Chlorine dioxide - RO membranes - CEDI

[Schulgarten1]

Hi guys,
is anybody here present, who has experience with applying Chlorinedioxide for sanitizing RO membranes and CEDI systems (CDI systems)?
Thanks for answers and regards
from
Schulgarten- Austria

 

[bimr]

Depends on the type of membrane and CDI system. Some do not recommend it. The best advice is to contact the system supplier.

"Sanitization with agents containing combined chlorine is generally not recommended. FILMTEC membranes have shown some compatibility with pure chlorine dioxide. Chlorine dioxide that is generated on-site from chlorine and sodium chlorate, however, is always contaminated with free chlorine that attacks the membrane. One should consider DBNPA as a safer and more effective sanitizing agent for non-potable applications."

http://dowac.custhelp.com/app/answe...ranes---chlorine-dioxide-(clo2)-compatibility

 

[dfmorvan]

Hi

I used a pilot plant with 4" filmtech membranes in the dairy industry. Chlorine dioxyde concentration was around 1 ppm. It worked fine.
I have no idea about CEDI with ClO2.

regards

 

[bimr]

All well and good. However, operating a pilot plant is somewhat different than operating long term 24/7. Since this equipment is expensive, the best advice is to contact the system supplier and follow their directions.

 

[dfmorvan]

Hi Schulgarten1

some doc

http://www.membranes.com/docs/tab/TAB115.pdf

 

[Schulgarten1]

Hi and good evening!
Thank you for the link! Useful and interesting. I have sanitízed RO membranes, a bit older and definite with biofilm. The biofilm was removed but rejection drop dramitcally. I am sure this was the influence of iron on the membranes. In another case we sanitized a larger system with quite new membranes and definite no iron with good success with about 3 ppm hour. No drop in rejection.
Thank you!

 

[dfmorvan]

During the test we made in a dairy application ( reuse of "cow water" from milk evaporation condensate) we were working @ 1 ppm equivalent Cl2. I was first surprised to see that rejection was not affected. The test lasted for something like a month. So I think that a low residual can give good results on biofouling but at low concentration. Of course caution should be applied, especially as you point out, regarding the presence of iron.

 

[Schulgarten1]

The next tests will go to Ionpures CDI, when I do have a non hot water sanitisation one (hot water sanitisation never has a problem with biofilm), but I need an older moduel, since on a new one, if fails, testing too expensive. I wonder, how the resins within the CDI and the ion exchange membranes will perform after the sanitisation....
Kind regards from the alps and Vienna!

 

[dfmorvan]

As for the resins, cationic resin will be OK as long as the concentration is not too high. I'm more reserved about anionic resins as they will oxidise more easily. You risk losing some strong capacity which is important for capturing weakly ionized species as CO2, SiO2 and Boron. Thereis also the question of the anion membrane which is basically the same polymer as the resin. You're right to test this on an old unit.

Tschussi !

 

[Schulgarten1]

Hello friends!
I wish you a happy 2016 and happy engineering and of course successful projects!
Coming back on resin stabiltiy:
all resins are most stabile for any chemical, oxidation or hydraulic-osmotic shocks when fully exhausted and loaded with NaCl. In this case both cationic and anionic parts are fully loaded and shrinked - compareable to human in a safety position awaiting beasts, whatsoever.
We will definite in this state.
Regards from the Austrian alps - where at the moment it is more spring than winter....