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Nanofiltration is a membrane filtration process that takes place in a porosity range between 150-500 Dalton, depending on the molecular structure (pore size around 1 nm), which achieves, among other things, the separation of polyvalent ions with an effectiveness of more than 95 %, as well as organic matter of low molecular weight (sugar, proteins, etc.).
There are a variety of membrane types on the market, making it possible to achieve a variety of different qualities for final product. It is worth mentioning:

  • Membranes with a spiral configuration: they consist of a group of membranes wound together over a tube that collects the permeate; in this case the water flows from the outside to the inside. They are more compact units and are used when high quality ultrapure water is required.
  • Tubular membranes: in this case, the tube-shaped membranes are placed on a support that acts as a collector. The flow goes from the inside to the outside, and  use is more widespread, due to its greater strength.


The main uses of this technology are:

  • As a pretreatment for other processes, e.g., reverse osmosis
  • Industrial process feed water
  • Separation of heavy metals
  • Wastewater reuse
  • Water softening (removes calcium, magnesium, and sulfate ions, among other things)
  • Reuse of brine


Some of the advantages of this treatment system are:

  • Compact plants (they take up less space)
  • Low pressure requirement