Geoscience Reference
In-Depth Information
wild animal feces contain traces of
Giardia
. Surface waters in agricultural areas are usually
even more severely infected with
Giardia
and
Cryptosporidium
than the mountainous regions,
since livestock are major carriers of these pests.
Western nations have developed vast systems of water purification, storage, and distribu-
tion designed to protect us from traditional waterborne diseases, but waterborne diseases and
parasites continue to plague most of the population of this planet, particularly in the third
world. In typical disaster situations, modern systems for purifying and distributing clean water
often fail. In these situations, to protect your health, you must purify your own water. Basic in-
formation on contaminants is presented here so that you will better understand the limitations
of particular water-treatment options. Subsequently, a variety of water-treatment options are
presented, and I offer my personal recommendations on particular brands and types of water
treatment.
Types of Contamination
Bacteria
Bacteria, commonly called “germs,” are single-celled organisms; they are spread by wind, wa-
ter, person-to-person contact, animal feces, and contaminated food. You can't be sure that any
surface water is free of harmful bacteria, even when it is crystal clear and there are no signs of
human habitation. Some examples of harmful waterborne bacteria are cholera,
Campylobacter
jejuni
, salmonella, and some varieties of
E. coli.
They multiply by cell division when they are
in a “friendly” host environment, which provides them with food and temperatures suitable for
growth. Given a positive growth environment, like feces-polluted water or a human body with
a compromised immune system, one bacterium cell may multiply into millions within just a
few hours. Signs of bacterial infection usually show up from six hours to three days after ex-
posure.
Bacteria are killed by boiling, ultraviolet sterilization, ozone, or chemical treatment,
provided the treatments are applied at the proper concentration and temperature and for the
proper length of time. Bacteria are tiny, on the order of 0.3 microns to several microns in size,
and visible only under a powerful microscope. One micron is a millionth of a meter long. To
give you a better idea of how tiny a micron is, realize that a single human hair is about 76 mi-
crons thick. Filters rated at 0.2 microns or less are usually effective against bacteria, but bacter-
ia can grow through some filter media over a period of time.
