How Desalination Works

Future of Desalination

As the number of desalination plants worldwide continue to grow, so do concerns about developing new technology to power the plants. Currently, large-scale desalination efforts require a lot of energy to operate and often are high-maintenance affairs, thanks to lots of working parts like membranes that tend to foul frequently [source: Schirber].

Costs are another concern: During the past five decades, public and private investment in developing desalination technology has reached more than a billion dollars worldwide. And even with the progress that's been made, the idea that desalination would do away with water scarcity is far from reality. And that's because it's still really, really expensive to plan, build and manage desalination plants [source: Water Science and Technology Board]. In fact, the average cost to turn one acre-foot -- about 325,000 gallons -- of salt water into fresh water ranges from $800 to $1,400 and requires a significant amount of energy [source: American Chemical Society].

Producing fresh water using reverse osmosis costs about one-third less than multistage flash, largely because of the costs of the thermal energy used by the latter method in the boiling process [source: Water Science and Technology Board]. Unfortunately, both processes -- as with all desalination techniques -- create brine. This by-product of desalinated water contains high concentrations of salt and, when released back into a natural body of water, can cause damage to marine life. That's because brine, which is usually denser than the water into which it's released, settles atop low-lying sediment where it depletes surrounding waters of oxygen [source: University of Texas at Austin].

These cost and environmental concerns are all part-and-parcel of the next round of improvements in desalination technology and processes. Light-weight portable desalination devices are being developed by researchers in Korea and at the Massachusetts Institute of Technology. The units produce enough fresh water to support several people. The process uses gravity -- simply pour saltwater into the top of the device -- to remove salt and other sediments using 1,600 filters [source: MIT].

Like these solar-powered portable units, large-scale reverse osmosis plants, although still in the planning stages, could also greatly decrease desalination plants' reliance on fossil fuels. In fact, the National Science Foundation granted $2.5 million to a team of experts at the University of Michigan studying solar energy's impact on desalination technology [source: Richard]. In addition to government funding in the United States and abroad, private funding sources are beginning to pay attention to developing more efficient desalination efforts. One thing is certain: If the desalination process improves, it could have the potential to change entire water-poor regions for the better.

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