vary, but it generally involves converting ammonium to nitrate, and finally to nitrogen gas. One example of this is ammonia-oxidizing bacteria which have a metabolic feature that, in combination with other nitrogen-cycling metabolic activities, such as nitrite oxidation and denitrification, remove nitrogen from wastewater in activated sludge. Since denitrifying bacteria are heterotrophic, an organic carbon source is supplied to the bacteria in an anoxic basin. With no available oxygen, denitrifying bacteria use the oxygen present in the nitrate to oxidize the carbon. This leads to the creation of nitrogen gas from nitrate, which then bubbles up out of the wastewater. See also Nitrifying bacteria Nitrogen Cycle References Bacteria Nitrogen cycle Soil biology Fishkeeping Aquariums