Nano filtration is a membrane liquid separation technology that is positioned between reverse osmosis (RO) and ultrafiltration. While RO can remove the smallest of solute molecules, in the range of 0.0001 micron in diameter and smaller, nanofiltration (NF) removes molecules in the 0.001 micron range.
NF is essentially a lower-pressure version of reverse osmosis where the purity of product water is not as critical as pharmaceutical grade water, or the level of dissolved solids to be removed is less than what is typically encountered in brackish water or seawater. As such, nanofiltration is especially suited to treatment of well water or water from many surface supplies like rivers or lakes.
Nanofiltration is used where the high salt rejection of reverse osmosis is not necessary. Yet NF is still capable of removing hardness elements such as calcium or magnesium. Like RO, NF is also capable of removing bacteria and viruses as well as organic-related color without generating undesirable chlorinated hydrocarbons and trihalomethanes (THMs). Nanofiltration is also used to remove pesticides and other organic contaminants from surface and ground waters to help ensure the safety of public drinking water supplies.
Sometimes referred to as “membrane softening,” nanofiltration is an attractive alternative to lime softening or sodium chloride zeolite softening technologies. And since NF operates on lower pressure than does RO, energy costs are lower than for a comparable RO treatment system.