Deep Sand Bed -- Anatomy & Terminology

[Reefer54]

"T-lak;
"With respect of the prognosis of the 2-7 year tank crash, I installed a plenum with tubes going down to the bottom. After a year or two I'm planning to take a quarterly (monthly?) sample of the anoxic water and do a sniff test. If anything smells, I'll siphon out the water from the bottom (flush out the DSB) without affecting the DT."
Tubes into the plenum would not occur to me as anything but a risk. i looked into plenums with great length in the past, and the idea is awesome, but without proper care, they carry as much risk as a mistreated DSB. Wouldnt you be concerned of the advection possibilities by a tube which is directly connected to the anoxic layer.....i mean, the idea of a plenum is not to mess with that layer. If the plenum was remote and quickly removable, i get it, but if it is integral to your sump or DT....i would feel like i was dancing with flares at a gas station. But you have me curious how that works for you."

ok......tubes. If they were hard lined into the frame or eggcrate or whatever you are going to use to create the plenum and had a length\height that came up out of \through the top of the rest of the layers, and had a water tight seal on them in a considerable amount of places.....it would definitely be viable and work very well. If that is what you are thinking about (or similar).....my apologies and applause. If i am off, please explain. i am super curious now (but it is still way more than i wish to currently undertake and holds too much possibility for the compost pile, especially if i got lax for a month or so).

 

[tmz]

Well, the numbers 14 inches etc for 150% etc, don't fly.imo. Most of the denitrification occurs in the first inch or less. There are studies cited earlier in this monster thread which show that. Defusion and advection are weak forces . Most denitrifying bacteria are facultative; they use O2 ;depelete it and turn to NO3 ,they can do this is very shallow sand ;even in their own mulm. I have a remote deep sand bed because I had it after a failed effort at NO3 reduction with it. It's not any trouble and provides nice habitat for sponges,bacteria and other fuana a sand critters and fits in with the cryptic set up . If I every redo it I'll use a larger footprint and shallower sand.

For NO3 and PO4 control in my heavily fed system I rely on organic carbon dosing and skimming.

 

[tzylak]

" ok......tubes."
Yes, the tubes go continuously from above the tank to the very bottom. I glued them in and even zip-tied the upper section to the walls to eliminate any movement as that would break the anoxic layer. -Anything else would be a disaster waiting to happen. And I feel very confident about its current security and the potential for future sampling to prevent any crashes.

TMZ
"Most of the denitrification occurs in the first inch or less. "
I'd appreciate further elaboration. Please.
IMO the first 1-3 inches is a stagnant layer where the O2 is used and depleted. It is BELOW that layer that the denitrification takes place. -I base this on the pictures from the very first page of this thread.

"If I every redo it I'll use a larger footprint and shallower sand."
-Yes, I agree on that one. That's why I use bottom of a large sump rather than considering the trash can setup.

Tom

 

[tmz]

There is a lot of eleboration throughout the thread ,pages of it, starting on post 74 an through at least post 678 which in on point and only a page or two back.

You are entitled to your opinion; reading salinet sections of teh thread may help.

In brief , most dentirifying bacteria are faculative( use oxygen and when it's used up they take it from nitrate). They engage in aerobic and anaerobic activity.They are also heterotrophic ,requiring organic carbon for energy, They also require other elements like phosphate, potassium ,iron,nitrogen , etc. These are all more available to them in shallower high flow areas than deep beds where their is no significant force to move them down. Without them the bacteria don't grow and don't take up anything. Difussion and advection are not strong enough to move much into a deep bed. Sand critters may channel some if their populations are maintained
The bacteria take up nitrogen and the other elements and can create their own hypoxic areas even in very shallow areas shallow areas in their mulm too. Denitrifcation occcurs at very shallow depths much less than an inch and has been shown in many studies.. In one study , tanks at various depths of sand were tested with no discernible difference in nitrate removal.

 

[tmz]

Good to see this thread still going strong,

Tom, I'm glad to see you still maintaining the thread. Your vast knowledge in the biology of this hobby is greatly appreciated.

Thanks Jimmy. Nice to hear from you.

 

[gregkn73]

There is a lot of eleboration throughout the thread ,pages of it, starting on post 74 an through at least post 678 which in on point and only a page or two back.

You are entitled to your opinion; reading salinet sections of teh thread may help.

In brief , most dentirifying bacteria are faculative( use oxygen and when it's used up they take it from nitrate). They engage in aerobic and anaerobic activity.They are also heterotrophic ,requiring organic carbon for energy, They also require other elements like phosphate, potassium ,iron,nitrogen , etc. These are all more available to them in shallower high flow areas than deep beds where their is no significant force to move them down. Without them the bacteria don't grow and don't take up anything. Difussion and advection are not strong enough to move much into a deep bed. Sand critters may channel some if their populations are maintained
The bacteria take up nitrogen and the other elements and can create their own hypoxic areas even in very shallow areas shallow areas in their mulm too. Denitrifcation occcurs at very shallow depths much less than an inch and has been shown in many studies.. In one study , tanks at various depths of sand were tested with no discernible difference in nitrate removal.

Hi,
after reading all these pages,I try to figure out how to make my 6" rdsb ,perform better.....if I manages to insert a drilled PVC pipe, at the bottom of the 15gallons tank I use as rdsb,and use a small pump drain water from the bottom, the increase flow through the DSB, will it enhance the denitrification by heterotrophic bacteria?