Which of the following is a common oxidizing chemical used in treatment processes?

Chlorine dioxide is a common oxidizing chemical used in various treatment processes primarily for disinfection and oxidation purposes in water treatment. This chemical effectively kills bacteria, viruses, and other pathogens, making it invaluable for ensuring safe drinking water. Additionally, it can oxidize certain pollutants and contaminants, such as iron and manganese, facilitating their removal from water sources.

In contrast, sodium bicarbonate, potassium nitrate, and calcium carbonate do not serve primarily as oxidizing agents. Sodium bicarbonate is typically used to adjust pH levels and acts as a buffering agent rather than an oxidizer. Potassium nitrate is more commonly recognized as a fertilizer and does not provide the necessary oxidation required for treatment processes. Calcium carbonate mainly acts as a pH buffer and is used to help prevent corrosion in water systems, but it is not involved in oxidation reactions. Thus, chlorine dioxide is distinct in its role as an effective oxidizing chemical in treatment processes.