Airdate: Jan 25, 2019
Scientist: Paul Westerhoff
Nanoparticles of gold are showing up in some unlikely places.
Golden SewageAs the saying goes, "there's gold in them there hills". And there's also nanoparticles of gold showing up in some unlikely places. I'm Jim Metzner and this is the Pulse of the Planet.Westerhoff: So it turns out that you can find gold in sewage at a water treatment plant.Paul Westerhoff is the Vice Dean for Research and Innovation in Engineering at Arizona State University. Westerhoff: This is at the wastewater treatment plant - everything we flushed down the drain. And what we found there, is we found nano gold. So we started thinking, where does that nano gold come from? We had to develop ways to measure it and see it, but we figured, okay, people put gold fillings in teeth, there's gold in electronics. There's actually gold leaf and when it breaks down into little pieces, it'll end up there. So we started finding these gold nanoparticles in sewage. Not a huge amount. There's also silver, there's platinum and palladium. So it becomes that sewage treatment plants are a new mine for cities.So we've explored ways to actually recover the gold from sewage. We have one technique that we've learned that's a combination of squeezing and pressurizing sewage sludge, which is bacteria, and gold, and silver, and all this other stuff squished together, but when you pressurize and squeeze it, we end up with some clean water, biofuel that we could burn. And we end up with then a concentrated mixture of ash. And that ash is super enriched in gold and silver, and other minerals. And so we can bring that to a smelting mill and maybe recover gold and silver. So currently, it's not economically viable to do this. But in the future, I think as we realize how to keep pollutants out of the environment, we can look at ways to recover important resources like gold and silver from their same waste streams. Pulse of the Planet is made possible in part by the Center for Earth and Environmental Nanotechnology and the National Science Foundation. I'm Jim Metzner.