I saw a charity that, I think, had people put 16.9 oz (.5 liter) water containers out in the sun on posts, then said it was safe to drink the water. I do not remember, but I think it took awhile, many hours.
I think it is warmth and possibly UV light that cause the sterilization effect. I think these could be increased strongly with a cheap 1-2 cent sticker applied to many containers even 1 or 2 liter containers.
The transparent sticker would be IR absorbing, and have little lensed bumps on it (or possibly a nonbumpy diffraction grating) to concentrate UV. When you think of a bump, or a diffractor, with an area 100 times the size of the focal point then that eentsy point gets 100 times more sterilizing radiation. So if UV previously did nt matter, it could contribute to water sterilization that way
The main improvement to affixing a sticker to a container and then tossing it haphazardly out into the yard is that you get to skip the process of installing dozens of tidy little semireflective posts in your yard, and can instead just fling things around haphazardly and still get drinkable water.
If the IR absorption of a container of water on a tidy reflectorized post is 20%, and that of a UV transparent IR absorbing sticker 99% then the sticker can be five times smaller than the container and get the same results, which makes it cheaper and easier to stick on. Alternatively it might mean that you can sterilize a larger 1 or 2 liter soda container at a highly similar surface area, which gives a person much more water per refill.
at 1-2 cents per sticker that would cover 1 billion containers for $10-20 million $ and prevent a lot of water based illness-- beanangel, Nov 19 2019 // sunlight //
Since some halfbakers reside in Caledonianshire and other northward areas, they might appreciate an explanation of what "sunlight" is.
Many of them have red hair and very pale skin, the result of a genetic variation which affects the production of melanin, a pigment that protects against damage by UV. Given the general lack of solar radiation of any sort, combined with a predisposition to the adoption of a troglodytic lifestyle, it's not surprising that the gene has become superfluous.
Either that, or it's dissolved away in a corrosive deluge of Buckie, Carlsberg Special Brew, and rubbing alcohol.-- 8th of 7, Nov 19 2019 I may have seen, but misinterpreted, a youtube video that said half of all illnesses are from water-- beanangel, Nov 19 2019 Terribly dangerous stuff, water .. have you seen what it does to steel nails ?-- 8th of 7, Nov 19 2019 //I think it is warmth and possibly UV light// It's probably the UV.-- MaxwellBuchanan, Nov 19 2019 So, what about a parabolic "solar cooker" that focusses the UV but disperses the visible and IR ? The water stays cool, but is bug free.
Then again, boiling does a good-ish job against many pathogens ...-- 8th of 7, Nov 19 2019 random, halfbakery