Conditioning of waste activated sludge for dewaterability by ultrasonic

Abstract

Efficiency of sonication was tested at batch cycles for sludge dewaterability on waste activated sludge samples. The study was specifically focused on the effect of specific energy and the changes in characteristics of the sludge were mainly followed by Capillary Suction Time (CST) and Specific Resistance to Filtration (SRF) parameters. The changes in viscosity, pH, Total Dissolved Solids (TDS) and Volatile Solids (VS) parameters were also elaborated to better understand the effective mechanism of sonication. It was inferred from the study that sonication meets the expectations on sludge conditioning only if it is applied at low specific energy levels just only to destabilize the flocs but not to lyse the cells structure. CST periods of the slurries decreased from order of minutes to seconds by lowering the specific energy. The lowest CST, which was observed with the waste activated sludge, was 10 s at 0.02 kJ/L specific energy sonicated for 2 seconds. Sonicated waste activated sludge proved to be favorable to dewaterability. It was inferred from the study that the components of a specific energy, power and sonication period, should be applied such that power should be minimized and the period be maximized, to enhance the dewaterability of slurries.