There are 3 very important Water-Content Terms Used in the Landfill Industry for the water balance calculations used to predict leachate volumes generated duiring the active life of a landfill site, and these are:
Field capacity is the amount of liquid that a given mass of material will absorb prior to downward percolation of that liquid due to gravitational forces. This definition is satisfactory for homogeneous materials such as soils (where the term is more commonly used) and perhaps for municipal waste in landfills. However, it is important to always be aware that with municipal waste, downward percolation invariably occurs before all the field capacity has been utilized. Waste constituents absorb liquid to different degrees, and some channelling also occurs.
To watch this video on the YouTube website follow this link: Field capacity definition definition for Landfill Designers.
Absorptive capacity is a term perhaps more suited to define the volume of liquid a given mass of crude refuse will-absorb prior to significant leachate generation. Field capacity would then be further clarified as being the total amount of liquid absorbed by a given mass of refuse under equilibrium conditions below which downward percolation will not occur.
To watch this video on the YouTube website follow this link: Absorptive capacity definition for Landfill Designers.
Saturation capacity is the total volume of liquid a given mass of refuse can hold including void space utilisation. The saturation capacity may not be much higher than either absorptive or field capacities as refuse density increases and because there is evidence that perched water exists (on plastic bags etc., and in areas where blinding of waste by access track materials etc occurs), even before the absorptive capacity is exceeded.
In practise all three types of water holding capacity defined above will vary from site to site and within sites, depending on the type of refuse and depth/density both initially and after subsequent settlement.
To watch this video on the YouTube website follow this link: Saturation capacity for Landfill Designers.
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