Texas Commission on Environmental Quality (TCEQ). Class C Water License Exam

What is the impact of using alum in water treatment?

1. Increases pH levels

2. Helps in sedimentation

3. Reduces water hardness

4. Neutralizes chlorine

The correct answer is: Helps in sedimentation

Using alum in water treatment primarily aids in sedimentation. Alum, or aluminum sulfate, acts as a coagulant that helps aggregate small particles and impurities in the water, forming larger flocs, which then settle out more easily. This process is essential for clarifying water, as it effectively removes suspended solids, organic materials, and microorganisms, improving the overall quality of the treated water. Other options do not accurately reflect the primary effects of alum. While alum can have some minor impacts on pH due to its acidic nature, it does not effectively increase pH levels – this role is better suited to substances like lime. Though alum might interact with calcium and magnesium in some contexts, it is not primarily used to reduce water hardness; specific treatments target hard water more effectively through ion exchange or reverse osmosis. Lastly, the neutralization of chlorine is unrelated to alum's function in water treatment, as alum does not neutralize chlorine but instead is used in coagulation processes. Thus, the key benefit of alum is its role in enhancing sedimentation during water treatment.