Page 356 - Materials Chemistry, Second Edition

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The Sanitary Landfill 327

Start

Assemble test apparatus

Place sample in filter

Allow sampletodraininto
graduated cylinder
Paint filter

Funnel

Did any test
material
collect in Stop
graduated
cylinder?
Ring stand
Graduated
cylinder
Material is deemed to contain
free liquids; see 40 CFR
264.314 or 265.314

Stop
(a) (b)
FIGURE 10.21 Testing for free liquids: (a) paint filter test apparatus; (b) U.S. EPA test for free liquids.

Many factors are involved in the chemical, biochemical, and physical variations of landfill
leachate. The chemical complexity of leachate reflects the extreme heterogeneity of the input
wastes. Furthermore, as the waste within a landfill cell ages, the chemical properties of the
leachate will change. Climate, season, and moisture are other factors that affect composition.
Chemical properties of concern include pH, BOD , suspended solids, N content, salt content, and
5
the presence of trace toxic compounds. Some significant chemical components of landfill
leachates are listed in Table 10.14. The major classes of microbes present within leachate include
bacteria, actinomycetes, fungi, and protozoa. Microbes may be aerobes, and facultative and obli-
gate anaerobes. Biochemical, chemical, and instrumental techniques are used to measure
the types and numbers of microbial populations present. The physical characteristics of the
leachate are a function of the quantity of dissolved and suspended solids, temperature, color,
and the amount of inorganic solids such as iron and lead. Leachate sampling parameters are listed
in Table 10.15.

10.4.23.1 Estimation of Leachate Volume Produced
The volume of leachate generated in a modern sanitary landfill cell is primarily influenced by the
volume of precipitation entering the site. Assuming the facility is permitted under RCRA Subtitle
D and therefore must possess a liner, it is necessary for engineers to estimate leachate production
and to determine relevant factors for its collection, for example, the spacing of the leachate collec-
tion pipes (discussed below) at the base of the landfill.