In filtration, the final step in removing suspended matter in water.

• A. Aeration
• B. Filtration
• C. Coagulation
• D. Sedimentation

Answer: (B)

Filtration serves as the final polishing step to remove the remaining suspended matter after earlier treatment steps have consolidated and settled the larger solids. After coagulation and flocculation, most particles form bigger flocs that settle in sedimentation basins, reducing turbidity. Yet some fine particles can still pass through, and that is where filtration comes in: water passes through a porous media bed (like sand or multimedia filters) that physically traps these remaining solids, often aided by adsorption and biofilm action. This final barrier ensures the water is much clearer before disinfection. Aeration and coagulation occur earlier in the process, with sedimentation removing a large portion of solids, while filtration provides the last step to polish the water.