Which process is the final step in the removal of suspended matter in water?

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

Answer: (A)

Removing suspended matter happens in stages: chemicals are used to destabilize particles and form larger flocs, allowing those flocs to settle out in sedimentation. But even after settling, some finer particles stay suspended. The final barrier is filtration, where water passes through a porous medium (like sand or multimedia) that traps the remaining solids. Aeration adds air and helps with gases and odors, not solid removal. Coagulation creates the flocs but doesn’t remove them by itself, and sedimentation removes most of the flocs but not all suspended particles. Therefore, filtration is the last step to achieve clear water by physically removing the residual suspended matter.