Saturday, 20 August 2011

Geography Picture of the Day - Could seawater solve the freshwater crisis?

By 2025, it has been predicted that 1.8 billion people will live in areas of extreme water scarity and so, desalination (the removal of salt from water) is increasingly being proposed as a solution to this huge problem. However, before desalination can make the impact required to solve the looming water crisis, much worl needs to be done to overcome the obstacles that make it an expensive and inefficient process......
Desalination plants such as the U.K.'s Thames Gateway facility use
reverse osmosis technology.

Scientists predict that by 2016, the amount of fresh water produced by desalination plants will exceed 10 billion gallons (38 million cubic meters) a year, or double the rate in 2008. Modern desalination plants use a technology called reverse osmosis,  which involves pressing salty water through really thin, semipermeable plastic membranes. Unable to pass through, large molecules or ions, such as salt, are filtered out, so fresh water flows out the other side. This method wastes much less energy than earlier desalination techniques, such as heating seawater and harvesting fresh water from the steam. However a typical reverse osmosis plant can still spend up to 40 percent of its operating costs on generating electricity to run the system—a big reason engineers are searching for ways to cut costs and make plants more efficient, starting at the membrane level.

Sounds like this technology, especially if the amount of electricity required can be reduced and the efficiency increased, could be used a lot in the future to try and secure water supplies. However, I am sure that it has other disadvantages, like the environmental impacts on oceans and ecosystems. Also what would you do with the salt as I am guessing if it is on a large scale then quite a bit of salt will be produced? Linking it to my EPQ, I am unaware of how much salt would be produced but by dumping the waste salt back in the oceans, whilst removing large volumes of water, the salinity of the oceans will be affected - something intrinsic to the stability of the thermohaline circulation..........

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