Moving Bed BioReactor (MBBR)
Technology MBBR is based on the principle of the biological active film which grows in little plastic support called “Carriers” or “Media” that are suspended in the reactor. This technology uses the advantages of the activated sludge and other biofilm systems (such as Trickling filters). Technically it is a hybrid technology (fixed and suspended biomass).
Carriers are designed to provide big surface and conditions for growing bacteria when suspended on water. MBBR uses the full volume of the aerobic reactor for bacterial growth. Conversely to what happens in a traditional activated sludge system, it does not require sludge recirculation because the biggest concentration of biomass is attached to the plastic carriers that wander freely in the mixed liquor. Carriers never leave the reactor since there are AISI 304 fine screens (sieves) at the outlet of the reactor.
MBBR mainly has the following uses:
For new facilities, especially the ones that require small space and easy operation for BOD/ COD and nitrogen removal.
As a previous high rate system for current biological treatments, used as a roughing stage.
To make an up-grade of an operating system with a specific civil work. Improve the process.
Some advantages of working with this technology are:
Less surface required
Easy up-grade for existing plants
Robust in low loads, toxic or hydraulic shocks
Specialised biomass since there is no need of sludge recirculation
Reactor can be used for both aerobic and anoxic processes.
In the aerobic process the carriers are held in suspension by the shaking made by the air supplied by the diffusers, while in the anoxic MBBR there is a mixer that provides energy needed to keep the carriers in motion.
A major benefit of this technology is that the amount of plastic filling in the reactor will depend on the need of each appliance. MBBR process can be used in several ways for BOD/ COD removal, namely:
MBBR + DAF Secundaria
MBBR + Lodo activado
Carriers (support media)
The carriers are the heart of the technology. These elements are designed to provide a great protected surface of biofilm and the optimal conditions for bacterial culture, when suspended in water.
There are plastic supports with different shape, size and surface, which give more flexibility for using the most proper media depending on the characteristics of waste waters, previous treatment, discharge regulations and available volumes.
Support medium or carriers are made of HDPE.
The development of biofilms rapidly occurs in most of water treatment aerobic systems. Even though the fixed biofilm is not visible until a few days later, hours after the start up you can perceive a microscopic layer.
At the beginning, the first bacteria in contact with carriers’ surface cannot attach to it, or they only attach temporarily, until 3 or 4 hours later when groups of bacteria attached to it start to grow from individual cells to form micro-colonies.