I've had a TM for 5 years, in July. When I worked for "That Other Company", they had us dump wherever. I've consulted with a local environmental engineer a couple of times since I started this thing, and he says that most of the popular cleaning agents we use are fine to dump, given the dilution ratios we're dealing with. However, should you boost with a d-limonene and naptha mixture, like Citru-Solv or Citrus Force, probably best NOT to dump willy-nilly.
I've got an APO on my machine. The only times I DON'T run into a toilet or sink drain in the place I'm cleaning is when I've had a float switch on the tank go out, or something, and the APO stops functioning.
I feel that we have a responsibility to the environment that we live in, and those who come after us. It's like a campsite...leave it like you found it, if not better.