At the biochemical level the nitrification process is more complex than simply the sequential oxidation by Nitrosomonas of ammonia into nitrite, and the subsequent oxidation by Nitrobacter, of nitrite to nitrate. Various reaction intermediates and enzymes are involved in this processes. In soils, streams and treatment plants, conditions permitting the oxidation of ammonia and nitrite can be created by a variety of micro-organisms. Table 3.2 show some of the factors influencing the nitrification.
Table 3.1 Some characteristics of nitrifying bacteria and biological nitrification.
Cell shape Cell size Motile Gram test Cell weight
Estimated generation time hours
Dissolved oxygen requirements to nitrify
Maximum growth rate at 20 °C
Nitrogen oxidation rate mg N/g VSS at 20 °C
Yield constant mg vss/mg N
Long-term temperature constant susp. culture, °C"1 0,05
Long-term temperature constant att. culture, °C"1
Temperature range for process °C
Reaction Kinetics used in literature
Saturation constant, mg N/liter
Saturation constant, mg 02/liter
Ovoid to rod-shaped 1 x 1,5|im may or may not be negative
Monod, zero order first order
Ovoid to rod-shaped 0,5 x1,0nm may or may not be negative
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