As a rule, during heavy torrential rains, water is either absorbed into the ground or goes into the sewer system. But it could well be used as a source of drinking water - especially in the arid regions of our planet.
A team of researchers at the University of California, Berkeley has developed a water filter composed of ordinary sand mixed with two types of natural manganese. By interacting with each other, these ingredients turn into manganese oxide (MnO2), harmless to humans.
Water contaminated with herbicides, pesticides or the plastic chemical bisphenol, passing through such a sand filter, reacts with manganese oxide. Harmful chemicals "bind", leaving water "free". At the same time, they are crushed into small, less toxic chemical fragments, which are easily biodegradable in the process of secondary purification.
Naturally, in the process of repeated use, the efficiency of the filter decreases, but it can be "recharged" by thoroughly rinsing with technical water. According to calculations, a half-meter layer of sand can be renewed by passing water with a chlorine content of 25: 1, 000, 000 through it for two days.
According to scientists, in the future, the sand filter can be placed above the aquifers to clean storm water. In the meantime, they intend to test the new technology on rainwater from a stream in Sonoma County (USA).