Which treatment is not a physical treatment?

• A. Filtration
• B. Sedimentation
• C. Coagulation and Flocculation
• D. Oxidation

Answer: (D)

The main idea is distinguishing physical removal from chemical alteration in water treatment. Filtration and sedimentation remove contaminants mainly by physical separation—filtration traps particles in a barrier, and sedimentation allows solids to settle by gravity. Oxidation, on the other hand, changes the chemical form of contaminants through reactions with oxidants, which is a chemical process rather than a purely physical one. Coagulation and flocculation involve adding chemicals to destabilize suspensions and form larger aggregates; the use of chemical coagulants means the method relies on chemical changes, even if it ultimately results in physical removal. So the treatment that is not a physical treatment is oxidation.