There is disclosed a treatment of w

There is disclosed a treatment of water that greatly reduces the scaling tendency of the water during its subsequent use or processing. The treatment comprises precipitation and separation of the calcium values of the water as calcium carbonate by the addition of magnesium hydroxide precipitant thereto, with, as needed, a carbonate source, e.g., carbon dioxide. During subsequent use or processing, salts dissolved in the water are concentrated in a residual portion thereof and the residual portion is processed by the addition of calcium hydroxide to precipitate the dissolved magnesium values from the residual portion and supply the magnesium hydroxide that is employed as the precipitant in the treatment of the raw water. The treatment can be applied to any of a variety of water treating processes such as reverse osmosis, distillation, electrodialysis, freezing, vapor compression, ion exchange, evaporative cooling and/or boiler feed water treatment. All of these processes are limited in efficiency and equipment design by the concentration of calcium salts in the residual water which rapidly approach their solubility limits as the water is concentrated, thereby inhibiting further concentration or forming of scale on the separation equipment during the salt concentration steps of the treating process. This invention greatly increases the operating efficiency of salt concentration processes by reading the tendency of the water to form scale during its processing.