In the words of the English Poet, Samuel Taylor Coleridge:
“Water, water, everywhere
Nor any drop to drink.”
These words were made famous by Coleridgeʼs ʻThe Rime of the Ancient Marinerʼ and told the story of an old sailor lost at sea with his crew slowly dying of thirst.
So what exactly is seawater and why canʼt we drink it? The saltiness of the sea comes from sodium (combined with chloride) that leached out of the ocean floor as the oceans were formed billions of years ago. Although we know this process no longer occurs, there are sedimentary layers containing enough sodium that cover the ocean bed to continue making our seas salty.
Swallowing the occasional mouthful of seawater while out swimming wonʼt be especially harmful but drinking it to alleviate thirst is really not a good idea at all. Your kidneys simply canʼt cope with that amount of salt. You require more water than is in the saltwater to flush out the salt via your kidneys/renal system. If your kidneys canʼt get rid of the salt in your body quickly enough, your blood sodium concentration will rise to toxic levels producing fatal seizures and heart arrhythmia.
However, humans are especially clever at finding ways to harness the powers of the elements and a little bit of salt certainly hasnʼt stopped us finding a way to make it safe to drink.
The largest desalination plant in the world is in the United Arab Emirates which is capable of producing 300 million cubic meters of usable water per year. Tampa Bay, Florida, houses the largest US desalination facility which converts around 34.7 million cubic meters of water. While much interest is being focused on producing more desalination facilities, it is the sheer cost of the exercise that is most prohibitive.
Our fascination with seawater doesnʼt just end with swimming in it, sailing on it or trying to make it less salty so we can drink it. Recently a device has been invented that uses sea water as an antenna system. Instead of using a metal antenna to receive radio signals, a stream of salt water can receive and transmit via a two-way radio. This could prove useful as ships are now being designed that wonʼt have the room that current Navy vessels have to house adequate antenna space.
NASA is also keen to know more about our seawater. The Aquarius/SAC-D is an international mission using a specially equipped spacecraft that will measure ocean salinity from space. Aquarius will allow us to better understand ocean circulation, climate and fresh water cycles. Within a couple of months, Aquarius will be able to tell us more about sea surface salinity than the entire 125 year historical record from ships and buoys.
Do you think the ʻAncient Marinerʼ in Coleridgeʼs poem would be surprised to see what we can do with seawater these days?