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Thread: Fluidized bed filters reduce nitrate?

  1. #1
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    Fluidized bed filters reduce nitrate?

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    heard from david that his FBF reduces nitrate. however, everything in the literature seems to indicate that they reduce ammonia and nitrite instead.

    (could it be they efficiently convert ammonia into nitrate and then your plants eat up nitrate instead of ammonia?)

    ===============
    Fluidized bed filters
    Very recently, some hobbyists have reported success with a new type of filter which uses a fluidized bed of sand. This filter is roughly similar in principle to the reverse flow undergravel filter, but with much higher water flow. The higher water flow keeps the sand clean of debris, while at the same time allowing the development of large and efficient colonies of beneficial bacteria. Reported problems include oxygen depletion and clogging.
    Denitrators
    Another specialized type of filter is designed to help in the control of the accumulation of nitrates, the end product of the neutralization of ammonia by the biological activity of bacteria. These fall into two categories, the anoxic bacterial, and the plant/algal scrubbers (discussed in the next section). It has been discovered that colonies of bacteria which grow in oxygen poor environments can be harnessed to biologically consume nitrate, and release harmless nitrogen gas. This method is achieved in one of two ways. The process was first developed in the 1980's through the use of a box system, coil, or porous foam block which allowed very slow transmission of nitrate-laden water. Inside the box/coil/foam, sugar was placed, and the slow passage of water quickly became anoxic. In these anoxic conditions, bacteria would grow and consume excess nitrate. Many aquarists have reported failure in their attempts at this type of filtration.
    More recently, hobbyists have developed similar anoxic conditions below plates at the bottom of their tanks buried in fine sand. In the saltwater systems, these sand beds are referred to as "live sand". In freshwater planted systems, fine grain substrates are allowed to develop anoxic zones which probably also have a denitrification capability.

    The Berlin Method of reef aquariums involves the use of large quantities of live rock harvested from tropical reefs. Aquarists report good nitrate control in live rock systems, which, though not well understood, probably involves the denitrification of the nitrates within the interior of the rocks. Another school of thought is that the heavy growths of calcareous algae on the live rocks in Berlin Method reef aquariums consume nitrate.

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    Nope... never heard FBF removes nitrates and I don't think it will. Needs anaerobic conditions for denitrifying bacteria.

    As in the article, denitrators are the equipment used for removing nitrates.

    BC

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    hi Lou

    If your FBF is placed on the inlet pipe of your water system...than what you are saying is correct as it acts as a normal filteration system...however if placed on the outlet pipe, you are 'culturing' anaerobic bacteria which breaks nitrate further into nitrogen..........however if the nitrate level drops to zero, these bacteria will die off........perhaps Yimin will have a better insight to this than I do.....
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    If your outlet from your filter is anerobic, you either have a lot of organics in your water, have a very large filter to maintain the bacteria population to use up all the O2, or a very large fluidised bed with a slow flow. In other words, unless you are filtering sewage...

    In anyway, your fish would have suffered from lack of O2 before anything considering the turnover of the filter (unless your flowrate very very slow).

    I second the notion that plants (or algae) removed the nitrate/ammonium.

  5. #5
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    hmm; wonder whether I should go to the expense of getting one..

    I notice my filter outlet usually get these bacteria slime of scum (at least some of it ends up at my co2 reactor..) so I wonder if it will clog up the FBF.

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    ----------------
    On 4/30/2002 7:31:39 AM

    If your outlet from your filter is anerobic, you either have a lot of organics in your water, have a very large filter to maintain the bacteria population to use up all the O2, or a very large fluidised bed with a slow flow. In other words, unless you are filtering sewage...

    In anyway, your fish would have suffered from lack of O2 before anything considering the turnover of the filter (unless your flowrate very very slow).

    I second the notion that plants (or algae) removed the nitrate/ammonium.
    ----------------
    I agree with CK.

    If your filter outlet is anaerobic, something is really wrong with the system. If it is, the filter itself is probably anaerobic. And that means your aerobic bacteria would have died!!

    BTW, FBF is not meant for that purpose. Anyway, you cannot have low flow in a FBF. You need to get enuf flow into the FBF to get it fluidised. The larger the FBF the larger the flow is needed. IMO, it probably will never work as a denitrator.

    Go get a proper denitrator if removing nitrates is what you want.

    BC

  7. #7
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    heh.. ok: I went to buy a rainbow lifegard from petmart $165..


    we'll see how it works.

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    hi CK

    could you elaborate on what you are saying coz i dont understand?

    hi bclee

    what i meant was not the water is anaerobic but attempting to culture anaerobic bacteria in the FBF.

    In fact to be honest...I was never a believer of the FBF or its concept till i gave it a go. My discus, altum, and tetra tanks had a nitrate reading of 50 to 60ppm (finally reading just before water change of 40% every 5 days).

    being so sick of the high nitrate level, I decided to give the FBF a go for the discus thank. After the FBF went in, the first week, the reading was pretty much the same and after the second week, it drop to about 20 ppm or so.

    Impressed with the result of the discus tank (but still sceptical), i decided to get another FBF for the Altum tank....and similiar result came....and lastly for my tetra tank as well.

    If it only happen for just one tank, it could be a fluke shot...but three tanks?
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    On 5/1/2002 11:34:00 PM
    hi CK
    could you elaborate on what you are saying coz i dont understand?
    ----------------
    Which part dun you understand?
    ----------------
    hi bclee

    what i meant was not the water is anaerobic but attempting to culture anaerobic bacteria in the FBF.
    ----------------
    How else can you culture anaerobic bacteria if the water is not anaerobic? They can't denitrify (use NO3 as electron acceptor) if there is O2 present as electron acceptor.

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    that's why I propose my theory that. fbf denitrify's the water so quickly that the plants can't use the ammonia/ammonium, they end up using only the nitrate that's present in the water column

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    ----------------
    On 4/30/2002 7:31:39 AM

    If your outlet from your filter is anerobic, you either have a lot of organics in your water, have a very large filter to maintain the bacteria population to use up all the O2, or a very large fluidised bed with a slow flow. In other words, unless you are filtering sewage...

    In anyway, your fish would have suffered from lack of O2 before anything considering the turnover of the filter (unless your flowrate very very slow).

    I second the notion that plants (or algae) removed the nitrate/ammonium.
    ----------------
    david uses 2 2028s in both coupled to fbfs
    he is also having slow flow rate
    and you're assuming your fish live off the o2 from the filter output
    but plants produce o2 at the same time

    chris' theory sounds feasible
    so does david's theory

    either way, the FACT is, fbfs have done it for david
    if you have the extra bucks, i'd say, why not?
    but for me, i'd rather trust in the plants

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    Hello David,

    May I ask how fast is the flow through your FBF? Is the flow high enuf until the all the particles are "floating" in the water?

    BC

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    none of the particles are floating in the water

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    2028 is rated 277GPH.
    Say the tank is 120G (4 feet tank).
    So in about two hours, most the water would have turned over and if the fluidised bed filter is really anerobic, you will have almost no O2 by then. Of course there will be diffusion from air etc, but can it keep up with 1048L/h? Say the filter run at 80% efficiency, then, total turn over happens in 2.5hrs.
    especially at night when the fish, the plants and the bacteria are all competing for the O2 and your only source of O2 would be through diffusion wouldn't it?

    Plants are the best nitrate absorbers.

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    ah yes, but there has to be a tree, you see (obscure joke reference here, ignore it if you don't get it)
    from point A to point B, something has happened that caused the nitrate to drop from 60 to 20
    and the only change was the addition of the fbf
    ergo, there must be a mechanism whereby nitrate is removed
    plants, could be, but not likely as they were held as control during the whole thing, ie no increase/decrease of plant biomass in the tank
    what we can say is that it is shown that fbfs do reduce nitrate to an extent in the tank
    but we don't know the mechanism, so we can't say it's proven

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    So "guilty until proven innocent"? I rest my case.

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    well
    we have experimental data
    and the overall picture is the fbf in david's tank was the only change that caused the nitrate to lower
    you do the math

    if you haven't tried it, don't knock it

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    ----------------
    On 5/5/2002 1:26:10 AM

    none of the particles are floating in the water
    ----------------
    Ha! That is exactly what I suspected.

    FBF was design base on the "FLUIDISEd BED" principle. This means the the particles was supposed to be FLUIDISED... which is to run with flow rate high enough that all the particles suspended in the water. This is to give a very high contact area. This method is super efficent for NH3 and NO2 conversion to NO3.

    If the particles are not suspended, it cause a lot of dead spots in the column. That explains the nitrate reduction.

    A word of caution though... this is something like an anaerobic substrate. In the similar way that NO3 was reduced to N2, SO4 can be reduced to H2S... very poisonous.[]

    A denitrator works somewhat differently. In one type, You actually cultivate bacteria specific for NO3 reduction. You can check the http://www.sera.de/English/Produkte/Bio-Denitrator.htm"]Sera one[/url]. The other uses algae or plant to consume the NO3.

    BC

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    I am selling a bottle of FBF medium
    Brand is RainbowLifegard , no need to say its probably the best brand for FBFs.

    Brand new.
    Note i am just selling the medium alone.

    The bundle at $165 you get from Petmart doesnt include it. STill got to fork out $25 for one bottle.

    Am clearing at $15.
    No use for it anymore.
    Just email me at [email protected] if anyone here is interested.

    Mods - sorry to put this here but in case any of the people here who know about FBFs are interested.
    Thanks

  20. #20
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    bc, have you used the seachem one?

    it also works, but it appears that it doesn't matter where you put it, ie the oxygen content doesn't seem linked to the function of the denitrate (tm)

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