Wastewater is the polluted form of water generated from rainwater runoff and human activities. It is also called sewage. It is typically categorized by the manner in which it is generated—specifically, as domestic sewage, industrial sewage, or storm sewage (stormwater).

wastewater treatment

Table of Contents

References & Edit History Quick Facts & Related Topics

Images & Videos

How is sewage transformed into drinkable water?

Understand global warming as a factor in the decline of dissolved oxygen in the ocean

Learn about primary, secondary, and tertiary wastewater treatment steps and how a Secchi disk tests purity

Discover

United States Electoral College votes by state

How Many Electoral College Votes Does Each U.S. State Have?

9 of the World’s Deadliest Spiders

The Sun Was Eaten: 6 Ways Cultures Have Explained Eclipses

Vietnam War. U.S. President Lyndon B. Johnson awards the Distinguished Service Cross to First Lieutenant Marty A. Hammer, during a visit to military personnel, Cam Ranh Bay, South Vietnam, October 26, 1966. President Johnson

Vietnam War Timeline

Solar Eclipse, Eclipse, Solar Flare, Outer Space, Astronomy

What Causes Lunar and Solar Eclipses?

How Is Coffee Decaffeinated?

Periodical Cicada, Adult, Magicicada spp. Requires 17 years to complete development. Nymph splits its skin, and transforms into an adult. Feeds on sap of tree roots. Northern Illinois Brood. This brood is the largest emergence of cicadas anywhere

Why Do Some Cicadas Appear Only Every 17 Years?

Science & Tech

wastewater treatment

Q: How is wastewater generated?

Domestic wastewater results from water use in residences, businesses, and restaurants. Industrial wastewater comes from discharges by manufacturing and chemical industries. Rainwater in urban and agricultural areas picks up debris, grit, nutrients, and various chemicals, thus contaminating surface runoff water. Read more below: Sources of water pollution

Q: What are the common pollutants present in wastewater?

Wastewater contains a wide range of contaminants. The quantities and concentrations of these substances depend upon their source. Pollutants are typically categorized as physical, chemical, and biological. Common pollutants include complex organic materials, nitrogen- and phosphorus-rich compounds, and pathogenic organisms ( bacteria , viruses , and protozoa ). Synthetic organic chemicals, inorganic chemicals, microplastics, sediments, radioactive substances, oil, heat, and many other pollutants may also be present in wastewater.

Q: How is wastewater processed at a sewage treatment facility?

Sewage treatment facilities use physical, chemical, and biological processes for water purification . The processes used in these facilities are also categorized as preliminary, primary, secondary, and tertiary. Preliminary and primary stages remove rags and suspended solids. Secondary processes mainly remove suspended and dissolved organics. Tertiary methods achieve nutrient removal and further polishing of wastewater. Disinfection, the final step, destroys remaining pathogens. The waste sludge generated during treatment is separately stabilized, dewatered, and sent to landfills or used in land applications.

Q: Why is wastewater resource recovery important?

Wastewater is a complex blend of metals, nutrients, and specialized chemicals. Recovery of these valuable materials can help to offset a community’s growing demands for natural resources. Resource recovery concepts are evolving, and researchers are investigating and developing numerous technologies. Reclamation and reuse of treated water for irrigation , groundwater recharge, or recreational purposes are particular areas of focus.

Also known as: sewage treatment

Written by Archis Ambulkar, Jerry A. NathansonSee All

Fact-checked by The Editors of Encyclopaedia Britannica

Article History

Cloaca Maxima

See all media

Category: Science & Tech

Also called:: sewage treatment

Related Topics:: sedimentation tank; trickling filter; activated-sludge method; sludge; floc

See all related content →

What is wastewater?

How is wastewater generated?

What are the common pollutants present in wastewater?

How is wastewater processed at a sewage treatment facility?

Why is wastewater resource recovery important?

wastewater treatment, the removal of impurities from wastewater, or sewage, before it reaches aquifers or natural bodies of water such as rivers, lakes, estuaries, and oceans. Since pure water is not found in nature (i.e., outside chemical laboratories), any distinction between clean water and polluted water depends on the type and concentration of impurities found in the water as well as on its intended use. In broad terms, water is said to be polluted when it contains enough impurities to make it unfit for a particular use, such as drinking, swimming, or fishing. Although water quality is affected by natural ...(100 of 7680 words)

Access the full article

Help support true facts by becoming a member.