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Making water safe to drink.

When it comes to drinking water, don't presume that it is pure just because it looks clear. Even the most remote stream or lake in the wilderness may contain Giardia lamblia or other parasitic microorganisms that can cause intestinal ailments.

The commonest ailments--giardiasis--is an infection caused by an intestinal parasite that lives part of its life cycle outside the body as a cyst in feces. Humans can transmit it, but the most likely carriers--particularly in wilderness areas--are wild animals (beavers, deer, muskrats) and transient livestock.

Giardia isn't the only waterborne threat, particularly if you travel abroad. Other bacteria, viruses, and protozoa can cause illnesses ranging from diarrhea and dysentery to cholera and typhoid.

When you can't carry a safe supply, you can take steps to purify tainted water. The three preferred purification methods are boiling, chemical disinfection, and filtering. Which to use depends on the length of the trip, and where and how you travel.


Boiling is the safest way to kill all three major types of disease organisms in suspect water, according to Dave Spath, chief of the technical programs, branch in the Office of Drinking Water of California's Department of Health. Spath recommends boiling water for a full 5 minutes, particularly at higher elevations, where water boils at a lower temperature.


If you're just out for a day-hike, or if boiling water is inconvenient, several commercially available chemical treatments protect against giardia and other microorganisms. Most of these products ($5 to $15 at outdoor supply stores) use iodine or chlorine as a biocide.

Iodine-based products like Potable Aqua ($5 for 50 tablets) are good to have for emergencies, but shouldn't be relied on regularly. If you want to carry something small and inexpensive to treat your water, tetraglycine hydroperiodide tablets do a good job in purifying water. But they have some drawbacks: the iodine imparts a medicinal taste, you have to wait 20 minutes or more before drinking the water (Spath advises letting the water stand overnight), and, once the bottle is opened, iodine tablets lose their potency within six months. Also, extended ingestion of iodine may pose health risks.

Chlorine is an alternative to iodine. Sierra Water Purifier combines chlorine and hydrogen peroxide. The chlorine zaps the microorganisms, then the hydrogen peroxide oxidizes the chlorine, breaking it down so there's little aftertaste. The Sierra Water Purifier kit ($15) comes in two small bottles, enough to treat about 160 gallons. As with the iodine treatment, you have to measure and mix, then wait (overnight is best) before drinking the water.


Portable water filters and purifiers require no mixing or measuring; you can drink the filtered water immediately after drawing it from a stream or lake--one reason they're a favorite of backpackers. Filter devices cost $25 to $250, and they will treat a hundred to more than a thousand gallons of water before their filters need replacing. One drawback: the cost of a replacement filter can run 50 percent of the unit's initial price.

These products work by using fine membranes to filter out impurities in the water, including giardia and some bacteria, but they do not filter out viruses; you could, for instance, still catch hepatitis A (for overseas travel, use a chemical treatment).

Reliability is another concern. Portable water filters do not have to be state certified. "You're depending on the manufacturer's word as to how well they really work," says Spath, who also notes that filters may break or not work properly.

Some products, like General Ecology's First Need Deluxe system ($45), include a food dye to test the filter's integrity. But that won't do you any good if you learn the filter has failed midway through a trek in the wilderness.

Two products from PUR, Traveller ($60) and Explorer ($140), add an iodine treatment to a filter to kill bacteria and viruses and to eliminate parasites like giardia.

Consider using a filter as a backup or in combination with another method--boiling or chemical disinfection--to provide an extra margin of protection.


If the storage container becomes contaminated, the water inside can be tainted by contact. Amber Cottle, manager of Adventure 16, an outdoor store in Costa Mesa, California, notes that backpackers and bicyclists who place a container of pure water to cool in a contaminated stream can still contract giardia if they don't sterilize the container before they drink from it.
COPYRIGHT 1992 Sunset Publishing Corp.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Author:Lansing, David
Date:Jul 1, 1992
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