Removal of natural organic matter (NOM) from water by ion exchange – A review

Natural organic matter (NOM) is present in underground and surface waters. The main constituents of NOM are humic substances, with a major fraction of refractory anionic macromolecules of various molecular weights. The NOM concentration in drinking water is typically 2–10 ppm. Both aromatic and aliphatic components with carboxylic and phenolic functional groups can be found in NOM, leading to negatively charged humic substances at the pH of natural water. The presence of NOM in drinking water causes difficulties in conventional water treatment processes such as coagulation. Problems also arise when applying alternative treatment techniques for NOM removal. For example, the most significant challenge in nanofiltration (NF) is membrane fouling. The ion exchange process for NOM removal is an efficient technology that is recommended for the beginning of the treatment process. This approach allows for a significant decrease in the concentration of NOM and prevents the formation of disinfection byproducts (DBPs) such as trihalomethanes (THMs). This article provides a state-of-the-art review of NOM removal from water by ion exchange.