I have finished my confidential report today on problems with a sewage treatment plant I visited earlier this week. It was very satisfying to be able to see a reliable way forward, even though the available data was rather uncertain.
One unusual feature of the plant was the presence of large numbers of Asellus aquaticus, (an aquatic relative of the woodlouse, pictured) in the aeration tank.
I have another effluent treatment plant to troubleshoot next week. It's nice to get a break from writing books to do some real engineering.