The removal efficiency of COD in the treatment of simulated laundry wastewater using electrocoagulation/electroflotation technology is described. The experimental results showed that the removal efficiency was better, reaching to about 62%, when applying ultrasound to the electrocoagulation cell. The solution pH approached neutrality in all experimental runs. The optimal removal efficiency of COD was obtained by using the applied voltage of 5 V when considering the energy efficiency and the acceptable removal efficiency simultaneously. The Cl- concentration of less than 2500 ppm had a positive effect on the removal efficiency. The performance of the monopolar connection of electrodes was better than that of the bipolar connection in this work. In addition, the removal efficiency of using Al electrodes was higher in comparison with using Fe electrodes in the study. The highest COD removal amount per joule was found to be 999 mg dm(-3) kW h(-1) while using two Al electrodes, although the removal efficiency increased with the number of Al plates. (C) 2008 Elsevier B.V. All rights reserved.