Biohydrogen production in pilot-scale fermenter: Effects of hydraulic retention time and substrate concentration

Systematic investigation of the effects of hydraulic retention time and substrate concentration on biohydrogen production rates in pilot-scale fermenter is of great academic and practical interests. The present study applied a 3 m³ pilot-scale bioreactor that composed of three sequential 1 m³ chambers (#1-#3) to investigate the effects of hydraulic retention time and substrate concentration on biohydrogen production rates from glucose. The 48 h hydraulic retention time resulted in poor mixing of the medium; chamber #1, which received the feed substrate, converted too much glucose, and little glucose was left to be utilized in the following chambers. However, a 12 h hydraulic retention time allowed insufficient volatile fatty acids to be produced, so a reductive environment for biohydrogen production was difficult to establish. At the optimal hydraulic retention time, 24 h for the present fermenter, sufficient mixedness of the medium and fermentation times for all chambers maximized the biohydrogen production rates. Biohydrogen production rates were increased as the substrate concentration was increased from 10 to 30 g/L, peaked at 100.16 mol/m³-d, and then decreased with the increase in substrate concentration. Unique in the literature, the reported data reveal the effects of substrate concentration on biohydrogen production rates in pilot-scale fermenter, guiding to the design and development of the pilot-scale bioreactors with high hydrogen yields that could help to improve the industrialization development of biohydrogen production.