Environmental Engineering Reference
In-Depth Information
• Aesthetic characteristics such as color, taste and odor are of importance in cases when
natural water would be used for drinking purposes or recreation. Water sometimes
contains a considerable color, resulting from certain types of dissolved and colloidal
organic matter leached from soil or decaying vegetation. True natural color is due to
dissolved impurities. Tastes and odors in water are caused by the presence of
decomposed organic material and volatile chemicals and are measured by diluting the
sample until the taste and odor are no longer detectable by a human test. Potable water
should be practically free of color, tastes and odor.
• The temperature of water is important in terms of its intended use and treatment, as well
as an environmental indicator. It depends on the source of the water.
Figure 1.1. Solids classification in a
water sample.
2.2
Chemical characteristics
2.2.1
Inorganic constituents - specific ions and gases
• The pH of water is taken as a measure of the acidic or basic nature and is defined as the
logarithm of the reciprocal of the hydrogen ion concentration in moles per liter. Pure
water at 24
o
C is balanced with respect to H
+
and OH
-
ions and contains 10
-7
mol/l of
each type. Thus, the pH of neutral water is 7 and the range of neutrality is between 6
and 8. Acidic water has a pH lower than 6, basic water has a pH higher than 8.
• Dissolved cations and anions - the most common anions, which are naturally present in
water are carbonates, bicarbonates, sulfates, and chlorides. The most common cations
are Ca, Mg, Si, Na, Fe, Mn. The distribution of the specific species will depend on the
source of the water. If a chemical analysis of a water sample is correct, the sum of the
cations and anions expressed in terms of equivalents or milliequivalents per liter must
be the same to satisfy the electroneutrality principle. This rule (ion balance) is applied
to check the accuracy of laboratory analyses. The presence of selected ions in excess
concentrations are connected with the following characteristics:
