Real Time Forecast of Landfill Leachate Flowby Thomas P. Ballestero, Univ of New Hampshire, Durham, United States,
Marco Aurelio Holanda de Castro, Univ of New Hampshire, Durham, United States,
Abstract: A computer model was written to describe the generation of landfill leachate due to large precipitation events. The landfill is described as a multi-layer system, each layer having its own hydraulic characteristics. Given a rainfall hyetograph, the model then translates rainfall into a leachate hydrograph by using a sequence of saturated, then unsaturated flow equations. During high intensity rainfall, infiltrating water moves into the landfill under saturated conditions. After the cessation of rainfall, the infiltrated water moves further downward, under the influence of gravity, as unsaturated flow, until it reaches the leachate collection system. At this point, the arrival time of moisture versus time is the leachate hydrograph. For the initial piston flow of infiltrating water, a layered Green-Ampt infiltration technique was applied. For moisture redistribution after the cessation of rain, the Richards equation was solved. The model uses a finite difference algorithm to resolve the flow equations. Two locations were used to calibrate and verify the model. The first was a sand aquifer and the second was an ash monofill (incinerated municipal solid waste bottom and fly ashes). The first location served to verify how the model calculates the movement of the wetting front and moisture redistribution. The second setting allowed landfill hydraulic parameters to be calibrated for observed high intensity events.
Subject Headings: Leachates | Computer models | Landfills | Infiltration | Unsaturated flow | Water flow | Moisture | Rain water
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