What effect can lime have on water quality?

Lime is commonly used in water treatment processes primarily for its ability to raise pH levels. When lime (calcium hydroxide) is added to water, it reacts with dissolved carbon dioxide to form calcium carbonate, which increases the water’s pH. This increase in pH can help in reducing the acidity of the water, making it more neutral or alkaline, which is beneficial for various water quality parameters.

In addition to raising pH, the addition of lime helps in reducing hardness in some contexts. Hardness in water is primarily due to the presence of calcium and magnesium ions. By precipitating these ions as calcium carbonate, lime can effectively remove some of the hardness from the water. This dual effect of raising pH and addressing hardness issues is a significant reason why lime is widely used in water treatment facilities.

The other options describe processes that either do not align with the known functions of lime or are outside the scope of its typical applications in water treatment. For instance, lime would not lower pH or increase hardness, nor is it primarily used for stabilizing turbidity levels or enhancing disinfection efficiency, which are related to different chemicals and processes within water treatment.