Abstract The capacities of nanofiltration and reverse osmosis high-pressure membrane systems to separate a high-concentration water solution have been investigated. The reverse osmosis membranes are able to retain NaCl, even if its concentration in aqueous solutions is near the saturation one. At the same time, it seems economically unreasonable to apply this process to electrolyte concentration over 100 g/l. Nanofiltration membranes keep their ability of selectively retaining ions at electrolyte concentrations in solutions up to 200 g/l. This enables us to use the nanofiltration membranes for separating multicomponent solutions into binary ones, from which the salts can be easily recovered by vaporization.