NOVELTY - The method for treating photoresist-containing effluents, which occur with photolithographic process steps, such as in the production of printed circuit boards, solar cells by UV light. The wastewater is irradiated in the presence of an oxidizing agent and a transition metal cation with the UV-light and a solid material is formed form the wastewater that contains a part of the photoresist and the part of transition metal. The oxidizing agent is hydrogen peroxide, and is partially added to the wastewater before the irradiation with UV-light. The transition metal cation comprises a cation.    USE - The method is useful for treating photoresist-containing effluents.    ADVANTAGE - The method is capable of having simple and effective treatment of photoresist-containing effluents.    DETAILED DESCRIPTION - The method for treating photoresist-containing effluents, which occur with photolithographic process steps, such as in the production of printed circuit boards, solar cells by UV light. The wastewater is irradiated in the presence of an oxidizing agent and a transition metal cation with the UV-light and a solid material is formed form the wastewater that contains a part of the photoresist and the part of transition metal. The oxidizing agent is hydrogen peroxide, and is partially added to the wastewater before the irradiation with UV-light. The transition metal cation comprises a cation of copper or iron, and is added to the wastewater in form of a transition metal salt. The wastewater contains a negative photoresist. The irradiation is carried out with the UV-light in an UV-reactor, which comprises a UV-radiator, which is arranged in a quartz glass tube. The formed solid material is cleaned by the surface area of the quartz glass envelope in a purification step, which is carried out by an acid or an acid solution. The acid is a polybasic organic acid. The purification step is carried out in discontinuous manner after the method of treatment or during an interruption of the method of treatment. An INDEPENDENT CLAIM is included for a cleaning agent for cleaning a solid material.