Simulation of membrane fouling considering mixed liquor viscosity and variation of shear stress on membrane surface.

Simulation of membrane fouling in MBR was conducted considering accumulation, detachment and consolidation of extracellular polymeric substances accumulated on membrane surface. The fluctuation of shear stress working on membrane surface and the influence of the viscosity of mixed liquor were considered for the evaluation of shear stress. A flat-sheet-type membrane module was used and the change of trans-membrane pressure was measured in a laboratory-scale MBR reactor. Shear stress working on membrane surface caused by aeration was measured by a shear force sensor changing viscosity of bulk liquid. Effective shear stress on membrane surface was defined in the model as the sum of time-averaged shear stress and three times of standard deviation. The increase in the trans-membrane pressure was accurately simulated by the developed model suggesting validity of the developed fouling model and the idea of the effective shear stress on membrane surface.