What is a limitation of the lime softening process?

The lime softening process is primarily used to reduce water hardness by precipitating calcium and magnesium ions, which are responsible for hardness. However, a limitation of this process is that it cannot remove all types of hardness effectively.

Lime softening specifically targets carbonate hardness but may be less effective in addressing non-carbonate or some forms of dissolved hardness, especially at lower pH levels or in the presence of certain water chemistry conditions, such as high levels of non-carbonate calcium. This means that while it can significantly reduce hardness in water, it doesn't guarantee complete hardness removal, which is a crucial consideration for water treatment facilities aiming for specific water quality standards.

In contrast, other choices highlight characteristics that either don’t accurately represent the lime softening process or are inherent benefits not related to limitations. For instance, removing color or being inexpensive are not universally true characteristics of lime softening, as certain waters may not experience significant color removal through this method, and the associated costs can vary depending on the context. Additionally, while sludge handling is part of many treatment processes, lime softening does generate sludge, requiring proper management, countering the claim that it requires no sludge handling.