Water Treatment A precipitate is a solid that separates from solution as the result of a chemical reaction. The chemical reaction that produces a precipitate is called a precipitation reaction. Precipitation reactions occur widely in nature. Many naturally occurring minerals are formed as the result of precipitation reactions.
Precipitation reactions are also widely used in industry.
Chemical precipitation used in water treatment is a good example. Water contains many impurities, including tiny suspended particles called colloids. Colloids are removed from water by a series of processes called coagulation, flocculation, and sedimentation. Coagulation occurs when chemicals added to the water form one or more precipitates. Flocculation is the process by which the colloidal impurities adhere to the precipitate.