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*Waste Management Paper 27 (WMP27)<ref name="ref27">Waste Management Paper 27 (WMP27): Landfill Gas</ref> | *Waste Management Paper 27 (WMP27)<ref name="ref27">Waste Management Paper 27 (WMP27): Landfill Gas</ref> | ||
===Leachate=== | ===[[Leachate]]=== | ||
[[Leachate]] is any liquid that, in the course of passing through waste matter in a Landfill, extracts soluble or suspended solids, or any other component of the material through which it has passed. Landfill [[Leachate]] is strongly polluting in the external environment; one of the principal reasons for constructing landfill sites as containment facilities is to prevent landfill [[Leachate]] from escaping from the waste mass in an uncontrolled manner. Escape of [[Leachate]] into the underlying groundwater is a key factor in assessing the location of a landfill and the engineering containment systems to be design. | |||
Once the design of sites moved from dilute and disperse to containment designs, as shown in the previous cross-sectional diagrams, it became necessary to devise means of avoiding | Once the design of sites moved from dilute and disperse to containment designs, as shown in the previous cross-sectional diagrams, it became necessary to devise means of avoiding [[Leachate] from building up excessively within the waste mass. There are two drivers for this: (i) in extreme circumstances, the volumes could lead to levels over-topping the sides of any containment structures and leaving the site, and (ii) designing the site to maintain levels at a level as low as practically possible would improve the '''Hydraulic Risk Assessment (HRA)''' outcome for any given design. Consequently, sites were designed with means to collect and remove [[Leachate]]. | ||
=== Groundwater and Hydrogeology === | === Groundwater and Hydrogeology === | ||
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Landfills are constructed in discrete parts known as “[[Landfill Cell|landfill cells]]”. The sub-division into cells is undertaken so as to minimise the operating area and consequently minimise leachate generation and make the site more manageable in terms of odour and litter control. Sub-division also enables the site engineering to be constructed progressively as the site fills. | Landfills are constructed in discrete parts known as “[[Landfill Cell|landfill cells]]”. The sub-division into cells is undertaken so as to minimise the operating area and consequently minimise leachate generation and make the site more manageable in terms of odour and litter control. Sub-division also enables the site engineering to be constructed progressively as the site fills. | ||
===Landfill Gas=== | ===[[Landfill Gas]]=== | ||
Another product of waste decomposition is landfill gas. This is a mixture of various components, principally methane and is a [[Biogas]] not dissimilar to that generated in an [[Anaerobic Digestion]] facility. WMP27B<ref name="refB" /> also contains a useful review of the generation and evolution of landfill gas. | Another product of waste decomposition is landfill gas. This is a mixture of various components, principally methane and is a [[Biogas]] not dissimilar to that generated in an [[Anaerobic Digestion]] facility. WMP27B<ref name="refB" /> also contains a useful review of the generation and evolution of landfill gas. | ||