Temperature effects on biohydrogen production in a granular sludge bed induced by activated carbon carriers

Temperature effects on H 2 production performance of a novel carrier-induced granular sludge bed (CIGSB) reactor were investigated. Using sucrose-based synthetic wastewater as the feed, the CIGSB system was operated at 30– 45 ∘ C to identify the optimal working temperature. It was found that H 2 production was the most efficient at 40 ∘ C , especially when it was operated at a low hydraulic retention time (HRT) of 0.5 h. The overall maximal hydrogen production rate and yield were 7.66 l/h/l and 3.88 mol H 2 / mol sucrose, respectively, both of them occurred at 40 ∘ C . The biomass content tended to decrease as the temperature was increased, suggesting that granular sludge formation may be inhibited at high temperatures. However, increasing temperature gave better specific H 2 production rate, signifying that the average cellular activity for H 2 production may be enhanced as the temperature was increased. The H 2 yield and gas phase H 2 content did not vary considerably regardless of changes in temperature and HRT. This reflects that the CIGSB was a relatively stable H 2 -producing system. The major soluble products from hydrogen fermentation were butyric acid and acetic acid, accounting for 46 ± 3 % and 28 ± 2 % of total soluble microbial products (SMP), respectively. Thus, the dominant H 2 producers in the mixed culture belonged to acidogenic bacteria that underwent butyrate-type fermentation.