Optimization of Electrocoagulation Conditions for the Purification of Table Olive Debittering Wastewater Using Response Surface Methodology

In the present study, the optimization of electrocoagulation (EC) conditions for the purification of olive debittering wastewater (ODW) was investigated by response surface methodology (RSM). For this purpose, a central composite design (CCD) was employed to optimize the process variables including current density (3.0–30.0 mA/cm²) and EC time (10.0–60.0 min). The results showed a significant effect of current density and EC time on the removal efficiency of total phenolic compounds (TPC) and chemical oxygen demand (COD). The best models obtained using the central composite design were quadratic polynomial for TPC (R² = 0.993), COD (R² = 0.982), and the inverse square root of turbidity (R² = 0.926). Additionally, the square root of electrode consumption and energy consumption were appropriately fitted to the two-factor interaction (2FI) model (R² = 0.977) and quadratic polynomial (R² = 0.966) model, respectively. The predicted optimum conditions based on the highest removal efficiency for TPC were a current density of 21.1 mA cm⁻² and an EC time of 58.9 min, in which the obtained model predicted 82.6% removal for TPC. This prediction was in agreement with the laboratory result (83.5%). The amount of energy consumption and the operating cost in these conditions was estimated to be 14.92 kWh and USD 6.49 m⁻³ per ODW, respectively.