The invention relates to a method, devices and reagents which are used for Fenton reaction-based wastewater treatment. According to the invention, the oxidation reaction of the organic material with the oxygenated water is performed in the main oxidation reactor (12) in the presence of metallic catalysts. The Fenton reaction takes place in the reactor at absolute pressure of between 1 Kg/cm.sup.2 and 1.5 Kg/cm.sup.2 and at a temperature of between 110.degree. C. and 120.degree. C. Once treated and cooled, the effluent is conveyed to zone D to a neutralising tank (6) in which the pH is increased to a value greater than seven, thereby causing precipitation of the hydroxides. In addition, safety checks are carried out automatically.