All life occurring on earth depends on water in sufficient quantity and quality. The entire store of water of the earth becomes estimated on 1.5 billion Kubikkilometer - that is a meant cube with the edge length of 1100 kilometers. The largest portion is stored in the whole of the Weltmeere (94%). By the remaining remainder - fresh water - however only a fraction for the water supply is usable. (Schwoerbel 1987)

The complete store of water circulates in an enormous cycle, so that impurities in ground, air or water body arrive sooner or later also in all areas, which are used for potable water supply. The water supply enterprises are continuous by the guiding principles for the central potable water supply, self-servicer by the guiding principles for the Einzelwasserversorgung (DIN 2000 and DIN 2001) to keep a minimum quality of the drinking water. Both nourish-physiological criteria play a central role and aspects such as corrosion protection and stone deposit. (Aurand et al. 1991)

The quality of waters for the drinking water use the available is very different. Therefore some methods and additives must be used, in order to be able to keep the guidelines. Apart from filtering and flocculations the water additives are metered such as chlorine, chlorine dioxide, ozone, potassium permanganate, hydrogen peroxide, sodium peroxide sulfate and potassium mono by sulfate for the oxidation of organic and inorganic ingredients as well as for disinfection. As corrosion protection for the metal tube line system a set of phosphates and silicates serves.

Many of the legally permitted drinking water contents materials are not acceptable for the health. Like that are phosphate, silicate and nitrate of materials, it work eutrophierend. Usually geo genes - Karbonathärte (Säurekapazität to pH 4.3) and total hardness (sum alkaline-earths) unwanted.