Which chemical is NOT typically used as a coagulant in water treatment?

Sodium bicarbonate is not typically used as a coagulant in water treatment processes. Coagulants are chemicals that help to aggregate and settle suspended particles in water, facilitating the removal of impurities. Common coagulants, like aluminum sulfate and ferric chloride, work by neutralizing the charges on particles so they can clump together, making them easier to remove from the water through sedimentation or filtration.

Aluminum sulfate and ferric chloride are effective coagulants due to their ability to create hydroxides that form flocs, aiding in the clarification of water. Synthetic polymers also serve as coagulants or can enhance the coagulation process by assisting in the floc formation.

In contrast, sodium bicarbonate primarily functions as a pH adjuster or alkalinity increaser rather than a coagulant. Its role in water treatment usually pertains to balancing the pH and not to the coagulation of particles, which differentiates it from the coagulants mentioned above.