What is the final step in the removal of suspended matter in water after coagulation and sedimentation?

Filtration is indeed the final step in the removal of suspended matter from water after the processes of coagulation and sedimentation. This step is crucial in ensuring that any remaining small particles or flocs—formed during coagulation and settled out during sedimentation—are effectively removed before the water is subjected to disinfection or distribution.

During coagulation, chemicals like aluminum sulfate are added to the water, which causes small particles to clump together into larger aggregates known as flocs. These flocs then settle to the bottom of the sedimentation basin, allowing clearer water to pass over the top. However, some finer particles may still remain suspended in the water column. Filtration involves passing the water through a filter medium, typically composed of sand, gravel, or activated carbon, which captures these tiny remaining particles and any additional contaminants.

This multi-step treatment process is designed to produce water that is safe for consumption and meets public health requirements. With filtration as the final step, the water is as clean as possible before any further treatments are applied. Disinfection, which is often performed afterwards, serves to eliminate pathogens that may still be present but is not part of the physical removal of suspended matter.