The main drawback of membrane bioreactors (MBR) systems is the fouling of the membrane, which is decreased and/or prevented through gas sparging. However, this practice is based on rules of thumb or a trial-and-error approaches which are tedious, very time-consuming, do not necessarily provide optimal fouling control and they are not energy efficient. Therefore, dedicated experiments are needed to fully understand the hydrodynamics of it. A hollow sheet (HS) MBR was studied. Experimental velocity measurements were made using micro-propellers and compared to CFD results. A good agreement between experimental measurements and CFD results was found (error less than 11 % in average). Due to the fact the shear stress measurements were not perform, they were extracted from the CFD simulations, as the CFD simulation was validated against velocity data. The results of shear stress shows that the shear is homogeneously distributes over the predominant part of the membrane surface.