You might be flushing valuable metals down the drain.
New research presented Monday at a meeting of the American Chemical Society says that sewage might be an overlooked source of gold and silver, as well as copper, palladium and vanadium that are used in cell phones and other electronics.
Kathleen Smith and other researchers at the U.S. Geological Survey are studying samples from various wastewater treatment plants in small towns, big cities and rural areas to see what useful stuff might be hidden inside.
"The source is whatever goes down the drain," Smith told CBS News. That means human waste as well as cosmetics, soaps and odor-fighting nanoparticles.
The project takes a two-pronged approach. For one, Smith is looking for better ways to remove certain metals from biosolids so that more of the 7 million tons of sludge generated in the U.S. each year can safely be used as fertilizer.
But she is also interested in how these metals can be put to use themselves.
"In the other part of the project, we're interested in collecting valuable metals that could be sold, including some of the more technologically important metals, such as vanadium and copper that are in cell phones, computers and alloys," Smith said in a statement.
A January 2015 study in Environmental Science and Technology estimates that for every one million people in the nation, there could be $13 million worth of metals and rare earth elements coursing through the sewers each year.
In her studies, Smith has turned up enough microscopic specks of gold in biosolids that if the same amount were found in rock it might the be considered commercially viable to mine it.
So does that mean we're literally pooping gold? Smith said that as to "the question about whether or not human feces contain metals ...we don't know." But it's too soon to rule it out.