Heat Transport Modeling in an Aquifer Downgradient a Municipal Solid Waste Landfill in Italy

Abstract

Heat generation inside municipal solid waste (MSW) landfills is due to aerobic and anaerobic exothermic reactions occurring inside the waste. The result of heat generation and transport inside sanitary landfill leads to a temperature field that varies from mesophylic range (optimum at 30-40°C) to thermophylic range (optimum at 50-60°C). Due to high temperatures at the bottom of the landfill, liner systems can be severely damaged. The increment in convective and conductive heat transport could lead to an increase of the temperature in the surrounding geological layers and in the underlying aquifer. Hydrodynamic thermodispersion and convection are the most important mechanisms of heat transport in saturated porous medium with a moving fluid such as aquifer systems. The aim of the study is to model and investigate the origin of a thermal anomaly in the aquifer underneath a municipal landfill in the North of Italy. In order to model the system a detailed experimental analysis was conducted inside the landfill, measuring the temperature of the biogas and leachate, and in the aquifer system measuring the temperature in monitoring wells and conducting a constant rate pumping test. Heat transport model has been exploited using the analogy between heat and mass transport in porous media. The model showed that the thermal anomaly is due to convective and conductive heat transport from the landfill to the aquifer.