water purification

Introduction
Determining water quality
Process
- Pretreatment
- Other purification steps
- Industrial water purification
- Saline water purification
System configurations and improvements

References & Edit History Quick Facts & Related Topics

Images & Videos

Diagram of a water treatment plant showing the process from water inlet through mixing, coagulation, flocculation, settling, filtering, chemical treatment with chlorine, storage, and high-lift pumping to the distribution system.

Two large pipes discharge polluted, muddy water, illustrating water contamination and environmental pollution.

Diagram showing the municipal water treatment process, with water flowing from a natural source through intake screens, coagulation, flocculation, sedimentation, filtration, disinfection, and finally distribution as purified water, with waste removed at various stages.

How is sewage and industrial wastewater reclaimed for use?

Quizzes

water glass on white background. (drink; clear; clean water; liquid)

Water and its Varying Forms

Related Questions

How are clogged rapid filters cleaned by backwashing?
How can lead enter drinking water from plumbing?
How can radioactive materials contaminate drinking water?
How did polluted water become linked to cholera in the 19th century?
How did sand filtration and chlorination reduce cholera and typhoid fever?
How do primary secondary and tertiary wastewater treatments differ?
How do stream standards protect rivers and lakes from pollution?
How does Vibrio cholerae enter drinking-water supplies?
How does activated-carbon filtering remove some water contaminants?
How does chlorination disinfect drinking water?
How does cholera toxin cause severe fluid loss?
How does coagulation remove particles from drinking water?
How does contaminated drinking water spread cholera?
How does disinfection protect people from waterborne diseases?
How does flocculation help purify drinking water?
How does ozone disinfect drinking water?
How does reverse osmosis remove dissolved substances from water?
How is reverse osmosis used to make seawater suitable for drinking?
What are the main sources of water used by public water-treatment plants?
What happens at a water-treatment plant before water reaches homes?
What is the difference between slow sand filters and rapid sand filters?
Which foods can transmit cholera when prepared with contaminated water?
Which microorganisms can be killed during drinking-water disinfection?
Why are rapid dual-media filters commonly used in water-treatment plants?
Why are raw shellfish a possible source of cholera infection?
Why can groundwater still need treatment before people drink it?
Why can radon in groundwater be harmful after it is released into air?
Why can the El Tor biotype of Vibrio cholerae spread widely?
Why can turbidity make disinfection less effective?
Why do drinking-water standards include limits for turbidity?
Why do some communities add fluoride to public drinking water?
Why does surface water usually need more treatment than groundwater?
Why does ultraviolet disinfection not leave a residual in drinking water?
Why is a chlorine residual maintained in water-distribution systems?
Why is sludge removed from water-treatment tanks?
Why is wastewater disinfected before it is released into surface water?
Why is water purification important for public health?
Why must wastewater be treated before it is discharged into rivers or lakes?

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External Websites

Mustansiriyah University - Water Purification
Centers for Disease Control and Prevention - How Water Treatment Works
Open Oregon Educational Resources - Environmental Biology - Water Treatment
Princeton University - Water Purification
U.S. Environmental Protection Agency - Water Purification
Chemistry LibreTexts - Water Treatment
ODU Digital Commons - Water treatment: keeping it pure (PDF)
National Center for Biotechnology Information - PubMed Central - Household Water Purification: Low-Cost Interventions

water purification

public health

Also known as: water treatment

Written by

Archis Ambulkar

Author of Guidance for Professional Development in Drinking Water and Wastewater Industry and contributor to Oxford Research Encyclopedia of Environmental Science. Expert reviewer for...

Archis AmbulkarAll

Fact-checked by

Britannica Editors

Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....

Britannica Editors

Last updated

Oct. 10, 2026 •History

water purification, process by which undesired chemical compounds, organic and inorganic materials, and biological contaminants are removed from water. That process also includes distillation (the conversion of a liquid into vapour to condense it back to liquid form) and deionization (ion removal through the extraction of dissolved salts). One major purpose of water purification is to provide clean drinking water. Water purification also meets the needs of medical, pharmacological, chemical, and industrial applications for clean...

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