Coagulation/flocculation/sedimentation is a common form of pre-treatment for UF (ultrafiltration) within water treatment plants, but little research has been conducted on floatation as a part of the pretreatment. The objective of this study is to compare floatation with sedimentation in the pretreatment of a water with a high hydrophobic NOM (natural organic matter) content. Fouling tests consisted of multiple filtration/backwashing cycles performed by an automated bench-scale UF hollow fiber membrane system. Alum coagulation coupled with floatation produced the least severe hydraulically irreversible fouling and also produced the highest quality permeate based on TOC (total organic carbon) concentrations. The hydrophobic fraction of NOM was found to affect hydraulically irreversible fouling in the earlier part of the runs while transphilic NOM and particulate organic carbon affected hydraulically reversible fouling. (C) 2015 Elsevier B.V. All rights reserved.