Which of the following is a source of cyanide waste streams?

Cyanide is commonly used in various industrial processes, and one of the main sources of cyanide waste streams is electroplating. In electroplating, cyanide is used as part of the solution for plating metals like gold and silver onto surfaces. While effective for producing a high-quality finish, this process can lead to the generation of wastewater that contains cyanide.

When electroplating occurs, the leftover chemicals, including cyanide, can contaminate wastewater if not properly managed. This makes it crucial for facilities that engage in electroplating to implement appropriate waste treatment options to mitigate the environmental impact of cyanide discharge.

The other choices, while they may involve hazardous materials or pollutants, do not typically result in the production of cyanide waste streams in the same manner as electroplating does. This specific connection to the electroplating process makes it the primary source of cyanide waste among the listed options.