I read a short story (non-Star Trek) some years ago about a ship that had a floor that absorbed and recycled any contaminant that came in contact with it - skin cells, dirt, hair... or human waste. One of the bridge crew was from a planet with absolutely no concept of privacy concerning biological functions. When he decided to urinate or defecate, he just pulled down his pants and did so, on the floor, in front of everybody.
It ended up causing some visiting aliens a great deal of offense, and an interstellar incident ensued...
Well, there is that line in early TNG (up the long ladder) about the 'ship cleaning itself'. I never thought of it in quite this way, though
