Wastewater from water softening stations contains a large amount of calcium and magnesium salts. The results of studies aimed at using these waters as natural solutions of calcium and magnesium ions in the processes of reagent purification of other categories of wastewater are presented. The conditions for the formation of sparingly soluble calcium and magnesium compounds during their alkali treatment using potentiometric titration were studied. According to the results of potentiometric titration of solutions of magnesium and calcium salts with alkali, the ranges of the active reaction of the medium are established, corresponding to the formation of precipitates in the form of hydroxides for magnesium and calcium. The potentiometric titration curves have sufficient selectivity for the quantitative evaluation of the compounds formed with acceptable accuracy. It is established that the interaction of pollutants of real sewage with freshly formed precipitation of calcium and magnesium hydroxides occurs according to the adsorption mechanism. Data on the sorption properties of calcium and magnesium hydroxide precipitation in relation to pollutants of textile enterprises are presented. The greatest efficiency of water purification is achieved by solid dispersed impurities absorbed by hydroxides at the time of structure formation and by dyes. The extraction of hydrocarbons, such as petroleum products and surfactants, does not exceed 40%.