In the case of one amazon data center the town already had nitrates in their water due to agricultural runoff, but at levels that weren't a problem. Amazon took in hundreds of millions of gallons of that water for cooling, which evaporated away some of the water, but left the nitrates. Then amazon dumped the concentrated nitrate 'waste water' at such high volumes that it was pushed so deep into ground that it reached the aquifer contaminating the source for some 45k people. Soon people's taps were delivering water contaminated at 10x the legal limit. People got sick. A bunch of parents lost their babies.

Amazon was forced to settle for 20 million which will pay for digging to find uncontaminated water sources deeper in the ground. They'll also pay for water treatments to help remove the excess nitrates.

Data centers don't have to bring in new toxins and pollutants. They can also make existing problems much much worse.