A speciality membrane filtration process which rejects solutes larger than approximately one nanometer (10 angstroms) in size.

(NPDES) US program to issue, monitor, and enforce pretreatment requirements and discharge permits under the Clean Water Act.

(NDP) The net feed pressure of a reverse osmosis system plus the osmotic pressure of the permeate, minus the permeate line pressure and osmotic pressure of the feedwater.

The chemical process that produces a solution that is neither acidic nor alkaline.

See “nanofiltration”.

(NCH) The hardness in water caused by chlorides, sulphates and nitrates of calcium and magnesium.

(NCG) Gaseous material not liquefied when associated water vapour is condensed in the same environment.

A solution that contains one equivalent weight of a substance per litre of solution.