What two chemicals are used for de-chlorination?

The correct choice of chemicals for de-chlorination is Sulfur Dioxide and Sulfite Salts. These compounds effectively neutralize chlorine in wastewater treatment processes, ensuring that any residual chlorine is removed before the effluent is discharged into the environment or gets reused.

Sulfur Dioxide acts as a reducing agent that chemically reacts with chlorine, converting it to chloride ions, which are less harmful. Similarly, sulfite salts, such as sodium sulfite or calcium sulfite, can also react with and neutralize chlorine in a similar fashion. The use of these agents is crucial in preventing chlorine toxicity to aquatic life when the treated water is released into natural water bodies.

The other options do not serve as effective de-chlorination agents in wastewater treatment. For instance, chlorine and ammonia are often used in disinfection processes but not for de-chlorination. Hydrogen peroxide and calcium hypochlorite, while relevant in chlorine applications, do not serve the purpose of de-chlorination effectively. Lastly, formaldehyde and sodium nitrate are not typically used for this purpose in wastewater treatment practices. Understanding the role and effectiveness of these specific chemicals enhances the treatment process, ensuring compliance with environmental regulations.