The performance modeling and optimization of integrated ultrasonic-persulfate advanced oxidation system to improve activated sludge dewaterability

Conventional sewage sludge dewatering methods demand excessive chemicals and energy due to the sludge’s complex nature, resulting in lower efficiency and environmental acceptance. This study investigated the use of ultrasonic (US) and persulfate (PS) together to improve dewatering and explored the key parameters. Sludge dewatering experiments were performed using an ultrasonic-equipped water bath at a constant 40 kHz ultrasonic frequency. The impacts of the parameters persulfate and ferrous sulfate (Fe) concentrations and reaction time on dewatering efficiency were studied. Utilizing the Design Expert software and CCD method, 20 experiments were designed and repeated, yielding optimal persulfate and ferrous sulfate concentrations of 2.3 g/L and 1.7 g/L, respectively, and an 85-min reaction time, resulting in a 50.73% reduction in specific resistance to filtration (SRF). The proposed sludge dewatering method significantly improved the dewatering process. The reaction time had the most significant impact on the improvement. Subsequently, both the persulfate concentration and the ferrous sulfate concentration affected the proposed dewatering process. In addition, the analysis of the physical and chemical characteristics of the processed sludge with SEM, XRD, and FTIR techniques confirmed the destruction of sludge particles and the breakdown of polymer compounds.