Membrane technology has led to a revolutionary new concept in wastewater treatment. Membranes act as a barrier to bacteria and suspended solids to produce a low turbidity treatment plant effluent with very low bacteria counts. Membrane Bioreactor (MBR) is the combination of a membrane process such as microfiltration or ultra-filtration with a suspended growth bioreactor. This very compact arrangement produces a MF/UF quality effluent suitable for reuse applications or as a high-quality feed water source for Reverse Osmosis treatment The submerged configuration relies on coarse bubble aeration to produce mixing and limit fouling. The energy demand of the submerged system can be up to 2 times lower than the side stream systems and submerged systems operate at a lower flux, demanding more membrane area. In submerged configurations, aeration is considered as one of the major parameters on process performances both hydraulic and biological. Aeration maintains solids in suspension, scours the membrane surface and provides oxygen to the biomass, leading to a better biodegradability and cell synthesis.