Liner compatibility with wastes

The minimum thickness specification for an FML top liner covered with a layer of soil is 0.75 mm for an FML without a soil cover layer, the specification is 1.14 mm. An FML in a composite bottom liner system must be at least 0.75 mm thick. Even though these FML thicknesses meet U.S. EPA specifications, 0.75mm is not a suitable thickness for all FML materials. In fact, most FML materials installed at landfills are in the range of 1.50-2.50 mm in thickness. Other key factors affecting the selection of FML materials include chemical compatibility with waste leachate, aging and durability characteristics, stress and strain characteristics, ease of installation, and water vapor/ chemical permeation. 

This section discusses chemical compatibility (resistance) of geosynthetic and natural liner materials with wastes and leachates. Even in a relatively inert environment, certain materials deteriorate over time when exposed to chemicals contained in both hazardous and nonhazardous leachate. It is important to anticipate the kind and quality of the leachate a site will generate and select liner materials accordingly. The chemical resistance of any FML materials, geonets, geotextiles, and pipe should be evaluated before installation.39... 

The main selection criteria for synthetic drainage materials are high hydraulic transmissivities, or in-plane flow rates, and chemical compatibility with the waste leachate. Discussion of the chemical compatibility of synthetic liners and drainage layers is given in a later section. 

The chemical suitability of any liner should be consistent with the chemicals that are going to come into contact with it (Jepson 1984), and testing should be carried out by the supplier of the liner to ensure that chemical compatibility is correct for each site (North West Waste Disposal Officers Sub-Group 1988). If chemicals harmful to clay minerals and geomem-branes/geotextiles are introduced, breakthrough may occur, and rapid pollution of groundwater becomes possible. 

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