You drink it then. It was editorialized correctly, the government is planning on dumping radioactive water into the ocean. Saying that the water is "treated" and thus not a problem is equally misleading.
Editorializing titles like that will cause you to lose submission privileges on HN. It's against the site guidelines: "Please use the original title, unless it is misleading or linkbait; don't editorialize." https://news.ycombinator.com/newsguidelines.html
Unlike on some other social news sites, submitting an article to HN confers no special rights over the submission and particularly no right to frame for others how they should interpret an article or a situation. Titles are the most powerful influence on threads—by far, actually—so this is a big deal.
If you want to say what you think is important about an article, that's fine, but do it by adding a comment to the thread. Then your view will be on a level playing field with everyone else's: https://hn.algolia.com/?dateRange=all&page=0&prefix=false&so...
If you felt that the article's original title was misleading, it's ok to change it, but you should do that by making it more neutral, not by replacing it with your own view. In this case your objection can easily be addressed by taking out the word "treated".