Power effect of ultrasonically vibrated spacers in air gap membrane distillation: Theoretical and experimental investigations

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