Possible to quantify nitrate removal rate for a reactor?

[FishguyJosh]

I have a 180 gallon Fowlr tank with nitrates that run between 60 and 80 ppm (post and pre water change respectively). Based on the consistency of my water changes (25% per week), I can infer that the weekly nitrate increase is around 20 ppm. I have some big fish in there so there is quite the bioload.

The question is, do nitrate reactor manufacturers provide a theoretical nitrate removal rate for their reactors? Or has this kind of question ever been posted/answered before? The goal of course is to reduce the frequency of water changes.

 

[wmb0003]

I believe it would depend on size, flow rate, media used. I would think the manufacturer should have a rough idea but doubt you will find a set number due to the many variables.

I would suggest this DIY reactor, you can adjust flow rate as well as carbon dosing amount to dial in your target levels.

Thread 'Poor Man's Nutrients Control - Donovan's Nitrate Destroyer'
https://www.reef2reef.com/threads/poor-mans-nutrients-control-donovans-nitrate-destroyer.302685/

 

[Belgian Anthias]

Nitrate management is about preventing nitrate may build up. It starts with the protein content of the food added.

In fish only tanks one may mange the nitrate production by managing the C/N ratio, adding organic carbon . See biofloc.
ref: MB CMF de Haes 2017-2019

What kind of reactor you have in mind? Using BADES ?
One does not need a reactor for increasing the nitrate removal rate using BADES. One may use BADES columns or just add some elemental sulfur as a substrate .for a growing biofilm. If the nitrate removal rate must be manageable to keep the nitrate level as desired by the user, one must use BADES in a reactor or in a refuge ( biofilter) ref: MB CMF De Haes 2007-2021

Removing only nitrate does not remove the rest of what is left over and prevents the rest may be removed by growth.

 

[J1a]

I have a 180 gallon Fowlr tank with nitrates that run between 60 and 80 ppm (post and pre water change respectively). Based on the consistency of my water changes (25% per week), I can infer that the weekly nitrate increase is around 20 ppm. I have some big fish in there so there is quite the bioload.

The question is, do nitrate reactor manufacturers provide a theoretical nitrate removal rate for their reactors? Or has this kind of question ever been posted/answered before? The goal of course is to reduce the frequency of water changes.

If some one who's running a nitrate reactor can provide the flow rate, inlet and effluent nitrate levels, then we can model the nitrate export for your system.

 

[Belgian Anthias]

Nitrate management is about preventing nitrate may build up. It starts with the protein content of the food added.

In fish only tanks one may mange the nitrate production by managing the C/N ratio, adding organic carbon . See biofloc.
ref: MB CMF de Haes 2017-2019

What kind of reactor you have in mind? Using BADES ?
One does not need a reactor for increasing the nitrate removal rate using BADES. One may use BADES columns or just add some elemental sulfur as a substrate .for a growing biofilm. If the nitrate removal rate must be manageable to keep the nitrate level as desired by the user, one must use BADES in a reactor or in a refuge ( biofilter) ref: MB CMF De Haes 2007-2021

Removing only nitrate does not remove the rest of what is left over and prevents the rest may be removed by growth.

I have a 180 gallon Fowlr tank with nitrates that run between 60 and 80 ppm (post and pre water change respectively). Based on the consistency of my water changes (25% per week), I can infer that the weekly nitrate increase is around 20 ppm. I have some big fish in there so there is quite the bioload.

The question is, do nitrate reactor manufacturers provide a theoretical nitrate removal rate for their reactors? Or has this kind of question ever been posted/answered before? The goal of course is to reduce the frequency of water changes.

Calculating the nitrate removal rate using a reactor: flow rate x (nitrate content in-fluent - nitrate content effluent)

Using BADES in a reactor the reactor must be big enough. The system has a daily nitrate production between +- 3ppm-4ppm or +- 2400 mg/ daily. Having 80 ppm the daily flow must be at least 30l/day to remove the daily production
More important, to remove the same daily nitrate production of 2400 mg daily, having reached a desired level of +- 5ppm the daily flow is increase to become 480l/daily or 20l/h. This if a 0 nitrate effluent is the target. Starting with a flow of 480l/day, the difference between effluent and influent is kept at +5ppm. To keep a level of 2 ppm a daily flow of 1200l/day or 2x the total system content is needed. If a little more than the daily nitrate yield is removed daily then the level will drop.

The above is not correct because in an anoxic environment also DNRA takes place, using nitrate to produce ammonia , nitrate is removed but not exported. ( normally about 16% of total heterotrophic nitrate removal) The amount DNRA may become very high using a carbon based denitrator. Also, a lot of HS may be produced if not managed correctly. Heterotropic denitrification = anaerobic remineralisation, producing inorganic nutrients, phosphate . In a marine environment nitrate is used if available, if not available sulphate is used for respiration. I can not advise a carbon based reactor because it only works when the reactor is kept in an anoxic state . That makes such a system very sensitive to human errors.

Targetting O nitrates in the effluent using a denitrator may not be a good idea! ( sulphate reduction!)

Using BADES the reactor is NOT kept in an anoxic state, the flow is managed in function of the nitrate content and such a high flow system becomes self regulating .

A BADES reactor must be big enough!! One only can remove what is entered.

 

[Belgian Anthias]

in

If some one who's running a nitrate reactor can provide the flow rate, inlet and effluent nitrate levels, then we can model the nitrate export for your system.

Influent = 20ppm NO3
Effluent = 0 ppm NO3
Flow rate is 600l/daily,= 25l/h
Heterotrophic based reactor nitrogen export =?
Autotrophic based reactor nitrogen export = ?

 

[J1a]

in



Influent = 20ppm NO3
Effluent = 0 ppm NO3
Flow rate is 600l/daily,= 25l/h
Heterotrophic based reactor nitrogen export =?
Autotrophic based reactor nitrogen export = ?

Did a very crude model for this set up, assuming a DT of 180G and a sump of 50G,

If your influent is steady at 20ppm, the denitratetor is helping you to process about 12g of nitrate per day.

 

[Belgian Anthias]

Did a very crude model for this set up, assuming a DT of 180G and a sump of 50G,

If your influent is steady at 20ppm, the denitratetor is helping you to process about 12g of nitrate per day.

If the influent is steady, the level does not decent! It is the intention the level goes down. I expect the daily removal rate to go down also. So the calculation just represents what is possible at the moment of measuring.
At a certain level, having the same flow ( anoxic reactor) , the removal rate will be insufficient to remove the daily production and the level will not decent any more. So, it may be more important to be able to know what level I may reach using a denitrator having a certain volume ( flow rate).

 

[J1a]

If the influent is steady, the level does not decent! It is the intention the level goes down. I expect the daily removal rate to go down also. So the calculation just represents what is possible at the moment of measuring.
At a certain level, having the same flow ( anoxic reactor) , the removal rate will be insufficient to remove the daily production and the level will not decent any more. So, it may be more important to be able to know what level I may reach using a denitrator having a certain volume ( flow rate).

I think I understand what you mean. However, when I was modeling this, I realised we cannot ignore the production. If you are interested, I can send you the simulation file. You can then adjust the flow rate etc, to see the effect of the reactor.

And yes. By changing the flow rate, you can see the equilibrium level of nitrate.

 

[Belgian Anthias]

I think I understand what you mean. However, when I was modeling this, I realised we cannot ignore the production. If you are interested, I can send you the simulation file. You can then adjust the flow rate etc, to see the effect of the reactor.

And yes. By changing the flow rate, you can see the equilibrium level of nitrate.

I am interested in the simulation file.


Using a denitrator ( anoxic reactor), the flow is limited in function of the oxygen content, and can not be managed in function of the nitrate level..
Of coarse we can not ignore the production, it is the most important factor. Because one can not change the flow rate in function of the nitrate removal rate and the same time keep the reactor anoxic using such reactor, the final nitrate level will depend on the daily nitrate production and the level will increase when the production increases. Because the level increases the reactor will remove more nitrate ( autotrophic based). Carbon based also one has to manage the carbon dose correctly in function of the removal rate and to prevent sulphate reduction caused by overdosing.

Using BADES, as intended by Marc Longouet ( MAAO system) when introducing a sulfur denitrator in the nineties, the reactor is NOT kept anoxic after start up and the flow is corrected in function of the nitrate removal rate until a certain level is reached, depending on the volume of the reactor and its ability to consume oxygen. Using this method the flow can be increased reaching about 5x the reactor volume/h and such a reactor will still work having a flow of 10l/h for each liter of sulfur used. ref; MB BADESS CMF De Haes 2017

The different methods used for denitrification purposes using BADES are explained in the reference provided.

 

[J1a]

I am interested in the simulation file.


Using a denitrator ( anoxic reactor), the flow is limited in function of the oxygen content, and can not be managed in function of the nitrate level..
Of coarse we can not ignore the production, it is the most important factor. Because one can not change the flow rate in function of the nitrate removal rate and the same time keep the reactor anoxic using such reactor, the final nitrate level will depend on the daily nitrate production and the level will increase when the production increases. Because the level increases the reactor will remove more nitrate ( autotrophic based). Carbon based also one has to manage the carbon dose correctly in function of the removal rate and to prevent sulphate reduction caused by overdosing.

Using BADES, as intended by Marc Longouet ( MAAO system) when introducing a sulfur denitrator in the nineties, the reactor is NOT kept anoxic after start up and the flow is corrected in function of the nitrate removal rate until a certain level is reached, depending on the volume of the reactor and its ability to consume oxygen. Using this method the flow can be increased reaching about 5x the reactor volume/h and such a reactor will still work having a flow of 10l/h for each liter of sulfur used. ref; MB BADESS CMF De Haes 2017

The different methods used for denitrification purposes using BADES are explained in the reference provided.

I have pm-ed you the file.

 

[Belgian Anthias]

I have pm-ed you the file.

Bedankt.

 

[Belgian Anthias]

The question asked is about the nitrate removal rate, not about the nitrate export rate, which is not the same, certainly not when using a carbon based reactor.
Calculating the removal rate seems not that difficult?

One is going to buy a denitrator. What size it should have? Well, it must be able to remove the daily nitrate production daily at the desired nitrate level with the flow needed to make that possible.

Since the nitrate removal rate is directly dependent on the flow rate but also on the amount of oxygen introduced determining the zone in which denitrification can take place, calculating the removal rate is not as simple as suggested.
When the nitrogen level goes down, in order to remove the same amount of nitrogen, the flow must increase, which means more oxygen is introduced and the denitrification capacity decreases. The available zone for denitrification is directly related to the flow of water, which contains about the same amount of oxygen regardless of the nitrate content.

Using BADES (NOT using an anoxic reactor ) we are able to calculate the volume needed based on the amount of substrate needed to support the biofilm, including the volume needed for the biofilm to consume an increasing amount of oxygen while maintaining the same minimal denitrification rate needed to remove the daily production daily.
To be able to make a simulation one has to know the daily nitrate production and the desired target nitrate level.
Using BADES it is known the reactor must be big enough, at least 1% ( 2% if a mixed substrate is used) of the total system volume. ( good for a daily flow of 2x the total system volume targeting 0 nitrate in the effluent.) Targeting 0 nitrate in the effluent is not needed and not advised.

 

[Belgian Anthias]

An other important parameter using an anoxic ( <0.5ppm DO) denitrator is nitrate availability. If the nitrate level goes down, at the same flow, the nitrate availability decreases. In a heterotrophic denitrator a certain anaerobic remineralisation rate is installed based on nitrate availability. Once the availability of nitrate decreases sulphate will be used in an attempt to maintain the installed remineralistion rate, certainly if organic carbon is dosed.