Investigation into leachate transport in MSW landfills under pumping of vertical wells

Owing to the composition diversity of MSW and the compacted nature in landfills, the leachate transport in landfills is found to be dominated by the preferential flow and shows significant anisotropy (i.e., horizontal permeability higher than vertical one). The vertical well pumping and leachate level recovery tests are conducted at Chengdu landfill. Meanwhile, the leachate distribution and transportation characteristics are examined quantitatively and qualitatively using electrical resistivity tomography (ERT). Through the vertical well pumping and leachate level recovery tests, it is found that the leachate transport in landfills is highly heterogeneous. The performance of vertical wells at different regions of this landfill shows great difference, and the hydraulic conductivity of the surrounding waste ranges from 2.35×10^-5 to 3.90×10^-4 cm/s. The leachate levels in the surrounding monitoring wells change unusually under pumping of vertical wells. It is mainly due to the existence of preferential flow in the leachate transportation process. In addition, the monitoring results on changes of waste resistivity in the process of leachate pumping and recirculation by ERT further reveal that there are significant anisotropy and preferential flow characteristics in leachate transportation. And the angle between leachate seepage path and horizontal direction is found to be 0~30°.