Photography and darkroom
The regulated container is the one for the waste
Updated
Spent fixer carries dissolved silver, and silver is a toxicity characteristic contaminant at 5.0 mg/L. Because fixer has almost no filterable solids the waste itself is the extract, so you compare the liquid directly. And the determination is made at the point of generation, before any dilution.
The waste
Silver, 5.0 mg/L, and the dilution clause.
What goes wrong
Named failures, with the cause for each.
Containers
191 containers, and 132 under 500 mL.
Written from 40 CFR 261.24 and 262.11. Every page names its source.