One of the confusing aspects of water purification is the misconception that activated charcoal filters remove bacteria - they do not. They're very effective in the absorption of chemical contaminants, particularly those that are carbon based. And, because of activated charcoal's massive, molecular surface area, it does an outstanding job of scrubbing organics. The bottom line is, while that activated charcoal filter does a fabulous job of making your water taste bland, in reality, it cannot remove bacteria. That's the reason most municipal water treatment facilities continue to use chlorine as the chemical of choice for bacterial elimination.
Now, if you think that your municipal water supply is pristine, fill a sterile jar with tap water, cap it off, then sit it outside in the sun for a week. In most instances, by the end of the week you'll see algae growing on the inside of the jar. The water is clean enough to drink - but it's far from being sterile.
Most bottled water is heavily filtered, and in some instances, as stated earlier, it's nothing more than tap water with a fancy name on the bottle. As for the Brits filling barrels with water for the ships, well, yes they sometimes did that, but that water was brewed into beer so it could be safely stored and used for months on end when there was no source of clean, fresh water available. Water stored in those casks was only good for a couple days at best, and this was when the water was drawn from pristine sources. In fact, the only reason this world exists is because of BEER! How Beer Saved the World | Watch Free Documentary Online
There's a good reason that I keep the boat's bar fully stocked.