Cleaning small RO membranes in homemade unit

[82cabby]

Hi all,
I have read everything I could find on cleaning and storing RO membranes but it all seems to apply to large, expensive setups. I have the typical home built RO with 4 Axeon 150 gpd membranes. I have rinsed with permeate but last year I lost all four to spoilage in storage when I thought they were clean. I have about $150 in these membranes and that's a lot for me to lose.

Any hints on cleaning and storing small membranes?

Thanks
Dave

[hodorskib]

I was just talking to SDdave about this:
Change your water filter
1. Run permeate through for about 20 minutes
2. Open the housings and dump out any liquid in the top
3. Mix up 4 quarts of hydrogen peroxide and 4 gallons of water water
4. Run the system for 45min to 1 hour but put your permeate and concentrate lines back in your feed bucket - this will allow everything to recirculate
5. Shut system off for 20 minutes and change your water filter
6. Run permeate/water through for 20-30 minutes
7. Disconnect your housings (this will allow you to remove the membranes easier) and remove your membranes
8. Wrap them in two layers of plastic wrap and put in a zip lock bag - store in the bottom of your refrigerator
9. Soak your housings, water filter housing and needle valve in a bucket of peroxide and water (same solution as above) over night
10. Scrub the housings with a bottle brush rinse everything and allow to dry
11. Coat the O rings on the housings with some silicone designed for that so they won't dry out

At the start of next season repeat this process with the cleaning and you will be back in business.

[mellondome]

Most people use sodium hydroxide to wash their membranes with. And you want to use water @ the max temp and ph the manufacture allows for the membrane.
Hydrogen peroxide will kill bacteria... but not clean the organic residue from the membrane surface.

[hodorskib]

I was always nervous about using it on residential membranes so stuck with hydrogen peroxide - if you have done this and are willing to share how you mixed it up I would be very interested.

[82cabby]

I know hydrogen peroxide is available in different strengths. 3% is the standard stuff my drugstore has. Is that appropriate? As for sodium hydroxide, that is basically lye right? What strength would I mix up for that?

The cleaner on the company's web site shows sodium hydroxide on its SDS but I can not determine the concentration. The smallest container they sell is 4.5 pounds and $80. That's 50% of the cost of new membranes for me, so I would like to avoid that!

Thanks for the help I truly appreciate it

[hodorskib]

for the hydrogen peroxide yes I have used 2 and 3% from the drugstore both worked fine

[mellondome]

Washing is not done by concentration.... but rather by ph. There is no "ratio". Find your manufacturer specs for your membrane. It will list max ph allowable and max ph for short time. Put permeate in your "wash tank" and add sodium hydroxide until the ph is that of the short time max allowed for the membrane. Heat to the max temp listed by the manufacturer and recirculate it through the membranes for a few hours. Be sure to check the ph again during the process because as it cleans the ph will drop. You will need to add more sodium hydroxide to bring ph back up. You will want to follow this with a rinse with permeate.

Some of the maple manufacturers have ro soap (sodium hydroxide ) that is buffered so that it doesnt exceed most membranes used in maple's max ph. With this you could take a 5 gallon bucket of heated permeate, add quarter cup of ro soap, and recirculate without having to monitor or check the ph.