Permeate & Concentrate Ratios

[Gary in NH]

I'm in the process of building a small RO system and had a question about the ratios of permeate (water) to concentrate (sap) that you get through a typical RO for syrup production. I will be using a Filmtec tap water RO membrane @ 250 psi feed. If you start off with 2% or 2.5% sugar content in the sap what is after the RO for the same ratios?

Thanks in advance,

[HanginAround]

My uncle runs his concentrate at about 8% sugar, I've heard you should only go to about 10%, but I've heard of some people going higher than that too.

At 8%, I think about 4:10 gpm concentrate to permiate is about right.

You could probably do the math with the 86 rule.

At 2%, 43 gl
At 8% 10.75 gl
So you removed 32.25 gl of permiate for your 10.75 gl of concentrate.

10.75:32.25 = 1:3

At 2.5%, 34.4
At 10 %, 8.6
Permiate = 25.8

8.6:25.8 = 1:3

Not sure if that's what you want or not... there must be an easier way, or better way. Someone will tell me I'm out to lunch LOL.

[Mike]

Im going to run mine at 5-6 % till I get used to the draw off.....In the last issue of the maple news some guys run it at 23%...............

[maplwrks]

Thats Me!! The best I can do is 12% in one pass. It takes a couple trips through to get it that high.

[Gary in NH]

Thanks for the responses. If I understand correctly you run the concentrate through the RO a second time?

[HanginAround]

You don't normally, you just adjust your valves until you get the desired concentration.

[Breezy Lane Sugarworks]

But you can get higher concentration when recircing the sap.