Reference metadata describe statistical concepts and methodologies used for the collection and generation of data. They provide information on data quality and, since they are strongly content-oriented, assist users in interpreting the data. Reference metadata, unlike structural metadata, can be decoupled from the data.
The indicator is part of the EU Sustainable Development Goals (SDG) indicator set. It is used to monitor progress towards SDG 6 on clean water and sanitation, which is embedded in the European Commission’s 2024-2029 priorities under 'Sustaining our quality of life: Food security, water and nature'.
Among other things, SDG 6 calls for ensuring universal access to safe and affordable drinking water, sanitation and hygiene, and ending open defecation. It also aims at improving water quality and water-use efficiency and encouraging sustainable abstractions and supply of freshwater. SDG 11 aims to renew and plan cities and other human settlements so that they offer opportunities for all, with access to basic services, energy, housing, transportation, green public spaces and others, while improving resource use and reducing environmental impacts.
The indicator can be considered similar to global SDG indicator 6.3.1 "Proportion of wastewater safely treated".
Protection of water resources, water ecosystems and of drinking and bathing water is at the cornerstone of EU environmental policy, as confirmed in the proposed 8th Environment Action Programme. EU water policy provides a framework to comprehensively address water protection and for achieving good status for inland surface waters, transitional waters, coastal waters and groundwater. The EU health and food safety policy also contributes to high standards on water and sanitation in terms of preventing the spread of communicable diseases. The Urban Waste-Water Treatment Directive regulates the collection, treatment and discharge of domestic as well as industrial urban wastewaters.
The EU in its external relations, its development cooperation policy (through the European consensus and the Agenda for Change), the European Neighbourhood Policy and the EU Enlargement Policy is supporting third countries in the achievement of this sustainable development goal through bilateral assistance programmes or regional initiatives. The EU Enlargement Policy promotes the extension of EU norms to candidate countries covering water quality, waste water treatment, but also water management and flood prevention.
4.1. Data description
The indicator measures the percentage of population connected to wastewater treatment systems with at least secondary treatment. Thereby, waste water from urban or other sources is treated by a process generally involving biological treatment with a secondary settlement or other process that removes organic material and reduces its biochemical oxygen demand (BOD) by at least 70 % and chemical oxygen demand (COD) by at least 75 %.
4.2. Unit of measure
% of population.
4.3. Reference Period
Calendar year.
4.4. Accuracy - overall
The indicator is produced according to the high-level quality standards of European Statistics. Details on accuracy can be found in the metadata of the source datasets (see link to related metadata).
4.5. Source data
4.5.1. Source data - Organisation
ESS (OECD/ESTAT joint questionnaire)
4.5.2. Source data - Comment
Data source: Water Statistics of the European Statistical System (ESS).
Data provider: Statistical Office of the European Union (Eurostat), based on data reported by countries with OECD/ESTAT joint questionnaire.
5.1. Frequency of dissemination
5.1.1. Frequency of dissemination - Grade
Every year
5.1.2. Frequency of dissemination - Comment
The indicator is updated every year with annual data. Complete and updated ESS data release information can be accessed via Eurostat release calendar.
5.2. Timeliness
5.2.1. Timeliness - Grade
T+2 years
5.2.2. Timeliness - Comment
New data points are disseminated within 18 months after the latest reference year.
6.1. Reference area
6.1.1. Reference Area - Grade
< 75% EU MS or no EU aggregate
6.1.2. Reference Area - Comment
Data are presented for all EU Member States except Bulgaria, Germany, Spain, France, Croatia, Italy, Cyprus, Luxembourg, Portugal and Sweden; plus Norway,Albania Serbia and Türkiye.
6.2. Comparability - geographical
6.2.1. Comparability - geographical - Grade
All EU MS
6.2.2. Comparability - geographical - Comment
Data are comparable between all EU Member States respectively other presented countries.
6.3. Coverage - Time
6.3.1. Time Coverage - Grade
> 10 years
6.3.2. Time Coverage - Comment
Presented time series starts in 2000.
6.4. Comparability - over time
6.4.1. Comparability - over time - Grade
> 4 data points
6.4.2. Comparability - over time - Comment
Length of comparable time series without methodological break is longer than 4 data points. Comparability over time is generally good, but can be limited due to data gaps and breaks in series.
7.1. Dissemination format - Publications
Analysis of indicator is presented in Eurostat's annual monitoring report on Sustainable development in the EU (progress towards SDGs in the EU context).
The indicator measures the percentage of population connected to wastewater treatment systems with at least secondary treatment. Thereby, waste water from urban or other sources is treated by a process generally involving biological treatment with a secondary settlement or other process that removes organic material and reduces its biochemical oxygen demand (BOD) by at least 70 % and chemical oxygen demand (COD) by at least 75 %.
14 April 2025
Not Applicable
Not Applicable
Not Applicable
Calendar year.
The indicator is produced according to the high-level quality standards of European Statistics. Details on accuracy can be found in the metadata of the source datasets (see link to related metadata).
