wastewater in cruise ships

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Cruise Ship Discharges and Studies

• bilge water (water that collects in the lowest part of the ship's hull and may contain oil, grease and other contaminants)
• graywater (waste water from showers, sinks, laundries and kitchens)
• ballast water (water taken onboard or discharged from a vessel to maintain its stability)
• solid waste (food waste and garbage)

These discharges can have impacts on water quality. Impacts depend on the characteristics of the discharge (e.g., constituents present, levels of discharge) and the characteristics of the receiving waters (e.g., currents, temperature).

Work to Date on Cruise Ship Discharges

Cruise ship discharge assessment report (2008) *.

• what the waste stream is and how much is generated
• what laws apply to the waste stream
• how the waste stream is managed
• potential environmental impacts of the waste stream
• ongoing actions by the federal government to address the waste stream
• a wide range of options and alternatives to address the waste stream from cruise ships in the future

Plume dilution study (2008) *

Nitrogen compounds sampling report (2005) *

The EPA sampled wastewater from four cruise ships that operated in Alaska during the summer of 2005, to collect information on nutrients in cruise ship wastewater. 

Alaskan cruise vessel survey (2004) *

In 2004, the EPA distributed a "Survey Questionnaire to Determine the Effectiveness, Costs, and Impacts of Sewage and Graywater Treatment Devices for Large Cruise Ships Operating in Alaska" to all cruise ships authorized to carry 500 or more passengers that operated in Alaska at the time.

The final version of the survey (approved by the Office of Management and Budget), associated Federal Register notices, supporting documents and comments received can be found at   www.regulations.gov   under the EPA's docket ID: EPA-HQ-OW-2003-0081.

Sampling reports (2004) *

Plume tracking survey (2001)

The EPA conducted a plume tracking survey to study the dilution of cruise ship discharges from wastewater systems in offshore waters.

Public hearings (2000)

The EPA, together with the U.S. Coast Guard and other Federal agencies, solicited public input on the issue of cruise ship discharges during public hearings in Los Angeles, Juneau and Miami .

* For access to these reports, please submit a request through the Contact Us link at the bottom of this page.

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• Cruise Ships

How Cruise Ships Work (Part 1): Water and Waste Management

When cruise lines advertise their ships, they usually parade their most exotic travel destinations, their award-winning gourmet restaurants, their luxury cabins and lounge areas, as well as the non-stop entertainment they offer on board. We are rarely shown any photos of the plumbing system, the garbage storage and all the other service facilities that ensure that all that glamour on board stays glamorous.

Have you ever looked at one of those giant cruise ships that accommodate thousands of people and wondered, how on earth does this ship carry water for all of these people? What happens to all the disgusting sewage water? Where does all the stinky garbage go? As always,  The Shipyard  is here to answer.

All This Water and Not a Drop to Drink

The biggest cruise ship in the world, Royal Caribbean’s  Symphony of the Seas , has a capacity of 6,680 passengers, each of whom uses on average between 200 and 250 liters of water per day. For a ship this size, this is a total of 1.5 million liters of water per day, for the passengers alone. There is no way in the world a ship could store so much water on board for the duration of the journey. So where does the water for the showers, sinks, cooking, etc. come from?

Cruise ships turn sea water to drinking water. Special pumps in the hull suck the raw water in and transfer it to the ship’s desalination plant. The plants are complex systems composed of water storage tanks, pipelines, pressure tanks and pumps. Two main methods are used to create fresh water: reverse osmosis and evaporation.

In the reverse osmosis process, a pump pressurizes the seawater and forces its molecules through a semi-permeable membrane. The result is called pure water permeate. Most dissolved salts, organic compounds, bacteria and suspended solids are larger than the mesh of the membrane and are unable to pass through.

In the alternative purification process, the H2O is evaporated from the seawater in specially designed evaporators, such as the Wärtsilä Serck Como multi-stage flash (MSF) evaporators in the picture below. Heat from the engine’s cooling water (75-95 ° C) is typically used as a source of heat for the evaporation process. The resulting condensate is then processed depending on the intended use.

After the water is desalinated through either evaporation or reverse osmosis, it is further mineralized and disinfected before it can be used as drinking water. Several methods for water disinfection are used on cruise ships including chlorination, ozonation, silver-ion treatment, UV radiation, filtration and heating up.

The resulting fresh water is stored in tanks, which are usually found in the hull of the cruise ships. With the aid of special pumps, the water finally reaches the end user in the bathrooms, laundry, the kitchen, etc. through kilometers of pipes that run through the ship. During the construction of the tanks, particular care is taken to protect the water from contamination. The plants achieve a quality of water that meets the drinking water standard on land.

Going Down the Drain – What Happens to Sewage Water?

Modern day cruise ships can carry several thousands of people who use the showers, toilets, pools and spa areas every day and all this results in astounding amounts of sewage material. Additional waste water is generated by the laundry, kitchen and other servicing facilities on board. Throughout the years, many cruise lines have been accused of dumping their wastewater directly into the ocean, but maritime regulations have changed in the recent past and all modern cruise ships are obliged to have their own wastewater treatment plant on board. To understand how it functions, let’s look at the four main types of wastewater on ships and how each type is processed.

Black Water

Black water is the first and most ghastly category. It refers to highly polluted waste water, containing fecal solids from the toilet system, bacteria, as well as traces of prescribed medications and hormones. To go from gruesome to golden, black water is treated in several steps – mechanically, biologically, as well as chemically. The first step is the mechanical treatment of the water, whereby coarse impurities (particles with a diameter of less than one millimeter) are mechanically filtered out. In the second step, the water goes through biological purification, where microorganisms decompose the organic matter. In the third step, the water runs through filters with extremely fine sifts (0.2 microns) that sort out all microorganisms. The filter membranes are advanced enough, so that no further disinfection of the water is necessary. The final step is nitrogen and phosphorus reduction. After all this treatment, black water may be disposed of overboard, if the ship is more than 12 nautical miles from land.

Grey water refers to most of the sewage on board, for example, from showering, bathing, washing hands, the laundry and the kitchen. Grey water is not as heavily polluted as black water, but still contains considerable amounts of pollutants, such as residues of personal care products, detergents or pharmaceutical products. On most ships it is therefore collected and treated together with the black water. According to current regulations, grey water may be dumped into the ocean 4 nautical miles from land.

Bilge Water

Bilge water may form in the lower part of the ship’s hull, the so-called bilge, for example due to condensate. Cruise ships have their own bilge water treatment system, which separates the gathered water from oil residues. The treatment of bilge water is extremely important, as even a small drop of oil can poison between 600 and 1,000 liters of water. The residues are separated from the water either mechanically, or chemically, and then transferred to special tanks. The separated oil residues are either burned on board or delivered ashore. The wastewater treatment plants on ships create by-products which are dehydrated and dried in a centrifuge. In order to prevent the reproduction of germs and to save space on board, the by-products are burned in an incinerator after they are dried. Once the ship docks, the ashes are disposed of with the remaining waste.

Ballast Water

Ballast water is taken in or expelled by seagoing vessels in order to increase the stability of the ship. The water is stored in appropriate ballast tanks and a quantity of up to 4000 cubic meters (141,258 cubic feet) is needed depending on the size of the ship. When seawater is sucked into the ballast tanks, small marine organisms, such as plankton, also get sucked in. When the ship sails to another location and expels its ballast tanks, these microorganisms are released into a foreign ecosystem, where they can spread rapidly and disrupt the balance of the existing ecosystem. To avoid this, ships are now obliged to filter and disinfect their ballast water through UV electrolysis or chemical treatment.

Where Has All the Garbage Gone?

16 tons of food waste are produced on average each week on a medium-sized cruise ship.

Since storage space on board is limited, a portion of the food leftovers is thrown overboard at the end of each day and ends up as fish food. This practice continues because food waste regulations are not as strict as those for sewage, for example. Despite the fact that food waste is theoretically not toxic to the environment, large quantities of it lead to the overfertilization of the oceans and fast algae growth, which in turn leads to a decrease in oxygen levels in the ocean. According to the International Maritime Organization (IMO) regulations, shredded food garbage may be released three nautical miles away from land. In certain special zones, the regulation states at least twelve nautical miles away from land. These regulations are often criticized for being outdated, as the passenger capacity on cruise ships, and therefore the quantities of garbage produced, has drastically grown in the past decade.

Cardboard, metals and plastics are collected and pressed together by hydraulic garbage compressors. Glass is crushed into small pieces by onboard crushing machines and then filled into large bags, each weighing a whole ton when full. Non-recyclable garbage is burned in incinerators and turned to ashes.

In the ports, the shipping companies then pass on the bundled waste packages to local disposal companies. The Marine Pollution Code of the IMO, states that no vessel or offshore platform may dump ashes from incinerators, oil from the kitchen or plastics into the sea, no matter the distance from land.

Part 2 Coming Soon…

In next week’s post , you can find out how the laundry rooms, the housekeeping, and the kitchens operate aboard a cruise ship.

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Blackwater Treatment Onboard Cruise Ships Explained

Cruise ships house thousands of passengers and crew, which leads to enormous wastewater generation of up to 1000 cubic metres per day. Hence, Wastewater management has become a critical aspect of everyday operations.

 A cruise ship needs to be self-reliant in this aspect, as it stays away from land for a considerable period of time. 

Wastewater onboard cruise ships are categorised into two types, namely, greywater & blackwater.

Greywater comes from bathrooms, showers and washbasins. The water from galleys, meat rooms, fish rooms and laundries is also greywater. However, such water is called galley & laundry grey water for ease of differentiation.

Blackwater is the dirty water from toilets and urinals, including flushed water. Since it consists of human waste, which is infectious & an environmental hazard, it needs special handling & treatment processes for its storage onboard or its discharge overboard outside ecological limits.

Therefore, our focus in this article will be on blackwater management, treatment and disposal.

Related reading:

• Sewage Treatment Plant on Ships Explained
• 4 Important Terms Related to Sewage Treatment Plant on Ships

Blackwater Collection & Segregation/Pre-treatment

Blackwater is collected in blackwater collecting units via a ring-main system. The ring-main system is divided by various decks or zones onboard and connected to different blackwater collecting units.

There can be multiple numbers of collecting units (4-10 units) depending upon the size of the ship. They are usually installed in technical spaces throughout the ship, where technical staff can monitor and maintain them.

The blackwater is collected in the collecting tanks by gravity or vacuum. In the case of a vacuum system, the vacuum is generated in the collecting tank & its suction line using attached vacuum pumps which operate per the vacuum level through sensors.

The blackwater goes to the collecting units through coarse strainers, which must be cleaned daily or as per demand. These strainers remove any large-sized solids that may go to the collecting tanks, clog pipework or the discharge pumps. 

The blackwater collecting units have attached discharge pumps that are normally set to work on a timer but can also be set to work on the level. The pumps are operated by float switches and operate from time to time to lower the level of the blackwater collecting units. These pumps are sewage discharge pumps and transfer the blackwater from the collecting units to screen presses.

The screen presses further separate the solids, such as toilet paper, plastics, grit, fibres, rags etc., from the blackwater, thus ensuring that only the liquid passes through to the next stage, which is the treatment stage. 

This is done by first separating the larger-sized solids by a mesh called a screen and, after that, removing the fine suspended solid impurities by a large screw shaft operated by a motor, which grinds and separates out the finer solids. 

The screened or filtered blackwater passes through to the next stage, the treatment stage, whereas the separated solids from the screen press are collected in a separate tank, usually known as a Bio-sludge tank.

Accommodated greywater can also be fed to the MBRs along with blackwater. This process is automatically controlled as per demand, with the help of a 3-way valve at the inlet to the screen presses. At times of low blackwater generation, which is usually at night when most people are asleep, the 3-way valve supplies greywater to the MBR system to maintain the levels of the stages.

In the above case, the accommodation greywater is stored in separate double-bottom tanks. MBR greywater pumps are provided, which operate automatically as per the greywater demand from the MBR and the level of greywater in the DB tanks.

Treatment Process

The screened/filtered blackwater goes to the sewage treatment plant known as MBR. MBR stands for Membrane Bio-Reactor. As the name suggests, it treats sewage or blackwater through biological processes and membrane filtration.

The MBR has two stages. The blackwater from the screen presses comes to the 1 st stage, where aerobic bacteria treat it. A constant air supply generates aerobic bacteria through blowers and diffusers, which create air bubbles for evenly distributing the air throughout the biomass. Excess air, water vapour & gases are vented from both stages by attached vent lines to the atmosphere.

The aerobic bacteria act on the sewage, thus breaking it down & separating the sludge from the sewage water. The treated water now passes through to the 2 nd stage of the MBR, through the ISFs, which stands for Inter-Stage Filters.

The ISFs help to remove any finer particles or impurities that may have been generated in the first stage or carried over from the pre-treatment stage. The filtrate from the ISF is collected in an attached filtrate tank, from where it is pumped to the 2 nd stage of the MBR by filtrate pumps, whereas the separated screenings (solids) collected in the screenings tank and are either pumped back to the screen press or the 1 st stage by the screening pumps. Both the filtrate & screenings pump has one operational pump & one standby pump.

The condition of the ISFs must be regularly checked, and the filters cleaned if required. The filtrate to screenings ratio is a parameter that indicates the health of the ISFs. Usually, the ratio should be between 1 and 5. Readings well outside this range will necessitate checks and/or adjustments.

Like in the 1 st stage, further aerobic action also takes place in the 2 nd stage. This is to ensure that sludge separation takes place as much as possible so that only liquid passes through to the membrane-filtration stage, thus reducing the possibility of membrane clogging and/or breakage, which can result in downtime and increased maintenance.

The separated sludge from both the 1 st stage & 2 nd stage must be removed daily to prevent the accidental carryover of the sludge along with the liquid to the membrane. There are separate sludge pumps and tanks which are provided for that purpose. Chemical dosing is also done in both stages for sewage sludge conditioning.

The liquid (wastewater) under treatment is pumped from the bioreactor’s 2 nd stage to the membranes by the centrifugal crossflow pumps. The membranes are usually arranged in multiple (usually 3 to 4) parallel banks. Each bank has several membranes in series & its crossflow pump. The individual banks can be isolated for cleaning or maintenance without disturbing the process.

Each membrane is tubular, with 8 mm nominal bore tubes mounted onto 200 mm nominal diameter fibre-reinforced casings. The membranes are rated in the ultra-filtration range, with a nominal pore size of 40 nanometres. 

There are several billions of such microscopic pores on the surface of the membrane fibre, which while forming a barrier to microbial impurities such as bacteria, viruses and protozoa, allow pure water molecules to pass through, thus affecting treatment. The untreated wastewater recirculates back to the bioreactor 2 nd stage.

The membrane banks, which foul due to accumulation of impurities, must be backflushed or flushed with clean freshwater once each day and chemically cleaned once a week for continued operational reliability and to avoid breakdown and damage to membranes. Membrane replacement can be a costly and time-taking affair.

The membrane-filtered liquid, known as permeate or treated wastewater, may be treated with chlorine for further disinfection before being pumped to permeate or treated wastewater storage tanks through a Turbidity sensor, which stops the permeate pump in case of high turbidity. 

The stored permeate is pumped overboard, if & when outside of environmental limits, by treated wastewater pumps. Chlorine treatment (disinfection), in the case of MBRs, is not usually necessary if the bio-reactor & membranes are performing well.

Weekly tests must be performed for Biological/Chemical Oxygen Demand, smell, colour and E-Coli by taking samples from both stages of the bio-reactors permeate to ascertain the performance of the MBR plant.

While accommodation greywater can be supplied to the MBR, it is not advisable to use galley & laundry greywater, as the presence of detergents and/or oils can potentially be detrimental to the aerobic bacteria, thereby affecting biomass generation and function. For this reason, galley and laundry greywater also have their own separate storage tanks.

Blackwater management is a complex process that demands a comprehensive understanding of the system, strict attention to parameters, adherence to proper & timely maintenance procedures and accurate troubleshooting for continued efficiency and operational continuity.

The system’s complexity can also be a factor in the size of the ship. Bigger ships will put a considerable load in terms of operations & routines. Although designed to operate automatically and without manual assistance, systems are always prone to failure. It is advisable to follow manufacturer guidelines, manuals, maintenance schedules & regular testing to ascertain the plant’s health. 

You might also like to read-

• The World Largest Cruise Line: Carnival Cruise Ships
• The Vista Class Queen Victoria Cruise Ship
• The Incredible MSC Fantasia Cruise Ship
• What are Polar Cruise Ships?

Disclaimer:  The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used in the article, have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 

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Matador Original Series

Where Does the Waste Go on Cruise Ships, and Is It Really Sustainable?

D on’t pretend it hasn’t crossed your mind. When you flush a cruise ship toilet and hear that rapid, louder-than-usual whooshing sound, you wonder as you stare at the empty bowl … “where does it all go?” On land, we have all kinds of easy explanations. We have sewer systems that pump to sewage treatment plants where the waste is processed and treated. But at sea, when you may not be making landfall for days, what happens to it?

You wander out of the bathroom and onto your private balcony, where you sit and stare out at the vast sea. Then it hits you. “What about everything else?” It’s not just human waste that seemingly has nowhere to go in the middle of the ocean, but food waste, plastic waste, and pretty much everything else we mindlessly toss in the trash. There are no dumpsters around the corner, no recycling plants nearby. How do cruise ships dispose of waste in a sustainable manner, so that doesn’t do irreparable harm to the environment?

Nothing that’s human-made in this world is 100 percent sustainable. That said, as public attention to sustainability efforts across all industries has increased, cruise ships have implemented a number of sophisticated treatment and recycling programs for everything from sewage and organic waste to landfill diversion in order to minimize the environmental impact of leisure on the water.

How waste disposal actually works

First of all, before we start talking about getting rid of waste — what happens to it on the ship? It has to be stored somewhere until it’s ready to be discharged, after all.

“Human waste is processed through our advanced wastewater treatment system,” Sarah Dwyer, Sustainability Program Manager for Virgin Voyages , tells Matador Network . “This system processes all blackwater (toilets), greywater (sinks and showers), laundry water, galley greywater, and food waste reject water to comply with MARPOL (International Convention for the Prevention of Pollution from Ships) regulations.”

The process is similar on Uniworld Boutique River Cruises although waste storage on a smaller river ship will differ somewhat from storage on a huge ocean liner.

“Human waste is collected in a tank (with a bacteria system) and this is emptied regularly, depending on where the ships are docked and whether we have access to the local sewerage system or if we have an external company coming to pump it out,” Julie Higgins, Sustainability Officer for Uniworld Boutique River Cruises, tells Matador Network . “For food waste, each ship has a geographical partner that either collects the food waste for animal feed or uses it for biofuel creation. These pickup points are fixed according to each itinerary.”

It’s not exactly surprising that cruise ships have pretty well-developed and intricate methods of getting rid of their waste. On Uniworld, both collection and offloading are more frequent, given the closer proximity of port.

Food waste is “collected by various companies, while human waste is collected in tanks on board each ship and then disposed of either directly into the city or town sewerage system,” Higgins says. “Otherwise, we have companies that come and collect it from our tanks when this is not possible depending on port facilities.”

As for larger ships like those operated by Virgin Voyages, waste must be discharged a certain distance from shore, or stored in a special recycling center for offloading.

“For our advanced wastewater treatment process, effluent (liquid waste or sewage) is held on board and then discharged at distances greater than three nautical miles from shore,” Dwyer says. “Food waste is either pulverized and discharged (12 nautical miles from shore and at a speed greater than six knots), or it’s stored in our waste recycling center to be offloaded in port.”

Is waste disposal actually sustainable?

The big complaint facing cruise lines is the issue of sustainability. From carbon emissions to how waste impacts the surrounding ecosystem, there are very real concerns about the impact cruises have on the ocean. That’s why environmental regulations are tighter than ever, and cruise lines have implemented strict treatment methods to limit any harm done by waste disposal.

“Our advanced wastewater treatment system is calibrated to meet stringent water quality standards under MARPOL and the US Clean Water Act,” Dwyer says. “Our crew ensures that our vessels are in compliance with the the National Pollutant Discharge Elimination System and Vessel General Permit, which are monitored by the Environmental Protection Agency.”

What does this actually mean? Well, everything from wastewater treatment methods to offloading strategies that divert waste from landfills.

“Our wastewater is treated by the bacteria within our tanks on board, which forms something we call ‘sludge,’” Higgins says. “We then dispose of this ‘sludge’ responsibly … over the years we have formed a reliable network that allows us to dispose in a responsible manner and not pollute the areas we sail through.”

The most visible part of Virgin Voyages’ sustainability program is its reduction of single-use plastics on board, as well as incorporating more sustainable materials for its passengers. From banning plastic utensils to using reusable food containers in restaurants, the goal is to limit how much non-recyclable waste is even produced in the first place.

“We collect and sort recyclable waste on board, which is then offloaded in our primary ports such as Miami,” Dwyer says. “We also have a recycling takeback program from our beach club operation in Bimini (Bahamas) to limit recyclable materials that would otherwise be sent to the landfill. We also vet the waste providers that we partner with on-shore to ensure waste is handled appropriately.”

In an industry that’s inherently not known for sustainability, it’s clear that cruise lines do all they can to reduce their environmental impact. But is it enough?

The impact of waste disposal on the ocean

While many cruise lines take sustainability seriously and ensure their waste management systems are up to code, that’s not always the case, resulting in harmful pollutants entering the ocean.

“Several cruise ships still use scrubber technology, which discharges a toxic cocktail of petroleum byproducts from ships directly into the ocean with little to no treatment,” Marcie Keever, Oceans Program Director at Friends of the Earth , tells Matador Network . “The ICCT (International Council on Clean Transportation) estimates that in one year, ships worldwide will emit at least 10 gigatons of scrubber wastewater, approximately 15 percent of which comes from the cruise industry.”

She also believes more oversight is needed to ensure the cruise industry’s sustainability standards are as strict as they should be. And indeed, however strict those regulations might be, without proper oversight, the rules themselves (if frequently broken) are irrelevant.

“The cruise industry remains a major contributor to air and ocean pollution, repeatedly failing health compliance and environmental tests,” she claims. “At the federal level, Homeland Security and the EPA provide little regulation enforcement and no oversight on wastewater discharge or public health, even though cruise ships continue to be a major spreader of harmful pathogens like COVID-19.”

Indeed, Carnival was fined in 2019 for dumping waste into the ocean. Apart from ocean water, Keever notes cruise ports themselves are also a serious victim of cruise ship waste.

“One community in Alaska fought hard against the industry after being filled with trash and sewage from ships,” she says. “In addition, carbon emissions from ships harm the places where they dock. Friends of the Earth is working to help ports electrify to reduce carbon emissions and improve air quality for surrounding communities.”

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Original research article, sources and leakages of microplastics in cruise ship wastewater.

• 1 Department of Environmental Sciences, Faculty of Science, Open Universiteit, Heerlen, Netherlands
• 2 Cartagena Convention Secretariat, United Nations Environment Programme, Kingston, Jamaica

To date, the contribution of sea-based sources to the global marine litter and plastic pollution problem remains poorly understood. Cruise ships produce large amounts of wastewater and concentrate their activities in fragile and ecologically valuable areas. This paper explores for the first time the sources of microplastics in cruise ship wastewater, as well as their pathways from source to sea. It thereto uses a novel approach for the identification of sources and pathways, based on scientific literature on microplastic sources and pathways, literature on cruise operations and wastewater management as well as a questionnaire among cruise lines. The study highlights personal care and cosmetic products, cleaning and maintenance products and synthetic microfibers released from textiles in laundry as relevant source categories. Untreated grey water and the overboard discharge of biosludge, resulting from the treatment of sewage and grey water, were identified as key pathways. Cruise lines can reduce microplastic emissions by adapting their purchasing policies for personal care, cosmetic, cleaning and maintenance products and professional textiles. In addition, the holistic management of all wastewater streams and resulting waste products is essential to prevent leakages of microplastics from cruise ships to vulnerable coastal and marine ecosystems. Furthermore, the approach can be used to guide company-level assessments and can be modified to address microplastic leakages in other maritime sectors.

1 Introduction

Marine litter is a problem of emerging concern and research efforts as well as initiatives to address the problem are developing rapidly ( UNEP, 2021 ). Recently, a breakthrough was achieved at the United Nations Environments Assembly (UNEA-5.2), where 175 nations committed to forge an international legally binding agreement to end plastic pollution by 2024, addressing the full lifecycle of plastic from source to sea 1 . Marine litter is defined as “any persistent, manufactured or processed solid material discarded, disposed of or abandoned in the marine and coastal environment” ( UNEP, 2021 ). While the term embraces different types of materials, plastics constitute the largest proportion ( Galgani et al., 2015 ). Jambeck et al. (2015) estimated that in 2010, 4.8 to 12.7 million MT of plastics entered the ocean, and inputs are expected to increase over the coming decades ( Lebreton and Andrady, 2019 ). Plastic can travel long distances and is found in all parts of the marine ecosystem, even in very remote locations such as in Arctic sea ice ( Obbard et al., 2014 ) and the Mariana Trench ( Chiba et al., 2018 ). Microplastics (MPs) are small pieces of plastic, with a size smaller than 5 mm. MPs comprise both manufactured microscopic plastic particles (primary MPs), such as microbeads with applications in the cosmetic industry and industrial pellets used for the production of plastics, and particles that result from the abrasion and degradation of larger items (secondary MPs) ( Cole et al., 2011 ). MPs in the marine environment can be ingested or inhaled through the gills by a wide range of organisms ( Wright et al., 2013 ; GESAMP, 2016 ; Hantoro et al., 2019 ). Once ingested, MPs may block or damage intestinal tracts ( Cole et al., 2011 ; Wright et al., 2013 ). They can also be absorbed through the gut walls ( Foley et al., 2018 ). In addition, MPs may leach toxic pollutants, including chemicals that are intentionally added during plastic production as well as organic contaminants and heavy metals that sorb to the MP surface ( Teuten et al., 2009 ; Rochman et al., 2014 ). Impacts that have been associated with MP ingestion in marine biota include adverse effects on feeding (e.g. Wegner et al., 2012 ), growth (e.g. Au et al., 2015 ), reproduction (e.g. Della Torre et al., 2014 ) and survival (e.g. Luίs et al., 2015 ). Besides the effects at the individual level, MPs as well as pollutants absorbed by MPs, can be transferred through food webs ( Farrell and Nelson, 2013 ; Setälä et al., 2014 ) and induce ecological impacts ( Rochman et al., 2016 ). Human health may also be affected by MPs in the marine environment through the consumption of contaminated seafood ( Hantoro et al., 2019 ; Campanale et al., 2020 ).

In order to effectively address marine litter and (micro-)plastics, it is necessary to understand the contribution of individual sources and the pathways from these sources to the environment. Assessing the origin of MPs in the environment is complicated ( Hardesty et al., 2017 ) and the relative contribution of different sources and pathways is strongly dependent on local conditions ( Duis and Coors, 2016 ). While it is generally assumed that most marine litter derives from land-based sources, the contribution from sea-based source varies strongly by geographic location and could be substantial for specific locations ( GESAMP, 2021 ). Knowledge about sea-based sources is still little developed compared to land-based sources; the GESAMP (Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection) Working Group on sea-based sources of marine litter concluded that knowledge of the type, quantity and impact of sea-based sources is lacking ( GESAMP, 2021 ), thus hindering the development of effective mitigation strategies. Ship-based sources contribute to MP pollution, e.g. through paints and coatings, abrasives used for the cleaning of ship hulls during maintenance, loss of cargo (e.g. plastic pellets) and discharges of wastewater ( Boucher and Friot, 2017 ; Bray, 2019 ; GESAMP, 2021 ). In terms of wastewater, cruise ships would be of particular interest because of the large quantities of wastewater that are generated on board these ships ( GESAMP, 2021 ). Vicente-Cera et al. (2019a) estimate that the world cruise fleet produced about 34.000.000 m 3 of wastewater in 2017; a production rate that is comparable to that of the country Cyprus 2 .

Until the start of the COVID-19 pandemic, the cruise industry had shown a constant growth, from 17.8 million passengers in 2009 to 29.7 million passengers in 2019 3 : an increase of 75% in 10 years. The pandemic led to a complete halt of operations; however, the industry expects a full recovery compared to 2019 levels by 2023 and a growth of 12% by 2026 4 . Currently, the largest cruise ship in operation can carry up to 6988 passengers and 2300 crew members 5 . Besides a means of transportation and accomodation, cruise ships typically provide a wide array of onboard services and attractions to their passengers, such as swimming pools, spas, theatres and sports facilities. The main mainstream cruise destinations are located the Caribbean, the Mediterranean and Northwestern Europe; specialty “adventure” types of cruises attend extremely remote and vulnerable environments ( Lamers et al., 2015 ) such as the Arctic and Antarctic. Around 70% of the cruise destinations are located in biodiversity hotspots ( Lamers et al., 2015 ) and cruise ships frequently pass through fragile coastal and shallow areas as well as marine protected areas, especially when entering or leaving ports ( Lloret et al., 2021 ). Caric et al. (2019) highlight that in the Mediterranean, cruise ships frequently anchor in close proximity of many marine protected areas (MPAs) and the heavily trafficked cruise port of Venice is even located within such a site. Considering that cruise activities typically concentrate in certain coastal areas and routes, these vulnerable areas are exposed to cumulative environmental impacts of these activities ( Toneatti et al., 2020 ). With increasing cruise intensity, the impacts of the industry, including MP pollution, are likely to increase in the coastal and marine environment.

This study aims to highlight characteristics of the cruise sector that affect the potential for MPs being found in wastewater discharges, and provide recommendations to guide and set-up future research efforts as well as indicate general directions for mitigation. It thereto uses a novel approach for the identification of these sources and pathways, based on scientific literature on MP sources and pathways, literature on cruise operations and wastewater management as well as a questionnaire among cruise lines. First, an inventory was made of sources of MPs in the marine environment, based on general scientific literature. From this general inventory those sources were selected that are relevant to cruise operations and additional source categories were identified based on the characteristics of cruise operations and facilities. Subsequently, the identified sources were linked to the different wastewater streams and finally the management of each of these wastewater streams was evaluated.

2 Materials and Methods

Figure 1 presents an overview of the methodology for the identification of sources and pathways of MPs in cruise ship wastewater (detailed descriptions of the steps are described in the following paragraphs). Here, the term “sources” refers to the different applications of plastics and synthetic polymers on board cruise ships that have the potential to release. MPs to the marine environment. Through different release mechanisms, MPs find their way to the wastewater streams. Pathways are defined as the routes through which MP particles are transported to the marine environment, where the scope of this research is restricted to pathways through cruise ship wastewater discharges.

Figure1 Research steps in the identification of sources and pathways of microplastics in cruise ship wastewater.

2.1 Literature Review of Microplastic Sources

Since cruise ships are often characterized as “floating cities”, it was reasoned that MP sources on cruise ships have significant overlap with land-based urban sources of MPs. In addition, the maritime operations as well as any aspects that are unique to the cruise industry should be addressed. To identify and characterize sources of MPs, the research is based on the approach that was applied in different European countries, the European Union and the OSPAR region, as reported by Sundt et al. (2014) ; Lassen et al. (2015) ; Essel et al. (2015) ; Magnusson et al. (2016) ; Scudo et al. (2017) ; Verschoor et al. (2017) and Hann et al. (2018) . These studies estimate MP emissions at a local or regional scale, based on the sources and pathways of MPs reported in general literature in combination with local data on plastic uses and other relevant local factors. Lassen et al. (2015) define eight categories of primary MP sources and six categories of secondary MP sources, and identified the pathways from these sources to surface waters. This structure was adopted and the list was complemented with the results of other studies, reflecting all reported land-based and sea-based MP sources and pathways at national or regional level. Next, sources were selected that could be relevant for cruise ship wastewater during normal operations.

2.2 Cruise-Specific Functionalities

In order to cover all sources of MPs that are specific to the cruise industry, the following overarching types of MP sources were considered, representing different functionalities of cruise ships: cruise ship facilities, ship stores and people . Cruise ship facilities were further divided into hotel facilities and ship facilities , in accordance with the structure proposed by Lois et al. (2004) . The proposed facilities were supplemented by consulting Vogel et al. (2012) and Gibson and Parkman (2019) , as well as by studying the deck plans of the ten largest cruise ships in the world, in order to cover the main facilities that are present on modern cruise ships. Stores comprise the different purchasing streams of cruise ships: fuel, corporate, technical and hotel purchasing ( Véronneau and Roy, 2009 ). Finally, personal belongings of passengers and crew may act as MP sources; these are covered by the category “ people ”.

2.3 Inventory of Microplastic Sources

Following the identification of the main MP source categories on board cruise ships, the inventory as derived from the literature study was further developed and supplemented to cover those categories that have relevance to cruise ships. This was done by crosschecking the identified categories as derived from literature on the one hand and the identified facilities, stores and people categories from the previous step on the other. This approach resulted in the elimination of some of the MP sources that were identified in the previous step, because of differences in the characteristics of these sources on board cruise ships compared to the general characteristics that are described in literature. On the other hand, cruise-specific sources were added to the general inventory. The contribution of specific facilities and stores to MP pollution is not always straightforward and requires a thorough understanding of operations, facilities and the types of stores. The details of many specific cruise operations are not extensively reported in literature, and only to a limited extent in grey literature. Therefore, in order to assess the relevance of the different facilities and stores, Google searches were used to identify open access online resources, such as deck plans and pictures of the 10 largest cruise ships (e.g. to understand the application of artificial grass and the organization of laundry facilities) as well as blogs and YouTube videos, concerning the specific cruise ship operations and facilities such as laundry installations and engine room operations. In addition, experts were consulted to verify the findings (see below).

2.4 Linking Wastewater Streams to Microplastic Sources

In order to establish links between the sources on the one hand and wastewater streams on the other, the different sub-streams of the wastewater streams were identified based on literature. Then, the pathways from the identified sources to the different wastewater streams were assessed, by crosschecking each of the sources to the identified wastewater streams and vice versa.

2.5 Wastewater Management

The objective of this step was to map the main routes of the different wastewater streams and the key characteristics of treatment processes, where applicable, in order to identify potential pathways of MPs from the different wastewater streams. In addition, the characteristics of common treatment technologies were described. The assessment is based on scientific literature as well as grey literature. In order to verify the findings based on the grey literature, experts were consulted and a questionnaire was distributed among cruise lines.

2.6 Expert Consultation and Questionnaire

A preliminary version of the inventory of sources and pathways of MPs on board cruise ships was reviewed by experts in the fields of marine litter (3 experts) and MPs in onshore wastewater (1 expert). The typical practices and systems for wastewater management on board cruise ships were discussed with two experts in the field of maritime wastewater management and one cruise industry representative. In addition, a questionnaire was developed and distributed among cruise lines to verify the preliminary findings and collect additional industry-specific information. The questionnaire was distributed in February 2020 to the environmental managers of different cruise lines through the Cruise Lines International Association (CLIA). It consisted of a general section, where respondents could indicate the fleet size, a general wastewater management section and sections related to different wastewater treatment technologies. The final section concerned the measures and policies addressing MPs in wastewater.

2.7 Analysis and Interpretation of Results

This research involved different types of information and data, from different fields of research as well as use of a questionnaire and expert interviews. In order to organize these data, the research was structured around the existing frameworks from literature for the inventory of general MP sources as well as cruise facilities. In addition, the identified wastewater streams and related wastewater management practices were described in tabular form. These frameworks were then combined into matrices in order to structure the available information and to ensure that all relevant topics were covered through crosschecking. This structure guided the more detailed part of the research, and in particular the identification of cruise-specific MP sources. Where scientific literature was lacking, secondary resources were considered.

3.1 Literature Review of Microplastic Sources

Tables 1 , 2 present the overview of main source groups of primary and secondary MPs in the marine environment, modified from Lassen et al. (2015) , and extended with the results from other studies (indicated in the table, where applicable). The column on the right indicates whether the listed source groups were considered relevant for cruise ship wastewater. MP sources that were not considered relevant include raw materials for plastic production, industrial and professional handling processes of plastics, emissions from road traffic (tires, brake pads, bitumen and road paint), agricultural, aquaculture and oil and gas applications, typical onshore waste management issues (illegal waste burning, landfills and dumps), as well as the fragmentation of macroplastics in the environment due to natural processes. Also, the blasting of the ship hull during large scale maintenance with plastic abrasives is not further considered as blasting is not part of normal ship operations. Furthermore, Lassen et al. (2015) includes a separate category of primary MP emissions from paints through the washing of brushes. This source group was not considered applicable to cruise ships since this is mainly relevant for “do it yourself” and not for industrial practices ( Verschoor et al., 2016 ). The category other includes plastic beads used in professional dish washing machines, plastic beads and ironing beads used by children, printer toner, specialty chemicals in wastewater treatment facilities ( Scudo et al., 2017 ) and oil and gas industry ( Sundt et al., 2014 ).

Table 1 Generic primary MP sources, modified from ( Lassen et al., 2015 ) and indicating relevance to cruise ships.

Table 2 Generic secondary MP sources, modified from ( Lassen et al., 2015 ) with descriptions and relevance to cruise ships. .

3.2 Cruise-Specific Functionalities

3.2.1 facilities.

Tables 3 and 4 give an overview of the typical hotel facilities and ship facilities as present on contemporary cruise ships, based on Lois et al. (2004) . The overview is not exhaustive and may not be representative for all cruise ships but is indicative of the main systems and facilities present on ships, with the purpose to identify potential sources of MPs throughout the vessel.

Table 3 Hotel facilities on board cruise ships [adapted from Lois et al. (2004) ].

Table 4 Ship facilities on board cruise ships [adapted from Lois et al. (2004)] .

3.2.2 Stores

Cruise ships carry stores of various types. Such stores include fuel and ship maintenance products for ship operations as well as food, potable water and detergents for hotel operations. Véronneau and Roy (2009) distinguish the following main purchasing streams of cruise ships: fuel, corporate, technical and hotel purchasing. Fuel purchasing covers fuel and other petroleum products for daily consumption, such as lubricants. Corporate items relate to office related materials such as office supplies and computers. Technical items include items for facility and ship maintenance, e.g. engine parts, electronic components and carpeting materials. Consumable items and food required for hotel operations fall under the category of hotel purchasing. Furthermore, fresh water is a key resource on board.

3.2.3 People

Passengers and crew bring their personal belongings in their luggage. Significant categories are likely to include personal clothing, shoes, flipflops, personal toiletries and medication, electronics, books, suitcases and backpacks and snacks. People with children may bring plastic and inflatable toys. Furthermore, souvenirs bought ashore are brought on board after port visits.

3.3 Inventory of Sources and Release Mechanisms

Overviews of key MP sources and release mechanisms of both primary and secondary MPs on board cruise ships are displayed in Tables 5 and 6 . The categories from Lassen et al. (2015) were revised to reflect both the general categories as found in literature as well as the relevance of these categories for cruise operations.

Table 5 Primary microplastic sources and release mechanisms with relevance to cruise ship wastewater.

Table 6 Secondary microplastic release mechanisms and sources with relevance to cruise ship wastewater.

The main source groups for primary MPs ( Table 5 ) are personal care & cosmetics, cleaning & maintenance and medical & pharmaceutical. Potential release mechanisms are mainly related to the use of products in “wet” applications, e.g. rinse-off bath and shower products, spa treatments, wet cleaning, dish washing, laundry and wastewater treatment. Other release mechanisms include medication use, medical and dental treatments, printing and damage of user products that contain primary MPs, e.g. polystyrene pellets or beads. In addition, certain shipboard wastewater treatment systems use flocculants ( EPA, 2011 ; Chen et al., 2022 ), which could be polymer-based. The detailed assessment of cruise ship facilities led to the exclusion of rubber granules from artificial turfs as a source of primary MPs: no examples could be found of high impact sport facilities on board cruise ships that would require “third generation turfs” using a performance infill of (synthetic) rubber granules for shock absorption ( Hann et al., 2018 ).

The identified release mechanisms for secondary MPs ( Table 6 ) include the wear and damage of products during normal use, laundry and cleaning of textiles, wear and damage of painted surfaces, waste handling and littering. Sources embrace all plastic and synthetic items and surfaces on board the vessel, including paints and waste.

3.4 Linking Wastewater Streams to Microplastic Sources

The main wastewater streams that are produced on board cruise ships are sewage, grey water and oily bilge water. Sewage is the wastewater from toilets and primarily consists of human body wastes and water and may on some ships be mixed with wastes from medical facility sinks and drains ( EPA, 2008 ). The International Convention for the Prevention of Pollution from Ships (MARPOL) covers the international regulations for sewage in Annex IV of the convention. According to these regulations, sewage may be discharged overboard without treatment outside coastal zones, provided that the ship maintains a minimum sailing speed of 4 knots. The average sewage generation rate is estimated at 68 l/person/day ( Vicente-Cera et al., 2019a ). Grey water consists of the wastewater streams from shower and bath, accommodation sinks, laundry, dishwashers and galleys ( EPA, 2008 ). Wastewater from these sources is in practice often mixed with wastewater from other sources, such as drainage from drains and sinks in non-engine room spaces, food pulper effluents and wastewater from whirlpools ( EPA, 2008 ). Unlike sewage, grey water discharges are not internationally regulated. Vicente-Cera et al. (2019a) estimate the average generation rate throughout the industry at 160 l/person/day. EPA (2008) defines oily bilge water as “the mixture of water, oily fluids, lubricants, cleaning fluids, and other similar wastes that accumulate in the lowest part of a vessel from a variety of different sources including engines (and other parts of the propulsion system), piping, and other mechanical and operational sources found throughout the machinery spaces of a vessel”. International regulations, covered by MARPOL Annex I, allow discharges of oily bilge water at sea, provided that approved oil filtering equipment is used. The oil residue from the filtering process is to be stored in dedicated oil sludge tanks and delivered to port reception facilities (PRF). Vicente-Cera et al. (2019a) estimate that the average industry generation rate is 23 l per nautical mile.

In order to link the different wastewater streams to MP sources, the identified wastewater streams were divided into different sub-streams, each reflecting potential entry routes of MPs into wastewater. The left-hand side of Table 7 summarizes the main sub-streams of which the wastewater streams consist. On the right-hand side, the primary MP source categories (as listed in Table 5 ), as well as the typical types of secondary MPs of relevance to these (sub-)streams are listed.

Table 7 Linking cruise ship wastewater streams to pathways and microplastic sources.

The results demonstrate that the MP sources attributed to the different wastewater streams vary significantly. The MP content in sewage derives from pharmaceuticals and detergents used for the cleaning of toilets as well as larger items that are disposed in toilets. The MP sources related to grey water include personal care and cosmetic products (PCCP), detergents used for cleaning, dishwashing and laundry, fibers from synthetic textiles and the secondary MPs that are removed by wet cleaning. Finally, the MP sources attributed to oily bilge water mainly relate to engine room operations, which may involve various products for the cleaning, maintenance and operation of machinery that contain primary MPs. In addition, the different sub-streams of oily bilge water collect solid waste and dust, including plastics and secondary MPs, on their way to the bilges.

3.5 Wastewater Management

3.5.1 sewage and grey water.

There exist two categories of treatment systems that are relevant to sewage and grey water. Older ships are typically fitted with sewage treatment plants (STP), generally referred to as Marine Sanitation Devices (MSD), dedicated to the treatment of sewage. On these ships, grey water is typically not treated ( EPA, 2008 ). MSD must be approved by the flag state of the vessel and comply with local effluent standards, if available. EPA (2008) reports that conventional MSD on board cruise ships treat sewage through biological treatment and chlorination, while some systems combine maceration and chlorination. Advanced Wastewater Treatment Systems (AWTS) comprise a range of relatively new technologies for treating sewage more effectively than the older MSD. For these systems to function properly, the influent of sewage is typically not sufficient. Thereto, (part of) the grey water streams are also routed through the AWTS. The use of these systems is becoming the standard in the cruise industry ( King County, 2007 ) and newbuilds are typically fitted with such systems ( Nuka Research, 2019 ). From the 2021 Cruise Report Card, published by Friends of the Earth 6 and covering the 18 major cruise lines and 202 ships, it can be derived that 75% of the cruise ships have an AWTS. According to Vard (2018) , most AWTS on board cruise ships are of the Membrane Bioreactor (MBR) type, utilizing an activated sludge process in combination with membrane filtration. Systems of the Moving Bed BioReactor (MBBR) type consist of a bioreactor filled with plastic beads, supporting bacterial growth, in combination with a Dissolved Air Flotation (DAF) unit ( Huhta et al., 2007 ). No complete overview could be retrieved of systems that are in use throughout the industry. However, the Alaska Department of Environmental Conservation annually reports which large cruise ships operated in Alaskan waters and which type of treatment system is used on board these ships. Table 8 provides an overview of the different systems that were used on board the ships that operated in Alaskan waters in 2019 ( ADEC, 2019 ), and indicates the number of ships associated with each system. Further information about these systems was collected from the AWTS brand websites, as well as ship-specific implementations, and added to the table. It follows that 18 out of 24 ships had an MBR type of AWTS, and 14 of these were of the brand Hamworthy. Six vessels operated an MBBR type AWTS of which 5 were of the brand Scanship.

Table 8 Overview of characteristics of AWTS systems and processes on cruise ships operating in Alaskan waters during 2019.

The MBR systems all involve a pre-treatment filtering of the influent to remove coarse solids and prevent blocking of the membranes. The treatment itself involves the biological oxidation through an activated sludge process and ultrafiltration through membranes, where concentrates are generally fed back to the bioreactors and filtered effluents are collected in a permeate tank. The MBBR influents also pass filters to remove coarse solids. In the reactor, biological matter is removed through aerobic biological oxidation, and consequently DAF units separate particulate matter. Finally, the effluents pass polishing filters. All systems utilize UV disinfection to remove pathogens. Where available, mesh sizes of screens and filters are included. Since MBR systems are based on ultrafiltration, the mesh of the membranes is very fine with pore sizes below 100 nm.

Both grey water and sewage could be discharged to the marine environment without treatment. This applies to grey water for ships which do not have AWTS and ships which route only certain grey water streams through AWTS. Furthermore, it is possible that treatment systems are switched off at open sea, resulting in discharges of raw sewage and grey water. In 2021, 25% of the cruise fleet had no AWTS in place and thus discharged untreated grey water to the marine environment. Since these would typically concern older, and smaller cruise ships, the percentage of total grey water discharged through this route is likely smaller and this is expected to decrease in the future due to the increased use of AWTS. The MARPOL Convention allows the discharge of untreated grey water and, under certain conditions, sewage outside coastal zones. So theoretically, treatment systems could be switched off when the ship is on open seas. An EPA survey of four cruise ships fitted with AWTS reports that all vessels operate the system on a continuous basis ( EPA, 2006a ; EPA, 2006b ; EPA, 2006c ; EPA, 2006d ) and therefore do not discharge raw sewage. This is in line with the CLIA waste management policy, which prohibits the discharge of untreated sewage on board member cruise lines 9 . One of the ships in the EPA survey ( EPA, 2006b ) only routes the grey water from accommodations to the AWTS and discharges galley and laundry wastewater overboard without treatment, demonstrating that discharges of untreated grey water also occur on vessels with AWTS. AWTS and MSD filtering and treatment processes separate the wastewater into treated effluents and waste products. Sewage is typically high in solids, such as toilet paper and sanitary items, which is removed before sewage enters the treatment system, leaving screening solids of various sizes in the sieves and membranes. Another waste stream is the formation of biosludge. Biosludge or excess biomass consists of organic material as well as bacteria, resulting from the biological consumption of sewage ( EPA, 2008 ) and contains over 95% water ( Avellaneda et al., 2011 ). It is separated from the treated effluents by filtration ( EPA, 2008 ) and therefore would contain any solids such as MPs that have entered the bioreactor.

Literature provides some information on the disposal of waste products from cruise ship sewage and grey water treatment. Disposal options are incineration on board, landing at PRF and discharge at open sea ( EPA, 2008 ; Klein, 2009 ; Avellaneda et al., 2011 ). The relevant findings from an EPA survey of four cruise ships with AWTS ( EPA, 2006a ; EPA, 2006b ; EPA, 2006c ; EPA, 2006d ) are shown in Table 9 , together with the details of a case study cruise ship, representing an average-sized cruise ship operating in the Caribbean, as described by Kotrikla et al. (2021) . From this table it follows that three out of five ships discharge biosludge overboard. One of these ships also discharges the screening solids from the laundry and accommodation wastewater treatment system overboard, whilst solids from sewage are collected and incinerated on board. These data are in line with Klein (2009) who reports the overboard discharge of waste biosludge by 15 out of 16 ships in Washington State waters, with dewatering and incineration of biosludge on board one ship. Experts interviewed as part of this research stated that delivery of biosludge to PRF is currently not a common method on a worldwide scale as adequate facilities are lacking. This is also outlined by Avellaneda et al. (2011) who raise the logistic challenges of dealing with the large amounts of biosludge from cruise ships in ports without fixed reception facilities, rendering this scenario unrealistic. The available data indicates that for screening solids, incineration or delivery at PRF is more common.

Table 9 Sewage sludge treatment and disposal on board four cruise ships ( EPA, 2006a ) ( EPA, 2006b ) ( EPA, 2006c ) ( EPA, 2006d ).

3.5.2 Oily Bilge Water

As international regulations prohibit the discharge of untreated bilge water, there are two main methods used for the disposal of oily bilge waters: storage on board and delivery to onshore facilities, and onboard treatment. The treatment of bilge water is aimed at separating the oily constituents and water, such that the treated bilge water can be discharged overboard and the oily constituents are retained on board in sludge tanks for delivery to shoreside facilities ( EPA, 2011 ). The systems used for the treatment of oily bilge waters are generally referred to as Oily Water Separators (OWS). EPA (2011) reports that contemporary OWS are comprised of a series of different separation methods and that all of the OWS systems for bilge waters that are approved by the US Coast Guard are a combination of gravity-based separation and one or more forms of polishing treatment. Oil and other contaminants that are contained from the bilge water are collected in sludge tanks. This oily sludge may be stored on board for discharge at shore reception facilities or incineration on board. Table 10 summarizes representative options for wastewater treatment and the discharge and disposal of the resulting effluents and waste products.

Table 10 Summary of identified representative wastewater management options per wastewater stream.

3.6 Cruise Line Questionnaire

Since the questionnaire was distributed almost simultaneous with the first infections of COVID-19 on board cruise ships, the response was minimal. One CLIA member company responded and completed the questionnaire. However, with a fleet size of over 15 vessels, the responding company can be considered an important player in the industry and generally representative.

All ships of this company have holding tanks and MSD or AWTS systems for the treatment of sewage and grey water, with most ships having AWTS. In the case of MSD, grey water is stored on board and discharged at a minimum distance of 12 nautical miles from the nearest land. All ships are equipped with OWS for the treatment of oily bilge water, and also fitted with holding tanks for discharge at PRF when necessary.

All MSD operated by the company are using biological treatment in combination with chlorination. The screening solids captured by the treatment process are incinerated on board. The MSD are operated on a continuous basis. When the ships operate within 12 nautical miles from nearest land, treated effluents are contained in storage tanks and discharged later.

Most AWTS installed are of the MBBR type, and some are MBR. All sewage, accommodation, laundry and dishwashing wastewater streams are routed through the AWTS. The systems are operated on a continuous basis and effluents are discharged at a minimum distance of 3 nautical miles from the nearest land, confirming commitment to the CLIA zero-discharge policy for untreated sewage. Biosludge is either discharged to sea, incinerated or landed at PRF, where the chosen method depends primarily on the region of operation. Screening solids are typically incinerated on board and ashes are delivered to PRF.

In terms of policies, the company reports the initiation of the phasing out of “discretionary single use plastics on our ships”. Additionally, onboard gift shops and spas do not sell products containing microbeads. No measures were reported regarding the use of synthetic textiles or the application of microfiber filters in laundry installations.

4 Discussion

This article explored for the first time the sources and pathways of MPs in cruise ship wastewater, using a novel approach, based on general literature on MP sources in the marine environment as well as literature and industry information on cruise operations and wastewater management practices on board cruise ships. An overview was presented of the main source groups and release mechanisms of primary and secondary MPs on board cruise ships. Pathways of MPs were identified by linking the identified sources to the main wastewater streams on board cruise ships and an assessment of typical wastewater management practices.

4.1 Inventory of Sources

An overview was presented of the main source groups of primary MPs on board cruise ships, each reflecting the types of products and operations that are relevant to MP releases: personal care & cosmetics, cleaning & maintenance, medical & pharmaceutical and miscellaneous. PCCP are generally considered a key source of MPs in onshore wastewater treatment plants (e.g. Carr et al. 2016 ; Mason et al. 2016 ). There is no reason to assume that this would not be the case on board cruise ships. Moreover, the use of sun protection products and presence of spa and beauty facilities could result in even higher loads. Both fragrances and UV-filters linked to PCCP have been detected in cruise ship wastewater ( Westhof et al., 2016 ; Vicente-Cera et al., 2019b ), with concentrations of fragrances at similar levels as those in onshore domestic wastewater and concentrations of UV-filters exceeding those ( Vicente-Cera et al., 2019b ). It should be noted that the data reported in the latter study were collected under maintenance conditions and could be an underestimate for normal operations with passengers on board. This suggests that cruise ship wastewaters contain concentrations of PCCP constituents that are similar or exceeding those of onshore wastewater. Several studies ( Sundt et al., 2014 ; Lassen et al., 2015 ; Magnusson et al., 2016 ) assessed medical and pharmaceutical products as a minor source of MPs to the environment. Both Westhof et al. (2016) and Vicente-Cera et al. (2019b) found concentrations of pharmaceutical compounds in cruise ship wastewater at similar levels compared to domestic wastewater, suggesting no substantial differences in their use on board cruise ships and on land.

Literature reports MPs and synthetic polymers in various products used for industrial cleaning and care. These include hard surface cleaners, toilet cleaners and blocks, stainless steel cleaners, bathroom acid cleaners, oven cleaners, laundry detergents and stain removers ( Scudo et al., 2017 ), commercial hand-cleaning products ( Lassen et al., 2015 ; Scudo et al., 2017 ) and synthetic waxes in floor agents ( Essen et al., 2015 ). Most of the listed product types could be relevant to cruise ships. However, no studies could be identified that address concentrations of detergents and other maintenance products in cruise ship wastewater, nor about the presence of MPs in products used for specific ship operations. Scudo et al. (2017) estimated that industrial hand-cleaning soaps used for the removal of grease, paints etc. account for more than half the tonnage of all applications of MPs in rinse-off products. Considering the nature of cruise ship operations, this could be an important source as well. In addition, considering the wide range of applications of MPs in industrial cleaning products, the use of MPs in specialty maritime and cruise cleaning and maintenance products cannot be ruled out.

The identified release mechanisms for secondary MPs include laundry, waste handling and littering as well as the general wear and tear of products, painted surfaces and other surfaces and facilities. The source products encompass a broad array of products and materials. Many of these concern facilities such as painted surfaces, furnishing and safety equipment, but also stores, e.g. disposable plastics, cleaning cloths and packaging materials and personal belongings. Whereas primary MPs in many cases are intentionally released directly to water during product use ( Boucher and Friot, 2017 ), secondary MPs mainly concern unintentional losses. These MPs may end up in wastewater, e.g. through wet cleaning, but could also be disposed of in solid waste or transported off the ship via air. As a result, not all MP sources may be equally relevant to wastewater. Laundry is an exception, as most of the microfibers released during laundry would be drained with laundry effluents to the grey water system. Synthetic textiles are considered a major source of MPs in the marine environment ( Carney Almroth., et al., 2018 ). Azizi et al. (2022) have summarized the findings of over 400 studies about MPs evaluation in conventional wastewater treatment plants on land. The authors concluded that, throughout the plants evaluated in these studies, fibers were most commonly found, with an average abundance of 57% fibers throughout the different treatment steps. The high contribution of fibers is commonly attributed to the washing of synthetic textiles (e.g. Browne et al., 2011 ; Napper and Thompson, 2016 ; Ziajahromi et al., 2017 ; Raju et al., 2018 ). Cruise ships have extensive laundry facilities for the washing, drying and folding of professional textiles and most ships also offer laundry services for guests and have launderettes for crew. On the Oasis of the Seas about 42,000 kg of laundry is processed on embarkation day 10 . This suggests that laundry may be a major source of MPs on board cruise ships, depending on the nature of professional textiles such as sheets, towels and crew uniforms. To which extent these MPs reach the grey water system also depends on the use of laundry filters, which could remove up to 78% of fibers ( Napper et al., 2020 ) and, as such, could substantially lower the concentration of microfibers in grey water. Many cruise lines have a policy in place, or have pledged to do so, to phase out certain single use plastics such as straws, stirrers and cups 11 , 12 , 13 , 14 , to reduce their plastic footprint. In line with this trend, cruise lines could consider the use of plastic-free or non-synthetic alternatives for the MP sources that are reported in this study. The majority of the primary MP sources relate to “stores”, indicating that these products are purchased on a regular basis by the cruise line. The company that was consulted in this study already stopped the sale of products containing microbeads in onboard shops. Such a policy could be further extended to also cover PCCP that are used throughout the ship (e.g. in bathrooms and spas) as well as cleaning & maintenance products, including industrial hand soaps. Secondary sources of MPs are more varied and also include permanent ship and hotel facilities, for which plastic-free alternatives are either unfeasible or excessively expensive. However, considering that laundry potentially is a major source of MPs in wastewater, measures addressing this specific source could be effective in order to minimize the total MP load in untreated wastewaters, for instance through replacing synthetic textiles with natural alternatives or the use of microfiber filters in laundry systems.

4.2 Pathways Through Wastewater

The results demonstrate that the MP sources attributed to the different wastewater streams vary significantly. The main sources related to sewage are pharmaceuticals, detergents and the disposal of larger plastic items in toilets. The sources related to grey water include PCCP, detergents, fibers from synthetic textiles and secondary MPs that are removed by wet cleaning. The sources attributed to oily bilge water mainly relate to engine room operations. The findings for sewage and grey water are in line with the findings of Westhof et al. (2016) , who evaluated the presence of different types of micropollutants in various wastewater streams on board a cruise ship. Their findings reveal a predominance of oral pharmaceutical residues in sewage with lower concentrations of other pollutants attributed to human excretion. In grey water the highest concentrations were found for caffeine, attributed to the draining of remaining coffee and residues to the grey water system, and flame retardants, which according to the authors diffused from the host material and were consequently discharged to wastewater via laundry, handwashing, bathing and showers. In addition, significant concentrations of pharmaceuticals, UV filters, fragrances and a plastic softener were found, indicating the relevance of PCCP, skin applied pharmaceuticals (e.g. salves) and laundry detergents for grey water.

This paper focused on MPs in the main wastewater streams on board cruise ships. Miscellaneous wastewater streams include ballast water, wastewater from pools, whirlpools and spas, food pulper effluents, effluents from sinks and drains, deck wash water and runoff, wash water from exhaust gas cleaning systems, cooling water, condensates as well as various types of operational wastewater from different types of equipment and machinery ( EPA, 2008 ; EPA, 2013 ; MEPC, 2017 ). These could also act as significant pathways of MPs. Ballast waters, for instance, have been reported to contain very high concentrations of MPs ( Matiddi et al., 2017 ). In order to assess the total contribution of MP pollution from cruise ship wastewater, these pathways should also be considered.

4.3 Wastewater Management

MPs in cruise ship wastewater may be discharged to the ocean through the discharge of both untreated and treated effluents, as well as through the overboard discharge of waste products from wastewater treatment.

The performance of wastewater treatment systems that are in use in the industry is not well documented due to a lack of administrative monitoring ( Westhof et al., 2016 ) and their effectiveness in retaining MPs in particular has not been comprehensively documented. EPA (2008) reports various pollutant concentrations in the effluents from various sampling efforts of AWTS and MSD effluents of cruise ships operating in USA waters between 2003 and 2005, with non-detected values for both settleable and suspended solids in most AWTS effluents. This indicates that the cruise ship AWTS included in the sampling efforts were generally effective in capturing solids. Furthermore, both membrane ultrafiltration, a main component of MBR systems, and DAF, a main component of MBBR systems, are associated with very high MP removal rates in onshore systems. For MBR and membrane ultrafiltration, rates reported in literature ( Talvitie et al., 2017a ; Lares et al., 2018 ; Ma et al., 2018 ; Lv et al., 2019 ) exceed 99% and this is considered the most effective technology to remove MPs in onshore WWTP (e.g. Sun et al., 2019 ). For DAF, values between 70% and 96% are reported ( Talvitie et al., 2017a ; Esfandiari and Mowla, 2021 ), for different types of flocculants and coagulants that are added during the process. On the other hand, EPA (2008) reports values of suspended solids in the effluents of cruise ship MSD systems which are substantially higher than the USA discharge standards for onshore wastewater treatment systems, indicating that these systems may be less effective in capturing MPs. No data could be retrieved regarding the effectiveness of OWS in capturing particulate matter. Onshore wastewater treatment plants are generally considered important sources of MPs in aquatic environment, despite their effectiveness in removing MPs from influents, due to the large volumes of wastewater that pass these plants [e.g. Talvitie et al. (2017b) ]. Considering the volumes of wastewater that are generated on board cruise ships, treated wastewater from cruise ships therefore represents a significant pathway.

The results of this study reveal that, currently, 25% of the world cruise fleet discharges all grey water without treatment to the ocean as these ships do not have AWTS. In addition, AWTS configurations not necessarily cover all grey water sub-streams and as a result, a potentially significant volume of grey water is discharged without treatment from ships with AWTS. Further study of typical configurations is required to assess the volumes and characteristics of such discharges throughout the industry.

Various studies of onshore wastewater treatment plants have investigated the fate of MPs in onshore wastewater treatment plants, demonstrating that the vast majority of MPs in the influent are captured in sludge ( Carr et al., 2016 ; Talvitie et al., 2017b ; Gies et al., 2018 ). Since sewage sludge is commonly recycled as fertilizer in agriculture applications ( Nizzetto et al., 2016 ), this represents a major pathway of MPs to the environment on land, leading to the accumulation of MPs in agricultural soils ( Corradini et al., 2019 ). Similarly, biosludge resulting from AWTS treatment on board cruise ships likely contains high concentrations of MPs, due to the expected effectiveness of MBR and DAF in capturing MPs. The results of this paper indicate that while three options for the disposal for biosludge are used throughout the industry, overboard discharge is the most common method. The overboard discharge of this substance therefore leads to a delayed and concentrated discharge of the MPs in grey water and sewage and this practice should be avoided. The development of adequate PRF for biosludge in cruise regions could be instrumental in reducing the volumes of MPs that are discharged through this pathway, especially in vulnerable areas receiving large numbers of cruise ships. The literature review as well as questionnaire response indicates that overboard discharge of screening solids is not common, however this practice has been reported for one ship by EPA (2006a) , indicating that this scenario cannot be ruled out.

In general, the available literature on wastewater treatment systems is restricted to a small number of dated reports (e.g. King County (2007) ; Huhta et al. (2007) ; EPA (2008) ; EPA (2011) , most of which were produced by USA government authorities. Furthermore, the available data regarding the practices of discharging untreated grey water and sewage as well as the overboard discharge of biosludge concern a limited number of isolated and largely dated case studies (e.g. EPA, 2006a ; EPA, 2006b ; EPA, 2006c ; EPA, 2006d ; Klein, 2009 ; Kotrikla et al., 2021 ). In order to address these knowledge gaps, this research collected information on both wastewater treatment systems and wastewater management practices from one large cruise line. The results confirm trends and practices in wastewater management as reported by other studies (see section 3.5.1). However, it should be noted that these efforts either build on voluntary contributions or on cruise operations in the USA, and Alaska in particular; an area that is more strictly regulated and monitored than the mainstream cruise regions in the Caribbean and Mediterranean. Therefore, these results are likely biased and caution should be taken when extrapolating these results to the industry as a whole, in particular in vulnerable areas with little regulation and/or inadequate enforcement. An industry-wide overview of wastewater management systems and practices, ideally linked to regions of operation, would greatly support the understanding of leakages of MPs and other pollutants from cruise ship wastewater.

Finally, as recently raised on one of the leading digital platforms in the maritime industry 15 , the improper management of solids in sewage may lead to discharges through other pathways, such as the disposal of any solids remaining in the holding tanks and the use of cutter pumps in the collection and treatment of sewage. These cutter pumps are purposely designed to remove the load on screens by breaking down solids in smaller particles. This is rendering screenings less effective, and even contributing to the formation and release of MPs to the environment. This further emphasizes the need for a holistic approach of wastewater management in order to prevent leakages of MPs.

4.4 Conclusions

This paper for the first time explored the sources and pathways of MPs in cruise ship wastewater, providing insight on the array of sources and pathways, highlighting priority areas for mitigation and identifying additional knowledge gaps. On the level of individual companies or ships, the overview of sources and pathways allows for the identification of mitigating measures from source-to-sea, by identifying the full array of sources and mechanisms that contribute to the release of MPs to wastewater, as well as the connections between sources and the different wastewater streams. As a result, it also provides guidance for purchasing policies by cruise lines and the need for ongoing education of crew and passengers.

In general, it is recommended that cruise lines consider the inclusion of PCCP well as cleaning and maintenance products containing primary MPs in their policies to phase out the use of single-use plastics. In addition, the replacement of professional synthetic textiles with non-synthetic alternatives and the use of laundry filters could be effective in reducing the MP load in wastewaters. Furthermore, adequate wastewater management is key to prevent MP leakages and reduce the MP load in wastewaters that are discharged to the ocean. This is greatly supported by the increased use of AWTS. However, the use of these systems is only a partial solution, which should be part of a holistic management of wastewater streams. Efforts should be made to minimize discharges through waste products, wastewater streams bypassing AWTS as well as wastewater streams other than discussed in this study. Although at the global scale, the quantitative contribution of MPs from cruise ship wastewater is small in comparison to land-based sources, local impacts could still be significant due to the large amounts of wastewater, waste products that are discharged without treatment, the vulnerability of the exposed coastal and marine ecosystems and the concentrated nature of cruise activities. To better place the problem in perspective, identify cost-effective measures and areas at risk, it is required that MP concentrations in different effluents and waste products are quantified through measurements and that contemporary wastewater management systems and practices throughout the industry are better understood.

In conclusion, the approach for this study was successful in exploring the major sources and pathways of MPs within the study scope, and to highlight knowledge gaps and starting points for mitigation. This makes it a valuable tool that could also be applied in other maritime sectors and will support global efforts to identify all sources and pathways of MPs within the context of the UNEA-5.2 resolution.

Data Availability Statement

The original contributions presented in the study are included in the article/supplementary material. Further inquiries can be directed to the corresponding author.

Author Contributions

The research was performed by MF and she also wrote the paper. CC and AL contributed by guiding the research, discussing ideas and supervising the writing of this paper. All authors contributed to the article and approved the submitted version.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Acknowledgments

The authors would like to thank Mr. G. Burnett of CLIA for distributing our questionnaire among the CLIA members and collecting their responses, as well as all experts who contributed to this research.

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Keywords: cruise ships, microplastics, wastewater, sea-based sources, marine litter, plastic pollution, marine pollution, shipping

Citation: Folbert MEF, Corbin C and Löhr AJ (2022) Sources and Leakages of Microplastics in Cruise Ship Wastewater. Front. Mar. Sci. 9:900047. doi: 10.3389/fmars.2022.900047

Received: 19 March 2022; Accepted: 28 April 2022; Published: 26 May 2022.

Reviewed by:

Copyright © 2022 Folbert, Corbin and Löhr. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Maartje E. F. Folbert, [email protected]

This article is part of the Research Topic

Plastics in Aquatic Systems: from Transport and Fate to Impacts and Management Perspectives

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An up-close look at an advanced cruise wastewater system

On one of Ketchikan’s rare sunny days this summer, a group of local residents gathered on the downtown cruise ship dock to board the Holland America ship Zaandam. The group had a fancy lunch on board, and then took a tour of not-so-fancy areas that most people never see: wastewater treatment, emissions filtration and garbage sorting.

After lunch, the group of Ketchikan business owners, elected officials, media and municipal employees watched a short video in one of the ship’s theaters.

“Every week on average, a cruise ship carrying 1,700 guests will produce up to 60,000 gallons of sewage,” the video’s narrator said.

It explained how much waste the floating cities produce, and what they do to manage it.

“We have an environmental officer on each of our ships, who provides environmental training and overseas shipboard compliance with environmental laws, regulations, industry standards and company policies,” the video continued.

Adrian Daniels is the Zaandam’s environmental officer. After the video, he took the tour through a door where opulence ends, and utility begins. Gone was the lush carpet, replaced with a painted metal floor. He walked up to a door with a key-card lock.

“We just going to go to the engine control room,” Daniels said. “Without stating the obvious, please don’t touch anything.”

About 95 percent of the ship’s automated systems are controlled from here, with three people minimum on watch at all times. Alexies Varon is the senior watchkeeper and is in charge of the ship’s wastewater plant.

“All the black water and gray water that comes from the cabins – is pumped by the jet pumps,” Varon said.

Blackwater is anything flushed in a toilet. Graywater is pretty much everything else – whatever goes down a sink or shower drain, for example. Varon explained that the Zenon-brand wastewater system mixes those, and treats both the same.

The water is sent into a filtration system to separate solids. The liquid is sent into a bioreactor and membrane filtration system to further filter impurities. Then, there’s a final step.

“It goes also on your UV filter to kill all the germs in there,” Varon said. “And then… it goes overboard or (we) keep it in the ballast tank to pump it outside 12 miles.”

The Zaandam, with its advanced wastewater treatment system, is one of the ships the state allows to discharge continuously, including when it’s docked next to a community. A local resident asked Daniels what is discharged in port.

“We discharge permeate,” Daniels said.

And what’s permeate?

“It’s been through the reactor. It’s been sterilized. It’s like clear water,” Daniels said. “It’s tested twice a month by laboratory and we have a random unannounced sampling as well to check for the criteria within that permeate.”

Daniels said that testing looks at levels of bacteria and dissolved metals. He said they meet international, federal and state regulations for discharge. And, he said, the permeate meets standards for drinking water.

But is that enough?

“That may be the case for human drinking water standards. But they may be releasing concentrated levels of metals that are completely intolerable to baby salmon, for example,” Michelle Ridgway said. She’s a marine ecologist who grew up in Ketchikan and now lives in Juneau – two of the largest cruise ship towns along Alaska’s Inside Passage.

Ridgway also was a member of the state cruise ship science and technical panel. In that role, she examined state regulations governing cruise waste and emissions, and procedures ships use to manage it.

While the science panel as a whole signed off on the state’s cruise ship wastewater regulations as adequate for marine life, Ridgway is concerned about discharge near shore and in port, even when the water is clear.

“Water can be crystal clear and contain quite a number of chemicals,” Ridgway said. “Heavy metals, such as copper, has been one of the constituents of the wastewater that’s of particular concern for us in Alaska.”

The science panel’s report notes that the state’s criteria for copper if 3.1 parts per billion. Cruise ships like the Zaandam are subject to state testing in addition to other tests.

But, Ridgway said even a little bit of copper can harm a salmon’s sense of smell. And they use smell to find their way back to the correct stream for spawning.

“We certainly know how much we like our king salmon. I don’t know about some areas in Southeast, but in the north area, we have seen a major decline in king salmon recently,” Ridgway said.

Ridgway said other marine animals are affected by dissolved metals. Krill is one example, and that’s an important food source for many ocean creatures, including whales.

Ridgway also questions how effective the systems are at removing tiny particles such as viruses and pharmaceutical residue.

So, what should the ships do to reduce their impact? Ridgway suggests cutting back on the amount of water used, along with continuing to improve on-board treatment systems. That includes more controls on temperature and acidity of wastewater, to make sure ships aren’t adding to ocean acidification or warming waters.

Ridgway said she’s definitely not anti-cruise ship.

“I was raised in the maritime and fisheries culture of Alaska,” Ridgway said. “I love ships and shipping, and I’m thrilled that people get to come to Alaska to enjoy wild Alaska.”

But, Ridgway said the cruise industry needs to do everything it can to maintain the wild Alaska that its customers come to see.

The cruise lines, at least according to the video, seem to recognize that, as well.

“Keeping the ocean safe and clean is good for the environment,” the video started. “It’s good for global ecosystems. It’s good for plant life; it’s good for animals; it’s good for our guests; it’s good for our crews; and it’s good for business.”

Leila Kheiry, KRBD - Ketchikan

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Beyond the Buffet: How Do Cruise Ships Get Rid of Human Waste?

By: Author David Chapman

Posted on Last updated: November 5, 2023

Categories CRUISE PLANNING , LEARN , ONBOARD EXPERIENCE

Cruises promise families a world of fun and adventure, from buffet extravaganzas to exotic shore excursions. But amidst the magic, there’s a logistical marvel often unnoticed: the management of waste on the high seas .

Specifically, how do cruise ships get rid of human waste? Let’s venture beyond the buffet to explore the systems in place that ensure both our comfort and the ocean’s health.

How Do Cruise Ships Get Rid of Human Waste: The Short Answer

Cruise ships deal with “ black water ,” which is human waste from toilets, clinics, and critter pens. All of this waste is packed with germs and junk, which, if tossed directly into the ocean, can definitely harm its ecosystem. Fortunately, rules and systems are in place to handle this procedure correctly.

Sewage treatment plants are among the systems used before discharging to combat and reduce pathogens and contaminants that blackwater can produce. Human waste collectively gets stored in holding tanks and most often gets disposed of in port facilities. 

The Advanced Wastewater Treatment System (AWTS) is the most environmentally friendly procedure – using multiple processing stages to remove all the pollutants. This now “purified wastewater” is then either reused on the ship (not for drinking purposes) or responsibly discharged into the ocean or at a port facility.

But for more details on the fascinating process, read on. 

Cruise Ship Wastewater Separation: How Does It Work?

Cruise ships churn out tons of wastewater, and it’s not your regular H2O. Because they house so many passengers and crew, they can generate around 1000 cubic meters of wastewater daily . It mixes toilet material, kitchen muddles, chemicals, and debris from sinks and showers.

So, of course, there are rules categorized for the three types of wastewater: 

• Black water – from toilets and kitchens –  is often the collection of sewage, food particles, medical waste, and more. Cruise ships handle blackwater with tanks and pumps. They collect it by gravity or vacuum, with strainers to nab any solids. Attached pumps move it to screen presses, separating the gunk from the liquid for treatment. 
• Grey water – from sinks and showers – is often a soapy and greasy collection. Cruise ships handle greywater with a hi-tech system. It screens out both the big and tiny debris, then uses bio and chemical approaches to clean it up. The result? Clean greywater that stays within nature’s limits.
• Bilge water –  from what collects at the lowest part of the ship’s hull – is often the oily contraption from the ship’s engines, as well as a sludge buildup from seawater and freshwater leaking into the bilge wells. Bilge water on cruise ships goes through these steps:
• Collection: They gather it in the bilge wells, the ship’s basement, where the sides meet.
• Separation: Operators now run it through an Oily Water Separator (OWS), which cleans out oily stuff – some systems also use a triple-filter system.
• Measurement: They check it’s clean – less than 15 parts oil per million parts water.
• Discharge: Only clean water goes into the ocean far from the coast. The rest gets another cleaning round – some cruise ships even go the extra mile with two OWS systems for added environmental safety.

Most cruise ships, though, are incredibly innovative and recycle some wastewater for things like cleaning decks or flushing toilets. It saves on fresh water and helps the planet.

What Do Cruise Ships Do With Sewage?

Sewage, being a mix of wastewater and human waste, comes in either a liquid or solid state. Solid includes paper, plastic, food scraps – the bulky stuff. Liquid is water from sinks, showers, toilets, plus any chemicals. 

The critical thing to remember here is that no ship can dump whatever they want, wherever they want. They are subject to criminal penalties if caught doing so. Cruise ships need to follow rules based on where they sail and what sewage they’ve got.

Solid waste gets its own tanks. It’s squeezed down and dried up. Some are burned on board, and some are offloaded for recycling or disposal. Records on how much solid waste is generated, as well as disposed of, is a mandatory requirement by law. 

Liquid waste splits into greywater and blackwater groups. Greywater is legally allowed to be disposed of at sea just over three miles from land after it has been treated. Cruise ships handle their black water in two ways: at port or at sea. It’s a choice based on a few things: port facilities, location, rules, and how clean the water is.

• Port action: Some ships like to dock and hand off their black water to the land-based sewage system. It’s greener and follows strict rules in some spots. But not all ports are ready for it, and it can mess with schedules.
• At sea: Others go for ocean disposal, which saves time and money – but only under the correct conditions. If human waste is not treated correctly, it’s a no-go for the environment. Thus, strict rules apply here; maintaining a distance of 3.5 miles from shore according to US laws is one of them. But they all vary depending on the jurisdiction and environmental protection laws.

Who Enforces the Rules?

Several different agencies and departments actively work to monitor and enforce the rules regarding handling wastewater. These include the U.S. Coast Guard, the Environmental Protection Agency (EPA), and the Department of Justice.

Here are some notable examples of rules enforcement at work:

• Holland America Line Operating Company Agrees to Plead Guilty to Illegal Discharge of 20,000 Gallons of Untreated Sewage into Juneau Harbor (December 2004)
• Princess Cruise Lines to Pay $40 Million Fine for Illegal Dumping (December 2016)
• Carnival Cruises to Pay $20 Million in Pollution and Cover-Up Case (June 2019)
• Holland America fined $17K over greywater dumping in Glacier Bay (September 2019)

Black Water Treatment On Cruise Ships

Black water treatment on cruise ships is all about cleaning up sewage before it hits the ocean. Different ships use different sewage treatment plants (STPs) based on their size and design.

• Marine Sanitation Devices (MSDs): Old-school STPs that grind waste, disinfect with chlorine, and remove excess chlorine before releasing it – not excellent at reducing organic matter and may create nasty by-products.
• Membrane Bioreactors (MBRs): Advanced STPs that use biology and membranes to clean. Bacteria break down waste, membranes filter out the gunk, and UV light or ozone sterilizes it, producing top-notch clean water.
• Advanced Wastewater Treatment Systems (AWTS): The eco-champion of STPs. It has stages for separating solids, breaking down waste, removing contaminants, and recycling water for non-drinking purposes – saving up to 80% of water and reducing waste.

Behind the Scenes: Cruise Ship Kitchen Operations

Understanding Advanced Wastewater Treatment On Cruise Ships

Cruise ships confront the challenge of wastewater, a complex mix of organic and inorganic contaminants that, if released untreated, can harm the marine environment and public health. To address this, vessels are equipped with sophisticated Advanced Wastewater Treatment Systems (AWTS) capable of purifying wastewater before it’s discharged into the sea.

AWTS represents a multi-faceted approach, leveraging biological, physical, and chemical processes for onboard wastewater treatment. The choice of AWTS type—whether membrane bioreactors, activated sludge systems, or reverse osmosis systems—depends on the vessel’s design and capacity. Nevertheless, all systems share common stages, including:

• Pre-treatment: This phase encompasses the removal of large solids, such as paper, plastic, and food scraps, through processes like screening, grinding, and filtering. These actions prevent potential clogging and damage to downstream treatment equipment.
• Biological treatment: Microorganisms like bacteria and fungi are employed to decompose organic matter and nutrients present in wastewater. These microorganisms metabolize organic material into carbon dioxide, water, and biomass. The biomass is subsequently separated from the treated water through sedimentation or filtration.
• Disinfection: Chlorination or ultraviolet radiation is applied to eliminate any remaining pathogens like bacteria and viruses within the treated water, ensuring its safety for discharge or reuse onboard.
• Post-treatment: This stage involves adjustments to the water’s pH, removal of excess chlorine, or the addition of chemicals to enhance the quality of the treated water, aligning it with international standards and regulations governing discharge or reuse onboard.

AWTS is engineered to produce effluent cleaner than what’s typically found in municipal wastewater treatment plants on land. Notably, the Cruise Lines International Association (CLIA) reports that 99% of new ships on order are equipped with AWTS, bringing the global capacity to 78.5%. Presently, 70% of the CLIA’s oceangoing cruise line fleet capacity relies on AWTS, marking a 5% increase over 2019.

The implementation of AWTS underscores the cruise industry’s dedication to environmental responsibility and innovation, minimizing its impact on marine ecosystems and safeguarding human health while providing an exceptional experience for passengers and crew members.

Do Cruise Ships Reuse Waste Water?

Cruise ships, those colossal floating cities, are thirsty for water. They use it for everything, but they can’t tap into pipes like on land. They either make their own from seawater or store it. And they’ve got to deal with the water mess left behind by passengers and crew.

Cruise ships work some water magic to stay in the good books of environmental regulations and be savvy with resources. They treat the water based on what it is.

Greywater gets cleaned up with physical and biological methods. Then, it’s used for things like flushing toilets or washing decks. Some high-tech ships take it further, making it safe to drink.

Black water needs a more complex treatment involving disinfection, nutrient removal, and sludge management. After that, it might find a new life for non-drinking uses like cooling the engine or getting released into the sea under strict rules.

And it’s not just about cleaning up. Cruise ships are water-saving champs. They use low-flow and air-powered faucets and teach passengers and crew to be water-wise. Every drop counts, and they even collect rainwater and AC condensation.

Treating and reusing water isn’t just about being responsible; it’s also a smart financial move and a nod to environmental stewardship.

How Cruise Ships Follow Environmental Standards

Cruise ships operate within a healthy framework of environmental strategies – demonstrating their dedication to environmental responsibility. Oversight from the major leagues like the International Maritime Organization (IMO), the US Environmental Protection Agency (EPA), and the European Union (EU) brings compliance to both national and international environmental laws.

For environmental sustainability, the pursuit starts with cruise ships committing to reducing global carbon emissions – aiming to achieve the IMO’s zero-emission target . They employ advanced tech and practices to boost fuel efficiency and reduce greenhouse gas emissions simultaneously – a must for the cruise industry. 

These include next-gen air quality systems and propulsion systems applying liquefied natural gas (LNG) as the main focus. Still, more innovative moves towards the change include shore power connections, optimized hull designs, speed management, and energy conservation measures.

Operating in ecologically sensitive areas, like the Norwegian World Heritage Fjords, requires strict adherence to environmental regulations. Cruise ships must meet specific criteria regarding fuel sulfur content, nitrogen oxide emissions, water discharge from scrubbers, incinerators, black and grey water treatment, and anti-vapor plume devices. 

More than just a fancy voyage – they tackle serious stuff too – waste control, clean ballast water, noise reduction, marine life care, and even educational programs. No ordinary gig!

Cruise lines adhere to industry best practices and standards as part of their ongoing commitment to reduce their environmental footprint and act as responsible ocean stewards.

David Chapman

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Environment  | Juneau  | Local Government  | State Government  | Tourism

Why cruise ship wastewater helps and hurts Juneau’s sewage treatment utility

April 13, 2021 by Jeremy Hsieh, KTOO

The City and Borough of Juneau has agreed to pay $64,000 in fines to state environmental regulators for repeatedly discharging dirty water from its two main sewage treatment plants. They’ve also promised to take steps to clean up the treated water they pipe into the environment, as well what goes down the drain in the first place.

Here’s what went wrong at the downtown plant, and why Juneau can both blame and thank the cruise industry for its contributions.

Raw sewage from downtown Juneau and Douglas gushes through a newer headworks building at a city treatment plant. It’s noisy and doesn’t smell great. A couple of machines continuously dip and pull a series of plates that look like stainless steel cheese graters. They’re screening out bits of trash before a much trickier stage of treatment.

But this plant isn’t just for city sewage. Up to four cruise ships at once can also offload their wastewater into this system. In the last pre-pandemic summer, cruise ships left behind nearly 20 million gallons of wastewater — more than triple the amount from just five years earlier.

Even so, the cruise ships aren’t pushing the plant anywhere close to its capacity limits. At least, not by volume. In the summer in 2019, the plant operated at about a third of its design capacity of 2.8 million gallons per day.

But the wastewater the cruise ships unload with the city is often harder to treat than regular municipal wastewater. Experts the city hired found that surges of “high-strength” cruise ship waste were one likely culprit for most of the violations at the Juneau-Douglas Wastewater Treatment Plant in recent years. Too much partially treated sewage was getting through and being piped into Gastineau Channel.

City wastewater engineer Lori Sowa explained why those surges are problematic.

“Most of the treatment that happens here relies on a community of microbes that naturally grow within the wastewater,” she said. “It’s not just one bacteria or one microbe, it’s really a community of microbes that work together to treat the waste,” she said. “And so, just like any biological system, even like, you think about your body — if things change, then you can get sort of out of whack.”

There were two specific pollutants the downtown plant had trouble lowering. One is tracked by how much oxygen microorganisms need to break stuff down in water. If it’s too high, there’s no oxygen left for fish and other marine life. This happens on a much larger scale when agricultural runoff from the Mississippi River watershed causes huge dead zones in the Gulf of Mexico stretching thousands of square miles .

“It basically sucks the all the oxygen, the dissolved oxygen, out of the water,” said Guy Archibald, the staff scientist at the Southeast Alaska Conservation Council. “You know, life just can’t live there.”

Archibald used to be an environmental chemist who worked on wastewater.

“Yeah, Unfortunately, I used to get a lot of these samples in the lab,” he said with a chuckle.

The other pollutant the city repeatedly ran afoul of was total suspended solids. Before you get grossed out, Sowa said in these cases, it’s likely those helpful, poop-eating microbes. They’re supposed to settle out to the bottom of clarifier tanks, leaving clear water to be disinfected with ultraviolet light for discharge.

But if those solids end up out in Gastineau Channel, they can settle out on the seafloor instead and smother the filter feeders, snails, mussels and crab that live there.

“It’s kind of the basis of the food chain,” Archibald said.

At least, that’s the risk. Sowa said it’s unlikely these intermittent violations or the plant’s proper discharges over time would create a noticeable environmental effect in the channel.

Most of the violations at the downtown treatment plant that regulators reviewed happened in the summer of 2017, when a facility upgrade kept the plant from running normally for months.

After the upgrade, the system handled the regular flow and surges of cruise ship wastewater better. Discharge violations fell off.

But if cruise ship traffic gets back on its pre-pandemic path, the fully operational plant may still run into problems.

Locals may be tempted to think cruise ship wastewater is nastier because cruise ship passengers are, you know, full of it?

Negin Kamali is a spokesperson for Princess Cruises. She wouldn’t go on tape, but replied to questions over email. Kamali said their ships generally try to unload their lowest-strength wastewater first: the stuff from guestroom showers and sinks, then laundry and lastly from galleys and food prep.

This practice fits with the rate structure in the contracts that the city maintains with the major cruise lines. They pay a base rate according to how much they offload that’s the same as what industrial users in town pay . Unlike industrial users in town, the cruise companies pay more, the nastier their wastewater is .

Cruise lines paid the city $1,153,784 for offloading wastewater in the 2019 season, according to city revenue data . So the $64,000 in fines that ratepayers covered aren’t catastrophic. City Manager Rorie Watt said the cruise ships’ money actually helps regular people in town.

“Taking graywater from cruise ships provided a substantial amount of revenue that allowed us to probably keep, you know, land-based Juneau operators’ rates down, maybe even as much as 3, 4, 5, 6%.”

The contracts do give the city discretion to refuse offload requests. That’s one thing Watt said should have happened more during the summer of 2017. Sowa said when the plant is running smoothly, they don’t need to refuse service.

And the actual sewage from toilets? Kamali said their ships usually hold on to that. They can legally discharge it untreated once they’re 12 nautical miles from land. Or treat it on board and discharge closer to shore under permits similar to the city’s.

In 2020, 30 out of 42 large ships registered with the Alaska Department of Environmental Conservation for wastewater purposes had permits to discharge treated wastewater closer to shore.

Kamali said there’s generally two reasons the company’s ships would offload in Juneau: They’re close to maxing out their storage tanks, or their treatment plants aren’t working properly. She said Juneau is like a safety valve that gives them more flexibility. She said the costs are significant, and offloading doesn’t come with any “distinct economic or environmental advantage” over other disposal options.

Juneau is the only regular cruise ship stop in Alaska that provides this service. The Port of Alaska in Anchorage can, but it doesn’t get many cruise ship visits. Juneau’s city manager said the pros and cons vary from ship to ship, and policies from cruise line to cruise line.

“All the ships have, you know, their own issues, their own systems and some ships, you know, as they’re upgrading their wastewater plants like the service more than others,” Watt said. “Some companies like the service more than others and they just thought it was good policy while in port to connect.”

While cruise ships have had a significant impact on Juneau’s treatment system, most of their wastewater goes elsewhere. Former DEC regulator Ed White analyzed data of all the large ships discharging in Alaska waters in 2018. In his report for the Ocean Conservancy , he found in 2018, only about 4% was offloaded for treatment in Juneau.

To better monitor what the cruise ships are offloading, the city has installed sensors and samplers at the four docks where the big ships tie up. Workers at the plant can see how much is flowing in from each dock and how dirty it is in real time.

In its agreement with environmental regulators , the city promises to come up with a new strategy to manage cruise ship sewage. That includes new contracts with the cruise lines for 2022 that will require better information about what they’re unloading before they unload it. And possibly more facility upgrades.

Kamali with Princess said the cruise line and its corporate siblings, Holland America and Seabourn, look forward to working with the city on the strategy.

KTOO is doing a deep dive into sewage this week. In the next story, we’ll learn about a very different set of problems that gunked up the Mendenhall Valley treatment plant. 

Jeremy Hsieh

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Cruise Ship Discharges

Cruise Ship Wastewater Discharges Fact Sheet | PDF Version (2 pp, 288K, About PDF )

EPA's 2004 and 2005 Alaska cruise ship sampling results are now available.

Cruise Ship Discharge Assessment Report

For additional information, please send an e-mail request to [email protected] .

There are more than 230 cruise ships operating world wide. Cruise ships are literally floating cities that provide some of the same services that small cities or towns provide to their citizens. These vessels can carry as many as 3,000 passengers and crew members, and often operate in pristine coastal waters. As the cruise ship industry continues to expand, there is an increasing concern about the environmental impacts of cruise ship discharges, including impacts to water quality.

Some of the waste streams generated by cruise ships include bilge water (water that collects in the lowest part of the ship’s hull and may contain oil, grease, and other contaminants), sewage, graywater (waste water from showers, sinks, laundries and kitchens), ballast water (water taken onboard or discharged from a vessel to maintain its stability), and solid waste (food waste and garbage). There is significant concern about the potential environmental impacts of these waste stream discharges.

EPA's current cruise ship activities include:

• Sewage and Graywater Standards Development Assessing the need for additional standards for sewage and graywater discharges from large cruise ships operating in Alaska.
• Cruise Ship Discharge Assessment Informational page and report examines waste streams generated by cruise ships, specifically, sewage, graywater, oily bilge water, solid waste and hazardous waste.
• Cruise Ship Plume Dilution Study in Skagway Harbor A survey conducted in Skagway Harbor, Alaska in July 2008 to estimate the near-field dilution of treated sewage/graywater discharges from docked cruise ships.

Other EPA cruise ship information and activities include:

• Plume Tracking Study A survey conducted in August 2001 to estimate the dilution of cruise ship discharges into receiving waters.
• Public Hearings Three regional hearings conducted in September 2000 to gather information regarding discharges from cruise ships.
• Hazardous Waste Tracking System A system developed by EPA and the States for assigning one hazardous waste tracking number to each cruise ship that all States would recognize.

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Deadly coral disease sweeping Caribbean linked to water from ships

Researchers find ‘significant relationship’ between stony coral tissue loss disease and nearby shipping

A virulent and fast-moving coral disease that has swept through the Caribbean could be linked to waste or ballast water from ships, according to research.

The deadly infection, known as stony coral tissue loss disease (SCTLD), was first identified in Florida in 2014, and has since moved through the region, causing great concern among scientists.

It spreads faster than most coral diseases and has an unusually high mortality rate among the species most susceptible to it, making it potentially the most deadly disease ever to affect corals. More than 30 species of coral are susceptible. It was found in Jamaica in 2018, then in the Mexican Caribbean, Sint Maarten and the Bahamas , and has since been detected in 18 other countries.

In Mexico, more than 40% of reefs in one study had at least 10% of coral infected by SCTLD, and nearly a quarter had more than 30%. In Florida, regional declines in coral density approached 30% and live tissue loss was upward of 60%.

Scientists have not yet been able to determine whether the disease is caused by a virus, a bacterium, a chemical or some other infectious agent, but the peer-reviewed study in the journal Frontiers in Marine Science supports the theory that ballast water from ships may be involved. Conducted in the Bahamas by scientists at the Perry Institute for Marine Science, it found that SCTLD was more prevalent in reefs that were closer to the Bahamas’ main commercial ports, in Nassau and Grand Bahama, suggesting a likely link between the disease and ships.

Judith Lang, scientific director at the Atlantic and Gulf Rapid Reef Assessment project, which has been tracking the disease, said: “The prevailing currents in the Caribbean push seawater to Florida and not in the reverse direction, and the predominant wind direction is westward. So human dispersal [to those three territories] in 2018 seems necessary.”

In 2017, the spread of deadly pathogens by ships when they discharge ballast water prompted the International Maritime Organization to implement the Ballast Water Management Convention, which requires that ships discharge their ballast water – used to maintain the ship’s stability – 200 nautical miles from shore in water at least 200 metres deep before entering port, to ensure they do not bring in harmful foreign pathogens.

In the Bahamas, SCTLD has spread rapidly since first being identified in December 2019.

Krista Sherman, senior scientist at the Perry Institute and a co-author of the recently published paper, said: “The disease is spread along about 75km of reef tract, about 46 miles – so for Grand Bahama that is a large structure of reef. We’re talking about mostly covering the entire southern coastline of the island.”

The disease is also widespread in the coral reefs of New Providence, where the Bahamas’ capital, Nassau, and main port are located. The study notes the presence of international container ships, cruise ships and pleasure boats at that location, as well as a fuel shipping station.

Infection rates among the most susceptible species were 23% and 45% across New Providence and Grand Bahama respectively, and recent mortality rates have reached almost 43%.

With the exception of two species, the researchers found “there was a significant relationship” between the disease and proximity of reefs to the major shipping ports. They noted “an increasing proportion of healthy colonies as distance from the port increased on both islands, and a greater proportion of recently dead colonies closer to the port than farther away”.

The locations where SCTLD is prevalent in the Bahamas are all popular with tourists, recreational fishers and divers, Sherman said.

There are concerns that the coral disease could affect the country’s main fishery export, spiny lobster, said Adrian LaRoda, president of the Bahamas Commercial Fishers Alliance. Although the lobster fishers work further out to sea, the industry would be affected if the reefs die. The spiny lobster fishery brings in $90m (£66m) a year and employs 9,000 people.

“Any negative impact on our reefs would definitely drastically affect our spiny lobsters because the mature animals migrate [from the reefs] to the fish aggregating devices [a technique for catching fish],” LaRoda said. He added that the lobsters’ reproduction rate and the food supply for juvenile lobsters in the reef would also be affected.

The Bahamian government has set up a national taskforce to tackle the problem. Currently, the most effective treatment for the disease is the application of the antibiotic amoxicillin directly to the corals, which has seen some success in reducing mortality, but no realistic permanent solution is available.

According to Lang, rather than treating the symptoms, there is a need to tackle the possible human-made causes. “Given a chance, nature can heal naturally,” she said.

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Studying Challenges to Cozumel’s Coral Reefs

TNC and Nat Geo extern Sophie Dellinger examines the impacts of poor water quality on Cozumel's reefs.

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This story is part of a series designed to introduce the perspectives of alumni from the National Geographic Society and The Nature Conservancy’s global youth externship program . Each guest author is an emerging leader in conservation and storytelling.

Cozumel, Mexico is a small island on the Eastern side of the Yucatan Peninsula with a total population of 88,000 . The island is part of the greater Mesoamerican Barrier Reef system and has some of the most diverse reefs in the world with over 35 endemic species of coral.

As a result of those reef conditions, Cozumel became well-known in the diving community as a “must-see” dive location. 

My dad, the person who introduced me to diving, frequently tells me stories of his adventures as a young dive master in the 1990s and never fails to mention that his all-time favorite diving location was Cozumel. My childhood was filled with stories about its wonder: times when he would jump in the water and the only thing he could see in front of him was the silvery shine from the large schools of fish. The first time my dad saw a hammerhead shark was diving at Santa Rosa Wall where he saw hundreds of them schooling.

 In 2021 after the COVID-19 quarantine period, I decided to get scuba certified and finish my open water dives in Cozumel. My first open water dive was behind my hotel on the Villa Blanca Reef, less than one mile away from the cruise ship docks. I was so excited to jump in the water for the first time in Cozumel to finally see what my dad had been describing for years, but when I reached the sandy bottom it was barren and what little coral was left was covered in algae.

Why This Project?

Scuba diving made me fall in love with the ocean and instilled in me a drive to protect it. Inspired by Cozumel, I decided to apply for an ocean conservation externship with TNC and the National Geographic Society in the summer of 2023. The main focus of the externship was a research project of our choosing. I chose Cozumel’s reefs and began having conversations with my dive masters on what was causing reef destruction. It was through these conversations with locals that I was able to learn about the increase in volume of cruise ships and ultimately decided to focus my research on the impacts of the cruise industry on Cozumel’s reefs.

Become An Extern 

Join hundreds of global youth who are connecting with the National Geographic Society and The Nature Conservancy.

What’s the Problem?

Over 80% of Cozumel’s coral population has died in the last 40 years as a result of tourist development on the island, specifically cruise development. Due to its close proximity to the resort town of Cancun, Cozumel began constructing its first cruise pier in the early 1970s. Cozumel now has three cruise piers, the International Pier, Punta Langosta, and Puerta Maya, and has become the largest cruise destination in the Western Caribbean with close to 5 million visitors annually . 

In 2020, the Mexican Ministry of Environment and Natural Resources approved a proposal for the construction of a fourth cruise pier in Cozumel despite the fact that current cruise piers are only reaching 54% of their total capacity . The fourth cruise pier is projected to be built on a UNESCO heritage site where local advocacy groups who have surveyed the region found 20 different species of coral, including two on the critically endangered list . The construction of the fourth pier is largely feared by locals who have seen how the current rate of cruise activity has already caused an ecological imbalance for coral reefs. 

Over 97% of coral populations around current cruise piers have died. In an Atlantic and Gulf Rapid Reef Assessment (AGRRA) survey done in 2022, only one dive site left in Cozumel was ranked as “very good” on the Healthy Reef Index (HRI) . Over 71% of Mexico’s total reefs are listed as being in poor or critical shape on the HRI. 

Cruise Ship Impac ts on Coral Reefs

There are three primary impacts that cruise ships have on the reef: the dumping of untreated sewage, the spread of coral diseases, and direct damage. 

Many cruise ships do not have advanced wastewater treatment systems and instead dump their gray water and untreated sewage directly into the ocean. Untreated sewage is high in nutrients such as nitrogen and phosphorus . An imbalance in the amount of nitrogen and phosphorus initiates a process called water eutrophication, or an excess of algal and plant growth. An increase in fleshy macroalgae (FMA) is one of the main culprits for coral death in Cozumel. 

Macroalgal domination starves coral of the sunlight needed to continue growing its calcium carbonate skeleton. The 2022 AGRRA report shows that Mexico has 24% FMA cover, considered a “critical” level, and would need a 77% decrease of FMA to be ranked “good” on the HRI. Water sampling done by CCRRP confirms that water quality around the island is poor, contributing to declining coral populations.

Another issue caused by cruise ships is the spread of coral diseases. 

Cruise ships have a ballast tank to promote hydrostatic stability of the ship. Water is taken in to the ballast tank at an initial port and expelled into the destination port during docking. Most Caribbean cruises from the US begin in Florida where there is Stony Coral Tissue Loss Disease (SCTLD) and White Band Disease. White Band Disease was brought to Cozumel in the 1980s and has primarily affected elkhorn corals which are currently at risk of becoming extinct in Cozumel. 

In October 2018, an outbreak of SCTLD brought by a cruise ship ballast water from Florida caused 60% loss of Cozumel’s hard corals in one year . SCTLD is believed to be caused by bacterial pathogens in the water column that create lesions on hard corals filled with alpha-toxins ultimately killing coral cells. The presence of SCTLD permanently alters the microbial community as bacteria levels remain high , leaving corals vulnerable as they continue to fight off the disease. This means that corals that don’t look sick may still be at higher risk of death or collapse as they are fighting off higher levels of bacteria in the water column.

Finally, anchoring and the backwash of propellers causes significant direct damage to corals. Anchors frequently smash hard corals, leading to a shift from live corals to macroalgal domination . One cruise ship ran awry 40 miles north of Cozumel and damaged 80% of Cancun’s total coral population. The impacts of cruise ships on coral reefs have left Cozumel’s remaining coral populations vulnerable. Remaining coral colonies are at higher risk of collapse due to limitations in sexual reproduction, genetic recombination, and the ability to adapt to rapidly changing environments because of weaker immune systems.

Solutions 

Cozumel should focus on reducing its FMA cover through improving water quality around the island. Decreasing levels of nutrients in the water can be done through the installation of port reception facilities (PRFs). PRFs collect sewage and marine litter for proper treatment at water treatment facilities. Cozumel can receive funding through the International Maritime Organization’s Technical Cooperation Fund to install IMO-approved PRFs. After the installation of PRFs, Cozumel should follow the Baltic Sea Model . In 2019, the IMO banned all cruise ships from dumping raw sewage within 12 nautical miles of shore in the Baltic Sea in order to improve water quality. All ships are required to utilize PRFs or dump sewage farther from shore.

To address the spread of coral diseases, ballast management protocols must be adopted by all cruise lines. Key protocols include the prohibition of gathering ballast water in “hot spot” zones of coral disease, rinsing of the anchor and anchor chain during every retrieval, conducting ballast exchange at least 200 nautical miles away from land, and keeping records of all ballast information to report at all ports. Additionally, the funding of local coral restoration programs helps fuel research for technologies aimed at limiting the spread of coral diseases and the repopulation of threatened coral populations.

Recovery and restoration are possible. Cozumel Coral Reef Restoration Program (CCRRP) has restored over 10,000 corals to the Villa Blanca Reef and has developed antibiotic pastes to limit the spread of SCTLD.

Finally, Cozumel needs to limit the amount of cruise ships docking at their ports if they wish to preserve the shallow reefs surrounding their island. Lowering the volume of ships coming in and utilizing marine spatial planning (MSP) to create anchoring paths for ships that avoid damaging coral colonies should help mitigate some of the damage being done to the reefs.

While Cozumel’s reefs are facing a significant threat with the growing popularity of cruise tourism in the Caribbean, implementing policies focused on minimizing the impacts of cruise ships may provide some relief for coral. 

By raising awareness through my externship project, I hope to reach tourists who travel to the Caribbean to help them understand the impacts of cruise travel. I also hope that increased awareness on the water quality in Cozumel incentivizes the city council to approve a long-term water infrastructure improvement plan to begin addressing the core issue behind reef degradation in Cozumel.

Discover the conservation work of other externs from Colombia, the Maldives, and the United States in Nature Conservancy Magazine.

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July 29, 2021

Story type: TNC Science Brief

• Environment
• Puget Sound

Cruise season in Seattle starts with a rally against pollution

As thousands of people flocked to the Seattle waterfront on Saturday to embark on the first cruise of the year, climate activists protested nearby demanding the cruise industry do more to address pollution.

From April to late October, nearly 1.7 million “revenue” passengers — which comes out to more than 800,000 unique passengers — are expected to depart Seattle on 276 cruises, Stephanie Jones Stebbins, managing director of the port’s maritime division, said during a news conference Saturday morning.

This year marks the 25th year of cruises between Seattle and Alaska.

She said this cruise season is estimated to provide almost $900 million in economic impact to the city’s tourism and other sectors. The port calculates that each ship that home ports in Seattle has a $4 million impact on the local economy.

“Over the last 25 years, the cruise business has become a significant part of our local economy, contributing to hundreds of businesses and thousands of jobs,” Port Commissioner Ryan Calkins said in a statement.

While thousands of voyagers wove through customs lines at Pier 66 to board the Norwegian Bliss headed to Alaska, members of activist group Seattle Cruise Control rallied outside. The volunteer organization is focused on educating people on the environmental impacts of the cruise industry.

The demonstration included children in sea creature costumes , a live band and a performance by the Red Rebel Brigade, a climate activist performance troupe.

The group wants the port to reduce the number of cruises it sends out and make the route from Seattle to Alaska a no-waste-dumping zone.

The port says it’s committed to being one of the most “environmentally progressive” cruise ports in North America. The current goal is to phase out seaport-related emissions by 2050. Additionally, the port plans to start shore power at Pier 66 this summer, meaning ships can plug into the power supply when docked at the port rather than run their engines, reducing emissions.

Seattle Cruise Control activists say the plan isn’t enough.

Elizabeth Burton, a member of the organization, said she doesn’t believe shore power in Seattle will be an effective solution because a ship plugging in for one stop of its trek only addresses a small percentage of the ship’s overall emissions throughout a trip.

For much of the time, she said, “The cruise ships are still polluting the air and wrecking the climate.”

Burton said she’s sorry that passengers of the Bliss don’t realize the harm being caused.

“We’re not trying to ruin their vacation, but we’d like to raise the consciousness in general,” she said. “Is it really worth wrecking the future for all future generations? So you can go on this trip?”

Standing in the customs line less than 25 feet from the demonstration, David Torok was ready to hop on the Bliss. The Myrtle Beach, South Carolina, resident said he’s hoping to see the northern lights and whatever Alaska has to offer, whales included.

“I’m sorry that people get mad about the cruise boat, but oh, well,” Torok said. “Tell them to go on a cruise. Maybe they’ll change their mind.”

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Santa Barbara limits cruise ship visits to 20 annually

SANTA BARBARA, Calif. - Santa Barbara City Council voted to adopt new rules and regulations for visiting cruise ships including capping the number of ships to 20 per year Tuesday. 

The city currently prohibits cruise ship visits from Memorial Day through Labor Day and on weekends year-round and the city council formalized this current practice.  

Since 2002, the city's cruise ship program has welcomed an average of 15 to 30 visits per year, bringing $3-$5 million to local businesses to aid the economy. 

Tuesday's 6-1 vote comes after months of discussion with community members on evaluating the environmental, economic impacts and regulations that govern the visiting cruise ships. 

The Harbor Commission formed a Cruise Ship Workgroup in April 2022 to review the cruise ship program and  provide recommendations on how to improve the program.  

In addition to the annual cap, the city council supported the new law with recommendation of improving how visiting cruise ships handle wastewater. 

The council directed staff to negotiate and require all visiting cruise ships to be equipped with Advanced Wastewater Treatment Systems (AWTS) by Spring 2025. 

The council also formalized the local requirement of no discharge of any kind within 12 nautical miles of Santa Barbara and reduce speeds when possible, to 10 knots or less within the Santa Barbara Channel Vessel Speed Reduction Zone between May 1 and December 15. 

Council directed staff to work with the Harbor Commission to create a packet of environmental best practices including a template for minimal requirements using industry ratings and scorecards.

The council also asked the Harbor Commission to further discuss the use of pilots for the cruise ships in the channel as well as requirements for smaller ships and the use of cleaner fuel. 

Mayor Randy Rowse supported most of the Harbor Commission's recommendations but ultimately voted no. Rowse expressed worry that the annual cruise ship limit will "take away the competition rather create competition."

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Eight passengers stranded on African island after Norwegian cruise ship left without them

A dream cruise vacation has turned into a nightmare for eight passengers left stranded on the African island of São Tomé and Príncipe after their ship left without them because they were late to return from a private tour.

The tourists — six from the U.S. and two from Australia — were aboard the Norwegian Dawn, a Norwegian cruise line ship , which departed from Cape Town, South Africa, on March 20 for a 21-day voyage up the coast of Africa set to end in Barcelona, Spain, on April 10.

But on Wednesday, the group of eight tourists was late to return to the ship by more than an hour for the all-aboard time of 3 p.m. from a private excursion on the island, which was not organized by the cruise line.

Jay and Jill Campbell of South Carolina were part of the group that was left behind.

They said that their tour’s operator notified the cruise captain that they were going to be late to rejoin the ship and that the local Coast Guard tried to get them on the vessel but that they weren’t allowed to board.

As a result, the couple and the rest of the group have been stranded for days on the island off Nigeria, grappling with language, currency issues and complicated travel to catch up with the ship.

“The lovely people of São Tomé were very gracious, very hospitable. They had reached out as much as they could to help us find hotels,” Jay Campbell said on NBC's "TODAY" show Tuesday morning.

“We were able to get to a tour agency there to arrange flights to the next port of call. ... Very difficult process — you’re dealing with multiple languages, language barriers, you’re dealing with different currencies ... finding someone that even has dollars ... trying to get an agent to understand where we need to get to.

"It’s one of those ‘You can’t get there from here,’" he added.

A Norwegian spokesperson called the incident a “very unfortunate situation” and said, “Guests are responsible for ensuring they return to the ship at the published time.”

The cruise line said that after the guests failed to return, their passports were delivered to local port agents, in line with protocol. The company said it was working with local authorities to understand “the requirements and visas needed for the guests to reboard the ship at the next available port of call.”

On Monday, the guests had made arrangements to rejoin the ship in Banjul, Gambia, but the ship was unable to safely dock there because of “adverse weather conditions” and “tidal restrictions,” Norwegian said. The guests were then contacted and provided with information to rejoin the ship at Dakar, Senegal, on Tuesday. 

Jill Campbell said they traveled through seven countries in 48 hours to arrive in Senegal on Monday night.

But the couple was reconsidering whether they even wanted to return to the cruise.

"We are considering whether or not we are going to board the ship. It is in dock here in Senegal," she said. "We believe there was a basic duty of care that they had forgotten about, so it does concern us."

"After what we witnessed, we truly believe that although there’s a set of rules or policies that the ship may have followed, they followed those rules too rigidly. I believe that they really forgot that they are people working in the hospitality industry and really the safety and well-being of the customers should be their first priority," she added.

Ultimately, the eight passengers did rejoin the cruise before 8:30 a.m. ET Tuesday in Dakar, Senegal, Norwegian told NBC News in an e-mail Tuesday evening, after this story originally published.

Norwegian said the passengers were responsible for making their own travel arrangements to rejoin the ship.

"Despite the series of unfortunate events outside of our control, we will be reimbursing these eight guests for their travel costs from Banjur, Gambia to Dakar, Senegal," a cruise line spokesperson said in a statement. "We remain in communication with the guests and are providing additional information as it becomes available."

A silver lining of the catastrophe was that the Campbells were able to connect with another Norwegian Dawn passenger — Julia Lenkoff, 80 — who was also left on the island, but for a medical reason.

Lenkoff was on a different day tour Wednesday. She had "medically disembarked" from the cruise to seek local treatment on that day, Norwegian said.

Norwegian said that its care team tried to call Lenkoff several times and was unable to reach her and that it worked with its port agent in São Tomé and Príncipe for updates on her health.

The Campbells met Lenkoff and were able to put her in contact with her family in California, who flew her home — a move Lenkoff's daughter said "saved her life."

"She's a world traveler. She travels all the time. So this was going to be one of her bucket list trips, because she's been to 120 countries so far, and she wanted to get to 130," her daughter, Lana Lenkoff Geis, said in an interview that aired Tuesday on "TODAY."

Norwegian said Lenkoff was escorted on a flight to Lisbon, Portugal, then put in the care of airport staff members to continue her journey back to the U.S., where she has safely returned.

Breaking News Reporter

20-year-old man missing after jumping off a Royal Caribbean cruise ship, report says

• A 20-year-old man on holiday with his family went overboard from a Royal Caribbean cruise. 
• The man, who's been missing since early Thursday morning, may have jumped, a report said. 
• The US Coast Guard has launched a search operation. 

A 20-year-old man who was vacationing with his family on a cruise may have jumped overboard, The New York Post reported.

Royal Caribbean confirmed that a passenger, whose identity has not been revealed, went overboard near The Bahamas at about 4 a.m. on Thursday and has been missing since then.

The US Coast Guard launched a search for the passenger on Thursday.

A Royal Caribbean spokesperson told Business Insider that the cruise line's "Care Team is providing support and assistance to the guest's family during this difficult time."

Bryan Sims, a fellow cruise passenger, told The New York Post that he'd hung out with the passenger in the hot tub until 3:30 a.m. Sims said the man appeared to be "pretty drunk."

Sims told the Post that after leaving the hot tub, they encountered the passenger's father while approaching the elevators.

"His dad was fussing at him for being drunk," Sims said.

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Deborah Morrison, another passenger on board the cruise, told the Post that "there was a lot of yelling and that the crew was alerted immediately."

"The ship's crew immediately launched a search and rescue effort alongside the US Coast Guard, who has taken over the search," the Royal Caribbean spokesperson said.

#Breaking @USCG crews are searching for a 20-year-old man who went overboard from the Liberty of the Seas cruise ship 57 miles from Great Inagua this morning. USCG Cutter Seneca and Air Station Miami HC-144 crews are conducting the search. #USCG #SAR pic.twitter.com/zZPpKOdyCn — USCGSoutheast (@USCGSoutheast) April 4, 2024

The Liberty of the Seas departed from South Florida and was 57 miles from Great Inagua in The Bahamas when the passenger went overboard.

The cruise ship has 18 decks and can accommodate up to 3,634 passengers. It's served by a crew of about 1,300.

The chances of falling overboard on a cruise ship are extremely low .

In 2023, about 31 million passengers traveled on a cruise, and at least 10 people went overboard, with two of them surviving, Business Insider reported .

"Even one incident is one too many," a spokesperson for Cruise Lines International Association told Business Insider, adding that "the vast majority of cases are either reckless behavior or some form of intentional act. People don't just inadvertently fall over the side of a ship."

Last month, a 23-year-old man who felt seasick fell overboard from the MSC Euribia cruise ship while crossing the North Sea in Europe and was presumed dead.

In December, an MSC Cruises passenger jumped from one of its ships while sailing from Europe to South America.

According to a CLIA report, only 28.2% of passengers who fell overboard between 2009 and 2019 were successfully rescued.

Watch: Sub taking tourists to see the Titanic goes missing

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