Resilient High‐Rate Sulfidogenesis in a Hydrogen‐Based Membrane Biofilm Reactor: Mechanistic Analysis of Kinetic‐Limited Performance Under Variable Loading

ABSTRACT Copper mining industry generates water with high sulfate (SO 4 2− ) concentrations. The hydrogen‐based membrane biofilm reactor (H 2 ‐MBfR) is a promising sulfidogenesis solution, using H 2 as a clean electron donor. An H 2 ‐MBfR was operated for 209 days treating synthetic mining‐influenced water under varying conditions (HRT, H 2 pressure, SO 4 2− loadings). The system proved highly resilient, achieving stable SO 4 2− removal (> 90%) and fully recovering from a severe shock load (4500 mg S L −1 ). To identify the governing mechanisms, a transient pseudoanalytical biofilm model was developed. A Global Sensitivity Analysis (Sobol) showed performance is dominated by the maximum specific growth rate (), detachment coefficient (), and H 2 S inhibition (). The model was calibrated on Stages 1–3 (Days 0–169, n = 44), achieving R² = 0.962 (calibration) and R² = 0.572 (blind validation, Stage 4). Crucial findings from the model calibration ( = 0.344 d −1 ) and a diagnostic analysis using the Thiele Modulus (mean = 0.224) strongly indicate that the system operated in a kinetically‐limited regime. Performance was governed by the delicate balance of slow growth and high detachment, not by mass transfer (H 2 supply or SO 4 2− diffusion). This research validates the H 2 ‐MBfR for high‐rate applications and correctly shifts the bottleneck for future optimization from mass transfer to biofilm retention kinetics.