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The Swiss sewage system is literally a gold mine

12 October 2017

The discovery of sewer gold in Switzerland has social media talking.

That's over $2.25 million in gold and $2.12 million in silver, researchers report.

Still, gold is not the only prized possession coursing through the sewage pipes in Switzerland.

More than $3 million of precious metals are found annually in sewage from more than 60 wastewater treatment plants in Switzerland, according to a study by the Swiss Federal Institute of Aquatic Science and Technology.

The study focused primarily not on recovery value, but on fluxes and mass balances: this is the first time trace elements in wastewater have been systematically surveyed for an industrialized country.

In most cases, it would be so expensive to extract and recycle that it wouldn't make economic sense - recovery would be "scarcely worthwhile", as the researchers put it.

The scientists noted that the concentrations found in the wastewater don't pose risks to the environment, and wide-scale recovery wouldn't be worthwhile.

But the concentrations of metals varied across the country.

In one part of southern Switzerland that is home to several gold refineries, elevated levels of metal deposits might even be worth collecting. A group of researchers led by Eawag environmental chemists Bas Vriens and Michael Berg has now carried out the first systematic, quantitative assessment of elements discharged in effluents or disposed of in sewage sludge.

The researchers believe the tiny flecks of gold flow into the waste water system from the country's famed watchmaking industry and gold refineries.

Meanwhile, the news of the untapped wealth in Swiss sewage might bring to mind another story we recently covered on The Two-Way - the tale of 500-euro banknotes mysteriously shoved down toilets in Geneva.