Cholera, dysentery, and many other waterborne diseases exist naturally in untreated water that hasn't been "meddled with" by humans.

The death tolls of historical urban outbreaks shows that you would MUCH rather drink the treated water.

Maybe you should just read the article I linked. If you have more questions, then you can google those and figure it out.

If through your process of learning, you come up with an understanding of any situation, then you should form an opinion.

I don't mean to be rude but your question is easily answerable by reading the article I linked (and it's a short one). If you're not going to take the 30 seconds to respect my comment, I will show none to your uninformed opinion.

They are part of the water treatment process for municipal drinking water supplies.

Though I'm not familiar with the specifics and details of this case (and have seen the Veritasium video describing the use), it's reasonable to assume that these treatments would be applied regardless, and the shade balls are an effective countermeasure.

I'm not clear why it matters. Everything natural isn't necessarily good.

Salts are everywhere, there's nothing wrong with trace amounts in water.

It's used in the water cleaning process to make it drinkable.