Olive Washing Wastewater Treatment by Coagulation/Flocculation/Decantation and UV-A LEDs/Fenton †

Abstract

Olive washing wastewater (OWW) is generated before the olive oil extraction process in a preliminary step which consists of washing the olives with potable water. The discharge of OWW without suitable treatment can create serious environmental issues. Hence, in this work, a coagulation–flocculation–decantation (CFD) process was initially studied using ferrous sulfate, optimizing the operational conditions. Afterwards, the CFD process was combined with a UV-A LEDs/Fenton as pre- and post-treatment process, evaluating the use of the remaining ferrous ions in both situations. After finding the best operational conditions (CFD: natural pH, [Fe2+] = 3.60 mM, fast mixing = 150 rpm/3 min, slow mixing = 20 rpm/20 min, and 360 min of sedimentation; UV-A LEDs/Fenton: natural pH, [Fe2+] = 3.60 mM, [H2O2] = 116.4 mM, and 120 min of reaction) and combining both processes, the CFD followed by UV-A LEDs/Fenton allowed us to achieve the best removals: 91.0% of DOC, 97.5% of COD, 95.7% of turbidity, and 89.8% of TSS.