RICHARDS EQUATION FEASIBILITY IN PREDICTING FLOW IN UNSATURATED SOLID WASTE AT A SEMI-ARID TROPICAL LANDFILL
M. A. H. DE CASTRO
AbstractThe validity of a model that calculates one-dimension, one-phase, vertical transient water flow through unsaturated Municipal Solid Waste (MSW) was verified by comparing the simulated results against data obtained in a new field experiment. The experimental data consisted of absolute moisture profiles that changed over time from columns packed with real solid wastes, measured by a Neutron Probe, and subjected to an artificial intense rain event. The artificial rain tried to simulate the precipitation intensity present in a semi-arid tropical region, The results showed that in order to adjust to the experimental curves, the field capacity had to be increased during the simulation by changing the characteristic equation empirical parameter cf. It was also found that, when used in the simulation process, the measured hydraulic conductivity at saturation (Ks = 1.71 10-04 cm/sec) was not able to represent the experimental unsaturated flow. Only by attributing large values to Ks (such as 10,000 cm/hr), was it found a good fit to the experimental curves. Although it was possible to mimic them using the Richards equation, it is evident that the conceptual model used is not a physically sound representation of the observed phenomenon.
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