The Choosing Of A Landfill Site

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. Th...

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...eatment, and the most appropriate methods, are site-specific. The timescale required for active leachate management is dependent on the rate at which pollutants are flushed from the landfill. With conventional low- permeability top covers and containment strategies, it is likely that the timescale will be several centuries, for wastes with a high pollution potential, such as MSW.

There is currently a great deal of interest in shortening this period by high- rate recirculation and partial treatment. As yet, these accelerated flushing techniques have not been proven at full-scale. Until they are, or until waste minimisation and pre-treatment reduce the pollution potential of the wastes that are landfilled, the long time-scales for pollution control arising from current landfill techniques will remain.

References:

1.Hjelmar O, Johannessen LM, Knox K & Ehrig HJ, Composition and management of leachate from landfills the EU. To be presented at 5th International Landfill Symposium, Sardinia,

October 1995

[return to text] within 2.Dept of the Environment, A review of water balance methods and their application to landfill in the UK, UK

Dept of the Environment Report No. CWM 031/91.