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September 8, 2018

Engineered sand could remove nasty toxins to produce drinkable water

by John_A

Water is one of our most underappreciated resources. For people with steady access to this life-giving liquid, it’s absence can seem like a distant dystopian nightmare. But some 783 million people lack clean water worldwide, according to the World Health Organization, and even in the United States, parched communities suffer from prolonged droughts.

Researchers at the University of California, Berkeley are working on a low-cost solution to make better use of the water at hand. They’ve engineered sand, coating the grains in compounds that react with and help destroy organic pollutants found in stormwater. The solution could be used to help support local sources of potable water for water-stressed communities.

“In all but the most arid places, enough rain falls within the city limits to provide the water we drink and use in our homes,” David Sedlak, a civil and environmental engineering at UC Berkeley who advised on the project, told Digital Trends. “Unfortunately, we cannot build reservoirs in a crowded city and rain barrels are too small to hold all of the water that we need. To capture the rainwater that falls in our cities, engineers have developed new approaches for infiltrating rainwater into the ground, where it can be stored in groundwater aquifers.”

The problem is that a lot of rainwater drains off rooftops, sidewalks, and parking lots, which pollute it with organic gunk and chemicals, and make it utterly unusable.

Sedlak and graduate student Joseph Charbonnet developed what they hope may provide a low-cost solution for decontaminating stormwater for drinking and household use. Coating sand in two kinds of manganese that react to form manganese oxide produces engineered sand thatbinds to chemicals like herbicides and pesticides and pulls them out of the water.

“If we are going to treat [water] as it infiltrates into the ground, we need to apply technologies that are simple, inexpensive, and do not require a lot of oversight,” Sedlak said. “Rainwater is typically introduced to aquifers by allowing it to percolate through sand. We have invented a new way of coating the surface of sand grains with a thin layer of manganese oxide.”

The research team’s idea is to add an engineered sand to current water reclamation basins, where standard sand is currently used. The stormwater would then be partially decontaminated as it percolates through the sand and into an aquifer. During rainy months, the aquifer would replenish, providing a source of water through the dry season.

The Berkeley team’s engineered sand doesn’t remove all contaminants, meaning it would need to be used in conjunction with other types of purification systems to make it potable. Sedlak pointed to the complementary work at the National Science Foundation’s Engineering Research Center for Reinventing the Nation’s Urban Water Infrastructure, where they create materials to remove toxic metals and pathogenic microbes.

A paper detailing the research was published last month in the journal Environmental Science & Technology,

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