Many factors affect the hydrodynamics of wastewater processes and hence MBRs. These range from physical properties (e.g. mixture rheology and gas/liquid/solid density etc.) to the fluid boundary conditions (e.g. inlet/outlet/recycle flowrates, baffle/mixer position etc.). However, many factors are peculiar to MBRs, these cover the filtration tank design (e.g. membrane type, multiple outlets attributed to membranes, membrane packing density, membrane orientation etc.) and its operation (e.g. membrane relaxation, membrane back flush etc.). The mixing modelling and design techniques applied to MBRs are very similar to those used for conventional activated sludge systems. They include the relatively quick and easy compartmental modelling technique which will only derive the RTD of a process (e.g. the MBR) or the process unit (e.g. membrane filtration vessel) and relies on broad assumptions of the mixing properties of each sub-unit. Computational fluid dynamics modelling (CFD) on the other hand does not rely on broad assumptions of the mixing characteristics and attempts to predict the hydrodynamics from a fundamental level. It is applicable to all scales of fluid flow and can reveal much information about the mixing in a process, ranging from the RTD to the shear profile on a membrane surface. Visualisation of MBR CFD modelling results is shown in the image. Investigations of MBR hydrodynamics have occurred at many different scales, ranging from examination of shear stress at the membrane surface to RTD analysis of the whole MBR. Cui et al. (2003) investigated the movement of Taylor bubbles through tubular membranes. Khosravi, M. (2007) examined the entire membrane filtration vessel using CFD and velocity measurements, while Brannock et al. (2007) examined the entire MBR using tracer study experiments and RTD analysis. The market of MBR is segmented based on end user, which includes municipal and industrial, and geography, which comprises Europe, Middle East and Africa (EMEA), Asia-Pacific (APAC) and the Americas. In this line in 2016 some studies and report showed that APAC region took the leadership position in terms of market share, owning 41.90% of it. On the other hand, EMEA’s market share is approximately 31.34% and eventually the Americas own 26.67% of it. APAC has the largest membrane bioreactors market.