Environmental Engineering Reference
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3.
Evaporation of leachate
4.
On-site or off-site treatment
5.3.2 Gas Collection System
Landfill gas is generated as the wastes decompose. Biological degradation of the
waste initially may be aerobic due to presence of oxygen. Later, as the oxygen
is depleted, the process becomes anaerobic. Methane and carbon dioxide are the
principal gases produced. Figure 7.5 presents this change in gas composition in
a landfill over time.
The following parameters affect the rate of decomposition and gas generation
rate:
•
Moisture content
•
Availability of nutrients
•
Absence of oxygen and toxics
Aerobic
Anaerobic
100
Phase I
Phase II
Phase III
Phase IV
90
80
70
60
45-60%
50
40-60%
40
30
20
10
2-5%
0
Note: Phase duration time varies with landfill conditions.
Source: U.S. EPA 1997
Figure 7.5
Change in gas composition in a landfill over time (U.S. EPA 1997)
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