Looking for thoughts on organic carbon dosing and nitrate

[biom]

Yes but did you have zero nitrates after the bacterial cloud was gone?

No, nitrates were about 2.5-5 ppm that time.

 

[Lasse]

Why would it be from a slow growing one when there undoubtedly are fast growing ones around?

When fast growing facultative aerobs switch from using Oxygen (can´t use oxygen because they have use all oxygen in that spot for the fast growth and create an anaerobic environment) to using Nitrate in the cellular respiration - the growth slow down very much because the ATP gain from the glucose is around 19 times higher in aerobic respiration compared with the gain in anaerobic respiration (38 ATP compared with 2 ATP)

Once again There is a huge difference between assimilatory nitrate reduction (Nitrate used as a source for ammonium production in the bacteria (growth)) and dissimilatory nitrate reduction (denitrification) The first need a N/P ratio unique for each organism because the purpose for the assimilatory nitrate reduction is to get N for the growth of the organism. If P is limited for growth - no assimilatory nitrate reduction. Denitrification - as process - do not need any P because the purpose of this process is to create ATP (energy) for the organism and the waste is N2 that leave the organism. However some NO3 can be used in assimilatory nitrate reduction even for anaerobic growth but most of the NO3 will be used in the anaerobic respiration cycle.

The anammox process does not directly involve NO3 - its role in order to have NO3 low is that with help of NO2 directly convert NH4 to N2 gas - befor any NO3 has been formed in the nitrification process

IMO - the lag period is because it takes time to establish denitrification in a tank.

Sincerely Lasse

 

[Randy Holmes-Farley]

IMO - the lag period is because it takes time to establish denitrification in a tank.

That could be true, but is there any evidence that denitrification is actually the primary way nitrate declines when organic carbon dosing?

 

[HomebroodExotics]

I see now where my confusion comes from here. I also am thinking in terms of denitrification as an act the bacteria does by just existing as the main driver for denitrification as opposed to organisms using the nitrates solely for growth and reproduction.

If denitrification was solely performed by random organisms growing and reproducing then I would expect that my water would be cloudy constantly. Instead my denitrification comes from bacteria converting nitrates into nitrogen gas thats performed in biological media (I guess also for growing and reproducing as well). At least thats my thought process.

 

[GARRIGA]

That could be true, but is there any evidence that denitrification is actually the primary way nitrate declines when organic carbon dosing?

I’m starting to believe it has nothing to do with denitrification since it happens in tanks where an anoxic environment doesn’t appear to exist. Gotten to the point I don’t care why and just glad it’s an option.

 

[Lasse]

That could be true, but is there any evidence that denitrification is actually the primary way nitrate declines when organic carbon dosing?

As I try to explain in my long post - I do not see how a mass calculation can prove a bacterial assimilatory nitrate reduction of large amount of NO3 in organisms with an atomic N/P ration lower than 17:1 (between the indexfinger and the thumb) This based on the food input. Till this comes also the N input that we can´t control - N fixation. Short - there will be other nutrient limitation that stops the growth of the bacterial biomass before. Obvious - P will be consumed in the form of PO4 and even if you add P (as PO4) to the system - you by yourself rise the question about trace elements.

Note - I have not say that denitrification is always the major factor for nitrat reduction in our aquarium - the only thing I have pointed out is that if you in an aquarium with high NO3 concentrations (let us say above 5 mg/L) and normal PO4 concentrations (around 0.1 mg/L) dose DOC and get lag phase before NO3 drop significantly - its likely denitrification that have kicked in. This is because the denitrification process has low sensitivity for limitation of other compound than DOC and NO3.

DOC is essential in most system in order to get denitrification started in two major pathways. To create a large enough fast growing aerobic heterotrophic bacteria population that create oxygen depletion in certain spots and force the facultative aerobics to use NO3 as electron acceptor in the cellular respiration. Than this happens - the DOC´s importance swing to serve as electron donator in the anaerobic cellular respiration that use NO3 instead of O2.

Other type of assimilatory nitrate reduction (microalgae, corals, fungi and macroalgae) can play a major roll and be the most important nitrate reduction processes in many aquariums. If the population the organisms are large enough and that no other nutrient or trace element limitations occur. In a mass balance point of view - macroalgae is maybe the most interesting organism here - its internal atomic N/P ration is around 30 (correspond to a NO3/PO4 ratio (by weight) around 20 if NO3 is the only N source). The uptake ratio of N/P is higher than my calculated input ratio for both dry and natural food.

Also processes that reduce the NH4/NH3 concentration like heavy aeration at high pH and the anammox can reduce the net production of NO3 in the nitrification process, Direct uptake of NH4/NH3 by algae, corals and other photosynthetic organism reduce the NO3 production as well.

t is frequently claimed that it takes a long time (sometimes weeks) for organic carbon dosing to reduce nitrate.

Do folks believe that is true, and if it is, why would it be true?

Are most folks just starting to dose too slowly?

Bacterial number increase is sometimes cited as a reason, but why would it take that long?

If bacterial numbers increase is the reason, then where is the organic carbon going in the meantime? Accumulating? Being used somehow in a way that does not consume nitrate? What way is that?

Any thoughts are appreciated.

This was the question (my bold). My answer is that if there is high NO3 concentrations compared with PO4 concentrations in the start of DOC dosing and there is a lag period - is likely the denitrification that´s responsible for the reduction of NO3. This because the ratio of inputted atomic N and P together with internal N fixation exceeds the bacteria internal atomic ratio by far. If there is a too high atomic ratio between NO3-N and PO4-P - in the start - a growth of bacteria biomass can´t solve the problem by itself - its need other NO3-N export or/and an other P import pathway (dosing P)

Sincerely Lasse

 

[Randy Holmes-Farley]

If denitrification was solely performed by random organisms growing and reproducing then I would expect that my water would be cloudy constantly.

Why would the water be cloudy? There are lots of bacteria in the water whether you dose organic carbon or not, and I also would not assume that most of the aerobic growth and incorporation in bacteria is necessarily in the water column as opposed to benthic bacteria.

 

[Randy Holmes-Farley]

This was the question (my bold). My answer is that if there is high NO3 concentrations compared with PO4 concentrations in the start of DOC dosing and there is a lag period - is likely the denitrification that´s responsible for the reduction of NO3. This because the ratio of inputted atomic N and P together with internal N fixation exceeds the bacteria internal atomic ratio by far. If there is a too high atomic ratio between NO3-N and PO4-P - in the start - a growth of bacteria biomass can´t solve the problem by itself - its need other NO3-N export or/and an other P import pathway (dosing P)

I guess I am unconvinced that such ideas demonstrate that denitrification takes place. There is too large of a reservoir of phosphate bound to rock and sand in many aquaria to really say much about the net availability of nitrate and phosphate for organisms as those elements are consumed/incorporated into tissues.

 

[biom]

IMO there is high probability that denitrification is the main process for nitrate reduction after dosing organic carbon in a saltwater aquarium.
But I dont agree denitrification is a slow process by definition (and reason for the lag time) and is not always anaerobic.

Characterization of a halophilic heterotrophic nitrification–aerobic denitrification bacterium and its application on treatment of saline wastewater

A novel halophilic bacterium capable of heterotrophic nitrification–aerobic denitrification was isolated from marine sediments and identified as Vibri…

www.sciencedirect.com

From there with small redactions from my side for clarity:
To confirm the aerobic denitrification by halophilic strain Vibrio diabolicus SF16 (I like that name ), potassium nitrate was used as the nitrogen source and sodium acetate as DOC source. A significant decrease of NO3 -N was observed between 8 h and 16 h. After 48 h of cultivation, the NO3 -N concentration decreased from 136 mg/L to 0.39 mg/L, corresponding to a removal efficiency of 99.7 %, and the aerobic denitrification rate was 2.83 mg NO3 -N/L/h. Meanwhile, the NO2 -N concentrations increased rapidly between 8 h and 20 h, and then decreased rapidly until 40 h

OD 600 on the figure is bacterial growth and stand for optical density at 600nm

This is very close to what I've seen during my experiment.

 

[Lasse]

I guess I am unconvinced that such ideas demonstrate that denitrification takes place. There is too large of a reservoir of phosphate bound to rock and sand in many aquaria to really say much about the net availability of nitrate and phosphate for organisms as those elements are consumed/incorporated into tissues.

May so - but in that case you should have no lag phase and see an exponential growth of bacteria with a steady going down in NO3.

But I dont agree denitrification is a slow process by definition (and reason for the lag time) and is not always anaerobic.

The denitrification process is not slow in it self but it take time to establish the anaerobic environment that's most bacteria need in the classic denitrification process.

Yes there is "super" bacteria out there - but there is no evidence they are present in our systems - so I will stay with the classic denitrification pathway for the moment. However this up to date review - Role of heterotrophic aerobic denitrifying bacteria in nitrate removal from wastewater from 2020 do not role out the possibility that heterotrophic aerobic denitrifying bacteria can exist in our aquarium. If so - it could also be the reason for the log phase. This is highly specialized bacteria that may need some time for building up enough of biomass. Interesting in this case is that glucose and acetate seems to be the most effective carbon source in contras with the classic denitrification there ethanol have shown upp to be best,

By the way - these discussions is gold worth - they at least forcing myself to update my knowledge. The linked article is an easy-to-understand update on the state of knowledge regarding aerobic heterotroph denitrification but also provides an overview of the nitrogen cycle with an up-to-date overview of the nitrification process as well. I highly recommend the article

Note that in the previous post I combined dissimilatory and denitrification pathways as the same but this author use three different pathways for reduction of nitrate - assimilatory, dissimilatory or denitrification. See quote

Assimilatory nitrate reduction involves anabolic reactions, wherein nitrate is converted to biomass. Dissimilatory nitrate reduction to ammonium involves direct conversion of nitrate to ammonium, whereas denitrification is the stepwise reduction of nitrate to dinitrogen

Let me correct my self. I still convinced that the large NO3 reduction use of DOC can give is due to denitrification (not a assimilatory) pathways but I open for that it can be aerobic heterotrophic denitrification or/and the more classic anaerobic version.

Sincerely Lasse

 

[Randy Holmes-Farley]

May so - but in that case you should have no lag phase and see an exponential growth of bacteria with a steady going down in NO3.

Do we always see a lag? Not in overdose settings.

There are other possible reasons for a lag.

 

[HomebroodExotics]

Do we always see a lag? Not in overdose settings.

There are other possible reasons for a lag.

whats an overdose amount?

 

[Lasse]

My answer is that if there is high NO3 concentrations compared with PO4 concentrations in the start of DOC dosing and there is a lag period - is likely the denitrification that´s responsible for the reduction of NO3.

My bold - haven't say that it is always a lag period but IMO if it is a lag period - its likely denitrification that have kicked in. However I open to hear other reasons for a lag period.

Sincerely Lasse

 

[Randy Holmes-Farley]

whats an overdose amount?

In general, when I use that term it means any amount more than intended, but in this context, I simply mean a large amount, as in my post #218 in this thread, where water column turned " extremely cloudy can barely see into it" with bacteria in about 24 h.

That's not indicative of a lag, IMO, and suggests that bacteria were expanding at quite a rapid rate. It also indicates a substantial amount of aerobic nitrate incorporation.

Looking for thoughts on organic carbon dosing and nitrate

Corals in their natural environment are dissolved organic carbon (DOC) net positive. About 40% of the photosynthetically fixed carbon by zoox is excreted by the coral in the surrounding water as mucus. I would expect it is like this in the aquariums too. Corals will probably take some of the...

www.reef2reef.com

 

[HomebroodExotics]

In general, when I use that term it means any amount more than intended, but in this context, I simply mean a large amount, as in my post #218 in this thread, where water column turned " extremely cloudy can barely see into it" with bacteria in about 24 h.

That's not indicative of a lag, IMO, and suggests that bacteria were expanding at quite a rapid rate. It also indicates a substantial amount of aerobic nitrate incorporation.

Looking for thoughts on organic carbon dosing and nitrate

Corals in their natural environment are dissolved organic carbon (DOC) net positive. About 40% of the photosynthetically fixed carbon by zoox is excreted by the coral in the surrounding water as mucus. I would expect it is like this in the aquariums too. Corals will probably take some of the...

www.reef2reef.com

It's obvious that the bacteria cloud will consume some nitrates, but it doesn't consume all the nitrates. My complaint with that is why did the cloud of bacteria dissipate before all the nitrate was removed? Trace elements? Then why the cloud doesn't come back once trace elements are reintroduced? This is evidence for me that points to denitrification happening in media, which requires time to happen.

 

[Randy Holmes-Farley]

It's obvious that the bacteria cloud will consume some nitrates, but it doesn't consume all the nitrates. My complaint with that is why did the cloud of bacteria dissipate before all the nitrate was removed? Trace elements? Then why the cloud doesn't come back once trace elements are reintroduced? This is evidence for me that points to denitrification happening in media, which requires time to happen.

Which can mean the organic ran out before nitrate consumption was complete, or something else, such as a trace element or phosphate, became limiting to further growth. There's no reason to assume that nitrate, will be the limiting growth factor.

 

[HomebroodExotics]

Which can mean the organic ran out before nitrate consumption was complete, or something else, such as a trace element or phosphate, became limiting to further growth. There's no reason to assume that nitrate, will be the limiting growth factor.

Of course nitrate is not the limiting factor. Then what is? Any aquarium with greater than 1 nitrate should have a bacterial cloud though if we follow this same logic as long as there is no limiting growth factor. Or every single aquarium has a limiting growth factor that is the same until it’s magically not months later. That doesn’t make any sense. Especially for people that do lots of water changes. There should be no limiting factors. At least not limited any more than the start of the tank.

 

[Lasse]

Which can mean the organic ran out before nitrate consumption was complete, or something else, such as a trace element or phosphate, became limiting to further growth. There's no reason to assume that nitrate, will be the limiting growth factor.

Yes but still in tanks with high NO3 levels (over 50 mg/L) I have seen down going of phosphate but not any significant down going of the NO3. After around 3 - 4 weeks (without any WC. PO4 adding or so) but still the same DOC dose - a fast down going without any signs of cloudiness or raised amount of skimmate (large bacterial biomass) Clearly this fast down going has not been related to bacterial growth.

Sincerely Lasse

 

[Randy Holmes-Farley]

Of course nitrate is not the limiting factor. Then what is? Any aquarium with greater than 1 nitrate should have a bacterial cloud though if we follow this same logic as long as there is no limiting growth factor. Or every single aquarium has a limiting growth factor that is the same until it’s magically not months later. That doesn’t make any sense. Especially for people that do lots of water changes. There should be no limiting factors. At least not limited any more than the start of the tank.

I expect added organic is the limiting growth factor, except in overdose scenarios. That is how folks determine doses. It is limiting before dosing, and likely after.

 

[Lasse]

I expect added organic is the limiting growth factor, except in overdose scenarios. That is how folks determine doses. It is limiting before dosing, and likely after.

At last - we agree

DOC is the limited factor - its the reason why it works with adding DOC. When you have reach a dosing that control your PO4 (all inputs of it) you will still have a N input that probably exceed the atomic ratio of N and P in the organism responsible for the assimilative nitrat reduction (probably with exception of Macroalgae) And if you started with an high load of NO3 the problem with statement that bacterial assimilative nitrat reduction is the major pathway for NO3 reduction will be obvious. At least in system with high NO3 concentration already from the beginning. But clearly - in spite of the same DOC dose (the same concentration of PO4, DOC dosing and no WC) after a month or two something happens in many systems - NO3 starts to decline and that without any signs of a fast growth of bacterial biomass (cloudiness, more skimmate and so on)

The only logical explanation is that this is caused of something else than assimilative nitrat reduction (biomass growth) and I put my dime on denitrification

Sincerely Lasse