USE OF SEALED END HOLLOW FIBERS FOR BUBBLELESS MEMBRANE AERATION - EXPERIMENTAL STUDIES

A novel microporous hollow fiber membrane module was evaluated for the oxygenation of water. Pure oxygen is maintained inside a bundle of sealed-end polypropylene fibers at a pressure below the bubble point. The water to be aerated is pumped over the outside of the fibers. The high oxygen concentration gradient encourages the oxygen to diffuse across the porous membrane wall, and to dissolve directly into the water without the formation of bubbles. The membrane is hydrophobic and the pores small enough that they stay dry and gas filled so that the transport across the membrane is by gaseous diffusion. The membrane itself therefore provides little resistance to transfer, and the mass transfer rate is controlled by diffusion across the liquid film on the outside of the fibers. Modules of varying size were tested and transfer correlations were developed for module design. The process gave 100% oxygen transfer efficiency at a reasonable power input. For water quality management and waste treatment, oxygenation by membranes appears to offer many advantages over conventional aeration devices.