BACKGROUND: Electrochemical oxidation has been applied successfully in industrial waste-water treatment. The simultaneous removal of CODCr and NH3-N, as well as the corresponding mechanisms and reaction zone, were examined in this study. The reaction kinetics and the significant factors that affect removal performance were also studied. RESULTS: The COD(Cr) removal efficiency without chlorides in waste-water was only 11.8% after 120 min of treatment, which was much lower than the efficiency with chlorides, and agitation did not improve the performance. When the current density was increased from 2.5 to 10mA cm(-2), the removal efficiency was improved. The removal efficiencies of COD(Cr) and NH(3)-N were less at initial pH = 11 than at pH = 3 and 8.7 ( without adjustment). The COD(Cr) and NH(3)-N removal efficiencies were decreased by about 30% and 50%, respectively, when the electrode distance was increased from 4 to 12 cm. Instantaneous current efficiency decreased with increase in current density. CONCLUSIONS: The degradation of pollutants occurred mainly at the boundary layer between the electrode and the bulk solution. The indirect oxidation by active chlorine generated from the chlorides was proven to be the primary mechanism of electrochemical oxidation treatment. The removal of COD(Cr) in this study followed a pseudo-first-order kinetic model. (C) 2011 Society of Chemical Industry