Removing ammonia nitrogen from wastewater is a well-established and quantifiable
biological process. Nitrogen exists in the influent primarily in the form of organic nitrogen
and ammonia nitrogen (Total Kejldahl Nitrogen + TKN). The principal part of the organic
nitrogen is mineralized to ammonia nitrogen through bacterial activity. Therefore,
ammonia-N is commonly regarded as the starting point in the nitrogen reduction process.
Nitrification: the conversion of ammonia nitrogen (NH3-N) to nitrate nitrogen (NO3-N) is a
biological process accomplished in the presence of dissolved oxygen. Typical
requirements for effluent ammonia-N are from 1 to 3 mg/l, which is reliably accomplished.
Successful nitrification is accomplished with a healthy microorganism population and an
environment where PH, temperature, alkalinity, organic loading and dissolved oxygen are
In the BioTank system the pH is generally buffered by the carbonate system
associated with the wastewater; the temperature remains consistent due to the biological
activity in the plant; the organic loading is relatively constant because the wastewater has
been treated in the first compartment(s) of the plant; and the compressor provides an
adequate supply of dissolved oxygen.
Facultative heterotrophic organisms under anoxic conditions accomplish biological
denitrification. In this process bacteria convert the nitrate-N to nitrogen gas
that is released into the atmosphere.
Denitrification occurs by several different means and though process control adjustments.
As the microorganisms multiply, the biological film thickens on the submerged media and
the diffused oxygen is consumed before penetrating the full depth of the slime layer.
Consequently the film develops aerobic, anoxic and anaerobic zones. This process accounts for significant nitrogen removal via simultaneous nitrification and denitrification.
Denitrification utilizing septic tank carbon is widely considered to be the most economical
and efficient method for nitrogen removal. Utilizing prescribed recirculation rates this
method of returning BioTank nitrified wastewater to the carbon source in the anoxic zone
of the primary tank has achieved reductions of nitrogen of approximately 80 percent.
Nitrogen removal may be enhanced further in a tertiary anoxic zone located after the