[DIYbio] Re: UV LED for disinfection of water

UVC disinfection for water sterilization has been around for quite a while. In fact, you can buy anything from industrial-scale UV water sterilizers, all the way down to portable "Steripens" for backpackers.

As you discovered, one issue is how low efficiency the UVC bulbs are, which means you pay a lot in electricity cost, and you have to dissipate a lot of heat. Another important limitation is that you need to expose the bacteria to a sufficiently high dose over time to be effective. So it's much easier to expose a bottle of drinking water to constant UV light for a minute, like the Steripen does, than to slap a big LED on the side of your water mains and expect it to be effective.

If you are going to tinker with mercury vapor lamps yourself, BE VERY CAREFUL! Shortwave UVC light is as good as absent from natural sunlight, and can burn out your retinas in a matter of seconds - especially if you work with a strong point source like the 125W bulb in the link that you posted! 

(For the same reason, NEVER work at a biosafety cabinet with the sash raised while the UVC germicidal light is on! The glass sash will block most of the UVC, but you can still get a bad sunburn on your arms, or develop the equivalent of snow blindness from the UVC reflected off the stainless surfaces.)