A two stages electrocatalytic method for oxidative-purification of wastewater from soluble substances, such as toxic chemical admixtures difficult of oxidation, including dye-stuffs, detergents, phenols, cyanides and the like, which stages inactivate the soluble substances present in the wastewater in a synergistic fashion and, therefore, are highly efficient, the method comprising the steps of (a) in a first stage, electrochemically treating the wastewater in the presence of chlorine ions, such that chlorine-containing oxidizing agents are formed and at least partially oxidize the soluble substances in the wastewater; and (b) in a second stage, catalytically treating the first stage treated wastewater in presence of a non-chlorine oxidizing agent and an added catalyst, such that remainings of the soluble substances are further oxidized, and such that the chlorine-containing oxidizing agents formed during the first stage are catalytically reduced; wherein, the first stage and the second stage act synergistically to purify the wastewater from the soluble substances.