This paper focused on the effects of mesoporous adsorbent resin (MAR) and powdered activated carbon (PAC) pretreatments on ultraffltration (UF) membrane fouling caused by natural organic matter (NOM). Three model foulants, humic acid (HA), bovine serum albumin (BSA) and sodium alginate (SA), were adopted to represent different NOM fractions in natural waters. Moreover, the impact of the presence of adsorbent particles in UP feed water on membrane fouling was also evaluated. The results indicated that MAR adsorption exhibited remarkable performance in alleviating HA and BSA fouling, no matter whether MAR particles were removed before UF or not. In contrast, PAC pretreatment slightly ameliorated HA fouling when PAC particles were removed before UP, whereas HA fouling was exacerbated by PAC pretreatment with PAC particles present in UP feed water. BSA fouling was moderately controlled by PAC adsorption irrespective of the presence or absence of PAC particles in UP feed water. However, neither of these two pretreatments visibly influenced SA fouling. Overall, the results obtained in the current research would provide relevant information on adsorbent selection and process design of the hybrid adsorption/UP process according to the composition and properties of NOM. (C) 2014 Elsevier B.V. All rights reserved