Assessment of a pilot-scale electrooxidation system for enhanced phenol removal from petroleum refinery wastewater streams

Abstract This study demonstrates the successful scale-up of an electro-oxidation (EOX) system for phenol removal from petroleum refinery wastewater, transitioning from laboratory validation to pilot-scale operation. The optimized system, comprising ten parallel reactors with graphite anodes and stainless-steel cathodes, achieved exceptional treatment efficiency across two distinct wastewater streams. During continuous 3-month operation, the system removed 99.9% of phenol at 10 V within 20 min retention time, while simultaneously reducing COD by 50%, BOD by 45–49%, and oil content by 35–50% with initial concentrations of 248 mg/L, 84 mg/L and 13 mg/L, respectively. Performance assessment revealed optimal operation at current densities of 4–6 A/m², with energy consumption averaging 0.45 kWh/m³ for high-TDS streams (1800 mg/L) and 0.25 kWh/m 3 for lower-TDS streams (1025 mg/L). Economic analysis showed favorable operating costs of 120–150 kWh per kg of phenol removed, with minimal electrode degradation (< 5% weight change after 3 months).The total operating cost was 0.13–0.15 $/m 3 including electricity (0.11$/m 3 ), electrode depreciation (0.05$/ m 3 ), maintenance and cleaning ( 0.08 $/m 3 ) and flow pumping (0.02$/m 3 ). The system maintained stable performance across varying wastewater conditions (pH 6.8–10.3, temperature 21–22 °C), demonstrating its robustness for industrial applications. These findings establish the technical and economic viability of EOX technology for full-scale implementation in petroleum refineries, offering both high removal efficiency and cost-effective operation compared to conventional treatment methods.