While attending the Bruce Barnbaum workshop he told us a bit about dumping chemicals. He had a seperate holding tank built underground for his darkroom chemicals. They were expoeriencing a drought one year and by mistake he watered his lawn with the spent chemicals. His lawn grew very well and was lusher than it had ever been. He thought it was a fluke so he tried it again. Well long story short, he found that the spendt chemicals made a wonderful fertilizer. His was also well mixed with the wash water from the prints and toher things. I now dump the spent chemicals I have out the back onto a section of our lawn. I have to take a weed whacker to it to keep ti semi proportional to the rest of the lawn.
As for the silver, I would get one of the recovery kits. Rio Grande in Albuerquere and Houser and Miller in Missouri both will take the filters and send you money based on the silver market.Be warned though, silver hovers well under $10 an oz. on the spot market. But it may buy you another roll of film for your troubles