In Africa where clean water is scarce, people drink from ditch watrer and many people die.
Warter bottles are public enemy #1 in green countries 
, but in Africa they are "new technology" 
. People in Afrifca they fill water bottles in ditch water, leave under the sun for hours. It's a solar treatment. Sickness dropped by some 70%. Western scientists did experiment and confirmed that in 4 1/2 hrs, most germs are killed. It destroys membrane and protein of necessary for germs reproduction. It's a SteriPen effect for free although takes longer.If you forget to bring water treatment system (and stove?), and can wait 4 1/2 hrs, this can be handy.
