North Carolina Surface Water Practice Exam

Sodium thiosulfate is primarily utilized to neutralize chlorine residuals in water treatment processes. Chlorine is commonly used as a disinfectant in surface water treatment; however, excess chlorine can be harmful to the environment and aquatic life when water is discharged back into natural bodies. By adding sodium thiosulfate, it reacts with the chlorine, effectively converting it into harmless chloride ions. This neutralization is vital in ensuring that the water released meets safety standards and does not adversely affect living organisms in the receiving waters.