WILDERNESS WATER DISINFECTION
Objectives: Describe how to disinfect water in wilderness situations or in devel
oping
countries.
REMOVING PARTICULATE MATE-
RIAL
River water--essentially all glacial
streams--often contains a large amount of
suspended particulate material that gives the
water a terra cotta color. (Glacial streams are
milky, gray, or grayish tan.) In the Grand
Canyon the condition of the water depends on
whether thunderstorms have recently occurred
upstream. The water is often clear. At other
times, the Colorado is described as "liquid
mud," and the silt can be removed from
equipment only by vigorous scrubbing. It fre-
quently cannot be completely removed from
clothing. Following a storm, side streams are
as muddy as the river.
If such water is placed in a container and
allowed to stand, much of the suspended ma-
terial settles, although the water may retain
some color. Hours may be required. Filling
the buckets in the evening allows the water to
be filtered the next morning.
The water can be completely cleared by
filtration. Filters used for disinfecting water
perform this function well, but most are rap-
idly obstructed and must be replaced. A filter
that can be manually cleaned is preferable.
For large groups a large volume filter such as
the Katadyn Explorer (4 l/min) serves quite
well. The filter can be removed quite easily
and scrubbed it for about twenty or thirty sec-
onds with a brush or scrubber to get rid of the
obstruction. (The large Katadyn filter does not
produce as much obstruction to flow as the
smaller filters produced by this manufacturer.)
Other filtering devices, including cloth and
coffee filters, also help remove sediment.
Flocculation can be used to clear murky
water, but is rarely necessary. The alum
needed for flocculation may not be readily
available.
DESIRABLE CHARACTERISTICS OF
WATER DISINFECTION SYSTEMS
A water disinfection system for wilderness
use must be:
·
Simple and convenient;
·
Relative fast;
·
Small and lightweight
·
Dependable.
Wilderness adventurers do not use systems
that are not simple, convenient, and fast. Hik-
ers and backpackers do not carry systems that
are not small and lightweight. If a system is
not reliable, it should not be used at all.
GOALS OF WATER DISINFECTION
The obvious goal of water disinfection is
preventing harmful or discomforting infec-
tions by water borne microorganisms. Inter-
estingly, disinfection techniques for small
quantities of water usually kill all organisms
that are present, unlike municipal water sys-
tems that typically monitor water quality by
determining the number of coliform organ-
isms present.
The most common water-borne parasites
that produce diarrheal diseases, are amoebae
(Entamoeba histolytica,) giardia (Giardia
lamblia,) and cryptosporidia (Cryptospo-
ridium parvum). When they are eliminated
from the body, all of these organisms form
