Speeding up consolidation time

Sediment waste of mine processes (tailings) as well as dredged sediments are stored in dedicated deposits, or beneficially re-utilized to build new lands (e.g. Marker Wadden), to improve resilience of flood defences or enhance habitat restoration. However these sediment and-or waste is characterized by a very high fines content, and the accompanied very long consolidation times (e.g. the soil is very fluffy and not suitable for construction, and it takes a lot of time for the soil to gain strength). This results in inefficiencies of the reclamation process, deriving in very high operational costs.

Solid content evolution as a function of time for a tailings bed, as well as for two tailings bed treated with worms. The increase in Sc is 100% larger than in the absence of treatment. The dewatering process is also faster, achieving equilibrium weeks – months before equilibrium in the absence of treatment.

The ability to speed up the consolidation time of these deposits is crucial for the future of reclamation of mining areas and reclamation and flood protection projects with dredged sediment. The techniques being currently used by the industry are very high in costs and not very efficient in increasing the soil strength within a competitive time scale, and thus there is room for improvement and for seeking new competitive and efficient technologies.

Moving away from chemicals and energy loss

The solution makes it possible to move away from the usage of chemicals and-or the consumption of large amounts of energies (and the associated carbon emissions) and to rely on natural processes to enhance dewatering and compaction of sediment waste. This technology has been proven not only to be environmentally friendly and consistent with current societal concerns, but also proofs to be a sound technical solution (so far demonstrated at small to mid scales).

Innovative idea

The idea of using Oligochaete worms to compact the sediment faster originated from our experts coming from many disciplines: ecology, biologie, engineering, soil sciences and geotechnics. Our experimental facilities, in particular the sediment lab, were a key to provide a proof of concept for this technology, as well as to test and quantify subsequent improvements.

Close-up of the water-bed interface at a treated bed. The worms travel up and down the bed seeking for sustenance, and leaving a network of tunnels throughout the bed. These tunnels favour dewatering, and improve reclamation time to a relevant extent.

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