The Mississippi river is actually a fascinating object of study. It has no more claim to the romance of southern rafting. It is a filthy, dangerous, industrial river. According to one professor, somebody dies ever year trying to swim across it. The waters are fast and turbulent, and the whole thing is huge. It's basically a continuous lake.
Anyway, where it passes through St.Louis, it has picked up the wastewater from seven major American cities, including Denver, Colorado and Chicago, Illinois, which apparently sends a lot of wastewater our way. And we drink it. Or at least, we filter it first and then drink it.
It's surprising that I've not been able to find one source for the inflow and outflow of water in St.Louis, so, to the best of my research: The City of St.Louis has two draw points- one in far north St.Louis on the Mississippi, and one across the county line, which draws water from the Missouri river. Interestingly enough, upriver from that draw point is what appears to be a County draw point, and then a county waste treatment plant which dumps into the river, a scant five miles before it's sucked up by the city draw.
My design thinking project (at this point anyway) has a lot to do with water flow, so the site of the project I wanted to be close to major treated wastewater outfalls. I went to two of them today. As far as I can tell, all the waste in St.Louis city is fed to a plant north of the downtown, treated and dumped in the Mississippi. I climbed down the embankment and found the outfall pipe, which goes into the river and dumps underwater. Standing on the shore, I was hypnotized by the plumes of blatantly different water color reach the surface. It was a lot more red, like a maroonish chocolate color.
Beautiful day to go waste treatment plant hopping too. Sunny, breezy, warm. I also drove way down to the confluence of the Des Peres river and the Mississippi, because there's a major county water treatment plant that dumps right into the Des Peres just before the confluence. The water level was so low, I can only assume that the majority of the water flowing in the Des Peres was from the treatment plant. It was an adventure and some luck that I found the spot overlooking the confluence.
You have to drive and park at the River City Casino, best near the northwest corner of the parking lots. There's a perimeter trail inside the fence which runs around the property, and at the farthest northwest corner, there's an opening, where there is a well-worn trail. If you follow it, it takes you to an overlook over the reinforced confluence, and from there you could walk down to the shoreline.
Images from the Mississippi river outfall: