Effect of a suspended carrier on membrane fouling in a submerged membrane bioreactor

In an attempt at membrane fouling control, a kind of cylindrical plastic suspended carrier was added in a submerged membrane bioreactor (SMBR) and its effect was investigated in this study. According to the transmembrane pressure (TMP) profiles and the sludge characteristics in comparative runs with and without suspended carriers, it was found that the suspended carriers added in SMBR had two effects on membrane fouling: one was the positive effect of mechanically scouring the membrane surface and the other was the negative effect of breaking up sludge flocs. Sludge particle size distribution change was mainly responsible. It was suggested to apply the suspended carrier at higher MLSS concentration and lower carrier dose based on the consideration for retarding sludge breakage caused by the carrier. The experiment was conducted under higher MLSS (8 g L⁻¹) and lower carrier dose (carrier volume/total volume = 1%). The TMP increase was effectively retarded by added suspended carriers compared to the system without addition of the carriers. The effect of suspended carriers on membrane fouling at high MLSS concentration was verified.