Florida Drinking Water Operator "B" Practice Test

Why is soda-ash used in the softening process?

1. To improve taste

2. To reduce pH

3. To remove non-carbonate hardness

4. To add minerals

The correct answer is: To remove non-carbonate hardness

Soda-ash, or sodium carbonate, is primarily used in water softening processes to remove non-carbonate hardness, which is mainly due to the presence of calcium and magnesium ions that are soluble in water. These ions can cause hardness in drinking water, leading to scaling and other issues in plumbing and appliances. When soda-ash is added, it reacts with the calcium and magnesium ions, forming precipitates that can be removed from the water. This action effectively softens the water by eliminating these hardness-causing minerals. This process is particularly beneficial because non-carbonate hardness is generally more difficult to treat with methods that only address carbonate hardness. The other options do not accurately describe the role of soda-ash in this context. While soda-ash can have an effect on taste, that is not its primary purpose in softening. Additionally, its use does not primarily aim to reduce pH; in fact, soda-ash can raise pH in some situations. Finally, soda-ash does not serve to add beneficial minerals, as it is focused on the removal of hardness-causing compounds rather than enhancing mineral content.