This Disney video about environmental conservation on
DCL ships provides some clues [and interesting facts]:
https://disneyparks.disney.go.com/b...se-line-plays-its-part-in-water-conservation/
From the article:
"
Whether it’s collecting condensation from the ship’s air conditioning units or using the heat from the ship’s power generators to convert over 142,000 gallons of saltwater into fresh water daily, Disney Cruise Line is committed to minimizing its impact on the environment and conserves water whenever possible."
Points from the video linked in the article:
- heat from the ship's power generators is used to run evaporators to turn "
that salty seawater" into "
clean, fresh water" "
and that is just one of the ways we can transform over 142,000 gallons of water every day" <evaporators suggest distillation>
- condensation from the air conditioners is collected and used to powerwash the ships outer decks, saving more than 30 million gallons of water a year
Also from this DCL "fun facts" document:
http://disneycruiselineblog.com/wp-content/uploads/2012/11/DCL_Env_Fact_Final.pdf similar info about the evaporators:
"
Evaporators: Excess heat from power generators is used to run evaporators transforming tons of sea water into potable water onboard each of our ships, every day."
And about reclaiming the condensation: "
Condensation: Naturally occurring condensation from the ships' onboard air-conditioning units is recycled to supply fresh water for onboard laundry facilitiesand for cleaning the outer decks of the ships, saving tons of fresh water each day. "
THis article also talks about the evaporators on the Magic and Wonder:
https://www.treehugger.com/natural-sciences/7-ocean-friendly-eco-cruises-hitting-the-high-seas.html as does this:
https://safety4sea.com/cruise-industry-environmental-practices-to-conserve-water/
And perhaps they use both distillation AND RO ?
This is an Environmental Sustainabilty report from Meyer Werft, dated before Dream and Fantasy [it talks about them as new ships ordered...]:
https://www.meyerwerft.de/media/pdfs/pdf/EN_Sustainability_Report..pdf
It has a section on
Evaporation systems for fresh water supply
In ports, the fresh water supply for ships comes from bunkering
the water from ashore; by contrast, on the open seas, fresh water
is supplied by evaporating seawater in fresh water generators
specially developed for use on ships. The steam generated in
these systems is then condensed, treated and supplied to the
consumers. The salt that was dissolved in the seawater is left be-
hind in the evaporation process as so-called brine.
To protect the environment, the energy needed by the evapora-
tors comes mainly from the heat emitted by the main engines.
To ensure that the heating effect generated by the engine coo-
ling water offers temperatures of around 90°C, evaporation
takes place under vacuum in flash evaporators. MEYER WERFT
gives absolute priority to energy efficiency in designing these
systems, so that the following procedure has become establis-
hed.
Seawater is sucked in from outside the ship and mixed with non-
evaporated water from the fresh water generator. This recovers
the thermal energy from the brine. The resulting mixture then
runs through heat exchangers installed in the fresh water gene-
rator. The heat exchangers extract the condensation heat in order
to condense the water vapour formed in the fresh water gene-
rator. In the heat exchangers, the seawater heats up by absor-
bing the condensation heat. The preheated water passes to
another heat exchanger operated by the cooling water from the
main engines. On leaving this heat exchanger, the seawater now
has a temperature of around 80°C. On the new ships being built
for Celebrity Cruises, the seawater then passes through 8 in-line
flash evaporators, where each level operates at lower pressure
than the previous one. From evaporator to evaporator, the sea-
water starts to boil at lower temperatures. In the last evapora-
tor, the pressure is so low that the water starts to boil at
temperatures of less than 40°C.
By using the heat emitted by the main engines together with the
internal heat recovery process involving brine and condensation
heat ,as well as connecting up 8 flash evaporators in line for the
very first time, the fresh water generators installed by MEYER
WERFT offer the greatest possible energy efficiency, making an
important contribution to environmental protection.
and
Generating fresh water by re-verse osmosis
The large number of passengers on board means that cruise li-
ners need huge quantities of drinking water. They are therefore
fitted with a reverse osmosis system in addition to the evapora-
tors. Reverse osmosis is based on membrane filtration. Mem-
branes are ultra-fine filters that filter out even viruses and salt
molecules. The seawater is pumped into the membrane module
by a high-pressure pump at 60 bar pressure. The elevated pres-
sure forces water molecules through the membrane. The water
is subsequently so pure that it is perfectly fit for use as fresh
water on board. Dissolved salts, organic components and mi-
croorganisms are too big to pass through the membranes. The
concentrated water is discharged over board.
However, this concentrate still contains large quantities of the
compression energy from the high-pressure pumps. Up to now,
this was put to no further use and simply allowed to escape into
the environment. By contrast, in the new ships being built for
Celebrity Cruises, a specially developed concept permits positive
utilisation of this energy. An impeller has been installed in the
concentrate outlet of the reverse osmosis plant; the impeller is
driven by the concentrate and is connected in turn to an impel-
ler in the inlet of the system. The energy remaining in the con-
centrate is thus transferred to the seawater at the inlet point so
that the required pumping output can be reduced. This concept
has lowered the energy needed in the system by around 65%.
