Americans are flushing a lot of valuable metals, according to new research by the United States Geological Survey. For eight years, researchers took monthly samples from wastewater treatment plants across the country and cataloged what they found. Silver was particularly common, appearing at an average of 28 parts per million, although copper, lead, and vanadium were also found in high concentrations. While the findings aren't perfectly representative of the nation as a whole, they indicate that a wealth of minerals are being pooped out on a daily basis.
The surprising wealth of minerals is most likely the result of compounds in common consumer products, said the researchers, who presented their findings today at the National Meeting & Exposition of the American Chemical Society. "There are metals everywhere," said USGS geologist Kathleen Smith, "in your hair care products, detergents, even nanoparticles that are put in socks to prevent bad odors."
A city of 1 million people produces $13 million in sewage-based minerals per year
The team used industrial mining techniques to extract the chemicals, although it's still unclear if the process would be cost-effective at scale. "We're interested in collecting valuable metals that could be sold," said Dr. Kathleen Smith, "including some of the more technologically important metals, such as vanadium and copper that are in cell phones, computers, and alloys." A similar study published earlier this year estimated that a city of 1 million people (roughly the size of San Jose, California) would produce $13 million worth of sewage-based minerals over the course of a year.
A metal-removal program could also make metal-tainted sewage suitable for use as fertilizer. Only half of all treated sewage is viable as fertilizer, and Smith hopes that metal removal could increase that percentage. Waste treatment has seen a number of technological breakthroughs in recent years, particularly as non-profits look for technologies that could be useful in developing nations. In January, the Gates Foundation unveiled its own waste-treatment system, the Janicki Omniprocessor, which converts sewage into fertilizer ash, electricity, and drinkable water.