Indicator 6.3.1 “Proportion of domestic and industrial wastewater flow safely treated”

Target 6.3 seeks to halve the proportion of untreated wastewater discharged into our water bodies – this page explains why and how to monitor progress towards the target.

The indicator at a glance

Indicator 6.3.1 tracks the proportion of wastewater flows from households, services and industrial economic activities that are safely treated before it is discharged into the environment. The treatment can take place at the source (e.g. at the premises of a household or an industry) or through centralized wastewater treatment plants.

The household component includes both sewage and faecal sludge, treated on-site and off-site, and is monitored as part of the sanitary chain with direct links to indicator 6.2.1 on access to sustainably managed sanitation services.

The monitoring of the total and industrial components of indicator 6.3.1 relies on existing data from governments, reported either to the United Nations Statistics Division (UNSD) and the United Nations Environment Programme (UNEP), the Organisation for Economic Co-Operation and Development (OECD) or Eurostat.

Data on 6.3.1 are commonly collected by national line ministries and institutions (e.g. for Water, Sanitation, Environment, Health, Public Services, Planning, Housing, Infrastructure, Production), utilities and on-site service providers as well as the National Statistical Office (household surveys and registers of economic activities).

Available support 

The World Health Organization (WHO), the United Nations Human Settlements Programme (UN-Habitat) and the United Nations Statistics Division (UNSD) are the custodians of indicator 6.3.1. For any enquiries about available support, please contact their helpdesk.

Guidance on data collection and reporting

• UN-Habitat, WHO, UNSD: Monitoring methodology.
• Eurostat: Joint OECD/Eurostat Questionnaire on the State of the Environment (for EU countries).
• OECD: Joint OECD/Eurostat Questionnaire on the State of the Environment (for OECD countries).
• UNSD: UNSD/UNEP Questionnaire on Environment Statistics (for all other countries).
• UN-Water: Data collection process and timeline.

Online support

• UN-Habitat and WHO: Helpdesk (email, phone, video conference).
• National workshops in selected countries.
• Regional workshops.

Data and progress reporting

• UN-Water: SDG 6 Data Portal.
• WHO: 6.3.1 country data on domestic component.
• OECD: OECD Statistics (see Theme Environment > Water).
• Eurostat: Eurostat Environment Water Statistics.
• WHO and UN-Habitat on behalf of UN-Water: 2021 Progress Report (including infographics).