How much water

[maplerookie]

All right guys and ladies..I am a little confused about how this reverse osmosis thing works..Dont you need a good supply of water constantly running through the system to draw off the water in the sap. if so I would never be able to do this as I am on a limited well. If somebody could explain the basics in laymans terms as I am not an engineer I would appreciate it. Thanks in advance!

[wiam]

You do not need a constant supply. You only need a source of water for the first wash/rinse of the season. Most commercial will take out 3/4 of the water in the sap each pass. This water known as permeate needs to be saved for washing/rinsing your membranes.

[Scribner's Mountain Maple]

I can answer with my limited understanding. I am a raw sap killer. RO next year for me. Maybe..

NO NEED FOR WATER SUPPLY. That much I can tell you for sure. The RO will create a water supply with each use.

The RO is pretty simple really. Raw sap passes into one end, goes into a special filter/membrane and that membrane only allows pure water through (permeate). Everything else (concentrate) is not allowed through the filter and is sent out another way.

When you are done you will have two tanks. One with pure water (permeate) and the other with condensed sap (concentrate).

Some people recirculate the concentrate and run it through again to take even more water out.

Hope this helps, I am sure the experts will chim in with more technical information.

Ben

[maple flats]

No, you don't need water to run an RO. However you do need to haul enough potable water to clean the membrane before th season. You will need up to the hourly rating in fresh water. I.E., if you get a 250 GPH RO, you could need 250 gal to clean it for use.
Then during the season, you need a tank for permeate (the water that has been removed from the sap), thus again, if a 250 GPH RO, you should have a 500 gal tank). Then in operation the RO draws sap in, removes a lot of water (permeate), I generally remove 75%, the concentrate goes to your head tank to feed the evaporator and the permeate goes to the permeate tank. When you are finished concentrating sap, you use the permeate to clean the membrane.
After you use an RO a day or 2 you will never want to boil straight sap again, and you will ask yourself why you waited so long to get the RO.
I then often run a second pass in the RO. My first pass takes 2% sap to 8% concentrate, then when I run a second pass, I reduce the pressure slightly and remove about half the remaining water to end up with 12% concentrate, and at times I've gone to 14-15% but not normally. To adjust the amount of water removed you just watch the flow meters and turn 1 valve, higher pressure, more water removed, lower pressure, less removed.

[Drew Pond Maple]

I'm also interested in getting a small RO next year.
So if one had 400 gallons of raw sap and ran it through an RO that took 75% of the water out, would you have 100 gallons of concentrate?
Also do you get more niter build up in the pans?

[heus]

Dave what was your beginning of the season wash/rinse when your ro was brand new?

[maple flats]

My owner's manual had me run 300 gal of fresh potable water thru my 250. It said to run 150 gal per 4" membrane, I have 2 membranes. The discharge went down the drain. My RO was then ready to run. During the wash, I set the valves for the highest flow possible. This could have likely been done with about 150-175 gallons because the permeate is returned to the source tank (after the first 5 minutes), only the "concentrate" is down the drain.

[heus]

Highest flow possible means valves backed all the way out, right? Sorry for hijacking your thread Bill.

[SWEETER CREATIONS]

Drew Pond you are correct 100 gallons and yes you still have niter.

[DrTimPerkins]

If somebody could explain the basics in laymans terms...

If you mean the physical reason the process works rather than the operational aspects....

Take a container of water. Divide it in half by putting a semi-permeable membrane in the middle. This membrane has microscopic pores within a matrix that will allow water to readily pass through, but anything dissolved in the water (like sugar or minerals) is too big to get through the holes. Now if you poured a bag of sugar on one side of the container, it couldn't get through the membrane to the other side. However the "energy" level of the water on the side with the sugar is lower than the side without the sugar (the water and the sugar bind together, which lowers the chemical bonding "energy" of the water on the side with the sugar). To even out the energy (and we can think of the energy in pressure terms), some water will naturally move to the side with the sugar in it to balance the pressures. Water will keep moving over until the "energy" or pressure is the same on both sides, which means there will be more water on the side with the sugar and less on the side without the sugar. This natural movement of water through a membrane to balance the pressure is called "osmosis." Now what we as sugarmakers really want to do is not dilute the sugar water by allowing osmosis to happen, but rather to make the sap more concentrated by getting the water out. To do that, we make the container on the side with the sugar into a pressure vessel and put a pump in there to build up pressure in the chamber. Now the sugar water on that side has too much energy (or pressure), so water gets pushed back out through the membrane to the other side, but the sugar can't go through, so it stays in the side with the pressure. The more we put pressure on it, the move concentrated the sugar side gets as water is pushed out. So what we are doing is "reversing" the direction of the natural osmotic flow, or producing "reverse osmosis" by applying pressure.

At the risk of complicating things, what most maple ROs do is NOT true reverse osmosis. Most of them are actually ultrafiltration units. That is simpler. Again you have a filter (which is called a membrane, but is actually a filter unit) that will allow water through, but not sugar. Rather than actually passing through the membrane matrix, the water actually passes through extremely fine holes, which is more like what people think of when you filter something. Because the holes are so tiny, it takes a lot of pressure to push the water through.

[maplerookie]

Ok . I think I get the picture now... thanks to all the input from you folks. one day I may go that way.. but as I am only a hobby guy at this point I will just do it the old fashioned way and boil the heck out of 50 gallons of sap to get my gallon of syrup.. Besjdes my wife would not like the hit on the budget at this time...gonna retire in a couple of years, then I may go balls to the wall with this ! Thanks again guys.