What are the risks of drinking water in the backcountry, and how can you protect yourself? Here's an overview:
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.
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.
You have several options for treating "raw" water found in the backcountry:
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:
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.
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:
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.
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.
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.
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:
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.
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.
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.
By T.D. Wood
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Last updated: Thu Aug 16 14:45:22 PDT 2012
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