Which waste category is commonly associated with cyanide as a contaminant along with heavy metals?

• A. Cannery
• B. Oil Refinery
• C. Metal Plating
• D. Pulp and Paper

Answer: (C)

Cyanide shows up in waste when processes use cyanide chemistry to separate or plate metals, creating waste streams that contain both cyanide and heavy metals. In metal finishing and electroplating, cyanide salts form stable metal complexes that allow smooth deposition of metals such as nickel, copper, or gold. When these plating baths or rinse waters are discharged, they carry cyanide along with dissolved metals, making this waste category the one commonly associated with cyanide contamination plus heavy metals. The other industries listed don’t rely on cyanide-based plating chemistry in their typical operations, so their wastes aren’t characteristically characterized by cyanide teamed with heavy metals in the same way.