Study And Optimization Design On The Oxygenation And Quality Improvement In Black Odorous Waters By Bubble-MABR Technology

The key point to the restoration of the urban black odorous water is to increase its dissolved oxygen（DO）content.At present,the common aeration technologies include mechanical aeration,microporous aeration,jet aeration,and micro-nano aeration,membrane aeration biofilm reactor（MABR）technology,etc.The first four technologies are traditional foaming aeration technologies,and the MABR technology is a bubble-free aeration technology.MABR has advantages in oxygen transfer efficiency compared with other traditional bubble aeration technologies,bBut the MABR’s aeration characteristics of low-pressure and bubble-free make the DO distribution in the aerated water uneven and hinder the restoration of black and odorous water,especially when the water flow rate is close to zero.The traditional bubble aeration technologies are not as high as the MABR in oxygen utilization efficiency,but a large number of bubbles will be generated during the aeration process,and the bubble could induce turbulence and agitate the water body,then the DO could be evenly distributed.Therefore,it is necessary to develop a new technique that has both high oxygen transfer efficiency and uniform DO distribution in the water.The main research contents and conclusions of this paper are as follows:（1）Considering the advantages and disadvantages of MABR and traditional bubble aeration technologies,the bubble-MABR technology was proposed,which was improved with special hollow fiber membrane that set in the hollow fiber membrane module for making bubbles.The bubble plume can be induced,and the stirring characteristic of the bubble plume can make the bubble-MABR technology to improve the DO uniformity while maintaining the high oxygen transfer efficiency,thereby to improve the treatment efficiency of black odorous water.（2）In the test device with an effective volume of 4 m×1 m×2 m（length×width×height）=8 m³,the oxygenation uniformity and oxygenation effect of the bubble-MABR technology in the simulated black odorous water were analyzed under the different aeration pressures,different water depths and different membrane module spacing.The results showed that:1)In terms of oxygenation effect,the aeration pressure has the most significant effect on the oxygenation effect of the bubble MABR technology,and the membrane module spacing and water depth have a relatively weak influence.The average DO saturation values of river water within 24h at the aeration pressures of 0 kPa,10 kPa,20 kPa and 30 kPa were 11.5%,25.1%,18.1%,43.6%respectively;Under the water depth of 1.0 m,1.5 m and 2.0 m,the average DO saturation rates of river water in 24 h were 42.01%,44.53%and 43.57%,respectively;Under the membrane module spacing of 3 m,2 m,and 1 m,the average DO saturation rates in river water within 24 h were 40.9%,45.7%,and 43.6%,respectively.2)In terms of oxygenation uniformity,as the aeration pressure increases,the influence scope of the bubble type MABR technology increases in the horizontal and vertical directions,and the uniformity also becomes better;compared with the 0 kPa test（the mean variance of the DO saturation rate of the river water in the horizontal and water depth tests were1.7 and 13.5,respectively）,the mean deviations of the DO saturation rates of the river water were 0.3,3.9 and 0.4 in the horizontal test and were 9.8,18.4 and 3.4 in depth test at the aeration pressures of 10,20 and 30 kPa.The bubble MABR technology operateed at an aeration pressure of 30 kPa can make the distribute of DO in the horizontal and vertical directions of 2 m to keep even.The bubble-MABR technology can realize a good oxygenation effect and uniformity to the water.（3）In the test device with an effective volume of 4 m×1 m×2 m（length×width×height）=8 m³,the performance of the bubble-MABR technology in the simulated black odorous water was analyzed under different aeration pressures,different water depths,different membrane module spacing and different flow rates.The results showed that:1)The aeration pressure and flow rate had the greatest influence on the degradation of ammonia nitrogen（NH₄⁺-N）,and the membrane module spacing and the water depth has the least influence;Within the aeration pressure range of 10 kPa³0kPa,the degradation rate increases with aeration pressure,and the degradation rates were 0.005 h^-1,0.015 h^-1,and 0.030 h^-1,respectively;In the flow rate range from 0.5m/h to 2.0 m/h,the degradation rate increased with the flow rate.At 0 m/h,0.5 m/h,1.0m/h and 2.0 m/h,the degradation rates were 0.058 h^-1,0.060 h^-1,0.081 h^-1 and 0.102 h^-1 respectively;Under the water depth of 1.0 m,1.5 m,2.0 m,the degradation rates are0.037 h^-1,0.039 h^-1,0.030 h^-1;Under the module spacing of 1 m,2 m,3 m,the degradation rates were 0.053 h^-1,0.058 h^-1,and 0.030 h^-1,respectively.2)Under different aeration conditions,the concentration of nitrate nitrogen increased in different degrees;the maximum reduction of total nitrogen（TN）within 24 h was 1.7 mg/L,and the maximum removal rate of COD was 78.20%.The concentration of the total phosphorus（TP）is almost unchanging.3)The results of denitrification operation under aerobic-static anaerobic conditions showed that the concentrations of DO,TN and COD decreased significantly.The degradation rates of the latter three were 0.048 h^-1,0.006h^-1,0.015 h^-1,respectively.The concentration ofNH₄⁺-N also decreased,the degradation rate was 0.005 h^-1,and simultaneous nitrification and denitrification occurred in the test.Bubble MABR technology exhibits good features of carbon and nitrogen removal.（4）According to the foregoing test results,the design optimization model for the in-situ river was established.Taking the Inner Circular River in the Beiyangyuan Campus of Tianjin University as an example,the layout scheme and operation of the bubble-MABR technology in the Inner Circular River were designed and the simulation model was solved by genetic algorithm.The calculation results show that the best solution is to arrange 3 groups of membrane modules,each group is laid as long as 18m with the group spacing of 240 m,and aeration is uninterrupted for 48 days under the aeration pressure of 10 kPa.The water quality can be improved,and the required operation cost is 31.05 thousand yuan.The optimization model gives practical arrangement and operation scheme of the aeration device when treating the black and odorous water body,which could provide reference and guidance for the application of the technology in practical project.