Nowadays, membrane is employed in a variety of water and wastewater treatment processes. In the Membrane Aerated Biofilm Reactor (MABR) process, gaseous substrate (i.e., air or pure oxygen) is supplied from the inside of membrane and acts as an electron acceptor. On the other hand, dissolved organic carbon (BOD/COD) or organic nitrogen (BON) acts as a coupled electron donor. In the middle of the electron transfer reaction, biofilm is formed on the outer surface of membrane. The MABR process is applicable to the high organic strength wastewater, total nitrogen removal in high loading with a view to high oxygen transfer efficiency and low energy consumption rate. Currently, our research team developed a novel MABR process with ultra high oxygen transfer rate (> 10.0 g-O₂/m²·day).