Colloidal silver has been shown to be an effective anti bacterial and anti viral solution. It's healing properties on wounds, especially burns, is renouned.

There was good reason in times gone by (when coins contained real silver, gold and copper) that they were placed in water supplies. Copper kills algae. Silver kills bacteria and viruses, and gold maintains the bond angle of water. Unfortunately in modern times all we remember is to make a wish when we throw a coin in a body of water.