Here are some ref's:
http://www.erdingtonaquatics.com/sandfiltration.html
http://www.wrc.org.za/archives/watersa archive/1999/July/jul99_p357.pdf
Ahh.... Found it...
In a post by Alfinus
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http://reefcentral.com/forums/showthread.php?s=&threadid=595109&perpage=25&pagenumber=37
I have built numerous denitrifiers from coils to sand in the bucket methods of all types. To understand how they work you need to understand the bacteria. Anerobic bacteria do not consume nitrates as a food, but as an oxygen source. These bacteria evolved in a low oxygen envoriment, so through time they devoloped the means to extract oxygen from nitrates and producing the by-product of nitrogen gas. Even tho they need nitrate to lived they also need a food source, some type of carbon fuel. Thats my I always had better results with the bucket method if you could at least have a drip trickle coming out the bottom. I understand about over complicating, but even tho the nitrates will diffuse through the sand over time, organic carbons don't diffuse as easy and need some a little push through the sand. And btw the trickle will not effect anything as the areobic bacteria always are in the top couple inches and as they consume food they will consume all oxygen. Thats also why you need a little trickle because the anerobic will also comsume all the carbon food too, before the anerobic can. I am not saying the simply flow over method will not work, just a way to make it work better.
Even tho I have not tried it yet, vodka dosing at very small amounts over the rdsb should kick it into high gear also, since vodka is a high carbon food source.
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From Pg18 of bigining of thread posted by baryhc:
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http://reefcentral.com/forums/showthread.php?s=&threadid=595109&perpage=25&pagenumber=18
I'm not sure if you are missing anything, but a lot of aquarists are, as evidenced in this thread in just the last page before my original post.
I will try, let's see how it goes.
Firstly, I was in error when I stated that the beginning of "denitrification" was in the Hypoxic or low oxygen zone.
I don't really know where we might say that "the beginning" of the denitrification process takes place. The process itself, however does take place at some depth, primarily in the anoxic zone of the bed.
The first statement should have been: "this is where the processing of Nitrate into other compounds begins. In effect, that is what I meant to be saying, and it is a good thing that we are getting that straightened out.
As I stated before ( originally ) in the "excerpt", this is where a lot of controversy begins.
EDIT: That is because the conversion of Nitrate to other compounds "begins" in the Hypoxic oxygen zone.
Too many aquarists are simply not familiar with this Low Oxygen zone, and this is why weatherman just explained about the fraction of a mm area where this is taking place.
My only intent with the entire original post, was to "clarify the definitions" of Oxygen Gradation Zones. That I did quite flawlessly, however, I stumbled over my shoelaces with the "beginning of denitrification" terminology. ( as well as the Nitrite to Nitrate part )
The terms "Aerobic and Anaerobic" refer to bacterial types and processes, whereas "Oxic and Anoxic" respectively, refer to the zones where these processes occur. These terms are used "in error" an awful lot, by aquarists and experts alike, causing a tremendous amount of confusion. Hypoxic is a rarely used but highly accurate term that correctly refers to "Low Oxygen", and eliminates a lot of confusion.
I hope we have that cleared up now, and that "WE" have correct terminology now available to use when discussing "Oxygenated Zones".
It's too bad that I contributed to the confusion myself to some degree, and I appreciate both yourself and Weatherman keeping me straightened up.
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Posted by Weatherman on Pg:17
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http://reefcentral.com/forums/showthread.php?s=&threadid=595109&perpage=25&pagenumber=17
The standard definitions I'm familiar with are the following:
Aerobic Respiration:
(the conversion of ammonium to nitrite to nitrate in the presense of oxygen)
106(CH2O)16(NH3)(H3PO4) + 106O2 => 106 CO2 + 16 NH3 + PO4
(1a) 16 NH4+ + 24 O2 => 16 NO2- + 16 H2O + 32 H+
(1b) 16 NO2- + 8 O2 = 16 NO3
106(CH2O)16(NH3)(H3PO4) + 138 O2 => 106 CO2 + 16 HNO3 + H3PO4 + 122 H2O
Denitrification:
(conversion of nitrate to nitrogen gas or ammonia in the absense of oxygen)
Nitrate Reduction by Denitrification
106(CH2O)16(NH3)(H3PO4) + 94.4 HNO3 -------106 CO2 + 55.5 N2 + H3PO4 + 177 H2O
Dissimilatory Nitrate Reduction to Ammonia
106(CH2O)16(NH3)(H3PO4) + 84.8 HNO3 -------106 CO2 + 42.4 N2 + 16 NH3 + H3PO4 + 148.4 H2O