The Moving Bed Biofilm reactor is based on MBBR biofilm technology. It utilizes the advantages of activated sludge and previous biofilm systems without being restrained by their disadvantages. The basic idea behind MBBR is to have a continuously operating, non-cloggable biofilm reactor with no need for backwashing, low head loss and high specific biofilm surface area. This is achieved by growing biofilm on small carrier elements that move along with water in the reactor. The movement is caused by the aeration in the reactor. The carrier element is made of polyethylene or polypropylene with a density of slightly less than water and shaped like small cylinders about 9-64 mm in diameter, depending on the application. The filling rate of carriers in the reactor may vary between 10 and 65 %, also depending on the application.
The microorganisms grow on the carriers as a biofilm. In the biofilm, the microorganisms are well protected which makes the process tolerant towards variations and disturbances and even extreme loads can be handled. With the MBBR biofilm technology, the process can be made very compact, since the microorganisms in the biofilm are very efficient. The process is also easy to maintain and the amount of active biomass is self regulated and depends on incoming load and hydraulic retention time. Since the carriers are continuously moving, the process is insensitive to suspended solids in influent wastewater.
In order to retain the carrier elements in the reactor, a sieve is placed at the outlet of the reactor, The air agitation is arranged so that the carrier elements are constantly being moved upward over the surface of the sieve. This creates a scrubbing action that prevents clogging. Both the aeration system and the sieves are designed to work well with the chosen carrier elements. The produced excess sludge sloughs of the carrier media, bypasses the outlet sieves and passes to the post-treatment step for further treatment and ultimate removal.