Biopolymer transformation and antibiotics degradation of wastewater sludge using thermally activated persulfate oxidation for dewaterability enhancement

• Thermally activated persulfate (TAP) oxidation enhanced sludge dewaterability. • Thermal hydrolysis and oxidation had a synergistic effect in biopolymer hydrolysis. • Proteins were decomposed into polypeptides, amino acids, and ammonia nitrogen. • TAP oxidation increased bioavailable phosphorus content of sludge. • TAP oxidation reduced antibiotic content and ecotoxicological risk of sludge. Wastewater sludge is mainly comprised of microorganisms and extracellular polymeric substances (EPS). The gel-like network structure of EPS traps bound water, resulting in poor dewaterability of sludge. In this work, the thermally activated persulfate (TAP) oxidation was used in sludge treatment to improve dewaterability. The transformation of proteins and phosphorus were systematically investigated to understand the mechanisms of sludge conditioning with TAP at molecular levels. The results showed that TAP oxidation produced SO 4 - and OH radicals which decomposed the macromolecular proteins, causing uncoiling of protein secondary structures and exposure of inner hydrophobic sites. The polypeptide, amino acid, and ammonia nitrogen were generated, and sludge dewaterability was enhanced. A mechanism was proposed to explain the synergistic effects of thermal hydrolysis and TAP oxidation on the transformations of nitrogen and phosphorus containing biopolymers. Furthermore, 30%-100% of antibiotics were degraded in TAP treatment. TAP performed well in macrolide and tetracycline degradation (>80%), while most of quinolone antibiotics were more refractory to oxidation.