The importance of nitrification and denitrification
The problem of nitrogene compounds and of their biological removal became very important for the effluent treatment, because of the
  • high oxygene consumption of nitrifying bacteria in recipients,
  • fish toxicity of free NH3 and3
  • cancerogenity und toxicity of NO2, an intermediate of the oxidation of NH4 to NO3.
Key factors of efficient and stable nitrification are
  1. SUBSTRATE (MATRIX of the effluent): chemical structure of organics and salinity)
  2. NITRIFYING BIOMASS (activity, stability, settling properties)
  3. INHIBITORS (primarly N- and S-containing heterocyc-les)
  4. TREATMENT PROCESS (prevention of process disturbances)
  5. PROCESS PARAMETERS (N-sludge-loading-rate, pH, temperature)
Characteristic for nitrification are
  • high O2-consumption of 4,6 kgO2/kgTKN
  • neutralization of the produced acidity (HNO3) is required: 2 H+/ Mol TKN-> 2 Mol. NaOH/ TKN
  • low sludge growth: YN ~ 0,04 to 0,08 kg MLSS/kg Noxidized.
  • high sensitivity of the nitrifying microorganisms to inhibitors.


Nitrification of complex effluents may be affected by
properties of nitrifying biomass like:
  • low sludge production
  • weak flocculation
  • slow sedimentation
  • high sensitivity to
  • pH-values: < 6,6
  • low temperatures: < 17°C
  • salinity: >20 g/L
respectively by the presence of
  • inorganic compounds, like heavy metals (copper-salts, etc.)
  • organic compounds, like
    -N-und S-containing heterocycles,
    -S-derivatives of carbamoic-acid (thiocarbamide,thioguanidine, thiurame, etc.)
  • serious, longer inhibition of the nitrification process (duration: several weeks)
  • loss of the nitrifiying biomass,
  • enhanced nitrogene concentrations in the treated effluent
  • slow recovery of the nitrifying capacity of the plant


A reliable PROCESS DESIGN for the nitrification of complex effluents is possible only on basis of continuous, practice relevant biotests, because of the diversity of decisive process parameters.

The reactivation of an inhibited nitrification can be achieved by
  • reduction of the sludge-N-loading rate
  • reduction of the concentration of inhibitors in the reactor(dilution)
  • introduction of new, active nitrifying biomass into the reactor and
  • immobilization of active organisms

Preventive methods for protection of the nitrification process

  • a reliable process design
  • analysis and eventually separate pretreatment of single streams
  • sufficient buffering of hydraulic and loading peaks and
  • high degree of adaptation of nitrifying microorganisms

30 years special experiences in the nitrification of extremely complex effluents the experimental determination of

  • biokinetic data
  • optimal process parameters
  • process design basis
  • inhibitory concentrations of typical chemicals and
  • investigation of new methods for increased process stability
practical experiences with
  • plant startups
  • process disturbances and
  • plant upgrading with
  • extremly problematic effluents

YOUR BENEFITS by cooperating with us:

  • meeting of requirements
  • stable and efficient process
  • optimized technology and process economy
  • good references

Five-step plant for the nitrification/denitrification of ammonia-rich petrochemical effluents

Figure 1. Five-step plant for the nitrification/denitrification of ammonia-rich petrochemical effluents

Dr. Imre Pascik: List of Designed technical scale plants for NITRIFICATION and DENITRIFICATION

Dr. I.Pascik: List of Lab and pilot scale tests, respectively of feasibility studies for biologcal N-removal

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