A large portion of data centers use open loop cooling. That is to say evaporative cooling. So they take fresh drinking water, make it hot, and dump it in the air.
It's a lot cheaper than closed loop cooling.
I’d like to see some evidence of that, adding evaporative cooling towers to a chilled water loop can almost double the COP. I don’t see datacenter operators foregoing much cheaper opex unless they’re in a water-critical area.
Particularly, newer data centers are much more likely to used closed loop systems. And, the bigger they are, the more likely they're on closed loop.