Environmental Engineering Reference
In-Depth Information
Volatile Organic Chemicals
Volatile organic chemicals (VOCs) are a particularly dangerous type of
organic chemical. VOCs are absorbed through the skin during contact with
water—as in the shower or bath. Hot water exposure allows these chemicals
to evaporate rapidly, and they are harmful if inhaled. VOCs can be found in
any tap water, regardless of where one lives and the water supply source.
Total Dissolved Solids
Solids in water occur either in solution or in suspension, and they are dis-
tinguished by passing the water sample through a glass-fiber filter. By defi-
nition,
suspended solids
are retained on top of the filter, and
dissolved solids
pass through the filter with the water. When the filtered portion of the water
sample is placed in a small dish and then evaporated, the solids in the water
remain as residue in the evaporating dish. This material is referred to as
total
dissolved solids
(TDS). Dissolved solids may be organic or inorganic. Water
may come into contact with these substances within the soil, on surfaces, and
in the atmosphere. The organic dissolved constituents of water come from
the decay products of vegetation, from organic chemicals, and from organic
gases. Removing these dissolved minerals, gases, and organic constituents
is desirable, because they may cause physiological effects and produce an
aesthetically displeasing color, taste, or odor.
Note:
In water distribution systems, high levels of TDS indicate high con-
ductivity with consequently higher ionization in corrosion control; how-
ever, high TDS levels also indicate the greater likelihood of a protective
coating, a positive factor in corrosion control.
Fluoride
Water fluoridation prevents tooth decay primarily through frequent, daily
contact with low levels of fluoride (CDC, 2011). Even today, with other avail-
able sources of fluoride, studies show that water fluoridation reduces tooth
decay by about 25% over a person's lifetime; in fact, drinking water contain-
ing a proper amount of fluoride can reduce tooth decay as much as 65%
in children between the ages 12 and 15. It should be pointed out, however,
that water fluoridation is not necessarily the safe public health measure we
have been led to believe it is (Mullenix, 1997). Concerns about uncontrolled
