How do Cruise Ships Make Fresh Water in a Sea of Salt?


Glass of Fresh WaterEmbarking on a cruise sees passengers confined to a ship and surrounded by salt water as far as the eye can see. Yet for weeks on end the showers are fresh and the tap water is drinkable.

How is this possible?

It’s all thanks to a process called desalination.

The Disney cruise ships are no different, their Facebook page of Fun Facts explaining “While cruising, Disney ships can convert sea water to fresh water for use on-board. An on-board desalinisation plant produces nearly 500,000 gallons of fresh water every day”.

How does desalination work?

Desalination can be done using two methods – flash evaporators or osmosis. Flash evaporators operate by boiling sea water and harvesting re-condensed steam vapour that is safe for drinking. The process draws its inspiration from the natural water cycle wherein sea water is evaporated, rises to form clouds and is then precipitated back to the earth in the form of rain water. Osmosis is a little more technical, using a fine membrane to filter out the salt and minerals that are found in sea water.

Is it safe?

While desalination is a highly effective method of removing the salt, it also removes the healthy minerals that are naturally found in fresh water. As such, the second stage of the desalination process passes the purified water through a mineralisation plant. This restores the water back to its natural mineral consistency. The water is also pH corrected and undergoes tests for impurities and sanitisation.

Where is it stored?

When the water has been cleared as 100% safe it is transported to the ships on-board storage tanks. The fresh water is then ready to be distributed throughout the cruise ship using a series of hot and cold water pipes. According to The Daily Mail the Oasis of the Seas has a huge 31 tanks that store over 2 million litres of water that are used by its passengers and crew each day.

After the water has been used on ship, it is treated again before being discharged into the ocean. There are strict environmental guidelines in place dictating how waste water is discarded. The process may not be simple, but it is absolutely essential to ensuring both passengers and the natural environment are kept as safe as possible!  

Image Source

“Glass of Water” by Greg Riegler


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