Which term describes air lift?

• A. Absorption
• B. Aeration
• C. Air lift
• D. Adsorption

Answer: (C)

Air lift describes a pumping method that uses compressed air to raise liquid. In an air-lift setup, air is injected at the bottom of a riser, creating bubbles that entrain water and reduce the overall density of the column, causing the mixture to rise and lift wastewater to a higher level. This mechanical lifting action is different from aeration, which is about mixing air into water to transfer oxygen for biological treatment. Absorption and adsorption refer to how contaminants interact with liquids or surfaces, not to lifting water. So the term that matches the described action is air lift.