Hoo boy! an opportunity to mention Physician John Snow's amazing detective work in tracking down the cause of a cholera outbreak in London in 1854, (nicely told in the book "Ghost Map" by Stephen Johnson).

At that time, a commonly-held theory was that cholera was caused by "miasma" (bad air). John Snow however subscribed to the germ theory of disease, so his search centered on anything the cases might have had in common (not just air). This map, which he drew showed how the cases of cholera (black blocks) were centered around a single water pump (red dot that I added)and which helped to determine the cause of the disease (or at least that cholera is water-borne) and showed the importance of pure water.

So in 1854, a sizable portion of the population would have not considered pure water important in combatting cholera.

Check out this link: http://www.epa.gov/safewater/consumer/pdf/hist.pdf

To answer your questions: There is documented evidence that humans have been thinking about improving the taste and odour (i.e. aesthetic) of water from 4000 BCE (the Greeks and the Indians).

Initial methods of improving water quality included charcoal, exposing to sunlight, straining and boiling. Although these methods improved taste, and some cases killed bacteria, they did not stop all pathogens or viruses.

Two things to keep in mind:

• Many early societies settled down and developed around sources of water. Either near areas of high groundwater or springs, or areas with plentiful surface water such as rivers, lakes or snow melt. Availability of fresh, sustainable drinking water was one of the most important factors in early settlement.

• Before the industrial revolution, there weren't too many industries that were heavy polluters of drinking water sources. I can think of certain operations like tanneries or mines, but these would likely have been downstream of major population centres and limited in number. So man-made contamination wasn't as much of a problem as it is today. In fact, before 1800 it's possible that you could have just stopped at a stream and drank from it (especially if it was a cool groundwater fed stream) and had no problem. I wouldn't try this today though.

It wasn't until the 1700 and 1800's that scientists started focusing on the non-visible things in water, like bacteria.