What is the primary purpose of coagulants in water treatment?

The primary purpose of coagulants in water treatment is to assist in flocculation and sedimentation. Coagulants, such as aluminum sulfate or ferric chloride, are added to water to destabilize suspended particles, including colloids and organic matter. When these particles are destabilized, they can agglomerate, or come together, forming larger aggregates known as flocs. These flocs are significantly easier to remove from water during the sedimentation process, as they can settle out of the water column more rapidly than individual particles. This process effectively clarifies the water, removing impurities and improving overall water quality before further treatment steps, such as filtration and disinfection, are carried out.

Using coagulants is crucial for the efficiency of subsequent treatment phases. While disinfectants are important for pathogen removal, adjusting pH can be carried out by other chemicals, and adding minerals for taste does not address the immediate goal of particle removal and clarification. Thus, the role of coagulants is specifically geared towards enhancing the removal of suspended matter through the formation of larger, settleable particles.