Winery wastewater treatment by sulphate radical based-advanced oxidation processes (SR-AOP): Thermally vs UV-assisted persulphate activation

Abstract

Winery wastewater is characterized by the presence of organic and inorganic contaminants with significant environmental impact if released without proper treatment. Thus, the application of sulphate radical-based advanced oxidation processes (SR-AOP) in winery wastewater treatment, with emphasis on the removal of organic matter, has been investigated. Several experiments were performed to assess the influence of temperature, UV-C radiation and transition metals in the thermal and photolytic/photocatalytic activation of sodium persulphate.COD removal was higher in the UV-C/S2O82- process than in the heat/S2O82- using an initial COD concentration of 600 mg O2 L-1. After a reaction time of 90 min (at pH = 7.0), using 15 mM of S2O82- driven by a UV-C lamp allowed achieving 59% of COD removal while the heat/S2O82- process attained a removal of only 41%. Afterwards, combining the thermal activation with transition metals, and using the optimal operational conditions ([S2O82-]/[Cu2+] = 1, pH = 7.0 and 90 min of reaction time), 61% of COD removal was obtained.Additional experiments with higher S2O82- concentrations and longer reaction time led to 96% and 71% of COD and TOC removal, respectively. To attain this target was used 25 mM of S2O82-, at pH 7.0 during a reaction time of 240 min. This removal rate proved to be higher than the achieved with hydroxyl radical-based advanced oxidation processes (HR-AOPs). Under the same optimal conditions, using 25 mM of H2O2 achieved 22% of COD removal and UV-C/Fe2+/H2O2 experiments obtained 48%.Overall, SR-AOP experiments, particularly UV-C assisted processes, have proven to be very effective in COD removal and can be seen as a promising technology to use in winery wastewater treatment.