Page 12 - mobile Workbook-chapter 2

2.6 Field capacity

Field capacity of solid waste is the total amount of moisture that can be retained in a waste

sample subject to the downward pull of gravity. The field capacity of waste materials is of critical
importance in determing the formation of leachate in landfills [1].

The field capacity of a waste stream is of critical importance for two reasons; first, aerobic
microbial activity is optimized at or slightly below the field capacity. Therefore, biological

processing such as composting is optimized near this point. Secondly, field capacity is important

in predicting leachate formation in landfills, compost piles, or storage piles. Field capacity varies
with the degree of pressure applied to the waste and the state of decomposition of the waste [2].

The field capacity of uncompacted commingled wastes from residential and commercial
sources may range from 50 to 60% [1].

2.7 Permeability

Permeability, designated K, of compacted wastes is a physical property that strongly influences

the movement of liquids (especially leachate) and gases in a landfill [2]. Permeability is called
hydraulic conductivity. The hydraulic conductivity of compacted wastes is an important physical

property that, to a large extent, governs the movement of liquids and gases in a landfill [1].
The coefficient of permeability is normally written as:

= 2 =

where K - coefficient of permeability - specific weight of water
C - dimensionless constant or shape factor - dynamic viscosity of water

d - average size of pores k - intrinsic permeability

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