Book 30, Question 116
Can a plastic bottle and sunshine clean water?
In some sunny places, families clean water with a method called SODIS.
They fill clear plastic bottles with clear water and set them in strong sun for about six hours. UV light and heat from the Sun work together to kill many germs. It works only for water that is not muddy, and it takes sun and patience. It's one low-cost way to make water safer.