5.3.1.3 Moving Media SystemsThese involve the synthetic small sized media, which are fluidized in the reactor by artificial air supplyby compressed air released at the floor of the reactor. This brings about the circulatory movement ofthese media into the tank contents. The trade names are Fluidized Aerobic reactor (FAB), Moving BedBiological reactor (MBBR) as also Fluidized Anaerobic reactor and their operational principleis illustrated in Figure 5.8.The microbial film that develops over the surface of the fluidized media permits the metabolism.Secondary settling is needed in the case of FAB and MBBR. In the case of FAB, additional furthertreatment may also be necessary.