Title: Flux patterns and membrane fouling propensity during desalination of seawater by forward osmosis

Journal: Water Research

Authors: Zhen-Yu Li, Victor Yangali-Quintanilla, Rodrigo Valladares-Linares, Qingyu Li, Tong Zhan, Gary Amy

Institute: Water Desalination and Reuse Center (WDRC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
Corresponding author: Gary Amy

The original and creativity of paper: The paper examined flux patterns and membrane fouling propensity of forward osmosis using seawater.

Summary: 

-    In semi-batch mode of FO filtration process, the external concentration polarization, fouling related resistance, and fouling related to concentrative internal concentration polarization are the major to affect flux decline.

-    The fouling which developed on the membrane surface was scaling-like foulant surrounded by biopolymeric substance.

-    In this paper, they mentioned that the scaling is caused by the polymerization of dissolved silica. 

-    After 10 batches of filtration with cross flow velocity of 16.7 cm/s, high concentration of sodium and chlorine were found due to the salinity of seawater. Interestingly, even though the amount of silica in seawater is quite low but the high peak of silica is observed. Therefore, the scaling-like foulants could be due to the deposition of silica.

-    The polymerization of silica during FO filtration could be initiated by accumulation of silica onto membrane surface and then create the concentrative external concentration polarization (CECP).

-    During the polymerization process, monosilicic acid and polysilicic acid can react with organic compound to form anhydrides that accelerates organic fouling and changes surface morphology of membrane. 

-    High crossflow velocity could reduce external concentration polarization.

-    NOM foulant in the fouling matrix is possible to remove by water flushing, whereas silica scaling is difficult to clean by hydraulically method.  

-    In order to control fouling, understanding of factor affecting the fouling formation and fouling layer composition is required.


Application & further study: The information presented in the paper is very useful for researches who study about fouling mechanism.


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