Which of the following is most likely used for dechlorination in water treatment processes?

Sodium thiosulfate is commonly used for dechlorination in water treatment processes because it reacts with chlorine to neutralize its disinfecting properties, thus making it safe for human consumption and the environment. When sodium thiosulfate is added to chlorinated water, it forms non-toxic products, effectively removing residual chlorine that can be harmful to aquatic life and detrimental to overall water quality.

The ability of sodium thiosulfate to rapidly neutralize chlorine is particularly beneficial in situations where the water is intended for sensitive uses, such as in drinking water treatment or aquaculture. It is preferred due to its effectiveness, ease of handling, and the fact that it does not introduce harmful byproducts into the water.

Alternate options may fulfill different roles within water treatment; for example, calcium carbonate is primarily used for pH adjustment, magnesium sulfate can be used to provide essential minerals, and chlorinated lime is a form of chlorine itself used for disinfection. However, none of these alternatives are suitable for dechlorination, which underscores the importance of sodium thiosulfate in this specific context.