A biofilm model was developed to evaluate the key mechanisms including microbially-mediated NO3-, and SO42- reduction in the H-2-based membrane biofilm reactor (MBfR). Sensitivity analysis indicated that the maximum growth rate of H-2-based denitrification) and maximum growth rate of H2-based SO42- reduction (mu(3)) could be reliably estimated by fitting the model predictions to the experimental measurements. The model was first calibrated using the experimental data of a single-stage H-2-based MBfR fed with different combinations of ClO4-, NO3-, and/or SO42- together with a constant dissolved oxygen (DO) concentration at three operating stages. mu(1) and mu(3) were determined at 0.133 h(-1) and 0.0062 h(-1), respectively, with a good level of identifiability. The model and the parameter values were further validated based on the experimental data of a two-stage H-2-based MBfR system fed with ClO4-, and DO simultaneously but at different feeding rates during two running phases. The validated model was then applied to evaluate the quantitative and systematic effects of key operating conditions on the reduction of ClO4-, NO3-, and SOi-as well as the steady-state microbial structure in the biofilm of a single-stage H-2-based MBfR. The results showed that i) a higher influent ClO4- concentration led to a higher ClO4- removal efficiency, compensated by a slightly decreasing SO42- removal; ii) the H-2 loading should be properly managed at certain critical level to maximize the ClO4- and NO3- removal while limiting the growth of sulfate reducing bacteria which would occur in the case of excessive H-2 supply; and iii) a moderate hydraulic retention time and a relatively thin biofilm were required to maintain high-level removal of ClO4- and NO3- but restrict the SO42- reduction. (C) 2017 Elsevier B.V. All rights reserved.