Hydrogen production from soft-drink wastewater in an upflow anaerobic packed-bed reactor

The production of hydrogen from soft-drink wastewater in two upflow anaerobic packed-bed reactors was evaluated. The results show that soft-drink wastewater is a good source for hydrogen generation. Data from both reactors indicate that the reactor without medium containing macro- and micronutrients (R2) provided a higher hydrogen yield (3.5 mol H2 mol−1 of sucrose) as compared to the reactor (R1) with a nutrient-containing medium (3.3 mol H2 mol−1 of sucrose). Reactor R2 continuously produced hydrogen, whereas reactor R1 exhibited a short period of production and produced lower amounts of hydrogen. Better hydrogen production rates and percentages of biogas were also observed for reactor R2, which produced 0.4 L h−1 L−1 and 15.8% of H2, compared to reactor R1, which produced 0.2 L h−1 L−1 and 2.6% of H2. The difference in performance between the reactors was likely due to changes in the metabolic pathway for hydrogen production and decreases in bed porosity as a result of excessive biomass growth in reactor R1. Molecular biological analyses of samples from reactors R1 and R2 indicated the presence of several microorganisms, including Clostridium (91% similarity), Enterobacter (93% similarity) and Klebsiella (97% similarity).

► H2 production from soft-drink wastewater in anaerobic packed-bed reactors is feasible. ► C:N:P 100:0.8:0.3 ratio presented 0.4 L H2 h−1 L−1 and 3.5 mol H2 mol−1 substrate. ► C:N:P 100:1.8:0.4 ratio presented 0.2 L H2 h−1 L−1 and 3.3 mol H2 mol−1 substrate. ► Elevated C:N ratio caused a change in the metabolic pathway and clogging of the bed. ► Bioreactor without nutrient supplementation showed continuous H2 production.