What Do Cruise Ships Do with Sewage and Waste?

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Have you ever wondered what do cruise ships do with sewage? If you have ever wanted to know, we have all of the answers. Read on for the truth!    

When most people think of a cruise vacation, they immediately picture beautiful views of open water, relaxation, luxury, and exciting amenities. What is often ignored is how these massive vessels deal with the immense amount of sewage and waste produced during their lengthy voyages.

If you have ever wondered what cruise ships do with sewage, we have all of the answers. We will explain how modern-day cruise ships handle human waste and other forms of sewage while they are at sea and how these enormous ships deal with garbage and recycling. While it may not be the most glamorous topic, having a clean, odor-free experience is essential for cruise passengers and crew members alike.

If you are ready to learn, here is how cruise ships ensure that they handle sewage safely and responsibly!

What Types of Sewage Do Cruise Ships Deal With & What Do They Do With It All?

Before we dive into the ways that cruise ships handle and dispose of sewage, it is helpful to quickly explain the different types of waste generated during a voyage.

Non-Human Solid Waste

While flushing toilets, running taps, and shower drains all result in significant amounts of human waste and wastewater, they are not the only forms of sewage that can build up while a cruise ship is on the water.

Kitchen waste, specifically food scraps and unfinished beverages, can quickly become an issue on a lengthy cruise with a high number of passengers and crew members. If not stored and dealt with properly, this type of waste can begin to biodegrade, resulting in unpleasant odors and even a buildup of flammable gases.

Even non-odorous solid waste, like scrap paper and plastic, must be dealt with appropriately, or else the ship would quickly become overwhelmed with unsightly messes.

What Do Cruise Ships Do With This Type of Waste?

To overcome this issue, waste is segregated and dehydrated. Any form of waste that can be recycled, such as reusable plastics, glass containers, and metal cans, are all cleaned and stored, so they can be recycled and repurposed when the ship reaches land and the appropriate recycling facilities.

Truck Collecting Cruise Ship Waste
Truck Collecting Cruise Ship Waste (Photo Credit: Darryl Brooks / Shutterstock)

Non-recyclable, organic waste is dehydrated, and then it is incinerated. This is the most environmentally-friendly way to deal with this waste while the ship is at sea. If the ship is in port, the waste can be collected by local waste management services.

For more information about how cruise ships are now using advanced technologies to handle waste at sea, read up on how the Carnival Corporation is investing millions of dollars in food waste biodigesters.

Non-Human Liquid Waste

Wastewater not linked to human waste is often called grey water within the cruise industry. This water can come from washing dishes in the ship’s kitchens, the ship’s laundry facilities, and water used by the cleaning staff to mop floors, sinks, and clean other surfaces. Since this water can contain non-biodegradable debris, chemical cleaning agents, and detergents, it cannot simply be released overboard.

What Is Done With This Type of Wastewater?

This type of wastewater is usually filtered and treated onboard the ship because modern cruise ships have sophisticated water treatment facilities. Settlement tanks, a range of filters, chemical treatments, and various water quality tests are performed on the so-called grey water, as this ensures that the water is free from all harmful contaminants.

Garbage Disposal Area on Cruise Ship
Garbage Disposal Area on Cruise Ship (Photo Credit: Mohd Syis Zulkipli / Shutterstock)

Once fully treated, this type of non-sewage wastewater can be discharged into some regions of the ocean. While this may sound like it would be harmful towards the environment, the water must meet stringent regulatory standards before dumping can begin. Essentially, the water must be completely clean and pose no serious risk to the health of local marine life and ecosystems. 

Human Waste and Sewage

Given how many passengers and crew members travel on a large-scale cruise ship, it is incredibly important that they handle human waste correctly. Human waste can refer to water that results from flushing toilets and water collected by cabin showers and other bathing facilities on the ship.

Cabin Toilet on a Cruise
Cabin Toilet on a Cruise (Photo Credit: Solarisys / Shutterstock)

This particular type of waste is also known as black water. Due to the health risks associated with it and the unpleasant odors that go with human waste, this form of sewage must be dealt with properly.

What Is Done With This Type of Wastewater and Sewage?

All forms of human waste have to undergo an extremely rigorous treatment process within areas of the ship that are off-limits to all passengers. In addition to heavy filtration, these modern sewage treatment facilities use chemical treatments and biological composting procedures. 

Throughout the process, the treated and untreated sewage is stored in airtight holding tanks, which helps with odor control. These holding tanks are also incredibly durable, and they are regularly checked for leaks and weak spots, as maintaining their structural integrity is essential for the health and safety of all onboard the ship.

Once the sewage has been treated and is no longer a biological concern, clean and tested water can be released from the ship into designated bodies of water. Dehydrated solid waste is kept until the ship can dispose of it correctly on land.

Some of the larger cruise ships also have incineration facilities that can deal with treated solid waste at high temperatures, reducing its volume and completely sterilizing it.

If the ship is in port when the treated sewage is ready for discharge, it is passed off to the local water treatment facilities to be processed even further.

What Types of Regulations Govern How Cruise Ships Dispose of Sewage?

To ensure that all cruise ships adhere to proper sewage treatment and disposal procedures, it is essential that the industry is regulated. 

To protect marine life and the environment, the entire cruise ship industry has to follow the rules regarding sewage disposal. The International Maritime Organization (IMO) is one of the most stringent regarding regulations regarding how cruise ships hold and release sewage and other forms of waste.

When cruise ships are within waters belonging to a particular nation, they must also adhere to that country’s specific rules and regulations regarding waste and sewage treatment. For example, if a cruise ship travels through American waters, the cruise ship must adhere to rules set out by the United States Environmental Protection Agency (EPA).

Cruise Ship Garbage
Cruise Ship Garbage (Photo Credit: savas_bozkaya / Shutterstock)

While these national agencies can set different standards and rules, most are fairly clear on how sewage must be treated and how it must be disposed of and discharged.

In addition to strict treatment standards, these powerful organizations also dictate where waste can be released, even after it has been treated.

Most do not allow cruise ships to discharge waste anywhere near the nation’s shores, so all waste must be treated, then delivered to local waste treatment systems. Naturally, this also comes with a significant fee, which can be rolled into fees paid to dock a cruise ship in a local port.

Does the Cruise Industry Have its Own Rules?

Believe it or not, many cruise lines add their own environmental standards for sewage disposal that go beyond what they are legally required to do.

Icon of the Seas Sea Trials
Icon of the Seas Sea Trials (Photo Courtesy: Royal Caribbean)

Not only is this good for the cruise line’s public image, but coming up with more effective and energy-efficient treatment systems cuts down on waste and makes the entire ship more practical and sustainable.

Frequently Asked Questions (FAQs)

What is black water on a cruise ship?

Black water is a term used to describe sewage. Typically, the term is explicitly used when describing human waste or water that has been in contact with some form of human waste.

Are cruise ships allowed to release sewage anywhere? 

No, there are set regulations that specify where a cruise ship is allowed to discharge sewage. Typically, sewage cannot be released within miles of a shoreline or at shallow water depths, as it can pose a greater risk to the marine ecosystem in the area. The sewage must also be treated before it is released into the water.

What is grey water? 

Grey water is a term cruise ships use to describe wastewater that has not come in contact with human waste or any other form of biologically hazardous material. This can include water that has passed through a sink, laundry machine, or non-toilet drain.

Is the treated sewage water safe to drink?

While this water is close to drinkable, it is unsafe to do so, as drinking water needs to be vigorously tested through a certified water treatment facility. 

Have cruise ships always treated sewage water?

Sadly, cruise lines of the past did not treat water before releasing it into the sea or ocean. Fortunately, changing attitudes and strict regulations have improved how cruise ships deal with wastewater and sewage.

Final Words

How cruise ships treat and dispose of sewage has come a long way. Cruise ships now use a complex sewage treatment process that helps limit the environmental impact of carrying so much waste at sea.

Read Also: What Is on the Lowest Deck on a Ship?

Thanks to advanced technologies, high standards, and government regulations, cruise ships deal with sewage sustainably and professionally, protecting passengers, crew members, and the waters that cruise ships travel through.

Emrys Thakkar
Emrys Thakkar
The founder of Cruise Hive which was established in 2008 as one of the earliest cruise blogs in the industry. Emrys has been reporting on the latest cruise industry news since the site first launched. Expert insights and tips featured on a number of publications including The Express, Business Insider, and more. Worked for Carnival Cruise Line for 8 years and is well and truly dedicated to cruising! Has also been on a number of cruises so can offer an insight into the industry that many will not be able to do. What's even more impressive is that Emrys has traveled the world by visiting more than 34 countries, lived in China for 8 years, and cruised the Caribbean, Baltic, Mediterranean, Asia, and Europe. Find out more about us here.


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