DNRA in the reefaquarium!?

Belgian Anthias · 11/05/2018, 02:57 PM

Reefers try to keep there nitrates at a low to very low level. Nitrate reduction is performed by assimilation and denitrification including DNRA, the nitrate reduction process back to ammonia. Normally about 15 % of total denitrification will be DNRA.
The DNRA share in the total denitrification can easily be influenced, increased.
What is best, lower the nitrate level by removing the nitrogen by denitrification to nitrogen gas or keeping the nitrogen in the system by DNRA?

reefgeezer · 11/05/2018, 03:40 PM

I'm afraid my initial answer is so obvious and that I'm probably missing something but... Ammonium is much more toxic in the marine environment. I can't think of a reason to want to increase it on purpose. I'm probably wrong though. I'd be interested in being educated.

bertoni · 11/05/2018, 03:55 PM

DNRA probably won't produce enough ammonia to become a toxicity issue. It might keep more fixed nitrogen in the tank, but feeding is such an easy way to add nitrate that I'm not sure that a bit of DNRA is all that useful on average.

Belgian Anthias · 11/06/2018, 05:42 AM

Quote:

Originally Posted by bertoni

DNRA probably won't produce enough ammonia to become a toxicity issue. It might keep more fixed nitrogen in the tank, but feeding is such an easy way to add nitrate that I'm not sure that a bit of DNRA is all that useful on average.

It may, depending of the max carrying capacity of the system.
DNRA limits the export of nitrogen by denitrification as they compete for the same in a very limited environment.. When DNRA increases, the export of nitrate by nitrogen gas is decreased, and depending of the situation this may end up to be a lot instead of a bit. It think the issue is important enough to be taken in account when choices have to be made about nitrogen management. As an example: A system in which 1 ppm nitrate is reduced daily by denitrification + DNRA , +- 0, 15 ppm is normally reduced by DNRA, the rest is removed as nitrogen gas. If denitrification shifts to DNRA this can cause too high a load for the existing carrying capacity. That it happens is very unlikely, it is only a theoretical example showing DNRA may not be overlooked when making decisions concerning nitrogen management..

pisanoal · 11/06/2018, 06:10 AM

AOk... So what parameters would we be looking at changing to facilitate one over the other? And just because it's possible to imagine this process becoming prevalent does not mean it is plausible in the laws of nature or even possible in our circumstances for that matter.

I'd be interested in the mechanisms that promote one over the other.

Tripod1404 · 11/06/2018, 04:44 PM

On issue I have with this is that DNRA is an anaerobic process and anaerobic organisms have very slow metabolisms due to being energy limited. So it would be difficult to have meaningful levels of this process without a large sum of anaerobic bacteria. This requires something like a large deep sand bed reactor.

Same is also partially true for denitrification to nitrogen gas. It also is mainly a anaerobic process. For a long time it was thought it would never occur in the presence of O2 as there is no energetic advantage of using nitrate as an oxidant when oxygen is present. However, today we know that it does occur in the presence of O2, but it is not clear why it happens as it lowers the overall yield. The main hypothesis is that in nature it happens in environments where oxygen levels fluctuate and used as a mechanisms to prevent metabolic staling when O2 levels drop.

In my opinion, both process have negligible impact on eliminating nitrogenous waste in regular tanks that do not have specialized equipment to maximize the effectiveness of these processes.

Uncle99 · 11/06/2018, 08:17 PM

So after reading these posts, it reminds me of just how much I have learned, and how much I have to go.....that appears to be a long, long way......

Tripod1404 · 11/06/2018, 09:15 PM

Quote:

Originally Posted by Tripod1404

On issue I have with this is that DNRA is an anaerobic process and anaerobic organisms have very slow metabolisms due to being energy limited. So it would be difficult to have meaningful levels of this process without a large sum of anaerobic bacteria. This requires something like a large deep sand bed reactor.

Same is also partially true for denitrification to nitrogen gas. It also is mainly a anaerobic process. For a long time it was thought it would never occur in the presence of O2 as there is no energetic advantage of using nitrate as an oxidant when oxygen is present. However, today we know that it does occur in the presence of O2, but it is not clear why it happens as it lowers the overall yield. The main hypothesis is that in nature it happens in environments where oxygen levels fluctuate and used as a mechanisms to prevent metabolic stalling when O2 levels drop. So a basal level of aerobic denitrification pathway is kept functional in case the bacteria quickly needs to switch over to that, in response to doping oxygen.

In my opinion, both process have negligible impact on eliminating nitrogenous waste in regular tanks that do not have specialized equipment to maximize the effectiveness of these processes.

bertoni · 11/06/2018, 09:21 PM

I am unclear on why DNRA suddenly should rise in an aquarium, especially to the point of poisoning animals.

Belgian Anthias · 11/07/2018, 03:27 AM

In a normal nitrifying bio-filter with chalk as a base for the growing biofilm about 15% of the produced nitrate is reduced by denitrification. About 85% of NH4-N reduced will leave the filter as nitrate, the rest, about 15%, as nitrogen gas and of coarse all what may be in between. ( The part nitrogen gas can be increased to 90% just by adding Sulphur grains as substrate for the growing nitrifying biofilm ref: http://www.baharini.eu/baharini/doku...bades-kolommen ).
A small part of produced NO3-N will be used for DNRA. When the C:N ratio increases denitrification will shift to DNRA and increase the minimum carrying capacity as more NH4-N must be cycled. Although the energy yield of DNRA is lower as can be withdrawn from denitrification their growth is twice as high at an increased C:N ratio. (ref: http://www.baharini.eu/baharini/doku...io-chemie:dnra )
About DNRA in a denitrifiying biofilm is part of other research, also the total effect on the carrying capacity.
Anyway, any increase of DNRA will lower the max bio-load, a high C:N ratio is best avoided.
As most reefers do not make use of bio-filters the carrying capacity can not easily be adjusted and the max bio-load of the system is unknown. Changing , increasing the minimum carrying capacity does always include some risk.
On the other hand, a high C:N ratio will support growth and fast ammonia assimilation as long all building materials are available, but reduce the installed nitrification capacity, all part of the total carrying capacity.

Belgian Anthias · 11/07/2018, 04:33 AM

A lot of heterotrophs are able to conduct nitrification or denitrification in aerobic conditions. A lot can do both simultaneously. As denitrification is inhibited by the presences of oxygen they use up the oxygen internally able reducing nitrate if more oxygen is needed. A lot of them can not live in a marine aquarium.

In a normal nitrifying biofilm denitrification takes place. +- 40 % of the population has an anaerobic pathway.

In a nitrifying biofilter a lot of processes may take place including anaerobic processes as denitrification both autotrophic and heterotrophic, DNRN, DNRA, ANAMMOX. The autotrophic reduction of nitrate is an important process in a nitrifying biofilm as it is responsible for the removal of constantly produced HS.

A high DNRA activity may slow down or inhibit most other processes needing nitrate.

11/05/2018, 02:57 PM	#1
Belgian Anthias Registered Member Join Date: Oct 2009 Location: Belgium Posts: 608	DNRA in the reefaquarium!? Reefers try to keep there nitrates at a low to very low level. Nitrate reduction is performed by assimilation and denitrification including DNRA, the nitrate reduction process back to ammonia. Normally about 15 % of total denitrification will be DNRA. The DNRA share in the total denitrification can easily be influenced, increased. What is best, lower the nitrate level by removing the nitrogen by denitrification to nitrogen gas or keeping the nitrogen in the system by DNRA?

11/05/2018, 03:40 PM	#2
reefgeezer Registered Member Join Date: Dec 2009 Location: Wichita KS Posts: 2,621	I'm afraid my initial answer is so obvious and that I'm probably missing something but... Ammonium is much more toxic in the marine environment. I can't think of a reason to want to increase it on purpose. I'm probably wrong though. I'd be interested in being educated. __________________ John, Current Tank Info: In-process, 90 Gallon SPS Reef

11/05/2018, 03:55 PM	#3
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	DNRA probably won't produce enough ammonia to become a toxicity issue. It might keep more fixed nitrogen in the tank, but feeding is such an easy way to add nitrate that I'm not sure that a bit of DNRA is all that useful on average. __________________ Jonathan Bertoni

11/06/2018, 09:21 PM	#9
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	I am unclear on why DNRA suddenly should rise in an aquarium, especially to the point of poisoning animals. __________________ Jonathan Bertoni

11/07/2018, 03:27 AM	#10
Belgian Anthias Registered Member Join Date: Oct 2009 Location: Belgium Posts: 608	In a normal nitrifying bio-filter with chalk as a base for the growing biofilm about 15% of the produced nitrate is reduced by denitrification. About 85% of NH4-N reduced will leave the filter as nitrate, the rest, about 15%, as nitrogen gas and of coarse all what may be in between. ( The part nitrogen gas can be increased to 90% just by adding Sulphur grains as substrate for the growing nitrifying biofilm ref: http://www.baharini.eu/baharini/doku...bades-kolommen ). A small part of produced NO3-N will be used for DNRA. When the C:N ratio increases denitrification will shift to DNRA and increase the minimum carrying capacity as more NH4-N must be cycled. Although the energy yield of DNRA is lower as can be withdrawn from denitrification their growth is twice as high at an increased C:N ratio. (ref: http://www.baharini.eu/baharini/doku...io-chemie:dnra ) About DNRA in a denitrifiying biofilm is part of other research, also the total effect on the carrying capacity. Anyway, any increase of DNRA will lower the max bio-load, a high C:N ratio is best avoided. As most reefers do not make use of bio-filters the carrying capacity can not easily be adjusted and the max bio-load of the system is unknown. Changing , increasing the minimum carrying capacity does always include some risk. On the other hand, a high C:N ratio will support growth and fast ammonia assimilation as long all building materials are available, but reduce the installed nitrification capacity, all part of the total carrying capacity. Last edited by Belgian Anthias; 11/07/2018 at 03:37 AM.

11/06/2018, 06:10 AM	#5
pisanoal Registered Member Join Date: Sep 2014 Posts: 705	AOk... So what parameters would we be looking at changing to facilitate one over the other? And just because it's possible to imagine this process becoming prevalent does not mean it is plausible in the laws of nature or even possible in our circumstances for that matter. I'd be interested in the mechanisms that promote one over the other.

11/06/2018, 04:44 PM	#6
Tripod1404 Registered Member Join Date: Mar 2016 Posts: 1,821	On issue I have with this is that DNRA is an anaerobic process and anaerobic organisms have very slow metabolisms due to being energy limited. So it would be difficult to have meaningful levels of this process without a large sum of anaerobic bacteria. This requires something like a large deep sand bed reactor. Same is also partially true for denitrification to nitrogen gas. It also is mainly a anaerobic process. For a long time it was thought it would never occur in the presence of O2 as there is no energetic advantage of using nitrate as an oxidant when oxygen is present. However, today we know that it does occur in the presence of O2, but it is not clear why it happens as it lowers the overall yield. The main hypothesis is that in nature it happens in environments where oxygen levels fluctuate and used as a mechanisms to prevent metabolic staling when O2 levels drop. In my opinion, both process have negligible impact on eliminating nitrogenous waste in regular tanks that do not have specialized equipment to maximize the effectiveness of these processes.

11/06/2018, 08:17 PM	#7
Uncle99 Crab Free Zone Join Date: Sep 2017 Location: Ontario, Canada Posts: 2,906	So after reading these posts, it reminds me of just how much I have learned, and how much I have to go.....that appears to be a long, long way......

11/07/2018, 04:33 AM	#11
Belgian Anthias Registered Member Join Date: Oct 2009 Location: Belgium Posts: 608	A lot of heterotrophs are able to conduct nitrification or denitrification in aerobic conditions. A lot can do both simultaneously. As denitrification is inhibited by the presences of oxygen they use up the oxygen internally able reducing nitrate if more oxygen is needed. A lot of them can not live in a marine aquarium. In a normal nitrifying biofilm denitrification takes place. +- 40 % of the population has an anaerobic pathway. In a nitrifying biofilter a lot of processes may take place including anaerobic processes as denitrification both autotrophic and heterotrophic, DNRN, DNRA, ANAMMOX. The autotrophic reduction of nitrate is an important process in a nitrifying biofilm as it is responsible for the removal of constantly produced HS. A high DNRA activity may slow down or inhibit most other processes needing nitrate.