The main goal of waste water treatment is to minimize the burden on the receiving watercourses by removing all organic, oxygen-consuming compounds and nutrients. In municipal waste water treatment plants, waters are mostly treated with physical, biological chemical processes, where lime products are used for controlling the pH and alkalinity, precipitating nutrients, handling sludge and removing odors.
The pH and alkalinity of water can be raised with lime products. Lime products differ from each other chemically and affect the process and the end result in different ways.
Calcium carbonate is slightly caustic and it dissolves slowly. The product works best when ground fine and when the pH of the waste water is less than 6.5. The product dosage is controlled by the flow rate. Calcium oxide and calcium hydroxide are strongly caustic. With these products the pH level of waste water can easily be regulated to the desirable level. The chemical reactions are fast, therefore the pH signal can be used for controlling the dosage.