Feed water (usually water coming directly form overflow) is flowing upwards through the moving filter bed. Filtrated water is discharged at
the top and into the sump. Solids are retained and the established biomass converts organic solids into No3. In order to maximize oxygen levels and the growth f the aerobic bacteria, air is injected into the moving media bed to create ideal operating conditions for the filters' biomass.
For denitrification, anoxic Moving Bed Biofilm Reactor MBBR tanks are used. The anoxic tank is similar to aerobic Moving Bed Biofilm Reactor MBBR tank described above except that no oxygen is supplied. The tank contains no diffusers and the media is kept in suspension in the reactor through submersible mixers. Other feature such as the screen is the same as aerobic reactor although the design may be slightly different.
Okay. This one is on the engineers. The idea of a fixed-film process is that the biofilm stays in the tank. This is what sets the MBBR biological process apart from traditional activated sludge processes. On occasion, there have been reports of the carrier media getting out of the reactor. Inside an MBBR biofilm reactor, there is supposed to be a sieve screen mounted to the outlet that prevents this from happening. But, if the sieve is not sized correctly (or installed correctly in some cases), the media can slip through. This problem can be avoided entirely if you partner with a good company with competent designers that make sure to double check things like making sure the mesh openings in the sieve aren't bigger than the carriers.
What happens in a plain clarifier (with no lamella plates or tube modules) is this: the water flows into the bottom and out at the top, and you make it so big that even though the descent rate of the tiny floc particles is very slow, the rise rate of the water is even slower, so the particles settle to the bottom.
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MBBR Technology Today many wastewater treatment facilities are being expanded to provide additional capacity because of increased flow and organic loading. Often these facilities have limited space due to encroaching development. As a result, processes continue to be developed to address the site constraints faced by municipal and industrial wastewater treatment facilities. One of these processes is activated sludge with suspended fixed-film packing, such as the Moving Bed Biofilm Reactor (MBBR). MBBRs incorporate benefits provided by both fixed film and activated sludge processes. The MBBR process is a continuous flow process that uses small high-density polyethylene (HDPE) carrier elements to provide sites for active bacteria attachment in a suspended growth medium. This allows a higher concentration of active biomass to be maintained in the reactor for biological treatment without increasing the reactor size. The result is more treatment capacity within a given reactor volume, resulting in a smaller footprint compared to a conventional activated sludge process. In addition, unlike the conventional activated sludge process MBBRs do not require return activated sludge pumping. |
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Moving Bed Biofilm Reactor (MBBR) The MBBR was developed in Norway at the Norwegian University of Science and Technology in cooperation with a Norwegian company Kaldnes Miljǿteknologi (now AnoxKaldnes AS). The first MBBR was installed in 1989. Although it is a relatively new technology to the United States (first introduced in 1995), there are now over 400 installations worldwide in both the municipal and industrial sectors with over 36 in North America. The MBBR is a complete mix, a continuous flow-through process that combines the benefits of fixed film and suspended growth processes. Benefits include increased treatment capacity, improved settling characteristics, enhanced process stability, and reduced sludge production (Metcalf & Eddy, 2003). The process can either be used as a 1) pre-treatment system ahead of an existing activated sludge system for increased organic matter removal, 2) stand-alone biological treatment process for BOD removal, nitrification, and/or denitrification or 3) a retrofit of an existing activated sludge process to help increase the overall nitrification capacity of the existing system. The MBBR process uses small plastic carrier elements to provide sites for bacteria attachment in a suspended growth medium. The carrier elements allow a higher biomass concentration to be maintained in the reactor compared to a suspended growth process, such as activated sludge. This increases the biological treatment capacity for a given reactor volume. The carrier elements can be installed in either an anoxic reactor or aeration basin. A screen or sieve assembly with 5 mm slot openings is used to retain the carrier elements in the reactor. The effective open area of the screen is sized to provide less than 2 inches of headloss. However, the process does not require backwashing of the retention screens which retain the carriers. Figure 3 below shows a photograph of a sieve assembly on an effluent pipe for an MBBR. |
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1.MBBR-SBR SLUDGE PROCESS
2. ANAEROBIC-ANOXIC-OXIC PROCESS
3.OXIDATION DITCH-MBBR PROCESS
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