Although Nanofiltration appears at the same time as Reverse Osmosis, it's a technology that is recently being applied.

It is mainly used in applications with low TDS (Total Dissolved Solids) such as surface waters, for softening and removal of disinfection by-products precursors (Natural Organic Matter).

Nanofiltration membranes' pore size is a few nanometers (10 angstroms) wide. Among different applications, removal of TOC, Nitrate, Herbicide, Hardness, Iron and THM's precursors are the most common.