The bioreactor landfilling is a waste management practice which has been introduced since the midst of 70’s. In this method, the common storage based design approach of conventional landfills is modified to enhance the biological degradation of the waste. One of the most common practices in the design of bioreactor landfills is leachate recirculation. Many research studies have demonstrated the advantages of leachate recirculation, showing that injecting leachate into landfills not only increases the stabilization rate of the waste but also improves the quality of collected leachate at the bottom of landfill. The realization of a leachate recirculation system has always been complicated by design and execution of such systems. Incorrect design of such systems would cause leachate to seep from the landfill edges and could result in unstable conditions in above ground landfilling and increased head on bottom liners. Investigations have shown that vertical and horizontal injection wells are the best methods of introducing leachate into bioreactor landfills in terms of performance. In the current research, the hydraulic properties of Municipal Solid Waste (MSW) in Iran have been measured in laboratory scale under different conditions of density and age. The results have been incorporated into the VS2DTI software to simulate the leachate flow through horizontal and vertical injection wells considering different scenarios for anisotropy and heterogeneity and ignoring the effect of gas production on leachate migration. Results show that anisotropy is more important in determination of distance of influence in injection systems compared to heterogeneity. Results of the simulations have been tabulated at the end of each section to provide guidance for designers of injection systems for preliminary assessments. Also thermal response of leachate injection into landfills has been investigated by simulating the injection of 4 o C leachate (winter conditions) and 32 o C leachate (summer conditions). Simulations show that injecting cold leachate would considerably decrease the temperature within landfill. This could reduce the waste degradation rate in landfills.