TLDR; Water is slightly more radioactive than natural, every nuclear plant does this, its normal behavior, and safe since its such a low amount of radioactivity.
In practice, almost everything is radioactive to some degree. This is always handy to show people who don't get this: https://xkcd.com/radiation/
We have really good analytics. That water, based on the description of the article can be anywhere between “would be legal as tap water” to “kills anything on contact”.