The toilet flushes. You wash your hands. You go on with your day at sea aboard your favourite
cruise ship. Most of the time we don’t think about what happens to our waste once we’ve flushed it.
We just assume there are systems in place to deal with it,
and we’re grateful that it’s not our job to worry about it.
But on a ship, there’s thousands of flushes per
day. So someone has to deal with it… so what do they do with all the poo?
Passenger ships today come in many different shapes and sizes,
with total capacities that range from a handful of people to thousands of people on a single ship.
But when there are that many people on board,
and no access to land-based infrastructure, the ship has to operate as its own entity.
A cruise ship has to produce enough energy, clean water and heating and cooling to keep everybody on
board safe and comfortable. It also has to deal with the waste produced by all those people on
board. Both food and packaging waste, and also waste water, which we’ll investigate today.
Hello and welcome back to my channel…if you don’t
know me my name is Chris Frame & I’m a maritime history author and lecturer,
I speak on board cruise ships and at maritime museums around the world. I am also the co host
of The Big Cruise Podcast, you can find all the details in the description below.
[SHIPS BELL DING]
In the early days of steam ships, waste was simply thrown overboard. This sounds
appalling by today’s standards, but it wasn’t quite the environmental disaster it would
be if we were still doing it today. Keep in mind, in the 1830s and 1840s, the passenger
capacity on steam ships was much lower, and the wastewater produced per person was also lower.
There were no flushable toilets on the first steamers, and sewage
was often handled using toilets that were manually emptied, as well as chamber pots.
Bathing was limited, so the amount of wastewater being produced was far lower than today.
Microplastics didn’t exist back then, nor did many of the chemicals that we use today to wash,
clean and bathe in. Many of these chemicals are devastating for ocean environments…
As time went on, and the passenger amenities onboard improved… nothing
much changed so far as the sewage was concerned,
at least for several decades. While the behaviour of discharging water into the sea didn’t change,
the method of dumping waste was ... upgraded – for want of a better phrase.
From the late 19th century, liners started to pump wastewater out of the ship,
rather than having it tipped over the side… and while this made it less visible,
it was still, in essence, just being thrown overboard.
If we look at a ship like Titanic – renowned for being one of the finest
liners of her time – we can see just how different things were in the early 20th
century. The ship’s passengers and crew were estimated to produce around a ton of
sewage every day – through the many toilets, wash basins and bathrooms aboard the ship.
However aboard Titanic, the sewers drained directly out through holes on the side of
the ship into the ocean. These holes were located just above the waterline and were
almost constantly discharging sewage and other dirty water directly into the sea.
This system was not-adjustable – meaning that the sewage left the ship untreated whether it
was at sea, or in port… But this couldn’t go on forever, as environmental awareness
expanded there were efforts made to improve the waste storage and discharge process on ships.
Today, modern cruise ships feature advanced water-treatment systems on board. These are
like the water treatment plants that are found in many cities,
only scaled down to fit into a cruise ship.
This is important due to the scale of cruising today. For example, each week, each of the largest
cruise ships – such as the Oasis-Class from Royal Caribbean – are estimated to create some 210,000
gallons of sewage – referred to as black water… that’s 794,000 litres! They also make over a
million gallons, or 3.7 million litres of grey water – which includes laundry water,
water from the sinks and the showers and so on. If this all went directly into the sea,
untreated, as in the days of old, it would be an environmental disaster on a massive scale!
Today, the treatment and discharge of wastewater is governed by MARPOL,
an International Maritime Organisation regulation. It restricts where ships
can discharge treated water, and what levels of treatment, ships must adhere to.
While there have been instances of cruise ship’s breaching these regulations, the vast
majority of cruise ships closely follow these regulations – not doing so attracts heavy fines
and terrible public relations damage, as we’ve seen in the past when breaches have occurred.
So back aboard the ship, when the toilets are flushed, or water from showers and sinks and
laundry's are used, the used water is sent to ballast tanks at the bottom of the ship.
The black water is kept separate from the grey water; with the black water being sent through
a significant treatment process, while the grey water receives less attention.
The black water is sent to the sewage treatment facility, located near the ship’s engine room.
Here it is skimmed – to remove any of the larger obstacles. After this, it is sent to
an oxygen rich bacteria tank. The bacteria speeds up the decomposition of the sewage.
Following this, it’s sent to a settlement tank;
that allows any heavy items that have got through to this stage to settle at the bottom while the
lighter, cleaner water is syphoned off to be sterilised – using UV treatment, or chlorine.
At the end of this process, the water is sent to another storage tank. It is then discharged
when the ship is in an area outside of restricted zones, as defined by MARPOL and local regulations.
So, what about the grey water? This water – such as your shower and sink water,
is given a lighter treatment. Many ships skim this water to remove the obstacles, however because it
doesn’t contain the dangerous bacteria as found in raw sewage, grey water is not required to be
treated with the same rigour as black water. It is generally stored, and also discharged when the
ship is in a geographical area that allows it. This practice does cause some concern,
because although there are none of the harmful sewage-related bacteria, this water does contain
microplastics, and chemicals such as that from shampoos and conditioners – and many areas
around the world are tightening up discharge restrictions to protect natural environments.
So there you have it… next time you’re at sea you’ll have a bit
more appreciation as to what happens when you press flush.
If you’re concerned about the environmental impact of greywater you produce, consider swapping to
environmentally friendly cleaning products, such as soaps and shampoos that don’t contain
harmful chemicals such as sulphates and parabens – there are plenty of options available these days.
Thanks so much for watching and I hope you found the video interesting. If you did you
might enjoy my how ships work playlist, and until next time I hope to ‘sea’ you on board.