New water purification system could help slake the world’s thirst
More than 1 billion people around the world lack access to fresh water, and the problem is growing: By 2025 a whopping two-thirds of the world’s population may face water shortages. To slake that thirst, some wealthy communities have invested in water desalination plants that turn salt water into clean drinking water. But these plants are too expensive for most communities to afford. Now, researchers have come up with a solar-powered technique that could make small-scale desalination systems affordable, even for individual households.
The approach is a new take on an old technology known as a solar still. These stills—large containers covered by clear plastic tarps or glass enclosures—direct sunlight onto a basin of salty water. Water evaporates, leaving salts behind, and then condenses on the plastic or glass, where it is captured. The trouble is throughput. The sun evaporates water so slowly that very little fresh water is produced—too little for most people to even bother.
To fix the throughput problem, researchers have tried topping the salt water with floating films dotted with nano-sized metal particles, typically made from gold. Gold is a good absorber of sunlight, and the nanoparticles funnel the sun’s energy into tiny hotspots that then efficiently evaporate water.
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