During water treatment, what is usually added to enhance coagulation?

In the water treatment process, enhancing coagulation is essential for effectively removing suspended solids and impurities from the water. Alum, a well-known coagulant, consists primarily of aluminum sulfate. When added to water, alum hydrolyzes and forms positively charged aluminum hydroxide particles. These particles attract and bind with negatively charged particles and colloids in the water, facilitating their agglomeration into larger floc particles that can settle more easily during sedimentation. This process improves the clarity and quality of treated water.

Using alum is a widely accepted practice because it effectively reduces turbidity, enhances sedimentation, and can also help remove certain contaminants. Cationic polymers, while also used as coagulants and flocculants, are typically employed as adjuncts or aids in specific circumstances, but alum remains the most common and traditional choice for enhancing coagulation in water treatment.