Influence of Organic Load on Biohydrogen Production in an AnSBBR Treating Glucose-Based Wastewater

An anaerobic sequencing batch reactor with immobilized biomass (AnSBBR) was applied to the production of biohydrogen treating a glucose-based wastewater. The influence of the applied volumetric organic load was studied by varying the concentration of influent at 3600 and 5250 mg chemical oxygen demand (COD) L(-1) and cycle lengths of 4, 3, and 2 h resulting in volumetric organic loads of 10.5 to 31.1 g COD L(-1). The results revealed system stability in the production of biohydrogen and substrate consumption. The best performance was an organic removal (COD) of 24 % and carbohydrate removal (glucose) of 99 %. Volumetric and specific molar productivity were 60.9 mol H2 m(-3) day(-1) and 5.8 mol H2 kg SVT(-1) day(-1) (biogas containing 40 % H2 and no CH4) at 20.0 g COD L(-1) day(-1) (5250 mg COD L(-1) and 3 h). The yield between produced hydrogen and removed organic matter in terms of carbohydrates was 0.94 mol H2 Mol GLU(-1) (biogas containing 52 % H2 and no CH4) at 10.5 g COD L(-1) day(-1) (3600 mg COD L(-1) and 4 h), corresponding to 23 and 47 % of the theoretical values of the acetic and butyric acid metabolic routes, respectively. Metabolites present at significant amounts were ethanol, acetic acid, and butyric acid. The conditions with higher influent concentration and intermediate cycle length, and the condition with lower influent concentration and longer cycle showed the best results in terms of productivity and yield, respectively. This indicates that the best productivity tends to occur at higher organic loads, as this parameter involves the biogas production, and the best yield tends to occur at lower and/or intermediate organic loads, as this parameter also involves substrate consumption.