Impact of organic loading rate on biohydrogen production in an up-flow anaerobic packed bed reactor (UAnPBR)

This study assesses the impact of organic loading rate on biohydrogen production from glucose in an up-flow anaerobic packed bed reactor (UAnPBR). Two mesophilic UAPBRs (UAnPBR1 and 2) were tested at organic loading rates (OLRs) ranging from 6.5 to 51.4 gCOD L−1 d−1. To overcome biomass washout, design modifications were made in the UAnPBR2 to include a settling zone to capture the detached biomass. The design modifications in UAnPBR2 increased the average hydrogen yield from 0.98 to 2.0 mol-H2 mol−1-glucose at an OLR of 25.7 gCOD L−1 d−1. Although, a maximum hydrogen production rate of 23.4 ± 0.9 L H2 L−1 d−1 was achieved in the UAnPBR2 at an OLR of 51.4 gCOD L−1 d−1, the hydrogen yield dropped by 50% to around 1 mol-H2 mol−1-glucose. The microbiological analysis (PCR/DGGE) showed that the biohydrogen production was due to the presence of the hydrogen and volatile acid producers such as Clostridium beijerinckii, Clostridium butyricum, Megasphaera elsdenii and Propionispira arboris.