Water clarification is the process for making water suitable for a specific application or for discharge into public waters. Untreated water can contain a variety of contaminants that require removal prior to end use, including clays, heavy metals, color bodies, organics, pathogenic bacteria, giardia cysts, and viruses.

Clarification for the production of drinking water utilizes the combined action of chemical coagulation, flocculation, sedimentation, filtration, and disinfection. Wastewater clarification differs from drinking water clarification in that the former is less likely to utilize chemical coagulation, frequently utilizes biological processes for secondary treatment, and generally uses some type of sludge dewatering .