Drilling mud wastewater is one of Hazardous and Toxic Substance from drilling activities by oil-gas company contain by phenol, H2S (dissolved sulfide) and COD with concentration 43,3 mg/L; 7,332 mg/L and 3400 mg/L. In this research is using Advanced Oxidation Processes (AOPs) ozone based with oxidation potential value 2,08 eV. Ozonation is performed by injecting ozone on reactor with continious…