Nano filtration is a separation process characterized by organic, thin-film composite membranes with a pore size range of 0.1 to 10nm. Nanofiltration membranes have pore sizes from 1-10 nanometers, smaller than microfiltration and Ultra Filtration, but larger than Reverse Osmosis Membranes. Unlike reverse osmosis (RO) membranes, which reject all solutes, NF membranes can operate at lower pressures and offer selective solute rejection based on both size and charge. Nanofiltration membranes allow water and some salts to pass through the membrane while retaining multivalent ions, low molecular weight molecules, sugars, proteins, and other organic compounds
Nanofiltration (NF) process is used most often with low Total Dissolved Solids water such as Surface Water and fresh ground water, with the purpose of softening (Polyvalent Cations) and removal of disinfection by-product precursors such as natural organic matter and synthetic organic matter. Nanofiltration is also becoming more widely used in Food Processing Applications such as Dairy, for simultaneous concentration and partial (monovalent ion) demineralisation.
Nanofiltration membranes overall are also able to greatly reduce levels of Nitrates, Sulfates, Tannins, Turbidity, Color, TDS, and moderate levels of salt from feed water streams.