Title: Implications f enhancing critical flux of particulates by AC fields in RO desalination and reclamation.

Journal: Desalination

Authors: Y.P Zhang, T.H. Chong, A.G. Fane, A. Law, H.G.L. Coster, H. Winters
Temasek Professor Programme, NTU, Singapore UNESC centre, UNSW, Australia

The original and creativity of paper: Fouling in reverse osmosis was discussed as the term of critical flux and fouling mechanisms according to hydraulic resistance as well as loss of driving force due to cake-enhanced osmotic pressure. 

Summary:

    Fouling can be explained in many terms. However, in this paper, fouling was explained using critical flux, fouling mechanism, and loss of driving force due to cake-enhanced osmotic pressure. 
    The calculations of the contributions of fouling resistance (Rf) and cake-enhanced osmotic pressure (CEOP) to ?TMP (constant flux) for cake of 10 microns thickness with the different particle sizes were discussed in this paper.  The results revealed that CEOP increased when particle size and salt concentration increase for the higher flux condition. Moreover, the calculations at the greater cake thickness show an increased contribution caused by CEOP. Also, when the pressure was fixed, the estimated CEOP contribution is lower while the flux is allowed to decline due to fouling.  However, in the practice, RO plant will operate at fixed permeate flux. Therefore, TPM is adjusted according to accumulation of foulant on membrane surface.   It is expected that the CEOP effect is less for low salt feed concentration. 
    In the case of biofilm, its major cause is due to extracellular polymeric substances (EPS) which could cause CEOP. The result found that the CEOP increased dramatically relative to Rf.
    Aside from cake thickness, critical flux also depends on the rate of deposition. All of particle size could deposit at typical spiral wound module (SWM). However, when SWM was dropped to 13.5 L/m2, the 1 micron particles would not tend to deposit at all. 

Application & further study: 
    According to this study, the results can explain more about fouling behavior which possible lead to the understanding of fouling mechanism. Further study could be study more to enhance critical flux, in order to enhance the efficiency of RO process.


By Monruedee Moonkhum
Email: moon@gist.ac.kr