I am working on an experimental SWRO plant with Ultrafiltration module. The Chemical Enhanced Backwash cycle for the UF membrane constitutes a biocidal flushing (NaOCl) followed by low pH HCl (2-3) and finally high pH NaOH (11-12)wash. The backwash solution is generated by injecting the said chemicals directly into UF permeate line from UF permeate storage tank. It is observed that that the NaOCl and NaOH dosing ports are getting frequently clogged due to precipitation of calcium carbonate (confirmed by chemical analysis of the precipitated scale).
Any suggestions on how to prevent this without reducing the pH (since the high pH is required for efficient cleaning)?
Can some alternate dosing arrangement be made to prevent this? Or using RO permeate instead of UF permeate solve this issue? Any other suggestions based on experience are also welcome.
Dear!
The effectiveness of using magnetic treatment to prevent fouling caused mainly by calcium carbonate has been scientifically proven. There are more than 500 patents in the world for magnetic conditioners or softeners. Check bibliography about it for a few
posible influence pH.
Greets you,
MSc. Ing. Nuria Vaillant
I agree with the idea of magnetic treatment to prevent CaCO3 precipitation. I also agree with the idea of using RO permeate as it is practically free of calcium.
The main problem is the partial transition of NaOH and NaOCl to Na2CO3 and NaHCO3 due to contact with air (CO2). Therefore, you can also try deaeration or using concentrated solutions.
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