The impact of gas slug flow on microfiltration performance in an airlift external loop tubular membrane reactor

© 2016 The Royal Society of Chemistry. This work investigated the impact of gas slug flow on microfiltration in an airlift external loop tubular membrane reactor. A complete description for the characteristics of the slug flow was obtained as the aeration rate increased from 30 to 120 L h-1 with an interval of 30 L h-1. The shear stress of the falling film region could reach 6.37 × 10-3 Pa with the aeration rate of 90 L h-1. Experimental results showed that the growth of transmembrane pressure (TMP) could be controlled effectively by increasing the aeration rate and the optimal aeration rate in a slug flow was around 90 L h-1. However, a subsequent increase in the aeration rate had no significant effect on slowing down the TMP growth rate. Turning the constant air-flow into periodic pulsatile air-flow, low gas-velocity and high gas-velocity led to alternate operation in filtration. When the alternate interval of pulsatile air-flow was 60 s at the alternate aeration rates of 30/90 L h-1 and 60/90 L h-1, it could delay membrane fouling and save a lot of gas compared with implementing a constant air-flow of 90 L h-1. Finally, for different water outlet positions along the membrane tube, membrane fouling gradually slowed down from the bottom to the top