Sodium thiosulfate is primarily used to do what?

Sodium thiosulfate is primarily used to neutralize chlorine residuals in water treatment processes. When chlorine is added to water for disinfection purposes, it can leave a residual that, if present in high concentrations, may pose a risk to aquatic life or interfere with other processes. Sodium thiosulfate acts as a reducing agent, effectively neutralizing leftover chlorine and converting it into harmless chloride. This is especially important in cases where water is being discharged into natural water bodies or when preparing water for processes that could be affected by chlorine, ensuring that it meets safety and environmental standards.

In contrast, adding chlorine to water is not a function of sodium thiosulfate; rather, it is typically done using chlorine gas or other chlorine compounds. Increasing pH levels in water usually requires the addition of substances like lime or soda ash, which are more effective than sodium thiosulfate for such purposes. As for controlling algae growth, chemical treatments often involve algaecides or nutrients management strategies rather than sodium thiosulfate, which is not specific to algal control.