Laboratory study on shale gas flowback water treatment applying electrochemical oxidation coupled with magnetic separation

Through analysis on composition, characteristics, and current treatment options of flowback water arising from slick water using for shale gas fracturing, as well as drilling site survey and state regulations on water resource utilization and environmental protection, this paper proposed treatment process with electrochemical oxidation followed by magnetic separation. Experiments have been conducted to identify the main factors influencing the treatment processes, discussing the function mechanisms of the electrochemical oxidation, and finally achieving the optimum operating conditions. In details, aluminum plate was chosen as electrodes with plate spacing at 4 cm; the catalyst was titanium dioxide with contents equivalent to 3.0%(w); the processing time, electric current of catalytic oxidation processing, and the current frequency were determined to be 40 min, 0.06 A, 1 800 Hz, respectively. Besides, in the magnetic separation process, the dosage of magnetic power and flocculant HPAM was 0.3%(w) and 20 mg/L. Results showed that by applying the proposed treatment process, COD, SS, oil & grease contents, chroma, pH, and other major water quality parameters could meet the first category integrated wastewater discharge standard (GB 8978-1996).