A biofilm model was developed to evaluate the key mechanisms including microbially-mediated ClO4 −, NO3 −, and SO4 2−reduction in the H2-based membrane biofilm reactor (MBfR). Sensitivity analysis indicated that the maximum growth rate of H2-based denitrification (μ1) and maximum growth rate of H2-based SO4 2−reduction (μ3) 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 H2-based MBfR fed with different combinations of ClO4 −, NO3 −, and/or SO4 2−together with a constant dissolved oxygen (DO) concentration at three operating stages. μ1and μ3were determined at 0.133 h−1and 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 H2-based MBfR system fed with ClO4 −, NO3 −, SO4 2−, 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 SO4 2−as well as the steady-state microbial structure in the biofilm of a single-stage H2-based MBfR. The results showed that i) a higher influent ClO4 −concentration led to a higher ClO4 −removal efficiency, compensated by a slightly decreasing SO4 2−removal; ii) the H2loading 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 H2supply; 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 SO4 2−reduction.
- Hydrogen-based membrane biofilm reactor
- Mathematical modeling