Water is the source of life, and each living person requires a lot of it on a daily basis. With that in mind how do cruise ships get fresh water while out in the vastness of the open sea?
A cruise ship is a complicated vessel that requires the interoperability of multiple systems for it to function properly. That includes making sure that its crew and passengers are well taken care of biologically and hygienically.
As cruise ships grow ever larger and more complex, further people and additional attractions will naturally accompany this growth. That is bound to make freshwater use increase dramatically.
This leads us to the core of this guide on how cruise ships acquire useable freshwater and in large quantities at that.
How Cruise Ships Get Fresh Water
Some cruise ships have near Olympic-sized swimming pool levels of stored water on board. But even that has its limits especially on extended voyages miles away from the nearest source of freshwater.
That said, engineers solved this problem by simply not relying on a single method for its acquisition. Instead they branched out using multiple technologies and systems that allow for increased efficiency in water utilization and even water treatment and recovery systems all onboard the cruise ship itself in order to recycle the water after being used.
Bunkering is a maritime term for supplying logistics to a ship. In this context, bunkering means the carrying of freshwater from a local source in port and loaded onto the ship.
This is the simplest method of getting freshwater. However, this is not a sustainable method because aside from the problem of needing a huge amount of space to fit everyone’s daily water needs plus that of the machinery in radiators for example, and in attractions like a pool, this stockpiled freshwater will run out within a few days, significantly hindering a cruise ship’s range and operational time.
As previously mentioned the stored freshwater onboard will run out quite quickly unless there was a way to continuously acquire it during the voyage.
But isn’t a ship surrounded by water and why not use that you say?
Seawater obviously isn’t safe for consumption and use either by people or by machinery. However, you are on the right track in that seawater can be cleaned out and processed into freshwater.
Fortunately, we have a process called desalination, which is the removal of salt and other impurities from water, and there are two standard methods of doing it.
This is a method in which the source water, seawater, in this case, is pressurized and pushed through a series of membranes only large enough for water molecules to pass through but blocking everything else.
This results in all the salt and impurities getting stuck on these membranes, and leaving only clean fresh water at the end.
The downside to this method is that it requires these membranes to be constantly cleaned to maintain freshwater output which leads to operational downtime, and they do have a limited number of uses before needing to be replaced.
Another method of desalination is something even survivalists use but on a much larger scale. Simply boiling water causes it to evaporate as pure water vapor, with all the salt and dirt left behind, this water vapor is then pumped into condensers which turn it back into liquid water.
Now, this is great since it is constantly operating plus the removal of impurities can be automated without needing to stop the machine’s operation.
Unfortunately, this requires a huge amount of energy which could’ve gone to powering electronics, navigational systems, and attractions, not to mention the resulting condensed water is at near boiling point temperature. Though useful in a hot spa, it is practically useless everywhere else unless additional steps are taken to cool the water before use.
Unlike the desalination processes mentioned above which involve actively spending energy and effort in order to clean water, condensation relies on utilizing the potential water sources already present due to normal ship operation.
This isn’t water production per se but rather reducing wastewater by efficiently harvesting other sources of water.
Steam from cooling the ship’s engines, kitchens, and other facilities plus the water produced by air conditioners are all collected and siphoned into a storage tank where they will be cleaned and reused.
Now aeration is also a unique process in that it doesn’t do anything with the water in particular. What it does is that rather than pressurizing the fresh water running through the ship for cooking, cleaning, bathing, and etc, with more water, instead, it uses air.
In order to achieve the same amount of pressure, it mixes in high-pressure air with the water in the pipes so that flushing the toilet, using a shower or faucet, works normally but uses significantly less freshwater.
Although it doesn’t produce more freshwater, it contributes by using less freshwater.
How the Water System Works on a Cruise Ship
It all starts with the bunkering, water is stored on the ship. As this water gets used through various operations, these are then treated and recycled as under every ship lies a water treatment and recycling plant.
Sewage is treated and discarded as waste water, whereas water that comes from other sources like pools and engine operation can be recycled by using the methods mentioned previously.
Seawater is also utilized to help cool some machinery then can be desalinated for further use.
How is Water Saved on a Cruise Ship?
Through the multi-staged processes of aeration and condensation, a sizeable amount of water can be saved. Add desalination processes to that and you can be sure that most of the water stored in the cruise ship will be recycled, reused, and will last until the next port.
How Much Water Do Cruise Ships Carry?
Cruise ships have large internal storage tanks for freshwater, in the magnitude of thousands of gallons at a time, and some can even carry up to two million liters of freshwater and that’s 500,000 gallons worth.
In conclusion, cruise ships are loaded with freshwater while docked, then combinations of onboard desalination systems allow for the production of water. Finally, efficiency systems make sure that water is properly utilized and that is the answer as to how do cruise ships get fresh water.