Within the framework of our new technological concept for the desalination of surface water to industrial wafer with lower impact on the environment, improved pretreatment of the feed surface wafer was the main objective of this study. The pretreatment involved: screening; lime-alkaline softening (precipitation) and adsorption of the organic matter on the Mg(OH)(2), which is formed, combined with coagulation and flocculation; mechanical bed filtration; weak cation ion exchange; deep cartridge filtration. The combined operation between the lime-alkaline precipitation and the weak cation exchangers was investigated using two types of water: synthetic water with low organic and silica contamination and varying inorganic concentration as well as surface water with higher organic and silica concentration and varying concentration of inorganics (river Blies, Saarland, Germany). The influence of pretreated water quality on low-pressure reverse osmosis partial desalination and retentate concentration by reverse osmosis was studied.