Filter Disks (English)
Médias filtrants (Français)
What is it?
Repérésdepuis 2007 on the beaches of the Basque-Landes, these plastic wheels have long been an enigma. Finally identified by the antenna Corsica Surfrider Foundation Europe on the cover of a brochure of the company Vinci, we now know that this is "media filter" used in the treatment of wastewater in lesstations of municipal treatment plants in the food industry (etboissons wines, canned fish and meat ...), on some ships decroisière.
How does it work?
In unestation purification, wastewater undergo several treatments depurification: screening (transition to work-to grids to retain lesgros residues), settling (to rest for the heavy materials tombentau background). In the final phase, we add dansl'eau waste-eating bacteria. In the early 2000s, researchers have found that by introducing norvégiensse support in water, bacteria sefixent top and become much more effective.
These are médiasfiltrants media for bacteria, introduced in large quantities (50% of the volume of water, several sieurscentaines of thousands and in some cases, millions) in basins of treatment plants. With the flow of water or the introduction of air, ilsbougent tenfold in a disorderly manner and the efficiency of bacteria.
How do they get to the beaches?
According nosconnaissances present, there are two possible sources of pollution:
1. Three-time Lesaccidents aumoins have been referenced in recent months: In fall 2009, in Guipuzcoa (Basque Country), escape desMille parts of a company (a factory papierprobablement) situated on the river Oria. The filter media rejoignentl'océan year Orio. They are identified by the local surfers and gestionnairesde water. The press published several articles and the mayor of San Sebastian déplore publicly pollution. The offending company has not identified étéofficiellement. On 11 February 2010, Evry, 500 to 800m3 (or millions) of escape from the filter media stationd'épuration and join the Seine. Soon, they are marked with a barge leshabitants that alert the River Police in Paris. The pollueurrepéré admitted the facts. The Robin Hood Association filed a complaint against pollution Xpour aquatic resources. March 7, they have found àBardouville downstream of Rouen in the Regional Natural Park of loops laSeine Norman to 310km from the place of the accident. The di-inning April 25, we lesramasse on the beach of Honfleur. The filter media rejointl'océan Parisians! Mi February 2010, Galicia, sinners anguillesremontent of large amounts of filter media in their net lefleuve Miño on the border between Spain and Portugal. Dureplusieurs pollution days. Local police investigated but did not discover the source.
2. Lesfuites regular
Nouspouvons make several assumptions: - lesmédias filter are used in open ponds overflowing in case of heavy rainfall. - Some manufacturers claim that "suffitd'ajouter filter media" without further modification in unestation to make it more effective. Would there be maladaptive stations at once? : Output grids retained the meshes too wide for example. This remains the assumptions, maisune thing is certain, the three accidents referenced do not explain seulsla impressive amount of filter media found on all the beaches of the Atlantic coast in France and Spain for 3 years. So there are other leaks to be identified.
Filter Disks in the United States
In March 2011 between 4 million and 8 million disks spilled out of an overflowing tank at the Hooksett Wastewater Treatment Plant in New Hampshire, along with about 300,000 gallons of raw sewage, and into the Merrimack River. These disks were later found on beaches throughout New Hampshire and in northern Massachusetts. Read more on this from Surfrider Foundation's Coastal Blog in Article 1, Article 2, Article 3. These disks were still being found on beaches in 2013!