chapter 4: temperature inside the landfill

medium and water moves between this porous medium and the waste until both are at
equilibrium with identical matric potentials. The moisture content can then be estimated using a
previously determined calibration curve. In soil applications a gypsum wafer is placed in the
porous medium and the dissolving gypsum increases the ion concentration sufficiently so that it
is not a variable affecting the performance of the sensor. However in landfills, leachate ion
concentrations are typically quite high.
Gawande et al (2003) developed a sensor at the University of Central Florida to measure
moisture content (electrical resistance), gas quality, and temperature. It was calibrated in the
laboratory for different values of conductivity and the following equations were developed:
At 4.0 mS/cm:
At 8.0 mS/cm:
MC =
1−
14.
795
0.
785exp(
−0.
0142R)
30.
068
MC =
1−
0.
568exp(
−0.
0167R)
(2-12)
(2-13)
Where MC is the moisture content of solid waste, and R is the resistance value measured
from the sensor.
Also the effect of temperature on the value of the measured resistance was quantified by
the following equation:
⎡1+
0.
02(
t − ⎤
2 25)
R1
= R2
⎢
⎥
⎣1+
0.
02(
t1
− 25)
⎦
(2-14)
Where R1 is the resistance at temperature t1, and R2 is the resistance at temperature t2.
13