Abstract <p>In the present study, the effects of the combination of electrooxidation (EOx) and ozone (O₃) processes on chemical oxygen demand (COD) removal and associated color removal and energy efficiency in the treatment of biologically treated vinasse are investigated. The results showed that hybrid technology is more effective than EOx and ozonation alone. The influence of operating parameters such as initial pH (5.0–9.0), operating time, current density (10.4–83.3 A/m²) and O₃ feed rate (2–5 mg/L) on percentage of color and COD removal as well as specific energy consumption and operating cost in the treatment of biologically treated wastewater was investigated. The COD removal percentage increased from 58.6 to 100% with an increase in current density from 10.4 to 83.3 A/m² when using a Nb boron-doped diamond-based electrode (Nb/BDD) after 4 h of operation. While complete color removal is observed after 4 h with the electrooxidation process alone, almost complete color removal is achieved in less than 3 h with the hybrid technique. The specific energy consumption and operating cost for the ozone-integrated electrooxidation process under optimal conditions were calculated to be 25.8 kW h/kg COD removed and $9.07/m³ respectively. Taking as a basis the operating costs of ozone-integrated electrooxidation, a slight raise of approximately 8% in the treatment costs were calculated with the electrooxidation alone process.</p>