What substances are used to promote coagulation in water treatment?

Coagulants are substances used in water treatment to promote coagulation, which is the process of aggregating and clumping together suspended particles so that they can be removed from the water. Coagulants work by neutralizing the charges on particles, making it easier for them to come together. Common coagulants include aluminum sulfate (alum), ferric chloride, and polymeric coagulants. This process is essential in the treatment of water, as it helps in clearing turbidity and improving water quality.

While other substances mentioned, such as flocculants, can also aid in the process of particle removal by facilitating the aggregation of particles into larger flocs, they are typically used after the coagulation stage to enhance settling. Disinfectants, on the other hand, are used to kill disease-causing microorganisms in the water but do not directly participate in the coagulation process. Purifiers is a broad term that may refer to any method of purification, but it does not specifically indicate the role of coagulation in water treatment. Therefore, the specificity of coagulants in promoting coagulation makes them the correct answer in this context.