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Chapter: Civil - Municipal Solid Waste Management - Disposal

Landfill Operation Issues

(i) Site infrastructure (ii) Earthworks (iii) Lining landfill sites (iv) Leachate and landfill gas management (v) Landfill capping


LANDFILL OPERATION ISSUES

 

(i) Site infrastructure: The size, type and number of buildings required at a landfill depend on factors such as the level of waste input, the expected life of the site and environmental factors. Depending on the size and complexity of the landfill, buildings range from single portable cabins to big complexes.

need to  comply  with  planning,   building,   fire,   health   and  safety regulations and


controls;

 

security and resistance to vandalism;


durability  of  service  and  the  possible  need  to  relocate  accommodation  during the


lifetime of the site operations;

 

ease of cleaning and maintenance;


availability         of  services  such  as  electricity,  water,  drainage  and telecommunication.


Paying some attention to the appearance of the site entrance is necessary, as it influences the perception of the public about the landfill site. All landfill sites need to control and keep records of vehicles entering and leaving the site, and have a weighbridge to record waste input data, which can be analysed by a site control office. Note that at small sites, the site control office can be accommodated at the site itself.

 

(ii)                 Earthworks: Various features of landfill operations may require substantial earthworks, and therefore, the working plan must include earthworks to be carried out before wastes can be deposited. Details about earthworks gain significance, if artificial liners are to be installed, which involves grading the base and sides of the site (including construction of 25 slopes to drain leachate to the collection areas) and the formation of embankments. Material may also have to be placed in stockpiles for later use at the site. The cell method of operation requires the construction of cell walls. At some sites, it may be necessary to construct earth banks around the site perimeter to screen the landfill operations from the public. Trees or shrubs may then be planted on the banks to enhance the screening effect. The construction of roads leading to disposal sites also involves earthworks.

 

(iii)              Lining landfill sites: Where the use of a liner is envisaged, the suitability of a site for lining should be evaluated at the site investigation stage. However, they should not be

 

installed,  unt il the site has  been properly prepared.   The area to be lined should be free of objects likely to cause physical damage to the liner, such as vegetation and hard rocks. If synthetic liner materials are used, a binding layer of suitable fine-grained material should be laid to support the liner. However, if the supporting layer consists of low permeable material (e.g., clay), the synthetic liner must be placed on top of this layer.

 

(iv) Leachate and landfill gas management: The basic elements of the leachate collection system (i.e., drain pipes, drainage layers, collection pipes, sumps, etc.) must be installed immediately above the liner, before any waste is deposited. Particular care must also be taken to prevent the drain and collection pipes from settling. During landfill operations,

 

waste  cells  are  covered  with  soil  to  avoid  additional  contact  between  waste  and  the

 

environment. The soil layers have to be sufficiently permeable to allow downward leachate transport. Landfill gas is not extracted before completion, which includes construction of final cover, of the waste body. Extraction wells (diameter 0.3 to 1.0 m) may be constructed during

 

or after operation.

 

(v)     Landfill capping: Capping is required to control and minimise leachate generation (by

 

minimising water ingress into the landfill) and facilitate landfill gas control or collection (by installing a low permeability cap over the whole site). A cap may consist of natural (e.g., clay)  or synthetic  (e.g.,  poly-ethylene)  material with thickness  of at least 1 m. An uneven settlement  of the waste may be a major cause of cap failure.  Designs  for capping should, therefore, include consideration of  leachate  and  landfill  gas  collection  wells  or vents.  For the  cap  to  remain effective, it must be protected from  agricultural machinery, drying and cracking, plant root penetration, burrowing animals and erosion.


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