MEMBRANE BIOREACTORS (MBR)
Membrane Bioreactors (MBR) are a new generation of waste water treatment processes. Submerged membrane modules successfully replace the conventional sedimentation tank in the activated sludge treatment process for the separation of solid/liquid (biomass/treated water) with the result of having a more compact and efficient plant. MBR is installed to reach many different goals. One of them, maybe the most common, is to increase the efficiency of the biological plant reducing the dimensions of the biological oxidation or increasing the capacity of the existing biological plant, or even removing the settling tank. Important applications are pre-filtration before biological oxidation and softening of river water.
- Complete retention of bacteria and solids thanks to the ultrafiltration membranes (insensitive to problems of bulking).
- High retention of viruses
- High load of sludge
- Excellent depurative efficiency and lower production of excess sludge due to the high sludge age (SRT)
- Removal of non-biodegradable organic compounds
- Smaller plant size
How does it work?
Membrane module consists on two separate blocks: permeation block and aeration block. The permeation block consists of a backflushable membrane pocket, creating a self supporting membrane sandwich of only 2 mm thick. The membranes are connected with a main collector, through which the permeated water is discharged with constant flow by gravity or suction pump. The aeration block consists of a series of diffusers used to supply thin air bubbles and to create an upward flow of water and air that keeps clean the surface of the membrane. By using a flat sheet membrane, activated sludge deposition has been reduced to minimum. It also allows a highly effective back-flush over the entire membrane surface. The process of separating biomass/permeated water is based on the mechanism of cross flow filtration of activated sludge, moving upwards and parallel to the surface of the membrane, and the liquid phase that permeates through the membrane as a result of the trans-membrane pressure (TMP).