Which force pulls particles together once they have been destabilized in the coagulation-flocculation process?

During the coagulation-flocculation process, particles in water are destabilized and then need to aggregate to form larger flocs for effective sedimentation and filtration. The force that primarily acts to pull these destabilized particles together is the Van der Waals force.

Van der Waals forces are weak intermolecular forces that arise from temporary dipoles that occur when the electron distribution around molecules shifts. Once particles are destabilized through coagulation, these forces become significant as they promote the aggregation of the particles into larger clusters, or flocs. As flocs increase in size, they can more easily settle out of the water column.

Other forces such as gravitational force, eddy force, and centrifugal force play a role in the overall sedimentation and removal of particles from water, but they do not specifically relate to the aggregation of particles once they are destabilized. Gravitational force impacts the movement of flocs after they have formed, eddy forces can disrupt particle movement but aren’t responsible for attraction, and centrifugal force is typically applied in processes like centrifugation rather than in the initial floc formation due to Van der Waals forces.

Therefore, Van der Waals force is key in facilitating the initial attractive interactions necessary for particle aggregation during