Treatment of oilfield produced water with electrocoagulation: improving the process performance by using pulse current

The main aim of this study is to investigate the technical and economic feasibility of the pulse electrocoagulation (PE) process on the treatment of oilfield alkali/surfactant/polymer flooding produced water. By using an Fe electrode, the performance of the PE process was analyzed in terms of operating parameters such as pulse duty cycle, current density, pulse frequency, electrode distance, and reaction time with removal efficiencies, some of which are presented in figures and others are given in tables due to the numbers of parameters. Under the optimal conditions of a pulse duty cycle of 0.3, current density of 35 mA/cm 2 , pulse frequency of 3.0 kHz, electrode distance of 1.0 cm, and reaction time of 40 min, the removal efficiencies of chemical oxygen demand (COD), oils and greases, turbidity, total suspended solids, and polyacrylamide reach 98.3, 99.0, 98.8, 98.1 and 94.3%, respectively, with an energy consumption of 0.19 kWh/kg COD removed and an electrode consumption of 3.1 kg Fe/kg COD removed . The quality of the final effluent could satisfy the requirement of the national discharge standard. Compared with the traditional direct current method, the PE process could save 76% of the energy. Moreover, the treatment performance of PE is much better than traditional chemical coagulation treatment using polymeric ferric sulfate.