Nano-filtration vs real RO

[Brent]

Last week a town just a few miles from here hosted the IMSA, the USMSA, about 15 state associations and Ontario and Quebec .... complete with about 20 technical presentations. Unfortuately they had two presentation rooms going at once and I missed the session done by Sandra Robaire and Dr Alfa Arzate of ACER Quebec on RO membranes.

Sandra was kind enough to email her presentation pdf file, which I think gives me about half of what she presented. In the study they compared several nano-filtration membranes to 2 real RO membranes with the Filmtec BW30 used as the base because it had the best rejection in all categories. Up until now I had my eye on the NF270, but the study revealed that this one had the single biggest defect of the 9 in the study, passing too much of the potasium. It looks like they also found that this made signifigant changes in the syrup.
Both the true RO membranes recieved a pass.
5 of the 7 nanofiltration (NF) membranes "did not meet the basic (*syrup*) quality requirements"

So, I have never heard of anyone using a Filmtec BW30 for syrup. There is nothing in the presentation slides the I got the sheds any comparative light on how well these membranes plug up and clean up.

The BW30-4040 rates 2400 GPD while the XLE-4040 rates 2600 GPD. Less than a 10% difference.

Can anyone out there shed some more light on this? Maybe fill in more if they saw the presentation.

PS: ACER should have an English version on their web site in a week or so.
http://www.centreacer.qc.ca/

[lew]

20 years ago the BW30 was a common membrane for maple. In my experience, they cleaned wll and lasted well. Their major drawback was that they were VERY teperature dependent. On cold sap, 35-40 degrees, 1 NF-70 could do the same as 2 BW 30's (roughly). The NF 70's performance did vary slightly with temp., but not much. If you had hot sap, 60 degrees(roughly), the 2 BW30's would do about 1 3/4 of what 1 NF70 could do.

[DrTimPerkins]

The other key difference between "true" RO machines and nanofiltration machines is the operating pressure. RO machines typically require about double the pressure compared to a nanofiltration machine. This makes the cost and complexity higher in a "true" RO compared to a nanofiltration device. Consequently, most machines used in the maple industry are actually nanofiltration devices rather than actual RO machines.

[lew]

I forgot to mention that you also ran the membranes differently. By that I mean that if you had NF 70 membranes you would run them to a maximum flow rate and not exceed a certain pressure. The BW 30's were run by adjusting your permeate and concentrate flow until the machine was running at 500 psi. You were supposed to keep your concentrate about1/3 of your permeate (if I remember correctly). then you just got a flow rate that the sap temperature would allow.

[Brent]

That information about the temperature sensitivity is something I ran into when I tried the GE Merlin ROs. They worked great, but terribly slowly at sap temperatures.

I did ask one of the major maple vendors who had a stand at the conference, who said that the only one to use is the PVD-1, which of course is sold exclusively through maple equipment OEM's, with multiple mark-ups and the price to prove it.

I think I'll wait to see what ACER puts up on their web site.

My RO will only go to 300 psi so a membrane needing 500 is out of my league.

Thanks for the feedback guys.