A time domain transmission method for determining the dependence of the dielectric permittivity on volumetric water content: applications to municipal landfills

Abstract

A method for determining the dependence of the dielectric permittivity of municipal refuse on its volumetric water content is developed and tested to monitor water contents throughout a municipal landfill. The method is based on time domain transmission (TDT) measurements collected with an automated network analyzer (ANA). Measurements in reference liquids, dry sand and spatially variably saturated sand were first made to test the method's ability to measure the apparent dielectric permittivity. The method was then extended to refuse samples collected from a closed 40 year old municipal landfill to determine whether a single calibration can be used to describe the relationship between the dielectric permittivity and the volumetric water content of refuse. The results show that the relationship between the dielectric permittivity and the volumetric water content within the refuse is highly site specific. The results do show, however, that a common calibration based on multiple samples collected throughout the landfill can be used to measure the volumetric water content with a root mean square volumetric water content measurement error ofless than 0.04 cm3 cm-3. It is recommended that such a calibration relationship be constructed from samples collected throughout a site before a dielectric permittivity method is selected to monitor water content at a municipal landfill.