Dynamic Longterm In-Series Resistance Modeling and Analysis of a Submerged Membrane Bioreactor Using a Novel Filtration Mode

This study is focused on the physical filtration characteristics of a flatsheet membrane bioreactor (MBR) operated under a novel filtration mode. The objective of this research was to demonstrate the possibility of running a membrane bioreactor with high MLSS concentration for prolonged periods without frequent blocking of the membranes. Current MBR designs mostly dictated by the manufacturers limit the level of MLSS that is taken as a basis for the design due to fouling problems. This restraint can be eliminated by applying higher shear rates and hence aeration intensity for the effective removal of cake layer from the surface of the membranes. A pilot scale MBR was setup at the inlet works of a domestic sewage treatment plant and was operated for 320 days. The system was operated continuously with an MLSS concentration of 13,000–16,000 mg/L for 285 days without the need for chemical cleaning. The apparent viscosity of the sludge was steady at 0.001 Pa.s throughout the study except for the period when there was no sludge wastage and the resultant viscosity reached almost 0.004 Pa.s. Resistance components were experimentally determined and compared against the results of dynamic long–term simulations using the in–series resistance model. It was found that cake resistance did not have major impact on the total resistance which was linked to the effective daily removal due to high shear rates. Intrinsic membrane resistance and fouling resistance were the main components contributing to total resistance having the fractions of 69% (Rm/Rt) and 30% (Rf/Rt) respectively.