Reef Chemistry Question of the Day #54 Denitrification

[Randy Holmes-Farley]

Reef Chemistry Question of the Day #54

People often talk about denitrification and the conversion of nitrate into N₂ in deep sand beds or in pores of live rock.

Besides nitrate, seawater and bacteria, something else is needed for that process to take place. What is it?

A. Carbon dioxide
B. Ammonia
C. Organics
D. Calcium carbonate
E. Bicarbonate
F. Larger organisms (such as worms)

 

[s.h.moradi]

I think the answer is A

 

[Nano sapiens]

C. An organic source of carbon, such as methanol, ethanol, etc, is required for dissimilatory nitrate reduction.

 

[lyang415]

Does the denitrifying only occur in anaerobic zones of live sand and live rock? Or does the process occur throughout the media? Please explain the chemistrybwhind this!

 

[Randy Holmes-Farley]

Does the denitrifying only occur in anaerobic zones of live sand and live rock? Or does the process occur throughout the media? Please explain the chemistrybwhind this!

Certainly. When I give the answer, I will explain it.

 

[leptang]

A. in anaerobic zones

 

[H2O]

I'm going with B ammonia can be used to boost the cycle new tank

 

[DFW]

A!!

 

[H2O]

Come on r2r don't be shy post your answers everyone's looking like their keyboards got stuck

 

[DRThompson]

C: organics. This bacteria is what you are growing when you carbon dose (vodka,vinegar,sugar,VitC, methanol...etc)

 

[CastAway]

Going to guess C, based on something I remember reading by alberthiel way back, on doesing sugar to a sponge for denitrification

 

[Heatherrom]

Organic material either dissolved or particulate is needed. The carbon source feeds the bacteria and the NO3- is its electron acceptor.

 

[ksanfranfan]

My guess,
C. Organics

 

[beaslbob]

I think organics also.

 

[Cory]

I think it's bicarbonate. I don't think they need organics when their food is already there no3.

 

[Randy Holmes-Farley]

Anyone else before I give the answer?

 

[Higher Thinking]

B. Ammonia. Final answer.

 

[Nevil]

I think the answer is A

 

[Randy Holmes-Farley]

And the answer is...C. Organics (although B would also get credit for the ammonox process, see below)

In normal aerated seawater, bacteria consume organics using O2 as the electron acceptor (just as people do)

organics + O2 --> CO2 + H2O + energy

In low oxygen regions, bacteria run out of the most efficient thing to use (which is O2), so species thrive which can use other things to metabolize organics, such as nitrate:

Organics + nitrate --> CO2 + N2 + H2O + energy

If you are not dosing organic carbon, this process is taking place with natural organics found in the aquarium (proteins, lipids, carbohydrates, etc).

If you are adding things like vodka, vinegar, sugar, or the commercial preparations of these sorts of organics, then you are accelerating this natural process by providing more organics as the "food".

The above is "normal" denitrification.

Another process that happens in some circumstances is the ammonox process where ammonia is used and organics are not.
The basic process involves ammonia and nitrite and results in N2 and some nitrate.

For more on this process, see:

http://en.wikipedia.org/wiki/Anammox

 

[DFW]

"organics + O2 --> CO2 + H2O + energy"


Doesn't this mean that A is also right?:smile: