Environmental Engineering Reference
In-Depth Information
Neutrality
Acidic range
Alkaline range
Bacteria
Plants
Bicarbonate waters
0
(a)
7
14
pH
10
-7
10
0
10
-14
(b)
[H
+
]
10
-14
10
0
10
-7
(c)
[OH
-
]
Lemon
juice
(2.3)
Pure
rain
(5.6)
Milk
(6.7)
Blood
(7.5)
Household
lye
(13.6)
Battery
acid
(0.3)
Beer
(4.5)
Orange
juice
(4.3)
Milk of
magnesia
(10.25)
Ammonia
(11.7)
Soda
(2.6)
Vinegar
(2.9)
Baking
soda
(8.4)
Wine
(3.5)
Distilled
water
(7.0)
Bleach
(12.6)
Coffee
(5.3)
Seawater
(8.0)
FIGURE 5.29
Typical pH values. (After Chapra, S.C.,
Surface Water-Quality Modeling
, WCB McGraw-
Hill, New York, 1997.)
HCO
-
CO
2-
H
2
CO
*
FIGURE 5.30
Forms of inorganic carbon.
1.00
0.75
CO
2-
H
2
CO
3
0.50
HCO
-
0.25
pK
1
pK
2
0.00
2
4
6
8
10
12
14
Solution pH
FIGURE 5.31
Variations in the fractions of inorganic forms of carbonate species as a function of pH.
amount of acid added (along with the normality of the acid and the size of the sample) is a measure of
the alkalinity of the water (usually expressed as milligrams of CaCO
3
per liter) (Figure 5.32).
The alkalinity is then a measure of water's capacity to resist changes in pH that would make the
water more acidic, commonly known as the “buffering capacity.” For example, if we add acid to
a system with an initial pH of 7 without any buffering capacity, the pH would drop immediately,
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