Selenite and selenate removal in a permeable flow-through bioelectrochemical barrier

Highlights: • Selenate and selenite removal in a flow-through bioelectrochemical barrier was demonstrated. • Anaerobic treatment resulted in 85% Se removal efficiency. • A 1.4 V applied voltage coupled with acetate addition enhanced selenate and selenite removal. • Up to 99.5% selenate and selenite removal achieved in the bioelectrochemical system. This study demonstrated the removal of selenite and selenate in flow-through permeable bioelectrochemical barriers (microbial electrolysis cells, MECs). The bioelectrochemical barriers consisted of cathode and anode electrode compartments filled with granular carbon or metallurgical coke. A voltage of 1.4 V was applied to the electrodes to enable the bioelectrochemical removal of selenium species. For comparison, a similarly designed permeable anaerobic biobarrier filled with granular carbon was operated without voltage. All biobarrier setups were fed with water containing up to 5,000 µg L⁻¹ of either selenite or selenate and 70 mg L⁻¹ of acetate as a source of organic carbon. Significant removal of selenite and selenate was observed in MEC experimental setups, reaching 99.5–99.8% over the course of the experiment, while in the anaerobic biobarrier the removal efficiency did not exceed 88%. By simultaneously operating several setups and changing operating parameters (selenium species, influent Se and acetate concentrations, etc.) we demonstrated enhanced removal of Se species under bioelectrochemical conditions.