Where Do Cruise Ships Dump Waste and Sewage?

Eric DawsonByEric Dawson Boats & Cruises

Cruise ships discharge treated sewage and graywater into marine waters, answering the question: where does cruise ships dump waste? Discharge conditions depend on the waste involved and the rules governing the waters where the ship operates.

More than 230 cruise ships operate worldwide, and the 2008 Cruise Ship Discharge Assessment Report examines five different cruise ship discharges (Environmental Protection Agency). Waste streams include toilet sewage, graywater, oily bilge water, ballast water, and solid waste.

What Happens to Cruise Ship Toilet Waste?

Cruise ship toilet waste passes through onboard wastewater treatment, with treated water stored onboard or discharged at sea under applicable rules. Disposal depends on the waters where the ship operates, including local restrictions and areas that prohibit discharge.

Advanced wastewater treatment uses physical, chemical, and biological processes. Systems capable of meeting or exceeding international sewage-discharge standards operate on 249 member ships, representing 86% of global passenger capacity, according to Cruise Lines International Association (CLIA). Additional treatment technologies include ozonation, reverse osmosis, and ultraviolet disinfection.

Royal Caribbean’s onboard treatment provides an example of the route from sewage cleaning to storage. Cleaned sewage enters a disinfection chamber, where ultraviolet radiation targets remaining pathogens. Water then moves into a storage tank before its eventual disposal, rather than passing directly from passenger toilets into the ocean.

  1. Process sewage through the onboard wastewater treatment system.
  2. Disinfect cleaned wastewater with ultraviolet radiation in the treatment sequence outlined here.
  3. Move the treated water into a storage tank.
  4. Keep wastewater onboard or discharge it at sea where applicable rules permit.

Discharge permission involves both the ship’s position and the rules governing that location. Applicable local and international requirements determine the distance from land for releasing treated wastewater. Areas that prohibit discharge require a different handling decision from waters where release is permitted.

Residual biomass is another output of onboard wastewater treatment. Treatment can turn that material into biosolids, a nutrient-rich organic byproduct used as a soil amendment. Liquid effluent and the biomass left by treatment therefore follow distinct processing routes within the wastewater-management account provided by CLIA.

Wastewater sampling has examined actual cruise ship operations in Alaska. Four ships operating there were sampled during the summer of 2005 by the Environmental Protection Agency (EPA). Separate sampling also covered vessels operating in Alaskan waters during the preceding summer, extending the examination beyond a single operating season.

Onboard equipment was also the subject of an EPA questionnaire distributed in 2004. Ships authorized to carry 500 or more passengers that operated in Alaska received questions about sewage and graywater treatment devices. That survey focused on the equipment handling wastewater, rather than only examining water after its release.

Where Does Cruise Ships Dump Waste by Waste Type?

Waste types require separate discussions. Different materials therefore belong in separate discussions of cruise ship waste disposal.

Symphony of the Seas provides a ship-specific comparison of wastewater volumes over a voyage, with graywater accounting for the larger reported quantity. Black water and graywater appear separately in the table because they represent different waste streams, not different names for the same material. Weekly quantities refer to a one-week cruise, as reported by Royal Caribbean Blog.

Ship Waste Stream Reported Volume Period
Symphony of the Seas Black water 210,000 gallons One-week cruise
Symphony of the Seas Graywater 1 million gallons One-week cruise

Graywater includes water from showers, sinks, laundries, and dishwashers, distinguishing it from toilet-related sewage. Both streams were included in the EPA examination of treated wastewater released by docked cruise ships in Alaska. Discharge studies addressed the behavior of wastewater after release, including how it diluted in surrounding water near the vessels.

Plastic waste aboard Symphony of the Seas is handled with equipment that includes an onboard incinerator and compactor. Compaction crushes approximately 528 gallons of water bottles, making this a concrete example of onboard handling for a solid material rather than wastewater. Equipment descriptions apply to that vessel, while the water-volume comparison concerns separate onboard waste streams.

Oily bilge water belongs to the EPA’s cruise-ship discharge categories alongside ballast water and solid waste. Sewage-focused descriptions of shipboard waste therefore address only part of the material generated during a voyage. Ballast water has its own place in that classification, separate from both wastewater categories associated with passenger toilets and other onboard water use.

Wastewater sampling covered four cruise ships operating in Alaska during the summer of 2005. In 2004, another EPA effort distributed a questionnaire to those vessels. Treatment devices and discharge behavior were distinct subjects within the agency’s work on cruise-ship wastewater.

Cruise-ship discharge oversight also involved public hearings held by the EPA, the U.S. Coast Guard, and other federal agencies in Los Angeles, Juneau, and Miami. Offshore plume tracking formed another part of the agency’s examination of discharged wastewater. Together, these activities addressed cruise discharges through vessel surveys, water sampling, observation of dilution, and public hearings.

Do Cruise Ships Dump Sewage Without Treatment?

Cruise ships belonging to CLIA must not discharge untreated sewage anywhere worldwide during normal operations, under the association’s mandatory membership policy. Discharge permissions depend on the applicable rules governing a vessel’s waters.

CLIA’s sewage commitment applies to member ships and specifies normal operations. Membership requirements address how participating operators handle wastewater, while local and international rules govern discharge locations and conditions. Some areas prohibit wastewater discharge, and treated wastewater can be retained onboard rather than released at sea.

Advanced wastewater treatment systems are installed on member ships. Those systems are described as capable of meeting or exceeding the sewage discharge standards of the International Maritime Organization’s International Convention for the Prevention of Pollution from Ships (MARPOL), Annex IV.

Onboard advanced treatment uses these processes to process wastewater. Residual biomass from wastewater treatment can be processed into biosolids, a nutrient-rich organic byproduct used as a soil amendment.

Baltic Sea Special Area standards provide another benchmark within the association’s wastewater reporting: more than 40% of reporting member vessels meet those standards. The association also describes its members’ wastewater policies as exceeding regulatory requirements. Both commitments form part of its broader account of wastewater management aboard participating cruise ships.

During the summer of 2005, the U.S. EPA sampled wastewater from four ships operating there. A separate survey distributed in 2004 addressed sewage and graywater treatment devices aboard Alaska cruise vessels.

EPA discharge investigations also examined how treated effluent diluted after entering surrounding waters. During July 2008, a Skagway Harbor study used Rhodamine WT fluorescent dye in treated effluent to track dilution near docked ships. Offshore plume tracking examined dilution at sea, while public hearings on cruise discharges took place in Los Angeles, Juneau, and Miami.

How Is Graywater Different from Sewage?

Graywater comes from showers, sinks, laundries, and dishwashers, while sewage is toilet-related wastewater. Cruise ship toilet waste therefore belongs to a different waste stream from water draining from bathrooms, laundry facilities, and kitchens. The EPA lists graywater and sewage separately when identifying cruise ship discharges.

Daily wastewater estimates describe a particular ship size rather than a fixed output for every voyage. An average-sized cruise ship carrying 3,000 passengers and crew produces an estimated 255,000 gallons of graywater and 30,000 gallons of sewage daily, according to Oceana. Both estimates refer to the same onboard population and daily period.

Treated graywater has also been examined alongside treated sewage during discharge studies. The harbor work examined effluent from six docked cruise ships. Investigators tracked its dilution near the vessels.

Offshore wastewater discharges were the subject of a separate EPA plume-tracking survey. That work examined dilution in offshore waters, adding a different operating setting to the harbor investigations. Graywater was consequently part of cruise wastewater assessment, not simply a category of water associated with onboard washing.

How Does Cruise Ship Garbage Disposal Work?

Cruise ship garbage disposal includes onboard compaction, incineration, and recycling, while prepared food that goes uneaten follows a separate disposal route. Solid and hazardous waste includes plastics, batteries, medical waste, and toxic chemicals, alongside discarded food.

Symphony of the Seas provides a ship-specific example of equipment used to handle plastic waste: an onboard incinerator and compactor. Bottle compaction aboard the ship handles approximately 528 gallons of water bottles; Royal Caribbean recycled 43.7 million pounds of waste in 2018, Royal Caribbean Blog reports.

Prepared but uneaten food can be ground up, mixed with water, liquefied using an industrial grinder, and discharged at sea. Food disposal through that process is distinct from the onboard handling of bottles and other trash.

Other waste streams require separate handling. Bilge water collects at the bottom of a vessel and includes oils released by equipment in engine compartments.

What Did EPA Studies Find About Cruise Discharges?

EPA studies examined cruise-ship wastewater and how treated discharges diluted in harbor and offshore waters. Alaska fieldwork included wastewater sampling and dye testing near docked vessels, with separate surveys examining treatment equipment and tracking offshore discharge plumes.

Public hearings in 2000 brought cruise-ship discharges before federal agencies in Los Angeles, Juneau, and Miami. Participants included the U.S. Coast Guard and other federal agencies alongside the environmental regulator. Cruise ship waste disposal was therefore addressed through public hearings as well as vessel sampling and field surveys.

Offshore plume tracking followed in 2001, when investigators conducted a survey to study the dilution of cruise-ship discharges. Dilution in offshore waters was the focus of that work, distinguishing its setting from the later harbor testing conducted alongside docked ships.

Nitrogen compounds were the subject of the latter sampling report. Separate sampling reports also covered four cruise ships operating in Alaska during the first summer.

Treatment-device information was collected through a questionnaire distributed in 2004 to all cruise ships authorized to carry 500 or more passengers that operated in Alaska. Questions addressed sewage and graywater treatment devices, making onboard equipment a specific subject of the survey alongside the agency’s wastewater sampling activities.

Skagway Harbor, Alaska, hosted near-field dilution testing in July 2008 involving six docked cruise ships. Investigators examined treated sewage and graywater discharged from those vessels.

Cruise Ship Discharge Assessment Report brought five different cruise-ship discharge categories into an overarching assessment. Its scope extended across multiple waste streams, while the individual field studies concentrated on particular sampling locations, wastewater characteristics, treatment devices, or discharge dilution.

Roundups that cite a roundup are among my least favorite reading habits, mostly because each retelling can quietly sand off the conditions that matter. For EPA’s cruise-discharge findings, I would check the Cruise Ship Discharge Assessment Report itself and keep its categories, sampling, and near-field dilution testing attached to the conclusion.

What Do Wastewater Treatment Claims Actually Cover?

Wastewater treatment claims cover equipment capabilities, the share of the fleet equipped with those systems, and industry membership commitments. CLIA reports broad member fleet coverage by advanced systems. Both figures describe the reach of equipment across the member fleet.

Passenger capacity is the measure attached to that coverage percentage, while the ship count identifies vessels carrying advanced wastewater treatment systems. Separately, more than 40% of reporting CLIA member vessels meet Baltic Sea Special Area standards. Reporting vessels form the group counted for that standards claim, rather than passenger capacity.

These systems use multiple treatment methods. Additional technologies identified in the industry account include ozonation, reverse osmosis, and ultraviolet disinfection. Equipment capability is the subject of these descriptions, with individual technologies contributing to the overall treatment process.

Membership commitments address operating policies as well as onboard equipment. Global wastewater policies cover both black water and graywater, and CLIA describes those policies as exceeding regulatory requirements. Compliance commitments and treatment technology are separate parts of the industry’s account of cruise ship waste disposal.

Residual biomass is another part of wastewater handling to consider when reading a cruise line’s environmental description, alongside its discussion of water treatment. For a practical question about treatment byproducts, ask how the ship handles its residual biomass.

Frequently Asked Questions

How Do Cruise Ships Dispose of Human Waste?

Cruise ships belonging to CLIA must not discharge untreated sewage anywhere during normal operations, under the association’s membership policy.

Where Does Poop and Pee Go After a Cruise Ship Toilet Is Flushed?

Cruise ship sewage enters a disinfection chamber where ultraviolet radiation targets remaining pathogens in the treatment sequence described by Royal Caribbean Blog.

Is Every Kind of Cruise Ship Waste Dumped into the Ocean?

Cruise ship trash cannot legally be dumped into the ocean, according to Friends of the Earth.

References

Sources read in September 2026.

Eric Dawson

I'm Eric Dawson, and I write The Money Watch from north Columbus, Ohio. Most of what I cover comes from my own life: renting, a 2014 Honda Fit, parking, computers, food and the bills behind all of it. I spent four years in an apartment-property office and eleven on a distributor's operations desk, reading leases and invoices. Where you need real information, I research the maker's or agency's own page and independent sources and report what they publish. I don't give tax, investment, legal or medical advice.