Study On The Membrane Fouling Of Liquidized Bed Membrane Bioreactor Controlled By Online Ultrasonic

With the rapid social economy development, industry and urban water consumption have grown quickly; hence, the wastewater becomes an important water resource. As a new wastewater utilization technique, membrane bioreactor could actualize the dynamic cycling of water within regions, and ensure the safety and stability of recycling water's quality. Actually, the fluidized bed MBR, combined by membrane bioreactor and fluidized bed technique, can strengthen their advantages and improve the removal efficiency of pollutant; however, membrane fouling became one of the key problems that affect the stability and economic efficiency for running membrane bioreactor.As this paper was based on both domestic and foreign research results of Ultrasonic Cleaning Technique in Membrane Bioreactors, while targeting at fluidized bed MBR's membrane fouling, researchers suggested to use on-line ultrasound for controlling membrane fouling. Basing on constructing the fluidized bed MBR, researchers ascertained ultrasound parameters that could be chosen in ultrasonic experiment, and then launched the long-run test of treating synthetic wastewater by ordinary fluidized bed MBR and ultrasonic fluidized bed MBR. Research was organized under conditions of a low-mid-frequency at 200W, a low-mid-frequency at 300W and a mind-frequency at 300W respectively, from which we studied the effect of on-line ultrasound controlling membrane fouling and how the ultrasound impact the effect of fluidized bed membrane bioreactor's effluent and the properties of mixed sludge liquor.The research results showed that:on-line ultrasound reduced the MLSS concentration and the ultrasound of a low-mid-frequency at 300W influenced on the MLSS concentration most obviously. The low-mid-frequency ultrasound increased the content of polysaccharides in exocellular polymer which caused the increase of the viscosity and the rise of viscosity would not deteriorate the filterability of the mixed liquor. On-line ultrasound could reduce the concentration of soluble microbial production and avoided the worsening of membrane pollution.-The ultrasound reduced the average particle size of the mixed liquor but only when the power is 300W will cause average particle size of mixture dropped significantly. These phenomenons were the root cause of other properties of the mixed liquor change. Online ultrasound controlled the development of membrane fouling effectively and improved the membrane flux obviously. Under a low-mid frequency ultrasound at 300W over 31 days operation, the decline of flux in fluidized bed MBR with ultrasound was 9% fewer than normal MBR. Besides, on-line ultrasound could reduce the filtration resistance of membrane significantly. After a period of operation, the total filtration resistance of membrane in the fluidized bed MBR with a low-mid-frequency ultrasound at 200W was 23.6% lower than the normal MBR.