Study on the Effects of Shear Strength and Aeration Method on Membrane Fouling in Vertical A/O-MBR Process

Vertical Anoxic/Oxic Membrane Bioreactor (A/O-MBR) was used to treat domestic sewage. PVDF hollow fiber membrane has been used in MBR. According to the comparison of intercommunity between three non-Newtonian fluid models (Bingham model, Ostwald model and Herschel-Bulkley model) and the test data, the Ostwald model was chose to describe the function relationship between shear intensity and aeration amount. In order to initiating a circulation velocity and to enhancing the scour to the MBR, the traditional aeration method was changed in this experiment. Two baffles were placed on both sides of the membrane modules, and aeration heads were scattered between two baffles. The influence of shear intensity and new aeration method to membrane fouling was investigated in this paper at shear intensity of 20s(-1), 40s(-1), 60s(-1) and 80s(-1). The result shows that the stronger shear intensity is, the heavier is the MBR been scoured and the smaller is the change of TMP. The best shear intensity was G=60s(-1) after considering all factors comprehensively. Finally, the membrane modules were analyzed by scanning electron microscope (SEM). By the SEM pictures we can see that there are some spots on the membrane surface which deposited by fine grains, EPS and SMP. The spots have different size and location, large scale or compact contamination layer can not been found in the pictures. So it indicates that the changing of aeration method and the controlling of shear intensity has a positive impact on slowing down the membrane fouling.