recurculating pump

[Wanabe1972]

I just picked up RO that was built for a process we used to do at work. It only has 2 50gpd membranes on it now but was told I could up size this with a xle4040 membrane. It has a 140 gallon per hour pump on it. This should make it about as good as a hobby size. My question is it also has a 100 gpd permeate pump driven by water pressure of the brine. Could I use this to recurculated concentrate from my tank back through the membrane or is it too small to bother with. Thanks jeff

[bowhunter]

The main pump is definitely big enough to feed 25-30 gallon per hour and remove about 75% of the water if it's capable of generating 200 psi of discharge pressure. You could set it up so the main pump also recirculates concentrate back to the pump inlet to keep higher flow through the membrane.

If you follow the membrane manufacturer's recommendations an xle 4040 is too big for your pump, but I know a lot of guys on this forum use a larger membrane with success. The upside to the 4040 is the ability to process more sap when the sap is very cold. An xle 2540 is a better fit for your pump meaning the pump has enough capacity to meet the design flows to keep the membrane from fouling excessively. The only down side to the larger membrane is it may foul quicker and require more frequent cleaning and the larger membrane and housing are more expensive to buy. The permeate pump probably won't generate enough pressure to use for recirculation back through the membrane.

If you think you will expand beyond 200 taps, you definitely should go with the xle 4040 and housing and just see how it runs the first season. You can always add another pump for recirculation later if you have problems with fouling. Procon makes some nice pumps for this kind of application that aren't that expensive.

Good luck!

[Wanabe1972]

My pump is rated at 2.3 gpm at 150 psi is the figure of 25 to 30 gph for total sap through the machine or concentrate?

[bowhunter]

Total sap through the machine or how much sap you can process per hour. Your pump will do about 120 gph. That means you would have about 100 gph recycling back to the pump inlet or suction. At 75% water removal your concentrate flow out would be about 6-8 gph. Permeate flow would be 30 gph minus 8 gph of concentrate or 22 gph. The pump pressure may be a little low to get down to 75% water removal on one pass. You'll have to experiment a little once you get your system running. You may have to pump through the membrane at a higher flow rate and recirculate back to the sap tank until you get out the water you want to remove.

The processing rate I gave you assumes you follow the manufacturer's recommendations on flow. Many people seem to get pretty good results with flow rates substantially less the recommended by the membrane supplier.

[Wanabe1972]

Ok I finally got a chance to look at the RO I picked up and tested each funtion. It has a Cat 230 pump that is rate for 2.3 gpm at 150 psi and the pump can run all the way up to 1200 psi. I have a 5 micro and a submicron filter here and a case of filters for each. It also has a Trojan 702 uv lamp that has a bad bulb. I found the bulb for 100 online but can't find a flow rate for it. It has low pressure and low level shutoffs. I have a jet pummp to feed the pressure pump and due to some research and advice from fellow traders goiing to get a xle2540 membrane and vessel. It has a hour meter and temp readout but not sure where to read the temperature from as of yet. I have a corner that is insulated amd would need a wall and a small heater to keep fromm freezing but will need to keep tanks in unheated area. Is this common practice? I found acrylic flow meters on Ebay today that go from 0 to 5 gpm is that the range I should get? I wll also be buiding a stand because this was hanging on a wall. After I get the stand built I will start to plumb up. I have a drawing so I can use a could of 3 way valves and several 2 ways to use the feed pump feed. Hp pump a head tank as well as feed concentrate back to the hp for recurculation

[bowhunter]

It's pretty common/desirable to keep the sap storage in a cool area. One 0-5 gpm meter would be ok for the flow through the membrane, but the permeate flow is only going to be 0.25 gpm and the concentrate flow to storage or to the evaporator will only be about 0.13 gpm. You will need at least one that is capable of reading these lower flow rates for the concentrate flow. I assume the unit has a needle valve to control the recycle flow. If not you need to get one for that purpose. You will also need a needle valve on the concentrate flow. You adjust the concentrate needle valve to control the flow of concentrate. You adjust the recycle needle valve to control the pressure and therefore control the flow of permeate.