ABSTRACT
With increasing industrialization, technical development and economic growth, the quantity of waste that is produced has increased immensely. In addition, in developed countries the nature and composition of waste has evolved over the decades, reflecting changes in industrial and domestic practices. For example, in Britain domestic waste has changed significantly since the 1950s, from largely ashes and little putrescible content of relatively high density to low-density highly putrescible waste. Many types of waste material are produced by society of which domestic waste, commercial waste, industrial waste, mining waste and radioactive waste are probably the most notable. Over and above this, waste can be regarded as non-hazardous and hazardous. Waste may take the form of solids, sludges, liquids and gases or any combination thereof. Depending on the source of generation, some of these wastes may degrade into harmless products whereas others may be non-degradable and/or hazardous, thus posing health risks and environmental problems if not managed properly. A further problem is the fact that deposited waste can undergo changes through chemical reactions, resulting in dangerous substances being developed. Indeed, waste disposal is one of the most expensive environmental problems to deal with. Dealing with the waste problem is one of the fundamental tasks of environmental protection. As waste products differ considerably from one another, the storage facilities they require
also differ. Despite increased efforts at recycling wastes and avoiding their production, many different kinds of special wastes are produced that must be disposed of in special ways. Wastes that do not decompose within a reasonable time, mainly organic and hazardous wastes, and liquids that cannot be otherwise disposed of, ideally should be burnt. All the organic materials are removed during burning, converting them to less hazardous forms and leaving an inorganic residue. Solid unreactive immobile inorganic wastes can be disposed of at above-ground disposal sites. It is sometimes necessary to treat these wastes prior to disposal. In order to provide longterm isolation from the environment, highly toxic non-degradable wastes should be disposed of underground if they cannot be burnt. The best method of disposal is determined on the basis of the type and amount of waste on
the one hand, and the geological conditions of the waste disposal site on the other. In terms of locating a site, a desk study is undertaken initially. The primary task of the site exploration that follows is to determine the geological and hydrogeological conditions. Their evaluation provides the basis of models used to test the reaction of the system to engineering activities. Chemical analysis of groundwater, and at times mineralogical analysis of soils and rocks, may help yield information regarding the future development of the site. At the same time, the leaching capacity of the water is determined, which allows prediction of reactions between water, wastes, soil or rock. If groundwater must be protected, or highly mobile toxic and/or
very slowly degradable substances are present in wastes, then impermeable liners may be used to inhibit infiltration of leachate into the surrounding ground. In terms of waste disposal by landfill, a landfill is environmentally acceptable if it is correctly
engineered. Unfortunately, if it is not constructed to sufficiently high standards, a landfill may have an adverse impact on the environment. Surface water or groundwater pollution may result. Consequently, a physical separation between waste on the one hand and ground and surface water on the other, as well as an effective surface water diversion drainage system, is fundamental to design. The objectives of a landfill classification are to consider waste disposal situations in terms
of the type of waste, the amount of waste and the potential for water pollution. The different classes of landfill then can be used as a basis for the establishment of minimum requirements for site selection. Although no waste is completely non-hazardous, non-hazardous waste includes builders, garden, domestic, commercial and general dry industrial waste, which can be disposed of in a landfill. Nevertheless, some such landfills may produce significant amounts of leachate and so must incorporate leachate control systems. The size of a non-hazardous landfill operation depends on the daily rate of deposition of waste that, in turn, depends upon the size of population served. Hazardous waste has the potential, even in low concentrations to have a detrimental effect on public health and/or the environment because it may be, for instance, ignitable, corrosive or carcinogenic. In order to carry out a detailed assessment of an existing or potential waste disposal site,
a large volume of technical information and site-specific data are required (Sara, 1994). The technical information includes:
1 The interaction of wastes in the landfill, their degradation and leaching characteristics and how these change with time.
