Evaluation of sonically enhanced AGMD for industrial scale water treatment

Evaluation of sonically enhanced AGMD for industrial scale water treatment

As the global supply of freshly available water becomes a scarce commodity, low energy and cost-effective schemes to reuse and rectify contaminated water sources are becoming essential. This research investigates air-gap membrane distillation (AGMD), a novel low energy technology aimed at reclamation of contaminated water sources. While previous studies have delved into the control mechanisms of AGMD, they have only been used at extremely small scales, and cannot be readily expanded to an industrial level. In this study, key parameters which affect permeate-flux production such as feedwater temperature, concentration and flow rates were compared with two membrane types on an AGMD system which was around 14 - 18 times larger than the typical systems previously studied.

A novel remediation method has been developed to tackle membrane fouling which is the most commonly encountered problem in membrane technologies. Without cleaning, membrane fouling decreased permeate-flux by approximately 25% after 70 hrs of running with feedwater of 4000 - 12 000 μS/cm. In stark contrast, the external application of ultrasonic energy with a low power range of 40 - 120 W/m2, resulted in a consistently high permeate-flux production (200 - 300 % compared to non-sonicated AGMD) with no signs of fouling evident after a 70 hrs of operation. With this low level of ultrasonic power, the occurrence of cavitational effects is highly unlikely. Hence, the observed permeate-flux improvement was attributed mainly to cleaning effects, along with mass and heat transfer enhancements. This was confirmed by microscopic examination of the membrane surface, which showed no signs of fouling or damage afterwards.