This study investigates the efficiency of low-power ultrasound in the range of 3.5–30.0 W to improve permeate flux and alleviate membrane fouling in an air–gap membrane distillation (AGMD) system. Natural groundwater and reverse osmosis (RO) reject water were fed into the AGMD system on which fouling experiments were conducted with hydrophobic polyvinylidene fluoride (PVDF) membrane. After 35 h of AGMD system operation with groundwater and RO reject water, fouling caused the permeate flux to decrease by 30% and 40% respectively. Concentration polarization, intermediate pore blocking, and cake filtration appear to be the main reasons for flux decline with both feedwater types. Ultrasound application for a short period of 15 min resulted in flux improvement by as high as 400% and 250% for RO reject and groundwater, respectively. Modelling of the heat and mass transfers showed that the flux increase was mainly due to membrane permeability improvements under ultrasonic vibration. Fouling visualisation using Scanning Electron Microscopy revealed that ultrasound effectively removed membrane fouling without compromising the membrane’s structure. Importantly, permeate flux improvements with targeted low-power ultrasound appears to be proportionally higher than those of high-power ultrasound applied to the whole system, on a flux improvement per ultrasound W/m² basis.

这项研究调查了在3.5-30.0 W范围内的低功率超声在气隙膜蒸馏（AGMD）系统中提高渗透通量和减轻膜污染的效率。将天然地下水和反渗透（RO）废水送入AGMD系统，在该系统上用疏水性聚偏二氟乙烯（PVDF）膜进行结垢实验。在使用地下水和反渗透水的AGMD系统运行35小时后，结垢导致渗透通量分别减少30％和40％。浓度极化，中间孔阻塞和滤饼过滤似乎是两种给水类型通量下降的主要原因。在短短15分钟的时间内使用超声波，反渗透水和地下水的通量分别提高了400％和250％。传热和传质的模型表明，通量的增加主要是由于超声振动下膜渗透率的提高。使用扫描电子显微镜对污垢进行可视化显示，超声波可以有效去除膜上的污垢，而不会损害膜的结构。重要的是，针对低功率超声的渗透通量改善似乎比应用于整个系统的高功率超声的渗透通量改善成比例地更高，每超声通量改善W / m²基础。