WHO International Scheme to Evaluate Household Water Treatment Technologies
Based on World Health Organization (WHO) global household water treatment (HWT) microbiological performance recommendations, a WHO International Scheme to Evaluate Household Water Treatment Technologies (“Scheme”) has been established.
- Promote and coordinate independent and consistent testing and evaluation of HWT products based on WHO recommended criteria to determine their level of performance in removing pathogens, and in so doing, guide WHO Member States and procuring UN Agencies in the selection of HWT;
- Support national governments in building the technical capacity of research and laboratory institutions for conducting complimentary assessments of HWT and, in general, applying WHO Guidelines on Drinking-water Quality recommendations at the national level.
Basis for a household water treatment evaluation scheme
There are a number of different HWT methods that aim to reduce microbial pathogens. The main types of HWT methods include:
- physical removal of pathogens (e.g. filtration, adsorption, or sedimentation);
- chemically treating water to kill or deactivate pathogens, most commonly with chlorine;
- disinfection by heat (e.g. boiling or pasteurization) and ultraviolet (UV) radiation, either using the sun (solar disinfection) or an artificial UV lamp; and
- combination of these approaches (e.g. filtration or flocculation combined with disinfection).
These different treatment methods vary in their ability to remove the main classes of enteric pathogens that pose health risks (bacteria, protozoa and viruses) and, even within each of these treatment categories, performance among different specific technologies varies considerably.
In order to assist Member States in the evaluation and selection of HWT, WHO published the aforementioned global recommendations, detailing criteria and guiding principles for evaluating and assessing the performance of HWT. These recommendations provide the basis for evaluating and classifying HWT into three levels of performance: 3-star (***); 2-star (**); and 1-star (*), based on their ability to remove pathogens.
However, many Member States have neither the capacity, nor the resources to evaluate technologies based on WHO’s recommendations. Concurrently, the governments of these same Member States, mainly located in sub-Saharan Africa, Southeast Asia and parts of Central and South America, are increasingly being approached by both local and international manufacturers to buy and/or allow the sale of their product within the respective countries. Therefore, WHO has established an international evaluation scheme for HWT to fill the immediate and growing need for rigorous health-based assessments of HWT technologies.
The HWT products that are found by WHO to meet the WHO recommended performance criteria will be included in a list published on the WHO website. Products on the list will be classified into three tiers: 3-star (***); 2-star (**); and 1-star (*), based on their ability to remove viruses, bacteria and protozoa. The list is principally intended to assist WHO Member States and UN agencies in the procurement of HWT.