What is a common chemical coagulant used in water treatment?

Aluminum sulfate, commonly known as alum, is a widely used chemical coagulant in water treatment processes. It works by neutralizing the charge on suspended particles in water, allowing them to clump together into larger aggregates, a process known as flocculation. This is essential in removing impurities and turbidity from the water, making it clearer and safer for consumption.

Alum is particularly effective because it dissolves in water, producing positive aluminum ions that attract negatively charged particles, such as dirt and organic matter. These particles then adhere to the alum, forming flocs that can be easily removed through sedimentation and filtration.

In contrast, chlorine dioxide is primarily used as a disinfectant rather than a coagulant, calcium carbonate is used for pH adjustment and hardness control, and sodium chloride serves as a source of sodium ions, but is not involved in the coagulation process. Therefore, the use of aluminum sulfate is a critical step in the effective treatment and purification of drinking water.