Travel Reference
In-Depth Information
Viruses are much smaller than bacteria and also produce a wide variety of infections.
Many cases of “traveler's” diarrhea result from infection by waterborne viruses. Hepatitis
A and polio have long been known to result from fecal contamination of water.
TECHNIQUES FOR WILDERNESS WATER DISINFECTION
Only four water disinfection methods suitable for wilderness use are available: heat, the
combination of microfiltration and chemicals, chemicals alone that require four hours or
more to remove
Cryptosporidia,
and ultraviolet light.
Heat
Heatisareliablewaytodisinfectwater.Toeliminate
Cryptosporidia
,CDCandtheEPA
recommendboilingwaterforafullminute(threeminutesabove6500ftor2000mbecause
water boils at a lower temperature at higher altitude). However, simply bringing water to a
boil is just as effective. (Milk is pasteurized, which eliminates most organisms, by heating
it to only 160°F [71°C] for twenty to thirty minutes.)
Table 6-1
Boiling Temperature of Water at Various Altitudes
Altitude
Temperature
Sea level
212°F (100°C)
10,000 ft (3000 m)
194°F (90°C)
14,000 ft (4300 m)
187°F (86°C)
19,000 ft (5500 m)
178°F (82°C)
29,000 ft (8800 m)
160°F (71°C)
Boiling is inconvenient and time consuming, particularly for small quantities of water.
Fuel must be carried, particularly above tree line. If a wood fire is built, an unsightly
residue is unavoidable without heavy, bulky firepans. Pressure cookers save time and fuel
at all elevations. No additional disinfection can be achieved by distillation.
Microfiltration
Cryptosporidia
, and possibly some other parasites such as
Cyclospora
, are resistant to
halide disinfectants, which makes microfiltration an essential element of quickly disinfect-
ing small quantities of water. (The second desirable feature of water disinfection systems
is “fast.”) Treatment with a chemical to destroy viruses is still needed following filtration
with filters that do not eliminate those organisms.
As of May 2009, the following websites for filter manufacturers were functional:
General Ecology® (First Need® filters):
www.general-ecology.com
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