> ...For cities which draw
> >from lakes and river systems, there are few alternatives.
>
> i think the alternatives would probably come about far easier if the
> city upstream would treat its water properly.
It's not just cities, of course. Large river systems are unreliable water supplies at best for a multitude of reasons, and urbanization is only one of them. Upstream agriculture and runoff. Just-plain-old-unsuitability - a river is, in essence and purpose, a great big concentrator. If it flows out of a swamp, it carries the swamp. If it flows a great distance, it carries a great many things with it. I doubt that the good citizens of the hypothetical city would enjoy the great many things that can flow through even quite pristine river water.
> ...- most
> >urban sewage is human waste.
>
> some things to consider...
> a significant number of cities have "combined sewer systems"
> which treat stormwater and sanitary sewage together during rain
> events. stormwater usually has the really nasty stuff in it. heavy
That's true, and that's usually because of the overflow system's design; rather than having storm sewers (which contain, as you say, heavy metals (from paint), gas and oil (from motorists), dioxins (all sorts of things), rats, rubbers, and needles) overflow onto streets and into houses, they allow it to flow through without appropriate treatment.
Any process, whether natural or not, has a limit to how much it can handle. Whether it's an artificial wetlands (the technology I believe you're talking about - there are more than 800 in the united states alone, so it's hardly suppressed technology) or a sewage treatment plant.
I'm not sure exactly what I'm arguing for or against: I think that sewage and especially water treatment should be taken much more seriously in the great scheme of things. I think you do too.
marco
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> Marco Anglesio | One of me stayed on the ground, <
> mpa at the-wire.com | without provisions or hope or <
> http://www.the-wire.com/~mpa | sight or legs, and refused to leave. <
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