Cruise Ship Wastewater: What Happens To It? Where Does It Go? The Answer Is Surprisingly Unexpected...

Jayson R.
Mar 22
3 min read

Cruise ships carry thousands of passengers across the oceans, offering luxury and adventure. But what happens to the wastewater generated on these floating cities? Many people assume that cruise ships dump untreated waste directly into the ocean, but the reality is more complex. Some cruise lines have made serious commitments to protecting the environment by properly treating wastewater. Others operate their own treatment facilities onboard, while some, including Carnival Cruises, show inconsistent practices. This post explores how cruise ship wastewater is handled, the regulations that govern it, and the differences between newer and older vessels.

Eye-level view of cruise ship wastewater treatment facility on deck — Cruise ship wastewater treatment system on deck

What Is Cruise Ship Wastewater?

Wastewater on cruise ships comes from several sources:

Blackwater: Sewage from toilets and medical facilities.
Graywater: Water from sinks, showers, kitchens, and laundry.
Bilge water: Water mixed with oil and other contaminants from the engine room.
Other waste streams: Such as ballast water and cooling water.

Each type requires different treatment methods before disposal or discharge.

How Do Cruise Ships Treat Wastewater?

Cruise ships use onboard treatment systems designed to reduce pollutants to safe levels before releasing water into the ocean. Treatment methods include:

Biological treatment: Using bacteria to break down organic matter.
Chemical treatment: Adding disinfectants like chlorine to kill pathogens.
Filtration and sedimentation: Removing solids and particles.
Advanced systems: Some ships use membrane filtration or ultraviolet light for extra purification.

Newer ships often have state-of-the-art treatment plants that meet or exceed international standards. These systems can treat wastewater to a level comparable to municipal treatment plants on land.

Regulations Governing Cruise Ship Wastewater

International and national laws regulate how cruise ships manage wastewater:

MARPOL Annex IV: The International Convention for the Prevention of Pollution from Ships sets global standards for sewage discharge. It requires ships to treat sewage before discharge and prohibits dumping untreated sewage within 3 nautical miles of shore.
United States Clean Water Act: The U.S. enforces stricter rules for ships operating in its waters, including the requirement to use approved treatment systems.
Local regulations: Many coastal countries have their own rules, often more stringent than international ones.

Ships must follow these rules or face fines and penalties. Compliance varies depending on the cruise line and ship age and where the ship sails. The International regulation still allows for untreated wastewater discharge as long as it isn't within 3 nautical miles of shore- a topic not satisfactory to many environmentally-conscious travelers.

Differences Between Cruise Lines and Ships

Some cruise lines have invested heavily in environmental technology:

Virgin Voyages, Holland America Line, Royal Caribbean and Norwegian Cruise Line equip their newest ships with advanced wastewater treatment plants.
Carnival Cruises has faced criticism for inconsistent wastewater management. Older ships in their fleet may not have the latest treatment systems, leading to occasional pollution incidents.
Smaller cruise lines and older yachts may lack comprehensive treatment systems, increasing environmental risks.

Older ships often rely on less effective treatment or even discharge untreated waste in certain areas, while newer vessels prioritize sustainability.

Challenges and Controversies

Despite regulations, problems persist:

Illegal discharges: Some ships have been caught dumping untreated wastewater illegally.
Monitoring difficulties: Tracking pollution in open waters is challenging.
Cost of upgrades: Retrofitting older ships with modern treatment systems is expensive.
Environmental impact: Even treated wastewater can affect marine ecosystems if not properly managed.