Environmental Engineering Reference
In-Depth Information
Source of natural
water
Urban uses in households, urban
environment, small industry
Raw sewage generation
Wastewater treatment
Agricultural use
Ca and Na
salts and Cl
Contamination of water resources
by salinization
FIGURE 7.3
Cycle of salinization of water due to urban use. (Reprinted from Environmental Geochemistry, Vol. 9, Vengosh, A.,
Salinization and saline environments, pp. 333-366, Copyright 2005, with permission from Elsevier.)
soaps, and salts are added to domestic wastewater, which is subsequently sent to wastewa-
ter treatment plants. The salts, sodium and chloride, however, are not removed in treatment
process resulting therefore in increasing salinity of the water, as schematically illustrated
in Figure 7.3. If the treated water is used for irrigation for agriculture, for example, in areas
of the United States, Israel, and Jordan (Vengosh, 2005), groundwater and soil quality may
be impaired. The addition of road salt for deicing also contributes to the salinization of
groundwater. Powdered road salt used for deicing may be subject to wind dispersion,
resulting in contamination of the surrounding area. Although calcium chloride can be
used as a deicing salt, it is more expensive and is not as effective as sodium chloride. The
combination of sodium chloride with calcium chloride can reduce the sodium-to-chloride
ratio. To reduce the stress on the land and water resources, processes such as reverse osmo-
sis and nanoiltration will be required for desalination.
7.3.2 Effect of Traffic and Energy Use
The impacts on the environment from trafic in urban areas are in the form of airborne,
land, and water contamination. Understanding these problems and inding solutions for
reduction of emissions are of paramount importance for the health and welfare of society
and the geoenvironment. The occurrence of air contaminants from vehicular emissions
at elevated levels can lead to serious health problems for the population living in high
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