Biohydrogen Production as a Function of pH and Substrate Concentration

TLDR

The conversion of organics in wastewater into hydrogen gas could serve the dual role of renewable energy production and waste reduction. The study aimed to recover the chemical energy of a sucrose‑rich synthetic wastewater as hydrogen gas. Using a fractional factorial design, batch experiments varied pH (4.5–7.5) and substrate concentration (1.5–44.8 g COD L⁻¹) with mixed bacterial cultures from compost, potato, and soybean fields that were heat‑treated to suppress methanogens and enrich sporeforming acidogens. The maximum hydrogen production rate was 74.7 mL H₂ (L h)⁻¹ at pH 5.5 and 7.5 g COD L⁻¹, yielding a conversion efficiency of 38.9 mL H₂ (g COD L⁻¹), with the highest observed efficiency reaching 46.6 mL H₂ (g COD L⁻¹).

Abstract

The conversion of organics in wastewaters into hydrogen gas could serve the dual role of renewable energy production and waste reduction. The chemical energy in a sucrose rich synthetic wastewater was recovered as hydrogen gas in this study. Using fractional factorial design batch experiments, the effect of varying pH (4.5−7.5) and substrate concentration (1.5−44.8 g COD/L) and their interaction on hydrogen gas production were tested. Mixed bacterial cultures obtained from a compost pile, a potato field, and a soybean field were heated to inhibit hydrogen-consuming methanogens and to enrich sporeform ing, hydrogen-producing acidogens. It was determined that the highest rate (74.7 mL H2/(L*h)) of hydrogen production occurred at a pH of 5.5 and a substrate concentration of 7.5 g COD/L with a conversion efficiency of 38.9 mL H2/(g COD/L). The highest conversion efficiency was 46.6 mL H2/(g COD/L).