Effect of illumination on the hydrogen-production capability of anaerobic activated sludge

To investigate the influence of illumination on the fermentative hydrogen production system, the hydrogen production efficiencies of two kinds of anaerobic activated sludge (floc and granule) from an anaerobic baffled reactor were detected under visible light, dark and light-dark, respectively. The 10 mL floc sludge or granular sludge was respectively inoculated to 100 mL diluted molasses (chemical oxygen demand of 8000 mg·L^?1) in a 250 mL serum bottle, and cultured for 24 h at 37°C under different illumination conditions. The results showed that the floc was more sensitive to illumination than the granule. A hydrogen yield of 19.8 mL was obtained in the dark with a specific hydrogen production rate of 3.52 mol·kg^?1MLVSS·d^?1 (floc), which was the highest among the three illumination conditions. Under dark condition, the hydrogen yield of floc sludge reached the highest with the specific hydrogen production rate of 3.52 mol·kg^?1MLVSS·d^?1, and under light-dark, light, the specific hydrogen production rate was 3.11 and 2.21 mol·kg^?1MLVSS·d^?1, respectively. The results demonstrated that the illumination may affect the dehydrogenase activity of sludge as well as the activity of hydrogen-producing acetogens and then impact hydrogen production capacity.