Natural organic matter (NOM) fractionation of French River water (Nova Scotia, Canada) was performed at an integrated membrane system employing ultrafiltration (UF) and nanofiltration (NF) for water treatment. An attempt was made to evaluate this surface water and the effect of UF treatment on disinfection by-product (DBP) precursor removal. Each NOM fraction was assessed in terms of trihalomethane and haloacetic acid formation potential. The NOM fractionation was performed by separation into six fractions: hydrophobic acid (HOA), base (HOB) and neutral (HON) and hydrophilic acid (HIA), base (HIS) and neutral CHIN). The raw water was found to be mostly comprised of HIN (approximately 50%) and HOA (approximately 35%). Upon treatment with UF, 66% of the DOC was removed. The key finding of this work was that the HOA fraction was the main contributor to DBP formation potential. Removal of 93% of the HOA components through UF treatment resulted in a reduction of trihalomethane and haloacetic acid formation potential of 54 and 30%, respectively, despite the fact that HOA comprised 35% of the NOM in the raw water. The results also showed that the UF component of the system contributes to the overall DBP precursor removal at this full-scale plant. (C) 2012 Elsevier B.V. All rights reserved.