RO Membrane Preservation

[TexasWine]

One thing I didn't think about when I bought my RO system is how in the world to keep microorganisms from growing in it when I'm not using it. Right now it's just sitting on a shelf in my garage, unconnected but plugged on the inlet and outlets.

I think I need to pull the membrane out and preserve it in something (formaldehyde?). Anybody have an idea of how to go about preserving an RO membrane when it's not in use?

 

[wilserbrewer]

I think I need to pull the membrane out and preserve it in something (formaldehyde?). Anybody have an idea of how to go about preserving an RO membrane when it's not in use?

Formaldehyde???

That is some nasty stuff bro! Very toxic....absolutely no.
I'm not convinced any potential bacterial growth in the RO system is a concern, as it is all pre boil? Water entering, or left in the system is likely chlorinated as well.

 

[TexasWine]

Ha! OK, just so you don't think I'm nuts. Here's where I got the idea.

http://www.watertreatmentguide.com/membrane_condition.htm

And I've seen formaldehyde recommended in other RO documentation as well.

But now I'm trying to figure out if Starsan or Kmeta can be used.

The reason I want to pull keep microbiological growth down is that it stops up the filter and that means it takes even longer to produce the water. It's just a trickle right now and takes a few hours to collect 10 gallons or so.

 

[TexasWine]

In case anyone is interested, I found a research paper from the federal government where they compared RO filter preservatives. According to the paper, a sodium metabisulfite solution of 1-1.5% did the best job.

So, my filter is sitting in a solution of 1 Tbsp Kmeta and 1 quart of water.

I'll have to flush it before using it again, but it sure beats buying a new filter because I let it get stopped up with microbiological slime!

 

[grathan]

Another idea would be buy a 2nd RO setup without a membrane for the house and switch the membrane out when you need to brew.

 

[Buckeye_Hydro]

The textbook answer is to run your RO system at least once a week. If it goes unused longer, pull the membrane and preserve it, and I'd pull the other filters and air dry them as well.

It might just make the most sense to set the system up so that you use it daily for drinking water.

Russ

 

[Buckeye_Hydro]

If you need to preserve it, sodium metabisulfite is a good way to go.

Russ

 

[fuzzy2133]

Another idea would be buy a 2nd RO setup without a membrane for the house and switch the membrane out when you need to brew.

The textbook answer is to run your RO system at least once a week. If it goes unused longer, pull the membrane and preserve it, and I'd pull the other filters and air dry them as well.

It might just make the most sense to set the system up so that you use it daily for drinking water.

Russ

I put our under sink system to use for brewing duty all the time. It just takes a few days to collect all the water since the tank is only 3 gallons.

 

[ajdelange]

As many membranes are shipped with hydrogen peroxide installed I would think that would be good for storage too.

 

[TexasWine]

As many membranes are shipped with hydrogen peroxide installed I would think that would be good for storage too.

Ah, I never thought of that! I'll give it a whirl.

 

[Buckeye_Hydro]

I put our under sink system to use for brewing duty all the time. It just takes a few days to collect all the water since the tank is only 3 gallons.

The "output speed" of your RO system can be changed easily.

The speed at which these systems produce RO water is limited primarily by the gallons per day capacity of the RO membrane. That said, most undersink RO systems designed to make drinking water include very very slow membranes (e.g., 12 gpd). Realize that that by changing the membrane (and installing a new matched flow restrictor) in the same housing you can get up to 150 gpd.

If you have water pressure or water temperature below the membrane specs, the system will make water more slowly. Residential RO membranes are typically spec'ed at 77F, and 50, 60, or 65 psi. We have a calculator accessible on our homepage where you can enter your pressure and your temperature and see how many gpd you should be getting. One of the two common signs of a membrane gone bad is that it produces water more slowly that it should given the feedwater temperature and pressure.

Sending your RO system output to a pressurized storage tank will 1) slow production, and 2) yield RO water with higher TDS.

Russ

 

[BigDog007]

I work with commercial grade UF/RO systems and we definitely soak the RO membranes in a sanitizer solution between run cycles to prevent microbial growth. We use Koch chemicals for this, however, I do not know of an equivalent product that is sold on the retail market. This of course ensures a clean membrane stays free of growth and if you don't clean it first there isn't a lot that is going to save you. I've seen some pretty nasty things growing on membranes when they haven't been cleaned properly.

 

[ajdelange]

Hydrogen peroxide should work and is recommended by Dow (0.25% solution) for their Filmtec membranes for example. Note that drugstore H2O2 is usually 3%. The one caveat is to be sure there is no iron deposited on the membrane as this catalyzes violent decomposition of peroxide with, apparently, negative effect on the membrane.