Aerating water is the process of adding more oxygen to water. It is necessary when water is anoxic, usually due to water contamination like sewage dumping. In the Chicago river, anoxia is likely due to pollution and runoff. When there is not enough oxygen in a body of water, fish and helpful bacteria die off. It is necessary to aerate the water from time to time to keep the balance of living organisms in the river.
If you look closely at the surface of the water during the aeration process, you'll see it fizzing like seltzer!
I run across the Webster bridge fairly often and am familiar with the usual fizzing there. However, last Sunday I stopped in disbelief because that entire area was filled with soap suds. I could smell the perfume from detergent. When a good gust of wind would come up, a section of suds would blow thru the air & land back in the water. Heaven knows what else is going into that river. I can't believe people kayak in that water all summer. Ick.
I'm pretty sure it has something to do with the extremely low flow of the current, which resulted way back when they reversed the river to flow into the Mississippi. There's practically no detectable current there, so the added oxygen helps keep the water from stagnating any more than it already is. It's had that soapy smell for as long as I can remember.
The Chicago River is hardly Perrier. I really have a hard time figuring out how people wanting clean water and being responsible humans to the planet in order to maintain the earth for habitation is a liberal elite thing. It is like saying keeping your house clean so you don't get roaches and rats, and buying the cleaning supplies in order to do so, is just another example of liberal elite spending. You would think being conservative with how we use natural resources would be something republicans and democrats could agree on. Every tax dollar spent is not an inherent evil in the universe. It is called civilization.
Perhaps cleanup of the Chicago River is moving pollution north from "Bubbly Creek" in Bridgeport to Lincoln Park. The stuff has to go somewhere. I personally am not responsible for the slaughter of animals at the Stock Yards in the early 20th century, nor are our elected officials.
Well, we or our current elected officials may not have caused it, but we are responsible for doing something about it. Dead politicians from 100 years ago sure can't take accountability or do anything about it now.