Increasing amount and number of resistant organics present in water and wastewaters and the increasing demand for advanced treatment have resulted in increasing use of chemical treatment processes. Chemical oxidation is the most effective process for the removal of organic pollutants present in water. Ozone is a very powerful oxidizing agent, which is able to participate in numerous reactions with organic and inorganic compounds. The role of ozonation and its related oxidation processes in the removal of organic compounds have been studied by different researchers. However, most of these studies have been conducted on systems that include single compound and also paid little attention to the influence of intermediates formed during the oxidation reactions on mechanism and chemical kinetics. In natural waters and wastewaters organic compounds cannot be found alone in the medium. Therefore for a better understanding the ozone oxidation process the removal pattern and kinetic evaluations of organics compounds should be analyzed as they exist alone and together within the aqueous medium. For this purpose phenol and bentazone was selected as model compounds to carry out the analysis mentioned above. Bentazone formulations are used as post-emergence herbicides for the control of broad-leaved weeds and Cyperaceae in a range of crops. Bentazone is not degraded after 120 days in either distilled water or WHO Standard Hard Water (FAO, 1991). Thus, bentazone was chosen as a model compound because it is commonly used as herbicide all over the world. Phenol and phenolic substances are abundantly present in wastewaters from agro-industries. Phenol is also considered to be an intermediate product in the oxidation pathway of higher molecular weight aromatic hydrocarbons. Thus it is usually taken as a model compound for treatment systems. In this respect, this study was devoted to analyze the ozone oxidation process for multiple substrate removal systems. The main objective of this study was to investigate the mechanism and kinetics of oxidation reactions of bentazone with molecular ozone when it exists individually or together with phenol in the aqueous medium under acidic conditions and in bubble column reactors. The parameters monitored were, organic compound removal, intermediate formation and removal, dissolved ozone concentration in the solution for an accurate evaluation of the kinetic behavior and the process of multiple substrate oxidation systems. Cis, cis-muconic acid and phenol were the intermediates monitored during the ozone oxidation of bentazone. For single bentazone oxidation experiments with initial concentrations of 25-100 mg/l, the peak concentration of phenol was ranged between 1.21- 5.70 mg/l while the peak values of cis, cis-muconic acid formed for all experiments were less than 1 mg/l. The peak dissolved ozone concentrations were ranged between 7.64 and 9.75 mg/l for experiments with initial bentazone concentrations of 50-100 mg/l. In single substrate oxidation systems of organic compounds, overall removal has found to fit firstorder model with respect to the organic compound concentration. Kinetic constants of single ozonation of bentazone have been found to range between 0.044-0.095 1/min at 3.0 mg/min ozone dosage. The kinetics and reaction pattern of bentazone in the multiple substrate oxidation systems were determined to be different from those of bentazone presents alone in the aqueous medium. This variation was considered to be due to the modification of reaction patterns by the interaction between the bentazone and phenol during their oxidation reactions, formation and oxidation of intermediates, as well as ozone transport limitations. In the mixture experiments a steady removal pattern was observed for both bentazone and phenol for all concentrations. Cis, cis-muconic acid was found to be the most important formed intermediate during the mixture oxidation experiments. The peak concentrations of cis, cis-muconic acid formed during the multiple substrate oxidation experiments increased with increasing initial phenol and bentazone concentrations. The peak concentration of cis, cis-muconic acid was ranged between 2.9-9.21 mg/l. The effect of dissolved ozone concentration in the mixture experiments was considered insignificant since it followed a close variation with those of single oxidation systems. The evaluation of the results showed that first-order model was also applicable for the oxidation of mixtures. However, the rate constant of bentazone was found always lower than those obtained for single oxidation kinetics. These changes in the rate constants were related to the accumulation of intermediates, particularly cis, cis-muconic acid.