The Moving Bed Bio-Reactor (MBBR) includes a tank in any shape filled up with small carrier elements. The elements are specially developed materials of controlled density such that they can be fluidized using an aeration device. A bio-film develops on the elements, which move along with the effluent in the reactor. The movement within the reactor is generated by providing aeration with the help of diffusers placed at the bottom of the reactor. The thin bio-film on the elements enables the bacteria to act upon the bio-degradable matter in the effluent and reduce BOD/COD content in the presence of oxygen from the air that is used for fluidization.Treated water flows from reactor through a grid or a sieve, which retains the MBBRbio-carriers in the reactor.
The process consists of adding small cylindrical shaped polyethylene carrier rings (specific density of about 0.96 kg/m3) in aeration tanks to support the biofilm growth. The bio-media when dumped inside the aeration tank, occupies about 25-30% of the tank volume. The fluidized bio media ensures optimum contact time & eliminates the fouling tendencies of fixed film media. The biofilm carriers are maintained inside the reactors by use of perforated plate at the outlet. As the effluent gets in contact with this media, the attached biomass degrades the organic matter. During this process, ammonia contained in the effluent is also oxidized to nitrates.
The process has a very high ‘BOD removal: aeration tank volume’ ratio. Since the biofilm is attached & grows on the biomedia, the FAB process generates very little sludge compared with conventional processes & does not require high sludge recirculation rates.