Optimizing hydrogen production from organic wastewater treatment in batch reactors through experimental and kinetic analysis

Anaerobic hydrogen production from organic wastewater, an emerging biotechnology to generate clean energy resources from wastewater treatment, is critical for environmental and energy sustainability. In this study, hydrogen production, biomass growth and organic substrate degradation were comprehensively examined at different levels of two critical parameters (chemical oxygen demand (COD) and pH). Hydrogen yields had a reverse correlation with COD concentrations. The highest specific hydrogen yield (SHY) of 2.1 mole H2/mole glucose was achieved at the lowest COD of 1 g/L and decreased to 0.7 mole H2/mole glucose at the highest COD of 20 g/L. The pH of 5.5–6.0 was optimal for hydrogen production with the SHY of 1.6 mole H2/mole glucose, whereas the acidic pH (4.5) and neutral pH (6.0–7.0) lowered the hydrogen yields. Under all operational conditions, acetate and butyrate were the main components in the liquid fermentation products. Additionally, a comprehensive kinetic analysis of biomass growth, substrate degradation and hydrogen production was performed. The maximum rates of microbial growth (μm) and substrate utilization (Rsu) were 0.03 g biomass/g biomass/day and 0.25 g glucose/g biomass/day, respectively. The optimum pH for the rate of hydrogen production (RH2RH2) and SHY were 5.89 and 5.74 respectively. Based on the kinetic analysis, the highest RH2RH2 and SHY for batch-mode anaerobic hydrogen production systems were projected to be 13.7 mL/h and 2.32 mole H2/mole glucose.