Concentration issues with my RO

[SmellsLikeSyrupNH]

I have a single tower RO with a Procon Series 4 pump. The pump is rated for 115 to 330 gallons per hour at 250 psi.

Over the past few weeks I have gotten about 700 gallons of sap. While processing I can never seem to get an even flow out of the 2 lines. My concentrate hose always seems to be running a lot harder than the permeate line. I know I should be getting them to flow evenly. I took 2% yesterday(using a refractometer to test), 150 gallons, and after 1 pass at 200psi it went to 3%, ran a 2nd pass, again at 200psi and I got it to just over 4%. Ive tried playing up and down with the pressures to make them more even but even then it doesnt seem to be concentrating to much over 4%. So far I have run 700 gallons through it and I get the same results each time. The RO is clean, I rinse every run and then Ive done 2 washes with Lapierre soap. Ive changed out the 5 micron pre filter after every run as well. From my collection tank I use a pump to feed the RO so not over working the Procon pump during the 1st pass. For the 2nd pass, that then feeds to my head tank it pulls straight from the tank which is about 3ft away. Im sure I could just recirculate it until it finally reaches 8% but that seems like a big waste of time adding potentially a few extra hours to each run.

Any ideas? I dont know why im not seeing anything close to 8% after 2 passes. I know its a Dow Filtec 4040 Membrane.

Thanks!

[MapleMark753]

I don't have your RO, but hopefully others do and can specifically respond. That said, it is possible that you are concentrating to your RO's design specs. IF you have the RO listed in your bio info, the makers web site lists 25-30 percents of water (permeate)removed at 180PSI. That would yield a bit less than 3 percent from 2 percent sap. But higher pressure may raise that to what you got or are getting. Also its possible the 8 percent target you mentioned IS possible but only with warmer sap. At about what temp is your incoming sap? Dunno, just my thoughts. If it is from a maple maunufacturer give em a shout on the phone. I'd bet it wouldn't be the first time your questions have been asked.
take care Mark

[maple flats]

What pressure does NextGen suggest you operate at? I suggest you call Steve at Next Gen for hints on getting better performance. Steve knows his units. If you don't have his number, google Next Gen Maple Products.
While his RO's are basic, I think you might be able to get a little better performance, if that's all it is designed to do, Steve will tell you.

[SmellsLikeSyrupNH]

Thanks Dave, I have a note into him. He has always been good at responding, just wanted to see some other thoughts. A friend of mine seems to think that my membrane is bad. Im getting a good amount of permeate out after 2 passes but just think I should be getting higher sugar percentages.

My sap temp is in the 30's when im running it, maybe 40 at the max. We havent had too much warm weather here lately. But its coming!

[bowhunter]

Okay. I looked at the NEXTgen website but I didn't get a lot of detail besides what you posted.

First - I don't think there's anything wrong with your membrane. 25-30% water removal is probably about all you can do with that membrane per pass at 180 psi when it's clean and the sap is not ice cold. Therefore your concentrate flow will be about three times the permeate flow...nothing you can do about that. You probably need 4 passes to get to 8%. You can never get to 8% on two passes if you only remove 25-30% of the water...the math doesn't work. That's probably just a misunderstanding.

Second - Temperature has a big impact on permeation rate. For each degree colder in sap temperature you lose about 3% permeate flow that you can overcome by increasing the unit pressure to maintain the same permeate flow. Many times people see their permeation rate dropping and assume it's fouling of the membrane when it's either an increase in sugar content or lower sap temperature. Check with the manufacturer to see what's the maximum pressure you can operate. I'm pretty sure you can go up to 250 psi. This will increase your permeation rate.

Third - The website said this unit has a pressure bypass..I assume that's on the pump? You probably need to find out what that's set for. That will determine the maximum operating pressure.

You have the basic parts to install concentrate recirculation on the system and get 8% on a single pass. It will process about 65 gallons per hour of sap and produce about 16 gallons per hour of concentrate and about 49 gallons per hour of permeate with an operating pressure around 225 psi. The recovery will be down to about 15% on the membrane which should improve the life between cleaning. I don't like to store concentrate because it has a short shelf life so I match my RO to my evaporator rate and run them both at the same time. It can get a little stressful and many people prefer to RO and boil at different times. It's just personal preference.

[SmellsLikeSyrupNH]

Thanks so much,
Maybe im just over thinking things? This weekend the real runs will start in earnest and I'll see what happens with the warmer temps and also I'll pay more attention to the amount of permeate im actually getting out of the system compared to what I started with.


Okay. I looked at the NEXTgen website but I didn't get a lot of detail besides what you posted.

First - I don't think there's anything wrong with your membrane. 25-30% water removal is probably about all you can do with that membrane per pass at 180 psi when it's clean and the sap is not ice cold. Therefore your concentrate flow will be about three times the permeate flow...nothing you can do about that. You probably need 4 passes to get to 8%. You can never get to 8% on two passes if you only remove 25-30% of the water...the math doesn't work. That's probably just a misunderstanding.

Second - Temperature has a big impact on permeation rate. For each degree colder in sap temperature you lose about 3% permeate flow that you can overcome by increasing the unit pressure to maintain the same permeate flow. Many times people see their permeation rate dropping and assume it's fouling of the membrane when it's either an increase in sugar content or lower sap temperature. Check with the manufacturer to see what's the maximum pressure you can operate. I'm pretty sure you can go up to 250 psi. This will increase your permeation rate.

Third - The website said this unit has a pressure bypass..I assume that's on the pump? You probably need to find out what that's set for. That will determine the maximum operating pressure.

You have the basic parts to install concentrate recirculation on the system and get 8% on a single pass. It will process about 65 gallons per hour of sap and produce about 16 gallons per hour of concentrate and about 49 gallons per hour of permeate with an operating pressure around 225 psi. The recovery will be down to about 15% on the membrane which should improve the life between cleaning. I don't like to store concentrate because it has a short shelf life so I match my RO to my evaporator rate and run them both at the same time. It can get a little stressful and many people prefer to RO and boil at different times. It's just personal preference.

[bowhunter]

You could set up the RO to run in and out of the same tank and let it run until you get to 8%. You could start boiling at maybe 6% and continue to run the RO until you get to 8%+ then shut the RO down while you finish boiling. I think it would probably take you 2-3 hours to get 200 gallons of sap down to 6-8% and then you could start the evaporator. You would only have about 3 - 3 1/2 hours of boiling. If you started with 400 gallons of sap and the same process it would take 10-11 hours total.

[SmellsLikeSyrupNH]

Haha so true, with my evaporator setup now I’m boiling about 40gph so I really need to just be glad it’s going as fast as it is. :-)