The poisons of the last gold mine become raw material for the purification of polluted waters. At the end of the gold season, in Furtei, in the Medio Campidano, about forty kilometers from Cagliari, that of environmental reclamation began. With particular attention to the circular economy. Where the material deriving from the treatment of polluted waters becomes raw material for the reclamation itself.
The plant used to restore what has been repeatedly called “the reservoir of poisons” affects the acidic waters that have an “important” presence of lead, zinc, cadmium, iron, manganese and “aluminum resulting from the oxidation of sulphides and pyrite ». As the technicians point out, these are the waters of the “tailings dam” coming from the production cycle and those present in the cultivation voids that have filled up over time.
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Very high concentration of sulphates
“The main problem of these waters are the sulphates whose concentration varies from 6,700 to 18,000 milligrams per liter – underlines Ilaria Desantis, geologist from Igea, an in-house company in the Region and holder of the mining concession – and in order to be able to break them down, treatment is osmotic from which the permeate comes out, that is purified water and a brine rich in sulphides and sulphates that should be taken to disposal ».
This is where the recovery process begins, leading to considerable savings, since 500 cubic meters of water (500 thousand liters) are processed daily with a production of 120 cubic meters of brine. Equal to the content of 17 articulated lorries. “Without this recovery process – argues the geologist – we would have had to send this waste with very high costs and a high presence of heavy vehicles”.