Treating industrial wastewater by advanced oxidation processes, is a recent interest primarily for decolorization of aqueous solutions containing dyes. The application of the Fenton reaction is one of these processes, bleaching liquid discharges after a textile dyeing unit in the city of Marrakech, Morocco, which are non-biodegradable, using oxidation by Fenton's reagent has shown its ability to degrade the dyes in water to carbon dioxide, water, and other harmless products. In this study a serie of pure dyes mineralization experiments used in the dyeing process, such as: the Bezaktiv BLUE-SR, the NOVACRON® Red FN-R, and the NOVACRON®SCALE TFN-6G, and a global liquid discharge containing dyes and chemical additives. Fenton's method is effective at pH = 3, as a result, we had a total discoloration for the three pure colors, and up to 47% to the overall rejection for 60 minutes at room temperature, and 100%  when the temperature was increased to 60 °C. The presence of chemical additives disadvantage Fenton oxidation.