4. Contamination of Water. A "contaminant" is a general term for a harmful impurity, which makes
water unfit for human consumption or domestic use. Contamination of water may be caused by disease-
producing organisms, by industrial waste and other materials, or by NBC agents.
a. Waterborne Disease-Producing Organisms. Water is a carrier of many organisms, which
cause intestinal disease. An epidemic of one of these diseases among Army troops can be more
devastating than enemy action and can cause great damage to morale as well as health. A heavy
responsibility thus rests upon any water supply section, and vigilance over water purification equipment
and procedures should never be relaxed. A waterborne disease rarely produces symptoms in its victim
immediately after he has drunk the contaminated water. A period of time known as the incubation
period must pass before the victim comes down with the disease. During the incubation period, the
disease organisms are multiplying and growing. Absence of symptoms for several days after untreated
water has been drunk is, therefore, no guarantee that the water is safe. Also, absence of disease among
the local inhabitants is no assurance of safety, because they may have developed immunity.
b. Types of Waterborne Disease. These diseases include: typhoid fever, paratyphoid fever,
cholera, bacillary dysentery, common diarrhea, infectious hepatitis, and schistosomiasis.. The last-
mentioned disease is the result of infection by the larvae (cercariae) of the blood flukes (schistosomes).
The snail host of the schistosomes liberates large numbers of the cercariae into the water and drinking
the water will cause infection. Also when the water dries on the skin of human beings, the cercariae
then burrow into the skin and infection occurs. The testing for microorganisms in water is difficult and
the number of these organisms is usually very low, even in a badly contaminated water supply. For
these reasons, indicator organisms are used to detect the presence of contamination. The bacterial
organisms used as an indicator of possible contamination are total coliform. These organisms occur in
large quantities in the intestines of warm-blooded animals. The presence of any coliform organism in
treated water is an indication of inadequate treatment or the introduction of undesirable material to the
water after treatment. The test to detect a surrogate organism, E. coli, is simple and effective for field
use. This is known as the filter membrane technique and is used to determine the presence of coliform
organisms in treated water. This test is conducted by preventive medicine on behalf of the command
surgeon. Over the years there have been accelerated research and development in biological agents and
the means of dissemination. Biological agents, if deployed today, can be of major significance, and field
water sources would undoubtedly be contaminated. The agents which could be used include the
spectrum of pathogenic organisms.
c. Industrial Wastes. Most industrial wastewaters are derived from cooling, washing, flushing,
extracting, impregnating, chemical treatment, and similar operations. They are varied in quantity and
nature as the products and processes of the industrial plants from which they drain. Toxic metals and
chemicals discharged as industrial waste may destroy the biological activity of streams and cause
receiving waters tastes and odors that are almost impossible to remove by water purification. Strong
acids and alkalies may be corrosive to metals. The use of raw water sources containing measurable
quantities of industrial waste should be avoided. If
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