Nanofiltration (NF) is a pressure driven cross flow separation process using a semi-permeable membrane. NF is often referred to as membrane softening, which is one of the major uses of the technology. Nanofiltration membrane softening has a wide range of performance characteristics between reverse osmosis (RO) and ultrafiltration (UF). It is similar to RO in concentrating dissolved organics and minerals but requires lower pressures. Typical NF systems operate at net driving pressures of 50 to 150 psi compared to 150 to 300 psi for brackish RO, the process from which it evolved.
The basic design guidelines, operational parameters, and process considerations for NF and RO are similar and solute rejection is influenced by pH, ionic charge and molecular weight. For water treatment, NF is typically selected over RO when the primary goal is to reduce hardness rather than salinity. Nanofiltration is accepted as a “best available technology” for removing precursors that form chlorinated hydrocarbons in potable water production. It also acts as an effective barrier in removing microbial cysts, bacteria, and viruses, inspiring the 1976 concept of “partial demineralization but total treatment”. NF is successfully employed in removing larger dissolved compounds and ions such as uranium and radium.
NF is used in a variety of food processing applications including dairy cheese whey recovery and maple sap concentration and in unique industrial applications including sulfate removal for process waters in offshore oil platforms.
AMTA is the only industry organization that focuses specifically on membrane processes including reverse osmosis (RO), nanofiltration (NF), microfiltration (MF), ultrafiltration (UF), electrodialysis reversal desalination (EDR), and membrane bioreactors (MBR). The AMTA website offers a wide range of proprietary Fact Sheets and a complete Digital Library of presentations, posters, and papers on all topics related to membrane treatment, membrane systems, and regulatory and compliance topics.
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