Progress on the proportion of domestic and industrial wastewater flows safely treated: mid-term status of SDG indicator 6.3.1 and acceleration needs, with a special focus on climate change, wastewater reuse and health

Table of Contents

• Abbreviations and acronyms 11
• Foreword by the Chair of UN-Water 12
• Foreword by UN-Habitat 13
• Executive summary 15
• Key messages 19
• 1. Wastewater monitoring and its importance to the SDGs and beyond 21
• 2. Methods and process 27
• 2.1. Total and industrial wastewater statistics 30
• 2.1.1. Total and industrial wastewater flows generated and safely treated 31
• 2.2. Domestic (household) wastewater estimates 34
• 3. Results and analysis 45
• 3.1. Frequency of harmonized data reporting 46
• 3.2. Total and industrial wastewater statistics 47
• 3.2.1. Total wastewater generated and safely treated 47
• 3.2.2. Industrial wastewater generated and safely treated 56
• 3.3. Domestic (household) wastewater estimates 59
• 4. Status and progress of SDG Indicator 6.3.1 67
• 4.1. Total and industrial wastewater statistics 68
• 4.2. Domestic (household) wastewater estimates 71
• 5. Two examples of SDG Target 6.3 cross-cutting issues 75
• 5.1. Total and industrial wastewater reuse and climate change adaptation and mitigation 76
• 5.2. Domestic wastewater and health 81
• 6. Conclusion 83
• References 85
• Annexes 89
• Annex 1: Wastewater terms and definitions relevant to this report 90
• Annex 2: Description of the five stages of the household wastewater conceptual framework 92
• Annex 3: Number of United Nations Member States reporting wastewater statistics (by volumetric and population-based variables) to UNSD/UNEP, Eurostat and OECD questionnaires (data compiled from all sources in April 2024) 94
• Annex 4: Changes over time in country estimates for safely treated household wastewater 95
• Annex 5: Volume of wastewater reuse reported in million m3/year, data source and reporting year. 99
• Annex 6: Country data (total and industrial wastewater) 101
• Annex 7: Country data (household wastewater) 106
• Annex 8: Regional and global data (household wastewater) 116
• Figures 9
• Figure 1. SDG Indicator 6.3.1 interlinkages with the other SDG 6 indicators. 25
• Figure 2. SDG Target 6.3.1 interlinkages with the other SDGs. 26
• Figure 3. SDG Indicator 6.3.1 data sources (orange), data inputs (light blue), data variables (dark blue) and global monitoring components (pink). 28
• Figure 4. UN-Habitat SDG Indicator 6.3.1 monitoring approach, with the wastewater databases and the number of countries provided by the different sources of data. 31
• Figure 5. Total and industrial flow diagram showing from left to right: the different point sources, the collecting systems and the treatments. 32
• Figure 6. Disaggregated variables used for the generation (left) and treatment (right) of wastewater used to report on SDG Indicator 6.3.1. 33
• Figure 7. Contributions of household and services wastewater to domestic wastewater generation. 35
• Figure 8. Conceptual framework for household wastewater monitoring. 37
• Figure 9. Example of greywater management (Government of India, 2021). 38
• Figure 10. Comparison of SDG indicators 6.2.1a (safely managed sanitation services) and 6.3.1 (safely treated domestic wastewater) for 2022. 41
• Figure 11. Household wastewater flow diagram for Iraq, 2022. 44
• Figure 12. Proportion of United Nations Member States (n=193) reporting data to the UNSD, OECD and Eurostat databases on total flows of wastewater generated and treated. 46
• Figure 13. Total wastewater flows generated (million m3) in 2022, by country, using a base-10 logarithmic scale on the x-axis. 48
• Figure 14. Total wastewater flow generated (million m3) in 2022 disaggregated by industrial and domestic sectors. (left) The 25 highest values and (right) the values of the other 60 countries. 49
• Figure 15. Number of countries and associated proportion of countries (over 193 Member States) that reported on the different variables for wastewater generation and treatment. 50
• Figure 16. Total wastewater flows treated (million m3) in 2022, by country, using a base-10 logarithmic scale on the x-axis. 51
• Figure 17. Total wastewater flow treated (million m3) in 2022 disaggregated by type and level of treatment. 52
• Figure 18. Screenshot of the OLAS dashboard showing some of the information available for a WWTP from Peru. 54
• Figure 19. Countries’ proportions of the total flow of wastewater treated versus the total flow of wastewater generated (%) for 2022, including safely treated wastewater (i.e. receiving at least secondary treatment). 55
• Figure 20. Estimated volumes of water consumption, wastewater generated, wastewater treated, wastewater discharged and wastewater untreated from the 150 industrial and urban facilities, in million m3 per year. 57
• Figure 21. Proportion of industrial wastewater flows treated and safely treated (%) in 2022. 58
• Figure 22. Estimated proportions of household wastewater safely treated, by year and region. 60
• Figure 23. Proportional representation of volumes of household wastewater safely treated (A), not safely treated (B) and undefined (C), by country and region. 61
• Figure 24. Breakdown of the global proportion of household wastewater flows generated, delivered to treatment facilities and safely treated by type of wastewater collection system. 62
• Figure 25. Overall and article-specific compliance with the UWWTD. 63
• Figure 26. Overall compliance with the UWWTD by country. 64
• Figure 27. Proportional representation of global household wastewater flows in 2022 through the stages of the conceptual framework. 65
• Figure 28. Estimated proportions of household wastewater safely treated by country (2022). 66
• Figure 29. Proportions of household wastewater collected, by collection type and SDG region. 66
• Figure 30. Comparison of data collected for the 2021 and 2024 reports. 70
• Figure 31. Number of countries with domestic wastewater estimates for which standard assumptions were employed, by data input variable and country type (sewer or septic tank dominant). 74
• Figure 32. Management instruments for pollution control. 77
• Figure 33. Volume of wastewater reuse reported in million m3/year 80
• Figure 34. Comparison of 2020 versus 2022 country estimates for household wastewater safely treated 95
• Figure 35. Notable time series for the proportion of household wastewater collected in urban wastewater collection systems and delivered to treatment. 97
• Figure 36. Notable time series for the proportion of household wastewater delivered from sewers to WWTPs and treated by secondary or higher processes. 98
• Boxes 9
• Box 1. Wastewater 2030: striving for a circular economy in a climate-resilient world 23
• Box 2. Monitoring of wastewater generated by services 34
• Box 3. Management of household greywater: Case study of the Swachh Bharat Mission in India 37
• Box 4. Safely managed sanitation services (SDG Indicator 6.2.1a) and safely treated wastewater (SDG Indicator 6.3.1, domestic component) 40
• Box 5. Demonstrative example of the development of a country estimate for the proportion of household wastewater safely treated 43
• Box 6. Taking stock of wastewater treatment capacity in Latin America and the Caribbean (LAC). 54
• Box 7. Industrial and urban wastewater flows as monitored by the Environmental Protection Agency (EPA) Ghana. 57
• Box 8. Czechia industrial wastewater monitoring 59
• Box 9. The European Union’s Urban Wastewater Treatment Directive: Progress, evolution, and future 63
• Box 10. Policy brief on setting the agenda for safe and sustainable wastewater management and monitoring in the context of the SDGs 69
• Tables 9
• Table 1. Summary of global wastewater monitoring data for SDG Indicator 6.3.1 comparing data between the 2024 and 2021 progress reports 16
• Table 2. List of variables covering the household wastewater conceptual framework for which WHO aims to compile reported data from countries 36
• Table 3. Monitoring of greywater management infrastructure established under SBM Phase II (and associated funding sources) 38
• Table 4. Comparison of wastewater statistics collected in 2021 and 2024 for the SDG 6.3.1 Indicator report. 71
• Table 5. Comparison of septic tank emptying assumptions and reported data 73
• Table 6. Description of the rationales for the most extreme cases of variability between the 2020 and 2022 country estimates 96
• Presenting the UN-Water Integrated Monitoring Initiative for SDG 6 118
• Learn more about progress towards SDG 6 120