Nonionic Triton X-100 surfactant was photocatalytically oxidized in an aq. soln. (initial concn. 125 and 250 mg/dm(3)) in a flat poly(methyl metacrylate) reactor in presence of coarse SiO2-supported TiO2 (10%) under UV and visible light ir-radn. (Hg lamp 125 IN or 150 W supported with 4 glow-di-scharge tubes 6 IN each). The reactor was operated either in batch mode or in flow mode with recirculation. The process course was followed by actinometry and detn. of chem. O demand and total org. C. The highest decrease in the parameters was achieved when all light sources were simultaneously used. After 5-fold recirculation of the studied soln. (or after 20 h long its treatment in the batch reactor), the decrease in total org. C was 50%, in chem. O demand about 60% and in absorbance 65%. The energy consumption was however high under the process conditions (about 27 kJ/mg C and about 2.6 kJ/mg O for initial surfactant concn. 125 mg/dm(3)).