Landfills include any site which is used for more than a year for the temporary storage of waste; and, any internal waste disposal site, that is to say a site where a producer of waste is carrying out its own waste disposal at the place of production.
Landfills does not include (a) any facility where waste is unloaded in order to permit its preparation for further transport for recovery, treatment or disposal elsewhere; (b) any site where waste is stored as a general rule for a period of less than three years prior to recovery or treatment; or, (c) any site where waste is stored for a period of less than one year prior to disposal.
MSW landfills represent the most widely accepted option for waste disposal in many parts of the world, particularly in underdeveloped and developing countries, due to its economic advantage over other methods.
Even highly developed countries also largely depend on landfilling. In USA, 54% of the 250 × 106 metric tons of MSW generated was landfilled in 2008, with recycling and composting accounting for about 33% of MSW management .
WASTE DECOMPOSITION PROCESS IN LANDFILL
LANDFILL GAS RECOVERY
Advantages of Landfill Gas Recovery
Disadvantages of Landfill Gas Recovery
Steps in Landfill Reclamation
(i) Excavation: An excavator removes the contents of the landfill cell. A front-end loader then organizes the excavated materials into manageable stockpiles and separates out bulky material, such as appliances and lengths of steel cable.
(ii) Soil Separation (Screening): A trommel (i.e., a revolving cylindrical sieve) or vibrating screens separates soil (including the cover material) from solid waste in the excavated material. The size and type of screen used depends on the end use of the recovered material. For example, if the reclaimed soil typically is used as landfill cover, a 2.5-inch screen is used for separation. If, however, the reclaimed soil is sold as construction fill, or for another end use requiring fill material with a high fraction of soil content, a smaller mesh screen is used to remove small pieces of metal, plastic, glass, and paper. Trommel screens are more effective than vibrating screens for basic landfill reclamation. Vibrating screens, however, are smaller, easier to set up, and more mobile .
Benefits of Landfill Reclamation
Drawbacks of Landfill Reclamation
MANAGEMENT OF CLOSED LANDFILLS
Aftercare management of closed landfills typically includes monitoring of emissions (e.g. leachate and gas) and receiving systems (e.g. groundwater, surface water, soil, and air) and maintenance of the cover and leachate and gas collection systems .
Landfill Gas: Closed landfill sites pose a potential hazard because of their methane production. The greatest risk occurs at sites that are within 250 m of housing and/or industrial estates. Problems become more severe when there are no gas-control measures .
Landfill leachates: Landfill leachates are defined as the aqueous effluent generated as a consequence of rainwater percolation through wastes, biochemical processes in waste’s cells and the inherent water content of wastes themselves. It contains many organic matters, minerals, heavy metals and has high concentration of ammonia-nitrogen, all these lead to the low biodegradability. The leachate qualities changes according to the landfill climate conditions and hydrology, it also varies according to the qualities of the garbage that has been buried in the landfill . The removal of organic material based on chemical oxygen demand (COD), biological oxygen demand (BOD) and ammonium from leachate is the usual prerequisite before discharging the leachates into natural waters. Conventional landfill leachate treatments can be classified into three major groups :
(a) leachate transfer: recycling and combined treatment with domestic sewage,
(b) biodegradation: aerobic and anaerobic processes and
(c) chemical and physical methods: chemical oxidation, adsorption, chemical precipitation, coagulation/flocculation, sedimentation/flotation and air stripping. After the hardening of the standards of rejection, conventional landfill leachate treatment plants are not able to meet the desired standards. Today, the landfill leachate treatment consists of various combined processes such as coagulation and ammonia-nitrogen stripping, UBF anaerobic process and two stages of Anoxic/Oxic process filter, UF and RO deep treatment .
Landfill mining: Landfill mining could be described as a process for extracting minerals or other solid natural resources from waste materials that previously have been disposed of by burying them in the ground .