Membrane Rinse During Long Concentration Cycle

[Amber Gold]

What's the proper way to rinse the membranes during a long concentration cycle? So far I haven't concentrated long enough to worry about it. To date all I've done is at the end of the night when I run out of sap is open the permeate valve, and run the HP pump to flush the sugar out of the membranes until it reads ~0% sugar, then I shut it down and put the wash cycle to it, then a final rinse with the remaining permeate.

During a long cycle, should I put the RO to the wash settings after the sugar's rinsed out, and wash it with straight permeate?

Thanks

[Thad Blaisdell]

you need to do the first rinse longer. After sugar is out I do another 15 minutes... your machine being smaller may take less.

[Brent]

Thad raises something that no instruction set that I've seen included. When you shut down to do a rinse you have good stuff in the filter and the membranes ie concentrated sugars. If you are not doing it you will be surprised how long it takes for the concentrate, which will likely be up near 8% ... to get flushed down to 0.5%. In my rig it is something near 10 or 15 minutes. So the question is what to do with this. I've decided that I should start the rinse back into a tank with raw sap. Monitor the concentrate percent until it gets near zero, and then dump to waste, the next 10 minutes or so. Same thing before I start a wash.

Maybe some members with more experience could add to this. It would be great if one of the RO manufacturers wrote a real proceedure manual.

[Russell Lampron]

When I do a rinse I first flush the machine so that there is no trace of sugar in the concentrate. I normally don't time it but it takes longer than the 5 minutes that my manual says it does. I then change everything over to wash settings and run 50 to 100 gallons of permeate through the machine. I then swap everything back to concentration settings and continue concentrating. I do this every 3 to 4 hours and do a soap wash after 10 hours.

[Brent]

Russ
when you flush to clear the sugar, I assume you save the flush and re-process it after the cleanup.

[Russell Lampron]

Yeah Brent when I flush out the sugar it goes back into my bulk tank when I am recirculating or the feed tank for the evaporator if I am finishing up for the night. The amount of permeate that gets mixed back in doesn't make much of a difference when the concentrate is in the teens.

[Amber Gold]

Thanks Russ. I know we had talked about it, but I couldn't remember what it was.

[danno]

I've got a question about wash/rinse. The DOW manual says wash with almost no permeate output, so I've been washing just using my feed pump, not my high pressure pump because if I turn on my high pressure pump, I'm getting permeate, even if I turn the pressure way down and concentrate output way up.

I did not see in the manual where it tells you how to rinse. Are you guys pushing your rinse through the permeate side, as well as concentrate side during the rinse? And, if so, what's your ratio of permeate to concentrate during your rinse, or does it even matter?

[PATheron]

Danno- My modern cdl machine washes and rinses with only the feed pump on. No high pressure pump on. The recirc pumps do work within the towers but anyway when you wash you just use the low pressure pump and then to rinse I just feed the perm through it and out the drain on the wash tank. My older seprotech machine is designed to wash with the low pressure, High pressure and the recirc pump all on while it washes and also to rinse it. The were kind of designed to be washed differently. Hope this helps. Theron