NASA harnessed what nature already knew and designed an ionization system aboard their Apollo flights. An electronic silver-ion generator – slightly larger than a cigarette pack – was mounted on various locations in the spacecraft. These generators dispersed silver-ions to eliminate bacteria and viruses and provide the astronauts with safe drinking water. They did not want to bring chlorine with them into space.
Official NASA Final Report on Silver Ionization
(also includes Spinoff article below)