Population connected to at least secondary wastewater treatment (Indicator)

Key messages: Since 2000, the proportion of the EU population connected to wastewater treatment has been steadily increasing, with 81% connected to at least secondary wastewater treatment in 2021.

Population connected to wastewater treatment at least at the secondary level in the EU-27, 2000–2021

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There are progressive levels of treatment that urban wastewater can undergo in wastewater treatment plants. Eurostat reports these levels as primary, secondary and tertiary. Conventional primary wastewater treatment mainly removes suspended solids, while the second level treats nutrients, pathogens and some chemicals. The tertiary level is more tailored to the specific case; this can involve, for example, more intensive nutrient removal and disinfection.

Since the Urban Wastewater Treatment (UWWT) Directive was implemented, the proportion of the population connected to wastewater treatment has been steadily increasing. As a result, by 2021, 81% of the EU population was connected to wastewater treatment at the secondary level at least. This development contributes to the improvement of freshwater quality in European surface water bodies.

Going forward, the Commission has proposed a revision of the UWWT Directive in October 2022 in attempt to tackle micro-pollutants and microplastics in wastewater by introducing new standards and monitoring requirements. More specifically, the proposal introduces a quaternary treatment level to eliminate the broadest possible spectrum of micro-pollutants. This would help to reduce the occurrence of substances of concern in effluents from wastewater treatment plants.

Please consult the relevant indicators and signals below for a more comprehensive overview on the topic.

The data on the EU population connected to at least secondary wastewater treatment were retrieved from the Eurostat table SDG_06_20.

‘Secondary treatment' refers to a process generally involving biological treatment with a secondary settlement or other process, resulting in the removal of organic material that reduces the biochemical oxygen demand (BOD) by at least 70% and the chemical oxygen demand (COD) by at least 75%.

The data reported to Eurostat differ from those reported under the UWWT Directive, owing to different reporting requirements. (According to the UWWT Directive, EU countries are required to collect and treat wastewater from urban areas above 2,000 population equivalents.) Depending on the size of the treatment plant and the sensitivity of the local environment, it may be necessary for wastewater to be treated at a level higher than the secondary level.

Data from the UWWT Directive show that, in 2018, 82% of Europe’s urban wastewaters were collected and treated in line with EU standards.

More information is available at the Freshwater Information System for Europe and Eurostat websites.

References and footnotes

EU, 1991, Council Directive 91/271/EEC of 21 May 1991 concerning urban waste-water treatment (OJ L 135, 30.5.1991, pp. 40-52).
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EC, 2022, Proposal for a DIRECTIVE OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL concerning urban wastewater treatment (recast), (
https://environment.ec.europa.eu/system/files/2022-10/Proposal%20for%20a%20Directive%20concerning%20urban%20wastewater%20treatment%20%28recast%29.pdf)
accessed 8 May 2023, European Commission.
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Eurostat, 2023, ‘Population connected to at least secondary wastewater treatment’, Eurostat (
https://ec.europa.eu/eurostat/databrowser/view/SDG_06_20__custom_2644378/bookmark/table?lang=en&bookmarkId=7a5cd3ed-6dda-48f7-8ebf-be77ce9b2277)
accessed 9 January 2024.
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Population connected to at least secondary wastewater treatment (Indicator)

Population connected to wastewater treatment at least at the secondary level in the EU-27, 2000–2021

Relevant objectives under the Chemicals Strategy for Sustainability

Other relevant indicators and signals

References and footnotes