Bubbleless fiber aerator for surface waters

The concept of bubbleless aeration with microporous hollow fiber membranes is tested in a system that does not require external energy input, other than pressurizing oxygen, and is designed to add oxygen to surface waters. Microporous hollow fiber membranes, potted at one end and connected to an oxygen supply, with the other end individually sealed, were installed vertically in a flume to simulate their performance in rivers and lakes. The gas-filled fibers tend to rise vertically due to buoyancy, while bending downstream due to the drag force exerted by the flowing water. When operated at differential pressures of up to 3 atm during the experiments, this cross-flow configuration resulted in high rates of gas transfer with no supplemental energy input. Gas-transfer coefficients were found to depend on cross-flow velocity and internal gas pressure for the tested fibers. Two possible applications for passive hollow fiber membrane aeration are considered, and contrasted with traditional methods of aeration.