Oil recovered at sea or arriving on the shoreline in the form of “chocolate
mousse” can contain up to 4 or 5 times its weight in water. This
mousse soils sediments, seaweed, plant debris and often solid
waste, which are then collected with the pollutant
in proportions of up to 20 times that of the oil. The pollutant and polluted materials recovered in response to an oil spill therefore end up representing far greater quantities than that of the spill.
The recovered pollutant and polluted materials are not all waste in the technical sense of the term: certain parts can be extracted and recycled. However, it is common to merge them all in the expression “oil spill waste”.
This waste can be in the form of liquids, pastes or solids. It can contain
highly variable quantities of oil and water. It can comprise solid objects
which make it unsuitable for pumping. Its transportation, storage and disposal
make use of very different solutions depending on their characteristics.
Storage facilities are necessary at all levels of the recovery chain. Primary storage for a period of a few hours to a few days is unavoidable on the recovery site or nearby, as an intermediate between the collection and evacuation chains.
Filling a skip with waste
It is generally accompanied by straining off liquids and pastes to avoid clogging up the pumps, using filter baskets placed over storage tanks. Emulsions which were not broken during pumping should be broken at this stage to avoid the storage of large quantities of water.
Intermediate storage facilities act as the link between evacuation and
treatment chains. They are sometimes located on the coast, other times on
the treatment site, and should be carefully prepared and made watertight
to avoid polluting the substrate
and ground water.
When the quantities in question surpass the treatment capacities of existing plants, a final storage site may be necessary to store waste until a specific treatment plant is built.
It takes a considerable amount of work to install, secure, manage, dismantle and restore these different storage facilities. They also require a complete control and transport chain.