Biological hydrogen production via dark fermentation by using a side-stream dynamic membrane bioreactor: Effect of substrate concentration

This study investigates the possibility of using dynamic membranes (DMs) as a solid-liquid separation medium for fermentative H-2 production under mesophilic conditions. In particular, the fouling behaviour of DM and H-2 production are studied in response to different influent COD concentrations (10-100 gCOD L-1). The results demonstrate that the influent feed concentration significantly affects the filtration behaviour of DM. In fact, the decrease in influent COD concentration determined an improvement of both DM permeability and solids separation. In addition, high influent COD concentration (above 30 g L-1) and resulting high organic loading rates, favoured the accumulation of volatile fatty acids (VFA), leading to the inhibition of bio-hydrogen production. The results, thus, demonstrated that stable DM filtration and H-2 production can be achieved by operating the bench-scale anaerobic DM bioreactor at low influent COD concentration (10-30 g L-1) and at an HRT of approximately 1 d. However, stable DM was achieved applying rather low filtration fluxes (approximately 2 Lm(-2) h(-1)).