Denitrification

Since denitrification can remove NO3−, reducing its leaching to groundwater, it can be strategically used to treat sewage or animal residues of high nitrogen content.

Other genes known in microorganisms which denitrify include nir (nitrite reductase) and nos (nitrous oxide reductase) among others;[3] organisms identified as having these genes include Alcaligenes faecalis, Alcaligenes xylosoxidans, many in the genus Pseudomonas, Bradyrhizobium japonicum, and Blastobacter denitrificans.

Examples of anoxic environments can include soils,[11] groundwater,[12] wetlands, oil reservoirs,[13] poorly ventilated corners of the ocean and seafloor sediments.

High activity of denitrifiers can be observed in the intertidal zones, where the tidal cycles cause fluctuations of oxygen concentration in sandy coastal sediments.

[14] For example, the bacterial species Paracoccus denitrificans engages in denitrification under both oxic and anoxic conditions simultaneously.

Upon oxygen exposure, the bacteria is able to utilize nitrous oxide reductase, an enzyme that catalyzes the last step of denitrification.

Enzymes NapAB, NirS, NirK and NosZ are located in the periplasm, a wide space bordered by the cytoplasmic and the outer membrane in Gram-negative bacteria.

[17] Organic carbon as an electron donor is a common limiting nutrient for denitrification as observed in benthic sediments and wetlands.

It is also an instrumental process in constructed wetlands[28] and riparian zones[29] for the prevention of groundwater pollution with nitrate resulting from excessive agricultural or residential fertilizer usage.

[32] Reduction under anoxic conditions can also occur through process called anaerobic ammonium oxidation (anammox):[33] In some wastewater treatment plants, compounds such as methanol, ethanol, acetate, glycerin, or proprietary products are added to the wastewater to provide a carbon and electron source for denitrifying bacteria.

[40] Electrochemical methods can often avoid requiring costly chemical additives, but their effectiveness can be constrained by the pH and ions present.