The classic location for a clean-water plant is outside town at the end of a road (maybe gravel), or hidden in some old industrial district. In part that always made sense. Economics dictate that to the extent possible, wastewater should flow by gravity. So the ultimate collection point is in a low spot, often right down near the river or the creek.
And probably not by accident, in a low spot well out of sight of downtown. Again necessity played a role: Look back 40 or 50 years and treatment plants had their issues
