Biofilm formation on granular activated carbon in xylose and glucose mixture for thermophilic biohydrogen production

Granular activated carbon (GAC) was used as a support carrier to develop biofilm of Thermophilic biohydrogen producer in an immobilized system of dark fermentation. The optimum ratio of the sludge to GAC loading was investigated in batch fermentation using glucose and xylose mixture as a carbon source. It was found that the highest hydrogen yield of 1.77 mol H2/mol substrate consumed and hydrogen production rate (HPR) of 2.0 mmol H2/l.h, were achieved at a sludge-GAC ratio of 1:2. On the other hand, the experiments with suspended culture as a control gave poor performance of hydrogen yield (0.86 mol H2/mol of substrate consumed) and HPR (0.5 mmol H2/l.h). The sludge-GAC biofilm was further developed in a sequencing batch feeding mode through controlled acclimatization condition. Stable hydrogen production was achieved after day 40th with consistent HPR of 2.4 mmol H2/l.h and yield of 1.17 mol H2/mol substrate consumed with 44.2% of hydrogen. Acetic and butyric acids dominate volatile fatty acids (TVFAs) as a major by-product while ethanol being the only alcohol produced but in a minor amount. This work has proven the possible future of GAC attached biofilm sludge as promising attachment system to achieve consistent hydrogen production even at thermophilic conditions.