Which chemical is used to stabilize water after it has been lime softened?

The process of lime softening water often results in the removal of hardness minerals, but this process can also lead to an imbalance in the water's pH and alkalinity. After lime softening, the water tends to be too alkaline, which can lead to scaling issues and other water quality problems.

Carbon dioxide is used to stabilize water after lime softening because it can lower the pH of the water. By introducing carbon dioxide, the water becomes more neutral, which helps in preventing the precipitation of calcium carbonate that could result from overly high alkalinity. This stabilization is crucial for maintaining water quality and ensuring that it is safe and suitable for distribution and consumption.

In contrast, sodium chloride does not play a role in stabilization in this context but is more commonly associated with other water treatment processes, such as water softening through ion exchange. Calcium sulfate and magnesium hydroxide also do not effectively address the pH issues following lime softening. Therefore, using carbon dioxide is the appropriate choice for stabilizing water in this scenario.