The Choosing Of A Landfill Site Essay
- Просмотров 296
- Скачиваний 5
- Размер файла 20 Кб
The Choosing Of A Landfill Site Essay, Research Paper The Choosing of a Landfill Site There is currently much debate on the desirability of landfilling particular wastes, the practicability of alternatives such as waste minimisation or pre- treatment, the extent of waste pre-treatment required, and of the most appropriate landfilling strategies for the final residues. This debate is likely to stimulate significant developments in landfilling methods during the next decade. Current and proposed landfill techniques are described in this information sheet. Types of landfill Landfill techniques are dependent upon both the type of waste and the landfill management strategy. A commonly used classification of landfills, according to waste type only, is described below, together with a classification according to landfill strategy. The EU Draft Landfill Directive recognises three main types of landfill: Hazardous waste landfill Municipal waste landfill Inert waste landfill Similar categories are used in many other parts of the world. In practice, these categories are not clear-cut. The Draft Directive recognises variants, such as mono-disposal – where only a single waste type (which may or may not be hazardous) is deposited – and joint-disposal – where municipal and hazardous wastes may be co-deposited in order to gain benefit from municipal waste decomposition processes. The landfilling of hazardous wastes is a contentious issue and one on which there is not international consensus. Further complications arise from the difficulty of classifying wastes accurately, particularly the distinction between ‘hazardous’/'non-hazardous’ and of ensuring that ‘inert’ wastes are genuinely inert. In practice, many wastes described as ‘inert’ undergo degradation reactions similar to those of municipal solid waste (MSW), albeit at lower rates, with consequent environmental risks from gas and leachate. Alternatively, landfills can be categorised according to their management strategy. Four distinct strategies have evolved for the management of landfills (Hjelmar et al, 1995), their selection being dependent upon attitudes, economic factors, and geographical location, as well as the nature of the wastes. They are Total containment; Containment and collection of leachate; Controlled contaminant release and Unrestricted contaminant release. A) Total containment All movement of water into or out of the landfill is prevented. The wastes and hence their pollution potential will remain largely unchanged for a very long period. Total containment implies acceptance of an indefinite responsibility for the pollution risk, on behalf of future generations. This strategy is the most commonly used for nuclear wastes and hazardous wastes. It is also used in some countries for MSW and other non-hazardous but polluting wastes. B) Containment and collection of leachate Inflow of water is controlled but not prevented entirely, and leakage is minimised or prevented, by a low permeability basal liner and by removal of leachate. This is the most common strategy currently for MSW landfills in developed countries. The duration of a pollution risk is dependent on the rate of water flow through the wastes. Because it requires active leachate management there is currently much interest in accelerated leaching to shorten this timescale from what could be centuries to just a few decades. C) Controlled contaminant release The top cover and basal liner are designed and constructed to allow generation and leakage of leachate at a calculated, controlled rate. An environmental assessment is always necessary to that the impact of the emitted leachate is acceptable. No active leachate control measures are used. Such sites are only suitable in certain locations and for certain wastes. A typical example would be a landfill in a coastal location, receiving an inorganic waste such as bottom ash from MSW incineration.