Optimization of Combined Ozone/Fenton Process on Olive Mill Wastewater Treatment

The aim of this study was to investigate the applicability of Fenton process and combined ozone/Fenton process to remove color, soluble chemical oxygen demand (CODs), phenol, and dissolved organic carbon (DOC) from real olive mill wastewater (OMW). The treatability of OMW was investigated in three different study parts. Initially, Fenton process was optimized under varying H2O2/Fe2+ molar ratios ranging between 10 and 20 at the constant H2O2 concentration of 0.5 mM. The H2O2/Fe2+ molar ratio of 10 was found optimum providing high color (51.6 %), CODs (58%), DOC (27.9%) and phenol removals (93.9%). Further, combined ozone/Fenton process was applied under gradually increasing dosages of Fe2+ and H2O2 reagents at constant H2O2/Fe2+ molar ratio of 10. The high color removal efficiency (51.6% color removal for Pt-Co) was obtained at the H2O2 and Fe2+ molar ratio of 0.5/0.05. Additionally, CODs, color, DOC and phenol removal efficiencies improved at increasing reagents concentrations. However, the color removal efficiency was adversely affected while no significant difference on CODs and phenol removal was observed at higher concentrations of molar concentrations above 0.5/0.05. Additionally, the results indicated that combined process enhanced treatment performance of OMW by 21%, 49% and 22% in terms of color, DOC and CODs removals, respectively, compared to only-Fenton process. In the rest of this study, combined ozone/Fenton process was optimized under varying ozonation time (60-120 min) at the optimum H2O2 and Fe2+molar dosage of 0.5/0.05 obtained from previous parts. Ozonation time significantly affected the treatment performance, and optimum the reaction time was determined as 90 minute in terms of the high treatment productivity and low operating cost resulted from minimum ozone consumption and short reaction time.