Massachusetts Wastewater Practice Exam

What byproduct is generated when metal finishing wastes are treated with chlorine?

1. Hydrogen gas.

2. Chlorine gas.

3. Ozone.

4. Chlorinated organic compounds.

The correct answer is: Chlorinated organic compounds.

When metal finishing wastes are treated with chlorine, one of the significant byproducts produced is chlorinated organic compounds. This occurs because chlorine reacts with organic materials present in the metal finishing wastes. In metal finishing processes, organic contaminants often exist alongside the metallic components. When chlorine, which is a strong oxidizing agent, is introduced to this mixture, it can react with the organic compounds, leading to the formation of chlorinated organic compounds. These compounds can possess various environmental concerns due to their potential toxicity and persistence in the environment. The other byproducts listed, such as hydrogen gas, chlorine gas, and ozone, do not dominate the reactions that occur in this specific context of metal finishing waste treatment. Hydrogen gas would typically result from reducing conditions, while chlorine gas might be a part of the initial treatment process but is not the primary product. Ozone can be generated through other specific reactions, typically involving electrical discharges or UV radiation, rather than directly from chlorine treatment in metal finishing waste management. Thus, the generation of chlorinated organic compounds accurately reflects the chemical transformations that result from the treatment of metal finishing wastes with chlorine.