Homemade R.O

[icehouse1]

I have been doing a lot of reading lately about making a RO. I need to make one that will process 200 gph of raw sap. I am wondering if two 4x40 membranes are capable with a procon pump. Also, how many gph pump should I get and will a 3/4 motor work?

[bowhunter]

Two 4040 NF membranes such as a Filmtec NF270 or an Axeon NF3 will work, but without much room to spare. Two Filmtec XLE's are probably not enough for this capacity. If you have a low pressure feed pump in addition to the ProCon you could boost the pressure 30-40 psi on the XLE's and squeeze out 200 gallons per hour. With the membranes in series you will need a pump capacity of about 540 gallons/hr to maintain the correct membrane recovery at 15% per membrane. A 540 gallons/hr ProCon pump requires a 2 HP motor. RO membranes are designed for a maximum recovery of 15% to prevent rapid fouling of the membrane. This is also known as a 5:1 ratio of concentrate to permeate out of the membrane. Most of the concentrate coming out of the membrane is recirculated back to the pump inlet to maintain these high flow rates and to keep the recovery down. Hope this helps.

[icehouse1]

Thank you. That helps a lot. I was planning on a shallow well feeder pump, but didn't realize it would be so much work on the XLE's. On good runs I can get almost 1200 gallons of sap. I boil on a wood fired 3x10. So you can see why I need to get going on my building my R.O.

[bowhunter]

To be clear the shallow well pump will help with the system pressure and you can probably make the XLE's work most of the time. The membranes foul and I usually have to do a soap wash about every third day of full running so the performance is slightly different each day after the wash. To compensate for fouling you have to increase the system pressure. I start the first day at about 165 psi and by the last day before the wash I am over 225 psi.

[mellondome]

Thank you. That helps a lot. I was planning on a shallow well feeder pump, but didn't realize it would be so much work on the XLE's. On good runs I can get almost 1200 gallons of sap. I boil on a wood fired 3x10. So you can see why I need to get going on my building my R.O.

What is your concentrate expectation? When you say 200 gal /hr, are you looking for 4% or 8%?

[icehouse1]

I think for now I will be happy to get 4% sap. So I guess my question now is will one procon pump run two xle's set up in parallel process 200 gallons 2% sap to 4% sap in 1 hour?