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

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 howard.robinson@enviros.com

or Keith Knox at kk@knoxuk.demon.co.uk