Abstract: A process is provided for the purification of water which is contaminated with environmentally undesirable components, such as halogenated hydrocarbons, wherein the contaminated water or the gaseous and/or liquid components present therein or derived therefrom are subjected to at least two of the following treatments: treatment with ozone, treatment of UV radiation, treatment with a solid catalyst. A combined treatment of ozone and a solid catalyst, such as activated carbon, is preferred. An apparatus for a co-current or countercurrent realization of the purification process is also provided.