Science Forums 2

[Turtle]

Originally Posted by modest

I think that info should give an idea if whether your UltraViolet Portable Absorption Sterilizing System (UV-PASS ) should work.

According to the chart you link, bacteria need between 3620 and 22000 microwatts per centimeter squared of UV to be sterilized. The only convincing source I could find on the amount of UV the earth's surface receives is this page. It gives between approx. 400 and 1800 µW/cm² for UV-A.

Needing 22,000 µW/cm² and having (on the low end) 500 µW/cm², you would need the surface of the magnifying glass to be (22000 / 500) 44 times larger than the surface of the target. That's not that bad really. If the target is one square centimeter then that's only a magnifying glass with a radius of (sqrt(44/pi)) 3.74 centimeters which is a diameter of about 3 inches.

That sounds very doable. The only thing I would worry about is how much UV the magnifying glass and the glass tube absorb. If it is something like 50 percent each then you'd have to make the area of the magnifying glass 4 times larger.

roger all that, and nice acronym. your source below says

pure-fused Quartz which has a transmission rate of approximately 98 percent.

my hand lens is plastic and i couldn't find much on its transmissibility of UV, but i found a lot on how damaging UV is to plastic. so, if we have ourselves a pure-fused quartz lens & tube, i still have questions/doubts whether the lens will bend the UV to the focus or if it will simply pass straight through??

Originally Posted by M-Man

I would wonder about parasites though. According to your chart protozoa require quite a bit more UV to kill. Are water-borne parasites protozoa? I wonder if that's the kind of thing the chart is referring to between 26,400 and 318,000 µW/cm². It would be discouraging if the intensity needed to be that high, but this is encouraging:

not sure on the protazoa/parasite business. will have a look.

Originally Posted by Modestino

The United States Department of Health has determined that a UV system should provide a minimum of 16,000 Microwatts per Centimeter Square.

Information on portable water purification and portable water systems

~modest

since they don't mention parasites/protazoa there as far as their UV sterilization systems, and they do have a pretreating filter in front of the UV treatment in those systems, maybe they filter out the parasites/protazoa? more sleuthing.