Water treated with UV radiation will not help you become a superhero. I’ve tried it, it didn’t work! I suppose it will change your water a little bit though, but not in a bad way. Anything that’s living in your water supply, whether it be little bacteria or organic matter, will be changed. Organisms will have their ability to reproduce put on stop and organic matter will have assistance in breaking down (like bacteria, some organic matter will more, and some less reactive to UV) this could actually make your water taste and smell better.
Mineral content will be unchanged, UV has no effect on the actual make-up of your water, nothing is added and nothing is removed. This also means that if you have bits in your water then UV alone will not get rid of them, a UV unit is not a filter.
UV being a physical treatment process (as opposed to a chemical one, like Chlorine) means that it’s impossible to overdose on UV. You can never kill too much bacteria and once the water is out of the reactor there is no after-effect from it (also one of the negatives of UV).
In summary, if you pass water through a UV unit, you will be left with pretty much the same water minus any bacteria that might have been in it. Will you notice a change in the water? I would guess not, but that’s not really the point is it?