Influence of Aeration Pipe Length on Oxygen Mass Transfer Efficiency in Terms of Bubble Motion Flow Field

Abstract

Improving the gas–liquid mass transfer efficiency in microporous aeration technology is the key to strengthening the restoration effect of black and odorous water bodies. However, the effect of bubble motion characteristics on oxygen mass transfer has not been systematically studied, which limits the efficient and economical application of microporous aeration remediation technology in black and odorous water. The influence under different aeration pipe lengths was analyzed for oxygen mass transfer and bubble movement in microporous aeration technology. The aeration pipe length (0.1–0.5 m) was positively correlated (R = 1.000, R = 0.997) with the number of bubbles and the specific surface area of bubbles and negatively correlated with the time-average velocity of bubbles and Sauter average diameter (R = −0.999, R = −0.997). Moreover, the increase in pipe length weakened the disturbance intensity of plume to water body. The results of oxygen mass transfer showed that the oxygen mass transfer coefficient (K L a) and oxygen utilization rate (E A) increased (K L a from 1.96 to 4.57 h–1, E A from 6.47 to 15.07%) with the increase of pipe length, which was significantly positively correlated (R = 0.985, R = 0.969) with the number of bubbles and bubble specific surface area (S b). This study provided theoretical parameters for the mechanism of oxygen mass transfer during microporous aeration.