Copper reduction in a pilot-scale membrane-free bioelectrochemical reactor

► A pilot-scale, membrane-free, bioelectrochemical system reactor (16 L) was tested for the removal of copper. ► Cupric ions were reduced and recovered as solid-state deposits on cathode. ► The internal resistance decreased and voltage output increased as the distance of each cathode to anode decreased. ► The reduced copper speciation depended on initial cupric concentration, distance of cathode to anode and current density.