Page 327 - Materials Chemistry, Second Edition

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298 Waste Management Practices: Municipal, Hazardous, and Industrial
the aquifer. The hydraulic conductivity of saturated clays is dependent upon grain size and particle
sorting and is relatively stable over time. Hydraulic conductivity in unsaturated clay is influenced
by grain size and sorting, and also by the water content in the pores.

EXAMPLE 10.1
Calculate the volumetric flow rate through a compacted clay liner at a landfill measuring 2.5 ha.
Liner thickness is 1 m and the saturated hydraulic conductivity is 10 8 cm/cc. Assume 0.3 m water
ponded on the liner.

SOLUTION

Q KAdh/dL
Q (K AH)/L
4
Convert all distances to meters, so 10 8 cm/sec 10 10 m/sec. Also, 2.5 ha 2.5 10 m 3
3
4
Q (10 10 m/sec 2.5 10 m 1.3 m)/1 m
3
3.25 10 5 m /sec
3
2.81 m /day (86,400 sec 1 day)
10.4.7 GEOMEMBRANE LINERS
Given its possible contact with a landfill leachate that is chemically complex, a geomembrane liner
must provide for substantial chemical resistance and reliable seams. The polymers most commonly
used in geomembranes are HDPE, linear low-density polyethylene (LLDPE), polyvinyl chloride
(PVC), flexible polypropylene (fPP), and chlorosulfonated polyethylene (CSPE) (Table 10.3 and
Figure 10.4) (Qian et al., 2002). A number of factors must be considered for successful geomem-
brane liner design and installation, including (U.S. EPA, 1994):

● Selection of proper membrane polymer materials
● Proper subgrade preparation
● Membrane transportation, storage, and placement
● Proper installation conditions (appropriate weather, temperature)
● Seaming and testing
● Use of construction quality assurance

TABLE 10.3
Types of Geomembranes and their Approximate Formulations

Type Resin Plasticizer Filler Carbon Black Additives
or Pigment
HDPE 95–98 0 0 2–3 0.25–1.0
VLDPE 94–96 0 0 2–3 1–4
PVC 50–70 25–35 0–10 2–5 2–5
CSPE 40–60 0 40–50 5–40 5–15
Source: U.S. EPA, 1993c.
HDPE high density polyethylene; PVC polyvinyl chloride; CSPE chlorosul-
fonated polyethylene.