Just before the municipal elections, a controversy arose regarding the possibility of denying cruise ships access to water in Spanish ports, using drought and water scarcity as justification. Conversely, the cruise industry is investing in increasingly sophisticated water production and conservation systems, striving for self-sufficiency.
Article from CruisesNews magazine no. 66 – September 2023
A cruise ship carries an average of 2,000 to 3,000 passengers. With so many people on board, week after week, you've probably wondered how the demand for fresh water for so many people (including the crew) is met on cruise ships. The average consumption of fresh water on these ships can vary between 500 and 1,000 tons per day, although it obviously depends on the size of the ship and the route.
Water Requirements Aboard a Cruise Ship
A modern cruise ship is unfeasible without fresh water. It is needed in the hotel section of the ship for drinking, cooking, laundry, washing, and high-pressure cleaning; in the technical section for steam production, various heating and cooling systems inside and outside the engine room, fire sprinkler systems, and for recreational purposes (swimming pools, spas, jacuzzis, and water slides).
With such high consumption, it is imperative that cruise ships be equipped with freshwater production and storage facilities. Regarding water production, the two most commonly used systems are vacuum evaporators and reverse osmosis plants.
Evaporators:
Vacuum evaporators use the cooling water from onboard diesel engines (or another heat source, such as steam) to produce fresh water. This water, like that in a car, is at 70-80°C, and to "boil" seawater, it must be done under vacuum conditions. The problem with their operation is that the propulsion equipment must be in use, and they usually require a considerable amount of space, near or inside the engine rooms. This location helps utilize the heat from the engine water, reducing the length of pipes and insulation; avoids pumping costs; and improves circulation.
On cruise ships, 3- or 4-stage evaporators are typically used, with at least two installed. The resulting water purity is around 10 ppm. A single evaporator can produce anywhere from 600 m³/day to 2,000 m³/day, depending primarily on the seawater temperature and the diesel engine's operating conditions. Evaporators are mainly used because they produce water with lower conductivity than a reverse osmosis system. This water can be used as technical water, such as boiler feedwater, although there are no significant differences between the two for other applications.
Cruise ships produce more than 90% of the fresh water they consume.
Reverse
osmosis (RO) is another method for producing fresh water from seawater on board a cruise ship. A typical RO plant is a compact unit, taking up much less space than a flash evaporator. It doesn't require diesel engines to be running, as it only consumes electricity, not heat. RO plants typically have a capacity of 12-15 m³/h, depending on the seawater quality and the condition of the filters. They usually operate in two stages: the first produces fresh water for recreational uses, laundry, etc., and the second produces fresh drinking water.
Essentially, an RO system produces fresh, technical water from seawater, using high-pressure pumps and sophisticated water filters, and other treatment components such as pre-sand filters, anti-scaling treatment, pre-filters, etc.
Among the problems of use are: the need for a high pressure circuit (50-70 bar), the need to change the membranes periodically to maintain water production and quality; and the brine produced.
For example, the latest MSC Cruises ships have reverse osmosis systems capable of producing around 2,000 m³/day. The most modern ship in the fleet, the MSC Euribia, has a reverse osmosis system capable of producing 2,700 m³/day of fresh water, enough to fill an Olympic-sized swimming pool and provide it with three days of autonomy in the event of a shortage of potable water.
Water Consumption in Port Networks:
Despite the installation of evaporators and reverse osmosis membranes, water consumption poses a challenge for cruise ships, especially on routes with numerous port calls, which is common in the Mediterranean. For example, all ships based in Barcelona offer itineraries with only one day at sea. Ships spend considerable time in port, averaging 8 to 10 hours docked, sometimes reaching up to 12 hours. Furthermore, the time spent maneuvering and near coastal waters must be considered, as producing potable water there is impossible due to shallow draft and the potential presence of land-based impurities. The ship must wait until it is at least 4 nautical miles offshore to start the evaporators, and even then, they are generally only used to fill the technical water tanks until the ship reaches deeper, cleaner waters where it is safe to switch production to the potable water tanks.
Reverse osmosis plants are generally started with a minimum depth of 50 meters to avoid any risk of fouling the filters or damage to the membranes.
It is clear that ensuring a supply of fresh water must be a cornerstone of any home port service, given that a modern cruise ship is unfeasible without water.
Given this scenario, it's normal for cruise ships to take on fresh water weekly or as needed. This is usually done at the ship's home port, either by connecting the ship to the port's water distribution network or by using a water tanker.
The USPH requires verification of the quality of the potable water supply before it is delivered to the vessel, and a written declaration of the chlorine content and pH must be issued. Typically, the vessel filters, chlorinates (to 2 ppm), and adjusts the pH of the additional supply water before filling the freshwater tanks. Since the water supply flow rate can be quite high, approximately 250–300 m³/h, manual tests for chlorine content and pH must be performed hourly during water loading to ensure the water is being chlorinated according to USPH standards.
Last June, the Carnival Elation suffered a serious malfunction in its freshwater production system, forcing the ship to make an emergency stop in Cape Canaveral to continue its five-night cruise from Jacksonville, shortening its stop in Nassau. This occurred despite the ship having already taken on freshwater in Jacksonville, its home port. Furthermore, the Carnival Elation uses saltwater in its pools and jacuzzis.
Studies of consumption in ports
In June 2020, the Balearic Port Authority (APB) offered some very interesting data on the water consumption of a cruise ship in the ports it manages.
According to these figures, each cruise passenger consumes an average of 90.49 liters of water per year during a stop in Palma de Mallorca. In 2019, 200,895 cubic meters of water were supplied to cruise ships in the Port of Palma, carrying a total of 2,220,135 passengers. According to data from the Port Authority of the Balearic Islands (APB), this consumption has decreased in recent years. In 2016, the Port of Palma supplied 178,068 tons of water to cruise ships, which carried 1,631,206 passengers, averaging 109.16 liters per passenger.
In 2017, the annual average fell to 90.03 liters per cruise passenger, with 150,632 tons for 1,673,210 passengers, while in 2018 the average reached its lowest point with 79.55 liters per passenger per year, with 163,226 tons of water supplied to 2,051,782 cruise passengers.
The State Ports Authority's statistical yearbook does not separate the provisioning of water to cruise ships from that of other vessels. However, the 2021 Yearbook shows that the two ports with the highest volume of water provisioning are Las Palmas and Algeciras, with Barcelona in third place. Tenerife ranks fourth and Cádiz fifth. The volume of cruise ship traffic does not appear to be a determining factor in this provisioning.
Costa Cruises
presented the sixteenth edition of its Sustainability Report. In it, Costa highlighted its ongoing commitment to minimizing water waste on its ships, supporting UN Sustainable Development Goals 6 and 14 within its 2030 Agenda. Specifically, regarding Goal 6, Costa has invested significantly in advanced freshwater generation systems (reverse osmosis) and evaporators, enabling the production of the maximum amount of water possible on board. This aligns with the UN Guiding Principles on Business and Human Rights, particularly concerning the protection of areas experiencing freshwater scarcity due to drought, where “Costa aims to avoid impacting its own water supply to protect the right to access water.” Furthermore, the 2021 Costa Sustainability Report indicates that “Costa trains its employees in the sustainable management of water resources and conducts an awareness campaign for its passengers on board, focusing on the correct and responsible use of water.”
But this philosophy isn't new: in its 2019 Sustainability Report (referring to 2018), Costa already stated that 70.99% of its water was produced on board (0.69% more than in 2017). That document explicitly states that "when a port of call experiences drought, our supply patterns are modified to avoid impacting the local water supply." In 2018, Costa initiated a strategic reduction in cabin cleaning operations (once a day instead of twice), and this initiative led to optimized water usage. One of Costa's priority areas for raising awareness and fostering direct engagement among passengers and crew is the responsible consumption of resources, especially water. Per capita water consumption on board, for example, fell by 4.67% in 2018, partly thanks to the “Stop the Drop” video campaign carried out on all ships to promote the efficient use of water, not only on board, but also at home.
Costa aims to avoid impacting its own supply in order to protect the right of access to water.
The most modern ships in the Costa fleet are undoubtedly the sister ships Costa Smeralda and Costa Toscana. These vessels boast remarkable facilities designed to reduce their environmental impact. Perhaps the most publicized is their use of LNG as fuel, but they also excel in all aspects of water consumption. On these sister ships, 100% of the water consumed is produced directly on board; the dishwashers in their restaurants use 35% less water per day compared to the rest of the Costa fleet; their laundries use 50% less water per kilogram of laundry than the rest of the Costa fleet; and cabin water consumption is 30% lower, thanks to the use of state-of-the-art showers and toilets.
The Costa Sustainability Report 2021 cites an average freshwater consumption of 280 liters per person per day in its fleet, indicating that 90% of that amount is produced on board, and 10% comes from the distribution networks of the ports of call.
Costa Cruises ships also have wastewater treatment systems, also known as Advanced Wastewater Treatment Systems (AWTS). These systems use third-level treatment to generate effluent of equivalent or better quality than that of the most advanced land-based system, and are consistent with CLIA policies. The AWTS implementation rate was 74% in 2021 (a 4% increase compared to 2020).
MSC Cruises
has been publishing its Sustainability Report since 2019. The 2021 MSC Cruises Environmental Management Report highlights the importance of water on board its cruise ships, stating that “a large part of the water used by its fleet is generated on board, generally thanks to reverse osmosis systems.” In the 2022 Report, published last July, the Italian cruise line specified this figure, indicating that in that year MSC Cruises ships produced 88% of the 4.8 million cubic meters of fresh water consumed on board. That report emphasized that, in addition to drinking water, MSC Cruises ships need fresh water for cooking, cleaning, laundry, and brewing beer on the new MSC World Europa. This ship, the most technologically advanced in the fleet, can produce more than 3,000 cubic meters of fresh water per day.
As part of its Environmental Action Plan, MSC Cruises has set a goal of reducing water consumption on its ships by 3% annually. To achieve this, it has opted for a combination of implementing new production technologies, rigorous consumption monitoring, installing flow-restricting aerators on taps, crew training, and passenger awareness campaigns. In 2021, the MSC Cruises fleet used an average of 246 liters/day/passenger, higher than in pre-pandemic years, because the ships were not sailing at full capacity. However, in 2022, freshwater consumption monitoring systems showed a reduction to 226 liters/day/passenger.
The toilets on the MSC Euribia only use 1 liter of water each time they are used, compared to 10 liters for a land-based model.
Once water has been used, MSC ensures it is treated before being discharged into the sea. All ships in the MSC Cruises fleet have grey and black water treatment plants, allowing them to comply with legal requirements on this matter anywhere in the world. Since 2007, all new ships added to the MSC Cruises fleet have been equipped with water treatment systems that allow them to recover water almost to the point of making it potable, also known as Advanced Wastewater Treatment Systems (AWTS).
The systems installed on the last four cruise ships in the MSC Cruises fleet go even further, rigorously complying with the requirements of IMO MEPC 227 (64), known as the “Baltic Standard.” These are the strictest and most demanding regulations for wastewater treatment and disposal in the maritime industry, comparable to, and in some cases exceeding, the most restrictive land-based legislation. In 2021, thirteen ships in their fleet, representing more than 80% of the fleet's capacity, were equipped with AWTS. Furthermore, the water treatment system is certified annually by SGS.
In 2022, MSC Cruises ships generated 3,530,867 cubic meters of wastewater of all types. Of this amount, 65.3% was treated using AWTS; 31.8% was greywater; 2.6% was treated bilge water; and 0.3% was untreated bilge water.
Aida Cruises
, a Carnival group company primarily focused on the German market, has been a pioneer in reducing its environmental impact, for example, regarding the use of electrical outlets in ports (OPS). It published its first sustainability report in 2007. Its most recent comprehensive sustainability report is from 2022, reflecting its management practices in 2021, during the height of the pandemic. Therefore, the most recent full-year data available for Aida Cruises dates back to 2019. Aida Cruises' environmental management report for that year indicated a 6.83% reduction in water consumption per passenger per day compared to 2018.
A key element in reducing water consumption on the Aida fleet is the food waste vacuum system. All ships delivered after 2004 have been equipped with this system, which, instead of using water to transport food waste through pipes, uses a vacuum system to transport the waste directly to a storage tank.
Aida also saves water in the laundry. Thanks to the adoption of new technologies in this area, water consumption has been reduced by 50% compared to 2008. And with innovative car wash tunnels, water consumption has been reduced by another 50%. The onboard toilets require only one liter of water per flush, thanks to the use of a vacuum system.
That same 2019 report stated that the Aida fleet's ships produced 84% of the water they consumed, primarily using reverse osmosis systems. It also projected a 6.8% reduction in water consumption for 2019.
Furthermore, Aida Cruises' reports describe the magnitudes of wastewater generated on board that are either well treated on board or discharged for management on land.
Comparing land-based and onboard fuel consumption:
It is always difficult to draw parallels between onboard fuel consumption and land-based fuel consumption. This is due, among other things, to the fact that the latter does not include consumption from collective activities, such as in a gym, changing rooms, swimming pool, restaurant, etc., or public activities, such as cleaning, transportation, and electricity generation, the consumption of which is included in the figures for a cruise ship.
As part of the Sustainability Plan, MSC Cruises aims to reduce freshwater demand by 3% annually on each of its ships.
That said, consumption figures are within the same order of magnitude. A modern cruise ship with 100% occupancy in lower berths consumes between 150 and 200 liters per passenger per night, while a guest at a Barcelona hotel consumes 163.5 liters per day, a perfectly compatible figure, with the aforementioned exception regarding technical water.
According to the INE, the average water consumption of a Spaniard was 133 liters per day in 2022; in Catalonia it was 117 liters, and in Barcelona 106 liters per day.
There is no data on the reuse of fresh water on land, while the figures on board a cruise ship are very telling.
NCL Holdings
' 2022 Sustainability Report includes a section on water use, emphasizing the increase in onboard production. In 2022, 5,870,000 m³ of water were consumed onboard across all uses on NCL Holdings vessels, of which approximately 5,280,000 m³ (90%) was produced onboard. This is the only report that breaks down the origin of the water generated onboard: 43% from evaporators, 47% from reverse osmosis systems, and 10% from land sources.
The report also makes it clear that NCL Holdings is expanding its use of reverse osmosis systems, with capacities ranging from 250 m³ to 825 m³/day, depending on the size and capacity of the installation. The NCL Holdings fleet has 59 RO installations and is “continuously evaluating additional installations both in its existing fleet and in new constructions.”.
Carnival Corporation,
in addition to the Sustainability Reports published by some of its subsidiaries, also publishes a global report for all of the group's brands. In its 2022 report, it states that 87% of the water consumed on the world's largest cruise line is produced on board the ships, and only 13% comes from land sources.
In this report, Carnival Corp. indicates that treated wastewater from some of its ships is pumped into certain ports for use as garden irrigation water, resulting in savings for the municipalities. Mario Zanetti, president of Costa Cruises, offered Barcelona the possibility of “donating tons of drinking water to Barcelona” as an example of a circular economy.
It also makes clear that Carnival Corp's corporate buildings have a rainwater collection system, which is then used in the toilet flush system, or in the fire suppression system.
Finally, 64% of the Carnival fleet is equipped with AWTS systems, a lower percentage than its competitors Royal Caribbean and MSC Cruises.
Royal
Caribbean's 2021 Sustainability Report dedicates an entire chapter to water, outlining three strategies: increased production, reduced consumption, and comprehensive water treatment. Royal Caribbean uses water aerators, low-flow showerheads, and reduced-flow dishwashers and laundry equipment. They also employ innovative processes on their ships, such as reusing condensate water from air conditioning units in the laundries to wash towels and sheets. Royal Caribbean Group ships produce more than 90% of the potable water they need onboard using both evaporators and reverse osmosis. The new Icon of the Seas will generate approximately 93% of its own water consumption, with RO evaporators/membranes that require 65% less energy than the systems installed on previous Royal Caribbean ships. The largest freshwater production facilities are located on Royal Caribbean ships. For example, Oasis-class vessels are capable of producing 4,100 m³/day with a combination of evaporators and reverse osmosis membrane systems. Voyager-class vessels produce 2,100 m³/day.
Thanks to these actions and initiatives, the average water consumption of Royal Caribbean passengers in 2019 was 250 liters/day, 128 liters less than the average for a typical North American. The last Oasis-class ship delivered to Royal Caribbean, the Wonder of the Seas, was delivered in 2022 with a projected water consumption of 170 liters/day/passenger.
Regarding wastewater treatment, Royal Caribbean committed in 2004 to installing Advanced Wastewater Treatment Systems (AWTS) on all its ships. Currently, that figure has reached 92%. These tertiary systems treat wastewater and greywater, including water from sinks, showers, and kitchens, to standards twice as stringent as those of the United States Public Health Service (USPH). Royal Caribbean guarantees that it checks this wastewater daily to verify compliance, and that an independent third party conducts a quarterly inspection.
The efforts aimed at self-sufficiency in this area by the cruise industry should be recognized by society by guaranteeing the supply.
Treatment of Freshwater Produced on Board:
However, water produced on board, whether by an evaporator or a reverse osmosis (RO) plant, is not suitable for direct consumption, as it lacks minerals and taste. Therefore, the water requires further treatment, including passing through mineralizers, treatment with carbon dioxide, and chlorination for disinfection.
United States Public Health (USPH) standards require that the free chlorine concentration be 2 ppm within the first half hour after the start of potable water production and must be maintained between 2 and 2.5 ppm at all times. This must be ensured by testing at least every four hours by the crew.
After mineralization, chlorination, and pH adjustment, the water is transferred to potable water tanks for storage, taking into account the ship's stability. The tanks are rotated so that drinking water is drawn from the tanks filled first, and the most recently filled tanks are used last, allowing the chlorine to settle. The drinking water must also be chlorinated according to USPH standards, maintaining a minimum concentration of 0.2 ppm at all times on the ship's top deck. However, most shipping lines raise this figure to 1-1.5 ppm on the top deck, exceeding the USPH standard, to ensure consistent compliance.
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