Numerical Modeling Applied to Leachate Generation using Hydrus – Case Study: Seropédica, Rio de Janeiro, Brazil

ABSTRACT Improper design and management of the cover layer of a sanitary landfill has been proven to produce harmful environmental impacts on the environment. One alternative at hand is to develop scenarios based on simulation of physical and computational models to represent the expected field water balance of a landfill coverage layer. This paper investigates the design of a sanitary landfill final cover in the municipality of Seropédica, which is located at the state of Rio de Janeiro - Brazil. More specifically, the compact soil coverage, which is widely used for landfill final cover of municipal solid waste, is evaluated in contrast to vegetation cover by grass, vegetation cover by brachiaria and capillary barrier. To accomplish such task, hydrometeorological forcing conditions, namely daily rainfall and temperature, were retrieved from the Anchieta weather station, which is situated nearby the study area. The Hydrus 1D and 2/3 D computational codes were employed to develop a set of scenarios to follow the contamination plume evolution within the landfill along the time frame of 20 years with some degree of reliability. It should be noted that the performed evaluation indicates the possibility to control the leachate release and consequently to avoid contaminating the environment, notably to prevent soil and water resources pollution. Vegetation cover by grass and brachiaria showed important control mechanisms with respect to the movement of the contaminant plume. In addition, it should be noticed that the best results for the landfill final cover were achieved for the capillary barrier, while poor performance results were obtained for the commonly employed compact soil.

Aspects Regarding the Collection and Removal of Rainfall Water on Landfill Final Cover

This paper presents an analysis of the rainwater flow on the final cover slopes of an urban landfill so as to ensure the drainage of infiltrate water through the drainage layer applied across the geomembrane of cover layer, with a runoff coefficient as low as possible. It is presented a calculation model for the transmissivity of the drainage layer depending on the thickness and on its hydraulic characteristics and also on the topsoil layer applied to the surface, as well as depending on the coating slope length. This calculation is made for both a side with a single slope (tilt) as well as for sides with two slopes. Also it is presented a mathematical model for the hydraulic calculation of surface water drainage ditches drained through the drainage layers, but also through the surface runoff, in order to establish the optimal drainage section.