This study examined the effects of feed water chemistry and membrane fouling on the rejection of trace organics by a loose nanofiltration membrane. One ionisable and one non-ionisable trace organics were selected for investigation. Results reported here indicate that the solution pH and ionic strength can markedly influence the removal of the ionisable trace organic compound sulfamethoxazole. These observations were explained by electrostatic interactions between the solutes and the membrane surface and by the speciation of the ionisable compound. On the other hand, no appreciable effects of solution pH and ionic strength on the rejection of the neutral compound carbamazepine were observed in this study. In addition, membrane fouling has also been shown to exert some considerable impact on the rejection of trace organics. However, the underlying mechanisms remain somewhat unclear and are subject to on-going investigation.