Title: How to estimate inorganic fouling flux on RO membrane by using ROIFA-4?
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