Effects of concentration polarization, temperature and pressure on ultrasound detection of inorganic fouling and cleaning in a spiral-wound membrane module
Chai, G. Y.
Zhao, G. Y.
Greenberg, Alan R.
Krantz, William B.
Date of Issue2012
School of Civil and Environmental Engineering
Singapore Membrane Technology Centre
Ultrasonic time-domain reflectometry (UTDR) involves passing an acoustic wave through a medium and analyzing the reflected waveform. In this study, UTDR is used to track the waveform peaks reflected from the outer and inner membranes in the outermost feed channel in a Koch 2521 spiral-wound module. The UTDR amplitude is shown to be more sensitive to fouling than the transit (arrival) time. The local (point) measurement provided by UTDR is shown to be advantageous since its location can be optimized for early fouling detection. Concentration polarization is shown not to compromise UTDR. This is an advantage relative to flux decline that responds to both fouling and concentration polarization. The UTDR amplitude is found to increase with increasing temperature and decreasing pressure. This is explained by the effect these parameters have on the crystallization rate that changes the fouling layer morphology and thereby the reflected UTDR waveform. This study underscores the importance of establishing a UTDR reference surface suitable for unambiguous detection of fouling. It also emphasizes the necessity for good temperature and pressure control during UTDR measurements as well as a more comprehensive understanding of the effects of operating condition changes on the ultrasound waveforms.
Desalination and water treatment
© 2012 Desalination Publications. This paper was published in Desalination and Water Treatment and is made available as an electronic reprint (preprint) with permission of Desalination Publications. The paper can be found at the following official DOI: [http://dx.doi.org/10.1080/19443994.2012.744718]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.