Sulphur smell in RO/DI water

[BradR]

Have used a captive purity RO/DI with the DI removed for 4-5 years. After plumbing the output line into my sink months ago I started noticing a strong sulphur smell from the RO unit for the first hour. I only use the unit 1-2x a week.
Took it apart and the RO and post RO area was covered in black film. Yeck. Cleaned the unit as best I could, bought another RO film from M. Depot and things were fine for a month. Now its back.
Is there any way to clean this without ruining the RO film?
Am I going to be stuck running water thru this every other day for 15 minutes to prevent anerobic activity?
I run the unit post a new culligan water softener which filters our well water (which was fairly hard).
Thanks for any suggestions.

Smelly in Michigan

[Randy Holmes-Farley]

Sounds like H2S or HS- in the water. It will smell and precipitate metal sulfides, which are black. Is it well water?

[BradR]

Yes it is well water. There was trace sulphur in the water and so the culligan man put a filter on in front of the water softener, carbon I think.
What confuses me is this wasn't a problem before and the only part of the ro/di unit that had the black film was the membrane and the areas downstream.
Guess I'm kinda convinced its an anerobic bacteria and was thinking that flushing it every other day might prevent it.
The water smell clears after running the unit for an hour.

[Randy Holmes-Farley]

Hydrogen sulfide gets through an RO membrane easily. It will get caught on the DI, but I'm not sure how to remove it before the RO so that it doesn't foul the RO membrane. Maybe the Culligan guy can help.

Guess I'm kinda convinced its an anerobic bacteria

I suspect it is simply an inorganic reaction, as opposed to bacteria, but you might be right.

[BradR]

Thank you Randy!

[Randy Holmes-Farley]

You're welcome.

Good luck.