Abstract: A process for depleting monovalent cations from water comprising subjecting the water to reverse osmosis, so that the retentate from this reverse osmosis has a higher ionic concentration, and subjecting said retentate to electrodialysis, so as to recover a water depleted in monovalent cations. The water may, for example, be intended for nutritional purposes. The may also, for example, contain monovalent and divalent cations, In one embodiment, the permeate from the reverse osmosis is added to the water depleted in monovalent cations, so as to obtain a water with a controlled mineral content.

Abstract: The invention relates to a process for separating electrically charged solid particles or macromolecules contained in a solution by using a semi-permeable membrane which is specific for the separation to be carried out and by applying an electric field to reduce the concentration gradient in the immediate vicinity of the membrane. In the present invention, a plurality of semi-permeable membranes (2, 3) are arranged directly oppositely each other so as to define an alternation of low and high pressure compartments (4, 5), and periodically the direction of the electric field is reversed. The process of the invention allows increasing the exchange area while benefiting of permanently increased efficiency from the applied electric field.