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Letter Re: UV Light for Sterilizing Water
In my reading about water purification one of the things that I read about
was ultraviolet (UV)
light purification. I discarded it because I live at a fairly high northern
latitude (lower intensity light) and it is fairly cold here most of the year.
I just noticed something though. Sitting next to me
I have a "halogen gooseneck desk lamp" with a 20 Watt halogen JCD
bulb in it. While looking at the glass piece that sits between the light and
outside world I noticed that it says "UV Filter 001". This
got me to wondering how much UV light this bulb is throwing off, and if it
could be used for water purification (assuming power is present and water is down or contaminated). I wasn't able to find much info
on UV output of halogen bulbs, other then G.E. claims that their bulbs put
out very low amounts of UV.
Near the bottom of this page I did find a
nice set of tables talking about how much UV is needed to kill various micro-organisms.
- Ben
JWR Replies: To sterilize water, it is best to use a light
bulb that is optimized for transmitting the UV portion of the light
spectrum. As koi fish fanciers
discovered
a
decade ago, UV
light does a great job of sterilizing water.It actually does not kill all
the bacteria, but it renders them harmless by making them incapable of reproduction.
(Typically, folks
with koi ponds
use a water pump to circulate water in conjunction with a UV light that shines
on a clear plexiglas section of water pipe, gradually treating all of the
water in the
pond.
On
a smaller scale, the same technology is used with the SteriPen device made
for
backpackers.
(SteriPens are available
from SafeCastle, Ready Made
Resources, and many other Internet vendors.)
