You may have seen headlines about extracting gold from your poop. That's not technically true but the reality is still pretty amazing. There are trace amounts of metals inside sewage, including gold, silver, and even platinum. Most of this comes from cleaning products like shampoo and even some clothing that now contain metal nanoparticles for one reason or another. For more details check The Guardian.
Some of this metallic contamination that ends up in the sewers is also harmful, like lead and other heavy metals. The original inspiration behind extracting trace metals from sewage was to simply remove these harmful components and make sewage usable. It may sound pretty gross but the solids produced from waste treatment eventually become a portion of fertilizers for fields and forests. But metal contamination reduces the amount of usable solids by roughly half.
Building off of a long-term study done by Arizona State University, and published back in January, scientists have announced that their might be usable metals in sewage. That study tested a large number of samples from various locations for metal fragments using a scanning electron microscope. Surprisingly, the concentration of precious metals was similar to certain deposits that are actually found in commercial mines.
You can't simply pan the sewage for gold like an old-time gold rush enthusiast, as even naturally occurring ores can contain low concentrations of the metals. However, it does mean that chemicals used in conventional mining to leach out trace metals could be used in a much safer and controlled environments. Counting everything up the study estimated that roughly $13 million in precious metals can be harvested from a city of 1 million, per year.
The Guardian article is also quick to point out that a sewage treatment plant in Japan is already successfully extracting gold from its sludge. Others around the world are attempting to extract pure nitrogen and phosphorus to use as fertilizers, and one in Sweden is attempting to produce bioplastics from waste. It would appear breakthroughs in chemistry have made it an interesting time to be involved in sewage treatment..
