Water - SODIS

In 2010 National Geographic Magazine created a special edition entitled Water Our Thirsty World.  I was reading in this morning and stumbled across an article about SODIS "Solar Water Disinfection".  It's an interesting concept that I hadn't heard of and so I thought I'd share it here in case someone else might be interested.

 Picture from Loughborough University  where they have even more interesting  information  on the subject of water.

The concept is simple you take a clear PET plastic water bottle remove the label and lay in on a piece of metal in the sun, 6 hours later you have disinfected water. 

According to a SODIS website the UV-A rays in sunlight kill germs such as viruses, bacteria and parasites (giardia and cryptosporidia).

This method has been recommended by the World Health Organisation (WHO), UNICEF, and the Red Cross.

For more information on how it works please see
SODIS:  How does it work?

Things to consider:
1. Size and shape of the bottle  (wash it out with soap first)

•  clear or light blue
• not too scratched
• not more than 3 liters

2.  Turbidity (how cloudy the water is)

• You should be able to read a newspaper headline through the bottle, if not the water needs to be filtered.

3. Weather

• Cloudiness
• If less than half of the sky is clouded over, 6 hours will be enough to completely disinfect the water.
• If more than half of the sky is covered with clouds, the bottle must be placed in the sun for 2 consecutive days.
• Rain -
• not effective during lengthy periods of rain, but on day like this you could collect rain water

4.  Re- contamination

• drink directly from the bottle or right after pouring it into a cup