Air sparging is widely used to minimize membrane fouling within submerged membrane bioreactor (SMBR) applied to wastewater treatment. This paper discusses its effectiveness in hollow-fibre membrane modules and its relationship with permeate flux, backwashing frequency and duration and main biomass characteristics. The effect of air sparging is expressed as shear intensity G which enables to describe the influence of several hydrodynamic parameters (viscosity, air sparging area and air flow-rate) on membrane fouling. The experimental study was carried out with sludge at four different biomass concentrations (MLSS = 4100-14,500 mg l(-1)) filtered under a broad range of hydrodynamic conditions (J = 20-63 l h(-1) m(-2); G=0-375s(-n)). Under constant filtration conditions, the slope of TMP against time, the fouling rate, is described by an exponential function of G: r(f) = (r(f))(0) exp(-(FGG)) + (r(f))(1), where shear intensity sensitivity factor (F-G) enables quantification of effectiveness of air sparging and limit fouling rate (rf), describes the fouling caused by adsorption of micro-colloidal and soluble fractions over the external membrane Surface. Also, it has been found that this sensitivity factor is a decreasing function of the imposed permeate flux and the biomass concentration. (C) 2007 Elsevier B.V. All rights reserved.