Interesting. So, you’re wondering. How far is it between a typical city and the sewage treatment plant (Publicly Owned Treatment Works (POTW))? Well, this article does cover some metrics for one city, Raleigh, North Carolina. Basically, a typical sewage treatment plant is huge. It may be in the middle of a giant farming district, serving the combined output of many cities.
20181014/DuckDuckGo distance between city and sewage treatment plant
20181014/https://www.scientificamerican.com/article/treating-sewage/