[philmont] Micro Pur Contact Time

The answer will be found at:

http://www.ahappycamper.com/products/water_purifiers/pur/micropur.html

>From that page they suggest different contact times are necessary for
different
contaminants.

 *Bacteria = *15 Minutes of Contact Time
*Virus = *15 Minutes of Contact Time
*Cysts = *30 Minutes to 4 Hours of Contact Time

A general article on water purification will be found at:

http://en.wikipedia.org/wiki/Water_purification

and an article on backpacking methods of water purification will be found
at:

http://www.princeton.edu/~oa/manual/water.shtml

Protozoans form cysts in water. ( examples: *Giardia lamblia* and *
Cryptosporidium*, both of which are pathogenic).

One issue is the temperature at which the treatment takes place. From
http://www.princeton.edu/~oa/manual/water.shtml:

 The colder the water, the less effective the chemical is as a purifying
agent. Research has shown that at 50° F (10° C), only 90 percent of *Giardia
* cysts were inactivated after 30 minutes of exposure. If the water
temperature is below 40° F (4° C), double the treatment time before
drinking. It is best if water is at least 60° F (16° C) before treating. You
can place the water in the sun to warm it before treating.

>From http://www.high-altitude-medicine.com/water.html

Killing effectiveness of the chemical is dependant on concentration of the
chemical, temperature of the water, and contact time. Decreased
concentration (better flavor) or decreased temperature (inevitably the case
in the mountains) requires a longer contact time for disinfection.

So the longer treatment time is necessary to destroy thoroughly the cysts.

Joe Jansen
JAJansenJr@gmail.com

On 1/30/07, JC Lewis <jc.lewis@tx.rr.com> wrote:
>
> Okay, everyone. What's the real deal about contact time for the Micro
> Pur water purification tablets after they've done their Alka Seltzer
> imitation and dissolved? The flyer in the package says 4 hours; and I know
> they didn't write that to satisfy their legal staff (at least, I hope not).
> However, that really seems to be way too long and totally impractical in the
> wilderness.
>
>
>
> A few years ago, soon after MSR put the product into the non-military
> market, I was taught to use them by some very experienced adult hikers who
> said the usual 20-30 minutes was fine, depending on how cold the water was.
> So, that's what I did. Our Ranger in 2006, said an hour is what they were
> taught in Ranger training, but also thought 30 minutes was probably enough
> in a pinch. I don't know ANYONE, in Scouting or out, who holds to the 4
> hours requested by the manufacturer.
>
>
>
> Given the particular chemical being used, sodium chloride, I think, is
> there a chemist or water purification expert amongst us out there who knows
> if less than 4 hours for these things is okay, and, if so, why? If the 4
> hours is gospel, why?
>
>
>
> (FYI for the lurkers and first-time Advisors: Micro Pur by MSR is the
> only water treatment method Philmont issues. They don't use the iodine
> Polar Pure bottles any more. You don't have to use the Micro Pur so long as
> you know to treat the water somehow. Some crews bring just filters, like
> the Katadyn Hiker, and don't chemical-ize at all. Many crews, however, do a
> combination of the two methods.)
>
>
>
> Jerry Lewis
>
> 2007 611-I-2
>
> Troop 303, McKinney TX
>
>
>
>
>
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Received on Tue Jan 30 00:00:24 2007