Electrochemical and bioelectrochemical treatment of steam-assisted gravity drainage water

Abstract

This study compares electrochemical and bioelectrochemical approaches for treating Steam-Assisted Gravity Drainage (SAGD) water. Electrochemical treatment tests were carried out at applied voltages (V_ap) of 1.4, 2.0, and 2.5 V. Bioelectrochemical treatment in a Microbial Electrolysis Cell (MEC) was conducted at the same applied voltages with microaeration of both electrode compartments. The two treatment approaches were thereafter combined in a continuous flow setup that consisted of an electrochemical cell (EC, V_ap = 2.5 V) followed by MEC (V_ap = 1.4 V). Chemical oxygen demand (COD), naphthenic acid, dissolved metals, and metalloid concentrations of SAGD water were substantially reduced after all treatments, thereby rendering the treated water less toxic according to ecotoxicological tests. However, the MEC treatment was more energy efficient resulting in the lowest specific energy consumption (SEC) value of 5.2 kWh/kg_COD. By replacing a Ti/IrO₂-oxide current collector in the MEC with a custom-made Ti/NiCo-oxide mesh, the COD removal efficiency improved by 30%. The results suggest that a MEC equipped with Ti/NiCo-oxide current collector can provide cost-efficient treatment of SAGD water.