A comparative study was performed to evaluate the removal efficiency of herbicide, oxadiazon as an organic contaminant in treatment processes for drinking water. In this investigation, three major treatment processes such as chlorination, ozonation and activated carbon treatment were applied separately to water system. The level of oxadiazon gradually decreased to 28%, when chloride as a disinfectant was applied to the water supply. Activated carbon treatments showed that this herbicide was removed efficiently from the aqueous solution. The results indicated that the performance of powdered activated carbon was more effective than granular activated carbon in terms of adsorption. The adsorption isotherms exhibited an excellent agreement with the experimental data and they were also well represented by the Langmuir and Freundlich equations, indicating the higher adsorption capacity for activated carbons. During ozone treatment, 50% of oxadiazon was removed but this removal was enhanced by the presence of hydrogen peroxide. The association of ozonation with chloride and activated carbon treatments was considered to be the best-tested treatment for drinking water production. Therefore, if oxadiazon enters into the water ecosystem as an organic contaminant, it could be removed effectively by the drinking water treatment processes.