Recirc flow

[Bricklayer]

If I run my RO at say 1gpm of permeate to 1 gpm of concentrate but recirc 4 gpm of recirc am I technically running 5-1. My recirc is just teed off the membrane concentrate outlet to a needle valve then flow meter then teed into hp pump intake.

[Urban Sugarmaker]

Bowhunter on this forum is the guy to ask about this. He will probably respond but maybe try PMing him.

[Chasefamily]

If I run my RO at say 1gpm of permeate to 1 gpm of concentrate but recirc 4 gpm of recirc am I technically running 5-1. My recirc is just teed off the membrane concentrate outlet to a needle valve then flow meter then teed into hp pump intake.

Yes I would say that is 5 to 1 has u have 5gpm coming out of the membrane to 1 gal of permeate. That 4gpm doesn't have any problems recirculating without a pump?

[Bricklayer]

If I open the recirc needle valve I can get more then 4gpm if need be.
By running at 1 gpm permeate to 1 concentrate and recircing 4gpm is this good for the membrane. I know most membranes need at least 5-6 gpm concentrate to 1 permeate to keep good flow across membrane. But by having much more concentrate going over them membrane and only 1 gpm of fresh sap. Does this make the membrane foul easier or keep it clean?

[bowhunter]

The higher recirculation rates normally keep the membrane from fouling as quickly.

[Bricklayer]

Ok. Haven't tried it with sap yet only water but it seems to work well. I'm planning on switching the recirc line to a 1/2" ID. All I had when I built it was 1/2 OD tubing. It's the only connection I used a compression fitting on so it bugs me anyways. So by going with a larger ID I should be able to get even more flow in the recirc. I would like to concentrate as high as possible in one pass without having to run multiple passes. The inlet on my high pressure multi stage pump is 1 1/2" so the pump can handle the recirc no problem.

[chrisnjake9]

has any one have any pictures of there home built ro with a recirculation pump installed iv been wanting to add one just not sure how to t it in

[nymapleguy607]

If I run my RO at say 1gpm of permeate to 1 gpm of concentrate but recirc 4 gpm of recirc am I technically running 5-1. My recirc is just teed off the membrane concentrate outlet to a needle valve then flow meter then teed into hp pump intake.

I'm not sure if I am reading your post correctly so apologies if I am interpreting this wrong. If you are running the concentrate and the permiate flow the same you are removing 50% of the water, the additional 4GPM you are recirculating is just helping to keep the membrane from fouling.

[Bricklayer]

Is there a limit on how much you can recirc on a 4" membrane? I would assume after a certain amount your just making it foul faster. I think the max flow in specs for my my membrane concentrate flow is 14 gpm. If one was able to get say 10 gpm recirc and 4 gpm concentrate flow is that ok for the membrane. It would mean higher concentration coming out but also higher concentration going into the membrane. I'm planning on only doing one pass with my RO so I just want to maximize the concentration but at same time not foul the membrane to fast.

[bowhunter]

Generally for a 4 inch membrane the maximum feed flow is 14-16 gpm. This limit is set to prevent mechanical damage to the membrane due to high velocities through the membrane. If your maximum feed rate is 14 gpm then running 10 gpm of recirculation with 4 gpm of concentrate will exceed the recommended maximum feed because you also have to account for the permeate flow. The feed rate is the concentrate plus the recirculation plus the permeate flow. Hope this helps.