To precipitate silver out of fixer, just toss in some of aluminum foil. The aluminum will swap places with the silver which falls to the bottom of the container as a gray metallic sludge. After all the aluminum has disappeared (about 3 or 4 days), I siphon off the spent fixer and pour in another batch. I keep a one gallon wide mouth bottle just for this purpose; by now it probably has a couple of pounds of silver in the bottom.
No more heavy metal into the waste stream...