This research is intended to decompose organic substances in municipal wastewater with nano- and nonnano-scale electrocatalytic electrodes. As an anode, the nano-scale electrodes included lab-made TiO2 and Cu2O electrodes; the nonnano-scale electrodes were a commercial TiO2 and graphite plate. According to experimental results, the nano- and nonnano-scale catalytic electrodes can effectively remove the organic pollutants in the municipal wastewater. The perforated TiO2 electrode is the best for eliminating the chemical oxygen demand (COD), and its efficiency is about 90%(COD decreases from 400 to 40 mg L-1). The conductivity of municipal wastewater and the electro-catalytic process will increase the pH and eventually remains in the neutral range. The conductivity of municipal wastewater can be lowered to some degrees. The most attractive discovery of electro-catalytic process is that the dissolved oxygen (DO) in the municipal wastewater can be increased by the TiO2 electrode (nonnano-scale) around 4-6 mg L-1, but few DO is produced by the nano-scale electrocatalytic electrode. (C) 2008 Elsevier B.V. All rights reserved.