Sulphur in the reefaquarium

[Belgian Anthias]

In a normal aquarium without dosing and bio-filter: nitrification depletes alk but when that process takes place in a nitrifying biofilm the film will by nature also remove nitrogen due to the high oxygen consumption, about 16% of the nitrate production, which means each cycle +- 16 % of the nitrogen may be exported, without doing a thing. ( some claim a nitrifying bio-filter produces nitrogen!?)
If the nitrifying bio-film grows on a base of carbon carbonate most carbon will be retrieved from of the substrate dissolved by the acids . When growing on a base of carbon carbonate mixed with elemental sulphur more nitrogen gas N2 will be produced by the BADES process and exported, more accids will be produced, more carbon will be retrieved from the substrate dissolved by the acids. The effect on alk in the water column for both nitrification and dentrification will be minimal. Calcium and some sulphate is produced. Depending on the used substrate minerals are added, useful for calcification.
Each internal cycle of nitrogen, production, nitrification, consumption, production, nitrification a lot of the nitrogen will effectively be exported, this way restoring the nutrient balance as only nitrogen over-production considered not needed may be removed. Without doing a thing, just by nature! Naturally when no supplemental nitrogen is added. if the addition of nitrogen is adjusted to the removal rate, or vice versa, the removal rate to the addition, nitrate will not build up. One is able to manage both sides, the removal rate and the addition rate.

If all of the above is correct, the next question may be: why most reefers do not use a bio-filter?

 

[Dan_P]

Uh, no.

The conversion of the initial ammonia (it is ammonia, not ammonium) waste from organic metabolism into ammonia takes up alkalinity.
The use of that ammonium to remake organic molecules gives back the exact amont of alk.

It is a round trip from organics to ammonia to organics again. There's no way round trip processes can add or remove alkalinity.

Got it!

 

[Dan_P]

Sorry, No. That is incorrect.

I agree with the equations in your reference, and they are the same ones that I often use my articles. But you have misunderstood the processes involved. There is no net consumption of alkalinity.

Ebling et Al 2006:

https://cals.arizona.edu/azaqua/ista/ISTA7/RecircWorkshop/Workshop PP & Misc Papers Adobe 2006/7 Biofiltration/Microbial Floc Systems/2006 Aquaculture Stoichiometry of photo-auto-hetero - Ebeling.pdf

Equation 16 shows:


NH4+ + 1:18 C6H12O6 + HCO3- = 2:06 O2 --> C5H7O2N + 6:06 H2O + 3:07 CO2

" This equation predicts that for every g of ammonia– nitrogen converted to microbial biomass, 4.71 g of dissolved oxygen and 3.57 g of alkalinity (0.86 g inorganic carbon) and 15.17 g carbohydrates (6.07 g organic carbon) are consumed. Also 8.07 g of microbial biomass (4.29 g organic carbon) and 9.65 g of CO2 (2.63 g inorganic carbon) are produced"

This seems, at a first glance, to be consuming one unit of alkalinity (HCO3-) for each ammonia consumed), but that does not hold up to a deeper understanding of the processes involved.

The thing that you (and perhaps the author) are neglecting is that the nitrogen compound that is the product of metabolism by fish and other organisms is NOT NH4+. It is NH3.

The metabolism reaction is exactly the reverse of equation 3 in your reference. The product of the metabolism of organic matter with nitrogen in it is NH3. Of course, the reaction can be written as if it is NH4+, but when you do that, you necessarily produce alkalinity. That is what the reverse of equation 3 actually shows. Production of NH3 and then combination of that with some of the CO2:

NH3 + H2CO3 ---> NH4+ + HCO3-

And the reverse of equation 3 shows this "production" of HCO3- explicitly. Same for phosphate.

Consequently, the overall round trip from fish food to ammonia to production of biomass by consumption of ammonia to biomass formation with organic carbon has NO NET EFFECT ON ALKALINITY.

The same is true if you convert the ammonia along the way to nitrate. The overall round trip from fish food to ammonia to nitrate to production of biomass by consumption of nitrate to biomass formation with organic carbon has NO NET EFFECT ON ALKALINITY.

Thanks!

 

[purp]

I was hoping we could revisit this today through a modern technological lense. With the ubiquity of alkalinity monitoring (and dosing) is this method, where we acknowledge that alkalinity is depleted, more acceptable because we can control and measure the alk more closely? Does it negate the need for the CaCO3 piece which leads to increasing Ca?

 

[Dan_P]

I was hoping we could revisit this today through a modern technological lense. With the ubiquity of alkalinity monitoring (and dosing) is this method, where we acknowledge that alkalinity is depleted, more acceptable because we can control and measure the alk more closely? Does it negate the need for the CaCO3 piece which leads to increasing Ca?

Good question.

I wonder how much per day a sulfur reactor depletes of alkalinity? If it is small, then the consequence is a tweak to the daily dose if no CaCO3 is mixed with the sulfur. Of course, if it is small, not much calcium is released. I cannot remember anyone posting a rate estimate.

 

[purp]

i should slog through this for a refresher in marine geochemistry, but maybe @Randy Holmes-Farley is better suited to do it without error

 

[Belgian Anthias]

Concerning an anoxic kept sulfur denitrator without calcium carbonate media the alkalinity consumption may be estimated, taking in account also a bit off nitrification and aerobic remineralization takes place ( +- 6ppm oxygen must be consumed) Part of the denitrification capacity may be heterotrophic ( <16%), a bit of the nitrate entered may leave as ammonia due to DNRA. In such a reactor also a lot of HS may be produced due to sulfate reduction, HS which is used for reducing nitrate. Alkalinity is used as a carbon source. The production of H+ and SO4 will influence pH and total alkalinity.
Autotrophic denitrification on elemental sulfur lowers alkalinity by 4.5 mg of CaCO3 per mg of NO3 reduced to N. (Sengupta2006) ref: http://www.baharini.eu/baharini/dok...ie:stikstofkringloop#autotrofe_denitrificatie.
In practice, it depends on heterotrophic activities ( organic carbon availability) and the Nitrate/DO ratio in the influent, the flow rate.
A sulfur denitrator aims at 0 nitrates in the effluent. Bad flow management may cause nitrate needed for HS removal may not be available wich makes such a reactor very sensitive to human errors. Bad management may lead to a high sulfate reduction rate.

Influent nitrate content minus effluent nitrate content ( after aeration) x daily flow x 75% may be a good estimation for using BADES without any calcium carbonate substrate, for calculating and predicting SO4 production and alkalinity consumption. pH will be affected by H+ production.

If enough calcium carbonate is used such formula can be used to estimate the calcium production only.

For a BADESS, total alkalinity consumption may be considered to be neglectable and no H+ leaves the filter, pH is buffered.
Calculating and or estimating calcium production is more difficult as calcium and nitrate may be produced by the nitrification process in the filter. Ammonium nitrified in the filter may increase the calcium production.
A BADES reactor is NOT kept anoxic. Using BADES aiming at 0 nitrates in the effluent is not a necessity and avoidable.
A BADESS can operate at a high flow rate which makes effective removal of a high daily nitrate overproduction possible while maintaining a low nitrate level, ( one can only remove what is present)
The effluent still may contain oxygen, it works fine with an effluent DO of 2ppm. ref: http://www.baharini.eu/baharini/doku.php?id=en:badess:start
If enough calcium carbonate is mixed with the sulfur and the effluent of the reactor is aerated, pH and alkalinity in the aquarium will not be affected much by using a BADES reactor, Ca and HCO3 may be produced ( Zhang) The BADES process will be able to use the substrate as a carbon source, alkalinity is not used.
According to the Zhang formula, approximately 1.76 mg Ca is produced per 3.1 mg NO3 removed by BADES.
If 10 mg of nitrate is removed by BADES, a maximum of 5.68 mg of calcium can be added. Theoretically, using a BADESS, this will be more due to the nitrification capacity of a BADES System. In the aquarium less alkalinity will be consumed due to nitrification. ref : http://www.baharini.eu/baharini/doku.php?id=nl:badess:theorie:de_neveneffecten#alkaliniteit
Nitrification taking place on a substrate of calcium carbonate may dissolve 1 mol CaCO3 for each mol NH4-N transformed into NO3, ( Green2001) ref: http://www.baharini.eu/baharini/dok...hemie:biofilm#kalk_als_drager_voor_de_biofilm The carbonates are used as a carbon source, the nitrification process will not consume alkalinity. Calcium is produced.

Using enough calcium carbonate media will also limit the SO4 production. ref: http://www.baharini.eu/baharini/doku.php?id=nl:badess:theorie:de_neveneffecten
Big systems use separate reactors for the calcium media. ref: http://www.baharini.eu/baharini/doku.php?id=en:badess:bades:maao&rev=1580489412

Is the calcium production of a BADESS considered to be positive or negative?

 

[ca1ore]

FWIW, on my 600 gallon system, I have to dose an extra 200 ml of alkalinity solution per day to offset the affect or a sulfur reactor. I use a CaRx for 90% of the mineral requirements and then trident controlled dosing to make up the last 10% and dial in the numbers.

 

[Dennis Cartier]

FWIW, on my 600 gallon system, I have to dose an extra 200 ml of alkalinity solution per day to offset the affect or a sulfur reactor. I use a CaRx for 90% of the mineral requirements and then trident controlled dosing to make up the last 10% and dial in the numbers.

... and thereby confirming what Randy has said for years, that sulfur denitrification will consume alkalinity unlike other methods of denitrification. I operated a sulfur denitrification filter on 2 different tanks and saw the effect first hand back before automated testers were available.

Excellent idea on using the Trident to fine tune the Ca/Alk balance and fix the imbalance that sulfur denitrification brings.

 

[purp]

I guess I was thinking more in terms of just using sulfur in media bags without CaCO3 so I don’t have an ca/alk imbalance. Then use a KHguardian to dose appropriate amounts of bicarbonate.

 

[purp]

FWIW, on my 600 gallon system, I have to dose an extra 200 ml of alkalinity solution per day to offset the affect or a sulfur reactor. I use a CaRx for 90% of the mineral requirements and then trident controlled dosing to make up the last 10% and dial in the numbers.

Are you using the old school anoxic sulfur denitrator?

 

[ca1ore]

Are you using the old school anoxic sulfur denitrator?

Yes.

 

[Belgian Anthias]

FWIW, on my 600 gallon system, I have to dose an extra 200 ml of alkalinity solution per day to offset the affect or a sulfur reactor. I use a CaRx for 90% of the mineral requirements and then trident controlled dosing to make up the last 10% and dial in the numbers.

200ml of an alk solution in a 2280l reef tank seems to me not that much. How do you know that alkalinity is consumed due to the sulphur reactor? How much calcium carbonate media does the sulphur reactor contain compared to the amount of sulphur used, in volume . What is the flow rate?
For example: if 1ppm nitrate is removed daily by BADES this may consume 10260 mg alk if no calcium carbonate media is used in the reactor. Nitrification which has produced the nitrate may have consumed more, 7.05 mg for each mg NO3 produced or 16074 mg alk.
If both processes take place using calcium carbonate substrate, carbonate is used as a carbon source wich limits the alk consumption.

 

[Dr. Dendrostein]

Sulphur must have been very important in forming the oceans as there is a lot of it, mostly present as sulphate. But this sulphate content seems not to be very important for keeping reef aquaria as salt mixes do vary a lot in sulphate content. https://reefhub.pl/test-of-marine-salts/
Elemental sulphur is only present in very small amounts in the aquarium although in the ocean it is present everywhere, sometimes in huge amounts, as at the coastline of Chili where several million tons are present on the bottom of the sea, playing an important role in the nitrogen and carbon cycle in the ocean.
What is the role of sulphur in a reef aquarium? How important is sulphur for the nitrogen cycle?

In a normal nitrifying biofilm +- 40% of the population have an anaerobic pathway, living in the oxygen minimum zones and anoxic zones, occupied recycling and renewing the biofilm. In the nitrifying biofilm, heterotrophic denitrification is limited due to the limited availability of anoxic zones and of the availability of organic carbon in those zones. Autotrophic denitrification is limited due to the limited availability of usable sulphur in the oxygen minimum zones and anoxic zones.

It is known that if a nitrifying biofilm grows on elemental sulphur more than 90% of the NH4 reduced by nitrification may be removed as nitrogen gas. By providing elemental sulphur as substrate a nitrifying biofilter may produce very little nitrate but a lot of nitrogen gas. This way the nitrogen is effectively removed . The process responsible for this is BADES, Biologaical Autotropic Denitrification on Elemental Sulphur.

Just by providing some elemental sulphur the aquarium system is able to close the nitrogen cycle!

True or false?

In February 2018, set up small dt with some sulfur in bio filter. As an experiment. No issues, but only operated for 4mo.

 

[Belgian Anthias]

... and thereby confirming what Randy has said for years, that sulfur denitrification will consume alkalinity unlike other methods of denitrification. I operated a sulfur denitrification filter on 2 different tanks and saw the effect first hand back before automated testers were available.

The BADES process is used for a very long time and was first used in marine aquaria in the 90ies. As far as I know Randy never made use of elemental sulphur. I think it was Baalsruud who described the process first, in 1954!!! Since then it is known the BADES process needs inorganic carbon and may consume alkalinity. The inorganic carbon source used depends on the situation.
In a reef aquarium, measures must be taken anyway as alk is consumed constantly.
For removing nitrate two other processes can be used, heterotrophic denitrification and DNRA, needing anoxic conditions. Producing a lot of CO2 and ammonia.( DNRA)

+- 16% of ammonia-nitrogen processed by a nitrifying biofilm may be removed naturally by heterotrophic denitrification.

The assimilation of nitrate increases alk but does not remove a thing. When nitrate -nitrogen is used as a nitrogen source a lot of it is leaked back as ammonia-nitrogen. Assimilation of ammonium depletes alk!!

 

[Randy Holmes-Farley]

I guess I was thinking more in terms of just using sulfur in media bags without CaCO3 so I don’t have an ca/alk imbalance. Then use a KHguardian to dose appropriate amounts of bicarbonate.

There is no way to avoid the imbalance. Either alk is depleted, or if you dissolve calcium carbonate to supply that alkalinity, calcium rises.

 

[Randy Holmes-Farley]

The BADES process is used for a very long time and was first used in marine aquaria in the 90ies. As far as I know Randy never made use of elemental sulphur. I think it was Baalsruud who described the process first, in 1954!!! Since then it is known the BADES process needs inorganic carbon. The carbon source used depends on the situation.
For removing nitrate two other processes can be used, heterotrophic denitrification and DNRA, adding alk, using an organic carbon-based reactor which must be kept anoxic, very sensitive for human error, producing a lot of CO2.

+- 16% of the ammonia-nitrogen processed by a nitrifying biofilm may be removed naturally by heterotrophic denitrification.

The assimilation of nitrate increases alk but does not remove a thing. When nitrate -nitrogen is used as a nitrogen source a lot of it is leaked as ammonia-nitrogen. Assimilation of ammonium depletes alk!!

You are correct that I have never used a sulfur reactor, but I understand the chemical processes involved. I have also never vacationed in Wuhan China. Do I need to in order to think it not the best plan?

 

[Dr. Dendrostein]

All I know when using sulfur denitrators, my alkalinity went down, consumed by something....hahaha

 

[ca1ore]

200ml of an alk solution in a 2280l reef tank seems to me not that much. How do you know that alkalinity is consumed due to the sulphur reactor? How much calcium carbonate media does the sulphur reactor contain compared to the amount of sulphur used, in volume . What is the flow rate?
For example: if 1ppm nitrate is removed daily by BADES this may consume 10260 mg alk if no calcium carbonate media is used in the reactor. Nitrification which has produced the nitrate may have consumed more, 7.05 mg for each mg NO3 produced or 16074 mg alk.
If both processes take place using calcium carbonate substrate, carbonate is used as a carbon source wich limits the alk consumption.

I have, frankly, not bothered to try to calculate how much alk the sulfur reactor should or is consuming. Note that I said 90% of the tank requirements come from a traditional CaRx. This is a guess, of course, but that means that the actual alk daily requirement is much higher. I never used trident adjusted dosing prior to running the sulfur reactor so there’s no baseline comparison. I setback the CaRx slightly so that I could use a DoS to dose to offset the reduction. Currently, I need to dose about 50 ml per day of calcium solution to maintain 450; 250 ml of soda ash solution to maintain 8.4. Wobbly math perhaps, but I thus conclude that the differential is a consequence of the sulfur reactor eating alkalinity (since I assume that most systems will dose equal amounts). Randy may savage my math .....

 

[ca1ore]

Continuing ....

I do use reborn in the sulfur reactor (broadly equivalent to the amount of sulfur redia) but using dissolving media to maintain target alkalinity drove calcium up to almost 525. I said that mine is an anoxic sulfurvrecator, however, I run it at higher flow rates than most would judge appropriate .... nominally about 5 gallons per hour. This keeps the ORP low, but not hydrogen sulfide low. Nitrate on the effluent is about 5, which is my tank target level.