Dubai’s Costly Water World | The city has spent billions of dollars to provide fresh water to its residents and tourist attractions, but experts say the efforts are straining the Persian Gulf

When all you've got it money and desert, that's where you build

But to maintain its opulence, the city relies on fresh water it doesn’t have. So it turns to the sea, using energy-intensive desalination technologies to help hydrate a rapidly growing metropolis.

All of this comes at a cost. Experts say Dubai’s reliance on desalination is damaging the Persian Gulf, producing a brackish waste known as brine which, along with chemicals used during desalination processing, increases salinity in the Gulf. It also raises coastal water temperatures and harms biodiversity, fisheries and coastal communities.

I was wondering too

Yes, with several common processes

I was curious too. The article mentions that Dubai’s old reverse osmosis systems rely on flash distillation which adds a lot of heat to the system and thus the brine being returned to the gulf waters.

“Unlike reverse osmosis, which removes salt and other contaminants by pushing water through a semipermeable membrane, multistage flash distillation relies on heat. Decades ago, when the U.A.E. began exploring desalination, the technology could better handle the Gulf’s high salinity, though reverse osmosis can now do the same. And although both technologies create brine, the byproduct of multistage flash distillation is far hotter, further disrupting the ecosystem.“

closed system, the less water there is to disperse heat energy it gains from sunlight/underwater vents, the more heat energy the water retains. it's basic mathematics.