Environmental Engineering Reference
In-Depth Information
Although radioactive minerals such as uranium and radium in water may
present a health hazard in particular areas, a far more dangerous threat
exists in the form of radon. Radon is a colorless, odorless gas created by
the natural decay of minerals in the soil. Normally present in all water in
minute amounts, radon is especially concentrated in water that has passed
through rock strata of granite, uranium, or shale. Radon enters homes from
the soil beneath through cracks in the foundation or through crawl spaces
and unfinished basements, as well as in tainted water. Radon is considered
to be the second leading cause of lung cancer in the United States (about
20,000 cases each year), second only to cigarette smoking. Contrary to popu-
lar belief, radon is not a threat from surface water (lakes, rivers, or above-
ground reservoirs), because radon dissipates rapidly when water is exposed
to air. Even if the water source is groundwater, radon is still not a threat if
the water is exposed to air (aerated) or if it is processed through an open
tank during treatment. Studies have shown that where high concentrations
of radon are detected within the air in a house most of that radon has come
through the foundation and from the water; however, hot water used for
showers, baths, or cooking (hot water) can release high concentrations of
radon into the air. Still, radon is primarily a threat from groundwater taken
directly from an underground source—either a private well or from a public
water supply whose treatment of the water does not include exposure to air.
Because radon in water evaporates quickly into the air, the primary danger
is from inhaling it, not from drinking it.
The Chemical Cocktail
If we were to take the time to hold a full glass of water and inspect the con-
tents, we might find that the contents appear cloudy or colored, making us
think that the water is not fit to drink. Or, the contents might look fine but
an odor of chlorine is prevalent. Most often, though, we simply draw water
from the tap and either drink it or use it to cook dinner. The fact is that typi-
cally a glass of treated water is a chemical cocktail (Kay, 1996). Water utilities
in communities seek to protect the public health by treating raw water with
certain chemicals; what they are in essence doing is providing a drinking
water product that is a mixture of various treatment chemicals and their
byproducts. Water treatment facilities typically add chlorine to disinfect,
and chlorine can produce contaminants. Another concoction is formed when
ammonia is added to disinfect. Alum and polymers are added to the water to
settle out various contaminants. The water distribution system and appurte-
nances must be protected from pipe corrosion, so the water treatment facil-
ity adds caustic soda, ferric chloride, and lime, which in turn increase the
aluminum, sulfates, and salts in the water. Thus, when we hold that glass of
