Degradation of Phenolic Compounds and Organic Matter from Real Winery Wastewater by Fenton and Photo-Fenton Processes Combined with Ultrasound

Abstract

Real winery wastewater (WW), with a high concentration of organic matter (OM), was treated using Fenton (FP), photo-Fenton (PFP), sono-Fenton (SFP), and sono-photo-Fenton processes (SPFP), with the primary objective of removing phenolic compounds (PhCs). Although beneficial to human health, these compounds are considered recalcitrant and toxic to aquatic organisms, posing significant environmental risks if discharged into water bodies. They can also reduce the efficiency of biological treatment processes. After physicochemical characterization and two hours of treatment, the removal efficiencies achieved by the FP, PFP, SFP, and SPFP processes were 29.35%, 41.30%, 28.82%, and 33.95% for PhCs; 27.88%, 31.51%, 23.19%, and 29.29% for chemical oxygen demand (COD); and 12.53%, 13.92%, 9.28%, and 10.62% for dissolved organic carbon (DOC), respectively. The degradations achieved by SFP and SPFP were lower than those of FP and PFP, respectively, due to reactions that scavenge hydroxyl radicals. Treatment of a gallic acid (GA) solution, used as a model compound for PhCs, exhibited similar trends, indicating that the lower efficiency in processes involving ultrasound is not due to the OM in the effluent, but rather the interaction between ultrasound (US) and H2O2, which reduces hydroxyl radical concentration. However, under the conditions of the wastewater used, the technologies applied did not completely reduce the parameters analyzed, being recommended as pre- or post-treatment, and combined with other processes.