Effect of Fermentation Time, pH, and Their Interaction on the Production of Volatile Fatty Acids from Cassava Wastewater

Abstract

Acidogenic fermentation is a technology that involves halting methanogenesis in the conventional anaerobic digestion process to produce mainly volatile fatty acids (VFAs). VFAs serve as direct precursors to energy-rich or higher value-added products upon undergoing additional processing. In this study, batch reactors were utilized to assess the individual and interaction effects of fermentation time and pH variables on VFA production from acidogenic fermentation of cassava wastewater through the establishment of a completely randomized design and a second-order response surface (rotatable central composite design), respectively. The maximum VFA production observed was 3444.04 mg of acetic acid (HAc)/L (0.58 gCODVFA/gCOD) in a fermentation time of 6 days, with acetic (48.5%), propionic (28.3%), and butyric (13.6%) acids identified as the main metabolites. Additionally, in the assessment of the effect of pH, the maximum VFA production reached 2547.72 mgHAc/L (0.34 gCODVFA/gCOD) at pH 5.9, and acetic acid was identified as the predominant organic acid. Statistically, the fermentation time and pH variables individually affect VFA production from cassava wastewater; however, the interaction between them generated a non-significant effect.