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Wet/Dry and O2 access.

Discussion in 'CO2 Enrichment' started by shoggoth43, Oct 14, 2011.

  1. shoggoth43

    shoggoth43 Lifetime Charter Member
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    After a quick exchange with Tom and the fact that I probably want to run with larger fittings on my CO2 reactor, or at least for as long as I have it, I ran across this thread over on TPT where they're just stuffing CO2 into one of those drinking water filter cannisters. No double venturi or looping it back. Just the cannister and maybe a vane in it to cause the water to swirl around a bit.

    I was also clicking on some other links and ran across someone who took another approach. Tom often mentions sealing the biotower on a wet/dry to reduce CO2 loss. Someone decided to run theirs sealed as well, but they put the CO2 inlet under the tower. CO2 bubbles up into the tower and they use that as their reactor chamber. He was also running with the water level high enough that there was no gap under the tower. This essentially IS the PVC reactor with bioballs in it except in box form.

    This seems almost far too simple to work so I also started wondering about the biotower. If we seal this up as Tom recommends, the only O2 that can get in "must" come from what's in the water. So now I have to wonder, what is the wet/dry doing? It would seem as though we're not really getting much benefit from the "dry" other than media capacity and the sheer amount of space for the bacteria? Or is the O2 somehow coming out of the water to replace "airborne" O2 lost in the dry chamber and thus still allowing the bacteria more efficient access to O2? If that's not the case, should we just flood the media and get rid of all that splashing which might drive off the CO2?

    George Booth had a whole thread on his setup many years ago and they were using the Dupla methods. At one point they were injecting air or maybe even O2 into the wet/dry but stopped as it wasn't doing anything they could see other than driving up CO2 usage. Possibly because the air was displacing the CO2 in the biotower.

    So, is the bacteria getting the O2 directly from the water, or is it pulling it from the "air" in the biotower which is supposedly the reason these are such incredibly efficient filters? If it's coming from the air, how is it getting replenished from the water if the bacteria is presumably consuming much of it? I suspect I'm really just overthinking this a bit, but the idea of removing a reactor or eliminating the needlewheel has a large amount of appeal but I could see needing to cut off the flow a bit sooner so that CO2 doesn't still need to be dissolved after lights out.

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    S
     
  2. chopsticks

    chopsticks Prolific Poster

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    I have the same questions about the sealed biotower.

    I have mine sealed and I thought the sealing works because the atmosphere in the biotower gets so rich in CO2 that the biotower starts working like a reactor, it gets to a point that the only way the CO2 could do something is being disolved in the water.

    I that injecting the CO2 directly in the biotower could be a very slow method to get the CO2 in the water, the biotower will just work like a giant CO2 bell with surface agitation.

    I think Tom said his wet/dry tanks get to the low CO2 level 45 min after cutting the CO2 flow, so even with the sealed biotower theres a lot of gas exchange going on.

    I suspect that it is the overflow per se and not the biotower that does this gas exchange.

    Please excuse the bad "english"

    Juan
     
  3. shoggoth43

    shoggoth43 Lifetime Charter Member
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    My overflow doesn't inject any air into the biotower. There's no durso or any bubbles sucked into the system. It's a Herbie type so there's just water. I'm not sure how this changes things. The only way O2 is going to get into the biotower air is if it comes out of solution as the water flows through the biotower.

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  4. shoggoth43

    shoggoth43 Lifetime Charter Member
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    Well, I finally sealed the biotower after determining that my CO2 leak was the lousy clippard solenoid. I don't know that the solenoid is the issue so much as the rubber O ring which became brittle and useless, the internal seal is also rubber, so there is a moderate amount of blow by when the solenoid is off as the pad is now brittle as well. I have removed the needlewheel feeding into the main pump and I'm just bubbling the CO2 into the biotower from below to see if this is a viable method.

    Of note: in my plumbing, the return lines to the sump go to the floor and then back up to the top of the sump. This is due to the design of the stand and there's not much I can do about that without emptying the stand and boring holes. This pretty much means that when the main pump is off, I have water in those lines at the bottom of the "U", like a sink trap. For a Herbie overflow, and the main line, this is not much of an issue. The air purges and there's no real problem nor with the emergency drain.

    However, the Eshoppes wet/dry I have has two inlets on the biotower. I had been using both of these for the Herbie. When I sealed the biotower, the main "wet" line works just fine. The emergency line does not work properly. The combination of the water at the bottom of the U and the backpressure from the biotower prevents this line from purging properly in the event of a clog on the other line. Or at least this seemed to be the case. I didn't care to let this continue to build up the level in the tank too high while I tweaked it. I may need to experiment with this a bit more.

    In the meantime, the "dry" line goes to the sump and the "wet" goes to the biotower. This seems to work just fine until I can find some time to tinker around with the plumbing a bit. I was not expecting there to be an issue with the dry line so there's definitely something amiss, but it may just be that I didn't give it enough time to kick in. The backpressure definitely seems to be causing some issues.

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    #4 shoggoth43, Oct 23, 2011
    Last edited by a moderator: Oct 23, 2011
  5. Biollante

    Biollante Lifetime Charter Member
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    Herbie Emergency Bypass Is In Order

    Hi,

    I had a similar issue with my Herbie when I sealed a sump; I simply bypassed the first stage with the emergency. In my case, this may mess up the filter function, but no water ends up on the floor.:) It also makes a lot of noise so it will be noticed.



    I have found sealing the first stage really seems to be at best an even trade, sealing the whole thing leaves you with a canister filter. I pretty well figure the CO[SUB]2[/SUB] losses are offset by improved wet/dry function. :)


    I have actually introduced air strippers into my larger (multi-tank) systems, from an efficiency/effectiveness of the system point of view I think I come out ahead giving up all the CO[SUB]2[/SUB].


    As an added bonus: unsolicited opinion on Clippard, I am not impressed. Speaking as a cheapskate, CO[SUB]2[/SUB] system components are not the place to save a few bucks.


    Biollante


     
    #5 Biollante, Oct 23, 2011
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  6. shoggoth43

    shoggoth43 Lifetime Charter Member
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    The regulator I bought had the clippard on it. Now I have to re-read all those other solenoid threads...

    I'm still not sure what happens with the O2 part of this. I'm not injecting air into the unit and unsealed there seems to be no real way for the air to circulate within the tower, so I can only hypothesize that the O2 may be outgassing from the water into the biotower due to the relative lack of O2. Essentially osmosis if that makes any sense. With the typical durso style overflow you'd have all that entrapped air in the stream constantly ventilating the tower/sump.

    I'm thinking the next experiment will be to take the wet and dry lines from the overflow and run those into a prefilter box in the sump. I'll have the pump running full tilt and divert flow from the tank return into the sealed tower and put the CO2 in there as well. This should get around any backpressure issues and still allow for some filtering of the emergency line if needed. Also, since the diverter lines are already in place at that point it would be easy enough to add extra refugia or reverse lighting setups and whatnot.

    How are you stripping out the air on your systems?

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    S


     
  7. chopsticks

    chopsticks Prolific Poster

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    What I think is that most of the gas exchange happens in the display tank when you seal the biotower, because the overflow doesn't allows the water ot develop any surface film, maybe on an unsealed biotower gas exchange happens in both places, but maybe with the clean water surface is enough to get proper gas exchange.

    Could a dropchecker in the biotower tell us something useful?
     
  8. shoggoth43

    shoggoth43 Lifetime Charter Member
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    I don't think a drop checker is going to tell me much. It would probably tell me I have a lot of CO2 in the biotower. :) I would expect the tank would have less. However, I still think the O2 has to be coming from the main tank and then diffusing out into the biotower. Most towers aren't sealed, but they aren't exactly wide open for airflow. Maybe along the lines of a cardboard box. Not exactly going to get a lot of O2 in there without some air movement. There's not really going to be a lot of movement in there UNLESS we pump air in. Your typical overflows are going to do that for you either with the gurgling straight pipe or the stockman or durso or hofer.

    Mine doesn't put air in the system, but since I've run it this way for at least months if not well over a year at this point, I think we can safely assume that if there weren't enough O2 in there I'd probably know about it by now. So either the wet/dry is getting O2 from the water into the air inside the tower and this is helping with the bacteria, or I really don't have anything better than a not quite flooded, not entirely airtight, cannister filter on the system and may as well just submerge the biomedia which might drastically change the sump designs I've been thinking of.

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    S
     
  9. Biollante

    Biollante Lifetime Charter Member
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    You Are Injecting Oxygen

    Hi,


    If your biological filter is... well, filtering biologically, we know you are injecting oxygen.



    Chopsticks is almost right :)(in my ever-humble-potted-plant opinion), the oxygen is being injected,


    • actually sucked in via the overflow,
    • sealing the canister does not stop the gas exchange,
    • simply increases the partial pressure.
    The “backpressure” you experience is precisely that, by sealing the tower you are raising the “air” pressure above 1-atmosphere[SUP]1, 2[/SUP].


    My experience is that both carbon dioxide and oxygen increase somewhat.


    Much of the CO[SUB]2[/SUB] retention rates appeared to be as much function of the “smoothness “of water introduction as the increased pressure.

    • Another way to think of this is the same thing that gives us quieter operation also produce better CO[SUB]2 (Aq)[/SUB] retention.:)

    As long as the dry lines are not submerged in the a pre-filter box in the sump or a later stage, no matter where you run the dry lines (except the sealed bio-tower) they must be out of the water to avoid back pressure.:rolleyes: This will make them noisy when in use, I consider that that an “alarm.”:cool:


    Biollante
    [SUP]1[/SUP]Actually increases above the ambient pressure.
    [SUP]2[/SUP]The best pressure increase I was able to get was something under 8” (~0.0024%), most were around 4-5”.



     
  10. shoggoth43

    shoggoth43 Lifetime Charter Member
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    Yep, emergency line is noisy on mine now that I've got it running to the sump although the end is submerged in the sump somewhat. Came home after a long weekend to a very noisy overflow up top. Very glad everything worked just like it was supposed to. :)

     
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