An innovative system that will enable the real-time monitoring of the movement of landfill leachate has been developed by the British Geological Survey (BGS). The project to design and build the system was made possible by a grant of £261,704 awarded by The Veolia Environmental Trust through the waste awareness category of the Landfill Communities Fund.

Work on the project began in 2003. The BGS objective was to develop a non-invasive 4D electrical imaging system using the automated time-lapse electrical resistivity tomography (ALERT) concept to allow a user to view near real-time images of fluid flow or hydrochemical changes in landfills. ALERT would enable the user to see how leachate was being generated and distributed within a landfill, monitor its movement, and take action if there were signs of any leachate flow-paths off-site.

The system developed collects data using an array of electrodes located on the surface of the landfill and in boreholes. The data is modelled and converted into a tomogram, which can be visualised as an animated digital image of leachate movement. The system’s development was carried out in five work packages, dealing with instrumentation and sensors, data processing and management schemes, modelling algorithms, and experimental validation of the ALERT concept.

An automated measurement system was developed to capture, process, store and model the data in a seamless manner with no manual intervention. Permanently installed electrode arrays and instrumentation allow imaging on demand from the office, using wireless telemetry. Data processing and modelling algorithms were devised to enable the data obtained from the electrodes to be turned into tomograms. A customised data management system, based on a relational database, was developed using dedicated IT infrastructure.

The project also set out to obtain experimental proof of the new 4D monitoring concept. The system was tested on a purpose-built field-scale test facility rather than a full-scale landfill as this would have been costly and resource intensive. This controlled test facility was used for a range of hydraulic experiments emulating the movement and behaviour of liquids in a waste mass. These included the periodic variation of liquid levels, and the movement of conductive saline tracer fluids in water-saturated sand, brought about by gravity and imposed hydraulic-gradients.

All experiments were monitored automatically with the ALERT system. When the geophysical results were compared with ground-truth data, obtained from observation wells to show what was actually happening within the waste mass, it was concluded that the BGS system could accurately image and track liquid levels and movements.

Dr Richard Ogilvy, manager of the electrical tomography programme at BGS and who led the project, says: “This new technology provides a technical capability that was not available when the project started, and represents a significant advance in landfill monitoring technology.

“We believe that the technology has strong commercial potential, and it is anticipated that it will be offered to the waste management industry as a service or under licence. The obvious next step is to demonstrate the technology at a commercial landfill site under realistic conditions.”

Research geophysicist Dr Oliver Kuras, who was the principal investigator, adds: “A permanently instrumented or smart landfill could be a reality in one to two years’ time if the demonstration studies prove the practicalities and cost-benefit of ALERT. This technology has the potential to revolutionise waste management and monitoring practice.”

Veolia Environmental Trust

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