College of Mechanical and Electrical Engineering, China Jiliang University, Hangzhou 310018, China.
College of Mechanical and Electrical Engineering, China Jiliang University, Hangzhou 310018, China.
Sci Total Environ. 2022 Apr 15;817:152939. doi: 10.1016/j.scitotenv.2022.152939. Epub 2022 Jan 8.
Pressurized electro-dewatering technology is considered to be one of the most effective methods for improving dewatering performance of sewage sludge. In this paper, four dewatering protocols were developed to further explore the coupling mechanism of sludge dewatering through mechanical pressure, electric field and their joint. The results showed that the dewatering performance of the four dewatering protocols were as follows: pressurized electro-dewatering with constant voltage gradient mode (G-PEDW) > first mechanical dewatering then electro-dewatering > mechanical dewatering > electro-dewatering. The coupling mechanism was revealed from the perspectives of pore structure and moisture distribution of sludge cakes. The pore structure was discussed in detail from the whole pore size distribution and fractal dimension. The fractal dimension could quantitatively describe the change of pore structure. The moisture distribution was analyzed by the thermogravimetric differential scanning calorimetry test. The results showed that the electric field could reduce bound strength of moisture and produce new micro-pores to build more water flow paths, the water was discharged through interior capillary channels, and mechanical pressure could accelerate the water removing process. Response surface method was used to establish an empirical prediction model of G-PEDW, and discussed the selection of optimal parameters. The R-square values of mathematical models of moisture content and energy consumption were as high as 0.9863 and 0.9838, respectively, which was more advanced than other mathematical models. Experiments showed that G-PEDW could reduce the time to 20 min or reduce the energy consumption to 7.1 Wh/kg when the target moisture content was set to 41.7%.
加压电脱水技术被认为是提高污水污泥脱水性能的最有效方法之一。本文开发了四种脱水方案，以进一步探索通过机械压力、电场及其联合作用对污泥脱水的耦合机制。结果表明，四种脱水方案的脱水性能如下：恒电压梯度加压电脱水（G-PEDW）＞先机械脱水后电脱水＞机械脱水＞电脱水。从污泥饼的孔隙结构和水分分布角度揭示了耦合机制。从整个孔径分布和分形维数详细讨论了孔隙结构。分形维数可以定量描述孔隙结构的变化。通过热重差示扫描量热试验分析了水分分布。结果表明，电场可以降低水分的结合强度并产生新的微孔，从而建立更多的水流路径，水通过内部毛细通道排出，机械压力可以加速脱水过程。采用响应面法建立了 G-PEDW 的经验预测模型，并讨论了最优参数的选择。水分含量和能耗数学模型的 R 方值分别高达 0.9863 和 0.9838，优于其他数学模型。实验表明，当目标水分含量设定为 41.7%时，G-PEDW 可以将时间缩短至 20 分钟或将能耗降低至 7.1 Wh/kg。
