Modelling Leachate Quality and Quantity in Municipal Solid Waste Landfills

Abstract

The operational phase of landfills may last for 20 years or more. Significant changes in leachate quality and generation rate may occur during this operational period. A mathematical model has been developed to simulate the landfill leachate behaviour and distributions of moisture and leachate constituents through the landfill, taking into consideration the effects of time-dependent landfill development on the hydraulic characteristics of waste and composition of leachate. The model incorporates governing equations that describe processes influencing the leachate production and biochemical processes taking place during the stabilization of wastes, including leachate flow, dissolution, acidogenesis and methanogenesis. To model the hydraulic property changes occurring during the development stage of the landfills, a conceptual modelling approach was proposed. This approach considers the landfill to consist of cells or columns of cells, which are constructed at different times, and considers each cell in the landfill to consist of several layers. Each layer is assumed to be a completely mixed reactor containing uniformly distributed solid waste, moisture, gases and micro-organisms. The use of the proposed conceptual model enables the incorporation of the spatial changes in hydraulic properties of the landfill into the model and also makes it possible to predict the spatial and temporal distributions of moisture and leachate constituents. The model was calibrated and partially verified using leachate data from Keele Valley Landfill in Ontario, Canada and data obtained from the literature. Ranges of values were proposed for model parameters applicable for real landfill conditions.

System tradeoffs in siting a solar photovoltaic material recovery infrastructure

“…Previous studies elevation criteria for siting landfills widely vary, buffering at slopes less than 15 (Bah and Tsiko, 2011;Gemitzi et al, 2006), 30 (Delgado et al, 2008), 50 (Guiqin et al, 2009), and between 8 and 12 (Çelik et al, 2010;Yildiz et al, 2004). We set buffers at elevations between 0 and 12 with 8e12 being most favorable and 0 being the lease favorable because the above research suggest landfill failures and contamination of water bodies from runoff can be controlled at these angles.…”

“…The use of spatial statistics for this purpose consists of three parts: average nearest neighbor index (ANNI), p-value, and z-score calculations. The average nearest neighbor index has been used to determine clustering of epidemics, diseases (Delgado et al, 2008;Kan et al, 2008;Lai et al, 2004), natural phenomenon (Bishop, 2010(Bishop, , 2007Guiqin et al, 2009), and population demographic densities (Austin et al, 2005;Çelik et al, 2010;Fisher et al, 2007;Yildiz et al, 2004). It compares the observed mean distance D O between each feature and its nearest neighbor with the expected mean distance D E for a feature in a random pattern (normal distribution) as shown in equation (1) (Alves et al, 2009;Smith et al, 2007).…”

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“…Thus, the domain for the refuse was divided into five layers, and the permeability of each layer was specified assuming that the permeability of the waste decreased exponentially with depth. This assumption was based on an empirical relationship between vertical stress and hydraulic conductivity in landfills (Yildiz et al, 2004). Since the vertical stress was approximately proportional to the thickness of the waste above the measuring point, the depth below the landfill surface can replace vertical stress in Yildez et al's expression [Yildiz et al, 2004] , respectively.…”

“…This assumption was based on an empirical relationship between vertical stress and hydraulic conductivity in landfills (Yildiz et al, 2004). Since the vertical stress was approximately proportional to the thickness of the waste above the measuring point, the depth below the landfill surface can replace vertical stress in Yildez et al's expression [Yildiz et al, 2004] , respectively. The vertical permeability k v was selected to be 10 times smaller than the horizontal permeability.…”

Influence of Recycling Different Leachate Volumes on Refuse Anaerobic Degradation

“…A traditional landfill is a facility engineered for the final disposal of MSW that is designed and operated to minimize the negative impacts on the environment and on public health [6], but needing 20 or more years for stabilization [7,8]. Given these long-term post-closure periods, barriers originally installed in the landfill are prone to exceed their useful life, thus opening the possibility for the infiltration to the soil of leachate and for the emission to the atmosphere of biogas, impacting on the environment and on public health [4,9].…”