Quote:
Originally Posted by Turtle
|
I think that info should give an idea if whether your
Ultra
Violet
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/cm
2 for UV-A.
Needing 22,000 µW/cm
2 and having (on the low end) 500 µW/cm
2, 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.
In thinking about whether the above numbers could be correct I'm reminded that my UV light keeping my pond clear of algae is 9 watts and I figure the surface area it illuminates is about 315 cm
2 which comes out to 38,100 µW/cm
2 which isn't much higher than the 22,000 that the magnifying glass with a diameter of 3 inches would achieve. And my UV light is very good at killing algae and water moves through the light very quickly.
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/cm
2. It would be discouraging if the intensity needed to be that high, but this is encouraging:
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
