What it takes to keep water clean and usage lean on cruise ships

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Referring to a modern cruise ship as a “floating city” is no simple analogy. Not only does it provide accommodation, recreation, relaxation and transportation, it also literally has to support life in the most basic sense.

On the open saltwater seas, as Coleridge famously noted, while water is everywhere, there is not a drop to drink – unless potable water is collected in port or “made” using reliably tested methods.

Nick Rose, environmental regulatory lead, environmental stewardship, for Royal Caribbean Cruises Ltd., says the company’s fleet provides clean, safe, drinkable water in three ways.

“One is through bunkering it,” Rose says, using the maritime term for loading   water in port and storing it on board. “We follow strict WHO (World Health Organization) as well as U.S. Public Health standards, so water is taken from a reputable drinking source.”

While it’s collected, the water is tested for microbials and other pollutants, then treated and chlorinated for any potential organisms or pathogens that may have eluded onshore treatment.

The second method, used for years and for which all RCL ships are equipped, goes by any of three names – steam evaporation, flash evaporation or steam desalination. One clever “green” aspect of this method is its use of waste heat from the ship’s engines.

“We bring on seawater and boil it using the waste steam and heat from our engines to remove the salt from the water,” Rose explains. “The water from the evaporator travels down to a condenser where the steam then condenses back into what at that time would be distilled purified water.”

As anyone who’s ever tasted it knows, distilled water has no familiar water flavor. So next, minerals are added, “so that it has the normal taste that most people like,” Rose continues.

“After it goes to the mineralizer we send it for chlorination, just again to make sure that you have nothing growing in it.”

The third, most technologically advanced method of creating potable water is through reverse osmosis using equipment now on most RCL ships.

“You bring on seawater, but instead of using heat or high amounts of energy, you actually use a little bit of energy to push the saltwater through a semi-permeable membrane,” Rose says. “The only thing that makes it through the membrane is pure, clean water.”

All the salt and other possible contaminants remain blocked on the intake side of the membrane, while the water that passes through is mineralized for flavor and chlorinated for added safety.

Taking all onboard freshwater usage into account, RCL reports that on average its guests consume 55 gallons per day, compared to the U.S. average of as much as 100 gallons.

Contributing to the difference, Rose says, is the shipboard use of low-flow showerheads and washbasin faucet aerators in guest and crew cabins; highly efficient ice makers, dishwashers and laundry equipment; re-use of condensed water from air-conditioners to supplement laundry needs, and other above-and-beyond-compliance conservation efforts.