a quick way to get 90% of it is to do a quick dunk in 1 tray that you keep using until you virtually can't see the paper for the dichromate. Keep it, and HHW recylce it (dehyate works, as does re-using spare 2l soda bottles, appropriately labeled.) The second etc baths should be so dilute in dichromate, just put it down the drain.

The advise might vary a bit if you are on septic; you may need to look at a polymer resin filter. I have one for silver that is commecially made; I'm not sure if there is one for dichromates.

Another idea is to dump the wash water effluent though an iron wool packed cylinder. It should turn the iron bits from ferric to ferrous, and in turn go from dichromate to bichromate, a less toxic form. I am winging it from memory here at work; all my references are at home. Others are more than welcome to chime in an say if this idea is full of holes.