DIY Sulfur Denitrator

[Belgian Anthias]

ORP and PH relation

ORP and PH relation

For those who use ORP reading for correcting the flow, take in account that ORP reading is PH related. When PH drops, ORP reading will increase (+-50mv for PH drop from PH 8.2 to PH 7) and visa versa.
As PH in the sulphur-reactor is related to the amount of nitrate reduced ORP reading will rise in accordance with the amount nitrate reduced. When the flow is decreased to correct the ORP increase sulphate reduction may be the result due to sudden decrease of available nitrate in anoxic conditions. ( dissolved oxygen level below 0.5ppm)
When ORP reading is used the ORP meter should be PH correcting. If not, ORP reading should only be used when corrected in relation to PH.

When a BADESS is used dissolved oxygen levels below 0.5ppm are avoided at all times.

 

[dartier]

Sorry if this was asked, I can't find it.
I'm in the process of collecting the materials for the original build.
What is the reason for using cpvc pipe and not regular pvc for the pipe connecting pump to main body?

I think the reason for the preference for CPVC in the original build is that it is sized based on external diameter instead of internal diameter like PVC. So it is a lot easier to drill a hole (using common drill bits) that the CPVC will slide snugly into.

Dennis

 

[tmz]

For those who use ORP reading for correcting the flow, take in account that ORP reading is PH related. When PH drops, ORP reading will increase (+-50mv for PH drop from PH 8.2 to PH 7) and visa versa.


As PH in the sulphur-reactor is related to the amount of nitrate reduced

ORP reading will rise in accordance with the amount nitrate reduced.



When the flow is decreased to correct the ORP increase sulphate reduction may be the result due to sudden decrease of available nitrate in anoxic conditions. ( dissolved oxygen level below 0.5ppm)
When ORP reading is used the ORP meter should be PH correcting. If not, ORP reading should only be used when corrected in relation to PH.

When a BADESS is used dissolved oxygen levels below 0.5ppm are avoided at all times.

Not sure what you mean here:

As PH in the sulphur-reactor is related to the amount of nitrate reduced

PH is not related to NO3;CO2 drives it.


ORP reading will rise in accordance with the amount nitrate reduced.

ORP declines with less nitrate ;it doesn't rise. Nitrate is an oxidizer not a reducer.

 

[CHSUB]

For those who use ORP reading for correcting the flow, take in account that ORP reading is PH related. When PH drops, ORP reading will increase (+-50mv for PH drop from PH 8.2 to PH 7) and visa versa.
As PH in the sulphur-reactor is related to the amount of nitrate reduced ORP reading will rise in accordance with the amount nitrate reduced. When the flow is decreased to correct the ORP increase sulphate reduction may be the result due to sudden decrease of available nitrate in anoxic conditions. ( dissolved oxygen level below 0.5ppm)
When ORP reading is used the ORP meter should be PH correcting. If not, ORP reading should only be used when corrected in relation to PH.

When a BADESS is used dissolved oxygen levels below 0.5ppm are avoided at all times.

interesting and thxs, however, +/- 50 ORP is of little worry; as i have found the "usable" range of ORP is from -100 to -325. i'm sure by now, you see how easy ORP controlled sulfur reactor are; i bet you're about to retire your BADESS system?

 

[Belgian Anthias]

interesting and thxs, however, +/- 50 ORP is of little worry; as i have found the "usable" range of ORP is from -100 to -325. i'm sure by now, you see how easy ORP controlled sulfur reactor are; i bet you're about to retire your BADESS system?

Autotropic denitrification on sulfhur can take place when the dissolved oxygen level decents below 3ppm.(normal +-6ppm) Heterotropic denitrification starts when dissolved oxygen level decents below 0.4ppm (annoxic conditions). The usable range for autotropic denitrification is certainly not limited to the range below-100mv! That is why the flow can increase to reach 10l/h/liter sulphur and still have active autotropic denitrification.
ORP can be used for monitoring a BADESS but Ph monitoring can tell us a lot more.
A BADESS removes easely between 1ppm and 2ppm nitrate every day while keeping the systems nitrate level between 1ppm and 0.5ppm. As a BADESS user I am able to decide at what nitrate level I want the aqua-system to operate (the desired nitrate level) and keep it that way. I am able to close the nitrogen cycle by removing the daily nitrate production every day. So, no, an ORP controled denitrification system where the flow is limited to keep the reactor annoxic will never be able to replace a technical very simple, safe and easy to manage BADESS.

 

[Belgian Anthias]

These are normal results except for the bacterial bloom! I think this must come due to the sudden nitrate level changes.
Is there nitrite present in the effluent water?
Flow corrections must be made slowly certainly when reducing the flow. less oxygen and less nitrate is entered. Reduce the flow till the effluent has reached 0 again and than increase the flow a bit. Keep the flow as high as possible.
The flow depends of the nitrate level in the system water. When the nitrate level is increased or decreased suddenly by water changes the reactor will not be able to follow without adapting the flow to the nitrate level
A sulphur reactor needs a constant supply of nitrate to be able to function properly and to become self-regulating.

When nitrogen gas is present in the water and this water is compressed by a pump, when this water decompresses in the aquarium a milky bloom may occur due to the supersaturation of N2 which may look as a bacterial bloom. To determine which is which take a glass of the water and leave it for 10 to 20 minutes. Supersaturated water with N2 will clear out.

 

[Belgian Anthias]

Orp and disolved oxygen

Orp and disolved oxygen

For ORP users.

ORP reacts very slowly to changes in dissolved oxygen. When the input is doubled it may take a very long time (even more than an hour,) before the reading stabilizes. ORP reacts a lot faster on nitrate changes.
Normal seawater contains 6-7 ppm dissolved oxygen. When the incoming water contains 40ppm nitrate and the flow true the reactor is decreased by half, how will ORP react? All nitrate will be reduced fast! What if the flow is increased, Nitrate increase will be measured and only with a long delay the increase in D/O.
When operated at a low nitrate level of 1ppm instead of 40 ppm there is still +- 6ppm of oxygen present. How this is translated to ORP readings? We assume the same quantity of nitrate has to be removed daily to keep the level steady.
The redoxpotential = 1,23 V for oxygen, 0,80 V for nitrate en 0,17 V for sulphate.
One can have a ORP reading of 0 mV with 3ppm D/O and 0mv with only 0,5ppm D/O.

I still do not get it how ORP can help me to manage the flow true a sulphur de-nitrator.
Managing the flow to keep the same nitrate reduction rate at changing nitrate levels in the system seems to me not possible based on ORP readings.

 

[dartier]

Not sure what you mean here:

As PH in the sulphur-reactor is related to the amount of nitrate reduced

PH is not related to NO3;CO2 drives it.


ORP reading will rise in accordance with the amount nitrate reduced.

ORP declines with less nitrate ;it doesn't rise. Nitrate is an oxidizer not a reducer.

Well Belgian is sort of correct, but not for the reasons he thinks. A correlation can be established between PH and Nitrate only because ORP declines with less Nitrate and ORP also moves counter to PH (-56mv for each unit of PH). So making the pitch that you can tell how much Nitrate is being reduced by monitoring PH is because you are actually observing changes in ORP. Though very ,very indirectly. Kind of like reading what was written with a finger on a bathroom mirror by turning on the shower. Far easier to use a piece of paper and a pencil (E.g. monitor ORP directly).

Well it looks like I will not ever get my new larger reactor online. I am moving and will be upgrading to a 300DD tank after the move. I plan on exploring DIY versions of ORP controlled Jaubert filters ( E.g. DyMiCo ). My experiences with a ORP controlled sulfur filter are what piqued my interest in this area again.

Dennis

 

[dartier]

For ORP users.

ORP reacts very slowly to changes in dissolved oxygen. When the input is doubled it may take a very long time (even more than an hour,) before the reading stabilizes. ORP reacts a lot faster on nitrate changes.
Normal seawater contains 6-7 ppm dissolved oxygen. When the incoming water contains 40ppm nitrate and the flow true the reactor is decreased by half, how will ORP react? All nitrate will be reduced fast! What if the flow is increased, Nitrate increase will be measured and only with a long delay the increase in D/O.
When operated at a low nitrate level of 1ppm instead of 40 ppm there is still +- 6ppm of oxygen present. How this is translated to ORP readings? We assume the same quantity of nitrate has to be removed daily to keep the level steady.
The redoxpotential = 1,23 V for oxygen, 0,80 V for nitrate en 0,17 V for sulphate.
One can have a ORP reading of 0 mV with 3ppm D/O and 0mv with only 0,5ppm D/O.

I still do not get it how ORP can help me to manage the flow true a sulphur de-nitrator.
Managing the flow to keep the same nitrate reduction rate at changing nitrate levels in the system seems to me not possible based on ORP readings.

You are on the right track. Oxygen and Nitrate are both oxidizers, so they both raise ORP. As the water is flowing through the reactor, the sulfur reducing bacteria will preferentially consume the Oxygen and then Nitrate, once the Oxygen is depleted.

When you regulate flow based on the ORP level, the flow through the reactor will be as fast as the reactor is capable of, based on the amount of Oxygen and Nitrate that can be consumed in a period of time.

Lets assume the Oxygen level is constant in your tank. If the Nitrate level is increasing, the flow will slow as the ORP rises. Once the Nitrate increase is overcome and it is being depleted, the flow will increase as the ORP is falling, and remember we are trying to maintain the ORP at a preset level (for example no lower than -200mv). So the amount of sulfur media, and the bacteria population will directly impact the speed that the ORP falls, and by monitoring the ORP level, you flow only as much as your reactor can process at that time.

So what can go wrong? Well in all reactors (ORP controlled or not), if the reactor is too small, then it will not be able to process enough O2/NO3 to make a dent in the Nitrate level (like me little test reactor).

On the other hand if the reactor is large and contains a lot of sulfur media, then once the Nitrate level falls very low, you are simply processing Oxygen and you can strip your tank of Nitrate. In that case you simply need to remove some media to lessen the efficiency of the reactor. Adjusting the ORP target higher, may also work in this situation, though I have never been able to test this due to my small reactor.

Does that help explain how flow relates to Nitrate levels when using ORP?

Dennis

 

[canada55]

It's been a few months now since I have posted any results of what this Sulfur denitrator has done to my 500 gal system. Since the beginning of September (60days) I have gone from 75ppm Nitrate down to 2ppm , pH has held steady at 8.0 and Phos. still is a bit of a problems at .25 and ORP is -25 to -35.

I have only had to vent gas 2 twice in the past 30 days

I have done NO water change in the past 60days. But I'm going to do a 100gal change very soon.

I have noticed that algae growing on back of tank is dying off, as well as some hair algae is also shrinking and starting to discolor/die off. Some Paly that had been closed up for months is starting to open up again. Now with an effort in the reduction of Phos. I'm sure I'll be back on track.....

 

[Belgian Anthias]

PH and denitrification

PH and denitrification

Well Belgian is sort of correct, but not for the reasons he thinks. A correlation can be established between PH and Nitrate only because ORP declines with less Nitrate and ORP also moves counter to PH (-56mv for each unit of PH). So making the pitch that you can tell how much Nitrate is being reduced by monitoring PH is because you are actually observing changes in ORP. Though very ,very indirectly. Kind of like reading what was written with a finger on a bathroom mirror by turning on the shower. Far easier to use a piece of paper and a pencil (E.g. monitor ORP directly).

Well it looks like I will not ever get my new larger reactor online. I am moving and will be upgrading to a 300DD tank after the move. I plan on exploring DIY versions of ORP controlled Jaubert filters ( E.g. DyMiCo ). My experiences with a ORP controlled sulfur filter are what piqued my interest in this area again.

Dennis

The reduction of nitrate produces H+ and sulphate. This lowers the PH in accordance with the amount of nitrate reduced. There is no CO2 production at that moment. The more nitrate reduced, the more effect on the PH. With some experience one will have an idea of the working rate. At high flow the nitrification process thus influence the reading because more H+ will be produced. It depends where the PH is measured, in the reactor, at the outlet of the sulphur reactor or after the calcium reactor. That is one of the reasons why I would use separate reactors.
Sulphur reactors are normally operated at a daily flow of 1 x the total system volume a day which makes it possible to remove the daily production daily and keep the level steady at a very low level. ORP reading is suspected to be close to 0 and gives no idea of the nitrate reduction at all because of the amount of D/O entered.
At a level of 70 ppm or at 0.5ppm still the same daily nitrate production has to be removed so the H+ from de-nitrification will stay the same but due to the increased flow more H+ is produced in the reactor due to the increased nitrification processes.
Removing a nitrate production of 1 ppm daily at 2 ppm or at 0.5 ppm = flow x 4
As the sulphur-reactor will operate at +- 0.5ppm D/O it may be suspected that heterotrophe denitrification will be minimal as is the HO- production.
During normal operation only +-1/8 of the volume will be used for denitrification depending of the daily nitrate production and the rest of the space is used to deplete the incoming D/O.

 

[Belgian Anthias]

You are on the right track. Oxygen and Nitrate are both oxidizers, so they both raise ORP. As the water is flowing through the reactor, the sulfur reducing bacteria will preferentially consume the Oxygen and then Nitrate, once the Oxygen is depleted.

When you regulate flow based on the ORP level, the flow through the reactor will be as fast as the reactor is capable of, based on the amount of Oxygen and Nitrate that can be consumed in a period of time.

Lets assume the Oxygen level is constant in your tank. If the Nitrate level is increasing, the flow will slow as the ORP rises. Once the Nitrate increase is overcome and it is being depleted, the flow will increase as the ORP is falling, and remember we are trying to maintain the ORP at a preset level (for example no lower than -200mv). So the amount of sulfur media, and the bacteria population will directly impact the speed that the ORP falls, and by monitoring the ORP level, you flow only as much as your reactor can process at that time.

The level is 1ppm and the production to remove is 1 ppm daily. The production increases and the level rises. As the level rises, at the same flow, more nitrate is entered. Without ORP control the reactor will not change the flow but if the reactor is big enough and in balance the reactor is self-regulating, more bacteria will grow and remove the increased amount of nitrate. Nothing has to be done!
In this example for each ppm of nitrate that has to be removed +- 5ppm of oxygen has to be consumed. The redox potential of oxygen is a lot higher as for nitrate. If ORP control will reduce the flow as nitrate increases, let us assume +- the same amount of nitrate is entered. How the increased amount of nitrate will be removed? As D/O is reduced more space is created for the same nitrate reduction. The reduction of D/O will influence the ORP +-10 x more as the change in nitrate reduction. ORP will decrease due to D/O, increasing the flow. Are we managing the D/O or the nitrate reduction?

A managing guide for wastewater- and drinkingwater plants does advise +50mv to -100mv ORP for the denitification zone. at PH 6.5, temp? heterothrophe) I could not find a referenced managing guide for sulphur based reactors exept for the one from aqua medic which is not suitable for sulphur denitrators.

So what can go wrong? Well in all reactors (ORP controlled or not), if the reactor is too small, then it will not be able to process enough O2/NO3 to make a dent in the Nitrate level (like me little test reactor).

On the other hand if the reactor is large and contains a lot of sulfur media, then once the Nitrate level falls very low, you are simply processing Oxygen and you can strip your tank of Nitrate. In that case you simply need to remove some media to lessen the efficiency of the reactor. Adjusting the ORP target higher, may also work in this situation, though I have never been able to test this due to my small reactor.

[At 70ppm or at 1ppm, the same daily production has to be removed. Why reducing the sulphur? The efficiency and volume of the reactor is based on the efficiency of the reactor to deplete oxygen and the daily nitrate production to remove. Lowering the nitrate level means more oxygen has to be removed to be able to remove the same daily nitrate production.
To be able to operate the reactor at very low nitrate levels and remove the daily production every day lot of oxygen has to be depleted. This assumes a normal fed aquarium and a constant supply of nitrate.
As the DO/nitrate ratio changes when nitrate level descends as flow has to increase to be able to remove the same nitrate production the influence on ORP will be in favor of the D/O.
I think a sulphur denitrator will work fine at + 50mv ORP at low nitrate levels. If big enough.

Does that help explain how flow relates to Nitrate levels when using ORP?

Dennis

Thanks for the explanation. I had some remarks. I understand how ORP control can keep a denitrification reactor within set working limits ( which limits should be adjusted to the working range of sulphur denitrators). But I can not see how ORP can help in managing the daily nitrate removal as it is based on limiting the flow true the reactor not taking in account the DO/NO3 reduction ratio and keep the same NO3 reduction.

 

[Belgian Anthias]

The reduction of nitrate produces H+ and sulphate. This lowers the PH in accordance with the amount of nitrate reduced. There is no CO2 production at that moment. The more nitrate reduced, the more effect on the PH. With some experience one will have an idea of the working rate. At high flow the nitrification process thus influence the reading because more H+ will be produced. It depends where the PH is measured, in the reactor, at the outlet of the sulphur reactor or after the calcium reactor. That is one of the reasons why I would use separate reactors.
Sulphur reactors are normally operated at a daily flow of 1 x the total system volume a day which makes it possible to remove the daily production daily and keep the level steady at a very low level. ORP reading is suspected to be close to 0 and gives no idea of the nitrate reduction at all because of the amount of D/O entered.
At a level of 70 ppm or at 0.5ppm still the same daily nitrate production has to be removed so the H+ from de-nitrification will stay the same but due to the increased flow more H+ is produced in the reactor due to the increased nitrification processes.
Removing a nitrate production of 1 ppm daily at 2 ppm or at 0.5 ppm = flow x 4
As the sulphur-reactor will operate at +- 0.5ppm D/O it may be suspected that heterotrophe denitrification will be minimal as is the HO- production.
During normal operation only +-1/8 of the volume will be used for denitrification depending of the daily nitrate production and the rest of the space is used to deplete the incoming D/O.

What happens in the calciumreactor where D/O will be less as in the sulphur reactor?
CO2 may be formed: calcium carbonate is effected by H+ and splits into calcium and bicarbonate. Some of the bicarbonate may become carbonic acid which may result in CO2 and water. Aeration of the effluent is advised to stabilize the PH.
Some of the produced calcium may find its way to the sulphate which may result in plaster this way reducing the amount of sulphate. ( it happens in SLAD systems but I do not know it is possible in seawater) It is known sulphate is held back in the calcium reactor.
When some nitrite is left over it is known to be processed in the calciumreactor. ( probably due to heterotropic bacteria using the organic carbon which is not consumed in the sulphur reactor or is it anammox?)

 

[Belgian Anthias]

It's been a few months now since I have posted any results of what this Sulfur denitrator has done to my 500 gal system. Since the beginning of September (60days) I have gone from 75ppm Nitrate down to 2ppm , pH has held steady at 8.0 and Phos. still is a bit of a problems at .25 and ORP is -25 to -35.

I have only had to vent gas 2 twice in the past 30 days

I have done NO water change in the past 60days. But I'm going to do a 100gal change very soon.

I have noticed that algae growing on back of tank is dying off, as well as some hair algae is also shrinking and starting to discolor/die off. Some Paly that had been closed up for months is starting to open up again. Now with an effort in the reduction of Phos. I'm sure I'll be back on track.....

Nice results.
What is the flow ratio you are keeping on? Flow/day/litre sulphur
daily flow x steady nitrate level will give the daily nitrate production. ( if effluent 0 nitrate )
Did you reach max flow?

 

[Belgian Anthias]

Not sure what you mean here:

As PH in the sulphur-reactor is related to the amount of nitrate reduced

PH is not related to NO3;CO2 drives it.


ORP reading will rise in accordance with the amount nitrate reduced.

ORP declines with less nitrate ;it doesn't rise. Nitrate is an oxidizer not a reducer.

CO2 may drive PH. PH is a measurement of H+ and HO-. Due to NO3 reduction H+ is produced. More NO3 reduction, more H+.

NO3 reduction lowers ORP, sorry about that, The influence of nitrate on ORP will be high at high nitrate levels and small at low nitrate levels as D/O stays the same. How one can know if nitrate is reduced in the reactor based on ORP readings?
PH can tell us if the reactor is actively reducing nitrate due to the relation with H+ production.

 

[Belgian Anthias]

untherstanding ORP

untherstanding ORP

At high nitrate levels let us say 70ppm the influence of nitrate on ORP reading will be high as D/O is +- 6ppm. The ORP limits for the reactor are set -100mv to -200mv . At a constant flow and the nitrate level decreases ORP will decrease because less nitrate is entered. When -200mv is reached the ORP controller will increase the flow in an attempt to keep the reactor above -200mv. More DO, more nitrate entered. Nitrate level decreases more to reach the level where the potential of total nitrate and DO is the same (+- 10ppm NO3). From that moment it will be DO that starts to drive the ORP reading when the nitrate level decreases more. How will ORP control avoid that all nitrate will be consumed and sulphate reduction can take place knowing -200mv is set as the low limit?
I think that ORP limit settings of +50mv and -100mv are more suitable for a sulphur denitrator which allows more flow.
How ORP control can give me control over the amount of nitrate the reactor will remove to keep the nitrate level steady on a the desired low nitrate level?

 

[tmz]

CO2 may drive PH. PH is a measurement of H+ and HO-.

CO2 from biological activity or gas exchange with the surrounding air produces H+ when it hydrolizes;CO2+H20 ----> HCO3(bicarbonate) + H or H2CO3 (carbonic acid) and other combinations all of which essentially result in a net plus of 1 H+ from the H2O, the second H+ is neutralized .

Due to NO3 reduction H+ is produced. More NO3 reduction, more H+

No, When NO3 is reduced to N ;it adds alkalinity not H+; NO3 raises ORP since it has a potential to neutralize acidity, H+ . It doesn't add it.




NO3 reduction lowers ORP, sorry about that, The influence of nitrate on ORP will be high at high nitrate levels and small at low nitrate levels as D/O stays the same.

How one can know if nitrate is reduced in the reactor based on ORP readings?
PH can tell us if the reactor is actively reducing nitrate due to the relation with H+ production.



To some extent, maybe,( unless other changes from the sulfur reactions add oxidizers like sulfate or CO2 rsulting in higher H+) but not with any precision or consistency as the ORP will vary with NO 3 levels, NO3 is a moderately strong oxidizer; up with more NO3, down with less but that's not nearly the whole story.

ORP is complex and may change due to a number of variables effecting oxidizing power vs reducing power.
For example: increased organics from an event in the aquarium unrelated to nitrate can lower it;some metals can lower it , ammonia, sulfide and other things can lower it.

Other oxidizers, some of which are stronger than NO3 , like sulfate,some metals like Iron Fe++ , iodate etc can increase it.

Even H+ which can increase the oxidation power of other oxidizers can raise ORP which is why low pH correlates with higher ORP , and on and on.

I don't think ORP is a useful predictor of nitrate levels in a sulfur reactor given everything else going on..

 

[Belgian Anthias]

CO2 from biological activity or gas exchange with the surrounding air produces H+ when it hydrolizes;CO2+H20 ----> HCO3(bicarbonate) + H or H2CO3 (carbonic acid) and other combinations all of which essentially result in a net plus of 1 H+ from the H2O, the second H+ is neutralized .

Surrounding air? PH of Sulphur denitrator effluent is measured before entering the calcium reactor(s).

No, When NO3 is reduced to N ;it adds alkalinity not H+; NO3 raises ORP since it has a potential to neutralize acidity, H+ . It doesn't add it.

Why do we need the calcium reactor to complete the sulphur denitrator system?

H+ production and its effect on alkalinity is a disadvantage of nitrification and denitrification using a BADESS. Because anaerobic bacterial activity on the sulphur is related to PH the activity slows down with PH decrease to stop almost completely at PH 5.6. That is why in SLAD systems lime is added to the reactor. We use a separate calcium reactor to remove H+ which produces Ca and bicarbonate this way neutralizing the effect on alkalinity by nitrate reduction on sulphur.

Oxygen, nitrate and sulphate are the most important oxidizers and are used in that order by the anaerobic sulphur bacteria we need and try to cultivate.
The redoxpotential = 1,23 V for oxygen, 0,80 V for nitrate en 0,17 V for sulphate. ORP of 1 0 = 1.53 NO3 = 7.235 SO4.
Due to the high amount of sulphate present in seawater and the production in the reactor sulphate is an important part of the ORP
Using BADESS knowing the amount DO in the reactorwater would be interesting. Finding a relation between DO and ORP seems to be very difficult certainly in seawater. Not that I need DO or ORP reading for operating a BADESS but it seems to me more interesting to invest in DO measurement instead of ORP
PH monitoring of the reactors effluent tells us all we need.

 

[tmz]

Surrounding air? PH of Sulphur denitrator effluent is measured before entering the calcium reactor(s).




Aside from complex and variable reactions occuring in the dentiirator;doesn't the reactor get it's feed water from the aquarium ? How do you account for variations in the feed water ? Doesn't gas exchange occur and biological activity occur in your aquariums ? In other words how do you know nitrate reduction is precisely the sole cause for pH variation in the reactor? I don't think that's possible with any certainty.


Why do you think oxygen , nitrate and sulphate (sic) are the most important oxidizers? ArE you using a chart or something or just guessing?

I understand the idea of running the effluent over a course of aragonite to get back some of the alkalinity; it's been discussed in this thread about 50 times or more already. IIRC the analyses done in an earlier post in this thread showed it was a minimal addition in the scheme of things and alk monitoring and additional supplementation are often required. in any case it has nothing to do with whether or not the effluent pH can precisely indicate nitrate reduction.

 

[Belgian Anthias]

Aside from complex and variable reactions occuring in the dentiirator;doesn't the reactor get it's feed water from the aquarium ? How do you account for variations in the feed water ? Doesn't gas exchange occur and biological activity occur in your aquariums ? In other words how do you know nitrate reduction is precisely the sole cause for pH variation in the reactor? I don't think that's possible with any certainty.

Never said that.


Why do you think oxygen , nitrate and sulphate (sic) are the most important oxidizers? ArE you using a chart or something or just guessing?

It is the natural way things happen. Nature follows most of the time the rule of the easiest path. When it does not there must be a reason.
Only Humans invent things to make easy things very difficult. Or use inventions who are only useful or make themselves necessary because they are used.

I understand the idea of running the effluent over a course of aragonite to get back some of the alkalinity; it's been discussed in this thread about 50 times or more already. IIRC the analyses done in an earlier post in this thread showed it was a minimal addition in the scheme of things and alk monitoring and additional supplementation are often required. in any case it has nothing to do with whether or not the effluent pH can precisely indicate nitrate reduction.

Aragonite is not the best media to use in a calcium reactor. Cheap oystershell has proven to be a lot better in providing ca and bicarbonate in a SLAD system.

PH monitoring can tell me that denitrification reactions take place in the closed environment of the reactor. Are there other main reasons why PH in the reactor should decrease? As nitrification and denitrification both produces H+ we can use separate reactors this way showing the nitrification activities and denitrification activities making it a bit more precisely. In big systems BIO- sandfilters can be used to reduce the D/O till 3-2 ppm followed in series by sulpur denitrators ( sulphur reactor + calcium reactor)
ORP monitoring only gives me an idea of the potential available to oxidize.

When using a BADESS the nitrogen cycle is closed by removing the daily produced nitrate daily using the nitrate available in the system water. A BADESS uses BIO filters where nitrification and denitrification on sulphur is the main activity. Most processes take place outside the aquarium in closed reactors making it controllable.
The user decides the nitrate removal rate and the desired nitrate level to keep.
A BADESS needs a regular supply of nitrate to be able to keep on a very low nitrate level and is not suitable for low nutrient systems