- This article is about a widely used strategy for solid waste disposal.
- For the disposal of liquid wastes, and sewage in particular, see Water treatment.
- For the practice of creating new land from sea- or riverbeds, see Land reclamation.
A landfill, also known as a dump or tip (and historically as a midden), is a site for the disposal of waste materials by burial and is the oldest form of waste treatment. Historically, landfills have been the most common methods of organized waste disposal and remain so in many places around the world.
Landfills may include internal waste disposal sites (where a producer of waste carries out their own waste disposal at the place of production) as well as sites used by many producers. Many landfills are also used for other waste management purposes, such as the temporary storage, consolidation and transfer, or processing of waste material (sorting, treatment, or recycling).
A landfill also may refer to ground that has been filled in with soil and rocks instead of waste materials, so that it can be used for a specific purpose, such as for building houses. Unless they are stabilized, these areas may experience severe shaking or liquefaction of the ground in a large earthquake.
Types & construction methods
Most modern landfills are classified according to the type(s) of waste material disposed of into them. Landfills can be engineered to a high standard in order to contain liquid leachate or landfill gas produced by decomposing organic waste. Modern landfills generally require a minimum of one landfill liner, consisting of a layer of compacted clay with a minimum required thickness and a maximum allowable hydraulic conductivity. Others also require the addition of one or more layers of impermeable membrane, such as high-density polyethylene (HDPE) together with geotextile. Various final cover systems are used to 'cap' landfills (such as clay or topsoil), depending on the type of wastes present within the landfill. Landfills, based on the waste type that is disposed within them, may be classified as:
- Hazardous waste landfill: waste disposal units constructed to specific design criteria and which receive wastes meeting the local definition of hazardous waste. These landfills are generally constructed to be secure repositories for material that presents a serious hazard to human health, such as high-level radioactive waste. They are restricted, by permit or law, to the types of waste that they may handle (chemical vs. radioactive, liquid vs. dry). Double liner systems are the norm for hazardous waste landfills. Deep geological repository of high level radioactive waste is not generally classified as landfilling.
- Sanitary landfills: also called modern, engineered or secure landfills, these usually have physical barriers such as liners and leachate collection systems, and procedures to protect the public from exposure to the disposed wastes. The term sanitary landfill normally refers to those where municipal solid waste is disposed of, as well as other wastes high in organic material. In some countries, all landfills are sanitary landfills.
- Inert waste landfill: waste disposal units that receive wastes which are chemically and physically stable and do not undergo decomposition, such as sand, bricks, concrete or gravel.
- Dumps: also simply called landfills, dumps are landfills that are not engineered with the special protective measures required by sanitary landfills. They are most common in rural, remote, and developing areas. Many jurisdictions prohibit the use of non-sanitary landfills for the disposal of municipal solid waste. Other jurisdictions that do allow dumps may require them to be constructed according to some engineering standard to mitigate the risk for environmental contamination, such as by limiting the slope, requiring compaction, or ensuring that the cell is high enough above the groundwater table.
Subsystems
A typical landfill consists of subsystems such
as the:
- Landfill liner
- Leachate collection and management system
- Landfill gas management system
- Landfill gas monitoring & leachate monitoring systems
- Road network
- Drainage system
- Final landfill cap
Their function is to secure the normal landfill operations and to control the anticipated emissions generated mainly by the decomposition of organic matter, such as leachate and landfill gas.
Site construction requirements
The construction of a landfill requires a staged approach. Landfill designers are primarily concerned with the viability of a site. To be commercially and environmentally viable a landfill must be constructed in accord with specific requirements, which are related to:
- Location
- Easy access to transport by road
- Transfer stations if rail network is preferred
- Land value
- Cost of meeting government requirements, such as the Environment Agency in England and Wales
- Location of community served
- Type of construction (more than one may be used at single site)
- Pit - filling existing holes in the ground, typically left behind by mining
- Canyon - filling in naturally occurring valleys or canyons
- Mound - piling the waste up above the ground
- Stability
- Underlying geology
- Nearby earthquake faults
- Water table
- Location of nearby rivers, streams, and flood plains
- Capacity The available voidspace must be calculated by comparison of the landform with a proposed restoration profile.
This calulation of capacity is based on,- Density of the wastes
- Amount of intermediate and daily cover
- Amount of settlement that the waste will undergo following tipping
- Thickness of capping
- Construction of lining and drainage layers.
- Protection of soil and water through:
- Installation of liner and collection systems.
- Storm water control
- Leachate management.
- Landfill gas management.
- Nuisances and hazards management.
- Costs
- Feasiability studies
- Site after care
- Site investigations (costs involved make small sites uneconomic).
Operations
Typically, in non hazardous waste landfills, in order to meet predefined specifications, techniques are applied by which the wastes are:
- Confined to as small an area as possible.
- Compacted to reduce their volume.
- Covered (usually daily) with layers of soil.
During landfill operations the waste collection vehicles are weighed at a weigh-bridge on arrival and their load is inspected for wastes that do not accord with the landfill’s waste acceptance criteria. Afterwards, the waste collection vehicles use the existing road network on their way to the tipping face or working front where they unload their load. After loads are deposited, compactors or dozers are used to spread and compact the waste on the working face. Before leaving the landfill boundaries, the waste collection vehicles pass through the wheel cleaning facility. If necessary, they return to weighbridge in order to be weighed without their load. Through the weighing process, the daily incoming waste tonnage can be calculated and listed in databases. In addition to trucks, some landfills may be equipped to handle railroad containers. The use of 'rail-haul' permits landfills to be located at more remote sites, without the problems associated with many truck trips.
Typically, in the working face, the compacted waste is covered with soil daily. Alternative waste cover materials are several sprayed on foam products and temporary blankets. Blankets can be lifted into place with tracked excavators and then removed the following day prior to waste placement. Chipped wood and chemically 'fixed' bio-solids, may also be used as an alternate daily cover. The space that is occupied daily by the compacted waste and the cover material is called daily cell. Waste compaction is critical to extending the landfill life. Factors such as waste compressibility, waste layer thickness and the number of passes of the compactor over the waste affect the waste densities.
Land reclamation
As human overcrowding of developed areas intensified during the 20th century, it has become important to develop land re-use strategies for completed landfills. Some of the most common usages are for parks, golf courses and other sports fields. Increasingly, however, office buildings and industrial uses are made of a completed landfill. In these latter uses, methane capture is customarily carried out to minimize explosive hazard within the building.
An example of a Class A office building constructed over a landfill is the Dakin Building at Sierra Point, Brisbane, California. The underlying fill was deposited from 1965 to 1985, mostly consisting of construction debris from San Francisco and some municipal wastes. Aerial photographs prior to 1965 show this area to be tidelands of the San Francisco Bay. A clay cap was constructed over the debris prior to building approval.[1]
Another strategy for landfill reclamation is the incineration of landfill trash at high temperature via the plasma-arc gasification process, which is currently used at two facilities in Japan, and will be used at a planned facility in St. Lucie County, Florida.[2]
Impacts
A number of adverse impacts occur from landfill operations. These impacts can vary: fatal accidents (e.g., scavengers buried under waste piles), infrastructure damage (e.g., damage to access roads by heavy vehicles), pollution of the local environment (such as contamination of groundwater and/or aquifers by leakage and residual soil contamination after landfill closure), offgassing of methane generated by decaying organic wastes; harbouring of disease vectors such as rats and flies, particularly from improperly operated landfills, which are common in Third-world countries, injuries to wildlife[3] and simple nuisance problems (e.g., dust, odour, vermin, or noise pollution). The presence of landfills can also cause local Samirol populations to rise.
Environmental noise and dust are generated from vehicles accessing a landfill as well as from working face operations. These impacts are best to intercept at the planning stage where access routes and landfill geometrics can be used to mitigate such issues. Vector control is also important, but can be managed reasonably well with the daily cover protocols.
Most modern landfills are operated with controls to manage problems such as these. Analysis of common landfill operational problems are available in [1].
Some local authorities have found it difficult to locate new landfills. These authorities may charge a fee or levy in order to discourage waste and/or recover the costs of site operations. Some landfills are operated for profit as commercial businesses. Many landfills, however, are publicly operated and funded.
Regional practice
United Kingdom
Landfilling practices in the UK have had to change in recent years to meet the challenges of the European Landfill Directive. The UK now imposes landfill tax upon biodegradable waste which is landfilled. In addition to this the Landfill Allowance Trading Scheme has been established for local authorities to trade landfill quotas.
United States
In the U.S., landfills are regulated by the state's environmental agency that establishes minimum guidelines; however, none of these standards may fall below those set by the United States Environmental Protection Agency.
The Fresno Municipal Sanitary Landfill, opened in Fresno, California in 1937, is considered to have been the first modern, sanitary landfill in the United States, innovating the techniques of trenching, compacting, and the daily covering of waste with soil. It has been designated a National Historic Landmark, underlining the significance of waste disposal in urban society.
Before the advent of modern landfills in America, most Americans lived in sparsely populated rural farming communities and most burned their garbage. Due to environmental and safety concerns, burning garbage by civilians has been outlawed by most municipalities and can only be performed by landfill managers or people who have obtained permits from the municipality. More information on landfill history in the United States can be found at [2].
The Resource Conservation and Recovery Act is a US federal law that is designed to protect the public from harm caused by waste disposal.
U.S. landfills consist of 40% to 50% paper waste, 20% to 30% construction debris, and 1.2% disposable diapers. [4]
Alternatives
The obvious alternative to landfills are waste reduction and recycling strategies. Secondary to not creating waste, there are various alternatives to landfills. In the late 20th century, alternative methods to waste disposal to landfill and incineration have begun to gain acceptance. Anaerobic digestion, composting, mechanical biological treatment, pyrolysis and gasification have all began to establish themselves in the market.
In recent years, some countries, such as Germany, Austria, and Switzerland, have banned the disposal of untreated waste in landfills. In these countries, only the ashes from incineration or the stabilised output of mechanical biological treatment plants may still be deposited.
See also
- Bioreactor landfill
- Daily cover
- Hydrologic Evaluation of Landfill Performance or HELP model
- Landfill gas monitoring
- Landfill mining and reclamation
- Landfill tax
- List of solid waste treatment technologies
- Mechanical biological treatment
- Midden
- Solid Waste Association of North America
- Tel - an ancient waste disposal method, in one respect the opposite of a landfill
- Waste management
Notes
- ^ Paul B. Awosika and Marc Papineau, Phase One Environmental Site Assessment, 7000 Marina Boulevard, Brisbane, California, prepared for Argentum International by Certified.Engineering & Testing Company, Boston, Massachusetts, July 15, 1993
- ^ http://www.usatoday.com/news/nation/2006-09-09-fla-county-trash_x.htm
- ^ Wildlife Injuries Noyes, K (2006) Clean-Up Your Trash, Charity Guide
- ^ National Geographic magazine, September 1993
References
- "Council Directive 1999/31/EC of [[26 April]] [[1999]], on the landfill of waste" (PDF).
{{cite web}}: URL–wikilink conflict (help); Unknown parameter|accessmonthday=ignored (help); Unknown parameter|accessyear=ignored (|access-date=suggested) (help) - "The Landfill Operation Management Advisor Web Based Expert System".
{{cite web}}: Unknown parameter|accessmonthday=ignored (help); Unknown parameter|accessyear=ignored (|access-date=suggested) (help) - H. Lanier Hickman Jr. and Richard W. Eldredge. "Part 3: The Sanitary Landfill". A Brief History of Solid Waste Management in the US During the Last 50 Years.
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