Puri tab questions

[Quixoticgeek]

Given that in theory we're expecting a winter soon. I'm about to put my Sawyer mini away and switch to puri tabs for water treatment. NaDCC tablets seem to be the tablets of choice, with Oasis being popular. I've got some 17mg Oasis NaDCC tablets which I got purely as they seem to be the ones the MOD give the squaddies. But I notice that the Oasis website recommends 5ppm as the ideal concentration, which for 1L of water is provided by their 8.5mg tablets. Which leads me to the question: why does everyone use the 17mg tablets over the 8.5mg?

The follow up question is does anyone know the timings for using NaDCC tablets at different temperatures? How long do I leave one at 5°C? What about 2°C or 10°C?

Cheers

J

 

[mick91]

Chlorine dioxide tablets like that are a really effective water purifier, 8mg tablets in 1 liter of water will handle most pathogens you're going to realistically come across. To a degree in our situation 17mg are overkill they're intended for heavily polluted water (ie raw sewage) and are in a way a case of what kills what deader.
On temperature you have to realise that all chemical reactions rely on activation energy, including the reactions that take place to kill bacteria (i know inhibition doesn't but let's not complicate it) so the more heat you have in the reaction the more energy you have. I'm not sure on actual times, but I normally leave mine around half an hour. Chlorine dioxide itself is fairly serious stuff, it's a powerful oxidizer, an explosive gas and wildly toxic. To give you an idea how toxic there's some numbers.
LD50 (Median dose)
292 mg/kg (oral, rat)
LCLo (Lowest published)
260 ppm (rat, 2 hr)
PEL (Permissible)
TWA 0.1 ppm (0.3 mg/m3)
REL (Recommended)
TWA 0.1 ppm (0.3 mg/m3) ST 0.3 ppm (0.9 mg/m3)
IDLH (Immediate danger)
5 ppm

5ppm is seen as an immediate danger even in something as large as a human, so microbes don't fare well in it. Mostly higher doses are to make you more confident not an actual functional issue. I use oasis all the time and have been fine so far

 

[Quixoticgeek]

Cheers, lots of interesting info there. Gives me something to think about.

J

 

[TarHeelBrit]

Thanks to the OP for asking this I was about to ask a similar question. As my Aqua Mira drops are almost gone and I was thinking of going the tablet route.