Environmental Engineering Reference
In-Depth Information
that could be used for estimating the degree of stabilization obtained within fills
under the saturated or submerged conditions prevalent at Bangkok during the
six-month rainy season Figure 4.17 illustrates the relationship between the rate
of gas production and the percentage moisture content in landfills. Information
was also gathered on problems in utilizing completed fill sites as related to
degree of stabilization and/or compaction. To supplement the review and literature
available at Bangkok, a canvass was made of past and ongoing research on refuse
landfilling stabilization phenomena. The results of the review are as follows:
There are several types of stabilization/gas production phenomena going on
in a fill including aerobic, facultative, and anaerobic, with the anaerobic phase
representing the main mechanics for achieving gas-production (both methane
and carbon dioxide) and hence stabilization. These various phenomena into
be classified in five stages: (1) initial adjustment, (2) transition, (3) acid for-
mation, (4) methane fermentation, and (5) final maturation
127
.
•
In a typical U.S. fill, a total of about 600 days is required to complete
stabilization under usual conditions in practice. However, various studies
show that the stabilization can be speeded up by increased temperature (up
to 41
◦
C), and especially by increasing moisture content, because the unsat-
urated portions of the fill tend to remain within the acid formation phase,
whereas when the materials become saturated, methogenesis develops very
rapidly. Under Bangkok conditions, saturation would be the norm during
the rainy season (about 6 months).
•
While the data are limited, the available data indicate that the rate of gas
production (total gas) may be roughly expressed by the equation:
•
log
R
=
0
.
0125Md
+
0
.
5
where
R
=
gas production in ml/kg/day and M
d
is the moisture content of
the fill on a dry weight basis.
Study Conclusions
Because of the fact that practically all research stud-
ies on refuse landfilling have been conducted in the Western countries, there
is a well-meaning tendency in the Western technology against the concept of
depositing organic refuse at ground elevations below groundwater levels. Western
technology requires that all filling be at levels above groundwater, and moreover,
a great deal of research and development over the past two decades has been
focused on developing practicable methods for preventing leachate percolating
from fills downward into the groundwater strata. The objectives are to protect
the groundwater quality from pollution because, in many situations, the ground-
water, including strata near the surface, are used as a source of water supply
for community and industrial purposes. In other words, under normal conditions,
without use of planned refuse filling, the groundwater is not generally polluted
and it is desired to keep it clean.
