Adam Weiss wrote in news: snipped-for-privacy@blockspam.org:
You're talking, in essence, about a simple distillation apparatus. Bacteria, parasites, and algae should be too large to be lifted by water vapor - if your plastic is hanging over an enclosed space with no or very little air movement, they should not be aerosolized.
I'm not sure about viruses. Polio virus can, if I remember correctly, survive in water but I don't know whether viruses could be lifted by water vapor. OTOH, I'd thought that distillation demineralizes water, and given the size of molecules, it also therefore ought to "de-virus" it as well.
Assuming that your plastic aheet and your collection vessel are clean, you ought to be OK.