>>564090It actually doesn't kill most of them, it renders them "inactive" (basically sterile) so they can't reproduce if you ingest them.
UV radiation is actually very damaging to nucleic acids. Larger organisms are protected by things like skin or bark, but since most microorganisms are basically just little DNA blobs they take the full brunt of it if exposed to UV rays.
Make sure that the water is free of particulate matter and/or that there's no label or printing on the bottle that might cause a shadow where bugs can hide.
You can also speed up the process by making a tinfoil or mylar reflector to set the bottle on. Of course, even then it's still a slow process so it's more of an emergency/survival method of doing things.
BTW I'm not a scientist or biologist, but I'm an avid backpacker and worked as an /out/fitter for a number of years so I had to learn how all the different filtration/purification methods worked as well as alternative/emergency methods.
