Using Our RO Most Effectively

[GeneralStark]

We are using a dinosaur of an RO, but it is a workhorse of a machine. It appears as though our flow rates (@450 psi) are 3gpm for concentrate and 6 gpm for permeate. We are about doubling our sugar concentration in one pass. We have potential 700 gallons of permeate storage, and a 450 gallon head tank that is presently set up to pump concentrate to.

In order to use this machine most effectively, I am curious about others' thoughts that may have experience with these older machines. To this point we have been concentrating to the head tank to about 5-6% and then concentrating a second time to about 7-8%(in the tank) and then boiling. This works fine, but when the sap flow is high and we start running out of concentrate and sap storage, we have to stop the machine, which seems ineffective.

I am advocating for concentrating back to the raw sap tanks as soon as we have some sap collected so we can keep the machine running and removing water. Then, concentrate the raw sap tank contents to the head tank and boil.

Also, we have been storing the permeate and using it to rinse and wash, but we have been rinsing as soon as we fill our storage tanks (about 2 hours). I am advocating for only rinsing at the end of the day and once we fill the permeate tanks, just sending the permeate to the drain so we can keep concentrating. It takes a couple hours to rinse the machine, and about 20 minutes to push all the sugar out before rinsing.

Just for reference, there are almost 2000taps feeding this machine and we can boil at about 75-100gph.

Any thoughts or advice would be appreciated.

[maplwrks]

General---I think you have the right idea with regards to recirculating and washing. This is exactly what I do with my RO. I recirc back into the raw sap until my permeate tank is full, then start feeding the feed tank and send the rest of the permeate down the drain. As long as your machine continues to perform well, wait to wash at the end of the day.

[802maple]

Wash at the end of the day, but you should give a 1/2 hour rinse every 4 hours, to keep that axe sharp.

[ennismaple]

General - We took PATheron's advice and will re-circulate back into the raw sap tank for a while, when the boiling time and gathering schedule permits. it allows us to dump water without feeding the evaporator feed tank while we do other things. When doing this we set the permeate and concentrate flow levels about equal - say 5 GPM each.

We have a simple valve system set up that allows the concentrate to either flow back into the sap tank or be directed up to the feed tank. Just make sure to never have both valves closed at the same time! I know someone who did something silly like this (twice!) and a hose on the RO blew up (twice).

[GeneralStark]

Thanks guys. This is helpful. We are still learning what this machine can do, but we'll get there. It seems to me that our primary goal should be to remove as much water as we can from the sap, and not to fill the concentrate tank as quickly as possible.

Rinsing every four hours seems reasonable. Should we do this even of the flow rates don't drop? If we push the sugar to the feed tank and the perm. down the drain after concentrating for four hours, then rinse for 30 minutes, that would only be 45 minutes that we are not concentrating.

Ennis - Why not remove as much water as possible when recirculating back to the raw sap tank? I'm not sure we can set the flow to be equal on both sides with this machine. It looks like the best we can do on the concentrate side is about 3gpm.

[802maple]

Yes, every 4 hours,even if it hasn't dropped off, sooner if it starts dropping off, significantly. Don't let the axe get dull and it will chop more.

Now to answer Ennis' statement, seeing that indirectly i taught him to do this, because I taught Theron this. It is easier on the membrane to run lower pressure and try to move it thru faster, again keeping the axe sharp. It will fail much quicker if you are squeezing it down and thus having to wash or rinse more often because of it dropping off. While it is washing or under producing because of it fouling.you are spinning your wheels.

[Teuchtar]

Late one evening I was running the RO and feeding from a tall 600 gal vertical tank. The RO was drawing off the drain at the tank bottom. The concentrate was trickling back into the same tank. All was dark except my flashlight. Just for gags, I shone the light right through the diameter of that translucent tank. I could see the concentrate drop like a rock from the tank return pipe all the way through the fresh sap to the floor. Seems to me that my RO was not drawing fresh sap, but was needlessly drawing the higher brix sap. This pushes up your osmotic pressure and reduces permeate flow. Nowadays, I draw fresh from one tank, and put all the concentrate into a new tank. Only once that first tank is empty do I draw from the second tank. I convinced myself it was faster and needed less continuously tweaking of the pressure setting to compensate for elevated brix. Let me know what you think. An alternative might be to put the RO feed fitting about 1/3 of the way up off the floor of the first tank, letting the denser concentrate return stay on the bottom.

[wiam]

In a seminar be Karl Lapierre he said if recirculating you should use a floating pick up and return concentrate to bottom of tank

[ennismaple]

Yes, every 4 hours,even if it hasn't dropped off, sooner if it starts dropping off, significantly. Don't let the axe get dull and it will chop more.

Now to answer Ennis' statement, seeing that indirectly i taught him to do this, because I taught Theron this. It is easier on the membrane to run lower pressure and try to move it thru faster, again keeping the axe sharp. It will fail much quicker if you are squeezing it down and thus having to wash or rinse more often because of it dropping off. While it is washing or under producing because of it fouling.you are spinning your wheels.

I agree. If we can run the permeate and concentrate at 5 and 5 on the first pass that means we're getting rid of 300 GPH of water. If we dial the membrane down to 3 concentrate we'll get about 6 permeate, depending on sap temperature - so we're getting rid of only another 60 GPH of water. The membrane performance can drop off quickly when re-circuating so you only need to run the RO another 12 minutes to make up the difference between 300 and 360 GPH permeate.

[MillbrookMaple]

We found that not concentrating to the raw sap was the best approach for us. We draw our sap in on the truck tank (500 gallons) and hook the RO and pump the sap off the truck with the RO into a 265 gallon tote and set the pressure to around 400 psi (500 is max for our unit). We have 4 totes. We alternate the concentrate tank daily and use the remaining ones for permeate. Once we run 2 loads through the RO we hook on to the concentrate tank and run the sap through at around 350 psi and recirculate until we hit our desired % then send it to Head tank. We used to recirculate back to the truck tank until it reached our target but then we always had to keep an eye on the pressure the whole time and calculated that we got the process done a little faster by using the concentrate tank. On the first pass once the sugar level plateaus the pressure will stay constant as long as the membrane doesn't start to get fouled. We rinse our membrane with 500 gallons of permeate every 1500-2000 of raw sap processed and wash and rinse every 3rd time. I don't profess that this is the best way it is just how we do it and works well. Maybe with some variations of all the suggestions you may find what works best for you.
P.S. The reason we run 2 loads initially is to get ahead of the evaporator. We end up boiling through the first load before the second is done otherwise. This allows me to start boiling and not have to stop until we have finished 4 loads.

[briansickler]

Hey General. I too have an osmonics RO made around 1984. I have 4 XLE membranes in it now...room for 4 more. Just for kicks the other night after running for 45 minutes concentrating to 8.5% I squeezed the conc. valve all the way closed. That gave me 450 psi on the guage. Checked the concentrate coming into feed tank and it was 11% in just one pass. I can't believe the performance I am getting out of this old machine. I should add that the sap was 2% even to start with. I would like to see a picture of your RO to see if it is like mine. Thanks.

Brian

[Russell Lampron]

I have a seperate tank for the concentrate. The RO pumps it out of the raw sap tank into the sweet tank. I then recirculate back into the sweet tank once the raw sap tank is empty. This gives me a place for raw sap so that I don't dilute my concentrate when bringing in more raw sap. When I am ready to boil I pinch down the concentrate flow to just faster than my evaporator can boil it and start boiling. I run my RO at 400psi and keep the flow rates even. I also flush out the sugar and rinse the RO after 4 hours of operation and wash at the end of the day.

[JBurkett]

Yes, every 4 hours,even if it hasn't dropped off, sooner if it starts dropping off, significantly. Don't let the axe get dull and it will chop more.

Now to answer Ennis' statement, seeing that indirectly i taught him to do this, because I taught Theron this. It is easier on the membrane to run lower pressure and try to move it thru faster, again keeping the axe sharp. It will fail much quicker if you are squeezing it down and thus having to wash or rinse more often because of it dropping off. While it is washing or under producing because of it fouling.you are spinning your wheels.

By rimse do you mean backflush with cold permeate or is this a hot rinse with permeate on a wash cycle?