Biohydrogen production using waste activated sludge as a substrate from fructose-processing wastewater treatment

Abstract

Biohydrogen production by dark fermentation in a series of batch tests under different environmental control conditions was evaluated to determine the optimal initial cultivation pH and temperature for a continuous-flow kinetic test to validate the kinetic model system. The waste activated sludge (WAS) from fructose-processing manufacturing was used as the model substrate for biohydrogen production. The batch experiments for biohydrogen production were conducted in a 6l bioreactor. Fifteen batch kinetic tests were investigated when pH was controlled at 6, 7, 8 and 9 as well as the temperature was controlled at 37°C, 45°C and 55°C, respectively. The experimental results indicated that the optimal operational condition for hydrogen production occurred while pH was 7 and temperature was 55°C with the highest hydrogen production of 7.8mmol. The optimal recovery time for hydrogen was 25h in the batch experiments. Furthermore, the kinetic test of biohydrogen production was performed by anaerobic mixed microbial culture in the continuous-flow experiment when pH and temperature was maintained at 7 and 55°C. Approximately 60% and 7% of substrate solution was converted into acetate and hydrogen, respectively, at the steady state. Roughly only 0.77% and 2.7% of substrate solution was converted into propionate and butyrate, respectively, at a steady-state condition. The experimental and modeling approaches presented in this study could be employed for the design of pilot-scale and full-scale anaerobic biohydrogen fermentors using food-processing waste activated sludge (WAS) as a substrate solution.