The area of ​​action of nanofiltration is located between reverse osmosis and ultrafiltration. Due to the size of the pores on the membranes with a diameter of one nanometer, it got its name. Nanofiltration is a relatively new process of water treatment by membrane filtration.

Nanofiltration is used to separate solutions of small molecular weights such as small organic molecules (such as sucrose and glucose), inorganic salts, aqueous solutions, etc. It is used in cooling systems for water decarbonization, beverage production or ion demineralization preparation to reduce regeneration and save on chemicals. It finds secondary application when it is necessary to remove harmful chemical constituents from water, such as arsenic (As), pesticides, sulfates, etc.

The efficiency of the nanofiltration process depends on the operating conditions such as the working flow, pressure, temperature and pH of the aqueous solution, and the physico-chemical properties of the membranes themselves. Environmentally, nanofiltration is more acceptable than reverse osmosis as it operates at a slightly lower operating pressure, and consequently has lower operating costs.