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Terms & Synonyms

Official WHO Definition

Liquid waste discharged from homes, commercial premises and similar sources to individual disposal systems or to municipal sewer pipes, and which contains mainly human excreta and used water (WHO 2006a).The used water and water-carried solids from a community (including used water from industrial processes) that flow to a treatment plant (WHO 2006b).

Other Definitions


Interpretations and Explanations

When produced mainly by household and commercial activities, it is called domestic or municipal wastewater or domestic sewage. In this context, domestic sewage does not contain industrial effluents at levels that could pose threats to the functioning of the sewerage system, treatment plant, public health or the environment (WHO 2006a).


by UNESCO Water Portal newsletter (13 April 2007)

Wastewater has been defined as the water discharged from a community after it has been fouled by various uses and containing waste, i.e. liquid or solid matter. It may be a combination of the liquid or water-carried domestic, municipal and industrial wastes, together with such groundwater, surface water and storm water as may be present.

Population growth, rapid urbanization, and increasing water supply and sanitation provision will all generate increased problems from wastewater pollution.

It has been estimated that the total global volume of wastewater produced in 1995 was in excess of 1,500 km3.

There is the understanding that each litre of wastewater pollutes at least 8 litres of freshwater, so that on this basis some 12,000 km3 of the globe’s water resources is not available for use each year. If this figure keeps pace with population growth, then with an anticipated population of 9 billion by 2050, the world’s water resources would be reduced by some 18,000 km3 annually.

At present, only about a tenth of the domestic wastewater in developing countries is collected and only about a tenth of existing wastewater treatment plants operates reliably and efficiently.

Some of the damage associated with inadequate handling of wastewater are:

  • increased direct and indirect costs caused by increased illness and mortality
  • higher costs for producing drinking and industrial water, resulting in higher tariffs
  • loss of income from fisheries and aquaculture
  • poor water quality, which deters tourists, immediately lowering income from tourism
  • loss of valuable biodiversity
  • loss in real estate values, when the quality of the surroundings deteriorates: especially important for slum dwellers where housing is the primary asset.

Untreated sewage affects over 70% of coral reefs, precious habitats are disappearing and biodiversity is decreasing, fishing and agricultural potential are being lost, while poor water quality is reducing income from tourism and the value of real estate.

The global burden of human disease caused by sewage pollution of coastal waters has been estimated at 4 million lost person-years annually.

In March 2003, the World Panel on Financing Water Infrastructure estimated that US $56 billion was needed annually for wastewater treatment in order to achieve the target on sanitation.

In the State of Mexico (Mexico), wastewater is generated approximately at the rate of 30 m3 per second (m3/s), about 19% of which is directly discharged without any kind of treatment.

Information from the International Glossary of Hydrology (http://www.cig.ensmp.fr/~hubert/glu/aglo.htm), the 1st United Nations World Water Development Report: ‘Water for People, Water for Life’ (http://www.unesco.org/water/wwap/wwdr1/), the 2nd United Nations World Water Development Report: 'Water, a shared responsibility' (http://www.unesco.org/water/wwap/wwdr2/table_contents.shtml) and from the United Nations Environment Programme (UNEP) Magazine ‘Our Planet’ (http://www.unep.org/OurPlanet/imgversn/144/images/Our_Planet_14.4_english.pdf) [PDF format – 1.11 MB]


WHO (2006a) Guidelines for the safe use of wastewater, excreta and greywater.WHO (2006b) Health aspects of plumbing.

WHO Lexicon page (translations and examples)

See also

External Resources

Guidelines for the Safe Use of Wastewater, Excreta and Greywater (By the World Health Organization (WHO); © 2006 WHO)

Direct Link: http://www.who.int/water_sanitation_health/wastewater/gsuww/en/index.html

Wastewater use

This World Health Organization’s (WHO) section explains what wastewater use is, contains the WHO Guidelines for the safe use of wastewater, excreta and greywater, and related documents.


This website of the Environmental Protection Agency (EPA), of the Queensland Government (Australia), contains answers to different questions such as: Where does wastewater come from? What is wastewater treatment? What happens in a sewage treatment plant? How is waste water managed? Is wastewater treatment effective?
What are future directions? / How can I help?
For a complete list of water links around the world visit http://www.unesco.org/water/water_links/ (UNESCO Water Portal)


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