In the context of water treatment, what does flocculation involve?

Flocculation is a critical process in water treatment that is primarily concerned with the aggregation of small particles into larger clusters, known as flocs. This step is essential for improving the efficiency of subsequent purification processes, such as sedimentation and filtration.

The process typically involves the addition of flocculating agents or coagulants that help to neutralize the charges on suspended particles, causing them to come together and form a more substantial mass. This aggregation significantly increases the size of the particles, making them easier to remove from the water through settling or filtration.

While the other options touch upon various aspects of water treatment, they do not accurately capture the essence of flocculation. Stirring water to add air pertains more to aeration processes, filtration focuses on the removal of solid waste without addressing particle aggregation, and chemically altering pH relates to the adjustment of water chemistry rather than the physical assembly of particles. Thus, the concept of combining particles to form a mass is the most suitable definition for flocculation.