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3.4.6 Functional requirements

Nanofiltration membranes are mainly used to partially soften potable water, allowing some minerals to pass into the product water and thus increase the stability of the water and prevent it from being aggressive to distribution piping material.

Nanofiltration membranes are generally characterised by a high charge density and pore sizes in the range of nanometres. The surface charge is most often negative and has the greatest effect on the selective passage nature of these membranes.

New membranes have been developed which have unique properties, including a varying range of hardness rejection and fouling resistance.