Optimizing the removal of COD and Phenolic compounds from olive mill wastewater by Fenton oxidation using experimental design

The production of olive oil, leads to the co-production of large quantities of olive mill wastewater (OMW). This waste has a high polluting power as well as a high antibacterial activity exerted, among others, by various phenolic compounds. In this study, the Fenton process using hydrogen peroxide (H 2 O 2 ) as oxidant and ferrous ions (Fe 2+ ) as catalyst was used to treat OMW. Box–Behnken design (BBD) based on the response surface methodology (RSM) was adopted to evaluate the effects of concentration [H 2 O 2 ], concentration [Fe 2+ ] and reaction time on the chemical oxygen demand (COD) removal, phenolic compounds (PC) removal and the residual H 2 O 2 level remaining in the solution. According to the Analysis of Variance (ANOVA), the three quadratic models that were developed using multiple regression analysis were reliable and successfully fit the experimental data with a high coefficient of determination R 2 ranging from 0,9969 to 0,9999. Optimal operating conditions based on the desirability function methodology were found to be [H 2 O 2 ] = 13,79g/l (0,4mol/l), [Fe 2+ ] = 0,55g/l (0,01mol/l) and reaction time = 5,73h. Under the values of these variables, COD removal of 88,70% and PC removal of 84,26% with no residual H 2 O 2 were predicted with a desirability value of 1.