Looking for thoughts on organic carbon dosing and nitrate

[taricha]

Just wondering about details again. Do you think the nitrate consumption is performed by pelagic bacteria or those associated with particulates in the aquarium?

Doing it in just a liter of tank water, the water clouded slightly (indicating massive increase in population)
Then the NO2 showed up.
My presumption is that there are many bacteria that can do this in the water or on surfaces. I also assume it's some portion of the population that scale up with the carbon dose that are doing the NO3->NO2.

My comment that it'd probably take less carbon if there were sand/rock is based on a guess that is easier to make space low in O2 at the substrate surface than in the bulk water.

 

[Dan_P]

Doing it in just a liter of tank water, the water clouded slightly (indicating massive increase in population)
Then the NO2 showed up.
My presumption is that there are many bacteria that can do this in the water or on surfaces. I also assume it's some portion of the population that scale up with the carbon dose that are doing the NO3->NO2.

My comment that it'd probably take less carbon if there were sand/rock is based on a guess that is easier to make space low in O2 at the substrate surface than in the bulk water.

Got it. Thanks.

I am thinking about exploring the behavior of water vs water+aragonite (Aquarium sand vs 1 month old inoculated sand). This investigation might turn up interesting data.

 

[biom]

The respiration from living organisms will result in CO2. CO2 is used by photosynthetic organism in order to produce organic matter. CO3 is used by stony corals in order to form limestone. IMO and IME - the chemo autotroph nitrification organism needs CO3 in the water in order to form organic matter - CO2 in water seems not to matter for them. They maybe need to transform the CO3 to CO2 inside the organism but they do not work with only CO2 in the water IME. I know there is different opinions about this.

In the water with pH 8.2 inorganic carbon is mostly in form of bicarbonate ion HCO3-. To have a significant amount of CO3- pH should be well above 10 which is not very common for surface waters except some alkaline lakes.

 

[biom]

And for the books - I do not believe in the direct nitrification/denitrification in a single microfilm. It has been the wet dream for waste water technicians for decades and the closet they have come is the sequencing batch reactor (SBR) . IMO - one of the must important factors why its difficult to achieve nitrification/denitrication in the same biofilm without sequencing is the demand for DOC in the denitrification.

Actually from first paper I googled based on your suggestion they say nitrification/denitrification do happen in the same biofilm.
"O2 consumption took place in the upper 50 to 100 um of the biofilm, with a rate of 0.81 umol /cm2/h. The production of NO3 2 plus NO2 2 appeared in the same layers, with a rate of 0.73umol z cm2/h... Denitrification in the layers below 150 um ranged from 0 to 0.28 umol/cm2/h, with an average of 0.11 umol /cm2/h"
Yes, denitrification happened with much slower rate but we should consider no additional DOC was dosed in this experiment the biofilms were grown on plastic foils, placed in the water cycle of an aquaculture producing eels.

Structure and function of a nitrifying biofilm as determined by in situ hybridization and the use of microelectrodes.

Microprofiles of O2 and NO3- were measured in nitrifying biofilms from the trickling filter of an aquaculture water recirculation system. By use of a newly developed biosensor for NO3-, it was possible to avoid conventional interference from other ions. ...

www.ncbi.nlm.nih.gov

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC168290/pdf/624641.pdf

 

[Lasse]

consider no additional DOC

That´s a reason for that - if DOC was dosed - it should favour the heterotrophic bacteria and hinder the nitrification bacteria both from O2 and space. You can´t get denitrification to to happen in the same rate as nitrification in a single biofilm . You must sequence it - first nitrification and after that denitrification - in the same batch but first a period of good oxygen and inorganic carbon - after that a period with bad oxygen concentration and adding DOC . - SBR reactors. Its the same biofilm but during different environmental conditions - not simultaneous in a run trough system

Sincerely Lasse

 

[biom]

The purpose of the experiment is to generate data to better understand the factors influencing carbon dosing in an aquarium. What provoked me into experimenting is the large dose of carbon needed before nitrate concentration starts to decline. An even deeper question is whether nitrate is reduced, assimilated or both. I don’t think that I can address the second question.

Make sense?

I think @taricha partially answered second question - if nitrites appear in his experiment after dosing nitrates (if there were no significant NH4) then there was denitrification happened for sure.

Maybe 1 ml vinegar per 1 gallon water is not that large dose organic carbon after all. I think it is about 6 mg/l carbon which if you are battling 20 mg/l NO3-N is not that much.
I would not expect to remove 20 ppm N with 6 ppm C by assimilation only having in mind C/N ratio of heterotroph bacteria is 69/16 and knowing much of the organic carbon is used as energy source not only as "building blocks". It should be other process involved for example denitrification.

 

[Dan_P]

I think @taricha partially answered second question - if nitrites appear in his experiment after dosing nitrates (if there were no significant NH4) then there was denitrification happened for sure.

Maybe 1 ml vinegar per 1 gallon water is not that large dose organic carbon after all. I think it is about 6 mg/l carbon which if you are battling 20 mg/l NO3-N is not that much.
I would not expect to remove 20 ppm N with 6 ppm C by assimilation only having in mind C/N ratio of heterotroph bacteria is 69/16 and knowing much of the organic carbon is used as energy source not only as "building blocks". It should be other process involved for example denitrification.

Good points.

The other provoking observation is that initially a little vinegar does not remove a little nitrate, but a “large” amount of vinegar kicks off the process of nitrate removal which can then be throttled back by reducing the dose. By the way, if dosing stops, will starting it up after a few months require the large dose to kick off the process? Yes (for my system anyway).

While we might come up with a reasonable stoichiometry for the process, the kinetics would remain thought provoking.

 

[biom]

Good points.

The other provoking observation is that initially a little vinegar does not remove a little nitrate, but a “large” amount of vinegar kicks off the process of nitrate removal which can then be throttled back by reducing the dose. By the way, if dosing stops, will starting it up after a few months require the large dose to kick off the process? Yes (for my system anyway).

While we might come up with a reasonable stoichiometry for the process, the kinetics would remain thought provoking.

I can confirm from my experience there is a difference in starting and maintenance DOC dose.

Possible scenario: You need relatively large DOC dose in the beginning because there are bunch of nitrate accumulated already. There are possibly different processes involved. In the beginning when there is excess of nitrate after DOC dosing it is denitrification dominating, because stoichiometry shows other processes not really possible in a big scale. Once nitrate is reduced significantly the "normal" aerobic heterotrophs outcompete nitrifiers and assimilatory process of NH4 dominate which means less NO3 is produced and the need of maintenance DOC dose is lower.
When stopping DOC dosing, nitrifying bacteria will take advantage over heterotrophs because they don't need DOC for energy, they use NH4, and NO3 will start accumulating again and you ll need relatively large dose of DOC to start denitrification.

 

[Lasse]

I can confirm from my experience there is a difference in starting and maintenance DOC dose.

Possible scenario: You need relatively large DOC dose in the beginning because there are bunch of nitrate accumulated already. There are possibly different processes involved. In the beginning when there is excess of nitrate after DOC dosing it is denitrification dominating, because stoichiometry shows other processes not really possible in a big scale. Once nitrate is reduced significantly the "normal" aerobic heterotrophs outcompete nitrifiers and assimilatory process of NH4 dominate which means less NO3 is produced and the need of maintenance DOC dose is lower.
When stopping DOC dosing, nitrifying bacteria will take advantage over heterotrophs because they don't need DOC for energy, they use NH4, and NO3 will start accumulating again and you ll need relatively large dose of DOC to start denitrification.

Now we are talking

Sincerely Lasse

 

[Dan_P]

I can confirm from my experience there is a difference in starting and maintenance DOC dose.

Possible scenario: You need relatively large DOC dose in the beginning because there are bunch of nitrate accumulated already. There are possibly different processes involved. In the beginning when there is excess of nitrate after DOC dosing it is denitrification dominating, because stoichiometry shows other processes not really possible in a big scale. Once nitrate is reduced significantly the "normal" aerobic heterotrophs outcompete nitrifiers and assimilatory process of NH4 dominate which means less NO3 is produced and the need of maintenance DOC dose is lower.
When stopping DOC dosing, nitrifying bacteria will take advantage over heterotrophs because they don't need DOC for energy, they use NH4, and NO3 will start accumulating again and you ll need relatively large dose of DOC to start denitrification.

This seems plausible

 

[Randy Holmes-Farley]

Actually from first paper I googled based on your suggestion they say nitrification/denitrification do happen in the same biofilm.
"O2 consumption took place in the upper 50 to 100 um of the biofilm, with a rate of 0.81 umol /cm2/h. The production of NO3 2 plus NO2 2 appeared in the same layers, with a rate of 0.73umol z cm2/h... Denitrification in the layers below 150 um ranged from 0 to 0.28 umol/cm2/h, with an average of 0.11 umol /cm2/h"
Yes, denitrification happened with much slower rate but we should consider no additional DOC was dosed in this experiment the biofilms were grown on plastic foils, placed in the water cycle of an aquaculture producing eels.

Structure and function of a nitrifying biofilm as determined by in situ hybridization and the use of microelectrodes.

Microprofiles of O2 and NO3- were measured in nitrifying biofilms from the trickling filter of an aquaculture water recirculation system. By use of a newly developed biosensor for NO3-, it was possible to avoid conventional interference from other ions. ...

www.ncbi.nlm.nih.gov

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC168290/pdf/624641.pdf

I could not find anywhere that they state how they calculated the denitrification rate that they report.

Anyone find it clarified?

FWIW, this paper used vey high ammonia (4.2 ppm) concentrations. I would be wary of using the gradients here to suggest much about a reef tank with ammonia levels closer to what is found in a cycled reef tank.

 

[Dan_P]

I could not find anywhere that they state how they calculated the denitrification rate that they report.

Anyone find it clarified?

p 4643, I think

 

[Lasse]

this paper used vey high ammonia (4.2 ppm) concentrations. I would be wary of using the gradients here to suggest much about a reef tank with ammonia levels closer to what is found in a cycled reef tank.

As information - a back calculation from my tank - when I stop dosing DOC show a rise with around 4 mg/L NO3 (0.9 NO3-N) a day. This means that my system' s input/production at least is around 1.2 mg/L NH4 (0.9 mg/L NH4 - N) a day. I have no clue how much the real input/production is - no way to measure how much NH4 that's will be direct into biomass. gassed out as NH3 or denitrified without extra DOC.

With these figures from a reef tank that is around 7 years old - I would not be surprised if my total load of NH3/NH4 in the tank is around 3 mg/L a day

Sincerely Lasse

 

[biom]

Now we are talking

Sincerely Lasse

Yes we are talking, but I am not sure what we are talking about .
Seriously I feel like we all are talking about different topics and jumping from one to another which is hard to follow (at least to me)

 

[Dan_P]

As information - a back calculation from my tank - when I stop dosing DOC show a rise with around 4 mg/L NO3 (0.9 NO3-N) a day. This means that my system' s input/production at least is around 1.2 mg/L NH4 (0.9 mg/L NH4 - N) a day. I have no clue how much the real input/production is - no way to measure how much NH4 that's will be direct into biomass. gassed out as NH3 or denitrified without extra DOC.

With these figures from a reef tank that is around 7 years old - I would not be surprised if my total load of NH3/NH4 in the tank is around 3 mg/L a day

Sincerely Lasse

This is useful information.

Just a small point. Randy points out that aquaria typically will not see 4 ppm of ammonia even if the 24 h total production is 4 ppm or an average of 0.16 ppm/h. At 0.16 ppm/h, the local accumulation of ammonia could be 0 ppm if the heterotrophic and autotrophic bacteria in your sand are well coordinated which they probably are.

 

[biom]

FWIW, this paper used vey high ammonia (4.2 ppm) concentrations. I would be wary of using the gradients here to suggest much about a reef tank with ammonia levels closer to what is found in a cycled reef tank.

We were talking if it is possible to have nitrification and denitrification in the same very thin biofilm. And from the paper it looks is possible.

 

[Randy Holmes-Farley]

p 4643, I think

I see the way they determined profiles, and the result of a denitrification calculation, but not how they actually calculated the denitrification rate, and most specifically, what assumptions they made.

i am concerned they assumed all nitrate lowering deep in the film was due to denitrification, which I would not accept without some considerable justification. If that is the case, how are they accounting for formation of N-containing biomolecules?

 

[Randy Holmes-Farley]

We were talking if it is possible to have nitrification and denitrification in the same very thin biofilm. And from the paper it looks is possible.

Possible, and happening in a reef tank are not the same, however. Artificially changing the situation by 100 fold (bulk ammonia concentration, and hence the input rate of nitrate to the deeper layers, and reduction of O2 within the biofilm) to do a test may lead to inaccurate extrapolation to real reef tank situations.

 

[Lasse]

We were talking if it is possible to have nitrification and denitrification in the same very thin biofilm. And from the paper it looks is possible.

The paper show much higher nitrification rate than denitrification rate - it means that the water column will rise in NO3 concentrations by time. The average nitrification rate was around 7 time higher than the denitrification rate (in µmol) IMO - the denitrification shown in this paper - even if it take place in our aquariums - are of no importance if your aim is to reduce your NO3 concentrations. The film will produce around 7 times more NO3 than it take away. I read the article as a prove that simultaneous nitrification/denitrification in the same biofilm are of no importance in our aquariums - it will add more than it take away

Sincerely Lasse

 

[Dan_P]

I see the way they determined profiles, and the result of a denitrification calculation, but not how they actually calculated the denitrification rate, and most specifically, what assumptions they made.

i am concerned they assumed all nitrate lowering deep in the film was due to denitrification, which I would not accept without some considerable justification. If that is the case, how are they accounting for formation of N-containing biomolecules?

I assume their denitrification rate is the measured rate of nitrate loss below 150 microns, but as you say, loss of nitrate can be caused by other mechanisms.