A hidden treasure of Switzerland: sewage gold. The price tag on the accumulated gold: roughly $2 million. But the sewage pipes are packed with it.
Scientists at the Swiss Federal Institute of Aquatic Science and Technology estimate that about 43 kilograms of gold - worth about $1.8 million - passes through the country's waste water every year.
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.
Scientists determined it's not worthwhile to recover the trace amounts of the elements outside of exceptional cases.
The averages and annual tonnages say little about the distribution of element concentrations, which vary widely - by a factor of up to 100 - from one treatment plant to another.
Swiss scientists have found that 43kg of gold worth about $1.8 million is passing through Switzerland's wastewater each year, as first spotted by Bloomberg.
"Concentrations of gold in sewage sludge are sufficiently high for recovery to be potentially worthwhile", the researchers wrote.
The concentrations of elements pose no risk to the environment as most cases lay below harmful limits. The USGS has explored ways to remove potentially unsafe metals from treated sewage that is used as fertilizer and also pursued the possibility of extracting valuable metals from wastewater as a potentially profitable resource. The researchers investigated the extent to which treatment plants contribute to total fluxes in receiving waters.
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.