Chlorine Dioxide Removal

[jabraben]

Our city uses Chlorine Dioxide for disinfecting the water supply and I have a question about how to remove it. In Martin Brungard's Water Knowledge page, in section 4.1.5, he says the following: "The design of an activated carbon filter system for chlorine compound removal is relatively simple. The residence time for water passing through the carbon media must meet certain minimum durations. For hypochlorite removal, the residence time should be at least 40 seconds. For chloramine removal, the residence time should be at least 6 minutes. Increasing these durations will improve the life of the media and increase the total volume of water that can be treated with the filter unit. (To provide an example of design recommendations for chloramine removal, kidney dialysis machine manufacturers typically recommend an 8-minute residence time for activated carbon, water pretreatment units) The residence time (also known as Empty Bed Contact Time) is calculated by dividing the volume of carbon media (say gallons or liters) by the flow rate (gal/min or L/min)."
He talks about residence time for hypochlorite removal and the residence time for chloramine removal but doesn't address chlorine dioxide directly so I'd like to know what the residence time, in this context, would be for water treated with chlorine dioxide. Anybody help me out?

 

[day_trippr]

The only discussions regarding chlorine dioxide I can recall here on HBT were regarding yeast washing and cleaning up potential bacterial contamination in same. But, with any luck, we might cajole Martin @mabrungard to check out this thread...

Good luck!

 

[505-Brewer]

Its a gas so i imagine if you boiled your water or even let it stand it would degas. They sell test strips you can use to measure it. That would be my starting point.

 

[jabraben]

I've ruled out boiling on account of the time and energy required. I'm doing 1 bbl batches and ~ 55 gallons would take a while and a lot of energy to boil for 20 minutes. I'd rather not have to let it stand on account of the time that takes. I have toyed with the idea of aerating as that is said to speed things along but it seems like a hassle right now.

 

[z-bob]

I would expect sodium thiosulfate or potassium metabisulfite to remove it, just like they do chloramine. Also perhaps vitamin C. But I don't know. Can you test for it? 505' mentioned test strips.

 

[jabraben]

I'm a hard customer. I've also ruled out those options. The only options I would accept are filtering, setting it out a day early, or aerating but filtering would be my preference.

 

[jabraben]

I know it leaves the treatment plant at 3 ppm. I will order some testing strips if a chemist friend confirms that they're reliable.

 

[tracer bullet]

Leaving it a day or two to degas seems easy enough. A consideration on boiling is to do it shortly before mashing, it's above and beyond a strike temp obviously but not terribly far over.

 

[mabrungard]

Although chlorine dioxide is different than chlorine, they both end up producing the hypochlorite ion. Therefore, you can use the treatment recommendations for chlorine when preparing that tap water for brewing use.

 

[VikeMan]

I'm a hard customer. I've also ruled out those options. The only options I would accept are filtering, setting it out a day early, or aerating but filtering would be my preference.

How did you rule out Campden (potassium metabisulfite)?

 

[jabraben]

Although chlorine dioxide is different than chlorine, they both end up producing the hypochlorite ion. Therefore, you can use the treatment recommendations for chlorine when preparing that tap water for brewing use.

Thank you. That is very helpful.

 

[jabraben]

How did you rule out Campden (potassium metabisulfite)?

Partly out of concern over the implications of having sulfites in the beer, though I'm not sure how much weight to give those concerns. Partly because I like the relative ease of using a filter compared to having to dose my water every time I brew.

 

[mabrungard]

If metabisulfite is added at any step prior to boiling, it will NOT result in sulfites being present in the finished beer. Heat breaks down metabisulfite.

 

[VikeMan]

Partly out of concern over the implications of having sulfites in the beer, though I'm not sure how much weight to give those concerns.

If metabisulfite is added at any step prior to boiling, it will NOT result in sulfites being present in the finished beer. Heat breaks down metabisulfite.

So @jabraben, maybe nearly zero weight? I can't confirm this 100%, but I wouldn't bet against @mabrungard too often regarding water chem.

 

[lumpher]

You can run your water, add Campden (or k-meta), and let it sit for 24 hours. After that, you can boil it in the normal process. Filters dont remove chlorine. When you said you're "a hard customer and will only accept those 3 processes", it seems like you had your mind made up already, so do what you have decided to do already.

 

[z-bob]

@mabrungard: (sorry to put you on the spot but you are regarded as an expert) When metabisulfite reacts with chlorine or chlorine-like ions, does it form sulfites or does it oxidize all the way to sulfates? Even people who think they are allergic to sulfites should not have a problem with low levels of sulfates; they are everywhere.

 

[VikeMan]

Filters dont remove chlorine.

They can, but it takes a relatively big carbon block and a relatively slow flow rate. Typical home filters wouldn't be very effective.

 

[mac_1103]

They can, but it takes a relatively big carbon block and a relatively slow flow rate. Typical home filters wouldn't be very effective.

Zero Water filters remove 99% of chlorine. They're designed to have slow flow rates. Even a Brita filter removes 95%.

 

[jabraben]

They can, but it takes a relatively big carbon block and a relatively slow flow rate. Typical home filters wouldn't be very effective.

You can run your water, add Campden (or k-meta), and let it sit for 24 hours. After that, you can boil it in the normal process. Filters dont remove chlorine. When you said you're "a hard customer and will only accept those 3 processes", it seems like you had your mind made up already, so do what you have decided to do already.

I suppose I had but that doesn't stop me from wanting to understand things better.

 

[jabraben]

So @jabraben, maybe nearly zero weight? I can't confirm this 100%, but I wouldn't bet against @mabrungard too often regarding water chem.

Well, now that I've had his response on that issue, no weight indeed.

 

[jabraben]

They can, but it takes a relatively big carbon block and a relatively slow flow rate. Typical home filters wouldn't be very effective.

Thank you. That is very helpful.

Now we've had a recommendation from Ecolab for the "Twin Head" filter kit in this brochure which uses two of the T020 filters. The Ecolab rep referred to it as the twin parallel water system, though it doesn't appear parallel to me. In any case, the specs on the T020 filters themselves claim NSF-42 certification for chlorine reduction at 10 GPM. They don't give carbon media volume so I can't accurately calculate the residence time. I've reached out to the rep to see if I can get that number but I'm curious what @mabrungard thinks about the accuracy of their claims for chlorine removal at 10 GPM given the NSF-42 certification and the size of this filter.