EFFECTS OF BIOLOGICAL TREATMENT CONDITIONS ON PERMEATE FLUX OF UF MEMBRANE IN A MEMBRANE ACTIVATED-SLUDGE WASTE-WATER TREATMENT SYSTEM

A bench-scale membrane/activated-sludge wastewater treatment system was built and operated continuously for more than one year with peptone/glucose solution as a model waste water. During the course of the operation, biological treatment conditions such as load, sludge retention time and dissolved oxygen level were varied. Effects of these treatment conditions on soluble fraction components in the sludge and resulting permeate flux of the UF membrane were studied. The permeate flux was in good correlation with the differential Dissolved Organic Carbon (DOC) between membrane feed and permeate. When sufficient dissolved oxygen (DO) was supplied, DOC was produced quantitatively from loaded substrate into the bioreactor. With lower DO level (1-2 mg/l), although the substrate was still completely digested, production of DOC increased. Prediction of permeate flux from biological treatment conditions was also attempted to give a guide line for controlling biological treatment conditions from a point of membrane separation performance.