Model comparison of flow through a municipal solid waste incinerator ash landfill

The drainage discharge of a municipal solid waste incinerator (MSWI) bottom ash landfill was simulated using various modelling approaches. Two functio nal models including a neural networks approach and a hydrological linear s torage model, and two mechanistic models requiring physical/hydrodynamic pr operties of the waste material, HYDRUS5 and MACRO (Version 4.0) were used. The models were calibrated using an 8-month data set from 1996 and validate d on a 3-month data set from winter 1994/1995. The data sets comprised hour ly values of rainfall, evaporation (estimated from the Penman-Monteith rela tionship), drainage discharge and electrical conductivity. Predicted and me asured discharges were compared. The discharge predicted by the functional models more exactly followed the discharge patterns of the measured data but, particularly the linear storag e model, could not cope with the non-linearity of the system that was cause d by seasonal changes in water content of the MSWI bottom ash. The lit of t he neural networks model to the data improved with increasing prior informa tion but was less smooth than the measured data. The mechanistic model that included preferential discharge, MACRO, better modelled the discharge char acteristics when inversely applied, indicating that preferential flow does occur in this system. However, even the inverse application of HYDRUS5 coul d not describe the system discharge as well as the linear storage model. Al l model approaches would have benefited from a more exact knowledge of init ial water content. (C) 2001 Elsevier Science B.V. All rights reserved.