Scaling-up up-flow microbial electrolysis cells with a compact electrode configuration for continuous hydrogen production.

Maintaining high current densities is a key challenge in scaling-up microbial electrolysis cell (MEC) reactors. In this study, a novel 10 L MEC reactor with a total electrode surface area greater than 1 m was designed and evaluated to maximize the current density and H recovery. Performances of the reactor suggest that the longitudinal structure with parallel vertical orientation of the electrodes encouraged high fluid mixing and the sheet metal electrode frames provided distributed electrical connection. Results also demonstrated that the electrode pairs located next to reactor walls decreased current density, as did separating the electrodes with separators. High volumetric H production rate of 5.9 L/L/d was achieved at a volumetric current density of 970 A/m (34 A/m). Moreover, the observed current densities of the large reactor were accurately predicted based on the internal resistance analysis of small scale MECs (0.15 L), demonstrating the scalability of the single chamber MEC design.