In this paper, a submerged membrane adsorption bioreactor (MABR) was evaluated for drinking water treatment at a hydraulic retention time (HRT) as short as 0.5 h. As powdered activated carbon (PAC) was added to the bioreactor at 8 mg/L raw water, the MAR achieved much higher removal efficiency for organic matter in the raw water than the parallel-operated membrane bioreactor (MBR). Moreover, the trans-membrane pressure (TMP) of MABR developed much lower than that of MBR, demonstrating PAC in MABR could mitigate membrane fouling. It was also identified here that the removal of dissolved organic matter (DOM) in MABR was accomplished through the combination of three unit effects: rejection by ultrafiltration (UF) membrane, biodegradation by microorganism, and adsorption by PAC; the last was of great importance. A sludge layer was observed on the membranes surface in both MABR and MBR and PAC particles themselves constituted a part of the cake layer and helped to intercept DOM in the mixed liquor by adsorption in MABR, especially for organic molecules of 5000-500 Da. The OF membrane together with the sludge layer and PAC layer in the MABR was able to reject hydrophobic bases (HoBs), hydrophobic neutrals, hydrophobic acids (HoAs), weakly hydrophobic acids (WHoAs) and hydrophilic matter (HiM) in the mixed liquor by 40.0%, 43.9%, 71.8%, 56.6% and 35.9%, respectively. (C) 2008 Elsevier B.V. All rights reserved.