Softening of water - ion exchange

Water hardness, specifically the total concentration of calcium and magnesium ions contained in the water, causes problems mainly through its potential to form precipitates and deposits of the cited metals. Upon exceeding the equilibrium concentration, precipitation of mostly calcium carbonates occurs, clogging piping and causing problems in hot water systems, or just creating annoying spots on tap water accessories.

The water softening system works on the principle of ion exchange of the mentioned calcium and magnesium ions for sodium ions, thus eliminating their concentration in the treated water. As a filling in such devices, a special cation exchange resin called Katex is used, which binds cations present in the treated water. Regeneration of these devices is carried out with a saturated NaCl solution (common salt), thereby restoring the initial capacity of the filling used.


For the removal of nitrates from the water, a similar resin called Anex (anion exchanger) is used; it has a different anion binding strength, however. This cartridge has the ability to exchange the nitrate anions that are present for chloride anions, thus reducing their content in the treated water. A disadvantage of this process is the increased concentration of chloride anions after this treatment. If the water contains a higher concentration of both of these parameters, it is often only possible to modify it through reverse osmosis.