Study On Aeration And Oxygen Mass Transfer Process Of Microporous Hose And Effect Of Strengthening Water Body Repair

The microporous hose aeration system is an aerobic device for effectively repairing polluted water bodies,and has gradually become a hot spot in the research of water body ecological restoration.The difference in the flow characteristics of the bubble plume during aeration will directly affect the mixing effect of the gas-liquid-solid three-phase and the oxygen transfer rate between the gas-liquid two phases,affecting the sewage treatment effect and energy consumption.Therefore,studying the influence of bubble plume motion structure on aeration oxygen mass transfer in aeration system has important theoretical reference value for improving oxygenation capacity and water quality improvement effect and reducing operating cost.In this study,the microporous hose aeration system was used as the research object.Using the image processing and particle tracking velocity measurement(PIV)method,the flow characteristics and velocity field of bubble plume under different aeration,aperture and tube length conditions were obtained,The oxygen mass transfer law of aeration system under different conditions was analyzed systematically,and the response relationship between bubble plume motion characteristics and oxygen transfer law was discussed.The purpose was to optimize the repair effect of microporous hose aeration system on polluted landscape water.The main research results include:(1)The aeration volume,pore size and tube length all affect the motion pattern and velocity field distribution of the bubble plume,and the most significant factor is the aeration.With the increase of aeration volume,the structure of the bubble plume tends to be complex,the Coanda effect is gradually enhanced,and the average velocity of the gas phase shows a large increase;As the length of the tube increases,the distribution of the bubble plume tends to diverge,and the average velocity of the gas phase decreases;With the increase of the pore size,the flow pattern of the bubble plume did not show significant changes,and the average velocity of the gas phase showed a small increase trend.(2)The parameter values such as the number of bubbles N,the geometric mean diameter dbs,the specific surface area Sb and the gas phase velocity u show regular changes with the change of various factors,which in turn affects the oxygenation performance of the aeration system.Among them,the aeration amount is linearly positively correlated with the oxygen transfer coefficient KLas and the oxygenation capacity EL,and has a power function relationship with the oxygen utilization rate EA,and the correlation coefficient R2 is 0.974,0.982 and 0.975,respectively;The pore size is linearly negatively correlated with KLas,EL and EA,and R2 is 0.940,0.937,0.943,respectively;The tube length is linearly positively correlated with KLas,EL and EA,and R2 is 0.956,0.976,0.960,respectively.(3)Aeration has a certain treatment effect on micro-polluted landscape water bodies.The average release rates of COD,TP,NH4+-N and TN in sediments under different working conditions were-0.820g/(m2·d),-0.019g/(m2·d),-0.155g/(m2·d)and-0.144 g/(m2·d).Under the conditions of aeration volume of 0.3m3/h,pore size of 200μm and tube length of 50cm,the removal rates of each pollutant were 83.3%,60.9%,94.2%and 70.8%,respectively.It is difficult to make all pollutant concentrations reach the surface V water quality standard by simple aeration method.It is recommended to use other measures for further treatment.