h a l f b a k e r y
Not just a think tank. An entire army of think.
add, search, annotate, link, view, overview, recent, by name, random
news, help, about, links, report a problem
or get an account
The biggest problem with pools is pool water. It smells like chlorine, feels like chlorine, and burns your eyes. Systems exist that purify the water using UV light, similar to a backpacking UV purifier. Why limit ourselves to a small UV unit that only partly purifies the water though?
bottom of the pool with large UV lights like the ones used in tanning beds. That way, the pool will be completely purified and the swimmers will get a nice, even tan at the same time. Swim goggles with UV protection required.
In the interest of safety the lights will only turn on for ~10 minutes every hour (or whatever is safe, I have no idea) and they can be set to turn on and off on a schedule to keep the pool clean when it isn't in use.
Vastly improved over last year's Gamma ray pool.
Water absorption spectrum
Second-to-last graph [spidermother, Jun 12 2013]
||After listening to the microbiologists at work, I no
longer trust UV in any sort of sterility applications.
Of course it's possible they may be making me a bit
paranoid on the subject, although I haven't seen any
||If anybody needs me, I'll be ETO sterilizing the cat.
||More practically, I'm pretty sure that sufficient UV
radiation to penetrate the full depth of the pool
would be severely dangerous (possibly lethal to
divers) to anyone who
happened to be swimming to close to the source.
For a six foot deep pool, you're looking at (as near
as I can tell) about two orders of magnitude
reduction from top to bottom. As a very rough
estimate, you would end up with something very
close to 8x the full intensity of the sun, except
purely in very nasty UV (UV-C) right near the
||If you've got a diving end, it works out to
something more like 800x.
||(Any can correct my numbers. This is based on a
disinfection dose of 8000 micro watts/cm^2, an
attenuation of .01/cm, and a full sunlight
intensity of 1W/cm^2)
||It works for water treatment because they use
relatively shallow pools, very intense lights, and
don't put humans anywhere near it when the
lights are on.
||The light doesn't have to penetrate the full depth of
the pool - it just needs to gradually sterilize water
as it passes near the lights. Convection and
pumping (for filtration) will cause adequate
||That said, I suspect that the best wavelengths for
sterilization are shorter than the best wavelengths
for safe tanning.
||The nasty sterilising wavelengths are very strongly absorbed by water (link), and very bad for you.
||The really nasty ones are, but they aren't generally
used because of the ozone production, which is bad
to have anywhere humans are working. I think the
ones that are generally actually used are in the
~250nm range, and aren't quite as strongly absorbed.