This study represents an analysis of comprehensive temperature and moisture content
data collected from the anaerobic portion of a bioreactor landfill at the New River Regional
Landfill, Florida, USA. The main focus of the study was the analysis of effects of the liquid
injection on the temperature inside the landfill. When the leachate or groundwater at lower
temperature than the landfilled waste is injected into the landfill, it has an initial cooling effect
on the waste until the biological activity, enhanced by the additional moisture, releases heat. This
cooling effect was tested in the study to determine whether it could be used to track moisture
arrival as an alternative to moisture sensors. First of all, this hypothesis of cooling effect was
tested at the injection wells by correlating temperature drops at the injection wells with known
injection events. Then the temperature drop events were identified at monitoring locations where
temperature and moisture sensors were co-located. The identification step at the monitoring
wells was more difficult than in the case of the injection wells because the cooling effect at the
injection well is more pronounced than at the monitoring sites, located 7.62 m away from the
point of injection. From the analysis it was found out that, overall, the temperature drop at
monitoring locations brought about by the injected liquid is a good criterion for tracking the
moisture arrival, however only at the first arrival of moisture. Of all of the cases studied,
temperature was able to indicate the moisture arrival for 85% of the times at the first injection as
opposed to 36% overall. The difference was attributed to the stimulation of biological activity
and subsequent heating of the injected liquid as it moves through the waste. Another focus of the
research was the estimation of the waste quantity (volume) wetted from the injection. It was
assumed that complete mixing takes places between injected liquid and the moisture already present in the waste and that the temperature of the injected liquid is the ambient temperature.
According to the results, there was a significant gap between the expected and the actual wetted
volume. The waste volume actually wetted was < 1% to 9% of the total waste volume expected
to be wetted. Also studied was the effect of ambient temperature on the waste temperature. It
was observed that the ambient temperature has no effect on the global temperature inside a
bioreactor landfill even at a shallow depth of 4.6 m. While analyzing the trend of waste
temperature inside the landfill, liquid injection was found to lead to an increase in temperature.