Removal of ammonia is a primary aim of wastewater treatment processes. The chemistry and biology of the process is well understood. In summary, it involves a nitrification step in which ammonia is firstly converted to nitrite and then nitrate followed by a denitrification step involving the reduction of nitrate to nitrogen gas. An overview of the nitrogen cycle is depicted in figure 1 below. Nitrite and nitrate are key actors within this cycle and nitrite has a role to play when considering nitrous oxide (N2O) emissions.