Swiss flushing away millions in gold and silver every year

For the most part, however, the experts believe that recovering metals that end up in sewage sludge is not cost effective yet.

According to the researchers, more than 6,500 pounds of silver ($1.8 million at current prices) flows into Swiss waste water each year.

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. There were also high concentrations in the Ticino area, which is home to gold refineries. Each year, about 70 percent of the world's gold passes through the oil refineries of the country.

As well as precious metals, researchers looked at the concentration of other elements which are useful in luminous paints and electronics.

But the study, commissioned by the Swiss government and carried out by the water research institute Eawag, was described by Eawag as "the first systematic, quantitative assessment" across an entire industrialized country.

But Ticino, an Italian-speaking region in the south of Switzerland, contains enough gold refineries releasing trace amounts of the metal into sewage pipes to make recovery there "potentially worthwhile", according to a news release by Eawag.

The scientists evaluated any possible environmental hazards, and found that in the overwhelming majority of cases, there was not any known environmental risk from the high concentrations of metals. The USGS explored ways of removing the possible risky metals from sewage that is treated and used in fertilizer and pursued a possibility of extracting the valuable metals in sewage as a possible profitable resource.

Currently, the researchers are checking whether it's worthwhile to extract the precious metals from the sewage.

In 2015, a group of researchers in the U.S. The study also found that the particles are filtered from the water through the existing systems before they reach people's taps.

Vanessa Coleman