The disposal of huge municipal sludge with high moisture content has led to numerous energy consumption and brought extensive concerns in the world. In this paper, three dewatering modes, ultrahigh-pressure mechanical dewatering mode (UMDW), pressurized electro-dewatering (PEDW) with constant voltage mode (U-PEDW) and constant voltage gradient mode (G-PEDW) were performed on a self-designed pressurized electro-dewatering apparatus for municipal sludge. The pore structures and moisture distributions were detected by low-field nuclear magnetic resonance technology. Meanwhile, the moisture distributions and quantitative bound strength were analyzed by the thermogravimetric differential scanning calorimetry test. Moreover, a pore-scale electro-osmosis model was accordingly developed based on the fractal characteristics of pore size distribution. Finally, the effect of dewatering modes and operating parameters on moisture content and energy consumption were examined in detail.

The results indicate that the pore-scale electro-osmosis model show good consistency with experimental data. The electric field can drive the middle-layers-water to overcome the capillary pressure, and make G-PEDW removing more water than UMDW. The moisture content of dewatered municipal sludge by G-PEDW and U-PEDW reaches to 28.41% and 27.33%, respectively. Furthermore, the energy consumption of G-PEDW is 189.62Wh/kg._H2O, it is much lower than that of U-PEDW. Therefore, the G-PEDW mode with low moisture content and less energy consumption indicates best dewatering performance compared with UMDW and U-PEDW modes. The present work is helpful to understand the dewatering mechanisms of G-PEDW and provides useful guidelines for G-PEDW dewatering technology.

高含水量的巨大市政污泥的处置导致大量能源消耗，并引起了世界范围的广泛关注。本文对自脱水进行了三种脱水模式：超高压机械脱水模式（UMDW），带恒压模式的加压电脱水（U-PEDW）和恒压梯度模式（G-PEDW）。设计了用于城市污泥的加压电脱水设备。用低场核磁共振技术检测孔结构和水分分布。同时，通过热重差示扫描量热法分析了水分分布和定量结合强度。此外，基于孔径分布的分形特征，相应地开发了一个孔径电渗模型。

结果表明，孔尺度电渗模型与实验数据具有很好的一致性。电场可以驱动中间层的水克服毛细管压力，并使G-PEDW去除的水比UMDW多。G-PEDW和U-PEDW脱水城市污泥的含水率分别达到28.41％和27.33％。另外，G-PEDW的能量消耗为189.62Wh / kg。_H2O远低于U-PEDW。因此，与UMDW和U-PEDW模式相比，具有低水分含量和较少能耗的G-PEDW模式具有最佳的脱水性能。本工作有助于理解G-PEDW的脱水机理，并为G-PEDW脱水技术提供有用的指导。