Treatment of hydraulic fracturing flowback water using the combination of gel breaking, magnetic-enhanced coagulation, and electrocatalytic oxidation

A combined process of magnetic-enhanced coagulation (MEC)-electrocatalytic oxidation (EO) was developed at lab scale for treating a real hydraulic fracturing flowback water with an initial chemical oxygen demand (COD) of 4230 mg/L, a viscosity value of 14.6 mPa center dot s, and a suspended solid (SS) concentration of 2890 mg/L. The results show that, under the optimum conditions, the removal efficiencies of COD and SS were averagely 97.8% and 99.3%, respectively, and the quality of final effluent can meet the national discharge standard of China. K2FeO4 could efficiently reduce the wastewater viscosity, which was beneficial for the subsequent processes. The MEC process removed a considerable proportion of organic matter and SS, while the EO played an important role in post-polish of final effluent. This work demonstrates that the hybrid system has the potential to be applied for the advanced treatment of high-strength oil/gas fracturing wastewater.