Novel advanced oxidation technology of Fe2+-activated peracetic acid for high efficient disintegration of waste activated sludge

The low hydrolysis rate of sludge has become a bottleneck for the resource utilization of anaerobic fermentation of sludge. In order to improve the hydrolysis rate of sludge, the advanced oxidation technology of Fe2+-activated peracetic acid (PAA) was employed. The efficiency and mechanism of sludge disintegration treated by Fe2+/PAA were analyzed by measuring soluble chemical oxygen demand (SCOD), polysaccharides, and nucleic acids, along with the characterization of scanning electron microscope (SEM), zeta potential, electron spin resonance (ESR) etc. Optimum sludge disintegration was achieved when the molar ratio of Fe2+/PAA was 0.4, PAA dosage was 20 mg/g SS, pH was 6.68, and reaction time was 6 h, resulting in SCOD, polysaccharides, and nucleic acids concentrations of 713.65, 139.26, and 123.65 mg/L, respectively. Free radical quenching test and ESR analysis identified the main active species in the Fe2+/PAA system were center dot OH, R-O center dot, and FeIVO2+. During the reaction, PAA and its active free radicals effectively destroyed extracellular polymeric substances (EPS) and sludge cell structure, causing the proteins and polysaccharides in tightly bound EPS (TB-EPS) to be transferred to loosely bound EPS (LB-EPS) and soluble EPS (S-EPS), sludge particle size decreased, sludge cell structure destroyed, and large amounts of intracellular organic matter, nitrogen, and phosphorus dissolved out. Meanwhile, the content of humic acid-like and fulvic acid-like organic matter in the liquid phase increased, and the dissolved cellular metabolites were oxidized to small molecules. The research findings provide a new pathway for sludge disintegration for the high-value utilization of sludge resources.