Mar 25, 2013 at 12:47 pm #1300869
John DonewarBPL Member
@newtonLocale: Southeastern Texas
If UV light can purify water for drinking using a SteriPen for instance, could a clear water bottle achieve the same results?
I was watching a video review of the SteriPen Adventurer and had a…
…as the old Sun Tea idea came to mind.
What opinions or experience does anyone have on this idea?
NewtonMar 25, 2013 at 12:53 pm #1969421
As far as I know sun works too. Exposure time has to be considerably longer though and … well … the sun should actually be out. Pacific North West in winter is probably not working so well. Australian desert in the summer should work well ;)
Edit: Right, the bottles itself filter UV light. Hadn't thought of that.Mar 25, 2013 at 12:56 pm #1969422
By no means is this a definitive answer but my understanding is that short wave UV light cannot pass through glass and most plastics. The steripen lamp is made out of quartz for this very reason.
Smart people?Mar 25, 2013 at 1:02 pm #1969424
Most plastics block UV light. Very little UV would make it to the water. clean lake water is exposed to UV for days, yet experts still advise treating the water.Mar 25, 2013 at 1:14 pm #1969431
This method is approved by the World Health Organization for treating household water. Here's a link:
For the lazy, here's a link to some 30+ studies that confirm light filtering through clear bottles (like PET plastic) will disinfect water a significant amount over 6 hours: http://www.sodis.ch/methode/forschung/publikationen/index_EN#health
Edit: Here's some more info.
-Even extreme levels of fecal matter (100,000 E. Coli per 100ml) are rendered harmless by UV exposure using the SODIS method (Solar Disinfection).
-A bottle 3 liters or smaller must be placed on its side for 6 hours in direct sunlight to be rendered harmless.
-Only clear bottles will correctly allow UV radiation in.
-Some bacteria grows with sunlight, but this is harmless bacteria.Mar 25, 2013 at 1:38 pm #1969442
Hamish McHamishBPL Member
Max beat me to it. Google "SODIS". There are caveats. Due to required exposure time even in ideal environments I would consider SODIS an emergency/survival tactic. Not super useful for the typical BPL hiker but it could be a lifesaver if you're on an international trek near the equator and run into water treatment problems.Mar 25, 2013 at 1:40 pm #1969443
Another thread on this topic.
Reading through the link from above, it seems that 6ish hours are required. Probably not practical for backpacking but great for third world countries though. I previously understood that UVC was the requirement for sterilizing pathogens but there's obviously more to the story than that. Seems temperature plays into the SODIS process as well.
Interesting article nonetheless.
Edit: James covered this while I was typing.Mar 25, 2013 at 2:37 pm #1969462
It's okay, guys. You were up against a journalist ;)Mar 25, 2013 at 2:50 pm #1969466
Gracious personality and a journalist to boot! In my effort to become all that is man, would it be okay if I follow you around for a week and take notes?Mar 25, 2013 at 3:45 pm #1969479
Colin KrusorBPL Member
@ckrusorLocale: Northwest US
I went to a global health conference a while ago and attended a talk about SODIS implementation in Africa. A major obstacle to acceptance by people living in African villages is stigma and aesthetics. In areas where waterborne parasites cause high mortality among children, people who adopt the SODIS method for water disinfection are stigmatized and ridiculed by their neighbors. People consider them gullible for believing that the water is unsafe just because some health worker told them so. They also don't like the way the bottles look, lined up on the roof.
Anyway, I would have to agree with the other posters: it doesn't seem practical for backpacking except on perfectly clear days at high elevation or low latitude. And the bottle(s) need to be thin-walled PET (not thick-walled lexan Nalgene) and strapped on the pack in full sun (no part shaded).Mar 25, 2013 at 3:57 pm #1969482
Nathan WattsBPL Member
A steripen uses UV-C
Sunlight that penetrates the atmosphere is UV-A
Both are effective at treating your water.
Your bottle will block UV-C, which is why the Steripen is safe to use.
UV-A from the sun will penetrate the bottle, which is why you can treat water in a bottle with this method.
Hope I didn't cross up the letter designations too badlyMar 25, 2013 at 6:48 pm #1969549
Ian, I was just joking!Mar 25, 2013 at 7:00 pm #1969555
So was I :)Mar 25, 2013 at 7:41 pm #1969568
Jason ElsworthBPL Member
@jephotoLocale: New Zealand
Gracious personality and a journalist to boot! In my effort to become all that is man, would it be okay if I follow you around for a week and take notes?
LOL – someone had to say it.Mar 25, 2013 at 7:45 pm #1969570
Paul KellyBPL Member
boys let the light shine – it will cleanse all
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