I found an article on the Nordbergs here. Boston's Deer Island Treatment plant is mentioned about half way down the page. It says there were 9 engines. I had sort of forgotten about the two that were being used for parts, at that point (the 1980's). The photo is of #7. They were ultimately replaced with 1000 horsepower electric motors. They ran mostly on shore power, but there were supposed to be two big Enterprise V-12 (IIRC) engines powering generators for emergency power, but the Enterprises were never reliable, ostensibly because the pads they were installed on were not level. The plant is gone today, and I'm not sure where the sewage goes. (FIL has passed on too.)

bigone.jpg