These days, any cruise ship is like a huge city, where every detail is thought out so
that passengers feel just as comfortable as on land, only better.
You can take a shower, do the laundry, or swim in a pool.
But where does all the dirty water go?
Like any city, cruise ships produce tons of waste and sewage.
And no, they don’t throw it into the seawater – those islands of plastic get into the
oceans from the land.
First, even though the passengers don’t notice, the water supply system onboard the
ship is designed to use the water sparingly.
Aeration mechanisms fill the water coming out of the faucets and showers with air, and
as a result, less water is flowing out.
Even a gallon saved per person saves thousands of gallons a day!
And still, the average ship spends about 40-50 gallons of water per passenger every day.
It makes tons of wastewater that needs to be utilized.
Say, the world's biggest cruise ship, Harmony of the Seas, can carry about 5,500 passengers
together with 2,300 crew members.
They produce about 312,000 gallons of wastewater daily, and it all goes to the sewage system.
There are two categories for the wastewater on cruise ships: “grey” and “black”.
Greywater comes from laundry, showers, baths, and kitchens.
Blackwater comes from bathrooms.
The highest volume of wastewater comes from greywater.
It gets mixed with some of the blackwater and is sent to the bio-reactor.
First, all the solids are filtered out, and after that it goes to another tank where bacteria
are added.
They do their job by eating small waste particles and cleaning the water.
After they’re done, the liquid in the tank is already pure enough.
But it also gets cleaned with ultraviolet light.
Chlorine and other chemicals aren’t used since they’re bad for the sea’s eco system.
At the final stage, the water is analyzed for its bacteria content, and in case any
harmful microorganisms are still found, it’s sent for extra cleaning.
They say that the water that gets thrown overboard after all these procedures is still cleaner
than the ocean water.
That’s why some harbors allow its disposal into the sea within the 12-mile sanitary zone.
The solid waste that was filtered at the first stage is kept in special tanks until the ship
arrives at the harbor where it’ll be utilized.
All the ships have special tanks called “ballast tanks” that are full of water and kept down
in the ship to keep it stable.
They have to fill these tanks with seawater anyway, so why not use waste instead?
Scientists have noticed that ballast water taken from one ocean and thrown into another
is bad for the ecosystem.
The species of plankton and other sea inhabitants vary in different oceans, and the “strangers”
can start destroying the “natives”.
That’s why modern ships have special filters that clean out the plankton and fish from
the ballast water; they’re sent back to the sea, and the water is purified with antibacterial
lamps.
After that, it can be poured into another ocean without doing any harm to the ecosystem.
There’s also water on every ship that’s referred to as “technical water”, which
includes condensed water, cooling water, and boiler water.
It contains oil, and if it’s just thrown into the sea, it’d be no good for the eco
system.
That’s why it’s sent to the separator which purifies the technical water from the
oil.
The rule has it that technical water thrown into the ocean shouldn’t contain more than
0.000015 parts of oil products.
Doesn’t sound like that much, right?
Sensitive detectors measure the level of oil in the water, and if it’s even a bit higher
than what’s allowed, the water is sent for cleaning again.
After that, it can be poured into the sea.
What about other kinds of waste?
The International Maritime Organization has strict laws about utilizing waste, and they’re
perfectly eco-friendly.
There’s special staff on board every ship who sort out the garbage into 4 categories
– food waste, paper, metal and glass, and plastic.
So, a tea bag should be divided into 3 waste categories: the bag itself and the string
would go to the paper, tea leaves are food waste, the staple holding the string to the
bag – to metal.
Imagine how many tea bags they have to sort out on the Harmony of the Seas!
5,500 passengers can have tea once or twice daily.
Now you know who real superheroes are!
Most of the food waste is considered natural: it doesn’t do any harm to the sea’s ecosystem.
Marine inhabitants are happy to finish up what passengers have thrown out.
Big food waste is chopped into small pieces in a special machine.
Say, if you fill the 6.5 gallon container with chicken bones, bread loaves and tangerine
peels, you’ll get less than 1 gallon of dry, small chips that your aquarium fish would
eat with pleasure.
The only rule about food waste refers to the distance from the land where the ship can
throw it into water.
It can be thrown overboard beyond a 12-mile sanitary zone.
Household waste, cooking grease, and solid waste are kept on board until the ship arrives
at the harbor and is utilized there.
Paper waste goes to a special stove where it gets burned.
Metal and glass are just thrown overboard.
Surprised?
These two just drop to the bottom and do no harm to the sea.
They get polished by the water for years and then turn into the beautiful smooth pieces
that you sometimes find on the shore.
The rules about the distance from the land where metal and glass can be thrown are stricter
though.
In the Mediterranean Sea, it’s not allowed to throw them overboard at all.
All the plastic used onboard during the cruise is kept there until the ship arrives at a
harbor.
To make the process of disposal faster and easier they use a special machine that presses
all the plastic waste into blocks.
Strict rules also apply to the passengers themselves.
On every deck of a cruise ship, there are usually special instructions that forbid them
from throwing anything overboard themselves.
And by the way, where does all the water on the ship come from?
They can’t take along all the freshwater used for drinking, cooking, and washing before
departure, right?
Turns out, all cruise ships have desalinating plants.
When the ship goes farther than 25 miles from the land, they take seawater, which goes through
a many-layered filter, a powerful ultra-violet lamp, and a desalinator.
The final step is the mineralizer – a huge tank filled with all the useful minerals that
freshwater usually contains.
After that, it goes under the ultraviolet lamp again and – presto!
It can be used for drinking.
The desalinating plant is the size of a room and gives enough fresh water for all the passengers
and crew.
That’s about 40-50 gallons per person a day, remember?
Do you know any other interesting facts about cruise ships?
Let me know down in the comments!
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