Reverse osmosis (RO) desalination is a well-established process that removes salt from sea water or brackish water sources. However, scaling by sparingly soluble salts on the membrane surface has been shown to significantly degrade membrane performance. We report the results from a comprehensive study evaluating the effectiveness of flow reversal (FR) controlled by ultrasonic sensors in mitigating scaling during RO desalination. The work utilized a sophisticated multi-port bench-scale flat-sheet cross-flow module with the ability to operate in FR mode with externally mounted ultrasonic sensors. A novel signal-analysis methodology was developed to utilize the ultrasonic waveforms to control a switch in flow direction at the onset of local scaling. Experiments were conducted under controlled conditions with repeated forward-flow (FF) and reverse-flow (RF) cycles. Data from the experiments confirmed that FR controlled by ultrasonic sensors can effectively mitigate scaling on the membrane surface and avoid the expected level of permeate-flow decrease. These results were validated by post-mortem membrane analysis including scalant gravimetric and membrane area-coverage measurements. Overall, the work demonstrates the successful adaptation of ultrasonic sensors for active process control in which the timing of the change in flow direction is critical.
|Number of pages
|Journal of Membrane Science
|Published - Nov 15 2012
Bibliographical noteFunding Information:
The authors gratefully acknowledge support of this work by the NATO Science for Peace Program (no. SfP 982481 ), the Middle East Desalination Research Center (no. MEDRC 08-AS-003 ), and the ROTEC, Ltd . The authors also acknowledge support from the National Science Foundation via NSF REU Supplement Award IIP 0624157 for Mr. Jay Wang. Finally, we acknowledge invaluable assistance provided at the University of Colorado Boulder by Dragan Mejic in the Department of Chemical and Biological Engineering Instrument Shop, John Coyle in the Department of Mechanical Engineering Electronic Shop, and Darren McSweeney in the Integrated Teaching & Learning Laboratory (ITLL).
- Membrane scaling
- Reverse osmosis
- Sensor-controlled flow reversal
- Ultrasonic time-domain reflectometry
ASJC Scopus subject areas
- Materials Science (all)
- Physical and Theoretical Chemistry
- Filtration and Separation