Returning to the Well
A Second Look at Water Treatment Options
Part 2—The State of the Mart
By Farwell Forrest
farwell@paddling.net
August 13, 2002
Need a drink? You're not alone, apparently.
Tamia's piece on
the perils of drinking "found" water provoked more comment
than any other recent column. Last week I addressed concerns voiced by a
reader in the "Wait
Just a Second!" camp. This week, it's time to hear from the "Yes,
But…" division. So here goes.
Kirk writes:
I read your water filtering article and though good you
miss a lot by not talking about the newer purifications systems out
there…. You mention filters, but purifiers are VERY different from
simple filters…. Purifiers must meet EPA regulations to even be
advertised as being a purifier and most nowadays exceed EPA regulations.
Some of these purifiers are the ones like you mentioned in the later part
of your article about an iodine impregnated solution, while others like
the SweetWater® purification system use a chlorine-based solution in
a little bottle after the water has been filtered, so people with iodine
problems can use the latter…. [There are even] newfangled ones that
use UV light to purify water….
Most backpackers I know have shifted away from using iodine pills as
their primary method to clean water and moved to a purifier…. They
simply taste better, are faster to produce clean water and actually remove
particulate matter from the water. No offense intended, but I think you
are doing your readers a bit of a disservice by not covered this topic in
more depth and laying out all the options available to them.
Fair enough, and no offense taken. Tamia's original article wasn't
intended as a marketplace survey, but Kirk raises several important
points, nonetheless. I won't attempt a definitive examination of all
available options—my own experience with portable water-treatment
systems is limited to chemical germicides and first-generation
microfilters, and I've never felt the need for anything more—but I
will take a closer look at the state of the mart. Since I don't
have an analytical lab at my disposal, I'll have to rely mostly on
manufacturers' claims and whatever documentation is available on-line.
Still, I think the exercise will be worthwhile. If nothing else, I'll have
an excuse to bring my slide-rule out of retirement. (For those born in the
last quarter-century, a slide-rule is a primitive, pre-electronic
calculating device. It won't give you ten-place accuracy, but at least it
doesn't need batteries—and there's no better tool for solving
proportions.)
First, though, let's take a look at EPA certification and its
limitations. The test protocol used in evaluating water purifiers is laid
out in the "Pesticide Program Guide Standard and Protocol for
Microbiological Water Purifiers" (Federal Register, Vol. 51, No.
133, Thursday, May 26, 1987). The EPA does not consider most
microfilters to be "purifiers." Microfilters do not, therefore, require
registration under the provisions of the Federal Insecticide, Fungicide,
and Rodenticide Act (FIFRA). As Kirk notes, however, a filter can become a
purifier with the addition of any system intended to deliver a chemical
germicide. Such devices must then be registered.
The EPA protocol appears to be well thought out, but it has two
apparent deficiencies: (1) the pH (a measure of acidity) of test water
samples is permitted to be neutral or even slightly acidic, and (2) viral
challenges are limited to strains of poliovirus and simian rotavirus.
Why is this important? To begin with, certain chemical germicides
suffer a marked loss of efficacy in alkaline water. (This is true of
chlorine-releasing compounds, for example.) A certification protocol which
does not ensure that water samples reflect a representative range of
pHs—both acid and alkaline—may therefore not adequately test all
germicides.
The limitation on viral challenges also poses difficulties. The
restrictions are, of course, understandable. Viruses are difficult to
culture, and many strains pose obvious risks to investigators. Still,
viruses are extraordinarily diverse, and relying on only two viruses as
proxies for the entire spectrum of viral pathogens makes the certification
process more-or-less conditional. So EPA registration, even though a
requirement of law and a valuable indication of a purifier's relative
efficacy under test conditions, cannot be taken as an iron-clad
guarantee that the same purifier will always perform satisfactorily in the
field. The world outside the laboratory is a messy and complicated place,
after all.
These cautionary comments aside—as always, "When in doubt, doubt"
remains the only certain rule—let's take a look at a representative
sample of what the water-treatment marketplace has to offer.
THE "OLD RELIABLES"
Balancing cost, fussiness, and efficacy, most paddlers will find only
one germicide worth considering: iodine. While elemental iodine can be
used to disinfect water—the so-called Kahn-Visscher
method—tetraglycine hydroperiodide (TGHPI) "emergency drinking
water purification tablets" are much more convenient. Potable Aqua®
and Coghlan's are two widely-distributed brands.
When used according to package directions, fresh TGHPI tablets will
reduce the numbers of bacteria, viruses, and some protozoan
pathogens to acceptable levels even in "grossly polluted water." The
treatment protocol is simple and easy: just add one tablet to each quart
of clear water, shake, and then wait ten minutes before drinking. (Double
the dose or contact time if the water is turbid—cloudy—or cold.)
Cost is moderately high: around US$0.40 a US gallon, though at least the
up-front investment is limited to the price of a bottle of tablets (about
US$5.00). The cost can be further reduced by employing a "low-dose" regime
of the sort that Tamia and I use, but it must always be remembered that
this practice invariably impairs antimicrobial efficacy. Prudent
paddlers will follow the label directions exactly.
Cautions are few but important. People with thyroid disease or iodine
allergy should not use TGHPI tablets. Moreover, TGHPI probably cannot be
relied upon to kill Cryptosporidium parvum, a common protozoan
parasite. Individuals whose immune systems aren't up to par should
therefore look for another treatment method. TGHPI tablets also lose
potency with time. They should be kept in a tightly-capped glass bottle,
and any unused tablets should be discarded at the end of the paddling
season.
Minor gripes: Iodine-treated water has a distinctive—some would
say unpleasant—taste, and it stains plastic water bottles brown. The
taste can be removed by subsequent treatment with sodium thiosulfate or
citric acid, but this increases cost and fussiness.
Recommendations: TGHPI is hard to fault. It's the plain brown wrapper
approach to water treatment—time-tested, reliable (when used
according to package directions and with an understanding of its
limitations), and easy to use. It's got my vote.
Filters—more properly, microfilters—have also been
around a long time. Katadyn®, PUR®, and Sweetwater® are
among the most widely-advertised brands. The idea is simple: pump water
through a filter whose pores are too small for the bugs to negotiate.
Dirty water goes in. Clean water comes out. Voilà! The
implementation of this attractive idea, however, is somewhat problematic.
With one possible exception (see below), microfilters—most of which
have pores in the 0.2µm range—cannot hope to trap the great
majority of viruses. If this troubles you, and it probably should, you'll
also have to employ a supplementary germicide like iodine.
Moreover, filters aren't cheap. Up-front costs range from US$45
(Sweetwater® WalkAbout™) to the venerable Katadyn® Pocket
Filter's US$200. Operating costs—that is, the cost of replacement
filter-elements—will add another US$0.20 a gallon or so in most
instances, though with an advertised life of 13,000 gallons, the
Katadyn® should only cost around US$0.01 per gallon. (By this
measure, the expensive Katadyn® turns out to be an economy champ.
Just don't drop the ceramic filter-element on a rock. A replacement will
set you back US$165!)
Caution! Don't rely on a microfilter alone to make your drinking
water safe. They're best used in conjunction with a chemical
germicide. Many manufacturers formerly employed iodine-impregnated
filter-elements to remove viruses, and some still do. Cascade Designs,
however, has now discontinued its SweetWater® ViralGuard cartridge,
citing evidence developed in its own lab that its "portable iodine resin
bead technology…does not meet the EPA standard for purifiers."
Any minor gripes? Yes. Pumping a gallon of water through a filter will
take most people three to six minutes, and if you don't have calluses on
your hands in the right places you may get a blister. Filters must also be
meticulously maintained, and the filter-element periodically replaced. And
not all filters will survive exposure to freezing temperatures.
Recommendations: If protozoan parasites (e.g., Cryptosporidium,
Giardia) worry you, and you don't mind a little fuss and bother, a
filter is a great investment in peace of mind. Just remember to treat your
water with a germicide, as well. This belt-and-suspenders approach is as
close to bombproof as any field treatment method can ever hope to be.
And now,
THE NEXT GENERATION
One microfilter stands apart from the pack: General Ecology's First
Need® Deluxe Water Purifier, the "only chemical-free portable
system independently certified to EPA Guide Standard for Microbiological
Purifiers." And General Ecology present the summary data to back up their
claim. They're understandably reticent about revealing just how they've
accomplished this small miracle, however. The published specifications
reveal only that the Deluxe is a microfilter with a nominal pore size of
0.1µm, not enough in itself to trap any but the largest viruses.
At US$85, up-front cost is high, but not as high as the Katadyn®
filter. Operating cost is moderately high, too: US$0.30 a gallon (under
"average" conditions).
Cautions? Beyond the uncertainties inherent in the limitations of the
EPA test protocol that I've already noted, none. Belt-and-suspenders types
may still wish to treat "purified" water with a germicide.
Minor gripes? Pumping a gallon of water through the Deluxe will take
2-3 minutes, so you'll have to earn your clean water with the sweat of
your brow. (Even this nuisance can be eliminated with the "Gravity Assist
Kit," however.) You'll also need to protect the filter cartridge from
freezing.
Recommendation: The Deluxe should suit almost any paddler with US$85 to
spare, though some of us will still want the added security provided by a
chemical germicide.
Have you ever longed to own a light-saber? Well, now you can. Like the
First Need® Deluxe, Hydro-Photon's Steri-Pen®, "a small
and highly sophisticated battery-powered water purification system,"
claims to meet the criteria "set forth in the U.S. EPA Guide Standard and
Protocol for Testing Microbiological Water Purifiers" without using "toxic
chemicals." (All germicides are toxic—to germs, of course, and to
people, too, if they consume too much of them. The doses used to treat
water pose little threat to most of us, though.) And like First Need's
General Ecology, Hydro-Photon have the data to back up their claim. In
fact, they go General Ecology one better, putting all their consultants'
test reports (and their owner's manual!) on their website as PDF files.
Reading these is an eye-opening educational experience. Hydro-Photon are
to be commended for going the extra mile.
Just how does the Steri-Pen® work its wonders? By zapping bugs
with ultraviolet (UV) light. It employs no germicide and requires no
pumping. Just switch it on, stir (the Steri-Pen® actually looks more
like a hi-tech swizzle stick than a light-saber), and drink. Couldn't be
simpler. Still, the devil's in the details, and the details warrant close
attention. Arming yourself to go bug-hunting with a Steri-Pen® won't
be cheap: it costs US$199. And the operating expense is also high. If you
use alkaline batteries (an 8-pack costs US$6 in northern New York stores),
and if you get the maximum claimed battery life (chilly weather
reduces battery performance), you'll pay another US$0.60 for each gallon
of water that you purify.
But you won't be able to purify water by the gallon. A single
"treatment" is limited to a maximum of one US pint. If you need a gallon
of water at one time (to fill your water-sack for the day, say), you'll be
swirling your swizzle stick for 5-6 minutes. (Up to 8 minutes if the water
is cold.) That's not very long, admittedly, but it's still more hands-on
time than all but the slowest filters.
OK. Are there any cautions? Yes, but not too many. Don't drop the
exposed UV lamp on a rock. It will probably break—and release a
little mercury into the environment, too. And don't plan on using the
Steri-Pen® in turbid or "discolored" water. You can pre-filter turbid
water before treating, of course, but I don't know what you can do with
the tannin-stained waters of the Adirondacks and the Canadian Shield.
Minor gripes? You'll need plenty of spare batteries. Bring them. If
this doesn't appeal, you'll have to spend more money for rechargeable
cells and a solar charger.
Recommendation: The Steri-Pen® is an ingenious device, with
excellent documentation. It's perhaps better suited to inn-to-inn tours
and short trips than to extended expeditions, however. And unless you can
be sure that the waters will always run clear, don't forget to bring a
filter, too.
That's it. Thanks to Harlan and Kirk—and to all the other readers
who wrote in response to Tamia's original article—for their help in
exploring the wonderful world of 21st-century water treatment. It's
obvious that we've come a long way from the little brown pills that give
water a funny taste. Today there's a method to suit every paddler. It
doesn't matter which you use, of course, so long as you use something that
works for you. And don't forget to bring a back-up system with you on
extended trips. As I'm sure you'll agree, the taiga two-step is a mighty
poor paddling companion, and thirst is always a dangerous thing!
Speaking of the infamous two-step: Bears do it, bees do
it, even educated fleas do it. So do paddlers. Want to know more? Then
watch for When you gotta go…, the next in Farwell's series of
gutsy, in-depth reports on fundamental topics in back-country health and
hygiene. It's coming to a computer screen near you soon.
Copyright © 2002 by Verloren Hoop Productions. All rights
reserved.