A critical review on the development for electro-osmotic dewatering (EOD) technology of sludge.

As a crucial step prior to the final treatment of sludge, sludge dewatering determines the subsequent transportation costs and the scale of treatment and disposal. Electro-osmotic dewatering technology of sludge drives the migration of water molecules through an applied external direct current electric field. In general, it does not require pretreatment or the addition of chemical agents, and has the advantages of compact equipment, simple operation, good dewatering effect and no secondary pollution. Its typical device consists of anodes/cathodes, pressure system, filtrate collection system, as well as a power supply and control unit. The mechanism of electro-osmotic dewatering of sludge involves multiple effects such as electrolysis, electro-osmosis, electromigration, electrophoresis and pH gradient, which realize the directional migration of moisture and thus achieve deep dewatering. The main influencing factors of the electro-osmotic dewatering performance include voltage gradient, electrode materials, pressure, pH and the physicochemical properties of sludge. Notably, the electro-osmotic dewatering process of sludge can also synchronously promote the removal and recovery of metal ions in sludge, and has the potential to inactivate pathogenic bacteria, which realizes the stabilization and harmlessness of sludge, thereby providing convenience for the subsequent resource utilization of sludge.