My grandad had a couple of wooden water buckets when I was a small kid. There was about fifty cents in silver coins in each bucket. We never dumped the coins out because they were used to stop bacteria from growing in the bottom of the pails. I don’t know how it worked but it did.
It does work. It’s the silver. In fact I have read that some preppers have a stock of colloidal silver as well as another type, which I can’t remember right now.
It’s will kill bacteria, and can serve as a sort of anitbiotic. You have to be careful with dosages.