Quote Originally Posted by Monito View Post
Do not dispose used fixer down the drain. It will kill necessary bacteria at the sewage plant and will deposit toxic heavy metal ions in the environment. Recover the silver or dispose of at a hazardous waste facility.
It is a good idea to recover silver, but used fixer doesn't contain enough silver to cause damage unless you produce relatively huge quantities.

If you are looking for a way to recover silver, check with jnanian here on APUG - he sells a unit that can do this for you.