The treatment of persistent organic pollutants in wastewater from chemical factories by decomposition using advanced oxidation processes (AOPs) has recently been studied. However, the AOPs studied to date suffer from problems such as high running costs for ozone generation and difficulties with operational parameters in the addition of hydrogen peroxide. In this study, a compact AOP reactor that generates ozone by UV irradiation was developed. Ozone was generated using the Chapman method, i.e., by irradiating oxygen with UV light; the use of this method saves energy. The decomposition activity of the designed reactor and the effects of a combination of ozone, UV, and TiO2 were examined. The results showed that 100% decomposition of 50 mg/dm3 phenol was reached within 120 min using an O3–UV–TiO2 process, and COD removal reached 100% within 240 min. COD analysis confirmed that a synergistic effect was obtained using ozone, UV, and TiO2 simultaneously.