Dissolved organic matter (DOM) would absorb on nanoparticle (NP) surface and affect their fate, transport, bioavailability, toxicity and control. The study explored the removal of TiO2 NPs as a function of DOM composition in coagulation/ultrafiltration membrane (UF) process by comparing the flocs properties and membrane fouling in different water samples (e.g. HA synthetic water (WATER(SN)), surface water (WATER(XQ)) and municipal wastewater (WATER(MW)). The results showed that floc size of WATER(SN) increased with higher dosage and lower pH conditions. In contrast, the floc size of WATER(MW) decreased with increasing dosages while the floc size of WATER(XQ). was not affected by Polyaluminum Chloride (PAC) dosage and pH. TiO2 NPs in WATER(MW) and WATER(XQ) aggregated to larger and looser flocs than those in WATER(SN), probably due to the higher protein and larger molecules DOM fractions in WATER(MW) and WATER(XQ). The floc properties in different water samples affected fouling behavior in ultrafiltration membrane following pre-coagulation. PAC (2 mg L-1) could reduce 67% of external fouling resistance for WATER(SN) but only 20% for WATER(MW). In addition, lower restricting internal fouling for WATER(MW) and WATER(XQ) was achieved by a pre-coagulation process. (C) 2017 Elsevier B.V. All rights reserved.