A pilot-scale, membrane-free, bioelectrochemical system (BES) reactor (16 L in volume) installed by five cathodes with different distance to anode was tested for the removal of copper. CuSO(4) solution was used as catholyte and anaerobic microorganisms grew as anodic biocatalyst. In the reactor, Cu(II) was reduced and recovered as solid-state copper deposits on cathodes accompanied with power production. When 600 and 2000 mg of Cu(2+) were added into the cathode chamber, removal efficiency of 92% over 480 h and 48% over 672 h period with electric quantities of 2724 C and 8703 C, and cathodic efficiencies of 61.92% and 45.60% were achieved, respectively. The reduction reaction rate depended on the initial average Cu(2+) concentration. The internal resistance decreased and voltage output increased as the distance of each cathode to anode decreased. The mass of metal Cu crystals and Cu(I) compounds deposited on each cathode was dependent on current intensity. (C) 2011 Elsevier Ltd. All rights reserved.