MABRs vs MBRs
What is an MABR?
MBRs vs MABRs
Both a regular immersed MBR and an MABR (a membrane-aerated biofilm reactor) consist of a membrane submerged in a tank, and in both cases this system is fed with air.
For the MBR, the membrane is used to separate the product water from the biomass. This means that the product water is clarified and largely disinfected. Also, the membrane tank is fed with the mixed liquor from the process biological tank rather than the wastewater itself.
For an MABR, a membrane aeration biofilm reactor, the membrane is not used to filter the water. Instead, it is used to aerate the solution, replacing the conventional fine bubble diffuser. In doing so the oxygen in the air, or from a pure oxygen source, is introduced in the molecular, or “bubbleless” form. This leads to highly efficient transfer of oxygen into the solution, since the oxygen is no longer limited by diffusion from the inside of the air or gas bubble to the gas bubble surface and then across the surface to the surrounding water.
Since the membrane is being fed with molecular oxygen and is immersed in the tank being fed with the influent wastewater, a biofilm forms on the membrane surface. An MABR is therefore an example of a “fixed film” process - like a trickling filter - as opposed to a purely suspended growth process - i.e. one based on activated sludge - as is the case for the MBR.
The MABR still has a mixed liquor of suspended particles, as with other fixed film processes such the moving bed bioreactor (MBBR), but at lower concentration than the MBR. Biological treatment is thus achieved both by the biofilm and by the suspended flocs.