Insight into sludge dewatering by periodate driven directly with Fe(Ⅱ): Extracellular polymeric substances...

The production of waste activated sludge is expanding in tandem with the significant growth in the global population. It is important to explore sludge pretreatment technology to achieve sludge reduction. In this study, deep sludge dewatering was achieved by using Fe²⁺-catalyzed periodate (Fe²⁺/PI) conditioning. The result showed that capillary suction time was reduced by 48.27% under the optimum Fe²⁺ and PI dosages. ·OH, Fe^Ⅳ, O₂^·-, ¹O₂, and IO₃· generated from the reaction between Fe²⁺ and PI, while ·OH (49.79%) and Fe^Ⅳ (47.76%) contributed significantly to sludge dewatering. Investigations of the mechanism revealed that the synergistic action of radical species oxidation and iron species flocculation in Fe²⁺/PI conditioning led to the mineralization and aggregation of hydrophilic substances in extracellular polymeric substances. The hydrophobic groups on the protein surface were more exposed to soluble extracellular polymeric substances and reduced protein-water interaction. The variations in zeta potential and particle size also verified the presence of a synergistic effect of oxidation and flocculation. The morphology observations revealed that the increased frictional forces generated when water flowed over the raw sludge (RS) surface prevented the rapid passage of internal water. In addition, the hydrophobic and electrostatic interactions in the sludge samples were essential influences that promoted flocculation and sedimentation of the sludge. This research aids engineers by providing a new option to better optimize sludge management while also deepening understanding of the Fe²⁺/PI conditioning involved in sludge dewatering.