What is a common coagulant used in water treatment?

Alum, or aluminum sulfate, is widely recognized as a common coagulant used in water treatment processes. Coagulation is an essential step in the water treatment process aimed at removing suspended solids from water. Alum works effectively by destabilizing the particles in the water, which allows them to clump together into larger aggregates called flocs. This aggregation helps in removing contaminants through subsequent sedimentation and filtration processes.

The effectiveness of alum is due to its ability to lower the electric charge on particles that are typically repelled from one another. When alum is added to water, it dissociates and releases aluminum ions, which interact with the negatively charged particulates, assisting in their aggregation. This process is vital in ensuring clear drinking water by significantly reducing turbidity and removing pathogens.

In contrast, sodium chloride is primarily used for water softening and does not function as a coagulant. Calcium carbonate is often used for pH adjustment and hardness stabilization, while magnesium sulfate serves different purposes, such as being a nutrient in certain water treatment systems, rather than as a coagulant. Thus, alum stands out as a strategic choice in water treatment practices, effectively aiding in the clarification of water through the coagulation process.