the designer to consider some of the new
complex interactions of microbial bacteria, these
technologies that can speed up solid waste stabili-
"wet landfills" may also require the addition of air
zation. Stabilization is achieved by the degradation
along with the recirculation of leachate. Lined
of the deposited refuse, mainly through de-
landfills that have been properly designed and
constructed provide leachate containment with a
lead to surface subsidence. Landfill designs offer
low risk of leakage.
(2) Gas Generation. Methane gas generation is
two options: dry or sealed landfills; and wet
considered to be a problem at some landfills.
b. Dry Landfills. Dry landfills are designed to
Therefore, the production of methane and other
seal off the solid waste in hopes of reducing
gases should be considered in the design. The
leachate production, therefore decreasing the possi-
economics of extracting methane gas as an energy
bility of leachate leakage outside of the landfill
source makes accelerated methane gas production
system. Unfortunately, studies show that solid waste
a benefit of wet landfill designs. This may require
stabilization is limited with the "dry" system.
that containing and recovering the methane gas be
Archaeological investigations have found 20 years
made part of the landfill design.
(3) Stabilization Time. The main advantage of
old refuse in existing landfills which was preserved
from the elements. Because the waste was sealed
a wet landfill is the increased rate of stabilization of
off, it was protected from the rotting influences of
the solid waste in the landfill. Studies show that the
air and moisture. While this method may require
process of leachate recirculation can speed up the
low maintenance, it could possibly require
rate of waste decomposition, by an active biological
maintenance for several decades, with little actual
process in a landfill from 50 or more years for a dry
stabilization or decomposition of the solid waste.
landfill, to just 5 or 10 years for a wet landfill. Long
c. Wet landfills.
term financial savings through eliminated or
(1) Biodegradation. Current studies have shown
reduced maintenance and long term monitoring may
that wet systems, or landfills that use leachate
outweigh the initial start-up costs and requirements
recirculation, are becoming the favored option when
for leachate recirculation, and should be considered
considering solid waste stabilization as a priority for
in the design of the sanitary landfill.
the landfill. Since most biodegradation results from