ok, so we've done some work on lift stations in the past and so we have to go out and meet with the sewer treatment guys on site on occasion. they've actually said that the crew that does what you're talking about will fight over who gets to go down "in the hole" because they get to keep what they find. meaning, diamond rings, old coins, watches, all kinds of stuff. so as they are sucking the stuff up with the vacuum hose they watch for the treasure. and if they don't get it, the guy watching the truck up top gets first dibs. sounds crazy and disgusting, but they said they have gotten thousands of dollars worth of jewelry at a time, and when it's cleaned up the pawn shop doesn't care. they are a very different group of guys, and as you say there is absolutely zero things they are grossed out by.