Comparison of Resistivity and Time Domain Reflectometry Sensors for Assessing Moisture Content in Bioreactor Landfills

Instruments that can monitor the in situ moisture content of landfilled waste would be of great benefit to landfill operators, especially those operating their facilities as bioreactor landills (wet landfills). Two instrumentation technologies for measuring in situ moisture content (resistivity sensors and time domain reflectometry (TDR)) in landfills were examined and compared. Resistivity and TDR instruments were installed in close proximity at multiple locations in a leachate recirculation well field at a bioreactor landfill in Florida, and resulting moisture content measurements were assessed. The resistivity instruments were less expensive, easier to install, and found more reliable over time than TDR sensors. Both technologies predicted transient moisture changes in the landfill. The magnitudes of the moisture content values obtained using the two technologies were much higher compared to values estimated using mass balance, suggesting that accurate calibration to field conditions is difficult.