Experimental Study On Pollution Control Of Ultrafiltration Membrane By Chemically Enhanced Backwashing

The membrane fouling problem of ultrafiltration technology limits its application in water treatment process.In order to alleviate the problem of membrane fouling,this paper systematically studies the pollution control efficiency of chemical enhanced backwashing on flat membrane ultrafiltration membrane.Established a pilot system to investigate the water purification efficiency and membrane pollution control effect The water efficiency and membrane pollution control effects were compared with the application effects of chemically enhanced backwashing in the long and short process ultrafiltration combined process,and the following results were obtained.The laboratory ultrafiltration membrane system was used to investigate the effect of conventional ultrafiltration effluent backwashing and chemically enhanced backwashing on membrane fouling control of different materials.The polyethersulfone ultrafiltration membrane and the polyvinylidene fluoride ultrafiltration membrane,after being contaminated by humic acid and sodium alginate,the flux decreased to varying degrees,and ultrafiltration membrane fluxes have different degrees of recovery after conventional backwashing and chemically enhanced backwashing.With different degrees of recovery,chemical backwashing has a better effect on flux recovery.According to pollution reversibility analysis,chemically enhanced backwashing converts some irreversible pollution into reversible pollution and alleviates membrane fouling.The ultrafiltration membranes were characterized by different means.The surface of the ultrafiltration membrane using chemically enhanced backwashing was closer to the new membrane in terms of functional groups,morphology and roughness,indicating that chemically enhanced backwashing can better clean the surface.Filter membrane.A pilot-scale study was carried out using a siphon-type ultrafiltration water purification device to study the water purification efficiency and membrane pollution control effect of the pilot system.The pilot system has excellent retention effect on turbidity and microorganisms,and the removal rate is as high as 95%.It has certain removal effects on organic substances such as COD_Mn,UV₂₅₄,DOC and ammonia nitrogen.The average removal rates are 18.34%,11.40%,8.56%.and 11.13%.The use of chemically enhanced backwashing has a good control effect on membrane fouling,and the ultrafiltration device can maintain stable operation of the device for a long time.Comparing the pilot system with the water plant process,the two ultrafiltration combined processes have significant removal effects on turbidity,and also have certain removal effects on organic substances such as COD_Mn,UV₂₅₄,DOC and ammonia nitrogen,and the removal rate of short process ultrafiltration combined process The removal rates of the short-flow ultrafiltration combined process were32.8%,21.4%,26.4%and 41.9%,while the removal rates of the water plant long process ultrafiltration combined process were 34.9%,21.4%,28.1%and 48.4%.The water-immersed ultrafiltration membrane tank is chemically enhanced and backwashed,which can effectively alleviate membrane fouling,slow down the growth rate of transmembrane pressure difference,and effectively extend the chemical cleaning cycle from 15 d to 35 d.