Lime treatment is a common process in wastewater reclamation plants. It is the first process applied to secondary-treated municipal wastewater at the Potable Water Reuse Demonstration Plant in Denver, Colorado; Water Factory 21 in Orange County, California; the Fred Hervey Reclamation Plant in El Paso, Texas; and the Upper Occoquan Sewage Authority reclamation plant in Centreville, Virginia. Lime treatment provides the following improvements to a wastewater: 1. Clarification, by colloid destabilization and the sweeping action of precipitation floc. 2. Disinfection, by inactivation of virus and bacteria at high pH and the removal of infested turbidity during clarification. 3. Removal of undesirable inorganic constituents, by the interaction of lime or other treatment chemicals with the wastewater. The subject of this paper is the removal of the undesirable constituent, calcium.