As someone who does industrial controls wastewater treatment is one of the worst industries because it's so low-margin. It's a 'barely pay for it the first time

As someone who does industrial controls wastewater treatment is one of the worst industries because it's so low-margin. It's a 'barely pay for it the first time and run it until it breaks down' type of industry because municipalities and rate payers are usually quite cost sensitive, but pedantry aside your point is largely accurate. As a side note - In my experience the best paid but most mind-meltingly dangerous industrial controls work is in oil refining. The most low-stress (and somewhat less well paid) work i've experienced is in designing control systems for hydroelectric facilities for private utilities. I wouldn't consider either glamorous but the hydro work does have a more environmentally friendly image and does have a correlating lower pay!