Denitrification
Denitrification is the microbial conversion of nitrates into nitrogen gas, and more broadly the removal of nitrogen compounds from a material. In soils, bacteria working under low-oxygen conditions liberate elementary nitrogen from nitrogenous compounds. Food systems meet it in wastewater plants treating nitrate-rich effluents and in cured meats, where unwanted bacterial action can strip nitrate. In agriculture the same biology returns fertilizer nitrogen to the atmosphere, a loss farmers manage through drainage and careful timing of applications. Monitoring nitrate levels keeps the process beneficial in treatment works and harmless in foods.