Water purification

Water purification removes contaminants to make water suitable for a specified use, such as drinking, industrial processes, or environmental discharge. Its methods depend on the contaminants present and the required water quality.

Coagulation and flocculation: Water-treatment processes that destabilize suspended particles and gather them into larger clumps for removal. These steps make fine particles easier to remove before filtration or settling.
Drinking water quality standards: Regulatory limits and guidelines for contaminants in water supplied for human consumption. These standards define the targets that drinking-water treatment must meet.
Drinking water: Water treated and supplied for human consumption and related domestic uses. Purification for consumption must control pathogens and regulated chemical contaminants.
Water filtration: The separation of particles or substances from water by passing it through a porous medium or membrane. Filtration is one treatment operation, whereas purification can combine many operations.
Sedimentation: The separation of suspended particles from a fluid by allowing gravity to make them settle. Settling removes flocs formed during pretreatment without requiring a fine filter.
Water quality: The physical, chemical, and biological characteristics of water in relation to a particular use. Purification is judged against the quality needed for its intended purpose.
Wastewater treatment: Processes that remove contaminants from used water before discharge or reuse. It applies purification principles to municipal and industrial effluent.
Water softening: Treatment that reduces water hardness, usually by removing calcium and magnesium ions or replacing them with sodium ions. Softening targets hardness specifically and does not by itself make water safe to drink.
Rapid sand filter: A granular-media filter that removes particles from water as it passes through a bed of sand and supporting layers. It is a widely used filtration step after coagulation and sedimentation.
Turbidity: A measure of water cloudiness caused by suspended particles that scatter light. Turbidity indicates particle removal needs and can interfere with disinfection.

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