TY - JOUR
T1 - Ultrasonic sensor control of flow reversal in RO desalination. Part 2
T2 - Mitigation of calcium carbonate scaling
AU - Mizrahi, Guy
AU - Wong, Kevin
AU - Lu, Xiaoyun
AU - Kujundzic, Elmira
AU - Greenberg, Alan R.
AU - Gilron, Jack
N1 - Funding Information:
The authors gratefully acknowledge support of this work by the NATO Science for Peace Program (SfP 982481 ) and the Middle East Desalination Research Center ( MEDRC08-AS-003 ). We also acknowledge support by Rotec, Ltd., which funded Mr. Mizrahi's graduate fellowship. We also thank Mr. Yitzhaq Lutwak and Mr. Naphtali Daltrophe for their technical assistance and Ms. Anna Mamontov for analytical support.
PY - 2012/11/15
Y1 - 2012/11/15
N2 - The use of ultrasonic time-domain reflectometry (UTDR) in combination with statistically based analysis has been utilized to provide timely warning of the initial onset of local calcium carbonate scaling. The methodology was able to detect the onset of scaling in real time before any significant decrease in permeate flux was observed. Ultrasonic detection of scaling was confirmed via post-mortem examination of the membrane that showed the presence of aragonite crystals that were as small as 20 μm and covered less than 10% of the membrane surface. The ultrasonic methodology was then employed to trigger a change in flow direction (reversal of the concentrate and feed ends of the flow channel) when scaling was detected. When in forward flow, the upstream, midstream and downstream sections of the membranes had aragonite supersaturation values of SI~2.0, ~5.3 and~7.65, respectively; when the flow direction was changed, the SI values at the ends were switched but the SI at the midstream remained at SI~5.3. Results indicated that flow reversal effectively mitigated scaling in downstream sections of the membrane even though they were periodically exposed to the highest supersaturation conditions. It was demonstrated that prompt intervention after an ultrasonic scaling signal improved the efficacy of flow reversal. The results reflect a significant advance in the use of UTDR in which the methodology is applied for active control of scaling miti ation rather than limited to passive detection of scale formation.
AB - The use of ultrasonic time-domain reflectometry (UTDR) in combination with statistically based analysis has been utilized to provide timely warning of the initial onset of local calcium carbonate scaling. The methodology was able to detect the onset of scaling in real time before any significant decrease in permeate flux was observed. Ultrasonic detection of scaling was confirmed via post-mortem examination of the membrane that showed the presence of aragonite crystals that were as small as 20 μm and covered less than 10% of the membrane surface. The ultrasonic methodology was then employed to trigger a change in flow direction (reversal of the concentrate and feed ends of the flow channel) when scaling was detected. When in forward flow, the upstream, midstream and downstream sections of the membranes had aragonite supersaturation values of SI~2.0, ~5.3 and~7.65, respectively; when the flow direction was changed, the SI values at the ends were switched but the SI at the midstream remained at SI~5.3. Results indicated that flow reversal effectively mitigated scaling in downstream sections of the membrane even though they were periodically exposed to the highest supersaturation conditions. It was demonstrated that prompt intervention after an ultrasonic scaling signal improved the efficacy of flow reversal. The results reflect a significant advance in the use of UTDR in which the methodology is applied for active control of scaling miti ation rather than limited to passive detection of scale formation.
KW - Calcium carbonate
KW - Flow reversal
KW - Membrane scaling
KW - Ultrasonic time-domain reflectometry
UR - http://www.scopus.com/inward/record.url?scp=84864988702&partnerID=8YFLogxK
U2 - 10.1016/j.memsci.2012.05.026
DO - 10.1016/j.memsci.2012.05.026
M3 - Article
AN - SCOPUS:84864988702
SN - 0376-7388
VL - 419-420
SP - 9
EP - 19
JO - Journal of Membrane Science
JF - Journal of Membrane Science
ER -