Attenuation of contaminants of emerging concerns by nanofiltration membrane: Rejection mechanism and application in water reuse

Reverse osmosis (RO) membrane has been widely used as a barrier for contaminants of emerging concerns (CEC) and pathogens in water reuse. In this chapter, nanofiltration (NF) membrane as a means of more cost-effective separation method for the attenuation of CEC was overviewed. While NF membrane separation efficiency for CEC varies based upon water chemistries such as pH and ionic strength, physical properties of membrane, and chemical properties of CEC, charged and/or hydrophobic CEC with large molecular weight can be effectively retained by NF membranes. However, uncharged small hydrophilic CEC such as N-Nitrosodimethylamine (NDMA) can easily pass through NF membranes, therefore requiring downstream treatment such as UV-advanced oxidation process (AOP) to further treat such CEC. In addition, remaining tasks for wider implementation of NF membrane in water reuse was also discussed, which covers monitoring strategies, fouling index for diverse effluent organic matter, and needs for CEC rejection database.