I was asked how cruise ships clean their water, ala the desalination process.

Desalination, refers to any of several processes that remove excess salt and other minerals from water.

The desalination process on a cruise ship uses either flash evaporators or osmosis. Flash evaporators boil sea water and re-condense the steam vapor, producing fresh drinking water. This method is similar to the natural water cycle, where sea water is heated by the sun, rises as steam to form clouds, and then falls back to earth as rain. The second method, osmosis, filters sea water through a fine membrane to separate pure water from salt and other minerals. Cruise ships do not desalinate water near ports or close to land, because coastal waters are the most contaminated.

After desalination, the water is passed through a mineralization plant, which adds minerals. This is necessary because the healthy minerals naturally found in drinking water have been removed by desalination. At this stage, the water is also checked for impurities, sanitized, and the pH is corrected. The water is then sent to massive storage tanks on board the cruise ship.

Next, the water is routed to hot and cold systems. Miles of distribution pipe move the water around the cruise ship. After the water is delivered through a sink or shower, and used by cruise ship passengers or crew, it must be treated again before it can be discharged. All cruise ships must follow strict environmental laws in the treatment of waste water. Even after treatment, the water is not immediately released, but is held in special storage tanks when the ship is close to land, in port, or other sensitive environments.

It's a complex process, but necessary in order to ensure the health of cruise ship passengers and the natural environment.

Drink up!

Partly right, they do use flash evaps to desalinate the water. They also have a reverse osmosis plant for backup, but rarely use them.

They get the steam for the evaps from waste heat off the turbines (Radiance class) or diesel exhaust (all the other classes).

The don't remineralize the water, they do chlorinate it, they have to, by law.

The water goes directly from the evap (approx 150F since the evaps run at about 5" vacuum and boil at 155F or so) to the hot water pipes. What isn't used in the hot water piping (most of it) ends up in tanks below the water line, where it cools to sea water temp. That is why the water is always warm in the Caribbean. When the sea water is 85F ot 90F, that's as cold as the potable (potty) water tanks get.

The process is called osmosis....

This is one of the 2 de salination plants on the Independance. Each produces 45,000 litres/hour

and a side view

and heres the sea water intake (sea chest), one for each plant.

This is one of 2 osmosis filters (made in England!) which filters the grey water on the ship to produce 10,000 litres/hour each.

Simon

Actually, they throw a giant one of them sham-wows overboard. It is tied to a rope. It absorbs over ten times it's weight in water. They then haul it back on board. They wring out the sham-wow over a bucket, saving the water and the impurities stay in the sham-wow. They do this several times an hour, until the sham-wow needs washing. Then they replace the sham-wow with a new one and start the process over again.:D

Well you know how they make bottled watter right? It involves a municipal source and a hose ... ;)

Nice work.....now if we could have a turn water into wine flirtration system what would ne even nicer.

On the HAL ships we have been on in the past two years, the Environmental Officer offers a slide presentation and lecture during the cruise on all environmental and safety issues and policies aboard the Holland America ships. My husband and I are both retired from the safety/environmental profession and enjoy these presentations immensely.

There is a Q & A session at the end of the officer's talk. The day & time of the talk is listed in the ship's daily program, and is scheduled to last about an hour. They are scheduled on sea days to maximize passenger availability.

Unfortunately, most of these presentations that we have been to have not been well attended, in spite of all the talk we hear on the ship voicing concern for the environment and speculating about what actually does or does not occur on board.

It is an excellent opportunity to see the lengths that these cruise ships go to in protecting our oceans, become acquainted with the overwhelming number of E & S regulations that differ from port-to-port, understand the concern for passenger safety and all that is done to assure your safety, and much, much more.

We would highly recommend attending one of these Environmental and Safety presentations if they are offered on board your ship. They are extremely informative and the Q & A session afterward will give you the opportunity to voice your particular concern & have it addressed by the man in charge.

Smooth Sailing! :)

Well you know how they make bottled watter right? It involves a municipal source and a hose ... ;)

Many tourists here (30 miles from Mexico) go to Mexicoand take bottled water as they have heard "don't drink the water". Our local WalMart for quite a while was selling bottled water for that purpose and because many like it better than tap water. In fine print on the back it said "Bottled in Mexico". :D

Nice work.....now if we could have a turn water into wine flirtration system what would ne even nicer.

Hasn't been done for 2000 years.

"Bottled in Mexico"...and Hasn't been done for 2000 years.

Good stuff, great sense of humour.

The process is called osmosis....

Reverse osmosis is used to desalinate. (Osmosis would be used to salinate, which would be of no practical use).

With a semi-permeable membrane, the flow would normally be from the freshwater side to the saltwater side (osmosis). Very high pressure is used to force the water the other way (reverse osmosis) so that the salt water flows through the membrane to the freshwater side. The salt ions cannot pass through the membrane, so only fresh water gets through.

Desalination, refers to any of several processes that remove excess salt and other minerals from water.

 

The desalination process on a cruise ship uses either flash evaporators or osmosis. Flash evaporators boil sea water and re-condense the steam vapor, producing fresh drinking water. This method is similar to the natural water cycle, where sea water is heated by the sun, rises as steam to form clouds, and then falls back to earth as rain. The second method, osmosis, filters sea water through a fine membrane to separate pure water from salt and other minerals. Cruise ships do not desalinate water near ports or close to land, because coastal waters are the most contaminated.

 

After desalination, the water is passed through a mineralization plant, which adds minerals. This is necessary because the healthy minerals naturally found in drinking water have been removed by desalination. At this stage, the water is also checked for impurities, sanitized, and the pH is corrected. The water is then sent to massive storage tanks on board the cruise ship.

 

Next, the water is routed to hot and cold systems. Miles of distribution pipe move the water around the cruise ship. After the water is delivered through a sink or shower, and used by cruise ship passengers or crew, it must be treated again before it can be discharged. All cruise ships must follow strict environmental laws in the treatment of waste water. Even after treatment, the water is not immediately released, but is held in special storage tanks when the ship is close to land, in port, or other sensitive environments.

 

It's a complex process, but necessary in order to ensure the health of cruise ship passengers and the natural environment.

 

Drink up!

A bit of an error there on the process.

The so-called "mineralization plant" which adds those "healthy minerals" is not quite the way it works.

The engineers are not too worried about the levels of "healthy minerals" you are consuming.

They are really worried about the ship's piping system.

Pure water without minerals will leech the metallic ions out of the ship's pipes.

This dramatically shortens the life of the pipe, causing unexpected and expensive leaks and floods.

First pH is measured, which gives a good indication of mineral content.

Adding minerals is done in 2 different fashions:

Chemical additions

Bunkering water from shore

These chemicals cost money.

Producing fresh water onboard also costs quite a bit.

If the ship is calling at a port where fresh water is of good quality and costs less than producing it onboard, the engineers save money twice.

They avoid having to add costly eminerals, as the land-based water already contains them.

They avoid having to produce so much water at higher cost.

The land-based water is first tested, then mixed with the water made onboard. This produces a blend that contains enough minerals to save the pipes.

All potable water is further sanitized using 2 different systems:

High intensity untraviolet light.

Addition of Bromine and Chlorine to USPH specifications.

An additional sanitizing process is carried out on a weekly and monthly basis:

Super chlorination of all shower heads, water taps, and swimming pool/jacuzzi pumps and piping systems.

It just occured to me to ask this question...then....

The water tastes a bit chemically/clorinated, what can you do to make it taste better?

I heard soem drop in a lime or lemon.

But..what about drops of some kind, add your own powered mix of fruit juices....? I swear the smeel and taste of the water (although C L E A N) its very heavy, you know? Anyone ever tired to make it taste better...?

Just a splash of distilled malted barley from Scotland always does the trick for me.

The water tastes great after that.

Bromine and Chlorine evaporate rather quickly.

If you let a container of ship's tap water stand for a few hours, the taste improves.

The same will happen if you let a container of ship's ice melt overnight.

Actually, they throw a giant one of them sham-wows overboard. It is tied to a rope. It absorbs over ten times it's weight in water. They then haul it back on board. They wring out the sham-wow over a bucket, saving the water and the impurities stay in the sham-wow. They do this several times an hour, until the sham-wow needs washing. Then they replace the sham-wow with a new one and start the process over again.:D

They better make sure that they wring out the sham-wow far away from where the extension cord is plugged in that is connected to the outlet back at the embarkation port that supplies the ship's electricity. Otherwise some poor soul could get electricuted.

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They better make sure that they wring out the sham-wow far away from where the extension cord is plugged in that is connected to the outlet back at the embarkation port that supplies the ship's electricity. Otherwise some poor soul could get electricuted.

 

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This thread is 7 years old. :o

Brucemuzz knows of what he speaks....and he should given his career working on ships :). But there is an irony to the entire process. A lot of money is spent engineering, installing, maintaining, and testing these water purification systems. And in the final analysis it is cheaper to simply "bunker" water (this means buying it at a port and having it pumped aboard). Go figure. The process of bunkering water is thousands of years old and still the most efficient (cost wise) method.

Hank

Brucemuzz knows of what he speaks....and he should given his career working on ships :). But there is an irony to the entire process. A lot of money is spent engineering, installing, maintaining, and testing these water purification systems. And in the final analysis it is cheaper to simply "bunker" water (this means buying it at a port and having it pumped aboard). Go figure. The process of bunkering water is thousands of years old and still the most efficient (cost wise) method.

 

 

 

Hank

I, like everybody else, have heard that water produced onboard is as safe, if not safer than your local drinking water and since some of this water may be 'bunkered' ( which, I'll admit, I didn't know they did, but it makes sense) say a Florida port, Me wonders, if those bunker tanks aboard cruise ships are cleaned to prevent any micro bacterial nasties that might cling in them. Or is this bunker water checked before it's mixed with water produced onboard ? I worked for a major airline for almost 30 years and heard that even though they used local drinking water for the passengers and crew, the tanks HAD to be 'cleaned' ever so often. Just wondering ? Sorry, if I sound like an ignorant landlubber. :)

Mac

Brucemuzz knows of what he speaks....and he should given his career working on ships :). But there is an irony to the entire process. A lot of money is spent engineering, installing, maintaining, and testing these water purification systems. And in the final analysis it is cheaper to simply "bunker" water (this means buying it at a port and having it pumped aboard). Go figure. The process of bunkering water is thousands of years old and still the most efficient (cost wise) method.

 

Hank

Since someone has resurrected this old thread, I'll weigh in. It's not quite correct, Hank, that bunkering water is cheaper than producing it onboard. The heat used to boil the water in the flash evaporators comes from the cooling water of the diesel engines, and if not used to boil water, would be rejected to the sea through heat exchangers, so this energy is "free". The other problem with bunkered water is segregation, which I will touch on below. Ships generally don't bunker water in port unless the itinerary does not allow sufficient time at sea to produce all the water needed for the voyage. Water making is prohibited when within 12 miles of land.

I, like everybody else, have heard that water produced onboard is as safe, if not safer than your local drinking water and since some of this water may be 'bunkered' ( which, I'll admit, I didn't know they did, but it makes sense) say a Florida port, Me wonders, if those bunker tanks aboard cruise ships are cleaned to prevent any micro bacterial nasties that might cling in them. Or is this bunker water checked before it's mixed with water produced onboard ? I worked for a major airline for almost 30 years and heard that even though they used local drinking water for the passengers and crew, the tanks HAD to be 'cleaned' ever so often. Just wondering ? Sorry, if I sound like an ignorant landlubber. :)

 

Mac

Cruise ships calling on US ports must meet USPH requirements when it comes to potable water sourcing, production, storage, and sanitation.

Water tanks are coated with epoxy coatings specifically made for potable water tanks. Any time the tanks are opened for inspection, there is a sanitizing process using 100ppm bleach solutions to be done prior to the tank being returned to service.

Water produced onboard is chlorinated to 4-5ppm as it travels to the storage tanks, so the water in the tanks has a residual chlorine content that keeps bacterial growth from forming.

Water bunkered from shore must meet several requirements before it can be used.

1. The individual hydrant the water is taken from, not just the municipal source, must have been tested for coliform bacteria within the last month, with negative results.

2. The hoses used must be used only for potable water, must be stored in special cabinets and with their ends capped, and before use, the hose ends must be sanitized in 100ppm bleach, and each hose connection must be raised off the ground.

3. The water is chlorinated to 4-5ppm as it travels to the storage tanks

4. The water bunkered in port must be kept segregated from the rest of the ship's water system, and not used, until a coliform bacteria test can be done onboard, with negative result. As these tests require 18-24 hours to complete, this can cause problems if shore water is the major source of water for the ship.

The water on a ship is recirculated, as opposed to one-way delivery like your municipal supply. So, the water is constantly moving from the storage tanks, through the pumps, to all the spaces on the ship, and what is not used returns to the storage tanks. This allows for continual monitoring and dosing of chlorine to the water. USPH requirements are that at the "farthest point from the injection point", which typically means on the ship's bridge, there will be a chlorine content meter, and this meter must always have a 0.5ppm chlorine residual concentration. This meter drives the dosing pumps down in the engine room, continually adjusting the dosage of chlorine to maintain this residual throughout the piping system.

When you want to know what is going on you ask the Cheng.....unless it is a Navy ship then ask the 1st or 2nd classes.:cool: (The cheng is usually sucking up to the skipper, division officers are usually clueless and the Cheifs are in the goat locker drinking coffee. ;))