The treatment of liquid or solid waste with high hydrocarbon content (over 15%) can be undertaken by recycling it in deballasting stations or by incineration in hazardous waste collection centres, cement works, or even, subject to specific derogation, in household waste incineration units.
Forgotten storage sites
During the Erika disaster, the French media highlighted the persistence of a few waste storage sites from previous oil spills. These were “definitive” storage facilities which had sunk into oblivion. In France, this previously used concept of definitive oil spill waste storage centres is no longer part of national contingency plans. All that is removed from intermediate storage sites must now be sent, after sorting into categories of materials:
• either directly to treatment plants accredited by the law in force (e.g. incineration of bird corpses)
• or, if this is not possible, to final storage sites from which point these products should then be treated.
Treatment is carried out at intermediate storage sites for certain products and after being sorted, is sent to specialised treatment plants for others. This treatment aims to recycle or destroy as much waste as possible and to transform the rest into ultimate waste in the strict sense of the legislation in force, i.e. all that cannot be recycled or destroyed. Ultimate waste is then sent to specialised storage centres.
Destruction of aquacultural produce
The experience of several recent oil spills highlighted the fact that the development of shoreline aquaculture has generated a new type of waste: tainted aquacultural produce which is destroyed due to a decision made in the name of consumer protection. The quantities at stake can be very high: nearly 9,000 tonnes of shellfish in the Aegean Sea accident in Spain (1992) and over 5,000 tonnes of salmon in the Braer accident in the Shetland Islands in Great Britain (1993).
Due to the lack of regulation, the disposal solutions put in place were specific to each case, from reuse as animal feed (for mink breeding, their flesh not being consumed by humans) to burying on landfill sites after lime treatment (www.ipieca.org).
Emulsion recovered at sea, only soiled by small quantities of solid waste, is a typical example of materials which can be recycled. Thick patties collected on the beach using shovels, with varying quantities of seaweed, sand and solid waste, can be recycled or incinerated.
Materials with low hydrocarbon content should undergo lime stabilisation in pits at intermediate storage sites, in power plants or on platforms. Building companies and public works then use the stabilised materials to build roads and embankments. However, this method is not exempt from criticism on the duration of stability obtained. Biological treatments (bioremediation and landfarming) are very effective but very long processes.
Ultimate waste, inert substances or substances presenting only slight traces of oil should be definitively stored in conditions whereby there is no risk of polluting surface or underground waters. This requires specially prepared sites and rigorous controls. The return of sand to the beaches where it came from is sometimes appealed for. This request is however generally dismissed, as it is practically impossible when an oil spill occurs, to treat the sand from each beach separately and even less conceivable to return sand from various origins to the relevant beaches.
Erika, Prestige: exceptional treatment plants
To ensure the final treatment of the 270,000 tonnes of soiled waste produced by the polluted shoreline clean-up in the wake of the Erika disaster, the Total group set up a pilot scheme and then a plant specially adapted to the treatment needs on the site of the Donges refinery (France). The development of techniques and the construction of the plant took 8 months, from September 2000 to April 2001. The plant functioned for 19 months, and was then dismantled. In Galicia, Spain, a similar but smaller plant treated the 70,000 tonnes of soiled waste produced by the Prestige pollution.
Treatment plant for waste from the Erika spill: sediment washing plant, May 2002, Loire-Atlantique (France)