Which of the following is a chemical treatment in water treatment process?

Concept

Water-treatment operations are classified as physical, chemical, or biological according to their principal mechanism.

Physical operations separate matter without relying on a chemical reaction; chemical operations add or use reactive substances to alter contaminants.

Application

In coagulation, a coagulant such as alum or a ferric salt is added to destabilize charged colloidal particles and promote their aggregation into flocs.

Contrast

• Filtration passes water through a porous medium to retain suspended particles; this is a physical separation operation.

• Sedimentation allows denser suspended matter to settle under gravity; this is a physical separation operation.

• Screening intercepts coarse floating and suspended matter with bars or meshes; this is a physical separation operation.

• Coagulation changes colloidal stability through an added coagulant; this is a chemical operation.

Result

Therefore, coagulation is the chemical treatment among the listed processes.