TUESDAY, JAN 17, 2023: NOTE TO FILE
Module 2-6
Nitrification and Denitrification
NITROGEN IN COMBINED MOLECULAR form is one of the principal pollutants present in wastewater; it exists in both organic and inorganic forms. The organic forms of nitrogen include amino acids, urea, uric acids, purines and pyrimidines, while free NH3, ammonium salts and nitrogen gas (nitrogen is not a polluting compound) are the forms of inorganic nitrogen.
While the biological pathways that treat these nitrogen compounds are complex, for simplification we will regard them as just two basic natural processes that take place. entails the biological oxidation of ammonia (NH3) transforming it into nitrite (NO2) with further oxidation producing nitrate (NO3) carried out by nitrifying bacteria. These are processes which take place naturally in the soil as part of the chemical processes of the waste-nutrient cycle and the micro-organisms are therefore essential for life.
Nitrates (NO3) can be readily absorbed by plants through their root systems to make proteins. In wetland wastewater treatments, bacteria living in nodules on plant roots oxidise the NO2 to NO3 which is then absorbed. This is a symbiotic, mutually beneficial relationship between the bacteria and the plants.
The micro-organisms involved in nitrification can be sensitive to the presence of excessive ammonia, temperature, low dissolved oxygen and acidity.
Denitrification is the chemical process by which excess nitrite (NO2) is converted to atmospheric nitrogen (N2) which can be released into the air.
Module 2, lesson 7
