Investigation of biological and fouling characteristics of submerged membrane bioreactor process for wastewater treatment by model sensitivity analysis

In this study, a mathematical model for the submerged membrane bioreactor (SMBR) was developed. The activated sludge model No. 1 (ASM1) was modified to be suitable for describing the characteristics of the SMBR, and the resistance-in-series model was integrated into the ASM1 to describe membrane fouling. Using the newly developed model, the biological and fouling characteristics of the submerged membrane bioreactor process for wastewater treatment was investigated by sensitivity analysis. The sensitivity of effluent COD and nitrogen, TSS in the reactor and membrane flux with respect to each parameter (K_h, μ_H, K_S, K_NHH, K_NOH, b_H, Y_H, μ_A, K_NHA, b_A, Y_A, K_m and α) was investigated by model simulation. As a result, the most important factors affecting membrane fouling were hydrolysis rate constant (K_h) and cross-flow effect coefficient (K_m). Heterotrophic yield coefficient (Y_H) had a great influence on effluent quality. Effluent quality was also somewhat sensitive to K_h. Peculiar operating conditions of the SMBR such as long solids retention time (SRT), absolute retention of solids by membrane and high biomass concentration in bioreactor could explain these model simulation results. The model developed in this study would be very helpful to optimize operating conditions as well as design parameters for a SMBR system.