YouTube Channel Reverse Osmosis Series

Forest Farming July 28, 2014 Print Friendly and PDF

Reverse osmosis is a process that forces a solution with solvent, in this case sugar, through a membrane using a great amount of pressure. The membrane is constructed from a sheet polymer which allows water molecules to pass through while keeping the sugar molecules behind. This effectively removes much of the water from the sap and reduces the amount of boiling time and energy needed to make syrup. Steve Childs, Cornell University's Maple Specialist explains the process of reverse osmosis and the benefits this system provides to both the large-scale producer and the backyard producer alike. By running sap through a reverse osmosis system repeatedly, the sugar eventually becomes more and more concentrated, greatly reducing time in syrup production. The concentrated sap still needs to be boiled towards the end as much of the maple flavor is enhanced during the boiling process.

Cornell University's Maple Specialist, Steve Childs, reviews a water purification unit which can be used as a small-scale reverse osmosis unit for the back yard maple producer. The unit reviewed generally comes with a carbon filter which should be removed, as a carbon filter will absorb the sugar from the sap and will quickly become saturated. Two reverse osmosis membranes outfitted with what appears to be a plastic bags, and should not be removed, are in the other two chambers. The third chamber, which housed the carbon filter will remain empty. This unit operates off of a standard shallow-well pump, which means that it can only remove about half of the water content. However this is still valuable for the back yard maple producer. Steve demonstrates how to connect the shallow-well pump to a 5 micron water filter and then finally to the reverse osmosis unit. He explains the importance of the valves and reviews each component of this small-scale RO system. 

Cornell University's Maple Specialist, Steve Childs reviews a second reverse osmosis system for a small-scale maple syrup producer. Reverse osmosis greatly reduces the time and energy spent in boiling maple syrup by pulling much of the water from the sap before the boiling process begins. This unit uses a shallow-well pump outfitted with a shut-off valve to maintain prime. From there, the sap goes through a water filter to remove any bark, insects and bacteria that can sometimes make their way into the sap. From there, the filtered sap continues on at about 200 PSI to the three different 21-inch-long membranes of this particular unit. The sap concentrates as it passes through the membrane, sending the purified water out of the top of the membrane and the concentrated sap through the second fitting of the membrane. Sap can be put through the system repeatedly and becomes more concentrated with each pass through the RO membrane. Boiling the concentrated sap at the end is always necessary however, as that greatly contributes to maple syrup's rich flavor. Steve Childs demonstrates the various steps of this system, removes one of the reverse osmosis membranes and illustrates the proper care for the unit. 

Cornell University's Maple Specialist, Steve Childs, reviews one more reverse osmosis unit that is still applicable to the small-scale maple producer, despite this unit's size. This unit uses a shallow-well pump, suction lines with a foot valve, and 5 micron water filter just as the other two options use. After the sap goes through the water, it continues to a high-pressure pump that operates at about 300 PSI. From there, the sap runs through a high-pressure line to the RO unit. This unit is a commercial size membrane that no longer runs at its full capacity. A small producer can purchase these discarded commercial units and still get adequate use out of it. Steve removes the membrane from the unit and demonstrates how to lubricate the O-rings on the unit. This is critical for maintaining the seal. After running sap through the membrane several times until it's concentrated, the unit should be cleaned by running the remaining purified water through it until the sugar content, measured by the refractometer, is less than 2 percent.

Cornell University's Maple Specialist, Steve Childs, demonstrates how to use a reverse osmosis system. Reverse osmosis uses pressure to force a liquid, in this case maple sap, over a membrane. The membrane allows water molecules through, but forces the sugar molecules to pass over it, essentially reducing the amount of water in the sap with each pass of the liquid through the system. A reverse osmosis unit can greatly reduce the amount of time and energy needed in producing maple syrup. After the sap has sufficiently reduced, the unit should be cleaned by passing the clean water that was removed from the sap, back through the membranes. By using a refractometer, the remaining sugar content in the system can be determined and eliminated with more clean water passing through the membrane.

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