Landfills are waste treatment sites where the waste is disposed of by means of its surface or sub-surface deposition. The location and design of every landfill must pose no pollution threat to the soil and the surface or underground water – both during the operational phase of the landfill and after it when the landfill’s maximum storage capacity has been reached. The choice of sealing materials depends on the type of waste concerned, most often the system comprises a combination of a geological barrier and an artificial lining system. The latter of the two parts of this multi-layered structure is represented by geosynthetic liners generally known as geomembranes.
Geomembranes made from high-density polyethylene (PE-HD) are used almost exclusively (because of their chemical resistance and durability) as bottom liners in landfills and various waste disposal sites (such as ash deposit sites where the waste created by coal burning power plants is stored). The following parts of the sealing multilayer system usually comprise a protecting geotextile used to prevent the geosynthetic barrier layer from being damaged during the installation of drainage and a protective layer of aggregate placed on the top of it.
Should it become necessary to avoid the penetration of seepage water into the landfill body after filling the landfill up to its maximum storage capacity, a surface sealing system must be installed. In those cases, geomembranes made from low-density linear polyethylene (PE-LLD) are often used. These products are characterized by a higher level of adaptability to significant spatial deformations of the underlying layers.
The purpose of the drainage layer is collecting leachate water from the landfill body and transferring it into reservoirs where the same type of PE-HD-based membranes is used as a bottom liner.