Composite liner

Disposing trash on Earth mainly comes in three ways: littering, incinerating, and storing in it the many landfills we have around the world. With today’s landfills, there are very constructed contaminate structures. These systems are designed to help keep solid waste from becoming too uncontained and uncontrolled from the environment and the impact it could have on the health of humans. The purpose of having a liner system within a landfill is mainly to isolate everything within the landfill from the environment and protect it from contaminating the contents of the soil and especially the water within the ground. These liners are engineered to create a physical barrier between the garbage within the landfill, the ground, and the environment, in order to separate the liquid contaminate (leachate) so that it can go to a treatment facility. There are different types of these landfill sites for the different types of solid wastes which society creates and leaves behind. There are certain levels of harmfulness in which the different types of trash have; therefore, there are different types of liner systems which are required for these different types of disposal sites. The first type is single liner-systems. These systems usually are put within landfills which mostly hold construction rubble. These landfills are not meant to hold the disposal of harmful liquid wastes such as paint, tar, or any other type of liquid garbage that can easily seep through a single liner system. The second type is double-liner systems. These systems are usually found in municipal solid waste landfills as well all hazardous waste landfills. The first part is constructed to collect the leachate while the second layer is engineered to be a leak-detection system to ensure that no contaminates leak into the ground and contaminate everything.[1]

Components

Composite liners are required to be used in municipal solid waste systems for landfills and use a double liner system which is composed of a leachate system which is a liquid that collects solids from the substance this is passed through it. The leachate system is surrounded in a by a type of solid drainage layer such as gravel which is enclosed by a geomembrane and compressed clay, also known as a geosynthetic clay liner. This geosynthetic clay liner is usually made of sodium bentonite which is compacted in between two thick pieces of geotextile. The next material surrounding the composite liner would be a leak detection system composed of another material like gravel with an additional geomembrane or complex liner.[2] The geomembranes within the composite liner consist of a high-density polyethylene which provide an effective minimization for flow and deliver and helpful barrier which is used on inorganic contaminants.[3] It can be used as a substitute for sand or gravel and also has a very high transmissivity and low storage. The lower surface helps provide an effective leak test once correctly installed. It is also a low permeable vapor and liquid barrier. The geosynthetic clay liners are manufactured by factories and the purpose for it being made of sodium bentonite is that they regulate the movement of liquids in gases within the waste.[4] The geocomposites which are a combination of the geomembranes and geosynthetic liner material also include a layer of bentonite between the middle of the layers of geotextile; however, airspace is allowed to be implemented. It is then topped off with a final cover.

How it works

The main role a composite liner has for a municipal solid waste system for landfills is that is reduces the amount of leakage through small seep holes that sometimes form in the geomembrane part of the composite liner. The protection layer part serves as a preventer from these holes from forming inside the geomembrane which would allow the waste to leak through the entire liner(awkward sentence consider rewording). It also takes away the pressure and stress which can cause cracking and holes from forming in the membrane as well.[5] An effective liner in a landfill system should be able to control water in terms of movement and protection on the environment. It should be able to regulate the flow away from the waste area and withhold the waste contents as it enters the actual landfill. Due to the effectiveness on how landfills are placed on top of slopes in order for the water to stream downhill and in an emergency, into the actual landfill. Water moves through the landfill and downward through the composite liner. The main purpose for all of this is so that the movement is lateral which lessens the probability for slope catastrophe and the waste leaking down and freely contaminating whatever is in its path. The final cover functions as a way to keep the water out of the contaminate and to control the runoff from entering the system. This helps prevent plants and animals from being harmed by the waste contaminated water,leachate. Using gravity and pumps the leachate is able to be pushed to a sump where it is removed by a pump. When developing composite liners it is extremely important to take in risk factors such as earthquakes and other slope failure problems that could occur.[6] Composite liners are used in municipal solid waste (MSW) landfills to reduce water pollution. A composite liner is made of a geomembrane along with a geosynthetic clay liner. Composite-liner systems are better at reducing leachate migration into the subsoil than either a clay liner or a single geomembrane layer.[7]

See also

References

  1. ↑ Hughes, Kerry L. "Ohio State University Fact Sheet." Landfill Types and Liner Systems, CDFS-138-05 (2005). Retrieved from the website: http://ohioline.osu.edu/cd-fact/0138.html
  2. ↑ Composite liners improve landfill performance. (1997). Civil Engineering (08857024), 67(12), 18.
  3. ↑ Rowe, R., & Rimal, S. S. (2008). Depletion of Antioxidants from an HDPE Geomembrane in a Composite Liner. Journal Of Geotechnical & Geoenvironmental Engineering, 134(1), 68-78. doi:10.1061/(ASCE)1090-0241(2008)134:1(68)
  4. ↑ Scalia, J., & Benson, C. H. (2011). Hydraulic Conductivity of Geosynthetic Clay Liners Exhumed from Landfill Final Covers with Composite Barriers. Journal Of Geotechnical & Geoenvironmental Engineering, 137(1), 1-13. doi:10.1061/(ASCE)GT.1943-5606.0000407
  5. ↑ Dickinson, S. S., & Brachman, R. I. (2008). Assessment of alternative protection layers for a geomembrane – geosynthetic clay liner (GM–GCL) composite liner. Canadian Geotechnical Journal, 45(11), 1594-1610.
  6. ↑ O'Leary, P., & Walsh, P. (2002). Landfill cover and liner systems for water quality protection. Waste Age, 33(4), 124-129. Retrieved from http://search.proquest.com/docview/219247584
  7. ↑ "PART 258 - CRITERIA FOR MUNICIPAL SOLID WASTE LANDFILLS". gpo.gov.
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