Fouling of nanofiltration membranes by natural organic matter

In this study, various physical and chemical factor affecting natural organic matter (NOM) fouling of nanofiltration (NF) membranes were systematically investigated, with an emphasis on the effect of divalent cations (Ca2+). Zeta potential measurements show reduced membrane surface charge in the presence of divalent cations. Results from fouling experiments clearly demonstrate that divalent cations markedly increase the potential for NOM fouling. Increased NOM fouling is attributed to complexation between Ca2+ and NOM which causes a decrease in electrostatic repulsion. Permeation rate also plays a critical role in NOM fouling. Product water flux declines much faster as permeation rate increases. The addition of strong chelating agents (EDTA) to feed water improves membrane performance significantly.