The effectiveness of different ozone-based advanced oxidation processes on the treatment of 1,4-dioxane in aqueous solution was investigated in a lab-scale reactor. The removal efficiency of 1,4-dioxane was studied under different initial pH and H₂O₂ concentrations. Degradation (18%) of COD was observed with the application of UV-C alone, but the degradation of COD was greatly enhanced by a combined method, O₃/H₂O₂/UV (94%). It appears, however, that an excess amount of hydrogen peroxide in the solution retards the decomposition of 1,4-dioxane. At pH 10 and an H₂O₂/O₃ ratio of 0.5, 1,4-dioxane in aqueous solution showed the highest degradation rate.