Chemical cleaning of membranes fouled by natural organic matter (NOM) generates secondary pollution. In this study, the effect of ultrasonic cleaning of polytetrafluoroethylene (PTFE) membrane fouled by pre-coagulated humic acid-bentonite mixture was investigated. Results show that chemical coagulation prior to microfiltration improved turbidity and TSS removals by 9.5% and 11.4%, respectively. Experimental data fitted to constant pressure filtration models determined the sequence of dominant fouling mechanism as follows: (i) membrane resistance-limited, (ii) pore blocking resistance-limited, and (iii) cake formation resistance-limited. Relative membrane permeability of 53 and flux recovery of 45% were achieved when continuous ultrasonic cleaning was done at a 2.0 cm probe distance, 25 min total cleaning time, 15 mg/L coagulant dose, and 15 W ultrasonic power. Ultrasonic cleaning was found to be more effective than hydraulic cleaning in terms of flux recovery. Compared to chemical cleaning, it is a competitive and safer alternative in mitigating NOM-induced fouling. (C) 2015 Elsevier B.V. All rights reserved.