Today's question: How is drinking water on cruise ships treated?
"Plain Talk" answer: Cruise ships used to bring water from shore, but with the biggest ships using more than 250,000 gallons (947,000 liters) of fresh water a day, this is impractical. Most of these liners have on-board desalination units, either employing reverse osmosis or flash evaporators that boil seawater and recondense the steam vapor, to produce purified water from the ocean water. This water then goes through a remineralization process to add back minerals that give the water a fresh flavor, followed by disinfection to kill any microbial contaminants.
The wastewater also goes through an extensive treatment process before being discharged.
For more information on this and many other water-related topics, check out "Plain Talk About Drinking Water" by Dr. James M. Symons.