Improvement of biohydrogen production using a reduced pressure fermentation.

This study investigated the effect of reduced pressure on biohydrogen production in an upflow anaerobic sludge blanket (UASB) reactor from whey permeate. The results showed that the reduced pressure fermentation was more effective in enhancing biohydrogen production than dark fermentative hydrogen production at atmospheric pressure. Mesophilic fermentative biohydrogen production was investigated at a constant hydraulic retention time (HRT) of 24 h and increasing organic loading rates (OLRs) of 20, 25, 30, 35 kg COD/m(3) day. The reduced pressure fermentation was successfully operated at all OLRs tested. The maximum proportion of hydrogen in biogas of 47.7 %, volumetric hydrogen production rate (VHPR) of 7.10 L H2/day and hydrogen yield of 4.55 mol H2/kg COD removed occurred at the highest OLR. Increase in OLR affected the hydrogen production in UASB reactor exploited at atmospheric pressure. The reduced pressure process was able to remarkably improve the biohydrogen performance at high OLRs.