Mechanisms and Patterns of Leachate Flow in Municipal Solid Waste Landfills
AbstractVertical moisture flow through municipal solid waste landfills has been represented primarily as one-dimensional Darcian flow in homogeneous media, though channeling of flow through large pores in the waste has been shown to be an important flow mechanism at high loading rates. Channeling of flow through test cells containing compacted municipal solid waste appears to be a significant flow mechanism even at low infiltration rates (0.17 mm/hr) and after steady-state conditions (infiltration = discharge) have been reached. Practical field capacity is significantly lower at 0.0996 than the HELP model field capacity of 0.294, while the average experimental porosity is identical to the HELP default value (0.52). Experimental unsaturated hydraulic conductivity values are one to two orders of magnitude higher than the HELP default value at field capacity (1.2 × 10-7 cm/s), however, these values appear to be influenced by the experimental loading rate. In order to better understand the mechanisms and patterns of moisture flow in solid waste, more detailed information on the channels such as nature of flow in the channels and the spatial distribution of the channels is needed. Also, to more accurately represent the physical system, any new leachate generation models should account for both Darcian and channeled flow.
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