4. Chemical precipitation treatments

Chemical precipitation encompasses a number of processes, all of which apply Bertholet's law: a soluble reagent is added to water which, by permutation or combination with pre-existing undesirable ions, forms an insoluble or very slightly soluble compound which precipitates to its solubility limit (determined by the solubility product, which can vary considerably according to temperature, ionic strength, the nature of other dissolved ions, etc.).

The end result of these precipitation reactions, often combined with neutralization of the rejects, is always solid-liquid separation, using conventional decantation, flotation or even filtration processes.

To speed up chemical reaction kinetics and increase treatment efficiency, it is often necessary to use seeding techniques facilitated by the use of sludge-contact decanters (Turbocirculator type),...