Radical-Mediated integrated sludge treatment Strategy: Simultaneous enhancement of dewatering Performance, attenuation of antibiotic resistance Genes, and sustainable resource reutilization.

Abstract

This study presents a systematic investigation of the performance, underlying mechanisms, and resource recovery potential of a calcium oxide-activated persulfate (PS/CaO) system for sludge treatment. Following PS/CaO conditioning, sludge dewaterability was markedly enhanced, with the capillary suction time (CST) reduced by 45.5%. This enhancement was primarily through structural disruption of extracellular polymeric substances (EPS) and subsequent release of bound water. The PS/CaO process also yielded marked attenuation of antibiotic resistance genes (ARGs), reducing their absolute abundance by over 1.5 log units across all monitored ARG targets. Compositional analysis revealed that sludge organic matter, such as proteins and carbohydrates, underwent progressive degradation and concurrent humification, yielding humic-like and fulvic-like acids at concentrations of 5.7% and 4.2% (w/w), respectively. Reactive oxygen species (ROS) identification confirmed sulfate radicals (SO4·-) and hydroxyl radicals (·OH) as the dominant reactive species responsible for dissolved organic matter (DOM) transformation with oxygenation, Maillard condensation, and dealkylation identified as key reaction pathways. Pot experiments further demonstrated that application of the treated sludge at a 2% (w/w) dosage significantly increased wheat fresh biomass by 87.83% relative to the control. Life-cycle assessment further confirmed its superior environmental compatibility relative to aerobic composting. This study presents a technically viable approach and a robust theoretical basis for achieving enhanced sludge dewatering, effective risk mitigation, and safe resource reutilization.