Iron filter/peroxide before or after softener

[diggity]

Seeking some advice from the good folks on this forum. We have been suffering with high iron ever since we built our house 10 years ago. Our water is pretty lousy: 15-20 ppm or so of iron, 50 grains of hardness, pH of 6.5, manganese is around 3 ppm. Fortunately we don't have any problems with metals, pollutants, or bacteria (although there is a mild amount of iron reducing bacteria).

We have a large Kinetico dual softener for the hardness and iron. I know that softeners are not usually the tool of choice for iron, but to its credit, it knocks down MOST of the iron, bringing it from 15-20 ppm down to probably 1-2 ppm or so. Unfortunately, of course, that is not low enough, and we get staining on fixtures etc.

We're finally going to throw some money at it and re-engineer things a bit. I'm in the process of fixing the pH (we actually have a calcite neutralizer which Kinetico said we didn't need a few years back, so they put it in bypass. Recent tests have shown the pH at around 6.5, so we clearly do need it. So I'm adding more calcite and putting it back in service).

As for the iron filter, I'm leaning toward peroxide injection in front of a filox type filter. I know I could inject chlorine instead, but I'm not a fan of chlorine for several reasons.

So I have a question as to whether the peroxide and filox should go in front of the softener, or after the softener. So in other words:

Acid Neutralizer -> peroxide injection -> contact tank -> filox filter -> catalytic carbon -> softener

-or-

Acid neutralizer -> softener -> peroxide injection -> contact tank -> filox filter -> catalytic carbon

I know typical recommendation is to put iron removal before the softener, but I'm a little worried that if any ferric iron breaks through, it could foul the softener. Any advice appreciated - thanks in advance!

 

[Mikey]

Speaking as a non-pro, I love chlorine. It's cheap, effective, and my wife is comfortable with a disinfectant she understands and trusts (Clorox). Follow the chlorinator with a charcoal filter and then you're good to go into the softener, although Kinetico wouldn't be my choice.

 

[Sponsor]

 

[Reach4]

I know typical recommendation is to put iron removal before the softener, but I'm a little worried that if any ferric iron breaks through, it could foul the softener.

Did that come out the way that you intended?

I expect somebody will have some good recommendations for you.

 

[ditttohead]

You have several issues that make this interesting. Low pH and a softener being used as an iron reduction system can work, but as you may notice, you are using many times more salt than is necessary. The low pH is good if you are using a softener as an iron reduction system. For your application, a staged approach may make more sense. First off, do you have a recent water report? If not, please consider it. It can be very beneficial in designing an effective water treatment system. What is your hardness?

You could simply add a backwashing calcite filter which will reduce the iron considerably, then chase it with a Katalox light backwashing system. This would probably take care of the iron problem without peroxide, but be prepared to ad the peroxide system if this does not clear it up. Shock your well and see if that clears up the iron bacteria for any length of time.

 

[ditttohead]

Did that come out the way that you intended?

I expect somebody will have some good recommendations for you.

Low pH and using a softener for iron reduction allows the resin to be cleaned by the salt with less fouling. High pH and softener/iron = fouling of the resin bed. It is one of the reasons we use acids in the brine tank, to lower the pH, allowing for a more effective cleaning/stripping of the iron from the resin. It is obviously a lot more complex than that, but you get the point.

 

[Bannerman]

you are using many times more salt than is necessary.

The high amount of salt is necessary when the softener is exposed and is required to remove iron, but is not necessary if the iron is being removed by other methods before the softener.

 

[Reach4]

It is one of the reasons we use acids in the brine tank, to lower the pH, allowing for a more effective cleaning/stripping of the iron from the resin.

Sounds like somebody could make a softener that gets low pH water from before the calcite for brine fill.

 

[ditttohead]

Correct, I just saw the 50 GPG hardness.

SO with 20 PPM iron, the system should be set to use 2-3X the normal amount of salt.

 

[diggity]

Did that come out the way that you intended?

I expect somebody will have some good recommendations for you.

LOL, yes, it came out the way I intended, but that doesn't mean it made any sense!

Thanks for all the replies everyone... I had no idea that the softener does better with a low pH. I'm so glad you mentioned this, as I have some calcite on order and was about to refill it and put it back online later this week. Maybe I should hold off on that!

@dittohead, yes, we do have a recent full water report. Can you explain a little more about the backwashing calcite filter with the Katalox chaser? What would be the order? Calcite -> softener -> Katalox? If so, how does that square with what I just learned, about higher pH being bad for the softener?

Thanks again!

 

[Reach4]

I had no idea that the softener does better with a low pH. I'm so glad you mentioned this, as I have some calcite on order and was about to refill it and put it back online later this week. Maybe I should hold off on that!

He was saying that low pH works better during resin cleaning. I don't think that he was saying that the softening operation was better done with low pH. The calcite raises hardness, so the softener needs to be after the calcite.

The use of the low pH raw water during regen or fill might be theoretically advantageous, it is not how real world equipment works as far as I know.

I suggest you consider a fairly comprehensive test on your raw water if you don't have a fairly recent comprehensive test. Kit60 http://www.karlabs.com/watertestkit/ is a good value. The free tests done by a dealer may be expensive in the long run. Your iron number is pretty shocking to me.

 

[ditttohead]

Water with iron and a high pH has a high fouling potential for softener resin. Salt cleaning is usually not adequate with higher pH. Low pH... resin is more likely to be adequately cleaned with just salt, again, it is a lot more complex than this simple statement.

With Calcite raising the pH, the Katalox would go next as it prefers a higher pH for iron reduction. The majority of the iron should now be removed prior to going to the softener last.

Post your water test please.

 

[diggity]

Oh OK - gotcha... so the low pH is helpful for resin cleaning/backwash. Got it. We normally add a little Iron Out to the brine tank. We also use the special salt in the green bags specifically for iron. I also recently heard about Res Care, but have not tried it yet. Maybe these things lower the pH in the brine tank?

So I should proceed as planned and get the calcite filter working again?

Regarding the water test, we did have a paid test done recently, at a local lab:
Coliform: 0
Sodium: 157 mg/L
Potassium: 6.45 mg/L
Copper: ND
Iron: 18 mg/L
Manganese: 5 mg/L
Magnesium: 39 mg/L
Calcium: 252 mg/L
Zinc: 0.16 mg/L
pH: 6.3
Turbidity: 200 NTU
TDS: 1,795 mg/L
Alkalinity: 20 mg/L
Chlorine: ND
Chloride: 426 mg/L
Hardness: 792 mg/L
Nitrate: 4 mg/L
Nitrite: ND
Ammonia: 10 mg/L
Sulfate: 534 mg/L

Thanks again!

 

[Reach4]

Oh OK - gotcha... so the low pH is helpful for resin cleaning/backwash. Got it. We normally add a little Iron Out to the brine tank. We also use the special salt in the green bags specifically for iron. I also recently heard about Res Care, but have not tried it yet. Maybe these things lower the pH in the brine tank?

Iron Out has sulfamic acid" acid. ResCare has phosphoric acid. Green bag Morton's salt pellets have citric acid.

That water test looks pretty challenging.

 

[ByteMe]

Notice the Nitrate of 4 ppm ?!?!?!


Ammonia: 10 mg/LL ?!?!?!?

Ding ding ding ruuba ruuba ruuba

Is that the most problematic water seen here... In like ever?

Is this a good candidate for whole house RO?

 

[ditttohead]

Actually the water is fairly bad, but certainly not the worst. This would be on the bad end of the spectrum, but... whole house RO would not be a bad, nor a good idea. Consider the waste ration, the pressure loss calculations, the energy consumption, the pre-treatment, chemicals, anti-scalants etc.

In my opinion, it would be better to get serious about the pre-treatment to the softener. Start with Katalox Light or calcite/catalox light, or maybe a chlorine/hydrogen peroxide injection and GAC backwashing system... there are many ways to tackle this.

Considering the low pH, I would lean toward calcite backwashing system and a Katalox Light backwash system, maybe with a chlorine regeneration design. You could even get fancy and use a clean water (separate source) backwash.

What is your current system layout? Atmospheric storage or pressurized? Gallons? Etc..

 

[ByteMe]

Separate source as in truck in water?

What about trying another well at greater depth?

 

[diggity]

Is 10 mg/L of ammonia really bad? It says on the test that there is no limit set by the EPA. We do have a reverse osmosis system, but it is only for the kitchen sink. We have indeed considered drilling another well, but of course there is the cost and no guarantee that the new well will be any better (though it seems unlikely to be worse either!).

@Reach4, thanks for the information - I always wondered what was in those products.

@Dittohead, we currently have the following system:
Non-backwashing calcite (not currently used, as mentioned) -> dual Kinetico sand filters -> dual Kinetico softeners
Plus the RO at the sink.
Pressurized system, with a 60 gallon pressure tank.

I *WISH* it was atmospheric storage! I say that because I have noticed that if I draw a bucket of untreated water, then let it sit overnight, all the rust settles to the bottom and the water on the top is clear and tastes good.

Anyway, thanks for your suggestions. They do lead me to a few more questions though:

1) How does a calcite system remove iron? I thought raising the pH just made the conditions more favorable for the formation of ferric iron downstream (in a katalox filter, for instance). But you seem to be saying that a backwashing calcite filter will, by itself, remove some iron. Or am I reading between the lines too much?

2) Something I've always been curious about the katalox/filox, etc. type filters... do they typically filter out ALL of the iron which they oxidize? I guess this gets back to my original concern about not wanting to foul the softener with ferric iron. I'll frame my question as an example... our incoming water has 18 mg/L iron. The Katalox filter is rated to remove, say, 10 mg/L. What happens to the other 8? Does it continue on to the softener as ferrous iron (which wouldn't be so bad), or does it get oxidized but not removed, and so proceed to the softener as fouling globs of rust?

Much appreciated!

 

[ByteMe]

I think the Nitrates and ammonia are indicators of a problem.

Nitrates = "The largest anthropogenic sources are septic tanks, application of nitrogen-rich fertilizers to turfgrass, and agricultural processes."

Ammonia is also a result of the above.

Me, not being an expert (in fact a total rookie), I'd suggest your well needs to be looked at.

Others here are and should have some experienced advice to give.

 

[Bannerman]

Does it continue on to the softener as ferrous iron (which wouldn't be so bad),

The iron in your raw water is clear iron (ferrous) and it is that iron which collects on and can foul the softener resin.

In simple terms, since a softener does not oxidize, any iron removal performed by the softener is achieved by being absorbed or sticking to and coating the resin. Once the resin is saturated with iron, its softening ability is effectively blocked. To maintain softening ability and clean away the iron, higher amounts of salt and more frequent regeneration is required, than would be needed if the iron wasn't present.

As Dittohead mentioned, low pH water is somewhat acidic and will assist the salt to remove the iron from the resin. In higher pH conditions, an acid cleaner is usually necessary.

Once clear iron is oxidized, it will settle-out as a solid (ferric, aka rust) as you observed in your water bucket. The solid iron particles can be simply filtered out.

Most iron filter medias, will typically oxidize the clear iron, and then filter out the solid particles which are then flushed to drain during the backwash cycle.

As a softener also backwashes, any debris and sediment making its way through, will be flushed away during backwash, while at the same time, expanding the space between the resin beads to increase brine contact.

Most iron filter media is somewhat slow to oxidize iron so more media is required to support the flow rate requirements for the household. Depending on the amount of iron and other water conditions, an oxidizer such as air, chlorine or hydrogen peroxide is also used to assist.

K-L provides a reasonable flow rating and doesn't require as much backwash GPM as most other iron media. Filter size is usual dependant on the flow requirements for the household as well as the water system's ability to backwash the filter media volume.

 

[diggity]

Thank you Bannerman. I guess I've learned something today - I always thought it was ferric iron that could clog a softener, not ferrous. I guess I always assumed that because it's the ferric iron which you see sticking to bath and toilet fixtures, so I kind of assumed that it would stick to the resin beads too. So thanks for setting me straight.
I guess that explains the frequent recommendation that salesmen are giving me, which is to always put the iron filter in front of the softener, not after.

Can I ask one more question? You guys are doing a good job steering me toward Katalox Light, but I see several systems that combine peroxide injection with "catalytic carbon." I know what "activated carbon" is, but what is "catalytic carbon?" It sounds pretty similar to activated, which I know removes contaminants by adsorption. Does catalytic carbon do the same thing, or does it do as its name suggests, catalyzing or speeding up the oxidation of ferrous to ferric iron?

Thanks again, you guys rock!