[Philmont]: Water Purification and Iodine - Take 100

Another treatise from last year:

There have been some comments that Polar Pure will be withdrawn from the
market. It appears that the increasing regulatory hassles WRT iodine
may be too much for a small "niche" company to overcome. However, a
quick perusal of their website says nothing about it (yet). Others on
the List may have more definitive info.

There are dozens of authoritative sources on how to purify water in the
backcountry. Punch "water purification" into Google if you have a free
month or two. However, in the immortal - and accurate - words of John
Leblanc, there are a hundred ways to skin a cat, and whichever one you
pick, you will still pretty much end up with a skinned cat. But the
quality and speed of the job will differ based on the technique you chose.

It basically boils down to what exactly are you trying to conquer, and
how much time, money, and effort you are willing to put into it. You
have four basic problems - debris, bacteria, viruses, and pollution.
That order is also the order of difficulty in their removal or
neutralization - debris is (usually) trivial, bacteria tough, viruses
tougher still, and pollution (depending on what it is) from moderately
difficult to all but impossible.

You have various techniques, from stone age (boiling for ten minutes) to
space age (purifying filters, unusual chemicals, or this new MIOX gadget
that has been discussed at some length these past 10 days or so).

Boiling will kill nearly everything (excepting some really hardy viruses
that most of us will never encounter), and will even get rid of
pollutants with any appreciable vapor pressure. However, it does
nothing for debris or most pollutants, takes a ton of fuel and a ton of
time, requires a cooling off period to be able to drink, and usually
results in really flat (nasty) tasting water.

Oxidizing chemicals will (when used properly) kill most bacteria in a
reasonable amount of time. Some can kill viruses too, but can take a
looooooong time to do so. Some will react with certain types of
pollutants, and turn them into other types of pollutants - which may or
may not be an improvement on the original set (it's a crapshoot). They
do nothing for debris, many viruses, and most pollutants.

Filters easily remove debris, but clogging is problematic, and can be a
disastrous drawback in some settings (endless silty or muddy water).
Back-contamination can (and probably will) occur for the untrained or
foolishly careless - but at least can be corrected when it does occur,
as long as the fact that it *has* occurred is *recognized*. Filters do
nothing for most pollutant chemicals, but may be able to remove some
macromolecular pollutants. Depending on the filter quality (see next
paragraph), they can remove from most to all bacteria, and from some to
nearly all viruses.

As noted in the previous paragraph, probably the biggest issue is filter
quality. Think of screening as an analogy. A cheap filter is link
fence, a decent filter has chicken wire, a good filter has window
screen, and a great filter has ultrafine mosquito netting. Obviously,
the higher the quality, the better the filtration. Conversely, however,
the finer the mesh, the more difficult it is to force the water through
it, and the easier it will clog. This is not a perfect correlation,
however, because some filters compensate by having more filtering
surface. So a really top notch filter has a really fine mesh, and also
a large surface area. You may need to take out a small loan to buy it.
Clogging is (partially) alleviated by back-flushing procedures, but that
is also another potential area for screwing up.

Next up are Purifiers, which come in two types, which I will refer to as
"standard" and "absorbent" for lack of any better terms. A "standard"
purifier includes both a filter and some form of cartridge that contains
usually iodine (some other chemical may also be used, depending on the
brand and model). So it both filters the water, and chemically treats
it (the best of both systems). The same comments made above on filter
quality pertain to the filters in standard purifiers. So, a standard
purifier will remove debris, and either filter or chemically kill up to
nearly all bacteria and up to most viruses, but still doesn't do much
for pollutants other than what was noted above under chemicals and filters.

This is where an absorbent purifier comes in. These add yet a last
step, a charcoal or other absorbent based cartridge. These absorb most
pollutants, and so do the best job of all. I believe (but I'm not sure)
that the top-of-the-line purifiers have both a chemical cartridge and an
absorbent cartridge in addition to their filters.

There are even more advanced technologies (like UV-light or osmolality
based systems) that are so completely over the top that no-one on this
List will ever even hear of them, never mind use them. I ain't goin' there.

You will note that I have discussed the attributes and/or failings of no
brand names or models, nor will I. This field is changing (and
improving) rapidly, and what was state-of-the-art two years ago is
yesterday's news today. Two general statements can be made: First,
bring the system you need to suit the area where you'll be using it;
don't spend a fortune to appease paranoia. This is North America, not
Rwanda, Bolivia, or Cambodia. While there are some problem locales
here, most aren't that bad (if they were, we'd all be half-dead).
Second, like with most things, you get what you pay for. Fortunately,
in most areas of North America, even cheap is usually adequate.

Hope this puts things in perspective. I am sure that John L. and others
can expand on the finer points.

- Dr. Bob

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Received on Wed Apr 6 02:47:34 2005