The Promise of Peat

UMN researcher Dr. Brandy Stewart studies carbon-rich peat to filter harmful metals from wastewater

By Lauren Holly

Water flows into our homes every day. We use it to wash our hands, do dishes and, of course, drink. Eventually, it ends up at a wastewater facility where it is treated, filtered, and safely discharged. Stormwater is different. Runoff from pavement, agriculture, and other human activity (think roads, golf courses, etc.) bypasses water treatment facilities. It flows directly into the environment, carrying the micronutrients, metals, and other contaminants picked up along the way. 

“Any time major metropolitan populations reside near bodies of water, we raise concerns over how to best protect that water from the inevitable contaminants that arise out of human activity,” says Dr. Brandy Stewart, a University of Minnesota researcher who works in Dr. Brandy Toner’s Low-temperature Geochemistry lab. The group studies how nutrients and metals move through oceans and sediments, including the role microbes play in this complex process. 

To help prevent contamination of nearby waterways, industries that use metals and similar contaminants are required to treat stormwater before it is released into the environment. The process can be both time-consuming and costly. Stewart, who studies contaminants moving through soil and waters, is looking at peat as a cost-effective solution for removing metals from stormwater.

Created by decaying plants in bogs and wetlands, peat is a remarkably flexible material. Gardeners prize peat for its ability to retain soil moisture. It’s also an important vehicle for beneficial microorganisms that can help increase agricultural yields. But researchers from the Toner lab were drawn to peat because of its amazing ability to remove metals from water—naturally.

The Toner lab has partnered with American Peat Technology (APT), a Minnesota company producing a commercially available peat product for treating contaminated water. At a field site in Michigan, APT’s product is used to treat water at a metal plating factory. Drainage from the factory runs through large treatment tanks containing peat that captures harmful metals like chromium, cadmium, and zinc.

Stewart’s research, supported by a MnDRIVE Environment Seed Grant, indicated that removal rates were actually higher than the team (Toner and Stewart along with collaborators Dr. Cody Sheik and Paul Eger) initially predicted. But Stewart suspects that peat may not be doing the job on its own. Bacteria and microbes may also contribute to the system’s success, and help sequester contaminants. 

“If we figure out the mechanism that is sequestering the chromium, we can try to enhance it and market it to other uses,” Stewart says. Ultimately, her goal is to make peat as efficient as possible. “It’s clearly working, but we want to see if we can use a different amount, or use it at a different temperature,” she explains. “Imagine if we only needed one tank instead of seven.”  

Given that it is a natural product, peat is an attractive solution for environmental remediation. It doesn’t require constant upkeep or input of chemical reagents. In fact, peat can sit in the tanks for up to four years without being changed. It’s proving itself to be a low-cost, low-maintenance treatment that ultimately could be a win for both industry and the environment.