Calibrating a side-stream membrane bioreactor using Activated Sludge Model No. 1

Membrane bioreactors (MBRs) are attracting global interest but the mathematical modeling of the biological performance of MBRs remains very limited. This study focuses on the modeling of a side-stream MBR system using the Activated Sludge Model No. 1 (ASM1), and compares the results with the modeling of traditional activated sludge processes. ASM1 parameters relevant for the long-term biological behaviour in MBR systems were calibrated (i.e.Y-H = 0.72 gCOD/gCOD, Y-A = 0.25 gCOD/gN, b(H) = 0.25 d(-1), b(A) = 0.080 d(-1) and f(p) = 0.06), and generally agreed with the parameters in traditional activated sludge processes, with the exception that a higher autotrophic biomass decay rate was observed in the MBR . Influent wastewater characterization was proven to be a critical step in model calibration and special care, should be taken in characterizing the inert particulate COD (XI) concentration in the MBR influent. It appeared that the chemical-biological method was superior to the physical-chemical method. A sensitivity analysis for steady-state operation and DO dynamics suggested that the biological performance of the MBR system (the sludge concentration, effluent quality and the DO dynamics) are very sensitive to the parameters (i.e. Y-H, Y-A, b(H), b(A) mu(maxH) and mu(maxA)), and influent wastewater components (X-I, S-S, X-S and S-NH).