In this study, ozone efficiency on the treatment of wastewater contaminated with high amounts of spent caustic (byproduct from hydrocarbons sweetening processes), is evaluated. The type of feedstock, pH, gas/liquid ratio and influence of catalyst use, are analyzed, in addition to the contact system used for the experiments. As a main conclusion, the feasibility of ozone in the treatment of industrial residues was established, especially in wastewater with high phenol contents.