Denitrification riddle

Hi,

I understand (I believe) how DSB and plenums work. By creating an anoxic
zone where bacteria are forced to pull oxygen out of the nitrate molecule,
leaving inert nitrogen behind.

What baffles me is if the oxygen cant get the anoxic zone, how in blazes
does the water and nitrate get there in order to be denitrified? Or is it
that the anoxic zone incubates this sort of bacteria, which then finds its
way into the water column, but still goes for the nitrate rather than
oxygen as thats all it knows?

Inquiring minds want to know.

-Phil

Phil,

What happens is the bacteria in the top of the sand bed use up the
oxygen as the water moves down into the sand bed leaving very little
oxygen in the water. While the nitrate is actually created in these same
top levels of the sand making it very easy to flow into the lower areas
that are low in oxygen.

Kim
http://www.jensalt.com




Hi,

I understand (I believe) how DSB and plenums work. By creating an anoxic
zone where bacteria are forced to pull oxygen out of the nitrate molecule,
leaving inert nitrogen behind.

What baffles me is if the oxygen cant get the anoxic zone, how in blazes
does the water and nitrate get there in order to be denitrified? Or is it
that the anoxic zone incubates this sort of bacteria, which then finds its
way into the water column, but still goes for the nitrate rather than
oxygen as thats all it knows?

Inquiring minds want to know.

-Phil

I would try to explain this with a dynamic nature of this anoxic layer.
Deep sand beds are alive. They contain micro worms, micro stars, snails.
They constantly travel through the sand mixing it a little bit all the time.
This will help with water exchange and the transport of energy/food
between layers of sand. This is an atempt of explanation, but it does
not explain plenums - which are "dead" and separated from upper layers.

"Phil" wrote in message ...
Hi,

I understand (I believe) how DSB and plenums work. By creating an anoxic
zone where bacteria are forced to pull oxygen out of the nitrate molecule,
leaving inert nitrogen behind.

What baffles me is if the oxygen cant get the anoxic zone, how in blazes
does the water and nitrate get there in order to be denitrified? Or is it
that the anoxic zone incubates this sort of bacteria, which then finds its
way into the water column, but still goes for the nitrate rather than
oxygen as thats all it knows?

Inquiring minds want to know.

-Phil

The bottom layer of a DSB are not alive, they are anoxic and where facultative
denitrification take place, where NO3 is converted to N2 gas, by facultative denitrifying
bacteria. If they were alive, being mixed by microfauna or meiofauna, the water would
carry in O2, which would inhibit denitrification. It is the upper layers that are alive,
the bottom is dead just like a plenum. Microfauna can not be supported in these lower
layer as there is not enough O2 for them to survive

--
Boomer

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"Pszemol" wrote in message ...
: I would try to explain this with a dynamic nature of this anoxic layer.
: Deep sand beds are alive. They contain micro worms, micro stars, snails.
: They constantly travel through the sand mixing it a little bit all the time.
: This will help with water exchange and the transport of energy/food
: between layers of sand. This is an atempt of explanation, but it does
: not explain plenums - which are "dead" and separated from upper layers.
:
: "Phil" wrote in message
...
: Hi,
:
: I understand (I believe) how DSB and plenums work. By creating an anoxic
: zone where bacteria are forced to pull oxygen out of the nitrate molecule,
: leaving inert nitrogen behind.
:
: What baffles me is if the oxygen cant get the anoxic zone, how in blazes
: does the water and nitrate get there in order to be denitrified? Or is it
: that the anoxic zone incubates this sort of bacteria, which then finds its
: way into the water column, but still goes for the nitrate rather than
: oxygen as thats all it knows?
:
: Inquiring minds want to know.
:
: -Phil

I understand (I believe) how DSB and plenums work. By creating an anoxic
zone where bacteria are forced to pull oxygen out of the nitrate molecule,
leaving inert nitrogen behind.

Plenum and DSB actually works in very different ways. The ideal behind the
water layer for plenum is to double the O2 zone by doubling the surface, but
in turn limits the available O2-lacking zone. DSB however, pushes for plenty
of O2-lacking zone, hence the depth.

What baffles me is if the oxygen cant get the anoxic zone, how in blazes
does the water and nitrate get there in order to be denitrified? Or is it
that the anoxic zone incubates this sort of bacteria, which then finds its
way into the water column, but still goes for the nitrate rather than
oxygen as thats all it knows?

This post by Rob may help ...
http://www.escribe.com/pets/reefkeepers/m13461.html

jc

"Boomer" wrote in message ...
Lets answer a question with a question. You are aware that LR also
brings about facultative dentrification and converts NO3 --- N2 (g).

Are there any worms or snails in the very fine pores of the LR......Nope

Interesting comparison... I do not know how LR works in this task.
But, in contrary, I see some worms drilling holes in my LR...

Think convection and diffusion

What stops convection/diffusion of oxygen into anoxic layers?

we want the process to continue, its slow, very slow and with its slow
speed the low
oxygen water and nitrogen is moved out, and other oxygen rich water is
slowly moved in.
allowing bacteria to process the oxygen rich water, then the oxygen poor
water, first
converting ammonia to nitrite removing some oxygen, then nitrite to
ammonia removing more
oxygen, then finally the anoxic zone where nitrate is converted and the
low oxygen water
is moved out, nitrogen is moved out, and the process repeates.

Now please explain just *how* all these "events" take place ... ;p

jc

"Richard Reynolds" wrote in message news:MhR6b.47296$Qy4.13076@fed1read05...
nothing stoped it

if it did then you would be in trouble

we want the process to continue, its slow, very slow and with its slow speed the low
oxygen water and nitrogen is moved out, and other oxygen rich water is slowly moved in.
allowing bacteria to process the oxygen rich water, then the oxygen poor water, first
converting ammonia to nitrite removing some oxygen, then nitrite to ammonia removing more
oxygen, then finally the anoxic zone where nitrate is converted and the low oxygen water
is moved out, nitrogen is moved out, and the process repeates.

ok, assuming it happens like you said, and that below a couple of centimeters
there is no oxygen - do we care how deep the anoxic layer is? In other words:
Why deep sand beds are so deep? Is there any role to play for the most bottom
layer of the sand, like 4-5 inches below the sand surface? I would expect it
to be completely dead and inactive if we eliminate the work of burrowing worms
and other critters breathing with oxygen but making short trips there "for food".

"Jimmy Chen" wrote in message ...
I understand (I believe) how DSB and plenums work. By creating an anoxic
zone where bacteria are forced to pull oxygen out of the nitrate molecule,
leaving inert nitrogen behind.

Plenum and DSB actually works in very different ways. The ideal behind the
water layer for plenum is to double the O2 zone by doubling the surface, but
in turn limits the available O2-lacking zone. DSB however, pushes for plenty
of O2-lacking zone, hence the depth.

Could you please explain this "double the 02 zone" little better?
I do not get it...

What baffles me is if the oxygen cant get the anoxic zone, how in blazes
does the water and nitrate get there in order to be denitrified? Or is it
that the anoxic zone incubates this sort of bacteria, which then finds its
way into the water column, but still goes for the nitrate rather than
oxygen as thats all it knows?

This post by Rob may help ...
http://www.escribe.com/pets/reefkeepers/m13461.html

Interesting:
"There is a basic misconception that the lack of measurable oxygen
means that there are no infauna present. That is simply not true. In
detailed studies of the relative meiofaunal density with depth and oxygen
concentration show that fauna are typically found well below the depth of 0
oxygen concentration, although the relative abundance falls quickly after
the oxygen concentration becomes low."

And wow! In the next part he is saying about what I have imagined:

"Since very few animals can live in anoxic sand, burrows to the bottom of the
substrate are prima facie evidence that we don't have an anoxic layer in the
lower portion of the sand.

That is simply not true -- many organisms are incapable of living in the
anoxic layer but make extensive use of the nutrients being regenerated in
those zones. Some species (e.g., Arenicola) gain almost all of their
nutritional requirements by ingestion sulfide-rich sediments from anoxic
zones and subsequently expel the reduced deep sediments onto the surface
around their burrow in the form of fecal castings. These worms make short
trips into the inhospitable reduced layers to feed and then return to oxic
zones for respiration and digestion of the bio-organic layers on the
reduced sediments. "

Who is Rob Toonen ? I should be probably ashamed now knowing who is he... :-)
He definitely sounds like some good college professor :-)

ok, assuming it happens like you said, and that below a couple of centimeters
there is no oxygen - do we care how deep the anoxic layer is? In other words:
Why deep sand beds are so deep? Is there any role to play for the most bottom
layer of the sand, like 4-5 inches below the sand surface? I would expect it
to be completely dead and inactive if we eliminate the work of burrowing worms
and other critters breathing with oxygen but making short trips there "for food".

my news server brain farted and i have 500 un read messages in this group and there all
duplicates of another message, stupid admins, ooh well better late then never

first off I never stated to how much space was required to get to the anoxic layer, second
a copule of centimeters are IMO capiable of creating an anoxic zone, (I can see what
apears like it in my FO which doesnt have a DSB, its not stable and only in a corner left
alone by sand sifting fish ) but its not reliable, a worm goes thru it / a rock falls /
a fish disturbs it and its no longer there the depth does a few things, it makes it
bigger, it makes it more stable, and it helps in the transfer of tank water to the anoxic
zone.


check out some of Dr Ron's stuff http://www.rshimek.com/reef/sediment.htm


there is another dr dude who is doing local research I have to find his stuff online again
so i can post it to these threads


--
Richard Reynolds