Fixer and Toners Are HHW
Used fixer and toners that contain heavy metals (like gold and selenium) should be disposed of as Household Hazardous Waste.
Developer, Stop and Hypo Clear
Unused and spent photographic developers and negative plate processing chemicals are generally not considered hazardous. They are safe to pour down the drain, but do so in small quantities in order to avoid chemical reactions.
Don't Dispose of in Septic System
It is never okay to dispose of photographic chemicals in the septic system. A septic system is an underground tank where waste is decomposed by anaerobic bacteria.