Depends on the amount of treatment steps it undergoes.

Standard procedure is aimed at just removing solid debris and organic matter, to return clarified and chemically balanced water to nature, with no excess nutrients that could feed algae in water streams.

From that point forward, it is just a question of how far the treatment can be taken.

For reuse for cleaning, washing, etc? Maybe it just gets a minute dosage of sodium hypocloride.

Highly sensible areas, like beaches or lakes? UV treatment, maybe followed by micro filtering. Extreme scenarios? Reverse osmosis.

If the protocols in place are strong, it's safe.

I always assumed the same... Turns out, a wastewater plant and treatment plant for drinking water look a lot more alike than I thought.

I'm pretty sure you could drink it, you'd just want to do it far enough away that you don't have to think about where it came from.

Which means a leak would be "relatively clean" water getting all over the place.

Just doesn't sound like a good idea.

Also, are we talking using this water in chiller cooling towers, like most buildings use? So essentially heating that "relatively clean" liquid to about 100° or so (you know, a temp that microbes just love), and releasing it to the atmosphere.