Enhanced deep-dewatering of high EPS-Containing sludge waste using PDMDAAC-PFS and H ₂ O ₂

Large quantities of sludge from wastewater treatment plants require dewatering before final disposal, with extracellular polymeric substance (EPS) significantly impacting sludge dewatering performance. This study achieved deep-dewatering of sludge with high EPS content (164.36-181.62 mg/g VSS) by reducing moisture content to 57.2% using a combination of polydimethyldiallylammonium chloride-ferric sulphate (PDMDAAC-PFS) and hydrogen peroxide (H₂O₂). Using PDMDAAC-PFS alone decreased tightly bound EPS (TB-EPS) from 152.7 to 135.3 mg/g VSS while increasing EPS by 77.2%, indicating that the reagent solubilised TB-EPS and disrupted the cell wall, releasing intracellular bound water. Further addition of H₂O₂ reduced total EPS by 34.2-55.1%, primarily affecting extracellular protein (PN) in TB-EPS. Three-dimensional fluorescence and Fourier transform infrared spectrometry revealed that the reduced PN in TB-EPS consisted mainly of tyrosine proteins, with the destruction of hydrophilic groups (amino group and carbonyl group) contributing to the release of bound water. Quenching tests demonstrated that hydroxyl radicals generated by H₂O₂ were crucial for EPS oxidation, contributing to 21.9% of sludge dewatering. Additionally, PDMDAAC-PFS re-flocculated the structurally damaged sludge into larger, more porous particles, enhancing the dewatering process. Thus, this study presents a novel method of deep-dewatering for waste sludge containing high EPS content.