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The Hydrodynamics of Leachate in Recirculating Landfills
Published in Debra R. Reinhart, Timothy G. Townsend, Landfill Bioreactor Design and Operation, 2018
Debra R. Reinhart, Timothy G. Townsend
The prediction of leachate quantity has been attempted by many researchers.10–13,63 Most commonly, leachate prediction is based on a water balance performed about the landfill by quantifying the processes shown in Fig. 1.1. The model most frequently used today is the Hydrologic Evaluation of Landfill Performance (HELP).” This model requires detailed information on site morphology and extensive hydrologic data to perform the water balance. The HELP computer program, which is currently in its third version, is a quasi two-dimensional hydrologic model of water movement across, into, through, and out of a landfill. Site specific information is needed for precipitation, evapotranspiration, temperature, wind speed, infiltration rates, and watershed parameters such as area, imperviousness, slope, and depression storage. The model accepts weather, soil, and design data and uses solution techniques which account for the effects of surface storage, snow melt, runoff, infiltration, evapotranspiration, vegetative growth, soil moisture storage, lateral subsurface drainage, leachate recirculation, unsaturated vertical drainage, and leakage through soil, geomembrane, or composite liners. A variety of landfill systems can be modeled, including various combinations of vegetation, cover soils, waste cells, lateral drain layers, low permeability barrier soils, and synthetic geomembrane liners. The HELP model is useful for long-term prediction of leachate quantity and comparison of various design alternatives; however, it is highly inaccurate when used to predict daily leachate production.
The Effect of Capillarity on Moisture Profiles in Landfills
Published in Bell John W., Proceedings of the 44th Industrial Waste Conference May 9, 10, 11, 1989, 1990
James J. Noble, Girish M. Nair
Water-budget models are based on numerical approximations to the Richards equation with the diffusivity term equal to zero. One such model currently in side use is the Hydrologic Evaluation of Landfill Performance (HELP) program.20,21 HELP-2, (the latest version of HELP), a quasi, two-dimensional, deterministic, EPA water-budget model, used the water balance approach to estimate leachate generation. It employs climatological, soil, and design data and predicts the percolation rate by subtracting evapotranspiration, runoff, lateral drainage, and change in soil moisture from the total precipitation. Multiple layers can be simulated. Default values are listed for the hydraulic parameters of 18 different types of soils. A weather database containing 5-year climatological data for 102 cities in N. America is includes. Details of the solution principles and modelling are described by Schroeder et al.20
Moisture Routing and Leachate Generation
Published in Syed R. Qasim, Walter Chiang, Sanitary Landfill Leachate, 2017
Fenn et al. (1975) provided a detailed method for conducting water balance calculations. Dass et al. (1977) showed moisture balance calculations for a sanitary landfill in Wisconsin. Pfeffer (1992) gave a simplified moisture routing based on net percolation and net water loss. Tchobanoglous et al. (1993) provided an example for leachate quantity calculation based on water budget analysis. Because of the tedious procedure involved in the calculation of leachate generation factors and moisture routing data, attempts have been made to develop computer simulation models for estimation of leachate generation. Lutton et al. (1979) adapted the U.S. Department of Agriculture Hydrograph Laboratory (USDAHL) model and applied this model to actual landfill conditions. A more complete model, designed specifically for landfill sites, is the HSSWDS (Hydrologic Simulation on Solid Waste Disposal Sites) model, developed by Perrier and Gibson (1980). This model was intended to assist the owners, operators and designers of the solid waste disposal sites to develop design and operation procedures. Another computer program, the Hydrologic Evaluation of Landfill Performance (HELP) developed by the U.S. Army Corps of Engineers, uses a quasi-two dimensional hydrologic model for movement of water across, into, through, and out of a landfill (Schroeder et al. 1984). Garner and Conrad (1986), reported the application of this model for the New York City Department of Sanitation. Several landfills were evaluated using this model for different design conditions. Peyton and Schroeder (1988) provided long-term simulations of 17 landfill cells using the HELP computer model. These landfills were located in different regions of the country. The results indicated that the HELP model can be a very useful tool for designing and evaluating landfills.
Risk assessment of nitrate transport through subsurface layers and groundwater using experimental and modeling approach
Published in Environmental Technology, 2018
Tamer M. Alslaibi, Ziyad Abunada, Salem S. Abu Amr, Ismail Abustan
Groundwater and leachate samples from 12 multilevel observation wells located around the Gaza landfill site were obtained and analyzed for 21 years after the landfill construction (Figure 3). Chemical and biochemical analyses were conducted at the Environment and Earth Sciences Department of the Islamic University of Gaza (IUG) in November 2008. Leachate quantity was obtained from the results of the Hydrologic Evaluation of Landfill Performance (HELP) model in a previous research [14], whereas the quality data were obtained from laboratory results. The data served as input data for the SESOIL model, which was used to predict the concentration at the bottom of the unsaturated zone to assess future concentration in the aforementioned wells.