Municipal Waste water charges adjusted for yearly inflation

Obviously, the cost for treating water is increasing, and I was wondering if that was due partly to the new methods that have been developed since this collection of these data began. Regardless, it goes to show just how valuable clean water as a resource will become. I read somewhere that, as difficult as it is to believe now, water will someday become more expensive than oil. That's pretty frightening, especially since we as a country are a bit pressed for money right now, but this is something we can't avoid paying.

I wonder if the cost increase is purely economic or if it is relative to the water quality. Is it possible that municipal water is being more and more thoroughly purified as the price increases each year?

I wonder how small a part of the increase is due to increase of population in this area. Which area is that by the way?