Source
https://www.who.int/publications/i/item/9789241512770 — original source (opens in a new tab; the file is not redistributed)
Context: both · Feeds D03 (greywater routing; potable-reuse feasibility)
Summary
WHO’s Potable Reuse guidance sets out why producing drinking-quality water from wastewater requires a complex, multiple-barrier treatment system rather than the simple point-of-entry filtration + UV suitable for clean source waters. It is the authoritative basis for the water-domain redesign’s decision to route greywater to non-potable uses only (toilet, laundry, irrigation), since a household-scale train cannot meet the pathogen-reduction targets wastewater demands.
Key claims
- claim: "Potable reuse of wastewater requires MULTIPLE treatment barriers, not simple treatment: 'potable reuse schemes require multiple treatment barriers to ensure safety'; typically 'advanced treatment processes such as membrane filtration, advanced oxidation and activated carbon follow a biological wastewater treatment process such as activated sludge or membrane bioreactor (MBR)'. [verified verbatim]"
source_location: "Ch.2 §2.5.1 (p.15) and p.16 (treatment-train description)."
- claim: "Because 'Wastewater contains high concentrations of enteric pathogens', production of microbially safe drinking-water requires high performance targets - default minimum 8.5-log reduction of enteric bacteria, 9.5-log reduction of enteric viruses and 8.5-log reduction of enteric protozoa. [verified verbatim]"
source_location: "Executive summary / Ch.5 microbial performance targets and Conclusions (p.61); default targets, Appendix 1."Model use
- Anchors RT_409a. Justifies the redesign’s rule that domestic greywater is non-potable and routed to toilet/laundry/irrigation only, never credited against drinking water. The point-of-entry UV + 5-micron cartridge train the model already carries (URL_041, URL_042) is scoped to low-turbidity clean source waters and delivers nothing close to the 8.5-9.5-log targets wastewater needs.
- NZ statutory anchors already held: BRANZ greywater bulletin OT_040 (greywater is non-potable, subsurface discharge). Together these mean greywater offsets non-potable demand only.
- Thesis: bounds the water self-sufficiency claim - full on-site potable closed-loop is municipal-scale and out of reach for a small community, so self-sufficiency is achieved by matching quality to use, not by recycling everything to drinking standard.
Research targets
No new research targets. Anchors RT_409a (greywater not cheaply treatable to potable at household/community scale).
Connections
Links to
Sources (3): OT_040 · URL_041 · URL_042
EDT domains (1): D03: Water, Waste & Circular Systems
Referenced by