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Engineering

Research project: Leachate recirculation and collection systems

Currently Active: 
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Environment Agency sponsored research sets out framework for recirculating leachate in landfills, and research into clogging of collection systems leads to recommendations for fundamental changes to the operational practice of landfills

Project Overview

Conceptual diagram of recirculation

Leachate recirculation

Leachate recirculation in landfills has been in widespread use since the 1970s for a range of purposes that include leachate management, enhanced landfill gas generation /recovery and to improve the sustainability of landfills.  However, leachate recirculation has the potential to cause problems such as surface seeps, high leachate levels and reduced landfill stability, and must be used appropriately.

The research was commissioned by the Environment Agency and investigated the key technical, environmental and operational issues for all applications of leachate recirculation. The research included a survey of practice and experience in the UK and resulted in a comprehensive technical review and guidance (see publications).

Further theoretical and practical research into leachate recirculation has resulted in the development of numerical models to simulate and help design leachate recirculation systems.

Tyre bale leachate collection layer

Clogging of leachate collection layers

Pilot scale tests were carried out to investigate the clogging of shredded and baled tyres in comparison with aggregates when percolated by leachates representative of those generated by methanogenic stage landfills.

Realistic lifetime loading rates of methanogenic leachate were applied, and clogging was not generally apparent in any of the drainage media studied. This is in apparent contrast to many other studies that have demonstrated the susceptibility of all forms of drainage media to biological and chemical clogging when percolated with high strength organic and calcium rich leachates.

...to allow a buffering layer of methanogenic leachate
Leachate collection base design

The research identified the reasons for these differences and concluded that clogging of drainage systems could be minimised in many cases if the drainage layer was buffered from high strength leachate by maintaining methanogenic leachate not only within the drainage layer but also within a buffer zone in the bottom layer of waste. This would require a major change to landfill design and operational practice as current regulations tend to require that drainage layers are kept fully drained.

Related research groups

Infrastructure Group
Waste Management
provides storage and helps balance flows to treatment or recirculation facilities
Leachate Lagoon
Leachate irrigation pipe
biological and chemical clogging tests
Leachate drainage media test
...compressed and ready for testing
Tyre shred...
Clogging of gravel tested

Publications

Key Publications

Articles

Conferences

Staff

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