A membrane fouling using computational fluid mechanics was developed for the prediction of trans-membrane pressure increase during the operation and for the simulation of the influence of design and operational parameters, such as configuration of reactors, the position of membrane modules, permeate flux and air flow rate for aeration, on the performance of reactors. CFD was employed for the calculation of shear stress and the comparison of the calculated values with measured ones suggested the validity of CFD for the development of fouling model of MBRs.