26. Integration of Experimental and Numerical Methods to Investigate the Effect of Hydraulic Retention Time on Ultrafiltration Membrane Fouling

The floc formation, breakage and regrowth processes were investigated by numerical simulation to explore the effect of hydraulic retention time on ultrafiltration membrane (UF) fouling. Using a numerical method, the floc average size, fractal dimension and porosity under various coagulation conditions were investigated. The standardized flux and invertibility of membrane fouling were also investigated. Results illustrated that flocs formation under shorter flocculation time (10 min) had a small value of fractal dimension, which readily generated a larger pores and shaggy cake layer on the surface of membrane. An initial simplified breakage model based on DLA model was proposed, which demonstrated that the broken flocs afforded more opportunities for diffused particles to access deeper-lying flocs uniformly packed around the aggregated core. Flocs became increasingly compact with increased time of stirring after breakage. Therefore, shortening of stirring time, whether during flocculation or recovery process, could enhance the permeability of membrane.