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

Abstract

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 (COD s ), 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 H 2 O 2 /Fe 2+ molar ratios ranging between 10 and 20 at the constant H 2 O 2 concentration of 0.5 mM. The H 2 O 2 /Fe 2+ molar ratio of 10 was found optimum providing high color (51.6 %), COD s (58%), DOC (27.9%) and phenol removals (93.9%). Further, combined ozone/Fenton process was applied under gradually increasing dosages of Fe 2+ and H 2 O 2 reagents at constant H 2 O 2 /Fe 2+ molar ratio of 10. The high color removal efficiency ( 51.6% color removal for Pt-Co) was obtained at the H 2 O 2 and Fe 2+ molar ratio of 0.5/0.05. Additionally, COD s , color, DOC and phenol removal efficiencies improved at increasing reagents concentrations. However, the color removal efficiency was adversely affected while no significant difference on COD s 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 COD s 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 H 2 O 2 and Fe 2+ 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.