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Landfill DisposalMost municipal solid waste in South Africa is disposed of in landfill sites. Durban currently has 3 fully permitted landfill sites:
As the water passes through the landfill, it picks up soluble portions of the decomposing waste. When the leachate leaves the landfill, it may contaminate either groundwater or surface water, thus acting as a vehicle for carrying potentially toxic materials from the landfill to water sources used for human activities. Municipal landfills are now constructed with the potential for ground water pollution in mind. This includes provision for liners at the bottom of the landfill to help prevent leachate seepage, capture and treatment of the leachate before it leaves the site, as well as consideration of the geological location of the landfill and its proximity to ground and surface waters. There are also regulations for the types of waste which are allowed to enter municipal solid waste landfills. Special facilities are required for the safe disposal of hazardous waste, and various regulations governing the manufacture and transport as well as disposal of hazardous materials are designed in part to prevent their illegal disposal in municipal landfills. Household hazardous waste is also gaining increasing attention. A number of US communities have initiated programmes for disposal of certain household items which have been deemed to be a problem in municipal landfills. Waste oil is a frequent target, but many other household items such as paints, solvents, batteries, and insecticides are included in some programmes. LANDFILL CONSTRUCTION Waste is placed on the ground or liner, spread in layers, and driven over with a special dozer called a landfill compactor. A thin cover of soil is used at the end of each day to stop rats or flies reaching it and prevent the waste blowing about and to reduce the odour nuisance. When the landfill site is full it is covered with a thick layer of soil and allowed to settle. Eventually the rehabilitated land can be used for farming, forestry or recreation. Landfill sites, however, are rarely sufficiently stable for building on. Once a landfill has reached capacity, it must be properly closed and maintained for a number of years. DSW is embarking on the rehabilitation of the front stability berm and wetland area of the Bisasar Road Landfill site. Indigenous trees, shrubs, ground cover and wild grasses will be planted to blend in naturally with the surrounding vegetation to re-establish natural vegetation. As sections of the site are completed, they too will be rehabilitated DECOMPOSITION OF WASTE After a landfill is closed, decomposition of the waste continues with some physical and chemical changes. The final depth of the landfill may be as much as 30 percent less than the original. It is estimated that 90 percent of the settlement will occur in the first five years after filling takes place. Bacterial activity also occurs in the landfill. This benefits with aerobic decomposition of the waste, with carbon dioxide, water and nitrates as the primary products. When the oxygen supply is depleted, the bacterial activity changes. Now anaerobic micro-organisms produce volatile fatty acids and carbon dioxide. Later, methane-producing bacteria reduce the volatile acids mainly to methane and carbon dioxide, as this rather foul smelling gas is commonly known as landfill gas. The rate of decomposition depends on a variety of factors including moisture, temperature, pH, and permeability of the soil cover. The entire process may take decades to complete. GAS FROM LANDFILLS Landfill gas comprises mainly methane and carbon dioxide. Not only is methane a cause for concern because of its significant contribution to the greenhouse effect but also because of its explosive nature when mixed with oxygen at certain concentrations. Methane nevertheless can also provide a valuable source of alternative energy if the landfill is set up to collect it. Recently DSW discovered the lateral migration of landfill gas from the Bisasar Road landfill site into the weighbridge and office complex. A gas curtain has since been installed whereby a series of wells were sunk into the refuse from which gas is actively pumped from the area and flared. Flaring landfill gas converts the methane component to carbon dioxide and water vapour. As an alternative source of energy it can be used to generate electricity, fire incinerators and boilers and kilns to make bricks. It should be noted that methane generation is not limited to landfills; swamps produce large quantities of methane where it is known as "swamp gas", and it is also produced in volume by volcanoes, cows, rice paddies and termites. In addition to methane and carbon dioxide, minor amounts of 80 other gases including nitrogen, oxygen, hydrogen, hydrogen sulphide, and carbon monoxide have been identified in landfill gas. BISASAR ROAD LANDFILL SITE Location and description of Site This site is DSW's flagship landfill site. It is situated in the Springfield district in the Central Region, favourably placed with respect to the CBD and close to the Outer Ring Road, a major artery connecting the city to the west, north and south. It is conveniently close to the DSW head office. The site is surrounded by both formal and informal residential housing, industries and open space. The site is positioned in an unstable valley line which was deemed unsuitable for residential use. The site was opened for operation in May 1980. It was issued with a permit by the Department of Water Affairs and Forestry in 1996 and is classified as a General Large Site (G:L:B+). Access to the site is via Dhulam Road, access is controlled and the entire site is fenced. Three 60-ton weighbridges have been installed. All waste coming onto site is recorded by means of software developed in-house. Tariffs are charged for all waste, other than that which is suitable for cover material (see Tariff Codes 501 onwards) Operation of the site The site is operated by DSW staff falling under the Plant and Disposal Branch. A Monitoring Committee consisting of Local, Provincial and State Government officials, I & APs and members of the public meets on a regular basis. The objective of this committee is to ensure that the standards set out in the Permit are adhered to and that the site is run to acceptable norms and standards. Click here for copy of the Permit. The permit is in PDF format and can be read using Adobe Acrobat Reader. The file is fairly large and may take some minutes to download. Regular Monitoring Committee meetings are held. Minutes of the meetings can be obtained by clicking below. The minutes are in PDF format and can be read using Adobe Acrobat Reader. Minutes of 25 January 2001 Minutes of 15 November 2001 Minutes of 9 May 2002 Minutes of 25 July 2002 Minutes of 17 October 2002 Minutes of 7 November 2002 Minutes of 23 January 2003 Minutes of 14 May 2003 Minutes of 11 June 2003 Minutes of 15 July 2003 Minutes of 28 August 2003 Current Available Air Space The remaining air space as at June 2002 was estimated at 10.5 million cubic metres. Estimated remaining life span, taking into account normal growth, is 15 years. Closure is planned for June 2017. LA MERCY LANDFILL SITE Location and description of Site The La Mercy Landfill site is situated in farmlands (sugar cane fields), in the Northern Region, north and approximately 1,5 kilometres from La Mercy. The proposed Shaka International Airport lies within a kilometre west of the site. The site is surrounded by sugar cane fields. The property on which the site is located is owned by the Tongaat-Hulett group. The site which started operating in 1993 was issued with a permit for waste disposal in that year. The classification of the landfill site is G:M:B+ Class 2. Access to the site is via a relatively long district gravel road. Access is controlled and the entire site is enclosed with security fencing and lockable gates. Current Available Air Space The remaining air space as at June 2002 was estimated at 65 000 cubic metres. There is a possibility of increasing this figure to 120 000 cubic metres should the development of the Buffelsdraai regional landfill site is further delayed. Closure is planned for June 2004 Further Remarks Daily cover material is being generated on site and from outside sources such as builder's rubble and excavation deposits. The site is well obscured and surrounded by sugar cane fields. MARIANNHILL LANDFILL SITE Location and description of Site The Mariannhill landfill site is situated in Mariannhill in the Inner West Region. Residential areas, forestry and open space surround the site which has been in operation since July 1997. The classification of the site is G:L:B:+. Access is controlled and the entire site is enclosed with security fencing and lockable gates. Incoming waste is regulated and recorded by a system of weighbridges. Operation of the site The site is operated by DSW staff falling under the Plant and Disposal Branch. A Monitoring Committee consisting of Local, Provincial and State Government officials, I & APs and members of the public meets on a regular basis. The objective of this committee is to ensure that the standards set out in the Permit are adhered to and that the site is run to acceptable norms and standards. Click here for copy of the Permit and Amendment. The permit is in PDF format and can be read using Adobe Acrobat Reader. The file is fairly large and may take some minutes to download. Regular Monitoring Committee meetings are held. Minutes of the meetings can be obtained by clicking below. The minutes are in PDF format and can be read using Adobe Acrobat Reader. Minutes of 30 May 2002 Minutes of 21 November 2002 Minutes of 30 January 2003 Minutes of 27 March 2003 Minutes of 13 August 2003 Current Available Air Space The remaining air space as at June 2002 was estimated at 3.8million cubic metres. |
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