Long‐Term Performance of Parallel‐Flow, Bubbleless, Hollow‐Fiber‐Membrane Aerators

Abstract

Microporous hollow‐fiber membranes can be used to transfer oxygen to water without producing bubbles. The membrane aerator consists of a large number of sealed end fibers potted into an external shell. Pure oxygen is maintained inside the hollow, gas‐permeable fibers at a pressure below the bubble point, and the water to be aerated is pumped over the outside of the fibers. The concentration gradient across fiber drives the oxygen to diffuse across the porous fiber walls and dissolve directly into the water without the formation of bubbles. The process provides 100% oxygen‐transfer efficiency at a reasonable power input. Mass‐transfer characteristics of membrane aerators are reviewed and laboratory test and evaluation procedures are presented in this paper. Field tests were conducted to evaluate the performance of the aerator in a variety of water and wastewater treatment applications. These tests have confirmed that membrane aerators can be used successfully over long periods of time without substantial loss of oxygen‐transfer efficiency.