University of California researchers have created an engineered sand to treat storm water runoff clean enough to return to aquifers
Engineers from University of California, Berkeley, have developed a mineral-coated sand that targets pollutants in storm water. The coated sand is composed of plain sand mixed with two forms of manganese that react to form manganese oxide, a mineral that binds to organic chemicals such as herbicides, pesticides and bisphenol-A.
“The way we treat storm water, especially in California, is broken. We think of it as a pollutant, but we should be thinking about it as a solution,” said Joseph Charbonnet, researcher on the project. “We have developed a technology that can remove contamination before we put it in our drinking water in a passive, low-cost, non-invasive way using naturally-occurring minerals.”
The manganese oxide-coated sand is safe for the environment and breaks common toxins found in storm water into smaller pieces that are less toxic and more biodegradable, as reported by Phys.org. While the coated sand is not capable of removing all contaminants from storm water, it would be effective coupled with a water purification system.
The sand loses its effectiveness over time but can be recharged by bathing the sand in a solution containing a low concentration of chlorine, which restores the manganese oxide’s initial reactivity. It would take approximately two days to recharge a .5-meter deep layer of sand using 25 ppm of chlorine in water, Charbonnet said.
“Manganese oxides are something that soil scientists identified 30 or 40 years ago as having these really interesting properties, but we are one of the first groups to use it in engineered ways to help unlock this water source,” Charbonnet said.
Next, the research team plans to perform field tests in Sonoma County, Calif., using storm water from a local creek.