Turbulent jet-assisted microfiltration for energy efficient harvesting of microalgae

Abstract

For energy-efficient harvesting of microalgae using a hollow fiber membrane, a turbulent jet was implemented to induce local high crossflow velocity near the membrane surface for fouling reduction during microfiltration. The performance of the turbulent jet-assisted module was evaluated and compared to that of a control group that represented other types of flow conditions including the conventional-type hollow fiber membrane module. When assisted by the turbulent jet, permeate flux at the steady-state increased by 126% and the specific energy for filtrating out a unit volume of permeate was reduced by 38% relative to the conventional type. In the results of a computational fluid dynamics analysis, the wall jet created after impingement of the jet flew along the membrane surface with a reduced boundary layer, and it is expected that this provided a scouring phenomenon. Shear stress on the membrane surface increased 3.7-fold on average, and was highest at the point of impingement. With regard to energy efficiency, concentrating on increasing the local fluid velocity near the membrane via turbulent jets rather than increasing the entire feed recirculation is more practical to improve the filtration performance for microalgae harvesting with low power consumption.