The principle technology to remove metals pollutants from wastewater is by chemical precipitation. Chemical precipitation includes two secondary removal mechanisms, coprecipitation and adsorption. Precipitation processes are characterized by the solubility of the metal to be removed. They are generally designed to precipitate trace metals to their solubility limits and obtain additional removal by coprecipitation and adsorption during the precipitation reaction.

There are many different treatment variables that affect these processes. They include the optimum pH, the type of chemical treatments used, and the number of treatment stages, as well as the temperature and volume of wastewater, and the chemical specifications of the pollutants to be removed. Each of these variables directly influences treatment objectives and costs. Treatability studies must be performed to optimize the relevant variables, so that goals are met and costs minimized.

In theory, the precipitation process has two steps, nucleation followed...