An investigation was performed to study the influence of ultrasonic aided bacterial disintegration on the aerobic degradability of sludge. In first phase of the study, effective floc disruption was achieved at an ultrasonic specific energy input of 2.45 kJ/kg TS with 44.5 mg/L of Extracellular Polymeric Substance (EPS) release including 0.035 U/mL and 0.025 U/mL protease and amylase activity respectively. In second phase, experimental outcomes revealed bacterial disintegration of floc disrupted-sludge showing a maximum solubilization of about 23% and was observed to be superior to bacterially disintegrated (11%) and control (6%), respectively. The result of aerobic biodegradability of ultrasonic aided bacterially pretreated sludge showed volatile solids (VS) degradation of about 40.2%. The kinetic study of aerobic biodegradability through non linear regression modelling reveals that floc disrupted sludge showed better biodegradability with decay constant of about 0.19 d (1) relatively higher than the control (0.14 d (1)) and bacterially disintegrated (0.17 d (1)) sludges. (C) 2015 Elsevier Ltd. All rights reserved.