Microbiological efficacy

• The efficacy of durable and consumable HWTS products should demonstrate statistically significant reductions in microbiological contaminants over the life of the product.

Key indicators

• Threshold for multistage device at end of life:
• Bacterial efficacy: 3 log reduction value (LRV).
• Viral efficacy: 3 LRV.
• Cyst reduction: 2 LRV.
• Most desirable for multi-stage device:
  • Bacterial efficacy: 6 LRV.
  • Viral efficacy: 4 LRV.
  • Cyst reduction: 3 LRV.

Notes and exceptions

• There is a need for more health impact studies correlated to specific products or technologies.
• Single-stage treatment methods may not meet a wide breadth of microbiological efficacy; however, the merit of the treatment should be assessed against available health impact studies.

Supporting evidence

• 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.
• Drinking Water Contaminants Maximum Contaminant Levels (MCLs) page. United States Environmental Protection Agency website. Available at: http://www.epa.gov/safewater/contaminants/index.html. Accessed April 1, 2011.
  
• The Sphere Project. The Sphere Project: Humanitarian Charter and Minimum Standards in Disaster Relief. Oxford, UK: Oxfam Publishing; 2004. Available at: http://www.sphereproject.org/content/view/27/84/lang,english/.
  
• Indian Standard for Drinking Water per Bureau of Indian Standards (BIS) (IS 10500:1991).
• Published health impact studies by various academic professionals (e.g., Mark Sobsey, Joe Brown, Christine Stauber, Robert Quick, Tom Clasen, Danielle Lantagne, T.M. Joyce).
• Full list of supporting evidence and additional materials.