and 33.33%respectively.The dissolved oxygen concentration in the reactor is controlled at more than 2 mg/L and there is almost no accumulation of nitrate and nitrite nitrogen,indicating that simultaneous nitrification and denitrification and aerobic denitrification exist in the reactor.There is an obvious concentration gradient in the reactor,and the area closest to the water inlet has the largest contribution to COD and NH₄⁺removal,which are 59%-79%and35%-70%respectively,which is of reference significance for shortening the hydraulic retention time and reducing the reactor volume.（5）Under the same treatment effect,the maximum pollutant removal load per unit membrane area of HTM-FMABR was 54 times that of HFM-FMABR,and the filler amount was only 42.7%of that of HFM-FMABR.Aeration membrane type and spatial location showed strong selectivity to microbial diversity and community structure.Compared with HFM aeration,HTM aeration has more kinds of microbial flora and higher similarity with inoculated sludge.Proteobacteria,as the main functional flora for nitrogen and carbon removal,is the dominant bacteria in FMABR system（except R2 reactor）;The dominant flora in R2 reactor is Firmicutes,which indicates that R2 reactor has good resistance to harsh environment.The dominant bacteria in HTM aeration reactor are Trichococcus and Sphaerotilus,and Trichococcus is suitable for growing in areas with high DO and high pollutants,while Sphaerotilus is more suitable for enriching in areas with low DO and high pollutants.The dominant bacterium Nakamurella in the HFM aeration reactor makes this type of reactor have an efficient and stable ammonia nitrogen removal effect.The existence of hyphomicrobium on the surface of aeration membrane proved that there was aerobic denitration phenomenon in the reactor.In this paper,the combination mode of filler and aeration membrane is designed by studying the oxygenation performance of aeration membrane and the law of oxygen mass transfer in the liquid main body,which provides theoretical basis and technical support for the application of membrane aeration technology in sewage treatment from the perspectives of actual operation performance of the reactor,membrane pollution degree,microbial community.