What is a Membrane Biological Reactor (MBR)?
An MBR consists of two principal components: (1) a biological reactor tank, and (2) an ultrafiltration or microfiltration membrane to retain biological solids within this tank. The membrane may either be internal or external to the reactor vessel. The membrane provides a barrier to keep microbial solids in the reactor and renders a clarified, solids-free effluent stream for discharge. The microbial solids are essentially the same as those found within activated sludge systems at water treatment plants, but within the MBR, they are weaned to grow on very difficult-to-degrade pollutants. These biological solids use the pollutants in the wastewater as food, creating an even greater quantity of microorganisms within the reactor. The age of the microorganisms in the reactor (i.e., the solids retention time, or SRT) is controlled automatically by the periodic wasting of a small amount of reactor contents to the sewer. To a large extent, the SRT dictates the effluent quality, or treatment lev
