While I don't condone dumping just anything down the drain, dumping small amounts of used fixer may sometimes be the best solution.
Originally Posted by jnanian
Ideally, of course, performing silver recovery before dumping fixing into the municipal sewer is a good idea. For some of us, that is no longer practical.
I used to take my used fixer to a local photo finisher for silver recovery. They were happy to get it (they made money from the recovered silver) and took it off my hands for free. They have longs since gone out of business. There are no longer any photo finishers around to take my fixer.
Another alternative is to take the fixer to the local hazmat facility. I tried that a couple of times. The goons working at the facility had no idea what I was trying to give them, seemed to be unfamiliar with silver recovery and handled the used fixer like it was toxic waste from Fukushima. The used fix just got labeled "photo chemicals" and I'm reasonably sure that it never got to any kind of silver recovery unit. So much for the hazmat people.
That leaves do-it-yourself silver recovery, which is a great idea and something I will initiate as soon as I have my own, and not a rental, darkroom. In my present situation, I will simply dump the five to ten gallons a year of used fixer down the drain. A less-than-ideal but still fairly responsible solution.
FWIW, Kodak in the tech pub J-300 states:
"Although the form of silver (silver thiosulfate) found in photographic processing effluent is not harmful and is removed during secondary treatment at the POTW, it is a good practice to recover silver before discharging the effluent."
I interpret this as "recover if you can, but go ahead and dump if you must." Especially for low-volume users, a few gallons a year of used fixer down the drain is not an environmental concern.