Alabama Grade II Water Operator Practice Test 2025 – Comprehensive Exam Prep

Alum, or aluminum sulfate, is widely recognized as a common coagulant used in water treatment processes because of its efficiency in removing suspended particles and impurities from water. When alum is added to water, it hydrolyzes to form aluminum hydroxide, which is a gelatinous precipitate. This precipitate helps to agglomerate (or clump together) smaller particles and suspended solids. Once these particles aggregate, they become larger and heavier, making it easier for them to settle at the bottom during sedimentation or to be removed through filtration.

The effectiveness of alum stems from its ability to adjust the pH of the water, enhance the coagulation process, and improve the overall quality of the treated water. Its application is crucial in producing safe drinking water, especially in municipal water treatment systems.

In contrast, the other substances listed do not serve the same primary function in water treatment. Chalk, primarily calcium carbonate, acts as a hardness agent and helps in adjusting pH but is not a coagulant. Salt is mainly used for softening water or in water conditioning, and magnesium hydroxide, while it can be used to adjust pH, is not typically employed as a coagulant in standard water treatment processes. Hence, alum stands