WSO Water Treatment Grade 2 Practice Test 2026 – Your All-in-One Resource for Exam Success!

The Langelier Saturation Index (LSI) is the correct choice for determining the calcium carbonate deposition property of water. This index helps evaluate whether water will deposit or dissolve calcium carbonate, which is particularly important in water treatment processes.

The LSI is calculated by comparing the actual pH of the water to its saturation pH (the pH at which calcium carbonate is neither dissolved nor precipitated). If the index is positive, it indicates that calcium carbonate will likely precipitate out of the water, leading to scaling. Conversely, a negative index suggests that the water is undersaturated with calcium carbonate, which can result in corrosion of pipes and other infrastructure.

Understanding the Langelier Saturation Index is crucial for water treatment operators, as it aids in preventing both scaling and corrosive conditions in water distribution systems. By maintaining a balanced LSI, operators can ensure the longevity of the system and the quality of water delivered to consumers.