Treatment of oily wastewater by electrocoagulation: Simultaneous optimization of oil removal efficiency and specific energy consumption

Electrocoagulation (EC) is an effective process to treat oily wastewater. However, the optimal conditions required to design a continuous EC reactor are still unclear. In this study, an experimental and statistical investigation was performed on the factors affecting the design of a continuous EC reactor used for the removal of oily contaminants. By employing the response surface methodology (RSM), the oil removal efficiency and specific energy consumption (energy consumption per unit volume of treated wastewater) were modeled as a function of three factors, i.e. the current density (30–80 A/m2), the reactor residence time (10–30 min), and the ratio of the anode surface to the reactor volume (S/V ratio, 15–45 m2/m3). The statistical analysis of the experimental results unveiled the considerable impact of the effluent flow rate on the oil removal efficiency. Maximizing the oil removal efficiency and minimizing specific energy consumption were done simultaneously by combining them into an overall desirability function. The optimization results demonstrated that the energy required to treat a unit volume of the tested wastewater in an EC reactor is halved and the operating costs are reduced by 37 % at the cost of <2 % of the oil removal efficiency (from >99 % to 98 %) only by extending the residence time from about 16 to 28 min. The results of this research can pave the path to the development of an efficient and economical industrial EC unit used for the treatment of oily wastewater.