Massachusetts Wastewater Practice Exam

A reducing agent is primarily used to treat:

1. Sulfide.

2. Phenol.

3. Chromium.

4. Cyanide.

The correct answer is: Chromium.

The use of a reducing agent is most commonly associated with the treatment of chromium, particularly in the context of wastewater treatment. Chromium in its hexavalent form (Cr(VI)) is toxic and poses significant environmental hazards. Reducing agents convert hexavalent chromium to its trivalent form (Cr(III)), which is less harmful and can more easily precipitate out of solution, making it less likely to cause environmental damage and easier to handle during treatment processes. This conversion process involves adding a reducing agent, which donates electrons to the hexavalent chromium, thus changing its oxidation state. This is a crucial step in wastewater management, as it helps to mitigate the risks associated with chromium contamination. In comparison, sulfide, phenol, and cyanide can also be treated through various chemical processes, but the specific role of reducing agents is primarily focused on the reduction of chromium compounds due to their hazardous nature and the need for effective management in wastewater systems.