Nitrification All or Nothing
When the AOB population is under stress, due to reduced dissolved oxygen concentration, low or high temperature, inhibition or other factors, the growth rate declines.
Because the kinetic constant for ammonia is so low (about one mg N/L) it is difficult to detect when the AOB population is declining.
For example, when there are no other constraints: by the time ammonia concentrations have changed from 0.2 to 2 mg N/L, the AOB population has declined by about 90%, and you are on the threshold of nitrification failure.
Two step reaction – no known MO converts ammonia
AOB--ammonia to nitrite
NOB--nitrite to nitrate
ammonia per hour.
Low net yield is due to low energy yield, and the need to
use CO2 as the carbon than organic chemicals.
Ammonia Oxidizing Bacteria (AOB)
Nitrosococcus Nitrosospira Nitroslobus Nitrosovibrio
Convert ammonia to hydroxylamine, then nitrite
Key enzyme Ammonia Monooxygenase (AMO)
Substrate is Free Ammonia, NH3 (FA)
Product is Free Nitrous Acid (FNA)