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! Hey, if you learned something new today, then
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