What is the most used coagulant in water treatment, which can be supplied as a solid or liquid and sometimes contains sodium silicate?

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Coagulation relies on neutralizing the negative charges on tiny particles in water and forming larger, settleable flocs. Aluminum sulfate, or alum, is the most widely used coagulant because it is inexpensive, effective over a wide pH range, and can be fed as a solid or as a liquid. When added, alum hydrolyzes to form aluminum hydroxide flocs that sweep up colloids and color-causing particles, which then settle out or are filtered. Some alum products include small amounts of sodium silicate as a stabilizer or filter-conditioning aid, helping with handling and improving the coagulation/flocculation process. While ferric chloride, lime, and sodium aluminate are used in some plants, alum remains the most common choice for primary coagulation.