Solar water disinfection (SODIS) involves exposing water-filled plastic polyethylene terephthalate (PET) bottles to sunlight for several hours. Exposure times vary depending on weather and climate from a minimum of six hours to two days during fully overcast conditions. It is recommended by the World Health Organization as <answer>a viable method for household water treatment and safe storage</answer>. Over two million people in developing countries use this method for their daily drinking water.
What does the World Health Organization say about Solar water disinfection?
a viable method for household water treatment and safe storage