The clean up operation
The contractor is currently excavating the waste tips, lagoons and hot spots. They are excavating the soils and processing them through remediation.
All of the materials in the soil go through a series of three screens that act like giant sieves.
The contractor ends up with three piles of debris: large debris, medium sized debris and small debris (this is the biggest pile).
People manually pick over the materials. As well as soil, there is rubber, wood, plastic, steel, etc. Large pieces are removed for recycling or processing. The remaining earth and soil has to be analysed for contamination.
Bioremediation
Bioremediation, using bugs and microorganisms to break down the pollutants, was used to clean less contaminated soil.
Thermal treatment
The most contaminated materials were processed through thermal desorption in a treatment plant which us probably the most visible aspect of the clean up operation. This thermal desorption plant cost €10 million to construct.
Contaminated soil is loaded into a large, rotating oven which gradually heats it up to 600 degrees C. The contaminants are then turned into gases which are collected and treated, leaving clean soil.
Cleaning up a heavily contaminated site is not always a logical linear process. Lots of processes happen at the same time on a site and a discovery may lead to a different way of working or a change in plan.
