Which chemical is commonly used for coagulation?

Alum, or aluminum sulfate, is widely recognized as a key chemical used in the coagulation process within water and wastewater treatment. Coagulation involves the addition of a coagulant to destabilize colloidal particles and organic matter in the water, allowing them to aggregate into larger flocs that can be easily removed during subsequent filtration or sedimentation processes.

Alum works effectively because it has properties that promote the neutralization of the charges on colloidal particles, encouraging them to flocculate together. This process improves the clarity of water and reduces turbidity, thus enhancing the overall efficiency of the treatment system.

While other chemicals mentioned, like calcium carbonate, magnesium sulfate, and sodium chloride, have their respective roles in water treatment, they are not primarily used for coagulation. Calcium carbonate is often used to adjust pH, magnesium sulfate can be utilized in some nutrient removal processes, and sodium chloride typically serves as a source of chloride ions or for softening, but none have the coagulation efficiency that alum provides.