Which chemicals are commonly used for coagulation in water treatment?

Coagulation is a critical step in the water treatment process, aiming to remove suspended particles and impurities from water. The correct chemicals used for this purpose are alum and polymers.

Alum, which is a type of aluminum sulfate, serves as a coagulant by neutralizing the charge on particles in the water, allowing them to clump together and settle more easily. Polymers are often used in conjunction with alum to enhance the coagulation process. They help to form larger aggregates, or flocs, by providing additional binding sites for the particles, improving the effectiveness of the coagulation process and ensuring that suspended solids can be effectively removed during subsequent filtration.

In contrast, the other options do not serve the primary purpose of coagulation. Chlorine and ozone are disinfectants primarily used for killing pathogens in water, not for coagulation. Calcium and magnesium are essential minerals that may be present in water but do not have coagulative properties. Iron oxide and sodium sulfate, while they might have roles in other treatments, are not standard coagulants and lack the effectiveness of alum and polymers in achieving coagulation.