Leachate Collection Systems Part 1

Components Of Leachate Collection Systems

There are many components to a collection system including pumps, manholes, discharge lines and liquid level monitors.  However, there are four main components which govern the overall efficiency of the system.  These four elements are liners, filters, pumps and sumps

Liners

Natural and synthetic liners may be utilized as both a collection device, and as a means for isolating leachate within the fill to protect the soil and groundwater below.  The chief concern is a liners ability to maintain integrity and impermeability over the life of the landfill.  Subsurface water monitoring, leachate collection, and clay liners are commonly included in the design and construction of a waste landfill.  To effectively serve the purpose of containing leachate in a landfill, a liner system must possess a number of physical properties.  The liner must have high tensile strength, flexibility, and elongation without failure.  It is also important that the liner resists abrasion, puncture, and chemical degradation by leachate.  Lastly the liner must withstand temperature variation, be black (to resist UV light), easily installed, and economical.

There are several types of liners used in leachate control and collection.  These types include geomembranes, geosynthetic clay liners, geotextiles, geogrids, geonets, and geocomposites.  Each style of liner has specific uses and abilities.  Geomembranes, are used to provide a barrier between mobile polluting substances released from wastes, and the groundwater.  In the closing of landfills, geomembranes are used to provide a low-permeability cover barrier to prevent the intrusion of rain water.

Shown here is a leachate evaporation pond in a landfill site 

Leachate Collection Systems Part 2

Geosynthetic clay liners (GCLs) are fabricated by distributing sodium bentonite in a uniform thickness between woven and non-woven geotextiles.  Sodium bentonite has a low permeability which makes GCLs a suitable alternative to clay liners in a composite liner system.  Geotextiles are used as separation between two different types of soils to prevent contamination of the lower layer by the upper layer.  Geotextiles also act as a cushion to protect synthetic layers against puncture from underlying and overlaying rocks.  Geogrids are structural synthetic materials used in slope veneer stability to create stability for cover soils over synthetic liners or as soil reinforcement in steep slopes.  Geonets are synthetic drainage materials, which are often used in lieu of sand and gravel.  Geonets can replace 12 inches of drainage sand, thus increasing the landfill space for waste.  Geocomposites are a combination of synthetic materials ordinarily used singly.  A common type of geocomposite is a geonet heat bonded to two layers of geotextile, one on each side.  The geocomposite serves as a filter and drainage medium.

Geosynthetic clay liners are a type of combination liner.  One advantage to using a geosynthetic clay liner (GCL) is the ability to order exact amounts of the liner.  Ordering precise amounts from the manufacturer prevents surplus and over-spending.  Another advantage to GCL’s is the liner can serve appropriately in areas without an adequate clay source.  Conversely, GCL’s are heavy, cumbersome, and installation is very labor intensive.  In addition to be arduous and difficult under normal conditions, installation can be cancelled during damp conditions because the bentonite absorbs the water making it even more burdensome and tedious.

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One Response to “Leachate Collection Systems Part 1”

  1. Geosynthetic Applications « Ieccovers's Blog Says:

    […] consideration.  Filtration applications are highway underdrain systems, retaining wall drainage, landfill leachate collection systems, as silt fences and curtains, and as flexible forms for bags, tubes and […]

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