Membrane bioreactor (MBR) is a combination of membrane processes like microfiltration or ultrafiltration with a biological wastewater treatment process, the activated sludge process. It is now widely used for municipal and industrial wastewater treatment. The two basic MBR configurations are a submerged membrane bioreactor (SMBR), and a side stream membrane bioreactor. In the SMBR configuration, the membrane is located inside the biological reactor and submerged in the wastewater, while in a side stream membrane bioreactor, the membrane is located outside the reactor, as an additional step after biological treatment.