Microbiological analyses in batch test for hydrogen production

The processes of anaerobic digestion and hydrogen production (dark fermentation) share many features, with the exception that to maximize hydrogen production, the methanogenic phase has to be reduced. The two processes of hydrogen production and methane production can be uncoupled by inhibiting the activity of methanogenic bacteria and maximizing the fermentative phase. To inhibit the methane producing microrganisms, thermal treatments can be carried out on the granular sludge, used as inoculum, at optimized temperatures and duration times according to the structure of the microbial community. The objectives of this research were a) the evaluation of the effects of heat treatments on the microbial community of the granular sludge in order to optimize the inoculum pre-treatment; b) to study the effect on the biogas and hydrogen productions of the heat treatment applied to the sludge. The applied thermal treatments strongly affected the microbial viability of inocula. A 2-to-4 hour treatment seems to be efficient for the selection of a microbial population that showed the best biogas and hydrogen performances. Fermentation experiments demonstrated that both hydrogen and biogas production increased as the time of heat treatments increased. The 4 hour pre-treated sludge showed the best specific and cumulative hydrogen productions.