Looking for thoughts on organic carbon dosing and nitrate

[Max93]

They may well have consumed suspended bacteria, like other filter feeders. I had them too, and it may be a potential side effect in some cases, of organic carbon dosing and the subsequent rise in bacteria.

Very interesting point. They are literally everywhere. I’m working on finding some quarantined bumbleebee snails, so hopefully that will help

 

[Dan_P]

So I did some data mining from the last 3 pages of @Lasse build thread. And I already considered Lasse's setup to be a best possible case - but crunching the numbers looks impossibly good.
Like 2 moles of Carbon removes 1 mole of Nitrogen, good.

Left chart is where I took different stretches of Lasse's data where he did various set volumes of 8% ethanol added fro a few days at a time.
When he doesn't dose any, NO3 climbs at between 2.5 to 4 ppm NO3 per day.
When he doses 18mL/day through his sand, NO3 drops around 2.5-3ppm per day.
The amount dosed is in mL of 8% ethanol (I interpret this as like 1/5 vodka) into 310L system.
The right chart is me trying to convert all those to moles/L of Carbon and Nitrogen.
(I'm not even sure that data is theoretically possible. Maybe Lasse can spot my error)


@Dan_P data with dumping vinegar into the water was more in the real world, like 40 moles C per 1 mole NO3 removed.

If nitrate is being reduced under anaerobic conditions, the ethanol might just be a source of carbon for biomass not energy and the consumption rate lower.

 

[Lasse]

If nitrate is being reduced under anaerobic conditions, the ethanol might just be a source of carbon for biomass not energy and the consumption rate lower.

Nope - as I have said before - the DOC (in my case ethanol) is essential as electron donor for the metabolism during anaerobic environment and with NO3 as an electron acceptor in the electron transport chain - with other words denitrification. It is both - source for biomass growth (include even PO4 reducing) and as a electron donor during ATP production.

https://www.epa.gov/sites/default/files/2019-08/documents/external_carbon_surces_for_nitrogen_removal_fact_sheet_p100il8f.pdf

Here is a comparison between different DOC as electron donors in denitrification(PDF)

Sincerely Lasse

 

[Dan_P]

Nope - as I have said before - the DOC (in my case ethanol) is essential as electron donor for the metabolism during anaerobic environment and with NO3 as an electron acceptor in the electron transport chain - with other words denitrification. It is both - source for biomass growth (include even PO4 reducing) and as a electron donor during ATP production.

https://www.epa.gov/sites/default/files/2019-08/documents/external_carbon_surces_for_nitrogen_removal_fact_sheet_p100il8f.pdf

Here is a comparison between different DOC as electron donors in denitrification(PDF)

Sincerely Lasse

Just woke up and was about to correct myself. Thanks for the correction. You are running a denitrator in your sand bed, right?

 

[taricha]

I rechecked the numbers and this result still looks accurate.

I already considered Lasse's setup to be a best possible case - but crunching the numbers looks impossibly good.
Like 2 moles of Carbon removes 1 mole of Nitrogen, good.

Left chart is where I took different stretches of Lasse's data where he did various set volumes of 8% ethanol added fro a few days at a time.

putting it in more common terms. Lasse is getting NO3 reduction and control at ~10mL of 8% ethanol or the equivalent of 16mL vinegar in 80 gallons or 0.2 mL vinegar per gallon.


The slope of the above right graph ~0.5 moles of NO3 per mole of Carbon is actually possible - at least it's well within what's allowed by the below equation : up to 12 mole NO3 removed per 10 mole of Carbon added, or 1.2 NO3 per Carbon.

Here’s the balanced denitrification for ethanol.

12 NO3– + 5 CH3CH2OH + 12 H+ → 10 CO2 + 6 N2 + 21 H2O

Weird to think how different this is from NO3 as a nitrogen source. It's essentially using NO3 as a source of oxygen, and if you make conditions where you need the NO3 to oxidize your carbon source, then the bacteria can eat a lot of NO3 that way.

the DOC (in my case ethanol) is essential as electron donor for the metabolism during anaerobic environment and with NO3 as an electron acceptor in the electron transport chain - with other words denitrification.

You are running a denitrator in your sand bed, right?

Right. As I think about this - it's really different from what happens when we add vinegar or vodka to our tank water.
The conditions necessary for the denitrification equation is
1) low or lack of O2
2) deliver Carbon
3) present NO3
This doesn't sound hard - but you can't just inject vodka into your sand - you'd have to also push your NO3-containing water into that same sand with the ethanol - while not adding too fast so that there's a bunch of O2.

It is, in fact, turning the sand into a denitrification reactor.

No one should expect typical carbon dosing to look anything like this. If you want this result, check out methods like a methanol denitrator, or nitrate destroyer etc.

 

[Randy Holmes-Farley Verified Community Expert]

This doesn't sound hard - but you can't just inject vodka into your sand - you'd have to also push your NO3-containing water into that same sand with the ethanol - while not adding too fast so that there's a bunch of O2.

IMO, that last sentence is why we do not get more denitrification in a normal sand bed or pores into live rock. It's really challenging to imagine how lots of NO3- and ethanol diffuses in, but O2 does not.

Even in Lasse's situation, I expect that a bunch of the ethanol is consumed aerobically in the sand, depleting the O2, and then denitrification can begin.

But for that to happen, one has to have a molar amount of ethanol that is high relative to O2. Just a little ethanol looking for a little denitrification may fail for that reason, leaving only aerobic metabolism and no denitrification.

 

[jda]

The rate just has to be stable and the oxic bacteria will develop/multiply to consume the oxygen. The oxygen free water can continue into the process.

Adequate sand beds are quite good at reducing no3 if maintained but also not disturbed. It is no stretch to me to imagine even a small bit of ethanol helping deplete o2 more rapidly, or even driving denitrification. What I struggle with is why it is necessary since my sandbeds don't need any ethanol to keep no3 at just barely a trace.

Back in the olden days, a particular doctor of chemistry used to argue that bioballs possibly did contribute to higher no3 levels since they did not allow no2 production so close to those anoxic regions in sand and rock. Would that same principle of proximity not apply here?

 

[Randy Holmes-Farley Verified Community Expert]

Back in the olden days, a particular doctor of chemistry used to argue that bioballs possibly did contribute to higher no3 levels since they did not allow no2 production so close to those anoxic regions in sand and rock. Would that same principle of proximity not apply here?

I still believe that is one of the reasons nitrate dropped in some tanks when bioballs were removed. I just do not think we have much data on how much denitrification actually takes place in typical aquaria.

 

[jda]

In so much as we don't really have much data on anything started to get complex, I agree. Dr. Ron did have some pretty good data... and some was posted on WWM. I have a few books somewhere that probably have some good stuff in them, but WWM is a disaster to browse through even though I never seemed to mind when it was en vogue.

To my question a while back on why ethanol is necessary for Lasse, but not others, it got me thinking. I seem to remember him using a large tower of aerobic material for filtration... or at least he showed a design for one. I wonder if use of this tower with with no2/no3 production so far from the plenum is one reason why the sandbed is not as efficient as others without the ethanol.

It is not hard for me to imagine that denitrification can be near-total since I have seen it in my own home, read about it for decades and shared similar experiences with many who did not let their sand beds decay with too much inert junk that slows/stops movement, saturated with po4 or disturbed all the time... not to mention a very close proximity to where the no3 is manufactured.

 

[Lasse]

I wonder if use of this tower with with no2/no3 production so far from the plenum is one reason why the sandbed is not as efficient as others without the ethanol.

Nope

I´ll think that my sand bed is not old enough to be self-sufficient with DOC for donor proposes. The denitrification - the classic - need DOC as donors.

But there could be other explanations why some tanks with old sand beds are free from NO3. Recently another process was discovered that transfer NH4/NH3 directly to N2 - the anammox process

https://en.wikipedia.org/wiki/Anammox.

Sincerely Lasse

 

[Randy Holmes-Farley Verified Community Expert]

Nope

I´ll think that my sand bed is not old enough to be self-sufficient with DOC for donor proposes. The denitrification - the classic - need DOC as donors.

But there could be other explanations why some tanks with old sand beds are free from NO3. Recently another process was discovered that transfer NH4/NH3 directly to N2 - the anammox process

https://en.wikipedia.org/wiki/Anammox.

Sincerely Lasse

Yes, I agree that the annamox process may certainly be happening in our sediments:

NH4+ + NO2- → N2 + 2H2O

It doesn't need organic carbon, but it does need both nitrite and ammonia. If the nitrite is being made in place from ammonia, then it also needs O2.

 

[SDchris]

There are some other assumptions being made.
It's mainly assumed that there is an increase in free floating bacteria that are skimmed out, with a change in skimmate cited as a reason. Is it possible that the change in colour and appearance is from the carbon source driving bacterial growth in the skimmer neck / waste collection cup directly? and not an increase in the amount of organics being removal.
In my case skimmers have been ineffective in controlling visible water column bacterial blooms, where as turning on a UV has. With the skimmer having X 4 higher turn over.

 

[taricha]

It's mainly assumed that there is an increase in free floating bacteria that are skimmed out, with a change in skimmate cited as a reason.

Right. This isn't exclusively true.
Carbon can feed heterotroph bacteria in the water (large enough doses cause visible cloudiness), but also on the sand/surfaces, and some sources of Carbon are widely used enough that they are consumed by algae and corals also.
Bacterial blooms in the water can produce a lot of material that is easily skimmed out, but also like you said some cloudy bacteria persist even with aggressive skimming, so not all waterborne bacteria are easily skimmed.
I suspect - but don't have the data to prove - that things like acetate and glucose are taken up by everything, including corals and algae, while things like alcohols, (methanol/ethanol) are more specifically available to bacteria than algae and coral.
I don't know how to think about biopolymers in this regard, like bio pellets or alginate. I think that they get chopped up into tiny digestible bits by bacteria, but after that I don't know who can eat the tiny chopped up bits. Maybe they then become available to everyone like glucose or acetate?

 

[SDchris]

I suspect - but don't have the data to prove - that things like acetate and glucose are taken up by everything, including corals and algae, while things like alcohols, (methanol/ethanol) are more specifically available to bacteria than algae and coral.

Seems a reasonable hypothesis.
Going back to the observed differences between adding glucose vs sucrose, or glucose vs fructose. We know coral can metabolise fructose as they contain fructokinase, but is it mainly for energy or something more signalling like? which might make it very dose dependent.
Maybe going a little off tangent...

 

[Randy Holmes-Farley Verified Community Expert]

Seems a reasonable hypothesis.
Going back to the observed differences between adding glucose vs sucrose, or glucose vs fructose. We know coral can metabolise fructose as they contain fructokinase, but is it mainly for energy or something more signalling like? which might make it very dose dependent.
Maybe going a little off tangent...

Certainly one might speculate that certain organic molecules have impacts other than simple metabolism, but I would be wary of inferring that an organism can and does take up molecules from the water just because it has an enzyme capable of breaking it down. Those may primarily relate to molecules made internally.

 

[machome79]

It 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.

I think the answers to your questions are simple. diversity. no two tanks are the same, different sources of bacteria, flora, rock, sand, creatures, corals, foods, water sources,etc, are the same. there is no benchmark to go from.every tank is different. you may use the same methods as me but produce completely different results.

 

[Dan_P]

I think the answers to your questions are simple. diversity. no two tanks are the same, different sources of bacteria, flora, rock, sand, creatures, corals, foods, water sources,etc, are the same. there is no benchmark to go from.every tank is different. you may use the same methods as me but produce completely different results.

I wonder though.

The truism that no two tanks are the same is probably an accurate statement at some level. So, no argument here. What I would like to put forward is what might be equally valid is that no two aquarists are the same. Given two identical aquaria (probably impossible) but different aquarists, the systems will likely perform differently. I would say in answer to the questions, first interrogate the aquarist, then the aquarium. Interesting thinking and perspectives of humans might explain much

 

[areefer01]

I wonder though.

The truism that no two tanks are the same is probably an accurate statement at some level. So, no argument here. What I would like to put forward is what might be equally valid is that no two aquarists are the same. Given two identical aquaria (probably impossible) but different aquarists, the systems will likely perform differently. I would say in answer to the questions, first interrogate the aquarist, then the aquarium. Interesting thinking and perspectives of humans might explain much

Husbandry, methods, consistency, practice?

 

[Randy Holmes-Farley Verified Community Expert]

I think the answers to your questions are simple. diversity. no two tanks are the same, different sources of bacteria, flora, rock, sand, creatures, corals, foods, water sources,etc, are the same. there is no benchmark to go from.every tank is different. you may use the same methods as me but produce completely different results.

I'm not sure how diversity causes the effect I'm asking about.

What you have to propose is that, for some reason, lots of organic carbon needs to be metabolized before nitrate and phosphate is lowered. That requires some process. Just saying diversity doesn't propose any actual process.

What would that process be, in any organism, in any tank, and why would it dominate over simple organism growth, or ordinary denitrification?

 

[machome79]

I'm not sure how diversity causes the effect I'm asking about.

What you have to propose is that, for some reason, lots of organic carbon needs to be metabolized before nitrate and phosphate is lowered. That requires some process. Just saying diversity doesn't propose any actual process.

What would that process be, in any organism, in any tank, and why would it dominate over simple organism growth, or ordinary denitrification?

I was more referring to " varibles" to affect a process. I don't think we have enough info about the denitrification in a tank yet. I wish I time and the proper equipment to observe . what else is happening that we cannot test for?