Environmental Engineering Reference
In-Depth Information
TAble 10.5
Maximum Dissolved Oxygen (DO) Concentrations vs.
Temperature Variations
Temperature (°C)
Do (mg/L)
Temperature (°C)
Do (mg/L)
0
14.60
23
8.56
1
14.19
24
8.40
2
13.81
25
8.24
3
13.44
26
8.09
4
13.09
27
7.95
5
12.75
28
7.81
6
12.43
29
7.67
7
12.12
30
7.54
8
11.83
31
7.41
9
11.55
32
7.28
10
11.27
33
7.16
11
11.01
34
7.05
12
10.76
35
6.93
13
10.52
36
6.82
14
10.29
37
6.71
15
10.07
38
6.61
16
9.85
39
6.51
17
9.65
40
6.41
18
9.45
41
6.31
19
9.26
42
6.22
20
9.07
43
6.13
21
8.90
44
6.04
22
8.72
45
5.95
waste is known as the
biochemical oxygen demand
(BOD). We include a discus-
sion of BOD and how to monitor it later. Other sources of oxygen-consuming
waste include stormwater runoff from farmland or urban streets, feedlots,
and failing septic systems.
Oxygen is measured in its dissolved form as dissolved oxygen. If more
oxygen is consumed than produced, DO levels decline and some sensitive
animals may move away, weaken, or die. DO levels fluctuate over a 24-hour
period and seasonally. They vary with water temperature and altitude. Cold
water holds more oxygen than warm water (
Table 10.5
), and water holds less
oxygen at higher altitudes. Thermal discharges (such as water used to cool
machinery in a manufacturing plant or a power plant) raise the temperature
of water and lower its oxygen content. Aquatic animals are most vulnerable
to lowered DO levels in the early morning on hot summer days when stream
flows are low, water temperatures are high, and aquatic plants have not been
producing oxygen since sunset.
