Massachusetts Wastewater Practice Exam

Toxic chemicals are added to the metal waste stream in which of the following processes?

1. Etching

2. Cleaning

3. Plating

4. All of the above

The correct answer is: All of the above

Toxic chemicals can be introduced into the metal waste stream through various processes that involve the treatment or manipulation of metals. In the etching process, chemicals are used to remove specific areas of metal, which often includes harmful substances that become part of the waste. During cleaning processes, toxic chemicals are typically employed to remove contaminants, oils, or other residues from metal surfaces before further treatment or processing, contributing to the metal waste stream as well. The plating process also involves the use of toxic substances as metals are deposited onto surfaces through chemical reactions. Each of these methods—etching, cleaning, and plating—utilizes chemicals that can be toxic, reinforcing the idea that all these processes introduce toxic materials into the metal waste stream. Therefore, it is accurate to conclude that toxic chemicals are added in all of these processes.