UV-Tube for Disinfecting Water
by Justin Thomas, Virginia on 09.12.05
This UV-Tube has been getting some press in the wake of hurricane Katrina. It is a low-cost water disinfecting system, which basically consists of a plastic tube and an ultraviolet light bulb, which can be run on solar power. It processes about five liters of water per minute. Ultraviolet light has been used to disinfect water for quite a while now. The inventors say the UV-Tube differs from other systems because it is inexpensive and less energy intensive.
"If you run the system throughout the day, you can get drinking water for hundreds of people," said graduate student Micah Lang at the University of California, Berkeley's Renewable and Appropriate Energy Laboratory. The team recently conducted a round of field tests with a solar-powered version of the tube in a tsunami-ravaged village in Sri Lanka and in rural villages in Baja California. The tests have gone quite well, Lang and Kammen said. "It is a great way to kill most of the pathogens in decaying fecal matter," said Kammen.
:: News.Com
There are patents on using UV irradiation to better sterilize potable water with less of the chemical additives such as ozone or chlorine. What I recall is that irradiation only works well if particulate matter is low and flow rates stay in a narrow range. The light won't penetrate a chunk of turd or a bit of fish eye flowing slowly by the bulbs in other words. Simple is nice but so is common sense.
Assumably the water would have to be at least coarsely filtered to fit down the the little funnel at the end(in the photograph) so large turds, fish eyes and other particulates might not go in to begin with :)
Maybe they can rig up some solar stills or something that is not dependent on power to clean the water. Whatever the solution, cleanup of the water in the Gulf Coast is a long way coming...
Combine the UV filter with this:
http://www.treehugger.com/files/2005/08/cermaic_filters.php
And I bet the water you get is hard to beat.
I like the idea, but what type of plastic is used? What about leaching and the uv breaking down the plastic? Maybe used in emergency situations the effect is minimal...
UV has been used as a supplementary treatment around the US, but as mr. laumer stated, it has limitations. an additional one being that UV has no residual like chlorine does, that would prevent the water from becoming infected again.
How about putting water in a clear container and leaving it in the sun. Same effect? With the added benefit of particulates settling to the bottom? Not quite as fast, and not for really nasty water, but good in a pinch.
OR, if you're using what's on hand, how about coffee filters in the funnel? :)
OR, if you're using what's on hand, how about coffee filters in the funnel? :)
This doesn't really help in NOLA, though, since there are chemical toxins in the water, not just biological ones.
No, a glear glass bottle wouldn't work, as glass reflects much of the UV, and the intensity would be too low.
Solar stills won't remove all cysts or bacteria
This will work quite well if the water is filtered through coffee filters, as mentioned by Eric, or clean cloth to remove particulates.
I would rather see it built out of glass, steel, or copper, to avoid carcinogens and xenoestrogens from the plastic contaminating the water.
The UV Tube has a layer of stainless steel in the inside of the PVC pipe to avoid degradation and toxics delivered into water.
I recommend to check the UV Tube website:
http://ist-socrates.berkeley.edu/~rael/uvtube/uvtubeproject.htm
i am studying engineering at university in glasgow. as part of a project we are to desgn a water purifier for third world countries. currently i am researching pipe diameters/materials and for a flow rate of 0.6 litres/sec. any information which could be provided on this would be much appreciated. Also how long does the water have to be exposed to the UV for bacteria to be killed?