Environmental Engineering Reference
In-Depth Information
DID YoU KNoW?
Water weighs 62.416 pounds per cubic foot at 32°F.
Tu r bid it y
Turbidity is a unit of measurement quantifying the degree to which light
traveling through a water column is scattered by the suspended organic
(including algae) and inorganic particles. The scattering of light increases
with a greater suspended load. Turbidity is commonly measured in
neph-
elometric turbidity units
(NTUs) but may also be measured in
Jackson turbidity
units
(JTUs).
Note:
To obtain nephelometric turbidity units, observers compare the
light scattered by the sample and the light scattered by a reference
solution:
•
Detection limits
—Should be able to detect turbidity differences of
0.02 NTU with a range of 0 to 40 NTU
•
Interferences
—Rapidly settling coarse debris, dirty glassware,
presence of air bubbles, and surface vibrations
The velocity of the water resource largely determines the composition of
the suspended load. Suspended loads are carried in both the gentle currents
of lentic (lake) waters and the fast currents of lotic (flowing) waters. Even
in flowing water, the suspended load usually consists of grains less than
0.5 mm in diameter. Suspended loads in lentic waters usually consist of the
smallest sediment fractions—silt and clay.
Turbidity plays an important role in drinking water quality, for, without
a doubt, one of the first things consumers notice about water is its clar-
ity. Turbidity may be caused by organic or inorganic constituents, but the
organic particulates may harbor microorganisms; thus, turbid conditions
may represent a threat of waterborne disease (see
Chapter 6
). Turbidity may
be classified as both a physical parameter, because it can raise aesthetic and
psychological objections by the consumer, and as a microbiological param-
eter, because it may harbor pathogens and impede the effectiveness of
disinfection.
Note:
Inorganic constituents have no notable health effects.
