EPS-Mediated Sludge Dewatering: Molecular Structure and Interfacial Behavior

Waste activated sludge (WAS) typically contains high moisture content, resulting in large sludge volume and increased disposal burden in wastewater treatment. Among the key limiting factors, extracellular polymeric substances (EPS) play a central role in governing sludge dewaterability by confining water within a complex structural network. This review establishes a structure-interaction-water retention framework to elucidate how EPS structural characteristics regulate water distribution and bound water confinement in sludge. Emphasis is placed on the molecular interactions and interfacial mechanisms responsible for water immobilization within the EPS matrix. By integrating cross-scale regulation strategies, from physicochemical conditioning approaches to molecular-level manipulation, this work provides a unified perspective on EPS-targeted dewatering enhancement. Advances in in-situ and molecular characterization techniques are critically assessed to clarify structural evolution and dynamic responses of EPS during conditioning. Finally, intelligent and deep dewatering-oriented EPS regulation pathways are proposed to guide future technological innovation.