A tale of two waters, which exemplifies the differences in the differences needed in water treatment depending on climate and raw water source:
Water 1: 21 years ago, I was living just outside of Washington DC (in Silver Spring, MD, the original home of Pace Worldwide) and I decided to make a pitcher of Kool-Aid. So I mixed it up, took a sip, and dumped it all down the drain — the chlorine taste was unbearable. It literally tasted as though it'd been made with pool water. (I had forgotten that the chlorine would have dissipated had I left it uncovered overnight.) DC is basically built on former swamp land, so in the summer, I guess the raw water is not of optimal quality.
Water 2: Here in Zurich, about 70% of the city water is pumped from the lake, while the remainder is a half spring water piped in from a nearby mountain range and half well water from within the city. Since Switzerland is at the top of Europe, altitude-wise, the water here is largely "virgin", needing relatively little treatment. (Amusingly, they use pools of live fish as "canaries" for early detection of water quality issues.) And I must say, the water here is
excellent — it tastes great, and even in the summer it comes out of the tap fairly cold. But Zurich actually has a backup water system, too, in case the main system becomes inoperable because of power failure or contamination of the lake! Remember the mountain spring water pipeline I mentioned before? It's purely gravity-fed and requires no filtration beyond a sand filter, ensuring a backup supply even without power. A separate network of 150km of pipes sends this water directly to critical consumers like hospitals, but also to over 400 fountains throughout the city, about 85 of which are special emergency fountains with hidden internal hydrants, guaranteeing 15 liters per person per day. During normal operation, they operate as normal water fountains that literally spout spring water for free. (If you're ever in ZH and see a
drinking fountain that looks like a bronze R2D2, those are the emergency fountains.)