Typically, stormwater is collected and treated to reduce pollutants before discharging downstream.
Researchers at the University of California Berkeley have developed a sand material that can treat storm runoff used for drinking water.
“When it rains heavily, even in arid places where water is scarce, the stormwater typically just runs off the streets and down the sewer drains. Thanks to a new “engineered sand,” though, that road-polluted liquid could soon be cleaned up and used for drinking water.
Developed at the University of California Berkeley, the material is actually just regular sand that’s been mixed with two types of naturally-occurring manganese. These react with one another to become manganese oxide, which is harmless to humans and the environment.
When water contaminated with organic pollutants such as herbicides, pesticides and bisphenol-A (BPA) is run through the sand, those chemicals bind with the manganese oxide. As a result, they’re either removed from the water, or they’re broken down into smaller pieces which are less toxic and more biodegradable – a secondary purification system, used in tandem with the sand, could then likely take care of them.
Although the effectiveness of the manganese oxide does diminish over time, it can be completely “recharged” by running weakly-chlorinated water through the sand. It is estimated that a half-meter-deep (1.6-ft) layer of the sand could be revitalized by running such water through it for about two days, at a chlorine concentration of 25 parts per million.”