Coagulation application prior to ultrafiltration process was carried out to increase humic acid (HA) removal and membrane permeability. The[Al13O4(OH)(24)(H2O)(12)](7+) polycation (Al-13 species) was used in the coagulant process and polyaluminum chloride (PACl) was also used for comparison. Characteristics of aggregates pre-coagulated by Al-13 species and PACl were investigated using a laser diffraction particle sizing device. Additionally, membrane fouling was investigated under different coagulation conditions. The various resistances caused by Al-13 and PACl treatment effluents were determined using the membrane fouling index equation. The results indicated that at dose of 1 and 3 mg/L, Al-13 produced larger flocs than PACl; while when dosage further increased, the PACl-HA flocs were much larger. The flocs formed by Al-13 were strong and compact, and those formed by PACl were weak and loosely structured with the exception of the flocs generated at 1 mg/L The investigation of membrane fouling demonstrated that Al-13 contributed to the best effluent permeating at 5 mg/L and the corresponding dose for PACl was 7 mg/L The adsorption resistance of effluent pre-treated by Al-13 accounted for a smaller percentage of the total resistances compared with that by PACl. (C) 2011 Elsevier B.V. All rights reserved.