Recovery of Volatile Fatty Acids from an Olive MillSolid Waste Ferment via Electrodialysis: A Comparative Study withSynthetic Mixtures

Abstract Electrodialysis has emerged as a sustainable technology for volatile fatty acids (VFAs) separation from organic streams, valued for its quick, efficient separation, low energy use, and minimal membrane pressure. This study explores the feasibility of the purification of VFAs from an olive mill solid waste (OMSW) ferment in comparison with a synthetic VFA mixture, evaluating the potential matrix effect of the OMSW ferment. The electrodialysis demonstrated to be partially effective in the extraction of VFAs from OMSW ferment, achieving a total VFA recovery of 55%. Comparing this recovery with the synthetic VFA mixture (recovery of 60%), it could be concluded that the matrix effect has a negligible impact on VFA recovery percentage, although it slightly decelerates the process. The initial concentration and molecular weight of each VFA compound influenced their specific recovery percentage as well as the migration rates, resulting in the higher efficiencies for acetic acid, between 58 and 73%. Respect to the VFA flow capacity to treat, energy consumption, and current efficiency of the OMSW ferment in the electrodialysis stack, the values of 8.7 g VFA·m–2·h–1, 0.97 kWh·m–3, and 86% have been obtained, respectively. In general, energy consumption mainly depends on the operational conditions (applied voltage), the percentage of VFA recovery (operating time), and the stream characteristics (electrical conductivity).