WASTEWATERBy Rick LallishWhat are the two methods or operational modes of membrane biologic reactor treatment units?A. Inner-OuterB. Serial-ParallelC. Over-UnderD. Internal-SidestreamAnswer: D. In areas where space is very limited or water reuse is necessary, membrane bioreactor treatment is a viable alternative. MBRs use either internal treatment (the unit is installed within the aeration basin) or sidestream treatment (the unit is a separate module). Many activated sludge plants can be modified to accommodate an MBR module. MBRs are unique in that no clarifier is necessary. The effluent is removed by permeating through the membranes, with pore sizes as small as 0.01 micrometers. Most solids and pathogens
