you are going to hear all sorts of opinions in this seemingly benign thread
as andy m said, your fixer and wash water have silver in them, and depending on where you live
it might or might not be allowed to dump your effluence / black+white processing tailings in your garden.
some will say its harmless ( as they always do ) some will even say your spent toners are harmless ( they always do )
and others will suggest none of it is ... the best thing to do is check with your local town / city hall to find out what is and isn't allowed, cause it will seep into your groundwater and could pose a potential problem down the road ..
IF you are permitted to pour de-silvered fixer and wash water ( if your municipality allows it )
there are ways to remove most if not all of the silver from your tailings.
you will have to determine what is or isn't permitted in your area, do a water test and figure it out from there ...
good luck !