In this work, the results of membrane filtration of natural water together with theoretical description (modelling) are presented. The obtained results were described in terms of the semi-empirical mass transport models and the extended Nernst-Planck equation. The model of NF based on that equation, taking into account membrane structural parameters and ionic composition of waters, effective for ternary systems, in the case of real multi-ionic solutions (no. of ions 8) needs farther improvement.