A slow adaptation period, with a lower than expected rate follows such changes. See figure for a graph of rate change with rapid changes in temperature. Click here to see a graph of growth rates with temperature. Nitrifying bacteria are especially sensitive to low oxygen concentrations, and providing enough oxygen in waste water treatment plants is often the most important design consideration. The exact mechanisms by which pH effects the reaction rates are not fully understood, although it is believed that inhibitions, particularly from the neutral NH3 and HNO2 species, become important.
Metals are particularly strong inhibitors of the reactions.
When exposed to more than one inhibitor, the extent of inhibition increases greatly.