Why is sodium thiosulfate added to total coliform bottles?

Sodium thiosulfate is added to total coliform bottles primarily to dechlorinate the sample. Chlorine is a common disinfectant used in municipal water treatment processes, and it can significantly inhibit the growth of bacteria, including total coliforms, if present in the sample. By adding sodium thiosulfate, any residual chlorine in the water sample is neutralized, allowing for a more accurate assessment of bacterial presence. This ensures that the testing reflects the true levels of coliforms and does not yield false negatives due to chlorine's bactericidal effects.

The other options relate to processes or effects that do not accurately describe the function of sodium thiosulfate in this context, as it does not enhance bacterial growth, dehydrate the sample, or preserve sample temperature. Understanding the role of sodium thiosulfate is essential for accurate microbiological analysis in drinking water testing.