Returning to the Well — Again

Progress Through Technology?
Water Purification Brought Up to Date

By Farwell Forrest
farwell@paddling.net

August 8, 2006

[W]hat we call "Progress" is the exchange of one Nuisance for another Nuisance.
    Havelock Ellis

It's hard to warm to a cynic, I admit, but Havelock Ellis may have gotten hold of an important truth here. In an ideal world you'd never have to ask if the water under your keel was potable. You'd know it was, and you'd just dip your cup and drink your fill. But this paradise is now well and truly lost — if it ever existed, that is. Today, the only safe rule of thumb for anyone worried about drinking the water is the well-known Fletcher Principle: If in doubt, doubt. And then disinfect.

So much for general principles. The devil, as we're reminded almost daily, is in the details. Fair enough. Just how can canoeists and kayakers make sure the water they drink won't make them sick? Since any trip that takes you farther than you can paddle in one day pretty much rules out carrying bottled water from home — the stuff is heavy, and active people need to drink often if they want to keep going — this is a very important question. And I've tried to answer it before, most recently in "Returning to the Well: The State of the Mart," an article that appeared on these pages almost four years ago to the day. Of course, four years is a pretty long time, a point that wasn't lost on one reader, who wrote in May to suggest that I revisit the topic. He then drew my attention to the "excellent [ultra]micropurifiers on the market now that filter down to the 0.02 micrometer level," and noted in conclusion that if I hadn't been keeping up on the subject, I was sure to be "pleasantly surprised."

He certainly got my attention. No one likes to be out of date, after all, and I'm no exception. I enjoy pleasant surprises, too. So I immediately went in search of a portable ultramicrofiltration system, the Holy Grail of backcountry water purification — a filter whose pores are small enough to trap the tiniest of waterborne bugs, but which is also field-maintainable and sufficiently compact to stow belowdecks in even the smallest kayak. To everyone who's struggled to keep a run-of-the mill microfilter free from clogging sediment in the untidy world outside the laboratory, this will sound like a formidable engineering challenge, and I guess it really is. To make a long story short, I searched in vain. I found residential and commercial ultramicrofiltration systems, to be sure, but nothing that a paddler could carry along into the backcountry. Still, my reader made an excellent point. I hadn't been keeping up. It was high time that I reviewed the state of the mart again. And I did.

Here's what I found. First, the good news: every system mentioned in my original article is still available, including one portable filter, the First Need® Deluxe Water Purifier, that claims to remove viruses. (This, by way of reminder, is where most microfilters fall down. They hold back bacteria and protozoan pathogens, but the much smaller viruses simply slip through the net. "Size-exclusion" microfilters, in other words, do only half the job of disinfecting water.) But the Deluxe is an unusual filter. It doesn't rely on pore size alone to exclude viruses. Its pores are no smaller than those of other microfilters, in fact — it is not a 0.02-micrometer ultramicrofilter. Instead, the Deluxe makes use of the phenomenon of adhesion. As one research paper puts it, "a combination of hydrophobic and electrostatic interaction" on the surface of an activated-carbon Structured Matrix captures and retains any viruses present in the raw water. Sceptical? I was, at first, to be honest. But the test results look good. Very good. And even the most case-hardened skeptic has to defer to fact. On the strength of the evidence presented in the peer-reviewed literature and accepted by the US Environmental Protection Agency, the Deluxe delivers the goods. End of story.

This is old news, however. As I've already mentioned, the First Need Deluxe was discussed in my earlier article, and to some extent it anticipates my reader's letter. It may not be a true size-exclusion ultramicrofilter, but it is a filter. If the cartridge is replaced regularly, no additional chemical germicide should be needed to make suspect water safe to drink. Is this the Holy Grail? It looks like it to me.

OK. Let's move on. What's new? Quite a lot, as it turns out. Three novel approaches to water disinfection caught my eye. I'll take them one at a time.

 

Nothing embodies progress quite like high-tech circuitry, right? And maybe you've been hankering to carry a personal chemical treatment plant around in your pocket. If so, you're in luck. The MSR MIOX® Water Purifier uses an electrical current to break the chemical bonds in a small amount of brine, yielding a potent cocktail of "mixed oxidants" (mostly chlorine compounds, apparently). Once added to raw water, this MIOX cocktail renders pathogenic bacteria, viruses, and protozoa harmless. Even the notoriously resilient cryptosporidia succumb, though only after four hours' contact time.

Does this sound too good to be true? It's not. Developed for the US Department of Defense, the MIOX apparently does what it claims. At a price. The upfront cost is around US$130. Steep? Yes, but still US$70 less than the venerable ceramic Katadyn® Pocket Filter, and the Katadyn does nothing about viruses. Of course, high-tech circuitry means batteries (two CR123 lithium cells, in this case), and you'll have to replace these every so often: MSR suggests that treating 50 (US) gallons will exhaust a fresh set of cells. If this is correct, figure on an operating cost of something like 26 cents a gallon of treated water, unless you can find a bargain on batteries.

Cautions? Don't spill the mixed oxidant solution on your clothes or gear. Carry plenty of spare lithium cells on long trips. And if you distrust electronic gadgetry as much as I do — MSR's reassurance that "the electronics of the MIOX Purifier are as reliable as a cell phone or GPS unit" fills me with a creeping dread — consider bringing a back-up method for the day when Nemesis strikes.

Minor gripes? I find the treatment process rather fussy. You have to (1) fill the electrolytic chamber with raw water, (2) cap the purifier and shake it 10 times (or more), (3a) check a chart to determine the number of button clicks required and then (3b) press the button the requisite number of times, (4) mix the resulting oxidant cocktail with the raw water you wish to disinfect, and (5) test the final product for free chlorine using the safety-indicator strips provided. Whew! Still, practice should soon make this seemingly complex drill almost automatic, I suppose. If you're worried about cryptosporidia, however, you'll also have to wait four hours before you can drink the water, so plan ahead. Lastly, don't use MIOX-treated water to make coffee. In MSR's words, it imparts "a strange taste." Then again, you boil your coffee water, don't you? And boiling kills bugs. Problem solved.

Recommendations? The MIOX Purifier is the answer to a technophile's prayer. It also gives you a lot to talk about around the campfire, while you measure, fill, shake, click, mix, and test. But don't expect all this to come cheap.

 

Next, let's look at the other end of the fussiness spectrum. It's hard to imagine an easier way to treat water than dropping a tablet (or two) in a canteen, shaking, and waiting ten minutes or so before drinking. That helps to explain the enduring popularity of Potable Aqua® (tetraglycine hydroperiodide, or TGHPI) germicidal tablets, despite their high per-gallon cost and other limitations. (See my earlier article for a detailed discussion.) But science marches on. Katadyn® MP-1 Micropur Purification Tablets offer all the convenience of TGHPI and more besides. While TGHPI can't be depended on to kill encysted giardia or cryptosporidia, chlorine-dioxide-releasing Micropur Tablets can — and do, though, once again, a four-hour contact time is needed to ensure that any cryptosporidia have gone belly-up. (They're tough little buggers.) Moreover, chlorine dioxide doesn't taint water to the extent that iodine-releasing TGHPI does, particularly at the higher (8-16 ppm) TGHPI label doses used by prudent paddlers.

And the price for all this? Ah, yes. The price. You had to ask. Progress doesn't come cheap. Figure on paying US$1.80 for each gallon of treated water. But at least the upfront cost is limited to the price of a 30-tablet pack: around US$14. That said, it's important to keep these things in perspective. I'll bet you drink bottled water at home. How much does this cost?

Cautions? Don't buy more than you need for one season, and check the expiry date on the package when purchasing. The shelf-life of Micropur tablets is limited to two or three years. And don't remove tablets from the blister pack until you're actually ready to treat some water. Never repackage Micropur tablets, either. They lose potency fast when exposed to air.

Minor gripes? The blister pack isn't easy to open. If you've been looking for a use for the scissors on your Swiss Army knife, you've just found one.

Recommendations: Simple. Safe. Effective. What more could you ask from any water treatment method? Cheap? Hmm.… Sorry. Nothing's perfect. But Micropur Tablets come close.

 

And now for something completely different. The final advance I encountered when reacquainting myself with the state of the art in water disinfection is really a step backward to a simpler time. Back in the day, I had an uncle who supported several wives (and many children) by dealing in used cars. Some of the cars that he sold had less than immaculate pedigrees, I'm afraid, but he wasn't a habitual villain. Mostly he bought wrecks at auction, got them running again, repainted them, and sold them on. He didn't extend credit, and he didn't offer much of a guarantee. On the other hand, his prices were low. Very low. He had his share of unhappy customers, of course, and when one of them brought a car back — or, more often, pushed it back onto the lot — my uncle would invariably promise to fix it. After all, he hated to say no. (Remember all those wives?)

Remarkably, he was a man of his word. When he promised to fix a car, he meant what he said. First, though, he parked the dead car on the lot for three days, and then phoned the purchaser to tell him it was ready for pick up. That was all. He called this happy expedient the "sunshine treatment." Amazingly enough, it frequently worked. More often than not, when the buyer came round to collect his car, it started up right away — and then kept running at least long enough for him to get it back home. This was good enough for my uncle. He didn't rely much on repeat customers, either in business or marriage.

What does all this have to do with water treatment? That's easy. It turns out that one of the simplest ways to disinfect raw water is…you guessed it…the selfsame sunshine treatment. Just park your water bottle in the sun. And wait. Sunlight — more accurately, ultraviolet radiation between the wavelengths of 320 and 400 nanometers, or UVA — inactivates most pathogens. Of course, no one calls this the "sunshine treatment." It's known as Solar Water Disinfection, or SODIS for short. Originally developed to meet the needs of rural villagers in what used to be known as the Third World, SODIS also holds great promise for canoeists and kayakers, particularly those paddlers who find themselves returning again and again to the world's great subtropical and tropical regions, either in fancy or in fact.

Sound interesting? I thought so. You won't find SODIS gear listed in any catalog, however. Why? The only equipment you need is a set of one- or two-liter plastic soda bottles (PET, or polyethylene terephthalate bottles, are best, and they must be clean, clear, and colorless), along with such efficiency-enhancing options as a lick of black paint, a plastic dishpan, and some aluminum foil. Want to know more? Just visit the SODIS website (www.sodis.ch). It should answer all your questions. In fact, it's so good that I won't go into any details here. You'll find complete instructions at the SODIS site. If you're curious, that should be your next stop. I will add a few words by way of summary, however.

Cost? Minimal. You probably have all you'll need lying around your house already. What's an empty soda bottle worth? Five cents in a state with a deposit law, maybe. Cheap enough.

Cautions? SODIS requires sunlight. It therefore works quickest when the weather's clear, more slowly on cloudy days, and not at all during prolonged sieges of rainy weather. Furthermore, it's not for paddlers who are heading up North: it's most effective at latitudes below 35 degrees. Since it's best not to agitate water violently during the treatment period (six hours under optimum conditions), it also requires a bit of forward planning.

Recommendations: Are you looking for a low-tech alternative to costly or complicated high-tech water purification systems? Do your travels take you equatorward? Then SODIS warrants serious consideration, if only as a backup (or supplement) to your primary water treatment system. It never hurts to have two strings to your bow, does it?

Progress. To paraphrase an old advertising slogan, it's humankind's most important product. But there's a very different way of looking at things, summarized in another old saying, one attributed to the French writer Alphonse Karr: Plus ça change, plus c'est la même chose. The more things change, the more they're the same. And we've seen an example in the preceding paragraphs, when one of the latest wrinkles in water treatment turned out to be something as simple as putting your water bottles on the deck to soak up some rays. Who says there's nothing new under the sun? Not me, at any rate. And that really is a pleasant surprise!

Copyright © 2006 by Verloren Hoop Productions. All rights reserved.