In both drinking and process water preparation, lime is mainly used for pH adjustment and/or water purification.

Lime milk is a cost-effective reagent which reduces water's hardness by precipitating the bicarbonates dissolved in it, thus preventing the formation of scale.

In waste water treatment plants ( both urban or industrial ), lime is widely used for correcting the pH balance of acidic waters, for precipitating heavy metals and phosphates, and for its flocculating action.