1. Nitrogen Main species Organic nitrogen
NH4+: Ionized ammonia, nutrient to algae
NH3: Free (unionized) ammonia, toxic to fish
NO2-: Intermediate byproduct of nitirification, < 1 mg/L, causes the hemoglobin in the blood to change to methemoglobin, cause methemoglobinemia (‘blue baby’ syndrome)
NO3-: Final product of nitrification, undeveloped digestive tracts of an infant possess bacteria that convert nitrate into nitrite, < 10 mg/L

2. Free Ammonia (Unionized, NH3) and Ionized (NH4+) Ammonia
More
toxic
pH effect
Toxic to
fish
Temperature effect
More
toxic
Ammonia not regulated in winter

3. Nitrogen Transformation in Biological Treatment Processes
Organic nitrogen
(proteins, urea, etc.)
Bacterial decomposition
and hydrolysis
Ammonia nitrogen
(NH3-N)
Assimilation
Organic nitrogen
(bacterial cells)
Organic nitrogen
(net growth)
Nitrification
Nitrite (NO2-)
Lysis and autooxidation O2
Nitrate (NO3-) O2
Denitrification
Nitrogen gas (N2)
Organic carbon
(substrate)

4. Subdivision of Total Influent TKN
(Nti) N H 3
& 4 -
(Nai)
100%
Organically
bound N (Nti - Nai)
~75%
Unbiodegrad.
soluble N
(Nui)
Unbiodegrad.
Particulate N
(Npi)
~25%
Biodegrad. N
(Nai)
~3%
~10%
~12%
Total Kjeldahl Nitrogen (TKN): sum of organic nitrogen, ammonia
(NH3), and ammonium (NH4+) in biological wastewater treatment

5. Nitrogen Transformation in Biological Treatment Processes
Organic nitrogen
(proteins, urea, etc.)
Bacterial decomposition
and hydrolysis
Ammonia nitrogen
(NH3-N)
Assimilation
Organic nitrogen
(bacterial cells)
Organic nitrogen
(net growth)
Nitrification
Nitrite (NO2-)
Lysis and autooxidation O2
Nitrate (NO3-) O2
Denitrification
Nitrogen gas (N2)
Organic carbon
(substrate)

6. Nitrification: Chemoautotrophs (1)
Nitrification: Conversion from ammonia to NO2- / NO3-
NH O NO2- + H2O + 2H+ + New biomass
Nitrosomonas
NO O NO3- + New biomass
Nitrobactor
Oxygen demand
Total oxygen demand for nitrification: 4.57 g O/g N