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Thread: What and how much will adsorb onto activated carbon??

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    What and how much will adsorb onto activated carbon??

    This is my first post on TFPs, so I want to thank all of you for making this a great site.

    A few patents call out the use of activated carbon to adsorb cyanuric acid (CYA) from pool water. I think this is expensive, but might still be useful to take out small amounts of CYA and at least delay/defer a drain and refill of the pool. A concern/question that I have is whether or not there are significant amounts of other substances in pool water that may also adsorb onto activated carbon that might make this method inefficient. Some of the threads on this forum refer to TOCs, for instance, and refer to some of the levels of TOCs in pool water. I assume that some to the typical TOCs might adsorb. Or, are there ways to get rid of many of the TOCs before using activated carbon to remove CYA? Any comments on this would be appreciated.

    del

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    Re: What and how much will adsorb onto activated carbon??

    Del, Welcome to the forum. Thank you for your thoughtful donation.

    Do you know if any of these have gone beyond the patent stage?

    I do not know of a product that acts in the manner you describe.

    I am not sure what you mean "by take out small amounts of CYA" To regain control of a pool and reduce CYA to usable levels often involves removing 10 lbs or more of CYA.
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    Re: What and how much will adsorb onto activated carbon??

    What about Reverse Osmosis, Del? Its like dialysis for water and can lower CYA and some other elements, but it might cost as much as a drain/refill there in CA with all the water restrictions.
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    Re: What and how much will adsorb onto activated carbon??

    Del,

    Let me also say thank you, and sorry you weren't answered before now. Don't know how we missed it, but please know it was only in error.

    It seems I recall someone last summer mentioning a system or method designed for Cya removal with Activated Charcoal, but I don't remember much beyond that. I haven't a clue where it is now, but I know the thread is here somewhere. Sorry I'm not of more help either, but I'm interested in knowing more.
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    Re: What and how much will adsorb onto activated carbon??

    Welcome to TFP!

    As Dave mentioned most folks needing to lower their CYA would need to remove about 5-15 lbs of CYA from their pool to get it back to manageable levels. For example, in a 15k gallon pool to reduce CYA level by 50 ppm would require removing 6-1/4 lbs of CYA. It doesn't seem like activated carbon could adsorb that much. Or if it could it seems like you would need a lot of activated carbon. It's a pretty interesting idea though, especially in areas of drought.
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    Re: What and how much will adsorb onto activated carbon??

    The patent reference I saw was application US20140076814. They reference coconut shell carbon and state that 1/2 pound can take out 20 PPM of CYA from 2000 gallons. My pool is about 26,000 gallons, so I might need 6 pounds or so. However, I know that activated carbon can take out all sorts of things, and may not get to be used exclusively for CYA removal, if there are a lot more organic carbon substances in the water besides CYA. I live in San Diego, and city water is very expensive, and some say it is also scarce. The local pool store suggests draining and filling when CYA is over 100 PPM (maybe too ambitious). if 5 or 6 lbs of carbon allows one to delay a drain and refill, that might be a good deal.

    I am aware of the RO service companies and am impressed by them. I am told that there is a multi-month backlog on this service right now, however.

    I did a quick experiment and took some of my pool water and swirled it in some activated carbon in a jar for 5 minutes. It was not a truly controlled experiment. It took it from 60 ppm to zero. My pool is only at 60 PPM, so I am doing this not just for my own pool, but to better understand options for high CYA pools, thus a posting in The Deep End.

    If anyone has insights into this issue, I would like to read about their thoughts.

    del

    PS - I have a degree in chemical engineering and have an interest in water issues in general and have for a while. I am not in the pool business, so I just wanted to disclose where i was coming from.

    - - - Updated - - -

    RO is great! it does waste about 15% of the water, but is still great. I am just trying to come up with something not quite as expensive as RO or a full drain and refill.

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    Re: What and how much will adsorb onto activated carbon??

    I hope you give it a try Del, and let us know how it works out. If it does with a reasonable amount/cost of carbon they are onto something. When I say that over stabilized pools are one of the top problems we see year in and year out, I'm not stretching it at all. Out of curiosity, how expensive is the water out there in SF?
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    Re: What and how much will adsorb onto activated carbon??

    I live in San Diego. It costs about 1.3 cents per gallon for just the water, not the taxes, city fees, etc. This is for the highest of the tier billings. If you do not use too much water in a month, it costs less.

    I will try to give it a try to see what happens and will let everyone know. I think that I will just put some activated carbon in a net bag and leave it in the skimmer for a few days and we will see what happens. Wish me luck.

    BTW- what sorts of CYA levels are typically seen in pools that have not been drained and filled for a while?

    Del

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    Re: What and how much will adsorb onto activated carbon??

    We see people here with CYA levels of 200, 300 or more. If you don't use trichlor pucks or dichlor then CYA doesn't ever get too high. Most folks here chlorinate either manually or via automated pump with bleach/liquid chlorine or use saltwater chlorine generators. I use a SWG and have to add CYA to my pool 2-3 times per year. More here, Pool School - How to Chlorinate Your Pool

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    Re: What and how much will adsorb onto activated carbon??

    I did a quick experiment and took some of my pool water and swirled it in some activated carbon in a jar for 5 minutes.
    Tell us a bit more about that. I assumed the carbon was a filter but your words here seem to suggest there was no vessel such as a filter body to pass the water through. Was the carbon come as a powder? Where did you get it? What was the cost?
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    Re: What and how much will adsorb onto activated carbon??

    Me too, and I'm intrigued. I figured some sort of cartridge assembly or similar.
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    Re: What and how much will adsorb onto activated carbon??

    Sorry about the confusion. I did what I call a "quick and dirty" experiment in wet lab at my office (not a water lab, just a wet lab). I took about 125 ml of my pool water at 60 ppm of CYA and put it into a disposable Ziploc brand cylindrical food storage container. I then put in about a teaspoon of activated carbon granules from Calgon Carbon (Centaur brand). I then stirred it up for a few minutes and re-took the CYA level with the regular Taylor test. The test showed no detectable CYA, which in reality means below 30 ppm as it cannot read lower than that. So, no, I did not test it in a filter. I intend to test it in a filter either on my pool or in a big aquarium. It may be a while before I get more data, perhaps a week or two, but I will try. If someone wants to beat me to the punch, please let me know what results you get. I want to somehow figure out how much non-CYA substances get absorbed, but that assumes that my pool is typical, but it may not be as I do not add a lot of extraneous chemicals to it. If I carefully follow the patent application, I might be able to do some math to figure this out. It may be difficult if the Taylor CYA kit is not precise enough to measure the real CYA level with precision.

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    Re: What and how much will adsorb onto activated carbon??

    I spent some time speaking to a carbon filter research expert yesterday. Long story short, he had little doubt that the method would surely work.

    The drawback is volume. Essentially, the amount of carbon needed to remove say around 50 ppm CYA would be cost prohibitive and take a huge filter.
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    Re: What and how much will adsorb onto activated carbon??

    I am in no way a scientist, Just an excited pool enthusiast

    Very interesting Del, is the link below a version of what you used? When the CYA was reduced to 0 did you also test the Free Chlorine level or any other levels, do you have a TF100 or taylor test kit?

    Seems the activated carbon takes chlorine, chloramines, and a bunch of other stuff out of the water... From what I see we all have the perfect setup for filtering, whether it be sand, cart, or DE it could be added into the filter until CYA was lowered.. The cartridge and DE filter would be easy to clean afterwards but a sand filter may be a little harder to get all the carbon out.

    The second link below is 1 cubic foot of activated carbon, would that be enough to drop, say, 100 CYA to 0? At 200 dollars, 0 water loss and only the cost of adding chemicals back to recommended levels may be a much better solution than emptying 20,000 gallons of water..

    http://www.calgoncarbon.com/wp-conte...015-EIN-E1.pdf

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    Re: What and how much will adsorb onto activated carbon??

    I still want to know more, so I hope you try it in your Pool Del.
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    Re: What and how much will adsorb onto activated carbon??

    Thanks for all of the insight. I do plan on trying it. At 1.3 cents per gallon, it would cost me $338 or so in water bills to change my water. I will keep you posted.

    Del

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    Re: What and how much will adsorb onto activated carbon??

    In my former aquarium and pond days when we needed to filter out something with activated carbon we would put it in a mesh bag and drop it in the filter. So, it might work to add it to a mesh bag and drop it in the pool in front of a return or in the skimmer basket.
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    Re: What and how much will adsorb onto activated carbon??

    Active carbon filtration is used extensively under the German DIN standard for indoor pool management. They use a series of chemical coagulation steps to remove biological and particulate matter through physical filtration and then absorbs THM's and DBP's using activated charcoal filters. The last step is to inject chlorine back into the return water after filtration. Ozone and UV are also used to help handle oxidation of bather waste.

    As Dave eluded to, it is going to take a significant amount of carbon to absorb a lot of CYA as there will be competitive absorption from dissolved organic carbon compounds, chlorine, etc. Then, in the end, there's disposal costs. It can probably be pulled off as a one-time experiment but it is not likely to be commercially viable on a retail scale. I would venture to guess you'll spend just as much on a one-time RO service.


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    Re: What and how much will adsorb onto activated carbon??

    13,000 takes about 2lbs of carbon to lower 5 ppm of cya. It removes chlorine too. Takes about two hours.

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    Re: What and how much will adsorb onto activated carbon??

    Not a cheap solution by any means but they do make some pretty big carbon filters not sure what water replacement costs are in your neck of the woods.
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