Application of CaO2-enhanced peroxone process to adjust waste activated sludge characteristics for dewaterability amelioration: Molecular transformation of dissolved organic matters and realized mechanism of deep-dewatering

Abstract

Sludge dewaterability is commonly poor due to the hydrophilic biopolymeric substances. The highly efficient oxidation process is of great significance for extracellular biopolymers disintegration and bound water discharge. This work investigated the novel CaO2-enhanced peroxone (CaO2/O3) process to adjust sludge characteristics for dewaterability enhancement and focused on the molecular composition and transformation of dissolved organic matters (DOM). CaO2/O3 (60/40 mg/gTS (total solid)) treatment showed more powerful sludge solubilization of 57.8% and cell death proportion of 46.1% over single CaO2 or O3 treatment. Hydrophilic extracellular polymeric substances, especially protein-like substances, were substantially degraded, and their conformation turned to be more hydrophobic, and carbohydrate-like, aminosugars-like, and lignins-like substances increased in CaO2/O3 process. Meanwhile, CaO2/O3 handling resulted in more decomposition of CHO-containing compounds than N-containing or S-containing compounds. Subsequently, 60 mg/gTS PFS (polyferric sulfate) reflocculation exerted a strengthened role in eliminating proteins & lipids-like, lignins-like, and unsaturated hydrocarbons-like substances, and especially S-containing compounds, which compensated for the unsatisfactory removal effects of these substances in the CaO2/O3 oxidation process. Therefore, the CaO2/O3-PFS treated sludge with less hydrated DOM easily harvested deep-dewatering in pressure filtration. Furthermore, it was noteworthy that the presence of CaO2 created an alkaline environment and served as the source of sustained-release H2O2, which accelerated O3 decomposition and greatly improved •OH generation. These findings provided molecular insight into a novel sludge conditioning approach for ideal dewaterability based on the CaO2-enhanced peroxone process in sludge treatment.