The membrane has a nominal pore size of 0.04 . Each module has an effective membrane surface area of 0.047. A chiller (Neslab RTE7) equipped with a stainless steel heat exchanging coil was used to maintain a constant temperature in the MBR. A personal computer was used to control the permeate peristaltic pump to operate on a 14 min suction and 1 min off cycle to provide relaxation time to the membrane modules. Flowrate of the influent pump was matched with that of the permeate pump to maintain a constant reactor volume. A mixer was continouusly used to ensure homogeneous conditions of the mixed liquor and to pervent the settling of biomass.