Get Ready for a Gold Rush in Your Bathroom
People have gone to the ends of the earth in search of precious metals such as gold and silver. Now scientists are starting to look for them much closer to home—in the sewage you send to your local wastewater treatment plant.
Scientists at the United States Geological Survey collected samples from eight wastewater treatment sites in urban and rural areas. They analyzed the samples for metals and found significant accumulations of silver, gold, copper, and even some lesser-known valuable metals such as vanadium, which is used in jet engines and other machinery. The sites didn’t differ much in the amounts of metals available.
If technology can be developed to extract bits of precious metals from sewage, some of the destructive environmental impacts of gold mining could be alleviated, according to the researchers.
“It’s important to find some domestic sources of these metals that can offset—though not replace—our need for primary resources and imports,” said Kathleen S. Smith, a scientist with the USGS.
She said that gold and silver in sewage come from everywhere, including household products and detergents.
“Wastewater is anything that goes down the drain,” she explained. “That includes sources from the shower, kitchen, garbage disposal, and laundry.” Of course, part of that waste stream comes from the toilet.
It is treated through a variety of chemical, physical, and biological processes. What’s left is clean water and biosolids. Those solids—the U.S. generates 7 million tons annually—may be a source of value.
“The particles are very small—about 1/100 the width of a human hair,” said Smith. “We think there are smaller particles present that we need specialized equipment to look for.”
Another group of researchers investigated the value of sewage. They estimated that there is about $280 worth of metals per ton of sludge, but the cost of extracting them remains unknown.
“No technology exists that is applicable at large scale, or even at pilot scale, for a variety of metals,” said Pierre Herckes, a chemist at Arizona State University and coauthor of a recent paper published in Environmental Science and Technology.
He pointed out that removing metals from sludge is a win-win: The metals can generate revenue, and removing them could allow the remaining sludge to be used as fertilizer. “Removing metals including the toxic metals could alleviate the concerns related to land application of biosolids,” he said.
More work needs to be done to figure out how to extract tiny amounts of metals without harming the remaining organic matter. Smith said microbes may be able to bioaccumulate the minerals, making them easier to remove. She presented her study this week at an American Chemical Society conference.
Herckes said his group’s research is also looking at recovery processes that are economically viable.
Related stories on TakePart:
• Is Gold the New Conflict Diamond?
• On the Trail of Illegal Gold Miners
• Are You Buying ‘Dirty' Gold Jewelry?
Original article from TakePart
