It is not possible to make correct calculations regarding the calcium production and the influence on carbonate hardness based on the nitrate level, on the difference between the supply and the output of a BADES System. One can only make a difficult estimate.
It depends not only on the BADES process but also on other sulfur sources. An important part of the nitrate is used and is needed for the oxidation of HS, originating from anaerobic remineralization and sulfate reduction, partial and complete sulfide oxidation whereby sulfur and/or sulfate is produced depending on the nitrate supply.
As with heterotrophic denitrification, the combined autotrophic denitrification by means of sulfur derivatives, the reduction of sulfate to sulfide, the oxidation of sulfide and the reduction of nitrate has the same positive effect on alkalinity by increasing it by 3.57mg CaCO3. (VanRijn2005) ref:
http://www.baharini.eu/baharini/doku.php?id=nl:badess:theorie:de_neveneffecten#alkaliniteit
That sulfur or sulfate is formed during the oxidation of sulfide is determined by the sulfide/nitrate ratio in the biofilm. (Fang2010) At an N: S ratio of 8: 5 sulfate is formed, at a ratio of 2: 5 sulfur (SherEnCo2008) ref:
http://www.baharini.eu/baharini/doku.php?id=nl:badess:theorie:de_neveneffecten#waterstofsulfide
This is to underline the importance that sufficient nitrate is present in an oxygen-free seawater containing reactor and that the pursuit of 0 nitrate in the effluent is not such a good idea. The use of a sulfur denitrator is accompanied by proper and difficult flow management and is therefore not recommended by me.
A BADES reactor is NOT kept anoxic and 0 nitrates in the outflow is not pursued, it is not necessary!
Aerobic and anaerobic remineralization, nitrification, autotrophic and heterotrophic denitrification, DNRA, these are all processes that influence the environment, the oxygen demand and the denitrification capacity of a biofilm. And the substrate on which the biofilm grows plays a major role.
Making a calculation based on just one of the many processes can never lead to a correct reflection of reality.
It is also very important that the correct data is used as a basis.
For example, one cannot calculate the correct Ca production using the BADES process since no Ca is produced in this process.
The process can result in Ca being produced if use can be made of the acids produced to dissolve calcium carbonate. In that case, alkalinity as a carbon source has already been used. and use is made of H + production after the process and pH transition has taken place.
2 H2O + 5 S + 6 NO3 - → 3 N2 + 5 SO42 - + 4 H + (HolmesFarley2003) ref:
https://www.advancedaquarist.com/2003/8/chemistry
According to this formula, I arrive at a Ca production of ± 4.3 grams per 10 grams of nitrate converted to nitrogen gas if all H + production can be used to dissolve calcium carbonate. I am not a chemist, it is an estimate. The formula used does not take into account the build-up of the necessary biomass. If we add the cell structure for which ammonia is used, this is according to Batchelor and Lawrence
55S 50NO 3 38H 2 O 20 CO 2 4 NH 4 → 4 C 5 H 7 N 2 O 25 N 2 55 SO 4 64H. Almost twice as much H + is produced here and possibly twice as much Ca. Later this was corrected to 11 S 10 NO3 - 4.1 HCO3 - 0.5 CO2 1.71 NH4 2.5 H2O -> 0.92 C5H7NO2 11 SO4 - 5.4 N2 9.62 H and then we get almost half more H + production. To make correct calculations, one must not only have knowledge of the processes but also opt for the most realistic. ref:
http://www.baharini.eu/baharini/dok...ie:stikstofkringloop#autotrofe_denitrificatie
In a BADESS we try to use Calcium Carbonate as a carbon source and we cannot use the above formulas as in these formulas alkalinity is used as a carbon source.
I use the formula of Zhang, the designer of the SLAD system. 55S + 44CaCO 3 + 50NO 3- + 18H2O + 4NH4 + → 4 C5H7O2N + 25N 2 + 55SO4 2- + 44Ca 2+ + 24HCO3- (TCZhang2004) ref:
http://www.baharini.eu/baharini/doku.php?id=en:makazi:het_water:slad_systeem&rev=1580734860 As one can see, no H + is produced here, but Ca and bicarbonate are produced directly. According to this formula, I get 5.68 grams of calcium per 10 grams of nitrate converted by the BADES process. A big difference with the calculation according to Holmes Farley. Added to this is the production of the nitrification process, whereby a BADES System can possibly meet the calcium demand.
The practice will be completely different from the theoretical approach as only a part of the nitrate is removed by the BADES process and many other processes influence the result.
It is therefore useless to try to make all kinds of calculations on which one cannot really rely on practice. The reality will be somewhere in the middle.
To use BADES, no special and expensive equipment or making all kinds of calculations is required, not even a reactor. Common sense only. A good BADES system will have little influence on the alkalinity in the system and will produce calcium . Calcium is also produced by autotrophic processes in an aquarium without BADES. The usual measures for correction are sufficient.
For easy management of the nitrate level, I recommend a separate filter, reactor or refugium.
I strongly discourage the use of an anoxic reactor, a sulfur denitrator, unless people know what they are doing. In that case it works very well for lowering a high nitrate content, but the result deteriorates and the risks increases as the nitrate content decreases. The amount of oxygen to be removed remains the same, which means that with a lower nitrate content, insufficient nitrate can be supplied, resulting in sulfate reduction.
The intention is to remove daily nitrate overproduction on a daily basis with a low nitrate content, it must be possible to adjust the flow to the nitrate content so that the same amount can be removed on a daily basis, or slightly more to lower the level. The lower the nitrate content, the more flow is needed, the more oxygen is supplied, to remove the same daily nitrate overproduction daily. This is not possible with a sulfur denitrator which is kept anoxic.
