Reverse Osmosis Questions - Do I need prefilters? Impact of hydrogen peroxide?

[Beets]

I have a well water. We remove the sulphur smell and kill the sulphide reducing bacteria (SRB's) by adding hydrogen peroxide. We then filter with Centaur Carbon. It does a pretty good job. We have a 75 Gallon per day RO system (Hydrotech) hooked up downstream of the centaur carbon filter. It takes the TDS from 450 down to 40. The TDS is mostly sodium. Our water is pretty soft. RO filters seem to last forever (+7 years), but the prefilters (sediment and carbon) can plug up fairly quickly and occasionally they get fouled by SRB's who made it through the system (probably fouled by SRB's twice a year, and changing carbon half a dozen times a year due to plugging - sometimes it won't plug for 12 months, but the next time a filter might last only a couple weeks. I don't know what is going on; the pre-sediment filter never seems to plug, but it gets replaced when fouled by SRBs). We started with 5 micron carbon prefilters, but they plugged instantly. We've been using 50 micron (green) carbon filters for +10 years now. They work best.

I've been debating two things:
1) I've been debating running without a carbon filter. If I have any slippage of peroxide past the main carbon filter into the RO system, will that do any damage to the membrane? Will the H2O2 pass through the membrane? Any concerns if it does pass through?
2) Instead of feeding the RO system with water taken after the Centaur Carbon, I've wondered about using water that still has peroxide in it. I'm thinking that might take care of any fouling of the RO system due to SRB's.

Thoughts?

 

[Bannerman]

The most common RO membrane will not tolerate chlorine which is why most RO systems utilize at least 1 carbon cartridge prior to the membrane. Not certain how well an RO membrane will tolerate hydrogen peroxide as it is an oxidizer similar to chlorine.

Does the carbon filter after peroxide injection utilize cartridges? The usual carbon system appropriate for point of entry applications will utilize at minimum, 1.5 cubic feet of carbon media installed in a 10" diameter X 54" or larger media tank equipped with a backwashing control valve.

The recommended flow rate for effective filtration is 1-3 GPM per cubic foot of carbon so a typical 2.5" X 10" carbon filter cartridge contains too little carbon to provide much benefit for a point of entry application.

While hydrogen peroxide is often preferred for oxidizing iron and manganese prior to a large scale backwashing media filter system, as you state there is IRB (iron reducing bacteria), chlorine is the recommended disinfectant for more effective neutralization of the bacteria.

If peroxide or chlorine is injected directly before entering the carbon filter, there will be insufficient time for peroxide/chlorine to remain in contact with the water so as to kill the bacteria prior to the peroxide/chlorine being removed by the carbon media.

Depending on the quantity of iron and bacteria in the raw water, chlorine is often injected prior to a baffled contact tank which will increase the time for the chlorine to kill the bacteria and also oxidize iron and manganese prior to sediment filtration through a media tank containing iron reduction media such as Katalox Light.

The filtered water exiting the sediment filter will then usually flow through a carbon system to remove any residual chlorine and most other chemicals from the water while also improving taste and colour.

 

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[Reach4]

Consider sanitizing your well. It will knock down SRB for at least a while. How long? I don't know, but I think the better you do it, the longer the effect will last.

https://terrylove.com/forums/index....izing-extra-attention-to-4-inch-casing.65845/ is my writeup. It is more intensive than most. Summer is a good time to sanitize. Winter is not.

I would add a sediment filter after your backwashing filter. 4.5 x 20 inch cartridge. I like the PENTEK-DGD-5005-20 cartridge, but there are many other good ones.

 

[Beets]

@Bannerman : Thank you! Peroxide is added at inlet to house. To get retention time, the water and peroxide mixture passes through an extremely large pressure tank (I'm guessing 50 gallons) and a large fiberglass tank (I'm guessing 70 gallons) tank before entering 10 x 54" centaur carbon filter. I am dealing with SRB's (not IRB's). I used chlorine for around 15 years, before switching to peroxide. I prefer the latter. There seem to be less upsets and H2S slippage. I have high pH water (8.5) so that makes chlorine less effective.

@Reach4 : Thank you! I have not shocked my well in over 10 years. I found it cut the H2S smell for a few days, but not weeks. I used a procedure that was half as elaborate as what you provided a link to. I could be wrong, but I have a theory that the SRB's go into slime producing mode when I add chlorine. I've been concerned this might plug off the well. On 2 or 3 occasions I've ran out of chlorine in the house (or purposely ran without because I was adding air to activate the centaur carbon). On those occasions, when I reintroduced chlorine into the system there was a sudden increase in H2S and no amount of back washing could get rid of it. That is backwards to what I expected. When I opened the carbon filter, I found it full of slime. I think I read somewhere that when the SRB's are hit with chlorine, they go into slime producing mode. I'm not sure if that is true, but it lines up with my experience. The carbon had to be replaced. Interestingly, I switched to peroxide the last time my carbon media was fouled. I managed to clean up that media using peroxide - something I was unable to clean up with chlorine.

 

[Reach4]

I have not shocked my well in over 10 years. I found it cut the H2S smell for a few days, but not weeks. I used a procedure that was half as elaborate as what you provided a link to. I could be wrong, but I have a theory that the SRB's go into slime producing mode when I add chlorine. I've been concerned this might plug off the well.

Interesting. On my recirculation path I run the water through a 20x4.5 cartridge that I had taken out of service. I collected a rust-colored thin (1/16 to 1/8 inch) pudding-looking layer. It seems to me that solids I can take out has to be good, but my level of stuff is nowhere close to what I might worry about causing a clog.

What color is your slime?

Did you drop your pH to 5 or lower with vinegar? Maybe next experiment drop the pH first, and then add the bleach. I think I started with bleach.

On your system, if you have a good place to dump plant-killing chlorinated water, you could run your initial water there before switching to recirculation.

Thanks for your comments. For well sanitizing I suspect you could be able to use H2O2, but more of it I expect. I think chlorine is about 5x or so as much a killer vs H2O2... maybe more. H2O2 is itself acidic. I wonder if there would be any merit in adjusting the pH as we do with chlorine. I have not read of anybody using H2O2 for well sanitizing.

 

[Beets]

@Reach4 I don't recall the color of the slime. It was mixed in with the carbon. I did not drop the pH when I did it. That might make a difference. I've only used chlorine for well sanitizing. I haven't tried H2O2. I've got the 35% H2O2 in 130 lb container, so it isn't as convenient/safe as handling chlorine. I will stick to chlorine if I do it again....

 

[Beets]

Just a quick note.....I've been running my RO system without a carbon filter. So far its been working well, and I haven't noted any decline in productivity. I do have a whole house carbon filter upstream. I also left the sediment filter in the RO system. I have been careful to turn off water to the RO system when sanitizing house with Chlorine or Peroxide.