According to a story in yesterday's Chicago Tribune, chinook salmon are running again in the outflow of the East Chicago, Indiana wastewater treatment plant.
The salmon have used the outflow of the sewage plant as a spawning grounds since the plant switched from chlorinating the discharged water to a UV light disinfection process. In the 19 years since then the discharge channel to the Little Calumet river has made a dramatic turnaround as wildlife return to its banks. Native fish and microorganisms now live in the water, and even freshwater sponges!