What type of chemical change occurs when sodium hypochlorite disinfects wastewater?

The process of sodium hypochlorite disinfecting wastewater is primarily characterized by oxidation. Sodium hypochlorite, commonly known as bleach, functions as a strong oxidizing agent. When it is added to wastewater, it facilitates the oxidation of various contaminants, including bacteria and organic matter, rendering them less harmful or non-viable.

Oxidation involves the loss of electrons or an increase in oxidation state by the molecules being reacted. In the case of sodium hypochlorite, it oxidizes the cellular components of microorganisms, thereby disrupting their functions and effectively killing them. This is crucial in wastewater treatment, as it helps in ensuring that the effluent discharged is free from pathogens, thus protecting public health and the environment.

Other processes listed—such as reduction, neutralization, and hydrolysis—do not accurately describe the primary action of sodium hypochlorite in this context. Reduction refers to the gain of electrons, neutralization involves reactions between acids and bases to form water and salts, and hydrolysis pertains to the reaction of water with another compound, leading to the breakdown of that compound. These processes do not encapsulate the mechanism by which sodium hypochlorite acts on contaminants in wastewater.