Finding gold in our waste sewage: Are you shitting me?

Finding gold in our waste sewage: Are you shitting me? 

Whenever I browse through the Proceedings of the National Academy of Sciences (PNAS), one of the most prestigious academic journals in the states, I never expect to find myself chuckling while reading through some of the world's most esteemed research publications. However, today I found myself both wide-eyed and smiling while reading about how much wealth is just sitting, unharvested, in our waste sewage running under our cities.

Paul Westerhoff from the School of Sustainable Engineering and The Built Environment at Arizona State University (ASU) accidently found that sewage contains precious metals worth millions by when he was trying to study the threat posed by engineered nanomaterials on the environment. He was building off of the research done by Rolf Halden, the director of the center of the Center for Environmental Security at ASU’s Biodesign Institute on whether the contents of sewage sludge are a good indicator of the chemicals and toxins that society uses. Halden says that “wastewater moving through a city is like the blood in a body;” It shows all the chemicals that humans are exposed to. 

Nanoparticles are used abundantly in many products like cosmetics and sunscreens, which ends up in city sewage or in rivers and streams. Westerhoff figured that the best and cheapest way to study the flow of nanoparticles into the environment was to examine sewage sludge. Under their transmission electron microscope (TEM), him and his team not only saw titanium microparticles, but also gold. And they were surprised at the quantity that they found. Within the sewage, they found gold at 1 part per million and other metals like silver at even higher quantities. They estimated that each year in a city of a million people, there is a whopping $13 million dollars of wealth.

Westerhoff thinks that, looking toward a sustainable future, we could create a compact waste processor that can filter out different components of waste. If we implement better wastewater processing, not only could we collect great profit, but we could also prevent heavy metal pollutants, pathogens and environmental pollutants like phosphorus from re-entering the environment. Additionally, it would decrease the rate at which we harvest metals from the earth.

The time is now for our country to begin decreasing our impact on climate change. Westerhoff’s discovery has me curious about the other things hiding in what our society dismisses as waste or unusable materials. As we continue to see an increase in scientific breakthrough in regards to sustainable advancements, I’m left wondering when these concepts are going to be implemented on a large scale in the United States.

Post based on, "Inner Workings: Finding precious metals in unlikely places" by John B. Carey and published in PNAS

Posted by Lauren Mason (3)