Which material is crucial for the coagulation process in water treatment?

The coagulation process in water treatment is primarily aimed at removing suspended particles and impurities to clarify the water. Alum, also known as aluminum sulfate, plays a vital role in this process. When added to water, alum dissolves and forms aluminum hydroxide, which acts as a coagulant. This coagulant gathers small particles together into larger clusters, or flocs, which can then be easily removed from the water, often through sedimentation or filtration.

The effectiveness of the coagulation process is largely dependent on the properties of alum, including its ability to lower the surface charge of particles, allowing them to stick together more effectively. This process is essential in both municipal and industrial water treatment systems, ensuring that the water meets safety and quality standards for consumption or use.

The other materials listed, while important in their own right, do not serve the same primary function as alum in the coagulation process. Chlorine is primarily used for disinfection, fluoride is added for dental health benefits, and sodium hydroxide is utilized for pH adjustment, none of which contribute directly to the coagulation of suspended materials in water.