LOL! My local supply is geologically old water, so it has been a long time, and it is processed before it gets to my house. Not a lot going on it biologically.
Since the water has seen daylight. Our local aquifer is geologically old, but not as old as some in upstate NY that I know of that predate humankind on this continent by a wide margin.
Have you only ever had the water from your local aquifer?
Have you never had any other liquid, eg milk, bottled water, beer, wine, cola, the list is endless. And even if another human didn't sit in it, how about dinosaurs?
I'm talking about the basic water molecules, I think it may be what you call RO.
Evaporation from the oceans, lakes, and from plant cover followed by condensation as rain falling on land was an excellent DI process prior to the industrial revolution, give or take a few massive volcanic eruptions and the occasional marcrometeor strike.
What's been a long time,and ..... 
do I really want to know? 