Simultaneous production of bio-hydrogen and methane from soybean protein processing wastewater treatment using anaerobic baffled reactor (ABR)

Bio-hydrogen (H₂) and methane (CH₄) co-production from soybean protein processing wastewater (SPPW) was examined using a four-compartment anaerobic baffled reactor (ABR) with the active reactor volume (34 L) under continuous flow condition in this present study. At steady state, the ABR achieved H₂ yields of 25.67 L/d, specific hydrogen production rate of anaerobic activated sludge was 0.28 L/g MLVSS d, CH₄ yields of 13.89 L/d, and chemical oxygen demand (COD) removal of 95% when operated at the organic loading rate of 1.9–2.6 kg COD/m³ d, hydraulic retention time of 48 h, and temperature of (35 ± 1) °C, respectively. The results showed that the niches of the bio-hydrogen-producing phase and the methane-producing phase in the ABR are different. A high alkalinity in the methanogenic compartment of the ABR was able to secure the pH neutral and methane generation. In general, the ABR proved to be a stable, reliable, and effective process for energy recovery and stabilization treatment of SPPW.