Study On Optimization Of Operation Conditions And Membrane Cleaning Method For MBR Wastewater Treatment Process

In recent years,membrane bioreactor?MBR?has been widely used in the field of domestic sewage and industrial wastewater treatment.During the process of MBR operation,the controlled conditions of the biological treatment and membrane separation have significant influence on the effect of the engineering operation and the membrane flux.However,to date,the researchs on the process optimization and membrane pollution control based on the large-scale MBR engineering is rare.In this paper,the large-scale MBR wastewater treatment plant in China was selected as the research object,the operation condition of the biochemical treatment part was studied by computer simulation,the operation condition of membrane pool was studied by means of productive experiment,and the cleaning methods of the membrane fouling were discussed based on the analysis and research of SEM and EDX.The main results of this study are as follow:The optimization scheme of the biochemical pool was as follow:the DO concentration in aerobic tank was maintained at 0.8 mg L^-1,the distribution ratio of water in anoxic and anaerobic tank was zero,reflux ratio of membrance pool was 200%,reflux ratio of aerobic tank was 250%,reflux ratio of anoxic tank was 50%.Hydraulic retention time?HRT?was maintained at 7.5 h,the overwater operation was not exceed 125,000 m³/d.Sludge age was maintained within 25 d.When the optimization scheme was applied to actual production,the removal rates of TP,TN,and NH₃-N increased by 6%,15%and 3%,respectively.The optimization scheme of membrane pool was as follow:The fact that the treatment of fiber,hair and dissolved organic matter was very important for controlling membrane fouling.The aeration strength was maintained in the 1.5-2 m³?m² h?^-1,in which 1.7 m³?m² h?^-1 was the optimum aeration strength.The critical membrane flux was 20 LMH under normal conditions.The optimal extraction ratio was 9:1,i.e.,producting water 9 min and stopping1min per 10 min.The analysis for membrane pollutants found that both inner and outer surfaces of membrane were contaminated,in which the pollutants in outer surface were mainly organic matter,while inorganic and organic pollutants coexisted on the inner surface.The optimized cleaning scheme was as follow:the contaminated membrane was washed with NaClO solution?200 ppm?,the backwashing cycle was 24 h,the soaking time was 20 min,and the backwashing time was 0.5 min.The recovery cleaning scheme:First,0.5%NaClO+0.3%NaOH alkaline washing was used,soaking time was 4 h;and then 0.3%citric acid washing was used and soaking time was 2 h;if necessary,2%dodecylbenzene sulfonic acid was used to remove oil and soaking time was 2 h.Finally,the membrane permeability recovery achieved almost 99%.The application of MBR technology in the large-scale municipal wastewater treatment plant is closely related to the operating conditions of the biological reaction pool and the membrane pool.The optimized operation scheme and membrane cleaning scheme in this paper can ensure the efficient and stable operation of the large-scale MBR project...