RO operation

[nymapleguy607]

Okay guys I'm looking for some knowledge about how an ro machine works. I understand the concept but im looking for some more details. I'm thinking about building and ro for next season. I would like somethong in the 125gph to 150gph range and my thought is 50% removal for each pass. My thought is a single membrane machine using an XLE 4040 membrane, I'm thinking a procon high pressure pump 250psi. Now this is where I am getting stuck, I see there are various pump outputs for the given pressures. Is it better to use a larger pump say 140gph our should I buy a 250gph pump? Does the membrane have a certain maximum flow amount? Or does the larger pump help reduce fouling the membrane because its moving more GPH? Next thing I haven't figured out is the purpose of the feed pump. Does this just serve the purpose of feeding sap to the high pressure pump or does it help maintain flow rates? Thanks for any info, I'm sure there will be more questions.

[jmayerl]

I started out with your same ambition but ran out of time and my building abilities I think are just to lacking to build one, there fore I bought a 125. I have a new procon in the classifieds if needed. I can tell you that a feed pump could be put in but is not at all nessicary. I believe if you go to dows website it will have the flow rates listed there.

[nymapleguy607]

How big was the pump you purchased, and how big of a motor were you going to use?

[jmayerl]

Procon series 4 240gph. From what I have read and seen a 1 hp would be the right size, some used a 3/4 but it might be right at the minimum size limit.

[bowhunter]

I see a lot of people on the forum using or planning to use Dow's FILMTEC XLE-4040 for homemade ROs. While Dow does recommend this membrane for maple sap they list the NF270 and the NF90 in the 4 inch size before the XLE-4040 because both have higher capacities than the XLE 4040. You don't have to believe me, just read their tech data sheet on FILMTEC elements for maple sap concentration.

If you follow Dow's guidelines for the XLE 4040 you should remove no more than 15-20% as permeate per pass. This means if you want to remove 75 gph of permeate you need to pump at least 5 times that amount through the membrane or about 400 gph. Of course you can probably do less, but there will be greater chance of fouling the membrane. The minimum recommended concentrate flow for the 4040 is about 3-4 gpm or 240 gph. If you decide to use a pump larger than the feed rate you will need a needle valve to recycle the excess concentrate back to the pump suction. If you use a 300 gph Procon pump it does require 20 psi of suction pressure. If you use smaller Procon pumps you only need to keep the suction wet.....make sure the level of the tank is about 12 inches above the pump suction. You can use two smaller Procon pumps in parallel to supply enough flow, but I'm not sure how well this works.

[jmayerl]

FYI my RO from Ray came with the nf270. He said it has better flow rates with this size RO. It also has the needle valve for recirculating

[nymapleguy607]

Interesting, it seems that alot of people are running higher than the 15-20% removal rate with the XLE 4040s. From what reading I have done it seems sugar passing is the main problem with the NF 270s, it seems like the people that started using XLE 4040 had better flow rates and less sugar passing.

[bowhunter]

I think most of this issue is marketing. The membrane manufacturers wanted to make losing a little sugar a big deal to get people to buy the next best thing. Dow will tell you that sugar loss with the NF 270 only occurs with high sugar concentrations..probably over 12-14%. If you're worried about sugar loss, the NF90 has 40% higher capacity than the XLE4040 at the same operating pressure and has about 90% of the mineral retention. The XLE's are sized or rated at 100 psi while the NF's are all rated at 70 psi. That 30 psi makes a huge difference in permeation rates which translate into lower operating pressures and lower electricity costs. The NF 270 works fine in sap concentration particularly if you stay below 15% sugar. If you have 300 taps add another 6-8 taps to compensate for sugar loss.

[nymapleguy607]

Good point, With your ro how big of a membrane are you using and what are you concentrating to?

[TunbridgeDave]

I have 2 xle 4040's in my machine in series. With a procon 240 and a 3/4hp baldor motor running it. There's also a 1/2 hp feed pump. Without recirculation I can about 50% water removal at 200psi and I can process about 200 gph of sap. If I go up to 300 psi I can get about 66% water removal, and with recirc I can go over 75% but the total throughput goes down obviously. The great thing about the xle's is they work great at lower pressures and use less energy and they pass no sugar. The feed pump is important to maintain constant flow through the membrane, especially when the pre-filter starts to get dirty. You don't want to starve the hp pump. Dow states that the maximum flow for the 4040 is 14gpm or 840gph so I wouldn't worry about getting a bigger pump. The 240 mates perfectly with a two membrane system for future expansion. Make sure you call Joe at atlanticro.com for the membranes, vessels and procon pumps.

[Thad Blaisdell]

a couple of points...

I ran the NF 270's for a few seasons and would never go back. Plain and simple. These membranes are great but are a little more finicky on the cleaning. You can only go to a 9 or 9.5 cant remember which. Any higher and you are likely to pass sugars. I have run the XLE's also and have found them to be a really great average membrane. Now for homemade machines I believe they are the cats meow and is exactly what you want. They can go to PH 11 for washing and 12 once in a blue moon. As far as a feed pump I would recommend doing it, small investment and makes sure the vanes don't run out of fluid. Bowhunter had some info on those that sounds right but I don't know.

As far as the membranes only taking out small percentages that I don't agree with. You should in one pass with not much hassle go from 2-6 and second pass to 8-9 easy. I would make the bigger jump first as I believe the more sugar in the sap the harder the water comes out.

[steam maker]

Thadd what do u run for membraines?

[Thad Blaisdell]

I have a 3 post CDL unit as well as a 3 post H20 unit.... I will be running all H20 membranes. They are made for the higher pressure that a commercial unit makes. Now I would also consider the new membranes put out by MES. Maple Expert Solutions. I think they have a really nice membrane as well. But for these smaller homemade machines the XLE is the best bang for the buck.