Which statement best describes an air lift pump?

• A. A chemical used to accelerate degrade
• B. A pump that uses gravity
• C. A pump that lifts water using impellers
• D. Type of pump, air injected at the bottom to lift water to the top, like percolator coffee pot

Answer: (D)

Air lift pumps work by injecting air at the bottom of a water column. The bubbles mix with the water, lowering the density of the liquid column and creating buoyant lift. Because the air supply adds energy and the column becomes less dense than the surrounding water, the mixture rises up to the top and exits. There are no moving impellers involved—the lifting is driven by the air supply itself, similar to how air bubbles push liquid upward in a percolator coffee pot. This setup is common in wastewater contexts where a gentle, low-head lift is needed and where an air compressor provides the driving energy.