The world is facing a growing water crisis as an increase in demand and climate change impact water availability. However, engineers from MIT and China have created a possible solution. The engineers created a passive solar desalination system that converts seawater into drinkable water, which could revolutionize access to water globally.
What is Desalination?
Desalination is the process of removing dissolved mineral salts from water. It typically occurs during the natural water cycle. As seawater evaporates, it leaves salt behind and forms clouds that allow for rainfall. The process involves boiling seawater in a still, collecting the stream, and condensing it to get fresh water. Other processes include reverse osmosis, solar distillation, nanofiltration, electrodialysis, and gas hydrate formation.
The Cost of Traditional Desalination
Traditional desalination methods are expensive (making them affordable to affluent societies only) and environmentally damaging. The residue from the process results in brine – wastewater with a high concentration of salt and pollutants – often disposed of in the ocean. Disposing of additional salt and pollutants into the sea negatively affects marine ecosystems and life.
A New Hope in Solar Desalination
Solar desalination is a promising alternative to other harmful water desalination processes. It uses the sun’s energy to evaporate saltwater, leaving behind salt. The water vapor is then collected and condensed in large facilities, resulting in liquid freshwater. The one downside to this solution is that large land areas are needed to facilitate this process.
MIT’s Breakthrough Device
Researchers from MIT and China have developed a passive desalination system superior to existing systems inspired by the ocean and powered by the sun. Previous models had issues with salt crystallization and accumulation during the process, but this latest design has addressed them to allow for better water production and salt-rejection rates.
How the $4 Device Works
A paper in the journal Joule explains that the solar device circulates seawater similarly to ocean movements and, in combination with the sun’s heat, drives water evaporation, leaving the salt behind. The water vapor can be condensed and collected, resulting in drinkable water. The remaining salt is expelled to avoid clogging. This device’s affordability makes it special, costing only $4 to build.
Scalability and Potential Impact
The device is roughly the size of a small suitcase and can produce four to six liters of drinking water per hour. The engineers predict it can last several years before replacement parts are needed. The team hopes that a scaled-up version of the device will meet the daily water needs of a small family and could potentially help isolated coastal communities with access to seawater.
Cheaper Than Tap Water
Lenan Zhang, a research scientist in MIT’s Device Research Laboratory, stated that, for the first time, water produced by sunlight could be cheaper than tap water. The system’s extended lifespan and passive nature, which requires no electricity, make its overall operational cost cheaper than producing tap water in the United States.
Environmental Benefits
Desalination can sustainably replenish the water cycle and can be reused in irrigation processes in agricultural and forest growth activities. This means that less water is used, particularly in industries where high volumes of water are required. Desalination may not only reduce the high demand for freshwater but also provide a water surplus, helping preserve and restore freshwater-dependent ecosystems.
Addressing Environmental Concerns
This new device proves that the negative effects of desalination can be effectively controlled. Energy-efficient desalination processes, such as the device designed by MIT and Chinese engineers, can use natural energy sources like the sun to facilitate the removal of salt from seawater. Additionally, solar desalination processes can redistribute brine disposal, affecting marine ecosystems, to minimize negative environmental impacts.
Turning Environmental Problems into Economic Opportunities
Manzoor Qadir, a researcher from the Institute for Water, Environment and Health at the United Nations University (UNU-INWE), proposes “turning an environmental problem into an economic opportunity” by using brine for aquaculture, electricity generation, or natural metal recovery. These metals include magnesium, gypsum, calcium, potassium, chlorine, and lithium.
The Future of Desalination and Wildlife
With decreasing costs and increasing efficiency, desalination can provide a lifeline for wildlife by reducing pressure on natural water sources and decreasing brine deposits in the ocean. Desalination stabilizes and sustains water supply efforts, which can help maintain and restore habitats, supporting biodiversity and ecosystem health. The efforts to increase desalination process efficiency can ultimately help protect remaining ecosystems and help them recover from previous damage caused by the process.
The Path Forward
This desalination system, a tactic seen as a last resort option, has become a solution for water security and climate change mitigation. To realize its full potential, more research and development are needed. Therefore, involving engineers, researchers, authorities, and communities in need to improve desalination processes is essential as the benefits can help protect our livelihoods and our wildlife.
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