- Where feasible, the efficacy of water treatment technologies offered to consumers is matched to specific contaminants present in their local water source.
- Turbidity may require reduction via settling/sedimentation or coagulation/flocculation in order to allow for other treatment options. For example, the following technologies have the corresponding requirements for influent turbidity values:
- Ultraviolet: influent <30 NTU (Laurent, 2005) for efficacy.
- Slow sand: influent ≤20 NTU (Davis, 2002) for efficacy.
- Ceramic: influent ≤20 NTU (Laurent, 2005) to mitigate clogging of filter element.
Notes and exceptions
- Emerging technologies and products may allow one device to be “customized” for specific contaminants.
- Turbidity and dissolved solids are key variables in source water and can determined the effectiveness and user satisfaction with HWTS products.
- Rainwater Harvesting Technical Brief. WaterAid, unpublished data, 2010.
- World Health Organization (WHO). Guidelines for drinking-water quality: Incorporating 1st and 2nd addenda, Vol.1, Recommendations, 3rd ed. Geneva: WHO; 2008. Available at: http://www.who.int/water_sanitation_health/dwq/fulltext.pdf.
- PATH HWTS Tradeoff Matrix. HaloSource, unpublished data, 2009.
- Full list of supporting evidence and additional materials.
The device should be appropriate for treating water from the local water source. Photo: PATH.