If you aren't neurotic...
You could just drink most any water that is flowing and is far enough from some publicly provided water. It is, after all, being exposed to UV several hours per day. It has usually been filtered by soil.
You body has very sophisticated systems to keep you healthy. No, one bacterium probably won't be enough. Fill up when you can, but only if you must. Empty, and fill at the next one.
Sure, there are things that could infect you in some water supplies. What are the odds? If natural water were really dangerous, we wouldn't be here. You dog or cat drinks out of any puddle.
Alternatively, stay home. Watch TV. Die slowly.