artesian aquifer, the water in the well rises due to the artesian pressure to a level that is
near the level of the water table. In rare cases, artesian pressure may be great enough
to cause water to flow from a well.
CHARACTERISTICS AND STANDARDS OF QUALITY WATER.
As water passes over and through the earth, it takes on various characteristics
that vary with the materials encountered. The most important water characteristics are
turbidity, color, odor, taste, pH value, temperature, and dissolved gaseous and mineral
substances. Each of these characteristics has an effect on the water quality. The
Army's water quality standards are addressed, in general terms.
a. Physical Quality.
(1) Turbidity. Turbid water is muddy or unclear. Turbidity is caused by
suspended particles of sand, clay, silt, and organic material, including decaying
vegetation and animal wastes. The size of the particles carried depends on the velocity
of flow. When the flow of water stops, the larger particles settle out. Ground water (see
para 1-6d) is clearer than surface water because of the natural filtration process it
undergoes in percolating through the soil. The Army standard is to remove the particles
to which microorganism may be attached by disinfect ion.
(2) Color. Organic substances in solution such as decaying vegetation, or
inorganic substance such as manganese salts and iron usually causes the true color of
water. For this reason, water taken from swampy sources is often highly colored. True
color must be distinguished from the apparent color caused by turbidity. The color
standard is to make drinking water more, appealing and palatable.
(3) Odor and taste . Algae (minute water plants), decomposing organic
matter, dissolved gases, industrial wastes, and/or certain mineral substances most
commonly cause the odors and tastes found in water. Mineral tastes usually come from
ground water while organic tastes and odors come from surface water. Cold water has
less taste and odor than warm water. To meet palabiIity standards, remove odors and
tastes. PalabiIity does not affect the potabiIity of water.
(4) Temperature. Cool water has less odor and taste than does warm water
and is more palatable than warm water, which tastes flat. The water temperature of
deep lakes and reservoirs is colder at the bottom in the summer. Therefore, if possible,
draw relatively cool water during hot weather by shifting the intake to lower depths. On
the other hand, cool water is more viscous (thicker) than warm water and thus fiIters
more slowly. Cool water is also more difficult to coagulate and chlorinate than warm
water because of slower reactions. When the water temperature drops below 45F,
water treatment rates should be reduced. Command decisions wiII be made based
upon medical recommendations, if need be.