An example of physical treatment of a waste is:

• A. distillation
• B. stabilization
• C. vitrification
• D. precipitation

Answer: (A)

The main concept is distinguishing physical treatment from chemical treatment of waste. Distillation uses differences in volatility to separate components through boiling and condensation, a pure physical separation—no chemical reactions occur and the chemical identities stay the same. This makes it a physical treatment, useful for removing solvents or concentrating organics without altering their chemistry. In contrast, stabilization and vitrification involve transforming the waste chemically or embedding it in a solid/glassy matrix to immobilize contaminants, and precipitation involves forming solid salts from dissolved ions—both chemical changes. Therefore distillation is the best example of a physical treatment of waste.