Stormwater pollution is a water-quality issue that affects the green industry. The herbicides and pesticides we apply to lawns and landscapes runs off after storms (or, as result of overwatering) and ends up in storm drains. From there, it travels to lakes, streams the ocean, and can even find its way into our potable water supply.
There may be a solution to this problem, however, thanks to some scientists at the University of California, Berkeley. According to a story published on the New Atlas website, they’ve developed an "engineered sand" that can clean up road-polluted liquid to the extent that it could possibly even be used for drinking water.
The material is actually just regular sand that's been mixed with two types of naturally-occurring manganese that react with one another to become manganese oxide. That compound is harmless to humans and the environment.
When water contaminated with organic pollutants such as herbicides, pesticides and bisphenol-A is run through the sand, those chemicals bind with the manganese oxide. This process either removes them from the water entirely or breaks them down into smaller, less toxic pieces that are more biodegradable. A secondary purification system, used along with the sand, could likely take care of the leftovers.
The effectiveness of the manganese oxide does diminish over time. But, it can be completely recharged by running weakly-chlorinated water, at a concentration of 25 parts per million, through the sand. It’s estimated that a 1.6-foot layer of the sand could be revitalized by running such water through it for about two days.
The scientists hope that the sand could be placed over underground water-storing aquifers, with stormwater runoff percolating through the material before entering the aquifers. They will test their invention soon on stormwater from a creek in Sonoma County.
"The way we treat storm water, especially in California, is broken,” said graduate student Joseph Charbonnet, a research-team member. “We think of it as a pollutant, but we should be thinking about it as a solution. We’ve 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."
A paper on the study was recently published in the journal Environmental Science and Technology.