Data Characteristics
Data Characteristics Unit of measure used Unit of measure used Power code Power code Concepts & Classifications Concepts & Classifications Key statistical concept Key statistical conceptLast updated: August 30, 2023
Contact: ENV.Stat@oecd.org
This dataset provides information on the level of public equipment installed by countries to managed and abate water pollution. It shows the percentage of national population connected to "public" sewerage networks and related treatment facilities, and the percentage of national population connected to "public" wastewater treatment plants, and the degree of treatment. Connected here means actually connected to a wastewater plants through a public sewage network. Individual private treatment facilities such as septic tanks are not covered here. When analysing these data, it should be kept in mind that the optimal connection rate is not necessarily 100 per cent; it may vary among countries and depends on geographical features and on the spatial distribution of habitats. The interpretation of those data should take into account some variations in countries' definitions, as reflected in metadata.
Source for non-OECD countries: UNSD, Country Files from the UNSD/UNEP data collection on environment statistics (available at: https://unstats.un.org/unsd/envstats/country_files; Date of last update: 16 May 2023).
Australia: no data is available to produce estimates for rural areas/utilities (the rural population connected to sewerage treatment is very small). From 2017-18 data have been imputed using the ratio of population receiving sewerage/water supply (constant at about 93.8% level in the past years). For more information see http://www.bom.gov.au/water/npr/
Canada: Before 2013, definitions for categories no-treatment, primary treatment and tertiary treatment varied slightly. As of 2019 a new data source has been used. Independent wastewater treatment includes private septic systems and smaller public systems. Once analysis is complete on the split between smaller public systems and those on private (septic) systems minor revisions will be needed.
Chile: Data refer only to population living in urban areas served by sanitary companies. Data is therefore not comparable with other countries. Primary treatment includes primary treatment with disinfection and submarine emissaries. Secondary treatment includes aerated lagoons. Tertiary treatment includes activated sludge (because this system has a disinfection phase to meet the standard of 1000FC/100ml, but it does not have nutrients treatment).
Colombia: Data refers only to urban centres and is estimated using total treated flows and total discharges.
Costa Rica: For more information see https://da.go.cr/estadisticas-e-indicadores-del-agua/
Czech Republic: For more information see http://eagri.cz/public/web/en/mze/water/water-management/
Denmark: Data refers only to municipal wastewater
Estonia: For more information , see http://www.keskkonnaagentuur.ee/
France: Data on the share of the population connected to the public wastewater treatment is based on a 2008 survey which has not been updated. Data for treatment types comes from a database put in place for the implementation of the European Directive No 271/1991 concerning wastewater treatment. Calculations for treatment types are based on the maximum entry load in population equivalents. For each year, starting in 2010, the percentage by treatment type is estimated assuming a constant total of 82%, estimated in 2008, of the population connected to public sewage. For more information see http://assainissement.developpement-durable.gouv.fr/services.phps
Germany: Before 1991 data refer to western Germany only. Unspecified treatment refers to population connected to industrial or foreign wastewater treatment plants or cesspits (total public sewerage and public total treatment include population whose wastewater is transported from independent storage tanks to wastewater treatment plants by means of trucks)
Iceland: Primary treatment includes 3.2% of preliminary treatment.
Ireland: Pre-2011 data are assumed to be of lower quality as they are based on population equivalents rather than actual population. 2011 onwards: change in methodology with data based on actual population. For more information see http://www.epa.ie/ ; http://www.epa.ie/pubs/reports/water/wastewater/ ; http://www.cso.ie/ and
http://www.cso.ie/en/census/census2011reports/census2011profile4theroofoverourheads-housinginireland.
The Environmental Protection Agency publishes a comprehensive national report on urban waste water treatment in Ireland each year and these reports are available on the Environmental Protection Agency's website at http://www.epa.ie/pubs/reports/water/wastewater
Japan: Secondary treatment in 1980 may include data for primary and tertiary treatment. 2010-2020 data does not include some municipalities that were unable to carry out a survey because of an earthquake. For more information: http://www.mlit.go.jp/ (Ministry of Land, Infrastructure, Transport and Tourism)
Korea: There is no official information on independent treatment. The large increase of tertiary treatment between 2012 and 2013 is due to the entering into force and the implementation of a regulation on public sewage. For more information see: Korea Statistical Information service (http://kosis.kr/) and Environmental Statistic Information System (http://stat.me.go.kr/).
Latvia: The population using independent treatment is computed as the difference between the total population and the number of inhabitants who reported, in surveys by water using operators, to be connected to treatment plants. In agglomerations with population equivalent of more than 2000 the percentage of population connected to the centralised sewerage system is increasing and, as a result, the percentage benefitting from independent treatment is decreasing in the last years. The main areas for investment in 2014 - 2020 are the extension and rehabilitation of water and wastewater networks in agglomerations with population equivalent of more than 10000 and in agglomerations with population equivalent 2000 - 10000 where network coverage is below 100%. Increasing household connections to centralised systems is one of the main challenges to which the country is confronted. Further information can be found in http://www.meteo.lv/fs/CKFinderJava/userfiles/files/Vide/Udens/notekudeni/2014_
ZINOJUMS_NOTEKUD_PARSKATS.pdf, http://parissrv.lvgmc.lv/public_reports
Lithuania: Wastewater from private households includes run-off rainwater.
Luxembourg: Primary treatment includes independent primary treatment. For more information see http://www.statistiques.public.lu/stat/ReportFolders/ReportFolder.aspx?IF_Language=fra&MainTheme=1&FldrName=3&RFPath=66
Mexico: There is no official information about population connected to wastewater treatment plants. Estimates are based on treated wastewater. For more information: http://www.conagua.gob.mx/ , http://sina.conagua.gob.mx/sina/ ,
New Zealand: 2014 data and older: data is based on the total of reported populations for the areas served by individual treatment plants, as used in New Zealand's greenhouse gas inventory. This is likely to be a low-end estimate (uncertainty from 0 to +6%) as the total known to have public connections or septic tanks is 94% (independent treatment in the last available year is estimated as 94% less total treatment), leaving 6% of the population unaccounted for. There has been a very slow increase in the estimated percentage of population connected to public sewer systems, due to urban population growth. 2015 data: estimations based on data for 85% of the population. Data by type of treatment is not available because standards are set at the local level and there is no uniformity across the country. For more information see http://www.waternz.org.nz/WWTPInventory and http://www.stats.govt.nz/.
Norway: Break in series in 2007: before 2007 the type of treatment is estimated with simplifying assumptions. Further information: https://www.ssb.no/en/avlut et http://www.ssb.no/natur-og-miljo/artikler-og-publikasjoner/kommunale-avlop
Portugal : data exclude overseas territories.
Slovak Republic: For more information see http://www.enviroportal.sk/indicator/detail?id=1784
http://www.enviroportal.sk/indicator/detail?id=1349
https://www.enviroportal.sk/spravy/index
Slovenia: the large difference in connection to secondary and tertiary treatment between 2020 and 2021 is due to a reclassification of treatment plants.
Sweden: For more information: http://www.scb.se/
Switzerland: For more information see https://www.bafu.admin.ch/bafu/fr/home/themes/eaux.html ,
https://www.vsa.ch/fr/publications/shop/produkt/couts-et-prestations-de-lassainissement/
United States: Primary treatment may include ocean outfalls and some biological treatment. Tertiary treatment includes 2-3% of non-discharge treatment, e.g. lagoons, evaporation ponds. Exclude rural areas served by Onsite Disposal Systems
England and Wales: Data refer to the financial year (April to March) until 2000. Independent treatment in 2012 is estimated by assuming that there are 2 persons per property.
Argentina: data are estimates for urban areas only. Data is not available on independent treatment.
Georgia: Data does not include treatment plants located on the territory of the Abkhazia region.
Last updated: August 30, 2023
Contact: ENV.Stat@oecd.org
This dataset provides information on the level of public equipment installed by countries to managed and abate water pollution. It shows the percentage of national population connected to "public" sewerage networks and related treatment facilities, and the percentage of national population connected to "public" wastewater treatment plants, and the degree of treatment. Connected here means actually connected to a wastewater plants through a public sewage network. Individual private treatment facilities such as septic tanks are not covered here. When analysing these data, it should be kept in mind that the optimal connection rate is not necessarily 100 per cent; it may vary among countries and depends on geographical features and on the spatial distribution of habitats. The interpretation of those data should take into account some variations in countries' definitions, as reflected in metadata.
Source for non-OECD countries: UNSD, Country Files from the UNSD/UNEP data collection on environment statistics (available at: https://unstats.un.org/unsd/envstats/country_files; Date of last update: 16 May 2023).
Australia: no data is available to produce estimates for rural areas/utilities (the rural population connected to sewerage treatment is very small). From 2017-18 data have been imputed using the ratio of population receiving sewerage/water supply (constant at about 93.8% level in the past years). For more information see http://www.bom.gov.au/water/npr/
Canada: Before 2013, definitions for categories no-treatment, primary treatment and tertiary treatment varied slightly. As of 2019 a new data source has been used. Independent wastewater treatment includes private septic systems and smaller public systems. Once analysis is complete on the split between smaller public systems and those on private (septic) systems minor revisions will be needed.
Chile: Data refer only to population living in urban areas served by sanitary companies. Data is therefore not comparable with other countries. Primary treatment includes primary treatment with disinfection and submarine emissaries. Secondary treatment includes aerated lagoons. Tertiary treatment includes activated sludge (because this system has a disinfection phase to meet the standard of 1000FC/100ml, but it does not have nutrients treatment).
Colombia: Data refers only to urban centres and is estimated using total treated flows and total discharges.
Costa Rica: For more information see https://da.go.cr/estadisticas-e-indicadores-del-agua/
Czech Republic: For more information see http://eagri.cz/public/web/en/mze/water/water-management/
Denmark: Data refers only to municipal wastewater
Estonia: For more information , see http://www.keskkonnaagentuur.ee/
France: Data on the share of the population connected to the public wastewater treatment is based on a 2008 survey which has not been updated. Data for treatment types comes from a database put in place for the implementation of the European Directive No 271/1991 concerning wastewater treatment. Calculations for treatment types are based on the maximum entry load in population equivalents. For each year, starting in 2010, the percentage by treatment type is estimated assuming a constant total of 82%, estimated in 2008, of the population connected to public sewage. For more information see http://assainissement.developpement-durable.gouv.fr/services.phps
Germany: Before 1991 data refer to western Germany only. Unspecified treatment refers to population connected to industrial or foreign wastewater treatment plants or cesspits (total public sewerage and public total treatment include population whose wastewater is transported from independent storage tanks to wastewater treatment plants by means of trucks)
Iceland: Primary treatment includes 3.2% of preliminary treatment.
Ireland: Pre-2011 data are assumed to be of lower quality as they are based on population equivalents rather than actual population. 2011 onwards: change in methodology with data based on actual population. For more information see http://www.epa.ie/ ; http://www.epa.ie/pubs/reports/water/wastewater/ ; http://www.cso.ie/ and
http://www.cso.ie/en/census/census2011reports/census2011profile4theroofoverourheads-housinginireland.
The Environmental Protection Agency publishes a comprehensive national report on urban waste water treatment in Ireland each year and these reports are available on the Environmental Protection Agency's website at http://www.epa.ie/pubs/reports/water/wastewater
Japan: Secondary treatment in 1980 may include data for primary and tertiary treatment. 2010-2020 data does not include some municipalities that were unable to carry out a survey because of an earthquake. For more information: http://www.mlit.go.jp/ (Ministry of Land, Infrastructure, Transport and Tourism)
Korea: There is no official information on independent treatment. The large increase of tertiary treatment between 2012 and 2013 is due to the entering into force and the implementation of a regulation on public sewage. For more information see: Korea Statistical Information service (http://kosis.kr/) and Environmental Statistic Information System (http://stat.me.go.kr/).
Latvia: The population using independent treatment is computed as the difference between the total population and the number of inhabitants who reported, in surveys by water using operators, to be connected to treatment plants. In agglomerations with population equivalent of more than 2000 the percentage of population connected to the centralised sewerage system is increasing and, as a result, the percentage benefitting from independent treatment is decreasing in the last years. The main areas for investment in 2014 - 2020 are the extension and rehabilitation of water and wastewater networks in agglomerations with population equivalent of more than 10000 and in agglomerations with population equivalent 2000 - 10000 where network coverage is below 100%. Increasing household connections to centralised systems is one of the main challenges to which the country is confronted. Further information can be found in http://www.meteo.lv/fs/CKFinderJava/userfiles/files/Vide/Udens/notekudeni/2014_
ZINOJUMS_NOTEKUD_PARSKATS.pdf, http://parissrv.lvgmc.lv/public_reports
Lithuania: Wastewater from private households includes run-off rainwater.
Luxembourg: Primary treatment includes independent primary treatment. For more information see http://www.statistiques.public.lu/stat/ReportFolders/ReportFolder.aspx?IF_Language=fra&MainTheme=1&FldrName=3&RFPath=66
Mexico: There is no official information about population connected to wastewater treatment plants. Estimates are based on treated wastewater. For more information: http://www.conagua.gob.mx/ , http://sina.conagua.gob.mx/sina/ ,
New Zealand: 2014 data and older: data is based on the total of reported populations for the areas served by individual treatment plants, as used in New Zealand's greenhouse gas inventory. This is likely to be a low-end estimate (uncertainty from 0 to +6%) as the total known to have public connections or septic tanks is 94% (independent treatment in the last available year is estimated as 94% less total treatment), leaving 6% of the population unaccounted for. There has been a very slow increase in the estimated percentage of population connected to public sewer systems, due to urban population growth. 2015 data: estimations based on data for 85% of the population. Data by type of treatment is not available because standards are set at the local level and there is no uniformity across the country. For more information see http://www.waternz.org.nz/WWTPInventory and http://www.stats.govt.nz/.
Norway: Break in series in 2007: before 2007 the type of treatment is estimated with simplifying assumptions. Further information: https://www.ssb.no/en/avlut et http://www.ssb.no/natur-og-miljo/artikler-og-publikasjoner/kommunale-avlop
Portugal : data exclude overseas territories.
Slovak Republic: For more information see http://www.enviroportal.sk/indicator/detail?id=1784
http://www.enviroportal.sk/indicator/detail?id=1349
https://www.enviroportal.sk/spravy/index
Slovenia: the large difference in connection to secondary and tertiary treatment between 2020 and 2021 is due to a reclassification of treatment plants.
Sweden: For more information: http://www.scb.se/
Switzerland: For more information see https://www.bafu.admin.ch/bafu/fr/home/themes/eaux.html ,
https://www.vsa.ch/fr/publications/shop/produkt/couts-et-prestations-de-lassainissement/
United States: Primary treatment may include ocean outfalls and some biological treatment. Tertiary treatment includes 2-3% of non-discharge treatment, e.g. lagoons, evaporation ponds. Exclude rural areas served by Onsite Disposal Systems
England and Wales: Data refer to the financial year (April to March) until 2000. Independent treatment in 2012 is estimated by assuming that there are 2 persons per property.
Argentina: data are estimates for urban areas only. Data is not available on independent treatment.
Georgia: Data does not include treatment plants located on the territory of the Abkhazia region.