Ничего, что на английском?
ESTABLISHING AN ANOXIC ENVIRONMENT
In the denitrification process, an anoxic zone is created by using an unaerated tank where the dissolved oxygen levels are kept below 1 mg/l and as close to, without reaching 0 mg/ as possible. A target operating point would be between 0.2 to 0.5 mg/l.
The concentration of mixed liquid and suspended solids must also be kept in balance. The pH of the anoxic zone should be close to neutral (7.0) and never drop below 6.5.
There must also be a carbon source. Typically 2.72 mg BOD5 are required per mg of NO3-N removed.
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During denitrification, the tank is agitated but not aerated, thereby starving the bacteria of readily available oxygen. This forces the bacteria to break down the nitrate in the activated sludge to use as their primary oxygen source.
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When optimizing a mixer design for an anoxic tank, the main considerations are:
- Creating a strong axial flow that engages the entire tank
- Suspending solids, including waste sludge
- Eliminating oxygen from the liquid surface by controlling swirl and vortex
- Promoting bacterial breakdown of nitrate so the nitrogen gas can escape
Impeller design is the most important factor since it determines the directional flow and level of pumping within the tank.
Fibrous material, which was not eliminated by screening or grinders in the front end of the treatment plant, may create build-up on a hydrofoil impeller. Accumulation of materials on an impeller can compromise the axial direction, making it more like a radial flow. This increases the likelihood of introducing a swirl or vortex on the surface of the effluent. The result is an incorporation of unwanted oxygen into the tank. An anti-ragging impeller should be used to maintain optimal mixer performance and a strong axial flow.
Это да... не аквариумная, немного, статья... но все равно по теме. Источник http://www.dynamixin...denitrification
Зато тут самое важное, как мне кажется:
dissolved oxygen levels are kept below 1 mg/l and as close to, without reaching 0 mg/ as possible
То есть то, о чем я и говорю, полностью анаэробные условия - это фейл, метан и сероводород.