Optimization of hydrogen production in a granule-based UASB reactor

Hydrogen production from sucrose in a granule-based upflow anaerobic sludge blanket (UASB) reactor was optimized through employing response surface methodology (RSM) with a central composite design in this study. The individual and interactive effects of influent sucrose concentration (Sin) and hydraulic retention time (HRT) on anaerobic hydrogen production were elucidated. Experimental results show that a maximum hydrogen yield of 1.62 mol-H2/mol-hexose was obtained under the optimum conditions of Sin 14.5 g/L and an HRT 16.4 h. The hydrogen yield was individually dependent on Sin and HRT, while their interactive effect on the hydrogen yield was not significant. Throughout the experiments the hydrogen content fluctuated between 25.9% and 50.0%, but free of methane. Ethanol, acetate and butyrate were the main aqueous products and their yields all correlated well with Sin and HRT, indicating a mixed-type fermentation in this UASB reactor.