Methane production from whey in single-stage and two-stage anaerobic systems

Abstract

Exploring high-rate technologies in waste treatment could contribute to closing production cycles sustainably. The inadequate disposal of whey in receiving bodies can generate consequences such as contamination and eutrophication of the aquatic environment, thus affecting ecosystems. This work evaluated methane production from raw cheese whey in two anaerobic systems: a packed bed anaerobic reactor as the sole configuration and a system with phase separation (sequential stirred tank reactor, followed by a packed bed anaerobic reactor). As the sole configuration, the packed bed anaerobic reactor operated up to a stable volumetric organic load of 4 kg COD/m³d, achieving a chemical oxygen demand elimination of 91 % with a methane yield of 0.317 m³ CH₄/kg COD_e. Phase separation allowed a volumetric organic load of 27 kg COD/m³d to be reached in the stirred tank sequential reactor, allowing the same to be increased in the packed bed anaerobic reactor to 6 kg COD/m³d, obtaining chemical oxygen demand elimination efficiencies greater than 95 % and average CH₄ yields of 0.297 m³ CH₄/kg COD_e.