Treatment of olive mill wastewater by a combined process: Fenton's reagent and chemical coagulation

Olive mill wastewater (OMW) was exposed to Fenton treatment and subjected to post Fenton coagulation/flocculation using lime. Several tests were performed for different R = H2O2/COD ratios, from 0.25 to 3.0, promoting the gradual addition of H2O2 and Fe2+, with the original condition of a pH = 3.5 and maintaining a constant relationship H2O2/Fe2+ = 15. A maximum reduction of COD of 96.8% was obtained using Fenton reagent with R = 3.0. In a second phase, the effluent which was neutralized with Ca(OH)2 reached a higher reduction of COD, achieving a final degradation value of 99.3%. Overall, the results show evidence of the potential value of applying the combined process tested.