0531_How to estimate inorganic fouling flux on RO membrane by using ROIFA-4?



Title: How to estimate inorganic fouling flux on RO membrane by using ROIFA-4? 
Journal: Desalination
Authors: Samir El-Manharawya and Azza Hafezb, 
Institute:    a Nuclear Geochemistry Dept., Nuclear Materials
b Chemical Engineering Department and Pilot Plant, National Research Centre, Cairo, Egypt

The original and creativity of paper:  The paper aimed to reveal an assessment of inorganic fouling in reverse osmosis (RO) process using RO Inorganic Fouling Assessment?version 4 (ROIFA 4). 


-    It has been reported that users satisfied the performance of   ROIFA software, especially in this study, the model can be well predicted inorganic fouling during RO process.  
-    The software was satisfied by several users for more than two years.
-    This model can calculate fouling fraction, fouling load, and fouling flux automatically using excel spreadsheet which is not complicated.
-    However, there are several points to be noticed:
o    At high brackish waters (TDS < 7000 mg/L) revealed poor linearity flux-recovery-curve.
o    The guideline limit of starting inorganic fouling of flux range is 8.00E + 17.
o    Feed water ion analysis is very sensitive.  Therefore, if the difference between cation and anion is higher than 3%, the result might not accurate. 
o    The fouling rate that calculated using this program was not affected by the varying of temperature.
-    The assumption of model are:
o    Minerals dissolved in water based on the hydration theory.
o    Under normal physical condition, hydrated ions dissolves in the form as same as its original compound and it has a capability to re-crystallize to the original compound.
o    Normally, the dissolved hydrated ions reveal in less active ion-pairs.
o    Dehydration of dissolving hydrated molecules on the membrane surface was considered as a random process. 
o    It is assumed that: 1) all dehydrated molecules could be dehydrated; 2) a fraction of the hardness molecules (e.g., CaSO4 and CaCO3) could foul as solid particles; and 3) others molecules (e.g., NaCl, Na2SO4 and MgCl2) could re-dissolve. This assumption based on their solubility and the available time necessary for re-dissolution.
o    Scale formation depends on the maturation of deposited solid particle size forming the initial crystal nuclei under preferred condition.
o    Only part of dissolved hardness molecules will be precipitated on membrane surface. This is because the CaSO4:CaCO3 ratio in brine solution and in scaling layer is a considerable difference.  

Application: The author provided free excel spreadsheet for RO inorganic fouling assessment using ROIFA-4. Therefore, we can try to apply the software to assess inorganic fouling in our SWRO system.
By Monruedee Moonkhum
Email: moon@gist.ac.kr

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