As others have said, except for metal based toners, photo chemicals are biodegradeable. As Thomas points out, they do place a chemical oxygen demand on the waste treatment system. In the US, most waste treatment plants do continuous aeration of the waste to deal with this for ALL the stuff in the waste stream. But to help, pre- oxidizing is a good idea. For developer, just leave it in a pan for a day at the most.(posted 8604 days ago)The silver is fixer is not in a biologically active state, but silver recovery is a good idea. Porter's (www.porters.com) sells the silver recovery setup Ed talks about. The neat thing is when you fill it up, you ship it back to the manufacturer and they pay you for the silver.
There is a good site called TerraGreen (www.terragreencom) that talks about this, and since it is not a manufacturer of photo chemistry, the concerns Thomas has about the sourse are moot. BTW he is no longer in business, so don't try to order any of his products.