The performance and process of pressurized electro-osmotic dewatering (PEOD) technology for activated sludge (AS) were investigated. In PEOD process, a single pressure of 600 kPa only removed a small amount of free water and bound water in AS, whereas both kinds of water further decreased to 0.24 g g(-1), dry solid and 0.25 g g(-1) dry solid after the application of 50 V voltage at electrical compression (EC) stage. During the PEOD process, the loosely network structure was gradually ruined, and a quantity of narrow and parallel slits generated in dewatered AS at EC stage. The contents of organic matters in filtrate increased at all PEOD stages and humic acid-like organics formed at EC stage. Using the response surface method (RSM), the optimum dewatering conditions were determined as a combination of 401 kPa pressure and 50 V voltage, which gave a dry solids content and energy consumption of 41.90% (wt%) and 0.153 kWh per kg removed water. (C) 2014 Elsevier B.V. All rights reserved.