Household water treatment technologies
Which household water treatment technologies have been officially approved by GWC, WHO, UNICEF and UNHCR? Is there any other study than "WHO International Scheme to Evaluate Household Water Treatment Technologies" which is still under review?
Which water disinfectant can be used for long term use at household level with proved efficiency and without any health effect in the context of cholera ? (Chloramine T vs. Sodium hypochlorite vs. Calcium hypochlorite vs. Filters)
3 Answers
sodium hypocholrite in range of 0.2 -0.8 ppm is the most effective and safe water disinfectant .
I will let others point to specific approvals, but in the context of cholera (which kills c100,000 people every year) the adverse health effects of chloramine, sodium hypochlorite & calcium hypochlorite are negligible.
When used correctly, I am unaware of any adverse short term health effects. Long term, if there are problems with the source water, combined with over-dosing, disinfection byproducts may slightly increase the chances of contracting cancer. Compare the threat of death tomorrow by diarrhoea, vs a slight increased chance of death in 40 years time by cancer...
'Filters' is a very broad category. Many membrane filters (tight microfiltration filters, ultrafiltration, nano filtration) will exclude cholera (although microfiltration would still allow viruses to pass), and other filtration methods may reduce probability of cholera passing (more so following coagulation).
However, there is a risk that the water becomes infected after filtration - particularly in the context of a cholera outbreak. As such it would be prudent to maintain a disinfectant residual (an ongoing concentration of chlorine-based disinfectant) even following household filtration.
HHWT technologies may work in the lab (and hence testing is a vital step) but the big issue is sustainable operation. The socio-economic aspect is just (more?) as important. The literature now seems to advise focusing on smaller groups of people to ensure a higher level of use. Involve them in the selection of the technology.
Consider community treatment (e.g. bucket chlorination) rather than household if you are concerned about cholera.
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