Drinking water must be pure. The elimination of undesirable components such as organic matters and metallic trace elements with the aid of lime milk is an integral part of the water purification process.
Lime milk is also used for softening or remineralising drinking waters, in order to achieve a calco-carbonic balance in the water.
When water is too soft (too acid), it can damage pipes. The application of lime neutralises the corrosive action of the dissolved carbonic acid by transforming it into calcium, through this chemical reaction:
H2O + Ca(OH)2 lime milk + 2O2
-> Ca(HCO3)2 dissolved + H2O
When water is too hard, it forms scale and needs to be decarbonised through this chemical reaction:
Ca(OH)2 lime milk + Ca(HCO3)2 dissolved
-> 2CaCO3 insoluble + 2 H2O
pH adjustment using lime milk is the most important use of lime in underground drinking water production. Lime is more effective than other alkaline products (see chart).