An economic assessment of the enhanced dewaterability of municipal wastewater sludge following ultrasonic treatment

Abstract

This study examined the dewatering behavior of sludge subjected to ultrasonic (US) treatment by measuring capillary suction time (CST) and specific resistance to filtration (SRF). The results revealed a significant decrease in the CST and SRF at high volumetric supplied energy, E-v (> 5,400 kJ L-1) due to the solubilization of disintegrated sludge floc or suspended solids. Moreover, the decrease in the sludge volume/mass and water content was proportional to E-v. However, the potential to reduce the sludge cake and water content was lower at higher E-v (> 5,400 kJ L-1) due to the release of some of the water trapped inside the sludge flocs or cells before sludge compaction. We conclude that selecting the optimal US energy is critical to obtain enhanced dewatering properties and reduced sludge cake. The economic efficiency of incinerating ultrasonically treated sludge cakes was high, with savings of similar to 52% in total treatment costs. (C) 2014 The Japan Society of Applied Physics