Which step is when particles are combined and begin to settle?

Which step is when particles are combined and begin to settle?

• A. Screening
• B. Disinfectant added
• C. Coagulants added
• D. Coagulation and Flocculation

Answer: (D)

Particles are brought together and prepared to settle during the coagulation and flocculation stage. Adding coagulants destabilizes the tiny, stable colloids, neutralizing their charges so they can start interacting. Then gentle mixing (flocculation) promotes collisions and binding among destabilized particles, forming larger clumps called flocs. These larger aggregates are heavy enough to begin settling in the next step. So, the combined process of coagulation and flocculation is the correct choice because it explicitly describes both destabilizing particles and forming settleable aggregates. Screening removes large debris, disinfectants address microbes, and adding coagulants alone starts coagulation but doesn’t complete the formation of flocs needed for settling.

Particles are brought together and prepared to settle during the coagulation and flocculation stage. Adding coagulants destabilizes the tiny, stable colloids, neutralizing their charges so they can start interacting. Then gentle mixing (flocculation) promotes collisions and binding among destabilized particles, forming larger clumps called flocs. These larger aggregates are heavy enough to begin settling in the next step. So, the combined process of coagulation and flocculation is the correct choice because it explicitly describes both destabilizing particles and forming settleable aggregates. Screening removes large debris, disinfectants address microbes, and adding coagulants alone starts coagulation but doesn’t complete the formation of flocs needed for settling.