I got this in a newsletter. Sounds like it should work. http://www.electricitybook.com/solar-water-purification/
It was found that by using only the PETE type plastic bottles, 2 liter and 3 liter soda types, and by painting them half black on the backsides only, they work much more effcicently. I did this and tried 2 different ways to enhance the sun uv energy... 1) I put 4 of these into a cardboard box, lined with aluminum foil, for maximum reflectivity into the bottles.... 2) I built a box of hardboard, and painted it flat black inside, and used just the clear plastic bottles.... By roughing up the backside of the plastic bottles with a 3m type pad, the paint adheres much better. The bottles being painted black on the backside, makes use of the uv to a greater percentage, and absorbs the uv better to treat the water. I decided to use plain old Phoenix (yuccky) tap water and treat it for 4 hours on one set and 8 hours on another set. The results were amazing. The chemical tastes (mostly chlorination) were removed somehow, and the water was quite warm. After refrigeration, the water was vastly superior to any bottled water I have ever tasted. I built a far more effcicent model, using hardboard, and mirror tiles! It really works! Bill
I cannot say whether it works or not, never tried it. However, before I relied on that method of "purification" I'd run a few test batches and send them off to get tested for bacterial contamination, both before and after treatment. Standard well testing protocols should do well enough. Little doubt in my mind that taste would be improved, but lots of doubt as to lack of infectiousness. Now, if there is a way to confirm that the temps were up to at least 168F for "a while" I'd be a lot less concerned. Bill, you need to run the same series of tests on water from a river or swamp (or taken directly from a sewer and filtered first, if you can stand the thought) not a city supply. The chlorine in the city supply killed the bacteria before you ran the test. Some things are too easy.
I came up with a technique for desalinating seawater in a portable assembly, especially for lifeboats etc. Good points Ghrit.
It isn't so long ago that lifeboats on warships were equipped with solar stills. They worked, but output was not generous. If I can find a link, I'll post it. IIRC, they were plastic and didn't last too long in storage. That's going back quite a way, plastics were not so advanced as today.
