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Thread: Degassing Columns

  1. #21
    Honmei ricshaw's Avatar
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    Quote Originally Posted by PapaBear View Post
    No hiding from the "nose" test . Even with a great pond, tailpipes from the waste line will get "ripe" after a day or two.
    Water from tailpipes from the waste line stink because of a mostly unavoidable design flaw. If the waste line had a stand pipe in the pond or filter for a valve instead of a valve further down the length of pipe where anaerobic conditions can exists inside the pipe before the valve, the stink would be less.

  2. #22
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    Quote Originally Posted by RobF View Post
    Is anyone certain that ammonia removal by air stripping at the pHs and temperatures and air flow of a koi pond system actually works? The AES write up says of their device says “The hydraulic design and high surface area of these units make them very suitable for "tricking biofilters" for ammonia removal.” Biofilter sure, but significant ammonia outgassing, is not claimed. So when they eariler say "Nitrogen" removed they probably mean N2 not NH3.
    I know just a little bit about this, but I also am not claiming to be an expert, so your mileage may vary......

    Just to refresh all of our memories, ammonia is considered a "gas" (at standard temperatures and pressures), but it is a gas which is wonderfully soluble in water. If one has ammonia (NH3) in water, however, one also has "ammonium" (NH4+) present, as the two molecules exist in equilibrium (in aqueous solution). Unlike ammonia, ammonium -- as a cation -- will not readily off-gas from water. The ratio of ammonia (NH3) to ammonium (NH4+) is highly pH-dependent; in ponds, most of the NH3/NH4+ present is in the NH4+ (ammonium) form. (Higher pH will shift the ratio towards ammonia [NH3]).

    The wastewater treatment industry performs something called "ammonia stripping," the set-up of which strongly resembles these degassing columns. There is a bid caveat, however, in that ammonia stripping really doesn't work so well at pond-appropriate pH levels. Because it is ammonia (NH3) and not ammonium (NH4+) which is effectively off-gassed, most of these large-scale installations will bump up the pH considerably (like to pH 11 or so) in an effort to drive a lot of the nitrogen present to the "ammonia" side of the equilibrium (which can then be off-gassed).

    About a year or so ago, myself and one other person over on 'Phen were independently performing some small-scale experiments with showers. We came to similar conclusions. Using bottled ammonia and "fresh" (non-colonized) substrate, we couldn't observe any significant off-gassing of ammonia at pH levels that were appropriate for a pond.

    I also could not get my small experimental shower to off-gas nitrate (NO3-), although others have claimed to see a reduction in nitrate levels from using showers. I cannot account -- from a chemistry standpoint -- how nitrate (another salt) would directly off-gas, but from speaking with others and trying to read what I could, I have formed an opinion. I suspect that the mechanical agitation of a shower/degassing column, coupled with the fantastic water-to-atmosphere surface area created, allows for other nitrogen intermediates (such as nitric oxide and nitrous oxide) to directly off-gas (and this results in less nitrate as a final product). People may think that their column/shower is directly off-gassing ammonia (or nitrate), but I believe that actual off-gassed nitrogen is mainly in the form of one of these microbial-mediated intermediates.

    This is not my original theory by any means -- others much more knowedgable than myself have unraveled this stuff -- but I do think this explanation is consistent with what people are reporting.

    As for the N2 -- well, I really don't know. I just cannot see much denitrifcation (which results in N2 being formed) happening to any significant extent in the well-oxygenated environment of a column/shower.

    Again, this is just my opinion and limited experience with the issue.

  3. #23
    Daihonmei PapaBear's Avatar
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    Good show Paul, and I think your observations link up well with the mainstream of what has been discussed, particularly the ammonia/ammonium relationships and the reference to "nitrogen intermediates (such as nitric oxide and nitrous oxide) to directly off-gas (and this results in less nitrate as a final product)". Temperature dependence along with ph play a major role and all of these things go a long way toward explaining the relatively rapid positive results from showers, towers, and columns of this type.

  4. #24
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    Hi Larry,

    Thanks for the vote of confidence!

    I am still really wrestling with the shower/column/TT idea in my own grandiose pond plans. There are a lot of things I really like about showers/columns, but I am also a bit adverse towards the electrical costs of having to lift the water high enough for these sort of designs. In the end, I guess everything is a compromise!

    Paul

  5. #25
    Daihonmei
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    Side bar:

    You will often hear or read that water low in

  6. #26
    Daihonmei PapaBear's Avatar
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    Quote Originally Posted by JasPR View Post
    ...ammonia leaves the water BEFORE IT IS AMMONIA by prefilter/sump and water change management. It is REDUCED by protein skimming and evaporation. And all it's intermediate conversions that are gaseous in nature are vented via a tower.
    It is very difficult for the beginner and intermediate koi keeper to envision anything beyond ammonia conversion as that is a full time job for the first year or two. And to a degree, organic removal ( but just in terms of water clarity) is mastered along the way. So some of this is a new to the ear drum.
    Something to think about. JR
    Interception vs mediation vs remediation might be one way to describe it.

  7. #27
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    Quote Originally Posted by JasPR View Post
    But on a more important level, the biofilm itself will be nitrifying AND denitrifying in certain settings.
    as I mentioned in many writings on the internet and in print, the biofilm itself is not all of the same oxygen, ORP or pH from area to area. And depending on environment the film can be very denitrification friendly just based on the dead layers of cells that are either biofouled or simply unable to slough off into the passing current.
    Hi JR,

    As always, I pay heed to what you have to say, and I have great respect for your extensive experience in Koi and pond-related issues....

    ...but I don't entirely feel the same way as you do about the microfilm environment within a degassing column/TT/shower. Simply put, I am not convinced that significant denitrification is taking place in the microfilm environment -- especially within these showers or columns.

    Why?

    For me -- and perhaps I am wrong -- it comes down to the energy yield of these reactions. When a bacteria oxides ammonia to nitrite (NO2-), the incentive for the bacteria is a net energy yield from the reaction. The bacteria will utilize that energy yield for a variety of biochemical processes, but suffice to say that this energy yield (or "delta G" [Gibbs free energy change for the chem nerds]) can be viewed by us as a fuel source for said bacterium. Ditto on the oxidation on nitrite to nitrate (NO3-), as the bacteria which perform this conversion also gain a net energy yield via this process.

    When we talk about denitrification, that is -- converting the nitrite/nitrate forms into other products, with dimolecular nitrigen (N2) being released into the atmosphere -- we are looking at an energetically "uphill" reaction. In other words, it "costs" the bacteria energy perform this reaction. There are lots of microbial twists on this theme and I am admittedly making some generizations, but I do believe this is fundamentally accurate. Therefore, what would cause a bacteria to spend the energy to reduce (i.e. "denitrify") these already-oxidized nitrogen forms? Aside from assimilation of nitrogen for cellular construction processes (which would require energy as well), the incentive to the bacteria for reducing nitrate/nitrite comes if that bacteria can oxidize something else, with a net energy yield in the final tally. If it costs the bacteria "x" in energy terms to break the bonds, but it gains "x + 1" to form the resultant product bonds, the bacteria may gain the net energy yield (energy change after expenses and earning, if you will). This other (energy-yielding) reactant molecule is usually some carbohydrate or protein. In a very low or no oxygen environment, the anerobic or facultative bacteria may be sufficiently "motivated" to reduce nitrate/nitrite (resulting in the release of N2) if another energy-yielding molecule is present (and the bacteria gets a net energy gian). My memory may be hazy on some of this, but I think this is mostly textbook-type stuff. Please correct me if I am remembering some of this incorrectly.

    In the highly-oxygenated environment of a shower/column, however, one would need to have both an energy-rich molecule AND nitrate in the presence of the (anerobically-living) bacteria discussed in order for denitrification to occur. I can't see this happening. Say, hypothetically, that one added a carbohydrate source to an established degassing column: I strongly believe that the aerobic bacteria present -- being so much more efficient -- are going to utilize that carbohydrate source almost entirely, leaving little or none to ever make it into the inner layers of biofilm where anaerobic conditions might be present.

    And maybe I'm really missing the mark. I apologize in advance for my (potential) ignorance, but I would rather hold up my current understanding for further scrutiny and debate, than just disagree in silence and learn nothing. Can you see a logical pathway for significant denitrification within a column, taking into account the energy yields involved?

    Sorry if I am being dense, but I do appreciate the discourse.

    Paul

  8. #28
    Jumbo RobF's Avatar
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    Paul, As far as I can see your explanation is right on the mark, both in terms of the chemistry, energy budget and is framed well for a Koi Forum’s level of understanding and application. I especially appreciate that you have actually made measurements and you speaking in terms that are specific shows your intent is to illuminate.

    It has been suggested, elsewhere, that the energy needed to move from nitrate to N2 in a tower comes not chemically, or electromagnetically but mechanically from vigorous agitation. In this method a bacterial intermediary is probably still required and it is conceivable that it wouldn’t have to be anaerobic. I don’t think anyone has documented how this would translate chemically (and for that matter I don’t think that this is happening). But I mention it because it is an example of the vague thinking offered by proponents of towers in nitrate reduction. It is probably the same straw grasping that brings to the fore the chemical intermediaries you describe (since their solubility, dwell time and concentration would seem to strongly limit any outgassing effect). Towers are fine, but they are no panacea. Once again, I congratulate you upon actually addressing the problem (and making measurements) head on.

  9. #29
    Tategoi andy's Avatar
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    As a student and wanting to learn about this subject I can see me believing both sides of the argument. Paul and JR really present very logical concepts but frankly who should I accept as gospel?

    Maybe its time to have AKCA sponsor a study/research on this matter. I'm sure a graduate student would love the opportunity......

  10. #30
    Daihonmei
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    Quote Originally Posted by Paultergeist View Post
    Hi JR,

    As always, I pay heed to what you have to say, and I have great respect for your extensive experience in Koi and pond-related issues....

    ...but I don't entirely feel the same way as you do about the microfilm environment within a degassing column/TT/shower. Simply put, I am not convinced that significant denitrification is taking place in the microfilm environment -- especially within these showers or columns.

    Why?

    For me -- and perhaps I am wrong -- it comes down to the energy yield of these reactions. When a bacteria oxides ammonia to nitrite (NO2-), the incentive for the bacteria is a net energy yield from the reaction. The bacteria will utilize that energy yield for a variety of biochemical processes, but suffice to say that this energy yield (or "delta G" [Gibbs free energy change for the chem nerds]) can be viewed by us as a fuel source for said bacterium. Ditto on the oxidation on nitrite to nitrate (NO3-), as the bacteria which perform this conversion also gain a net energy yield via this process.

    When we talk about denitrification, that is -- converting the nitrite/nitrate forms into other products, with dimolecular nitrigen (N2) being released into the atmosphere -- we are looking at an energetically "uphill" reaction. In other words, it "costs" the bacteria energy perform this reaction. There are lots of microbial twists on this theme and I am admittedly making some generizations, but I do believe this is fundamentally accurate. Therefore, what would cause a bacteria to spend the energy to reduce (i.e. "denitrify") these already-oxidized nitrogen forms? Aside from assimilation of nitrogen for cellular construction processes (which would require energy as well), the incentive to the bacteria for reducing nitrate/nitrite comes if that bacteria can oxidize something else, with a net energy yield in the final tally. If it costs the bacteria "x" in energy terms to break the bonds, but it gains "x + 1" to form the resultant product bonds, the bacteria may gain the net energy yield (energy change after expenses and earning, if you will). This other (energy-yielding) reactant molecule is usually some carbohydrate or protein. In a very low or no oxygen environment, the anerobic or facultative bacteria may be sufficiently "motivated" to reduce nitrate/nitrite (resulting in the release of N2) if another energy-yielding molecule is present (and the bacteria gets a net energy gian). My memory may be hazy on some of this, but I think this is mostly textbook-type stuff. Please correct me if I am remembering some of this incorrectly.

    In the highly-oxygenated environment of a shower/column, however, one would need to have both an energy-rich molecule AND nitrate in the presence of the (anerobically-living) bacteria discussed in order for denitrification to occur. I can't see this happening. Say, hypothetically, that one added a carbohydrate source to an established degassing column: I strongly believe that the aerobic bacteria present -- being so much more efficient -- are going to utilize that carbohydrate source almost entirely, leaving little or none to ever make it into the inner layers of biofilm where anaerobic conditions might be present.

    And maybe I'm really missing the mark. I apologize in advance for my (potential) ignorance, but I would rather hold up my current understanding for further scrutiny and debate, than just disagree in silence and learn nothing. Can you see a logical pathway for significant denitrification within a column, taking into account the energy yields involved?

    Sorry if I am being dense, but I do appreciate the discourse.

    Paul

    Not dense Paul, just down the wrong road. Mineralization is your 'missing link' JR

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