This study investigated the performance of four different membrane bioreactor (MBR) systems, namely floating media biofilter-crossflow microfiltration (FMB-CFMF) system, submerged membrane bioreactor (SMBR) alone, submerged membrane adsorption bioreactor (SMABR) and sponge-SMBR system, in terms of critical flux. The results indicated that FMB could be used as a pretreatment unit prior to MBR in order to minimize membrane fouling when the FMB-CFMF system operated under sub-critical flux condition. The addition of powdered activated carbon (PAC) could maintain the sustainable flux at a lower TMP value (7.5 kPa). However, irreversible fouling occured when the filtration flux exceeded the critical flux. The addition of 10% volume (reactor volume) fraction of sponge could increase sustainable flux of SMBR system to 2 times.