What happens after you flush the toilet on a cruise ship?

this ship here has a capacity for 1,300 passengers and 800 crew by modern standards it's a small ship the largest ones are pushing up to 9,000 people now so we'd be talking about a population the size of Glastonbury now all those people have to actually live on the ship in nice conditions let's face it if it wasn't nice it wouldn't be possible for the cruise lines to actually set up in cabins they expect to be clean to be able to wash their clothes and it goes without saying they expect the basics like showers and toilets all these facilities use water may not seem much individually but it soon adds up if I tell you that the average person we use 40 to 50 gallons of water per day you can start to see the issue even on this small ship you'll be looking at a hundred thousand gallons of water everyday as pushing 500 tons of water you look at the classic Southampton New York run about six days even a small ship will have produced almost 3,000 tons of wastewater now contrary to popular belief ships don't just empty this water into the sea this is little convention from the IMO that's called Marple which deals with marine pollution and restricts the discharges that ships are allowed to make first off we need to collect it all together and that's easy enough across the bottom of the hull there are loads of ballast tanks normally you would fill them with seawater to add weight into the bottom of the ship simply for stability reasons more weight down load generally means a more stable ship but actually that weight doesn't need to be sea water you can just as easily fill them with the waste water please produced on board so now you don't just pick a random tank and collect all the waste water together in much the same way as you separate paper and metals in household recycling we separate waste water onboard who actually use two categories of green water in black water the difference between the two is in the bacteria that's present in each black water which is waste from many toilets has come into contact with solid waste and contains far more harmful components grey water on the other hand is things like waste water from showers and laundries it's a sort of water that some environmentally friendly homes would collect and reuse for example when you're flushing toilets with old bath water things like that so now you have a tank and rapidly filling out with black water or more sewage as it's commonly known what on earth can you actually do with it unsure it all goes to sewage treatment plants and actually on a ship the exact same thing happens albeit on a slightly smaller scale down in the engine room you'll actually find a full blown sewage treatment facility let's break it down and have a look at how it works as sewage enters the system first passes through this filter all this does is skim off anything particularly large from there it passes into the next chamber the aeration chamber this chamber is actually filled with aerobic bacteria aerobic just means the bacteria needs oxygen to be able to survive if we were to just dump all the sewage in here the bacteria would soon use up their oxygen so we actually use air blowers to give them a constant supply with oxygen and the sewage is a food source the bacteria set to work all this is is is just an accelerated form of decomposition remember these bacteria are all alive this is why ships are so careful with the chemicals they use in their toilets the last thing they want is to go and kill all these helpful bacteria by accident so now our little friends have digested all the sewage is on to the next stage and this is the settlement chamber it's a bit like a cocktail that you've left out for too long you know where it separates out into layers in our case the dense heavy material sinks to the bottom and the water floats to the top it's easy enough to deal with the dense stuff you can actually just send it back to the beginning and you kind of keep cycling it through the bacteria and so they've eaten through all they can saying that at some point it will become so dense that you gets caught in the filters and then it can be removed and either sent for incineration or landed ashore the fluid stuff at the top which by this stage is practically just water then gets liquid into the final treatment chamber and this final treatment is just sterilization could be chlorination like we use in a swimming pool or it could be another high-tech method like UV treatment basically we're just making sure that the last of the harmful bacteria is gone finally we're left with a result there's water that's perfectly safe it's actually safer than some drinking water of course on ships we don't send it for drinking we actually just send it to another storage tank where it can wait until the ship is in a geographical area where is allowed to discharge so that's the Blackwater but what about the grey water well that doesn't actually need to pass through the sewage treatment plant at all some plants do add great water and process it along with the black but not all by any means one issue in particular is that is far harder to control the chemicals that people use in showers and the sinks you wouldn't want your shampoo killing off all the little workers down in the treatment plant as far as I'm aware there's no requirement to treat great water at all because it doesn't contain those harmful bacteria that are found in raw sewage of course simple filtration is used to remove anything large that shouldn't be in there but even so treatment of grey water is usually minimal most ships will simply discharge it when they're far enough away from land saying that they're a growing number of geographical areas that do now prohibit or at least limit gray water discharge one particular area of note is Alaska where there have been a few high-profile prosecution's for breaching their limits I always find it fascinating that when wastewater finally comes to be discharged what started out as the most harmful black water actually enters the sea is the cleanest practically fresh water so next time you take a cruise spare a thought for all those little bacteria are working away in the bowels of the ship digesting everything you send them hopefully you've enjoyed today's topic for more like this every other Friday be sure to hit that subscribe button until next time thank you for watching and good bye

Channel: Casual Navigation

Views: 4,820,456

Keywords: casual navigator, marine, uscg, shipping, casual navigation, maritime explaination, merchant navy, sailing, marine animation, cruise ship toilet, marine sewage treatment plant, marine sewage treatment plant process animation, marine sewage system, cruise ship sewage system, cruise ship sewage treatment, cruise ship sewage disposal

Id: 5Z7bTmZVPTI

Length: 6min 11sec (371 seconds)

Published: Fri Jul 12 2019

Reddit Comments

[u/itzarel]

Interesting however it should be noted, grey water contains a lot of phosphorus and other chemicals that are far from ideal for the ecosystems of the sea. Cruise ships are pollution powerhouses.

[u/[deleted]]

"The average person uses 40-50 gallons of water everday."

Where on God's green earth did he get that statistic?!!?

[u/Britavit]

I thought that was what the porthole was for?