Help!!

[Indumathis]

hi,

we use Tangential Flow filtration for the seperation of cell debris and in the past few runs we have had problmes with teh downward trendingof the permeate flow untill the last runit was almos zero. We did a routine maintanance by replacing all teh gaskets etc. but couldnto find any problem. We use Pall filters adn all the runs the integrty tests for bothpost and pre runs were good. The only thing is that we don't have readings for perssure sinc ethe operators did not note it down for the runs. Would there be a problem with the way they maintained the perssures on the feed, retantate and permeate. The TMP was maintained the same though.

The last run when there was 0 permeate flwo, the flow picked up when we reduced th eretentae flow and we don't know why such a behaviuor.
Please advise.

 

[mbrown]

Indumathis,

If your unit has a tank for cleaning in place I would try a complete cleaning first. Call your membrane supplier and find out what cleaning solvents they recommend for your unit and pick the harshest one compatable with your material. Find out from them if you can backflush your membranes. Also see if you can get them to send a technical service rep. to your account to help troubleshoot. If you still cannnot recover the membranes you may need to replace them. It is EXTREMELY important to maintain a min. flow across a membrane whenever it is in contact with a process fluid. You simply must know what inlet and outlet pressures are at all times. And do not allow process fluid to sit in contact with a membrane, if you must stop flow, flush the membranes with DI water as soon as possible. And if at all possible have either Pall, your membrane supplier, or the pump supplier bring in a ultrasonic flow meter and measure what flow you are getting. One important lesson that I have learned (painfully I must admit) is that flow and pressure, while related, are not the same thing.

Email me directly if you have any other questions

Mike Brown
mbrownpti@aol.com

 

[johbil]

I agree with the previous post. I'm not sure I completely understand your set up, but it seems you are microfiltering in a feed and bleed set-up. You seem to be describing a typical fouling problem. You will need to find out if you can avoid the fouling. Increasing feed pressure might compact your gel layer and give a similar effect. For microfiltration you want to keep the feed pressure as low as possible. In any case, once fouled you will need to clean the membranes.

 

[Indumathis]

Thanks for all of you for replying. We do change the membranes after every run(which is really stupid but thats not my decision).
So the fouling would have gotten taken care of but maintaing the pressures is something we have to look into and come up with some ideal pressures for the system that we can set and not alter all the time.

If there are any websites or books that you could suggest to help me get more information, it would be very helpful.

Thanks again.

-Indu