Proper Rinse and Wash flows for Membranes....

[wmick]

Hi Folks.... I've been reading about rinsing and washing... and I think I have a pretty good handle on following the manufacturers specs on PH levels and Temperature Limits... but what I'm really weak on, is how you actually flow your rinse and wash through the membranes.... I'm trying to make sure I have the valving in place on my Home-Built RO in order to to do proper membrane maintenance...

Couple questions...

Are you looking to send equal volumes through the Permeate and Concentrate sides? or should one get more rinse/wash than the other?
Do you flow in the same direction as processing..... or does anyone do a reverse flow rinse or wash through the membranes?

Thanks

[maple flats]

Same direction as when concentrating. Start with as close as you can to 50/50. Then as the membranes get cleaned, you adjust the pressure to try to stay at 50/50. Check you membrane manufacturer to know the max temperature. Mine are 113F, others are different.
I start at 110-113, but then I send the permeate component thru my tankless water heater before it returns to the wash tank since it cools very quickly until the membrane canister contents get up to temperature. Once back up to 110-113 it might not need further heating.
No reverse flow wash or rinse.

[wmick]

Same direction as when concentrating. Start with as close as you can to 50/50. Then as the membranes get cleaned, you adjust the pressure to try to stay at 50/50. Check you membrane manufacturer to know the max temperature. Mine are 113F, others are different.
I start at 110-113, but then I send the permeate component thru my tankless water heater before it returns to the wash tank since it cools very quickly until the membrane canister contents get up to temperature. Once back up to 110-113 it might not need further heating.
No reverse flow wash or rinse.

Thanks - I appreciate it..

[RedMapleCreek]

I have an RO Bucket with three 400 gpd membranes and the instructions are to flush it with permeate with the needle valve wide open. This keeps a strong flow along the surface of the membranes which flushes them off. If you try to achieve a 50/50 flow you will not flush the surface of the membrane nearly as well since you will be forcing more water thru the membrane instead along its surface. If your home built RO is this type with the small 100 to 400 gpd membranes then you should probably be following the RO Bucket flushing procedure. Flushing a large commercial maple processing RO could be different since that is what Maple Flats is likely referring to.

[therealtreehugger]

Good morning - just got an RO bucket 15 kit, not thinking about rinsing it when I ordered it. However, if all it takes to rinse it is to run the permeate through it and have the valve wide open so there is no pressure through the membranes, just across the membranes, that sounds easy enough. How long should I run the permeate through it for? Is there anything else I am missing or need to know?
Thanks!

[n8hutch]

When I rinse my R.O. I rinse with both valves wide open, that's what the directions say so that's how I do it. When I start out rinsing I get more concentrate flow than permeate but once the unit has had 200 gallons or more through it they flow even.

[tgormley358]

Like some others perhaps on this thread, I seem to be missing some of how Rinse is supposed to work with different valves open or closed or in between. I’m wondering if it’s terminology That's confusing me so I’m going to use my own from the manufacturer. I realize not all ROs are made the same way, but I’m hoping you can shed some light on my questions.

I used my small Single membrane RO, 50 GPH water removal, for the first time last year and it worked well. Mine has an inlet valve receiving filtered sap from my feeder. Closing it sends sap to the pressure pump, which concentrates the sap if I turn that pump on and close down the exit valve. When I rinse, I think last year I left both valves wide open as another poster said they do. I think this will flow permeate in two paths, one is thru the pressure pump, which then flows to one part of the membrane, and 2nd to another part of the membrane. Which one of these two is the main target for cleaning? If I were to close the inlet valve during rinse, then only the first of those two paths will get rinsed.

When I rinsed to start the season last week, virtually all the exiting water exited the concentrate hose, almost nothing from the permeate hose. Does that mean I’m finding then appropriate part of the membrane?

Tom

[bowhunter]

You have the concept right. Using permeate to rinse through the membrane allows a lot of the stuff....minerals and high molecular weight sugars to dissolve back into the rinse thus cleaning the membrane media. Warm permeate will work better than cold permeate but you have to be really careful and keep the temperature below 110 F. Higher temperatures can damage the membrane. You don't want a lot of pressure but I would definitely use enough pressure to get some permeate out of the membrane. If you can measure the flow one good way to know how long to rinse is to watch the permeation rate at a given pressure say 50-100 psi. As the membrane cleans up the rate of permeate production increases for a given pressure. Once the permeation rate stops increasing you've probably done about as much as you can with the rinse. As an example on my membrane the permeation rate will be about 0.3 gpm at 100 psi at the beginning of the rinse. About 20 minutes later it will be up to 0.5 gpm at 100 psi. From there it usually doesn't improve much. I generally rinse for about an hour to get my membrane as clean as I can and to put off soap washing for as long as possible.