Geophysical Monitoring of Leachate Injection in Pretreated Waste Landfill

Landfill leachate recirculation is applied to manage the landfill as a bioreactor to enhance biogas production, limiting the impact due to greenhouse gas emissions and optimizing the energy recovery from biogas. This study deals with the geophysical monitoring of the leachate recirculation within the waste of a pretreated waste landfill. For this aim, electrical resistivity tomography (ERT) was adopted, detecting the main distribution of moisture within the waste both through the surface and through several boreholes. The electrical resistivity of waste mainly depends on water content, leachate salinity and temperature. The method is sensitive to the transient phenomena associated with leachate flow within the waste; moreover, the ERT long-term monitoring data suffer from anomalous and unexpected polarization phenomena induced by the measurements themselves. Results demonstrated the reliability of this approach to qualitatively detect the landfill volume affected by the leachate circulation. The effects of moisture changes by leachate infiltration on biogas production are still challenging, notwithstanding a positive effect on methane concentration in biogas itself is evident.