Ultrasonic Energy Transfer Optimization in Sludge Dewatering: Volume-Dependent Tuning of Ultrasonic Duration and Intensity for Enhanced Cavitation Efficiency

High water content in sludge has consistently posed a significant challenge in sludge treatment processes. As an effective approach for sludge dewatering, ultrasound treatment induces cavitation effects, mechanical vibration, and thermal effects to rapidly disrupt sludge floc structures and release bound water, with sonication energy density and ultrasonic duration serving as key control parameters that ultimately determine dewatering efficiency. This study identified the optimal sonication energy densities and ultrasonic durations for sludge volumes of 500ml, 750ml, 1000ml, 1250ml, and 1500ml as 0.161W/ml, 0.165W/ml, 0.171W/ml, 0.177W/ml, 0.180W/ml and 31s, 33s, 34s, 37s, 41s, respectively. Comprehensive analyses including WC, SRF, viscosity, particle size distribution, SEM, FTIR, and NMR were conducted on sludge samples of different volumes under these optimal ultrasonic conditions. The results demonstrated that while ultrasound treatment significantly reduced WC compared to raw sludge across all volumes, the degree of reduction varied with sludge volume. As sludge volume increased, the required ultrasonic intensity and duration increased accordingly, with the improvement in water reduction showing an initial enhancement followed by a gradual decline. The study established optimal sonication energy densities and durations for different sludge volumes, investigated the variations in WC and specific resistance to filtration under optimal ultrasonic conditions, examined the relationship between sonication energy density, ultrasonic duration, and sludge volume, and provided mechanistic insights through microscopic and spectroscopic analyses. These findings offer valuable guidance for industrial-scale sludge treatment by identifying appropriate ultrasonic conditions to enhance sludge reduction efficiency for large-volume applications.