Understanding Water Treatment

A clear-flowing mountain stream could have some of the cleanest, purest water on earth. Or it may carry a stray microscopic pest that, if it finds its way into your intestines, could leave you weak, nauseous, cramped, bloated or vulnerable to diarrhea and vomiting for weeks.

It's a fact of modern wilderness life: Any backcountry water source, no matter how high or remote, is susceptible to contamination due to unsanitary practices of the creatures that visit it — from birds and bears to possums and humans. Many experienced wilderness travelers recognize the need to play it safe with backcountry water and thus treat every drop before they drink.

What are the risks of drinking water in the backcountry, and how can you protect yourself? Here's an overview:

The Enemies

Whenever animal or human fecal material connects with a water source, it's possible one or more pathogenic (disease-causing) microorganisms could invade the water. They fall into 3 categories:

Protozoan cysts—These are hard-shelled, single-cell parasites, including the well-known Giardia lamblia (ranging in size from 5 to 15 microns) and the resilient, lesser-known Cryptosporidium parvum (2 to 5 microns).

• Giardia infection occurs in the small intestine, where cysts "hatch." Symptoms (diarrhea, gas, nausea, cramps) appear within 1 to 2 weeks and last 4 to 6 weeks or longer. Symptoms of crypto (diarrhea, loose stool, cramps, upset stomach, slight fever) appear in 2 to 10 days and typically last 2 weeks.
• Giardiasis can be treated with prescription drugs; so far, cryptosporidiosis cannot. People with weakened immune systems could be at risk for more serious disease, particularly with cryptosporidiosis.
• Cryptosporidia are highly resistant to iodine and chlorine.
• Portable filters and purifiers with fine pores (capable of trapping particles as small as 0.2 or 0.3 microns) reliably capturethese bugs. Units should have an "absolute pore size" of 1 micron or less. (Absolute pore size indicates the largest possible opening in a filter or purifier's straining element.) UV light works by damaging the DNA of pathogens and rendering them harmless.

Bacteria— These are smaller organisms, most of them commonly associated with food poisoning: E. coli, salmonella, cholera (common in some developing countries) and others. Campylobacter jejuni has appeared with some regularity in wilderness settings.

• Bacteria range in size from 0.2 to 10 microns. Symptoms of infection (diarrhea is common) may appear within 6 hours or 3 to 5 days out. They may last 4 days or longer. In healthy people, campylobacteriosis symptoms usually vanish within 5 days. Antibiotics could be used if needed.
• Filters and purifiers are also effectivein straining out or killing these organisms.

Viruses— The tiniest (0.004 to 0.1 microns) of organisms. Examples: Hepatitis A, rotavirus, Norwalk virus and polio. (To this point, hantavirus does not appear to be a waterborne disease.) Viruses are the least common pathogens found in the wilderness.

• Viruses that afflict humans usually only reach backcountry water sources via human fecal matter. Animals and humans, meanwhile, are common carriers of protozoa and bacteria.
• Once exposed to the environment, viral particles exhibit a short lifespan and do not reproduce in water as some bacteria do.
• Viruses can slip through filters but can be inactivated by boiling, by UV light, by contacting the chemical component found in purifiers, or by chemical treatment either before or after filtration.

Chemicals and toxins— This fourth category includes agricultural runoff (pesticides, herbicides) and industrial runoff (metals, mine tailings). Some toxic bacteria can spawn algae in warm, shallow water and turn it green.

• Filters that include an activated carbon element offer some protection against such materials found in water. If you believe a water source has been tainted by chemicals or toxins, either boil the water (which offers limited benefit) or, better, move on.

A Microscopic World

None of the organic microscopic critters described above is visible to the human eye. All are measured in microns.

A micron is 1 millionth of a meter, or .0000394 of an inch. A period at the end of a sentence is roughly 500 microns. The unaided human eye cannot see anything smaller than 50 microns. The straining ability of the pores in filters and purifiers is typically measured in microns. Often you will hear friends and salespeople recommend that you seek out a "0.2-micron" filter. In a simplistic way, this is basically sound advice.

Treat Your Water Right

You have several options for treating "raw" water found in the backcountry:

Boiling

Boiling water is considered 100 percent effective against protozoan cysts, nontoxic bacteria and viruses. The U.S. Environmental Protection Agency recommends bringing water to a rolling boil for one minute to kill microorganisms. At elevations higher than 6,500 feet, the EPA says boiling time should be extended to 3 minutes.

Sounds like the perfect water-treatment solution. Yet some drawbacks exist:

• Boiling takes time (stove setup; heating time; waiting time for the water to cool).
• Boiling drains your fuel supply.
• Sediment in the water is not removed.

Note: Water boiled for meal preparation needs no additional treatment (chemical or mechanical filtration) before it is combined with a packaged freeze-dried meal.

Still, boiling is an ideal last resort if your filter clogs or you run out of batteries or chemical pills.

Chemical Treatment

Exposing water to halogens such as iodine or chlorine is believed to kill bacteria and viruses, but not all protozoan cysts. Hard-shelled cryptosporidia, as mentioned previously, show strong resistance to iodine and chlorine. You should not expect halogens alone to be 100 percent effective against this cryptosporidia.

Note: Some manufacturers and water experts recommend combining chemical treatment with filtration for maximum effectiveness. While simple and inexpensive, the use of halogens, particularly iodine, includes some additional potential drawbacks:

• Iodized water presents a taste some people find objectionable.
• Iodine can be unhealthful for some people, particularly for pregnant women, individuals with thyroid conditions or people who use it for periods of longer than 14 days.

Follow manufacturer instructions closely when using iodine or chlorine. Generally, 2 iodine tablets (such as Potable Aqua) purify a quart of water, though 1 tablet can be used to treat a quart at 50°F or warmer (basically, room temperature).

Wait 10-15 minutes for pills to dissolve; very cold water or cloudy water requires a waiting period of 30-60 minutes. Don't introduce powdered drink mixes (to camouflage the taste) until the waiting period is complete. (Potable Aqua offers optional neutralizing tablets.) Water treated by a saturated solution involving iodine crystals (from Polar Pure) also requires a 15-minute (or longer) waiting period to assure efficacy.

Adding 2 drops of household laundry bleach to a quart of water can also do the job. The bleach should be 4 to 6 percent sodium hypochlorite and should be soap-free. Some experts recommend first treating "raw" water with chlorine, then filtering it, or filtering first and then adding chlorine. Chlorine is effective against bacteria and viruses.

Mixed Oxidant Treatment

This chemical-treatment variation uses a small amount of salt and an electric current to create a mixed oxidant (MIOX) solution. The resulting process of electrolysis destroys microorganisms including Giardia, cryptosporidium and even viruses. It is powered by tiny camera batteries, so it's convenient for backcountry users.

Mechanical Filtration

Cleansing water via a mechanical process — forcing it through a finely porous internal element housed within a filtering unit — has emerged as the most popular method of nonwinter water treatment among wilderness travelers.

Portable filters and purifiers are compact, hand-pumped units that draw in water via an intake hose and physically strain out solid materials, including fine sediment and most (though not absolutely all) microorganisms.

Filtering water from a lake or stream is a relatively speedy and efficient process, though it is never as fast and easy as turning on a tap back in civilization. Filters and purifiers, in fact, can sometimes be a chore to operate,particularly when they show signs of clogging.

When shopping, be mindful of a filter's ratings for output and pump strokes per liter, and its "pump force" (how much oomph it takes to work the pump; beware of high numbers). Ratings are supplied by the manufacturers, so be aware that "your numbers may vary." Prices range from $35 to $250.

If portability and speed are not a factor, you have another option to consider: a gravity-fed "drip" filter. Here you pour water into a large reservoir, then let it slowly trickle through one (or more) filters to remove protozoa and bacteria. Such units are a good choice for car camping in remote locations.

What's the difference between a filter and purifier? Both are microbiological water-treatment devices. A filter removes protozoa and bacteria from contaminated water. A purifier does the same, plus it eliminates viruses in 1 of 2 ways:

• Through the use of an internal disinfectant (such as iodine) which inactivates (or kills) viruses — though it does not physically remove them.
• By capturing them in a filter medium that carries an electrostatic charge, a nonchemical approach taken by the First Need purifier.

Does this always make purifiers superior devices? Not necessarily. For a detailed discussion of the comparative merits of water filters and purifiers, please refer to our separate clinic, How to Choose a Water Filter or Purifier.

UV Light

A more recent alternative to the above treatments, ultraviolet light rays can be used to irradiate water. Though new to campers, this process has been used for decades by commercial bottling plants and municipal water systems. The UV process works by damaging the DNA of microbes, even viruses. Without complete DNA, germs and pathogens cannot reproduce and cause harm.

The simplicity, swiftness and size of UV purifiers are appealing to travelers of all kinds. These devices exceed the EPA standard for water purifiers by killing bacteria, viruses and protozoa such as Giardia and cryptosporidium.

Downsides? UV purifiers operate best in clear water. If water is murky or has leaves or other "floaties," it needs to be prefiltered via the manufacturer's attachment (or a coffee filter will work, too). The UV method is dependent upon batteries, too, so consider using rechargeables in conjunction with a solar charger for go-anywhere convenience.

Tips for Selecting Safer Water

Avoid filtering water in area where animal activity is obvious. Are you near signs of beaver impact? An area where the deer and the antelope have played? A meadow dotted with cow patties? Find another place to draw water.

The same principle applies to human impact.Is a heavily used campsite nearby? Are you near a trail crossing? A mine? If so, go further upstream for water.

Try to select water from still, clear water sources. Many microorganisms, particularly giardia, tend to sink in still water due to the weight of their shells; turbulence keeps them suspended.

If your only water option is melting snow or ice,choose ice. Ice supplies greater water content, but keep in mind many bacteria are impervious to freezing. Thus while boiling can kill pathogens in water, freezing cannot. Clean snow, though, is still a good source for water. Beware of pinkish "watermelon snow," however. This is a toxic algae that filtering will not remove. If you see it, look elsewhere for ice or clean snow.

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