ELECTROCHEMICAL TREATMENT OF OILFIELD PRODUCED WATER
M. I. Panayotova, N. N. Mintcheva, L. P. Djerahov, G. D. Gicheva, V. T. Panayotov
Pages: 425-440 Published: 20 Dec 2017
Views: 906 Downloads: 303
Abstract: Oil production generates wastewater bearing oily hydrocarbons, referred to “produced water” (PW). PW from a heavy-oil field has been treated with stainless steel (SS) cathode and dimensionally stable anodes – passivated titanium and graphite. In the electrolytic cells with these electrodes, electrooxidation (EO) accompanied by electroflotation (EF) are the main processes leading to pollutants removal. An oxidation by in situ generated oxidizing agents is found as the most plausible mechanism for decomposition of oily hydrocarbons in the PW containing high concentration of chloride ions. Total oily hydrocarbons (TOH) content and chemical oxygen demand (COD) as integral parameters and gas chromatography / mass spectrometry as analytical method were used to evaluate the efficiency of the treatment. At the optimal conditions, 15 mA/cm2 and 15 min, 92.5 % removal of TOH and 25 % removal of COD have been achieved through energy consumption 2.218 kWh per kg removed TOH by the EO. Additionally, the treatment of PW in a cell having SS cathode and iron as sacrificial anode has been performed, where electrocoagulation (EC) supplemented by electroflotation cause decrease of organic contaminants concentration. At the optimum conditions, current density 10 mA/cm2 applied for 10 min (energy consumption 0.603 kWh/kg) or current density 8 mA/cm2 applied for 15 min (energy consumption 0.629 kWh/kg) the TOH removal of 95.4 % and 96.4 % respectively have been determined. EC/EF has been found to be more effective than the EO/EF for treating the PW polluted by high-molecular alkanes. The EC/EF is an environmentally friendly and efficient method.
Keywords: electrocoagulation, electroflotation, electrooxidation, oily produced water treatment