Nitrate Consumption Rates And Stoichiometry For Organic Carbon Dosing

[Dan_P]

In a previous post I demonstrated the use of a 2 liter aquarium to study carbon dosing with vinegar (acetic acid) and ethanol.

Carbon Dosing A Model Aquarium

Two posts last year resulted in my interest in gaining a deeper understanding of how carbon dosing worked: @Miami Reef published the new organic carbon dosing schedule https://www.reef2reef.com/threads/new-vodka-and-vinegar-dosing-charts.1024056/ and @Randy Holmes-Farley posted a question...

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Following the hobby protocol of weekly increases of the daily dose, nitrate was consumed as expected, even though the aquarium was not filtered nor attached to a skimmer. Ethanol dosing provided a greater reduction of nitrate than acetic acid (vinegar) on a molar basis (same number of molecules). Phosphate was also consumed at roughly 0.1 ppm per ppm of nitrate. In this post I want to share the results of the next study designed to determine how quickly nitrate is consumed after vinegar or ethanol is dosed. All experiments were performed at room temperature (20-23 C). Nitrate was measured with the Hanna low range nitrate Checker, phosphate with the Hanna low range Checker and oxygen with the Hanna oxygen test kit (modified Winkler titration).

In this study I used 150 mL BOD bottles, glass stoppered bottles designed to study oxygen consumption, instead of magnetically stirred 2 liter aquaria. The aquarium water used in the experiment was pre-dosed with either vinegar or ethanol and stirred for 24 hours to get past the lag phase in bacteria growth (a discovery for another post). The post lag phase water was then divided in half. One portion filled four BOD bottles (control), the other portion was dosed with either vinegar or ethanol before filling four additional BOD bottles (treatment). The size of the ethanol dose was scaled to obtain the same size nitrate consumption as vinegar dosed at 0.5 mL/gallon aquarium water. Here is the data.

The two charts show how quickly nitrate is consumed with either vinegar or ethanol, and equally interesting how fast oxygen is removed from the water. The good news is that oxygen consumption is smaller than what would be predicted from complete oxidation of the dose (100% respired), 7.4 ppm vs 1.5 for ethanol and 3.5 ppm for acetic acid. The table below summarizes the total consumptions of nitrate, phosphate and oxygen. To convert to ppm, multiply the entry by 62 for nitrate, 95 for phosphate and 32 for oxygen. The “organic residual”, the difference between the amount of organic dosed and the amount oxidized (calculated from the oxygen used and stoichiometry of the oxidation reaction), gives us an idea of how much of the dose could have gone into biomass. Phosphate consumption looks like it is very closely related to oxygen use.

What are the implications of this data for carbon dosing aquaria? The concern about oxygen depletion remains, especially for a vinegar doses nearing 0.75 mL/gallon where the system’s oxygen could be nearly depleted quickly. From an oxygen depletion perspective, ethanol is safer. I wonder whether oxygen depletion is one reason why coral and fish seem to be affected by carbon dosing. As for phosphate removal, about 0.1 ppm is removed with every 1 ppm of nitrate. That rate would be considered wonderful if large amounts of phosphate weren’t being released by aragonite surfaces and hiding this removal rate in aquarium carbon dosing.

What’s next? I feel that we still don’t have all the reasons for carbon dosing seeming to fail in practice. Unraveling that mystery should be fun.

 

[Rick Mathew]

In a previous post I demonstrated the use of a 2 liter aquarium to study carbon dosing with vinegar (acetic acid) and ethanol.

Carbon Dosing A Model Aquarium

Two posts last year resulted in my interest in gaining a deeper understanding of how carbon dosing worked: @Miami Reef published the new organic carbon dosing schedule https://www.reef2reef.com/threads/new-vodka-and-vinegar-dosing-charts.1024056/ and @Randy Holmes-Farley posted a question...

www.reef2reef.com

Following the hobby protocol of weekly increases of the daily dose, nitrate was consumed as expected, even though the aquarium was not filtered nor attached to a skimmer. Ethanol dosing provided a greater reduction of nitrate than acetic acid (vinegar) on a molar basis (same number of molecules). Phosphate was also consumed at roughly 0.1 ppm per ppm of nitrate. In this post I want to share the results of the next study designed to determine how quickly nitrate is consumed after vinegar or ethanol is dosed. All experiments were performed at room temperature (20-23 C). Nitrate was measured with the Hanna low range nitrate Checker, phosphate with the Hanna low range Checker and oxygen with the Hanna oxygen test kit (modified Winkler titration).

In this study I used 150 mL BOD bottles, glass stoppered bottles designed to study oxygen consumption, instead of magnetically stirred 2 liter aquaria. The aquarium water used in the experiment was pre-dosed with either vinegar or ethanol and stirred for 24 hours to get past the lag phase in bacteria growth (a discovery for another post). The post lag phase water was then divided in half. One portion filled four BOD bottles (control), the other portion was dosed with either vinegar or ethanol before filling four additional BOD bottles (treatment). The size of the ethanol dose was scaled to obtain the same size nitrate consumption as vinegar dosed at 0.5 mL/gallon aquarium water. Here is the data.

The two charts show how quickly nitrate is consumed with either vinegar or ethanol, and equally interesting how fast oxygen is removed from the water. The good news is that oxygen consumption is smaller than what would be predicted from complete oxidation of the dose (100% respired), 7.4 ppm vs 1.5 for ethanol and 3.5 ppm for acetic acid. The table below summarizes the total consumptions of nitrate, phosphate and oxygen. To convert to ppm, multiply the entry by 62 for nitrate, 95 for phosphate and 32 for oxygen. The “organic residual”, the difference between the amount of organic dosed and the amount oxidized (calculated from the oxygen used and stoichiometry of the oxidation reaction), gives us an idea of how much of the dose could have gone into biomass. Phosphate consumption looks like it is very closely related to oxygen use.

What are the implications of this data for carbon dosing aquaria? The concern about oxygen depletion remains, especially for a vinegar doses nearing 0.75 mL/gallon where the system’s oxygen could be nearly depleted quickly. From an oxygen depletion perspective, ethanol is safer. I wonder whether oxygen depletion is one reason why coral and fish seem to be affected by carbon dosing. As for phosphate removal, about 0.1 ppm is removed with every 1 ppm of nitrate. That rate would be considered wonderful if large amounts of phosphate weren’t being released by aragonite surfaces and hiding this removal rate in aquarium carbon dosing.

What’s next? I feel that we still don’t have all the reasons for carbon dosing seeming to fail in practice. Unraveling that mystery should be fun.

Very nice Dan...Well done!

 

[Dan_P]

Very nice Dan...Well done!

Thanks Rick!

 

[ReneReef]

Great work Dan!

As to what’s next…
I think it would be nice to see if the carbon sources marketed as “slow” or “slower” or something the like are actually slower acting and by how much. And how they hold up with regards to oxygen consumption.

Things like the polyalcohol in Tropic Marin Elimi NP or the algae/plant based biopolymers in Reef Actif.

 

[Randy Holmes-Farley]

From an oxygen depletion perspective, ethanol is safer.

Any hypothesis of why the viengar O2 drop is more? I'm suspicious that the O2 consumed does not seem to match the expectation that vinegar uses less O2.

 

[BeanAnimal]

You lost me at

Stoichiometry​

I can't speak to the contents of the thread -- the word in the title scared me and I am typing this with one eye open, to be sure I don't see what is above.

The word evokes feelings of frustration, if not nightmares from a computer science major - who's curriculum was under the math and science department where Chem I and II and Organic Chem were required... well that and Discrete Mathematics, Calc I and II, probability and statistics...

 

[Randy Holmes-Farley]

You lost me at

Stoichiometry​

I can't speak to the contents of the thread -- the word in the title scared me and I am typing this with one eye open, to be sure I don't see what is above.

The word evokes feelings of frustration, if not nightmares from a computer science major - who's curriculum was under the math and science department where Chem I and II and Organic Chem were required... well that and Discrete Mathematics, Calc I and II, discrete mathematics, probability and statistics...

lol

Had dinner with a mathematician a couple of nights ago. My wife asked him what kind of math another mathematician friend of his did. The answer did not clarify anything for us. lol

 

[BeanAnimal]

Not to derail this entire thread, but the highlight of organic chem class was the pair of lab partners next to me dropping a bottle of alcohol onto the table, where it shattered and was ignited by our bunsen burner...

Roughly 2 square feet of the 12' long, two sided lab counter was on fire, as was the entire length of the sink trough. Not a big fire by any means, just a few inches high and visibly blue on the black counter and down the length of the 12' sink trough. Not a big deal by any stretch of the imagination unless you are panic type... I took a step back and told my lab partner to move her notebook, but not to worry, as it

The professor calmly says, "It's oka, everyone just take a step back, nothing to worry about", somebody pulled the fire alarm. The overhead stobes began flashing and the siren wailing....

At almost the same time two students yanked the fire blanket roll from its spring loaded spool, breaking the fancy cover....

As the fire alarm begins to wail, the girl who dropped the container, in some kind of odd delayed understanding of reality -- starts screaming "fire fire fire... ohhhh myyyy god ohhhhh my god fire fire fire " as she is doing some kind of funky panic dance in the same spot she was standing when she dropped the bottle.

Meanwhile her lab partner has retrieved the large fire extinguisher and as the professor calmly says "Do not discharge that.... " the extinguisher is discharged. sending broken glass, everyone else's notebooks, experiments and bunsen burners (still aflame) tumbling.

The professor simply turns off the valve at the end of the desk, killing the bunsen burners and says "please nobody move, there is glass @$@# everywhere".

Ohh.. and the trough was still aflame, as fire extinguisher boy pretty much hit everything but the fire..

10-12 seconds of absolutely amazing mayhem that -- like anything that amazing played out in super slo-mo in real time. None of that helped me get a good grade.

 

[Randy Holmes-Farley]

Not to derail this entire thread, but the highlight of organic chem class was the pair of lab partners next to me dropping a bottle of alcohol onto the table, where it shattered and was ignited by our bunsen burner...

Roughly 2 square feet of the 12' long, two sided lab counter was on fire, as was the entire length of the sink trough. Not a big fire by any means, just a few inches high and visibly blue on the black counter and down the length of the 12' sink trough. Not a big deal by any stretch of the imagination unless you are panic type... I took a step back and told my lab partner to move her notebook, but not to worry, as it

The professor calmly says, "It's oka, everyone just take a step back, nothing to worry about", somebody pulled the fire alarm. The overhead stobes began flashing and the siren wailing....

At almost the same time two students yanked the fire blanket roll from its spring loaded spool, breaking the fancy cover....

As the fire alarm begins to wail, the girl who dropped the container, in some kind of odd delayed understanding of reality -- starts screaming "fire fire fire... ohhhh myyyy god ohhhhh my god fire fire fire " as she is doing some kind of funky panic dance in the same spot she was standing when she dropped the bottle.

Meanwhile her lab partner has retrieved the large fire extinguisher and as the professor calmly says "Do not discharge that.... " the extinguisher is discharged. sending broken glass, everyone else's notebooks, experiments and bunsen burners (still aflame) tumbling.

The professor simply turns off the valve at the end of the desk, killing the bunsen burners and says "please nobody move, there is glass @$@# everywhere".

Ohh.. and the trough was still aflame, as fire extinguisher boy pretty much hit everything but the fire..

10-12 seconds of absolutely amazing mayhem that -- like anything that amazing played out in super slo-mo in real time. None of that helped me get a good grade.

Hilarious. And very telling whether you can count on people in a crisis.

 

[Dan_P]

Great work Dan!

As to what’s next…
I think it would be nice to see if the carbon sources marketed as “slow” or “slower” or something the like are actually slower acting and by how much. And how they hold up with regards to oxygen consumption.

Things like the polyalcohol in Tropic Marin Elimi NP or the algae/plant based biopolymers in Reef Actif.

Thanks.

If we can identify the polymers in these products, understanding what slow means might be doable. I suppose studying the product itself might be an alternative. I will give it some thought.

 

[Dan_P]

You lost me at

Stoichiometry​

I can't speak to the contents of the thread -- the word in the title scared me and I am typing this with one eye open, to be sure I don't see what is above.

The word evokes feelings of frustration, if not nightmares from a computer science major - who's curriculum was under the math and science department where Chem I and II and Organic Chem were required... well that and Discrete Mathematics, Calc I and II, probability and statistics...

I will be more sensitive to others’ feelings next time

 

[Dan_P]

Any hypothesis of why the viengar O2 drop is more? I'm suspicious that the O2 consumed does not seem to match the expectation that vinegar uses less O2.

I went

 

[taricha]

You lost me at

Stoichiometry​

I can't speak to the contents of the thread -- the word in the title scared me and I am typing this with one eye open, to be sure I don't see what is above.

@Dan_P just talking about his bacterias favorite Redfield Ratios.
Lol. Sorry. couldn't help it.

 

[BeanAnimal]

Hilarious. And very telling whether you can count on people in a crisis.

I worked in underground coal and rock mines for a rather long time, mostly in emergency (fire, flood, massive roof fall and unstable conditions) and have seen and been part of some wild, some scary and some very unfortunate events over those years, as well as out here in the daylight... You are absolutely correct. You don't know who is going to flake or who is going to buckle down and get it done until it hits the fan. Sometimes the folks who you could swear are going to be the heroes are the one's in shock or adding to the chaos and the ones you are sure to be useless are the calm and collected life savers.

At this juncture, I will see my way to the door that I came in, and let you lab types discuss lab things.

 

[Dan_P]

Any hypothesis of why the viengar O2 drop is more? I'm suspicious that the O2 consumed does not seem to match the expectation that vinegar uses less O2.

Try this.

I set the doses of acetic acid and ethanol to cause an equi-molar consumption of nitrate. As a first approximation, the energy requirement for bacteria growth is the same regardless of the carbon source. Since acetic acid has a lower energy content than ethanol, a great amount of acetic acid needs to be oxidized. Basing energy content only on the number of oxygens needed, I would say ethanol has 1.5 times more energy content than acetic acid, and therefore, only 2/3 the amount of ethanol is needed compared to acetic acid to supply the same energy. Directionally, this is what I observed but my calculated ratio of ethanol oxidized vs acetic acid is only about 1/3.

 

[Reefering1]

I would say ethanol has 1.5 times more energy content than acetic acid, and therefore, only 2/3 the amount of ethanol is needed compared to acetic acid to supply the same energy.

This seems to conflict the seemingly accepted 8x potency ratio. I always thought 5ml of vodka is about equivalent to 40ml of vinegar ?

 

[Dan_P]

This seems to conflict the seemingly accepted 8x potency ratio. I always thought 5ml of vodka is about equivalent to 40ml of vinegar ?

The equivalency that you are referring to is based on the concentration of acetic acid in vinegar and ethanol in vodka, 5% versus 40%, respectively. I am referring to the energy content of acetic acid and ethanol. The energy from combustion or respiration of ethanol is about 1.5 greater than that of acetic acid.

 

[Reefering1]

The equivalency that you are referring to is based on the concentration of acetic acid in vinegar and ethanol in vodka, 5% versus 40%, respectively. I am referring to the energy content of acetic acid and ethanol. The energy from combustion or respiration of ethanol is about 1.5 greater than that of acetic acid.

Understood(I think)..

 

[BeanAnimal]

What’s next? I feel that we still don’t have all the reasons for carbon dosing seeming to fail in practice. Unraveling that mystery should be fun.

While I do understand why people carbon dose, and the basic mechanisms at play, I was not aware that it "failed" in practice.

Can you put context to that form me? I am genuinely interested in (after all of these years) getting up to speed and considering if this is something that I will want to try or need.

 

[Dan_P]

While I do understand why people carbon dose, and the basic mechanisms at play, I was not aware that it "failed" in practice.

Can you put context to that form me? I am genuinely interested in (after all of these years) getting up to speed and considering if this is something that I will want to try or need.

I used the word “fail” which might have been too strong or misleading. There are occasional posts about carbon dosing taking too long or ceasing to work. Here’e Randy’s post to gather thoughts on the subject

Looking for thoughts on organic carbon dosing and nitrate

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...

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There were times during my small scale studies that I would have said my carbon dosing wasn’t working and it is repeatable. I need to understand why before I add to the discussion.