Today's question: I’ve heard that some countries use solar rays to disinfect their drinking water. Is that true?

Plain Talk answer: Solar disinfection has proved useful in developing countries, where access to safe water is limited. Solar disinfection relies solely on the heat and ultraviolet radiation of the sun to make water stored in transparent containers drinkable.

The practice is used at the household level under the responsibility of the user, and its success rate depends on numerous factors, including the intensity of sunlight, geographic location, cloud cover, time of day, type of bacteria being exposed, containers in which the contaminated water is kept during exposure and clarity and depth of the water.

For more information on this and many other water-related topics, check out Plain Talk About Drinking Water by Dr. James M. Symons.