In this study, the SMBR was compared in terms of membrane fouling with and without the addition of suspended medium in the membrane reactor. The effectiveness of medium in suspension in submerged membrane bioreactor (SMBR) was evaluated at different filtration flux. The SMBR was operated at a flux of 5-30 L/m(2) h (corresponding hydraulic retention time of 10-1.7 h) with and without suspended medium. The suspended medium used in this study was granular activated carbon (GAC; particle size 300-600 mm) at air scouring (aeration) rates of 0.5-1.5 m(3) m(-2) membrane area h(-1). At higher aeration rate of 1.5 m(3)/m(2) membrane area h, the effect of flux on membrane resistance was found to be negligible. The reduction of aeration rate from 1.5 to 1.0 m(3) m(-2) membrane area h(-1) resulted in a sudden rise of TMP. The addition of suspended medium prevented a sudden rise of IMP (total membrane resistance reduced from 51 x 10(11) to 20 x 10(11) m(-1)). The organic removal efficiency remained high irrespective of flux. The molecular weight distribution (MWD) and excitation emission matrix (EEM) analysis of SMBR effluent showed a range of organic (composed of amino acids, biopolymers, humics and fulvic acids type substances) removed by the GAC both by scouring and adsorption mechanisms. (C) 2011 Elsevier B.V. All rights reserved.