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The ion exchange system came into use in a start towards softening or softness in hard water. To achieve this objective, natural zeolites were used. Zeolites have the ability to change the cations (both calcium and magnesium), which are those that cause water hardness. After using the zeolites for the softening process, they are regenerated with a solution based on sodium chloride.

With the advance of science and the use of new technologies, processes were transformed. Today for example, synthetic resins are used for deonizar water. A widely used system is the equipment exchange "mixed bed". Through this system, different types of resin mixed with compressed air act together, connected in series.

Reverse Osmosis is the concept that encompasses all systems that work with Osmotic Phenomenon. Through this phenomenon, water (or any other solution), with a low concentration of salts, pass through a membrane and deposited in a solution with high concentration of salts. There is a difference in pressure between both sides of the membrane, which act on the water. For it is called osmotic pressure. The water being treated is subjected to greater than the osmotic pressure. When it passes through the membrane, the cations and anions (that are the focus of the team) fall in the membrane. Al filtered liquid left after passing through the membrane, is called "permeate".

Between 1959 and 1960, came into use in the treatment of water, within industries, Reverse Osmosis process. permeable membranes were beginning organic (made on the basis of cellulose acetate) and placed a spiral manner to achieve greater exchange surface. Then he started changing the materials used for the membrane. Emerged resins and hollow fiber ceramic membranes, which are used today.

Now the problem is knowing which system is best used for water treatment: if the Ion Exchange or Reverse Osmosis. To make this decision, we must consider some important criteria such as how much it costs energy to use, chemicals for regeneration , water to be treated. You should also consider what will be the fate of the discharge of regeneration, and how much you should invest in different equipment and staff training to be undertaken by the processes.