Higher Brix RO

[TheNamelessPoet]

So, is the reason that RO's like many homemade and the RO Buckets, that in order to filter more, you need more pressure. The pressure is limited by the materials correct? If you could replace fittings and materials, would the membrane hold up to say 200 PSI? 250?

I ask because I was wondering how to increase the Brix before I start boiling. I mean I know they have units that can get you up to like 35% but I don't have that kind of money or do that much to make any sense.

[DRoseum]

adding a Recirculation loop is the best approach for raising sugar concentration in a small DIY unit. Keep pressure in normal range, keep flow across membranes yet can increase concentration levels.

There are multiple reasons why going too high in pressure with those systems isn't the best option. #1 diaphragm pumps those systems use exponentially decrease flow at higher pressures above a certain point (normally around 100 - 120 psi or so). #2 pressure ratings of membranes and all other components. #3 increase fouling due to higher pressure and low flow (higher recovery rate results in accelerated membrabe fouling)

[eastky]

How much increase in concentration do you get with a recirculation loop.
I have one of the RO bucket Kits with (3) 8GPH membranes.
It doubles the brix now, but I am only starting with about 1.3% sap.
I guess my question is, would I be better with a recirculation loop or just running it through twice.

[maple flats]

In most cases the membrane is not the limiting factor. It's generally the pressure canister, and the tubing/fittings. Most small pumps in the price range homemade RO units have don't attain higher pressures, nor do the canister , tubing nor fittings. That being said, I'm not aware of any pressure vessels that can hold up to much more pressure than the 100-125 psi most run. When running the membrane is in an equalibrium pressure, the inside pressure is pretty only lower slightly below the pressure on the outside.

[DRoseum]

Recirc loop is better than running thru twice if you can start to boil the output right away. It won't sit for as long without boiling, limiting microbial action.

It's really simple, just split the concentrate output afyer the needle valve and tee one of those back to the pump inlet tube. You can use a 2nd needle valve to change how much recirc you get, which will influence final concentration level and the rate of outflow of that concentrate.

[ebliese]

How much increase in concentration do you get with a recirculation loop.
I have one of the RO bucket Kits with (3) 8GPH membranes.
It doubles the brix now, but I am only starting with about 1.3% sap.
I guess my question is, would I be better with a recirculation loop or just running it through twice.

We run the RB25 from the RO Bucket. Carl told us setting the psi at 125 is a good pressure for prolonged runs but you can run it up to 135-140 psi for a couple of hours to get in the 6-8% range. So maybe you could set your psi higher at this point (if you have a gauge).

We usually run our sap through twice, though we are new to the RO game. We boil all our concentrate when we make it so nothing sits around. It might be worth an email to Carl at the RO Bucket to ask about your unit and recirculation.

[jrgagne99]

Recirc loop is better than running thru twice if you can start to boil the output right away. It won't sit for as long without boiling, limiting microbial action.

It's really simple, just split the concentrate output afyer the needle valve and tee one of those back to the pump inlet tube. You can use a 2nd needle valve to change how much recirc you get, which will influence final concentration level and the rate of outflow of that concentrate.

Droseum is right. Poor-man's recirc is the way to go. Just as he described, no need for a 2nd pump. I modified my Waterguy's single-post in this manner about 4 years ago and it was a game changer for me. Now I walk into the sugarhouse and make 6-8% immediately right out of the 200-gal truck tank, feeding it directly to the steam-away to start boiling right away. I don't even use a concentrate tank anymore. No need to run RO for 1-2 hours before boiling.

[TheNamelessPoet]

I have it recirculate back into the tank, and then let it go until it is at 8ish percent.

I had not thought about just having it go back through. Does anyone have any pictures? Droseum, I get the concept, but if I am splitting it off doesnt some of it still come out at the lower %? OR do you have a shutoff for the "lower" concentrate to make it recirculate?

[TheNamelessPoet]

Also... any reason NOT to go from an RB10, to the RB165? I have about 40-50 taps.

[DRoseum]

Not sure of pump size for RB10 vs. 15, but another membrane is a good idea if the pump is big enough to have adequate flow to it and keep your recovery rate of the 3rd membrane sufficiently low.

Cranking up pressure too high is not advisable for reasons stated below. It actually decreases pump flow rate significantly ( which negatively impacts recovery rates and can increase fouling).

Running thru twice is ok, but you have to wait for entire batch to finish to start again before you can get anything to boil.

Recirculating to same tank is common, but isn't optimal either. The concentrate you put back in is reintroducing concentrated bacterial levels and it isn't going to uniformly mix into the sap. You may actually get some density gradients in your tank.

Adding recirc is simple with tee after the needle valve and going back to a tee at the pump inlet. You can add needle valves on either or both the final output line or recirc loop to give you control over how much concentrate is recirculating.

The output is going to assymptotically approach a maximum concentration level that os a function of how much of the outflow is recirculating back to the pump.

I adjust mine to match the boiling rate of my evaporator. Taking 1.3% sap up to 6% and ROing and boiling in parallel is a huge time saver.

See rough sketches to illustrate the concept. 22813
22814

I have video that briefly discusses and shows a recirc loop on a small DIY RO build: https://youtu.be/JIbeiX3a16I

[eastky]

I have the RO 15, and it has a 40gph pump and won't support over the 3 membranes it came with, according to the RO bucket page.
I would like to add a larger pump and 2 more membranes. I would like for my RO to keep up with my evaporator.
Where to buy a bigger pump and which one.

[ebliese]

I have the RO 15, and it has a 40gph pump and won't support over the 3 membranes it came with, according to the RO bucket page.
I would like to add a larger pump and 2 more membranes. I would like for my RO to keep up with my evaporator.
Where to buy a bigger pump and which one.

If you look on the RO Bucket's website, you can look at upgrade kits. A RB15 can be upgraded to an RB25 (five membranes) but you will need the purchase the larger 60gph booster pump. Contact the company and I am sure Carl give you specifics with what you need.

What kind of evaporator are you running? Size? Pan type? Evaporation rate?

[eastky]

Not sure of pump size for RB10 vs. 15, but another membrane is a good idea if the pump is big enough to have adequate flow to it and keep your recovery rate of the 3rd membrane sufficiently low.

Cranking up pressure too high is not advisable for reasons stated below. It actually decreases pump flow rate significantly ( which negatively impacts recovery rates and can increase fouling).

Running thru twice is ok, but you have to wait for entire batch to finish to start again before you can get anything to boil.

Recirculating to same tank is common, but isn't optimal either. The concentrate you put back in is reintroducing concentrated bacterial levels and it isn't going to uniformly mix into the sap. You may actually get some density gradients in your tank.

Adding recirc is simple with tee after the needle valve and going back to a tee at the pump inlet. You can add needle valves on either or both the final output line or recirc loop to give you control over how much concentrate is recirculating.

The output is going to assymptotically approach a maximum concentration level that os a function of how much of the outflow is recirculating back to the pump.

I adjust mine to match the boiling rate of my evaporator. Taking 1.3% sap up to 6% and ROing and boiling in parallel is a huge time saver.

See rough sketches to illustrate the concept. 22813
22814

I have video that briefly discusses and shows a recirc loop on a small DIY RO build: https://youtu.be/JIbeiX3a16I

Thanks for the video, I have the parts to add a recir line coming, after your first needle valve where you set the pressure to around 110, then you split the concentrate line, one leg to the pump intake and the other leg to the concentrate collection tank, do you split the flow of these 2 legs evenly?

[DRoseum]

You basically have 3 options:
1. split it evenly 50/50
2. increase the flow through the recirc line to more than 50/50 with a 2nd needle valve on the outflow line (further increases concentration)
3. Decrease flow thru recirc line with another needle valve on the recirc line (less concentration)

I tried to sketch that in the one image.

[U90025]

First time poster but a long time reader who very much APPRECIATES this platform. I don’t know if we would be making maple syrup without this help. Because of this platform I have built an RO with the aquatec 8800 pump with 4 - 150gpd membrane solutions membranes and absolutely love it, we’re going into the third season using it! I am interested in increasing output concentration by adding the recirculating line but do I need to add a check valve anywhere? Seems to me that the recirc line should have one? Thanks in advance for any replies and all of the help everyone.

[DRoseum]

I put a check valve on the sap intake side of the tee. The other two sides of the tee are the recirc return and the line going to the pump. This prevents back flow into the sap intake.

[MajorWoodchuck]

Seems like a logical upgrade of improving performance on these smaller systems would be to get a smaller vane pump. I picked up a 1/3 hp carbonator pump from a auction that included a soda fountain for $5. This Fluid o tec pump puts out a pretty consistent 2 gpm at all pressures. It looks like you can get a new pump and used motor off eBay for $150. Just a little more than a Aquatec and transformer. I was testing it out on well water and the permeate ran faster on 140 psi than 110 psi. The Membrane Solutions filters i got from eBay said they are good to 200 psi. This pump with recirculation looks like there will always be a lot of flow on the membranes to keep them from fouling at higher pressures.

[U90025]

I will add it this weekend! Good luck on having a great season and thank you for the quick response.

[neil2fish]

i have a medium size DIY w with 3, 4x40 but the physics are the the same. After one year i added a recirc pump when I wrapped my head around the idea that 15% recovery is max. Increase the flow at 15% and you increase the recovery with no additional pressure and therefore minimal fouling if any. if 85% of your flow is going ACROSS your membrane it rinses w sap. OH happy days! I do not valve my recirc. Whatever i don't take out as concentrate recircs. My recirc pump is 600GPH so my max recovery is 4.5gpm 1.5gpm x 3 membranes. I adjust my concentrate valve to achieve that and walk away. Much thanks to the many folks here who gave mw the courage and knowledge to homebuild...!