I vent my darkroom to the outdoors with an overhead fan (above developer/stop) that I got from Grainger. I have a dark vent (Premier darkroom louvers) in my door that takes air from another room. This I got from Freestyle. In general the air is pretty good and just the goings in and out gives me plenty of fresh air. I searched for a paper/developer combo that looks good without toning as I'm not sure toning is a cure-all for longevity. It certainly doesn't do my longevity any good. My prints will outlive me and that is good enough for now, but I'm not in the print sales biz.

Developers, stop (water), and everything else except the fix, goes in the gray water which just goes out on the ground. The exhausted fix I bring to work and send down the toilet. This is okay for my few gallons per year. If it were more, then I would add steel wool, remove the steel (steel/silver) wool, and then toss the fix that is left. It is pretty much just salt water at that point.

If you don't have a lot of liquid waste, you can evaporate the water from it and just toss the powder that is left.

Silver in low quantities is not on the EPA bad list, as I understand. Selenium may be a different story. Seems like it is a good thing in trace quantity and a bad thing in the San Juaquin Valley.