Study will predict the impact of changing landfill practice on leachate quality

The Environment Agency has commissioned the second phase of a consultancy project to predict the impact of changing landfill practice on leachate quality in the UK, as progressive implementation of the Landfill Directive (1999/31/EC) changes the nature of waste inputs. The Agency will require data to use as a source term to help it assess applications for new landfills and extensions to existing landfill sites

The project has been undertaken within the Environment Agency's Waste Regulation and Management Research Programme. The study is being carried out jointly by Enviros Aspinwall and Knox Associates. The waste industry as a whole will need source term data to assess implications for landfill design features, including leachate collection and treatment, leachate-liner interactions, leak detection and risk assessment.

Two-phased approach
The study is being undertaken in two phases. Phase 1 has involved a review of existing data, both from published literature and from operating landfills, within other parts of the EU. Data have been collected from appropriate sites in the EU. Phase 2 will now involve laboratory scale experiments and field sampling, designed to validate and extend the predictions made in Phase 1. The types of waste that may be expected to lead to significant changes in leachate quality might include:

  • biologically pre-treated household waste
  • treated hazardous wastes
  • bottom ash and APC residues from waste incineration
  • residues from waste recycling activities

Phase 1
Data in Phase 1 were obtained by literature search, and by identifying suitable examples of sites, through contact with specialists and operators in other EU states, that have suitable landfill monitoring data available. In addition to leachate quality data, supporting information has been obtained for each landfill, to assist interpretation in the UK context.

This includes information on gas generation and gas quality, to assess the level of biological activity (this is currently an important unknown, eg for sites receiving mixed hazardous wastes); relative wetness of the site, to assess the extent to which leachate strength has been affected by dilution; waste input data, details of any waste acceptance test used, eg the German DIN test (this will be relevant to the practical work undertaken in Phase 2), impacts on wastes stabilisation and effects on landfill design, eg leachate collection and liner systems. It is expected that few EU landfills will be able to provide results for all of the 56 List I organic Pollution Inventory substances that will soon have to be reported by landfill operators in the UK, for discharges to sewer or surface water, or for the List I substance groups cited in the Groundwater Directive (80/68/EEC). Leachate samples will therefore be obtained from selected landfills within each category, for supplementary analysis to be undertaken, during Phase 2.

Phase 2
Phase 2 has begun, and includes analysis of leachates from selected EU landfills, for trace organic compounds. The detailed programme for the remaining experimental work in Phase 2 of the study has been designed on the basis of the results of Phase 1. It is likely to focus on MBP wastes and MSW incinerator residues, involving leaching tests on samples of real wastes from pre-treatment processes currently operating in the UK. These results will be compared with leaching test results from waste inputs to the full-scale operating EU landfills that provided data for Phase 1, and will provide a basis for assessing the validity of the leachate quality data from Phase 1, to future landfills in the UK.

The study began on 8 January 2001 and Phase 1 is due to be completed by April 2002. Phase 2 will be completed during the summer of 2002, with estimated publication later in the year, as R&D Project Number P1-494.

If any readers have access to data that they feel could contribute to the objectives of the study, they are invited to contact either Howard Robinson, at or Keith Knox at



Waste & resource management

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