Dynamic changes in the characteristics and components of activated sludge and filtrate during the pressurized electro-osmotic dewatering process

•Pressure–voltage had a synergistic effect on activated sludge dewatering.•Parallel slits formed in activated sludge at electrical compression stage.•Bound water/free water increased by 7.73 times after electrical compression.•Cell rupture in AS matrix occurred at electrical compression stage.

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.