Perchlorate, nitrate, and sulfate reduction in hydrogen-based membrane biofilm reactor: Model-based evaluation.

A biofilm model was developed to evaluate the key mechanisms including microbially-mediated ClO 4 − , NO 3 − , and SO 4 2− reduction in the H 2 -based membrane biofilm reactor (MBfR). Sensitivity analysis indicated that the maximum growth rate of H 2 -based denitrification ( μ 1 ) and maximum growth rate of H 2 -based SO 4 2− reduction ( μ 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 ClO 4 − , NO 3 − , and/or SO 4 2− together with a constant dissolved oxygen (DO) concentration at three operating stages. μ 1 and μ 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 ClO 4 − , NO 3 − , SO 4 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 ClO 4 − , NO 3 − , and SO 4 2− 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 ClO 4 − concentration led to a higher ClO 4 − removal efficiency, compensated by a slightly decreasing SO 4 2− removal; ii) the H 2 loading should be properly managed at certain critical level to maximize the ClO 4 − and NO 3 − 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 ClO 4 − and NO 3 − but restrict the SO 4 2− reduction. [ABSTRACT FROM AUTHOR]