Selected processes for removing NOM: an overview

efore the 1970s, research into the nature of natural organic matter (NOM) in drinking water and into methods for its removal was driven primarily by the desire to remove color from public water supplies. Since then, several other problems associated with NOM have been identified, including its demand for coagulants and disinfectants, its potential to transport metals and hydrophobic organic chemicals, its potential to contribute to corrosion and slime growths in distribution systems (especially when oxidants are used during treatment), its potential contributions to taste and odor, its tendency to interfere with the removal of other contaminants, and its contribution to the formation of disinfection by-products (DBPs). As a result of these problems, there has been considerable applied and basic research focused on removing NOM from drinking water before disinfectants are applied. Much of this research, including the As a result of the anticipated Disinfectants/Disinfection By-product Rule, there has been increasing emphasis by the water industry on the removal of natural organic matter (NOM) from raw-water supplies. Three important NOM removal options are coagulation, granular activated carbon (GAC) adsorption, and membrane filtration. Of these three processes, coagulation is the most widely used in the water industry. But when coagulation cannot remove adequate concentrations of NOM so that disinfection by-products can be controlled, other treatment technologies such as GAC and nanofiltration may need to be used. Various aspects of each of these technologies are discussed.